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thesn10 dd5ec25ff9 rename canocial amount to price

2026-05-25 21:55:02 +02:00

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Solisting Implementation Plan

For agentic workers: REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (- [ ]) syntax for tracking.

⚠️ Reference plan — do not implement yet. Two prerequisites must be completed first:

2026-05-19-descro-buyer-flow.md — adds buyer_create_escrow, seller_confirm, and symmetric cancel to descro

AcceptancePolicy prerequisite (adding AcceptancePolicy enum to descro_ext_resolvers) — documented in the old plan's prerequisite section

Goal: Build the solisting Anchor program — a coordination and discovery layer for product listings and bilateral order consent, orchestrating the full flow from buyer intent → bilateral consent → active descro escrow without ever touching the descro vault directly.

Architecture:

ListingAccount holds a single canonical price (canonical_currency + price) as the sole source of truth. Alternative currencies (alt_currencies: Vec<AltCurrencyConfig>) are always converted from canonical at create_order time via on-chain Pyth oracles — no independent price per currency, no arbitrage possible.
Each AltCurrencyConfig carries its own usd_oracle: Option<Pubkey> (the Pyth TOKEN/USD feed for that token; None = treat as a $1 USD stablecoin). The canonical currency has a parallel canonical_oracle: Option<Pubkey>. Currency::Spl stores decimals: u8 so the program never needs to look up the mint.
OrderAccount records the bilateral consent: which currency the buyer chose, the oracle-computed amount, and a pointer to the descro escrow.
The oracle module converts between any two currencies through USD as an intermediate (using up to two Pyth feeds): canonical_usd = amount × canonical_price, target_amount = canonical_usd ÷ target_price. Both sides can independently be a stablecoin (None oracle = $1 peg, no account needed).
accepted_resolvers is a global list per listing — resolvers handle disputes, not payments, so one list covers all currencies.
create_order CPIs descro.buyer_create_escrow atomically. accept_order CPIs descro.seller_confirm. Solisting never holds or transfers vault funds.
State drift (buyer cancels directly on descro) is handled gracefully: terminal instructions read descro state first and skip the CPI if the escrow is already resolved.

Key design decisions:

No OrderVault — funds live in descro's vault from the moment create_order is called
AcceptancePolicy is enforced by descro in seller_confirm, not by solisting
quantity_reserved tracks pending orders; decremented at create_order, restored at reject_order/cancel_order
escrow_id is derived from the first 8 bytes of the order_account PDA to guarantee uniqueness without coordinator state
close_stale_order can be called by anyone to clean up an OrderAccount whose descro escrow is already terminal
max_slippage_bps argument on create_order protects buyer from price movement between submission and confirmation
SPL token path (descro_spl CPI) is not yet implemented — create_order errors on payment_currency = Spl until descro_spl exists; state and oracle are designed to support it without schema changes

Tech Stack: Rust, Anchor 1.0.x, LiteSVM 0.10.0, pyth-solana-receiver-sdk for oracle reads. Build order: descro_ext_resolvers → descro → solisting.

File Map

Action	Path	Responsibility
Create	`programs/solisting/Cargo.toml`	Crate definition + dependencies (incl. pyth-solana-receiver-sdk)
Create	`programs/solisting/src/lib.rs`	Program entrypoints + declare_id!
Create	`programs/solisting/src/state.rs`	`ListingAccount`, `OrderAccount`, `Currency` enum, `AltCurrencyConfig`
Create	`programs/solisting/src/error.rs`	`SolistingError` enum
Create	`programs/solisting/src/oracle.rs`	Generic Pyth feed reader + USD-intermediate cross-currency conversion + slippage check
Create	`programs/solisting/src/instructions.rs`	Module re-exports
Create	`programs/solisting/src/instructions/create_listing.rs`	Init `ListingAccount`
Create	`programs/solisting/src/instructions/update_listing.rs`	Mutate price/quantity/currencies
Create	`programs/solisting/src/instructions/close_listing.rs`	Close `ListingAccount`
Create	`programs/solisting/src/instructions/create_order.rs`	Validate currency, optional oracle conversion, CPI `buyer_create_escrow`
Create	`programs/solisting/src/instructions/accept_order.rs`	CPI `seller_confirm`, close `OrderAccount`
Create	`programs/solisting/src/instructions/reject_order.rs`	Defensive CPI `cancel`, close `OrderAccount`
Create	`programs/solisting/src/instructions/cancel_order.rs`	Defensive CPI `cancel`, close `OrderAccount`
Create	`programs/solisting/src/instructions/close_stale_order.rs`	Clean up orphaned `OrderAccount`
Create	`programs/solisting/tests/common/mod.rs`	LiteSVM setup, helpers, mock oracle account builder
Create	`programs/solisting/tests/test_listings.rs`	Listing instruction tests
Create	`programs/solisting/tests/test_orders.rs`	Order flow tests
Modify	`Cargo.toml` (workspace root)	Add solisting to workspace members

Task 1: Workspace + Crate Setup

Step 1: Add solisting to workspace root Cargo.toml

Add "programs/solisting" to the [workspace] members array.

Step 2: Create programs/solisting/Cargo.toml

[package]
name = "solisting"
version = "0.1.0"
edition = "2021"

[lib]
crate-type = ["cdylib", "lib"]
name = "solisting"

[features]
default = []
cpi = ["no-entrypoint"]
no-entrypoint = []
no-idl = []
no-log-ix-name = []
idl-build = ["anchor-lang/idl-build"]
anchor-debug = []
custom-heap = []
custom-panic = []

[dependencies]
anchor-lang = "1.0.2"
descro = { path = "../descro", features = ["cpi"] }
descro_ext_resolvers = { path = "../descro_ext_resolvers" }
# Pyth oracle SDK for on-chain price reads (Pull Oracle / V2 accounts).
# Verify latest compatible version at https://crates.io/crates/pyth-solana-receiver-sdk
pyth-solana-receiver-sdk = "0.3"

[dev-dependencies]
litesvm = "0.10.0"
solana-message = "3.0.1"
solana-transaction = "3.0.2"
solana-signer = "3.0.0"
solana-keypair = "3.0.1"

[lints.rust]
unexpected_cfgs = { level = "warn", check-cfg = ['cfg(target_os, values("solana"))'] }

Step 3: Create directory structure

mkdir -p programs/solisting/src/instructions programs/solisting/tests/common
touch programs/solisting/src/lib.rs
touch programs/solisting/src/state.rs
touch programs/solisting/src/error.rs
touch programs/solisting/src/oracle.rs
touch programs/solisting/src/instructions.rs
touch programs/solisting/src/instructions/create_listing.rs
touch programs/solisting/src/instructions/update_listing.rs
touch programs/solisting/src/instructions/close_listing.rs
touch programs/solisting/src/instructions/create_order.rs
touch programs/solisting/src/instructions/accept_order.rs
touch programs/solisting/src/instructions/reject_order.rs
touch programs/solisting/src/instructions/cancel_order.rs
touch programs/solisting/src/instructions/close_stale_order.rs

Step 4: Commit skeleton

git add programs/solisting/ Cargo.toml Cargo.lock
git commit -m "chore(solisting): add crate skeleton and workspace entry"

Task 2: State, Errors, Oracle Module

Files: state.rs, error.rs, oracle.rs

Step 1: Write state.rs

use anchor_lang::prelude::*;

/// Payment currency identifier. Amounts are always in the currency's smallest unit:
/// Sol → Lamports (u64), Spl → token units (smallest unit per `decimals`).
#[derive(AnchorSerialize, AnchorDeserialize, Clone, InitSpace, Debug, PartialEq)]
pub enum Currency {
    Sol,
    /// `decimals` mirrors the SPL mint's decimals field (e.g. 6 for USDC/USDT, 5 for BONK).
    /// Storing it here avoids a mint account lookup at order time.
    Spl { mint: Pubkey, decimals: u8 },
}

impl Currency {
    pub fn decimals(&self) -> u8 {
        match self {
            Currency::Sol => 9,
            Currency::Spl { decimals, .. } => *decimals,
        }
    }
}

/// Per-alt-currency oracle configuration. Each alt currency carries its own Pyth feed
/// because different tokens have different price feeds.
#[derive(AnchorSerialize, AnchorDeserialize, Clone, InitSpace, Debug)]
pub struct AltCurrencyConfig {
    pub currency: Currency,
    /// Pyth V2 PriceFeedAccount for this token priced in USD (TOKEN/USD).
    /// `None` = treat as a $1.00 USD stablecoin — no oracle account required at order time.
    pub usd_oracle: Option<Pubkey>,
}

#[account]
#[derive(InitSpace)]
pub struct ListingAccount {
    pub seller: Pubkey,
    /// Sole source of truth for price. All alt_currencies are derived from this via oracle.
    pub canonical_currency: Currency,
    /// Price in canonical_currency's smallest unit.
    pub price: u64,
    /// Pyth V2 PriceFeedAccount for the canonical currency priced in USD.
    /// `None` = canonical is a $1.00 USD stablecoin.
    /// For Sol canonical: set to the SOL/USD Pyth feed.
    pub canonical_oracle: Option<Pubkey>,
    /// Alt currencies the seller accepts. Amounts are oracle-computed at create_order time.
    /// Empty = no oracle ever needed.
    #[max_len(3)]
    pub alt_currencies: Vec<AltCurrencyConfig>,
    /// Resolvers the seller accepts for dispute resolution. Empty = any resolver ok.
    #[max_len(4)]
    pub accepted_resolvers: Vec<Pubkey>,
    /// Total units the seller offers (includes quantity_reserved).
    pub quantity: u32,
    /// Units held by pending orders. available = quantity - quantity_reserved.
    pub quantity_reserved: u32,
    #[max_len(256)]
    pub metadata_uri: String,
    pub listing_id: u64,
    pub is_active: bool,
    pub bump: u8,
}

#[account]
#[derive(InitSpace)]
pub struct OrderAccount {
    pub listing: Pubkey,
    pub buyer: Pubkey,
    pub seller: Pubkey,
    pub resolver: Pubkey,
    /// The currency the buyer chose to pay in.
    pub payment_currency: Currency,
    /// Actual amount paid (may differ from price when oracle-converted).
    pub amount: u64,
    /// The descro EscrowAccount PDA for this order.
    pub escrow_account: Pubkey,
    /// Derived from order_account PDA bytes[0..8]; used as descro escrow_id seed.
    pub escrow_id: u64,
    pub order_id: u64,
    pub created_at: i64,
    pub bump: u8,
}

Step 2: Write error.rs

use anchor_lang::prelude::*;

#[error_code]
pub enum SolistingError {
    #[msg("Listing is not active")]
    ListingNotActive,
    #[msg("No quantity available")]
    OutOfStock,
    #[msg("Signer is not authorized")]
    Unauthorized,
    #[msg("Currency not accepted by this listing")]
    CurrencyNotAccepted,
    #[msg("Resolver is not accepted by this listing")]
    ResolverNotAccepted,
    #[msg("Oracle account is required but was not provided (non-stablecoin currency)")]
    OracleRequired,
    #[msg("Passed oracle account key does not match the address stored in the listing")]
    OracleMismatch,
    #[msg("Oracle price is unavailable, stale, or has too wide a confidence interval")]
    OraclePriceUnavailable,
    #[msg("Slippage tolerance exceeded — oracle rate moved unfavorably since tx was built")]
    SlippageExceeded,
    #[msg("SPL payment path not yet implemented — descro_spl does not exist")]
    SplNotImplemented,
    #[msg("Descro escrow is not in expected state")]
    EscrowStateUnexpected,
    #[msg("Descro program address mismatch")]
    InvalidDescroProgram,
}

Step 3: Write oracle.rs

The oracle module converts between any two currencies using USD as an intermediate. Each currency has an optional Pyth feed (TOKEN/USD). None = treat as $1.00 stablecoin. No feed ID is hardcoded — the seller registers the oracle account address in the listing; the program only verifies that the passed account key matches the stored key (done in create_order, not here).

Math (using USD as pivot):

canonical_usd  = price × (cp_raw × 10^cp_expo) / 10^cd
target_amount  = canonical_usd   × 10^td / (tp_raw × 10^tp_expo)
              = price × cp_raw / tp_raw × 10^(cp_expo − tp_expo + td − cd)
let shift      = cp_expo − tp_expo + td − cd   (can be positive or negative)

Stablecoin sentinel: (1, 0) meaning exactly $1.00 per whole token.

Example — SOL → BONK (cd=9, cp_expo=−8, td=5, tp_expo=−8): shift = −8 − (−8) + 5 − 9 = −4 → target = ca × cp_raw / tp_raw / 10^4

Example — SOL → USDC (cd=9, cp_expo=−8, td=6, tp_raw=1, tp_expo=0 sentinel): shift = −8 − 0 + 6 − 9 = −11 → target = ca × cp_raw / 10^11 ✓ (matches old formula)

use anchor_lang::prelude::*;
use anchor_lang::AccountDeserialize;
use pyth_solana_receiver_sdk::price_update::PriceUpdateV2;
use crate::error::SolistingError;
use crate::state::Currency;

const ORACLE_MAX_AGE_SECS: i64 = 60;

/// Reads any Pyth V2 PriceFeedAccount and returns (price_i64, exponent_i32) where
/// `price * 10^exponent` is the USD value of 1 whole token (price in USD per whole unit).
/// The caller is responsible for verifying the account key matches listing state.
fn read_usd_price(oracle_account: &AccountInfo) -> Result<(i64, i32)> {
    let data = oracle_account.try_borrow_data()?;
    let price_update = PriceUpdateV2::try_deserialize(&mut data.as_ref())
        .map_err(|_| error!(SolistingError::OraclePriceUnavailable))?;
    let msg = &price_update.price_message;
    let now = Clock::get()?.unix_timestamp;
    require!(
        now - msg.publish_time <= ORACLE_MAX_AGE_SECS,
        SolistingError::OraclePriceUnavailable
    );
    require!(msg.price > 0, SolistingError::OraclePriceUnavailable);
    Ok((msg.price, msg.exponent))
}

/// Returns the USD price as (raw_i64, exponent_i32) for a currency.
/// Stablecoin sentinel (oracle = None) returns (1, 0) = exactly $1.00 per whole token.
fn usd_price(oracle: Option<&AccountInfo>) -> Result<(i64, i32)> {
    match oracle {
        None => Ok((1, 0)),
        Some(account) => read_usd_price(account),
    }
}

/// Converts `price` (smallest units of `canonical_currency`) to the equivalent
/// amount in `target_currency` smallest units, using USD as an intermediate.
///
/// `canonical_oracle` / `target_oracle`: pass `None` when the currency is a USD stablecoin.
/// `canonical_currency` / `target_currency`: used only for their `decimals()` value.
///
/// Slippage: if |computed − expected_amount| / expected_amount > max_slippage_bps / 10_000,
/// returns `SlippageExceeded`. Pass `max_slippage_bps = 0` to skip the check.
pub fn convert_with_slippage(
    canonical_oracle: Option<&AccountInfo>,
    canonical_currency: &Currency,
    price: u64,
    target_oracle: Option<&AccountInfo>,
    target_currency: &Currency,
    expected_amount: u64,
    max_slippage_bps: u16,
) -> Result<u64> {
    let (cp_raw, cp_expo) = usd_price(canonical_oracle)?;
    let (tp_raw, tp_expo) = usd_price(target_oracle)?;

    let cd = canonical_currency.decimals() as i32;
    let td = target_currency.decimals() as i32;

    // shift = cp_expo − tp_expo + td − cd
    let shift: i32 = cp_expo - tp_expo + td - cd;

    // target = price × cp_raw / tp_raw × 10^shift
    // Use u128 to avoid overflow. tp_raw and cp_raw are always positive (checked above).
    let numerator = (price as u128)
        .checked_mul(cp_raw as u128)
        .ok_or(error!(SolistingError::OraclePriceUnavailable))?;

    let computed: u64 = if shift >= 0 {
        let scaled = numerator
            .checked_mul(10u128.pow(shift as u32))
            .ok_or(error!(SolistingError::OraclePriceUnavailable))?;
        u64::try_from(scaled / tp_raw as u128)
            .map_err(|_| error!(SolistingError::OraclePriceUnavailable))?
    } else {
        let divisor = 10u128.pow((-shift) as u32);
        u64::try_from(numerator / divisor / tp_raw as u128)
            .map_err(|_| error!(SolistingError::OraclePriceUnavailable))?
    };

    if max_slippage_bps > 0 && expected_amount > 0 {
        let tolerance = (expected_amount as u128)
            .checked_mul(max_slippage_bps as u128)
            .unwrap_or(u128::MAX)
            / 10_000;
        let diff = computed.abs_diff(expected_amount) as u128;
        require!(diff <= tolerance, SolistingError::SlippageExceeded);
    }

    Ok(computed)
}

Step 4: Verify state.rs compiles in isolation (no instruction files yet)

cargo check --manifest-path programs/solisting/Cargo.toml 2>&1 | head -20

Expected: errors only about missing modules (lib.rs not wired yet), no type errors in state.rs itself.

Step 5: Commit

git add programs/solisting/src/state.rs programs/solisting/src/error.rs programs/solisting/src/oracle.rs
git commit -m "feat(solisting): add state, errors, and oracle conversion module"

Task 3: Listing Instructions

Files: create_listing.rs, update_listing.rs, close_listing.rs

Step 1: Write failing tests in tests/test_listings.rs

mod common;
use common::*;

#[test]
fn seller_can_create_sol_only_listing() {
    let (mut svm, seller, _) = setup();
    let listing_id: u64 = 1;
    let price = 100_000_000u64; // 0.1 SOL in lamports

    let ix = ix_create_listing(
        &seller.pubkey(),
        listing_id,
        Currency::Sol,
        price,
        None,           // canonical_oracle: None (no alt currencies)
        vec![],         // no alt_currencies
        vec![],         // any resolver
        10,             // quantity
        "ipfs://test".to_string(),
    );
    send(&mut svm, &[ix], &[&seller]);

    let listing = read_listing(&svm, &seller.pubkey(), listing_id);
    assert_eq!(listing.canonical_currency, Currency::Sol);
    assert_eq!(listing.price, price);
    assert_eq!(listing.alt_currencies.len(), 0);
    assert_eq!(listing.canonical_oracle, None);
    assert_eq!(listing.quantity, 10);
    assert_eq!(listing.quantity_reserved, 0);
    assert!(listing.is_active);
}

#[test]
fn seller_can_create_listing_with_usdc_alt_stablecoin() {
    // canonical=Sol, alt=USDC with no oracle (stablecoin $1 peg)
    let (mut svm, seller, _) = setup();
    let usdc_mint = Pubkey::new_unique();
    let sol_usd_feed = Pubkey::new_unique(); // mock SOL/USD feed key
    let ix = ix_create_listing(
        &seller.pubkey(),
        10,
        Currency::Sol,
        1_000_000_000,
        Some(sol_usd_feed),     // canonical_oracle = SOL/USD feed
        vec![AltCurrencyConfig {
            currency: Currency::Spl { mint: usdc_mint, decimals: 6 },
            usd_oracle: None,   // USDC is a stablecoin — no feed needed
        }],
        vec![],
        5,
        "ipfs://x".to_string(),
    );
    send(&mut svm, &[ix], &[&seller]);

    let listing = read_listing(&svm, &seller.pubkey(), 10);
    assert_eq!(listing.canonical_oracle, Some(sol_usd_feed));
    assert_eq!(listing.alt_currencies[0].usd_oracle, None);
}

#[test]
fn seller_can_create_listing_with_bonk_alt_oracle() {
    // canonical=Sol, alt=BONK — needs both SOL/USD and BONK/USD feeds
    let (mut svm, seller, _) = setup();
    let bonk_mint = Pubkey::new_unique();
    let sol_usd_feed = Pubkey::new_unique();
    let bonk_usd_feed = Pubkey::new_unique();
    let ix = ix_create_listing(
        &seller.pubkey(),
        11,
        Currency::Sol,
        1_000_000_000,
        Some(sol_usd_feed),
        vec![AltCurrencyConfig {
            currency: Currency::Spl { mint: bonk_mint, decimals: 5 },
            usd_oracle: Some(bonk_usd_feed),
        }],
        vec![],
        5,
        "".to_string(),
    );
    send(&mut svm, &[ix], &[&seller]);

    let listing = read_listing(&svm, &seller.pubkey(), 11);
    assert_eq!(listing.canonical_oracle, Some(sol_usd_feed));
    assert_eq!(listing.alt_currencies[0].usd_oracle, Some(bonk_usd_feed));
}

#[test]
fn seller_can_update_listing() {
    let (mut svm, seller, _) = setup();
    let listing_id: u64 = 2;
    let ix = ix_create_listing(&seller.pubkey(), listing_id, Currency::Sol, 1_000_000_000, None, vec![], vec![], 10, "".to_string());
    send(&mut svm, &[ix], &[&seller]);

    let ix_update = ix_update_listing(
        &seller.pubkey(),
        listing_id,
        Currency::Sol,
        2_000_000_000,
        None,
        vec![],
        vec![],
        20,
        "ipfs://new".to_string(),
    );
    send(&mut svm, &[ix_update], &[&seller]);

    let listing = read_listing(&svm, &seller.pubkey(), listing_id);
    assert_eq!(listing.price, 2_000_000_000);
    assert_eq!(listing.quantity, 20);
}

#[test]
fn seller_can_close_listing() {
    let (mut svm, seller, _) = setup();
    let listing_id: u64 = 3;
    let ix = ix_create_listing(&seller.pubkey(), listing_id, Currency::Sol, 1_000_000_000, None, vec![], vec![], 5, "".to_string());
    send(&mut svm, &[ix], &[&seller]);

    let ix_close = ix_close_listing(&seller.pubkey(), listing_id);
    send(&mut svm, &[ix_close], &[&seller]);

    let pda = listing_pda(&seller.pubkey(), listing_id);
    assert!(svm.get_account(&pda).is_none());
}

Step 2: Run tests — verify they fail with "unresolved" errors (not compiled yet)

cargo test --manifest-path programs/solisting/Cargo.toml --test test_listings 2>&1 | head -20

Expected: compile errors (ix helpers not defined yet).

Step 3: Write create_listing.rs

use anchor_lang::prelude::*;
use crate::state::{Currency, ListingAccount};
use crate::error::SolistingError;

#[derive(Accounts)]
#[instruction(listing_id: u64)]
pub struct CreateListing<'info> {
    #[account(mut)]
    pub seller: Signer<'info>,

    #[account(
        init,
        payer = seller,
        space = 8 + ListingAccount::INIT_SPACE,
        seeds = [b"listing", seller.key().as_ref(), &listing_id.to_le_bytes()],
        bump
    )]
    pub listing_account: Account<'info, ListingAccount>,

    pub system_program: Program<'info, System>,
}

pub fn handler(
    ctx: Context<CreateListing>,
    listing_id: u64,
    canonical_currency: Currency,
    price: u64,
    canonical_oracle: Option<Pubkey>,
    alt_currencies: Vec<AltCurrencyConfig>,
    accepted_resolvers: Vec<Pubkey>,
    quantity: u32,
    metadata_uri: String,
) -> Result<()> {
    let listing = &mut ctx.accounts.listing_account;
    listing.seller = ctx.accounts.seller.key();
    listing.canonical_currency = canonical_currency;
    listing.price = price;
    listing.canonical_oracle = canonical_oracle;
    listing.alt_currencies = alt_currencies;
    listing.accepted_resolvers = accepted_resolvers;
    listing.quantity = quantity;
    listing.quantity_reserved = 0;
    listing.metadata_uri = metadata_uri;
    listing.listing_id = listing_id;
    listing.is_active = true;
    listing.bump = ctx.bumps.listing_account;
    Ok(())
}

Step 4: Write update_listing.rs

use anchor_lang::prelude::*;
use crate::state::{Currency, ListingAccount};
use crate::error::SolistingError;

#[derive(Accounts)]
pub struct UpdateListing<'info> {
    pub seller: Signer<'info>,

    #[account(
        mut,
        seeds = [b"listing", listing_account.seller.as_ref(), &listing_account.listing_id.to_le_bytes()],
        bump = listing_account.bump,
        constraint = seller.key() == listing_account.seller @ SolistingError::Unauthorized,
        constraint = listing_account.is_active @ SolistingError::ListingNotActive,
    )]
    pub listing_account: Account<'info, ListingAccount>,
}

pub fn handler(
    ctx: Context<UpdateListing>,
    canonical_currency: Currency,
    price: u64,
    canonical_oracle: Option<Pubkey>,
    alt_currencies: Vec<AltCurrencyConfig>,
    accepted_resolvers: Vec<Pubkey>,
    quantity: u32,
    metadata_uri: String,
) -> Result<()> {
    let listing = &mut ctx.accounts.listing_account;
    listing.canonical_currency = canonical_currency;
    listing.price = price;
    listing.canonical_oracle = canonical_oracle;
    listing.alt_currencies = alt_currencies;
    listing.accepted_resolvers = accepted_resolvers;
    listing.quantity = quantity;
    listing.metadata_uri = metadata_uri;
    Ok(())
}

Step 5: Write close_listing.rs

use anchor_lang::prelude::*;
use crate::state::ListingAccount;
use crate::error::SolistingError;

#[derive(Accounts)]
pub struct CloseListing<'info> {
    #[account(mut)]
    pub seller: Signer<'info>,

    #[account(
        mut,
        seeds = [b"listing", listing_account.seller.as_ref(), &listing_account.listing_id.to_le_bytes()],
        bump = listing_account.bump,
        constraint = seller.key() == listing_account.seller @ SolistingError::Unauthorized,
        close = seller,
    )]
    pub listing_account: Account<'info, ListingAccount>,
}

pub fn handler(_ctx: Context<CloseListing>) -> Result<()> {
    Ok(())
}

Step 6: Write tests/common/mod.rs skeleton (listing helpers only for now)

use litesvm::LiteSVM;
use solana_keypair::Keypair;
use solana_signer::Signer;
use anchor_lang::prelude::Pubkey;
use solisting::state::{Currency, ListingAccount};

pub fn setup() -> (LiteSVM, Keypair, Keypair) {
    let mut svm = LiteSVM::new();
    svm.add_program_from_file(
        solisting::id(),
        "../../target/deploy/solisting.so",
    ).unwrap();
    let seller = Keypair::new();
    let buyer = Keypair::new();
    svm.airdrop(&seller.pubkey(), 10_000_000_000).unwrap();
    svm.airdrop(&buyer.pubkey(), 10_000_000_000).unwrap();
    (svm, seller, buyer)
}

pub fn listing_pda(seller: &Pubkey, listing_id: u64) -> Pubkey {
    Pubkey::find_program_address(
        &[b"listing", seller.as_ref(), &listing_id.to_le_bytes()],
        &solisting::id(),
    ).0
}

pub fn read_listing(svm: &LiteSVM, seller: &Pubkey, listing_id: u64) -> ListingAccount {
    let pda = listing_pda(seller, listing_id);
    let account = svm.get_account(&pda).unwrap();
    ListingAccount::try_deserialize(&mut account.data.as_slice()).unwrap()
}

pub fn send(svm: &mut LiteSVM, ixs: &[solana_message::compiled_instruction::CompiledInstruction], signers: &[&Keypair]) {
    // build and send transaction — adapt to LiteSVM 0.10 API (see existing descro tests for pattern)
    todo!("fill from descro tests/common/mod.rs send() helper")
}

pub fn try_send(svm: &mut LiteSVM, ixs: &[solana_message::compiled_instruction::CompiledInstruction], signers: &[&Keypair]) -> Result<(), Box<dyn std::error::Error>> {
    todo!("fill from descro tests/common/mod.rs try_send() helper")
}

// --- Instruction builders ---

pub fn ix_create_listing(
    seller: &Pubkey,
    listing_id: u64,
    canonical_currency: Currency,
    price: u64,
    canonical_oracle: Option<Pubkey>,
    alt_currencies: Vec<AltCurrencyConfig>,
    accepted_resolvers: Vec<Pubkey>,
    quantity: u32,
    metadata_uri: String,
) -> solana_message::compiled_instruction::CompiledInstruction {
    todo!("build anchor instruction for create_listing")
}

pub fn ix_update_listing(
    seller: &Pubkey,
    listing_id: u64,
    canonical_currency: Currency,
    price: u64,
    canonical_oracle: Option<Pubkey>,
    alt_currencies: Vec<AltCurrencyConfig>,
    accepted_resolvers: Vec<Pubkey>,
    quantity: u32,
    metadata_uri: String,
) -> solana_message::compiled_instruction::CompiledInstruction {
    todo!("build anchor instruction for update_listing")
}

pub fn ix_close_listing(
    seller: &Pubkey,
    listing_id: u64,
) -> solana_message::compiled_instruction::CompiledInstruction {
    todo!("build anchor instruction for close_listing")
}

Note: Copy the send() / try_send() pattern from programs/descro/tests/common/mod.rs and wire the instruction builders using Anchor's discriminator + borsh-encode args pattern from those existing tests.

Step 7: Wire lib.rs and instructions.rs (listing instructions only)

instructions.rs:

pub mod close_listing;
pub mod create_listing;
pub mod update_listing;

pub use close_listing::*;
pub use create_listing::*;
pub use update_listing::*;

lib.rs (listing portion — extend in Task 4):

pub mod error;
pub mod instructions;
pub mod oracle;
pub mod state;

use anchor_lang::prelude::*;
pub use error::*;
pub use instructions::*;
pub use state::*;

declare_id!("So1istingProgramID11111111111111111111111111"); // replace after anchor keys list

#[program]
pub mod solisting {
    use super::*;

    pub fn create_listing(
        ctx: Context<CreateListing>,
        listing_id: u64,
        canonical_currency: state::Currency,
        price: u64,
        canonical_oracle: Option<Pubkey>,
        alt_currencies: Vec<state::AltCurrencyConfig>,
        accepted_resolvers: Vec<Pubkey>,
        quantity: u32,
        metadata_uri: String,
    ) -> Result<()> {
        create_listing::handler(
            ctx, listing_id, canonical_currency, price,
            canonical_oracle, alt_currencies, accepted_resolvers, quantity, metadata_uri,
        )
    }

    pub fn update_listing(
        ctx: Context<UpdateListing>,
        canonical_currency: state::Currency,
        price: u64,
        canonical_oracle: Option<Pubkey>,
        alt_currencies: Vec<state::AltCurrencyConfig>,
        accepted_resolvers: Vec<Pubkey>,
        quantity: u32,
        metadata_uri: String,
    ) -> Result<()> {
        update_listing::handler(
            ctx, canonical_currency, price,
            canonical_oracle, alt_currencies, accepted_resolvers, quantity, metadata_uri,
        )
    }

    pub fn close_listing(ctx: Context<CloseListing>) -> Result<()> {
        close_listing::handler(ctx)
    }
}

Step 8: Build and run listing tests

cargo build-sbf --manifest-path programs/descro_ext_resolvers/Cargo.toml && \
cargo build-sbf --manifest-path programs/descro/Cargo.toml && \
cargo build-sbf --manifest-path programs/solisting/Cargo.toml
cargo test --manifest-path programs/solisting/Cargo.toml --test test_listings 2>&1 | tail -10

Expected: all listing tests pass.

Step 9: Commit

git add programs/solisting/
git commit -m "feat(solisting): implement listing create/update/close with canonical price model"

Task 4: `create_order` — Validate Currency, Oracle Conversion, CPI `buyer_create_escrow`

The buyer's single transaction: validates payment currency against listing, optionally reads oracle, reserves quantity, CPIs descro.buyer_create_escrow.

File: programs/solisting/src/instructions/create_order.rs

Step 1: Write failing tests in tests/test_orders.rs

mod common;
use common::*;

#[test]
fn buyer_can_create_order_canonical_sol() {
    // Listing: canonical=Sol(0.1 SOL), no alt_currencies
    // Buyer creates order paying in Sol
    // Assert: OrderAccount exists with payment_currency=Sol, amount=0.1 SOL in lamports
    // Assert: descro EscrowAccount exists, state == AwaitingSellerConfirm
    // Assert: descro vault has listing.price lamports
    // Assert: listing.quantity_reserved == 1
    let (mut svm, seller, buyer) = setup();
    let listing_id = 1u64;
    let price = 100_000_000u64;
    let ix = ix_create_listing(&seller.pubkey(), listing_id, Currency::Sol, price, None, vec![], vec![], 5, "".to_string());
    send(&mut svm, &[ix], &[&seller]);

    let order_id = 1u64;
    let ix_order = ix_create_order(
        &buyer.pubkey(),
        &seller.pubkey(),
        listing_id,
        order_id,
        Currency::Sol,
        0,   // max_slippage_bps — unused for canonical
        None, // no oracle account needed
    );
    send(&mut svm, &[ix_order], &[&buyer]);

    let order = read_order(&svm, listing_pda(&seller.pubkey(), listing_id), buyer.pubkey(), order_id);
    assert_eq!(order.payment_currency, Currency::Sol);
    assert_eq!(order.amount, price);

    let listing = read_listing(&svm, &seller.pubkey(), listing_id);
    assert_eq!(listing.quantity_reserved, 1);
}

#[test]
fn create_order_fails_if_listing_inactive() {
    let (mut svm, seller, buyer) = setup();
    let listing_id = 2u64;
    let ix = ix_create_listing(&seller.pubkey(), listing_id, Currency::Sol, 1_000_000_000, None, vec![], vec![], 1, "".to_string());
    send(&mut svm, &[ix], &[&seller]);
    let ix_close = ix_close_listing(&seller.pubkey(), listing_id);
    send(&mut svm, &[ix_close], &[&seller]);

    let result = try_send(&mut svm, &[ix_create_order(
        &buyer.pubkey(), &seller.pubkey(), listing_id, 1, Currency::Sol, 0, None,
    )], &[&buyer]);
    assert!(result.is_err());
}

#[test]
fn create_order_fails_if_out_of_stock() {
    let (mut svm, seller, buyer) = setup();
    let listing_id = 3u64;
    // quantity = 1, reserve it with first order
    let ix = ix_create_listing(&seller.pubkey(), listing_id, Currency::Sol, 100_000_000, None, vec![], vec![], 1, "".to_string());
    send(&mut svm, &[ix], &[&seller]);
    send(&mut svm, &[ix_create_order(&buyer.pubkey(), &seller.pubkey(), listing_id, 1, Currency::Sol, 0, None, None)], &[&buyer]);

    let buyer2 = Keypair::new();
    svm.airdrop(&buyer2.pubkey(), 10_000_000_000).unwrap();
    let result = try_send(&mut svm, &[ix_create_order(&buyer2.pubkey(), &seller.pubkey(), listing_id, 2, Currency::Sol, 0, None, None)], &[&buyer2]);
    assert!(result.is_err());
}

#[test]
fn create_order_fails_if_currency_not_accepted() {
    let (mut svm, seller, buyer) = setup();
    let listing_id = 4u64;
    // Sol-only listing — buyer tries to pay with fake SPL
    let ix = ix_create_listing(&seller.pubkey(), listing_id, Currency::Sol, 100_000_000, None, vec![], vec![], 5, "".to_string());
    send(&mut svm, &[ix], &[&seller]);

    let fake_mint = Pubkey::new_unique();
    let result = try_send(&mut svm, &[ix_create_order(
        &buyer.pubkey(), &seller.pubkey(), listing_id, 1, Currency::Spl { mint: fake_mint, decimals: 6 }, 0, None, None,
    )], &[&buyer]);
    assert!(result.is_err());
}

#[test]
fn create_order_fails_if_resolver_not_accepted() {
    let (mut svm, seller, buyer) = setup();
    let listing_id = 5u64;
    let allowed_resolver = Pubkey::new_unique();
    let ix = ix_create_listing(&seller.pubkey(), listing_id, Currency::Sol, 100_000_000, None, vec![], vec![allowed_resolver], 5, "".to_string());
    send(&mut svm, &[ix], &[&seller]);

    // Pass a different resolver — must fail
    let result = try_send(&mut svm, &[ix_create_order_with_resolver(
        &buyer.pubkey(), &seller.pubkey(), listing_id, 1, Currency::Sol, 0, None, None, Pubkey::new_unique(),
    )], &[&buyer]);
    assert!(result.is_err());
}

Step 2: Run tests — verify compile failure (create_order instruction not yet written)

cargo test --manifest-path programs/solisting/Cargo.toml --test test_orders 2>&1 | head -10

Expected: compile errors.

Step 3: Implement create_order.rs

use anchor_lang::prelude::*;
use crate::state::{Currency, ListingAccount, OrderAccount};
use crate::error::SolistingError;
use crate::oracle;

#[derive(Accounts)]
#[instruction(order_id: u64, escrow_id: u64, resolver: Pubkey, payment_currency: Currency)]
pub struct CreateOrder<'info> {
    #[account(mut)]
    pub buyer: Signer<'info>,

    /// CHECK: Seller — verified against listing.seller
    pub seller: UncheckedAccount<'info>,

    #[account(
        mut,
        seeds = [b"listing", listing_account.seller.as_ref(), &listing_account.listing_id.to_le_bytes()],
        bump = listing_account.bump,
        constraint = listing_account.is_active @ SolistingError::ListingNotActive,
        constraint = listing_account.quantity > listing_account.quantity_reserved @ SolistingError::OutOfStock,
        constraint = seller.key() == listing_account.seller @ SolistingError::Unauthorized,
    )]
    pub listing_account: Account<'info, ListingAccount>,

    #[account(
        init,
        payer = buyer,
        space = 8 + OrderAccount::INIT_SPACE,
        seeds = [b"order", listing_account.key().as_ref(), buyer.key().as_ref(), &order_id.to_le_bytes()],
        bump
    )]
    pub order_account: Account<'info, OrderAccount>,

    /// CHECK: Descro EscrowAccount PDA — created by the CPI
    #[account(
        mut,
        seeds = [b"escrow", seller.key().as_ref(), &escrow_id.to_le_bytes()],
        bump,
        seeds::program = descro::id(),
    )]
    pub escrow_account: UncheckedAccount<'info>,

    /// CHECK: Descro vault PDA — funded by the CPI
    #[account(
        mut,
        seeds = [b"vault", escrow_account.key().as_ref()],
        bump,
        seeds::program = descro::id(),
    )]
    pub descro_vault: UncheckedAccount<'info>,

    /// CHECK: Pyth USD feed for the canonical currency (listing.canonical_oracle).
    /// Pass SystemProgram as placeholder when canonical_oracle is None (stablecoin).
    pub canonical_oracle: UncheckedAccount<'info>,

    /// CHECK: Pyth USD feed for the chosen alt currency (alt_cfg.usd_oracle).
    /// Pass SystemProgram as placeholder when usd_oracle is None (stablecoin).
    /// Also pass SystemProgram when paying in the canonical currency (oracle unused).
    pub target_oracle: UncheckedAccount<'info>,

    /// CHECK: Descro program — verified in handler
    pub descro_program: UncheckedAccount<'info>,

    pub system_program: Program<'info, System>,
}

pub fn handler(
    ctx: Context<CreateOrder>,
    order_id: u64,
    escrow_id: u64,
    resolver: Pubkey,
    payment_currency: Currency,
    expected_amount: u64, // amount buyer expects to pay (for slippage check)
    max_slippage_bps: u16,
) -> Result<()> {
    require!(
        ctx.accounts.descro_program.key() == descro::id(),
        SolistingError::InvalidDescroProgram
    );

    let listing = &ctx.accounts.listing_account;

    // Validate resolver
    if !listing.accepted_resolvers.is_empty() {
        require!(
            listing.accepted_resolvers.contains(&resolver),
            SolistingError::ResolverNotAccepted
        );
    }

    // Determine amount in payment_currency
    let amount = if payment_currency == listing.canonical_currency {
        // Paying in canonical currency — no oracle needed
        listing.price
    } else {
        // Must be a configured alt_currency
        let alt_cfg = listing.alt_currencies
            .iter()
            .find(|c| c.currency == payment_currency)
            .ok_or(error!(SolistingError::CurrencyNotAccepted))?;

        // Validate passed oracle accounts against listing state
        if let Some(expected_canonical) = listing.canonical_oracle {
            require!(
                ctx.accounts.canonical_oracle.key() == expected_canonical,
                SolistingError::OracleMismatch
            );
        }
        if let Some(expected_target) = alt_cfg.usd_oracle {
            require!(
                ctx.accounts.target_oracle.key() == expected_target,
                SolistingError::OracleMismatch
            );
        }

        let c_oracle = listing.canonical_oracle.map(|_| ctx.accounts.canonical_oracle.as_ref());
        let t_oracle = alt_cfg.usd_oracle.map(|_| ctx.accounts.target_oracle.as_ref());

        oracle::convert_with_slippage(
            c_oracle,
            &listing.canonical_currency,
            listing.price,
            t_oracle,
            &payment_currency,
            expected_amount,
            max_slippage_bps,
        )?
    };

    // Only Sol payment supported now (descro_spl does not exist yet)
    require!(
        payment_currency == Currency::Sol,
        SolistingError::SplNotImplemented
    );

    // CPI: descro.buyer_create_escrow — creates EscrowAccount + funds vault atomically
    descro::cpi::buyer_create_escrow(
        CpiContext::new(
            ctx.accounts.descro_program.to_account_info(),
            descro::cpi::accounts::BuyerCreateEscrow {
                buyer: ctx.accounts.buyer.to_account_info(),
                seller: ctx.accounts.seller.to_account_info(),
                escrow_account: ctx.accounts.escrow_account.to_account_info(),
                vault: ctx.accounts.descro_vault.to_account_info(),
                system_program: ctx.accounts.system_program.to_account_info(),
            },
        ),
        amount,
        Some(resolver),
        escrow_id,
    )?;

    ctx.accounts.listing_account.quantity_reserved += 1;

    let order = &mut ctx.accounts.order_account;
    order.listing = ctx.accounts.listing_account.key();
    order.buyer = ctx.accounts.buyer.key();
    order.seller = ctx.accounts.seller.key();
    order.resolver = resolver;
    order.payment_currency = payment_currency;
    order.amount = amount;
    order.escrow_account = ctx.accounts.escrow_account.key();
    order.escrow_id = escrow_id;
    order.order_id = order_id;
    order.created_at = Clock::get()?.unix_timestamp;
    order.bump = ctx.bumps.order_account;
    Ok(())
}

escrow_id derivation note: Solisting passes escrow_id as an argument. The SDK derives it as u64::from_le_bytes(order_pda.to_bytes()[0..8]). This ties the escrow_id to the order PDA, ensuring uniqueness as long as order_id is unique per buyer+listing.

Step 4: Add order helpers to tests/common/mod.rs

Add order_pda(), read_order(), ix_create_order(), ix_create_order_with_resolver(). Mirror the pattern from listing helpers: PDA derivation, borsh-encode instruction data, build CompiledInstruction.

pub fn order_pda(listing: Pubkey, buyer: Pubkey, order_id: u64) -> Pubkey {
    Pubkey::find_program_address(
        &[b"order", listing.as_ref(), buyer.as_ref(), &order_id.to_le_bytes()],
        &solisting::id(),
    ).0
}

pub fn read_order(svm: &LiteSVM, listing: Pubkey, buyer: Pubkey, order_id: u64) -> solisting::state::OrderAccount {
    let pda = order_pda(listing, buyer, order_id);
    let account = svm.get_account(&pda).unwrap();
    solisting::state::OrderAccount::try_deserialize(&mut account.data.as_slice()).unwrap()
}

/// `canonical_oracle` / `target_oracle`: pass None to use SystemProgram as placeholder
/// (i.e. when paying in canonical currency or when the oracle is a stablecoin None).
pub fn ix_create_order(
    buyer: &Pubkey,
    seller: &Pubkey,
    listing_id: u64,
    order_id: u64,
    payment_currency: Currency,
    max_slippage_bps: u16,
    canonical_oracle: Option<Pubkey>,
    target_oracle: Option<Pubkey>,
) -> solana_message::compiled_instruction::CompiledInstruction {
    let listing = listing_pda(seller, listing_id);
    let order = order_pda(listing, *buyer, order_id);
    let escrow_id = u64::from_le_bytes(order.to_bytes()[0..8].try_into().unwrap());
    let resolver = Pubkey::new_unique(); // default resolver for simple tests
    ix_create_order_with_resolver(buyer, seller, listing_id, order_id, payment_currency, max_slippage_bps, canonical_oracle, target_oracle, resolver)
}

pub fn ix_create_order_with_resolver(
    buyer: &Pubkey,
    seller: &Pubkey,
    listing_id: u64,
    order_id: u64,
    payment_currency: Currency,
    max_slippage_bps: u16,
    canonical_oracle: Option<Pubkey>,
    target_oracle: Option<Pubkey>,
    resolver: Pubkey,
) -> solana_message::compiled_instruction::CompiledInstruction {
    let listing = listing_pda(seller, listing_id);
    let order = order_pda(listing, *buyer, order_id);
    let escrow_id = u64::from_le_bytes(order.to_bytes()[0..8].try_into().unwrap());
    let (escrow_account, _) = Pubkey::find_program_address(
        &[b"escrow", seller.as_ref(), &escrow_id.to_le_bytes()],
        &descro::id(),
    );
    let (descro_vault, _) = Pubkey::find_program_address(
        &[b"vault", escrow_account.as_ref()],
        &descro::id(),
    );
    let canonical_oracle_key = canonical_oracle.unwrap_or(solana_sdk::system_program::id());
    let target_oracle_key = target_oracle.unwrap_or(solana_sdk::system_program::id());
    let expected_amount = 0u64; // tests that don't use oracle set this to 0
    todo!("build CompiledInstruction: discriminator + borsh encode (order_id, escrow_id, resolver, payment_currency, expected_amount, max_slippage_bps), accounts: [..., canonical_oracle_key, target_oracle_key, ...]")
}

Step 5: Run tests

cargo build-sbf --manifest-path programs/solisting/Cargo.toml
cargo test --manifest-path programs/solisting/Cargo.toml --test test_orders -- buyer_can_create_order_canonical_sol create_order_fails 2>&1 | tail -20

Expected: all create_order_* tests pass.

Step 6: Commit

git add programs/solisting/
git commit -m "feat(solisting): implement create_order with oracle-driven currency conversion"

Task 5: `accept_order` — CPI `seller_confirm`

The seller accepts: CPIs descro.seller_confirm to move the escrow to Active, updates quantity, closes the OrderAccount.

File: programs/solisting/src/instructions/accept_order.rs

Step 1: Write failing test

#[test]
fn seller_accept_creates_active_descro_escrow() {
    let (mut svm, seller, buyer) = setup();
    let listing_id = 10u64;
    let price = 100_000_000u64;
    send(&mut svm, &[ix_create_listing(&seller.pubkey(), listing_id, Currency::Sol, price, None, vec![], vec![], 5, "".to_string())], &[&seller]);
    let order_id = 1u64;
    send(&mut svm, &[ix_create_order(&buyer.pubkey(), &seller.pubkey(), listing_id, order_id, Currency::Sol, 0, None, None)], &[&buyer]);

    let listing_key = listing_pda(&seller.pubkey(), listing_id);
    let order = read_order(&svm, listing_key, buyer.pubkey(), order_id);

    send(&mut svm, &[ix_accept_order(&seller.pubkey(), listing_id, buyer.pubkey(), order_id, order.escrow_id, order.resolver)], &[&seller]);

    // OrderAccount must be closed
    let order_key = order_pda(listing_key, buyer.pubkey(), order_id);
    assert!(svm.get_account(&order_key).is_none());

    // quantity reduced, reservation cleared
    let listing = read_listing(&svm, &seller.pubkey(), listing_id);
    assert_eq!(listing.quantity_reserved, 0);
    assert_eq!(listing.quantity, 4); // 5 - 1
}

Step 2: Implement accept_order.rs

use anchor_lang::prelude::*;
use crate::state::{ListingAccount, OrderAccount};
use crate::error::SolistingError;

#[derive(Accounts)]
pub struct AcceptOrder<'info> {
    #[account(mut)]
    pub seller: Signer<'info>,

    /// CHECK: Resolver — may need to co-sign if AcceptancePolicy is SignatureGated (descro enforces this)
    pub resolver: UncheckedAccount<'info>,

    #[account(
        mut,
        seeds = [b"listing", listing_account.seller.as_ref(), &listing_account.listing_id.to_le_bytes()],
        bump = listing_account.bump,
        constraint = seller.key() == listing_account.seller @ SolistingError::Unauthorized,
    )]
    pub listing_account: Account<'info, ListingAccount>,

    #[account(
        mut,
        seeds = [b"order", order_account.listing.as_ref(), order_account.buyer.as_ref(), &order_account.order_id.to_le_bytes()],
        bump = order_account.bump,
        constraint = seller.key() == order_account.seller @ SolistingError::Unauthorized,
        close = seller,
    )]
    pub order_account: Account<'info, OrderAccount>,

    /// CHECK: Descro EscrowAccount — state checked by descro.seller_confirm
    #[account(
        mut,
        seeds = [b"escrow", seller.key().as_ref(), &order_account.escrow_id.to_le_bytes()],
        bump,
        seeds::program = descro::id(),
        constraint = escrow_account.key() == order_account.escrow_account @ SolistingError::EscrowStateUnexpected,
    )]
    pub escrow_account: UncheckedAccount<'info>,

    /// CHECK: Optional resolver registry entry — passed through to descro.seller_confirm
    pub resolver_entry: UncheckedAccount<'info>,

    /// CHECK: Descro program
    pub descro_program: UncheckedAccount<'info>,

    pub system_program: Program<'info, System>,
}

pub fn handler(ctx: Context<AcceptOrder>) -> Result<()> {
    require!(
        ctx.accounts.descro_program.key() == descro::id(),
        SolistingError::InvalidDescroProgram
    );

    descro::cpi::seller_confirm(
        CpiContext::new(
            ctx.accounts.descro_program.to_account_info(),
            descro::cpi::accounts::SellerConfirm {
                seller: ctx.accounts.seller.to_account_info(),
                resolver: ctx.accounts.resolver.to_account_info(),
                escrow_account: ctx.accounts.escrow_account.to_account_info(),
                resolver_entry: ctx.accounts.resolver_entry.to_account_info(),
            },
        ),
    )?;

    let listing = &mut ctx.accounts.listing_account;
    listing.quantity_reserved = listing.quantity_reserved.saturating_sub(1);
    listing.quantity = listing.quantity.saturating_sub(1);

    Ok(())
}

Step 3: Run test

cargo build-sbf --manifest-path programs/solisting/Cargo.toml
cargo test --manifest-path programs/solisting/Cargo.toml --test test_orders -- seller_accept 2>&1 | tail -10

Expected: PASS.

Step 4: Commit

git add programs/solisting/src/instructions/accept_order.rs programs/solisting/tests/
git commit -m "feat(solisting): implement accept_order"

Task 6: `reject_order` and `cancel_order` — Defensive CPI to `descro.cancel`

Both instructions read descro escrow state before cancelling. If the escrow is already resolved (buyer cancelled directly on descro), the CPI is skipped and the OrderAccount is still closed.

Files: reject_order.rs, cancel_order.rs

Step 1: Write failing tests

#[test]
fn seller_can_reject_order() {
    let (mut svm, seller, buyer) = setup();
    let listing_id = 20u64;
    let price = 100_000_000u64;
    send(&mut svm, &[ix_create_listing(&seller.pubkey(), listing_id, Currency::Sol, price, None, vec![], vec![], 5, "".to_string())], &[&seller]);
    send(&mut svm, &[ix_create_order(&buyer.pubkey(), &seller.pubkey(), listing_id, 1, Currency::Sol, 0, None, None)], &[&buyer]);

    let buyer_before = svm.get_account(&buyer.pubkey()).map(|a| a.lamports).unwrap_or(0);
    let listing_key = listing_pda(&seller.pubkey(), listing_id);
    let order = read_order(&svm, listing_key, buyer.pubkey(), 1);

    send(&mut svm, &[ix_reject_order(&seller.pubkey(), listing_id, buyer.pubkey(), 1, order.escrow_id)], &[&seller]);

    let buyer_after = svm.get_account(&buyer.pubkey()).map(|a| a.lamports).unwrap_or(0);
    assert!(buyer_after >= buyer_before + price - 10_000); // roughly refunded
    assert_eq!(read_listing(&svm, &seller.pubkey(), listing_id).quantity_reserved, 0);
    assert!(svm.get_account(&order_pda(listing_key, buyer.pubkey(), 1)).is_none());
}

#[test]
fn buyer_can_cancel_order() {
    let (mut svm, seller, buyer) = setup();
    let listing_id = 21u64;
    send(&mut svm, &[ix_create_listing(&seller.pubkey(), listing_id, Currency::Sol, 100_000_000, None, vec![], vec![], 5, "".to_string())], &[&seller]);
    send(&mut svm, &[ix_create_order(&buyer.pubkey(), &seller.pubkey(), listing_id, 1, Currency::Sol, 0, None, None)], &[&buyer]);

    let listing_key = listing_pda(&seller.pubkey(), listing_id);
    let order = read_order(&svm, listing_key, buyer.pubkey(), 1);
    send(&mut svm, &[ix_cancel_order(&buyer.pubkey(), listing_id, &seller.pubkey(), 1, order.escrow_id)], &[&buyer]);

    assert_eq!(read_listing(&svm, &seller.pubkey(), listing_id).quantity_reserved, 0);
}

#[test]
fn reject_handles_already_cancelled_escrow() {
    // Buyer cancels directly on descro, then seller calls reject_order — must not panic
    let (mut svm, seller, buyer) = setup();
    let listing_id = 22u64;
    send(&mut svm, &[ix_create_listing(&seller.pubkey(), listing_id, Currency::Sol, 100_000_000, None, vec![], vec![], 5, "".to_string())], &[&seller]);
    send(&mut svm, &[ix_create_order(&buyer.pubkey(), &seller.pubkey(), listing_id, 1, Currency::Sol, 0, None, None)], &[&buyer]);

    let listing_key = listing_pda(&seller.pubkey(), listing_id);
    let order = read_order(&svm, listing_key, buyer.pubkey(), 1);
    // Buyer cancels directly on descro (bypassing solisting)
    send(&mut svm, &[ix_descro_cancel(&buyer.pubkey(), &seller.pubkey(), order.escrow_id)], &[&buyer]);
    // Seller calls solisting reject — should succeed without CPI error
    send(&mut svm, &[ix_reject_order(&seller.pubkey(), listing_id, &buyer.pubkey(), 1, order.escrow_id)], &[&seller]);
}

Step 2: Implement reject_order.rs

use anchor_lang::prelude::*;
use crate::state::{ListingAccount, OrderAccount};
use crate::error::SolistingError;

#[derive(Accounts)]
pub struct RejectOrder<'info> {
    #[account(mut)]
    pub seller: Signer<'info>,

    /// CHECK: Buyer receives vault refund from descro.cancel
    #[account(mut)]
    pub buyer: UncheckedAccount<'info>,

    #[account(
        mut,
        seeds = [b"listing", listing_account.seller.as_ref(), &listing_account.listing_id.to_le_bytes()],
        bump = listing_account.bump,
        constraint = seller.key() == listing_account.seller @ SolistingError::Unauthorized,
    )]
    pub listing_account: Account<'info, ListingAccount>,

    #[account(
        mut,
        seeds = [b"order", order_account.listing.as_ref(), order_account.buyer.as_ref(), &order_account.order_id.to_le_bytes()],
        bump = order_account.bump,
        constraint = seller.key() == order_account.seller @ SolistingError::Unauthorized,
        constraint = buyer.key() == order_account.buyer @ SolistingError::Unauthorized,
        close = seller,
    )]
    pub order_account: Account<'info, OrderAccount>,

    /// CHECK: Descro EscrowAccount — read to check current state before CPI
    #[account(
        mut,
        seeds = [b"escrow", seller.key().as_ref(), &order_account.escrow_id.to_le_bytes()],
        bump,
        seeds::program = descro::id(),
    )]
    pub escrow_account: UncheckedAccount<'info>,

    /// CHECK: Descro vault — drained to buyer by descro.cancel
    #[account(
        mut,
        seeds = [b"vault", escrow_account.key().as_ref()],
        bump,
        seeds::program = descro::id(),
    )]
    pub vault: UncheckedAccount<'info>,

    /// CHECK: Descro program
    pub descro_program: UncheckedAccount<'info>,

    pub system_program: Program<'info, System>,
}

pub fn handler(ctx: Context<RejectOrder>) -> Result<()> {
    require!(
        ctx.accounts.descro_program.key() == descro::id(),
        SolistingError::InvalidDescroProgram
    );

    // Defensive: skip CPI if escrow already resolved (buyer cancelled directly on descro)
    if !ctx.accounts.escrow_account.data_is_empty() {
        let data = ctx.accounts.escrow_account.try_borrow_data()?;
        if let Ok(escrow) = descro::EscrowAccount::try_deserialize(&mut data.as_ref()) {
            if escrow.state == descro::EscrowState::AwaitingSellerConfirm {
                drop(data);
                descro::cpi::cancel(
                    CpiContext::new(
                        ctx.accounts.descro_program.to_account_info(),
                        descro::cpi::accounts::Cancel {
                            canceller: ctx.accounts.seller.to_account_info(),
                            buyer: ctx.accounts.buyer.to_account_info(),
                            escrow_account: ctx.accounts.escrow_account.to_account_info(),
                            vault: ctx.accounts.vault.to_account_info(),
                            system_program: ctx.accounts.system_program.to_account_info(),
                        },
                    ),
                )?;
            }
        }
    }

    ctx.accounts.listing_account.quantity_reserved =
        ctx.accounts.listing_account.quantity_reserved.saturating_sub(1);
    Ok(())
}

Step 3: Implement cancel_order.rs

Identical to reject_order.rs with three differences: buyer: Signer instead of seller: Signer, constraints check buyer == order.buyer, and CPI canceller = buyer, close = buyer.

use anchor_lang::prelude::*;
use crate::state::{ListingAccount, OrderAccount};
use crate::error::SolistingError;

#[derive(Accounts)]
pub struct CancelOrder<'info> {
    #[account(mut)]
    pub buyer: Signer<'info>,

    #[account(
        mut,
        seeds = [b"listing", listing_account.seller.as_ref(), &listing_account.listing_id.to_le_bytes()],
        bump = listing_account.bump,
    )]
    pub listing_account: Account<'info, ListingAccount>,

    #[account(
        mut,
        seeds = [b"order", order_account.listing.as_ref(), order_account.buyer.as_ref(), &order_account.order_id.to_le_bytes()],
        bump = order_account.bump,
        constraint = buyer.key() == order_account.buyer @ SolistingError::Unauthorized,
        close = buyer,
    )]
    pub order_account: Account<'info, OrderAccount>,

    /// CHECK: Descro EscrowAccount — read defensively
    #[account(
        mut,
        seeds = [b"escrow", order_account.seller.as_ref(), &order_account.escrow_id.to_le_bytes()],
        bump,
        seeds::program = descro::id(),
    )]
    pub escrow_account: UncheckedAccount<'info>,

    /// CHECK: Descro vault
    #[account(
        mut,
        seeds = [b"vault", escrow_account.key().as_ref()],
        bump,
        seeds::program = descro::id(),
    )]
    pub vault: UncheckedAccount<'info>,

    /// CHECK: Descro program
    pub descro_program: UncheckedAccount<'info>,

    pub system_program: Program<'info, System>,
}

pub fn handler(ctx: Context<CancelOrder>) -> Result<()> {
    require!(
        ctx.accounts.descro_program.key() == descro::id(),
        SolistingError::InvalidDescroProgram
    );

    if !ctx.accounts.escrow_account.data_is_empty() {
        let data = ctx.accounts.escrow_account.try_borrow_data()?;
        if let Ok(escrow) = descro::EscrowAccount::try_deserialize(&mut data.as_ref()) {
            if escrow.state == descro::EscrowState::AwaitingSellerConfirm {
                drop(data);
                descro::cpi::cancel(
                    CpiContext::new(
                        ctx.accounts.descro_program.to_account_info(),
                        descro::cpi::accounts::Cancel {
                            canceller: ctx.accounts.buyer.to_account_info(),
                            buyer: ctx.accounts.buyer.to_account_info(),
                            escrow_account: ctx.accounts.escrow_account.to_account_info(),
                            vault: ctx.accounts.vault.to_account_info(),
                            system_program: ctx.accounts.system_program.to_account_info(),
                        },
                    ),
                )?;
            }
        }
    }

    ctx.accounts.listing_account.quantity_reserved =
        ctx.accounts.listing_account.quantity_reserved.saturating_sub(1);
    Ok(())
}

Step 4: Run all order tests

cargo build-sbf --manifest-path programs/solisting/Cargo.toml
cargo test --manifest-path programs/solisting/Cargo.toml --test test_orders 2>&1 | tail -15

Expected: all pass.

Step 5: Commit

git add programs/solisting/src/instructions/reject_order.rs programs/solisting/src/instructions/cancel_order.rs programs/solisting/tests/
git commit -m "feat(solisting): implement reject_order and cancel_order with defensive escrow check"

Task 7: `close_stale_order` — Cleanup Orphaned Orders

Anyone can call this to close an OrderAccount whose descro escrow is in a terminal state. Rent goes to caller as incentive.

File: programs/solisting/src/instructions/close_stale_order.rs

Step 1: Write failing test

#[test]
fn anyone_can_close_stale_order_after_terminal_escrow() {
    let (mut svm, seller, buyer) = setup();
    let listing_id = 30u64;
    send(&mut svm, &[ix_create_listing(&seller.pubkey(), listing_id, Currency::Sol, 100_000_000, None, vec![], vec![], 5, "".to_string())], &[&seller]);
    send(&mut svm, &[ix_create_order(&buyer.pubkey(), &seller.pubkey(), listing_id, 1, Currency::Sol, 0, None, None)], &[&buyer]);

    let listing_key = listing_pda(&seller.pubkey(), listing_id);
    let order = read_order(&svm, listing_key, buyer.pubkey(), 1);
    // Buyer cancels on descro directly → escrow is Cancelled
    send(&mut svm, &[ix_descro_cancel(&buyer.pubkey(), &seller.pubkey(), order.escrow_id)], &[&buyer]);

    // A third party can now close the stale OrderAccount
    let janitor = Keypair::new();
    svm.airdrop(&janitor.pubkey(), 1_000_000).unwrap();
    let janitor_before = svm.get_account(&janitor.pubkey()).unwrap().lamports;
    send(&mut svm, &[ix_close_stale_order(&janitor.pubkey(), listing_key, buyer.pubkey(), 1, order.escrow_account)], &[&janitor]);

    assert!(svm.get_account(&order_pda(listing_key, buyer.pubkey(), 1)).is_none());
    let janitor_after = svm.get_account(&janitor.pubkey()).unwrap().lamports;
    assert!(janitor_after > janitor_before); // received rent
}

#[test]
fn close_stale_order_fails_if_escrow_still_active() {
    let (mut svm, seller, buyer) = setup();
    let listing_id = 31u64;
    send(&mut svm, &[ix_create_listing(&seller.pubkey(), listing_id, Currency::Sol, 100_000_000, None, vec![], vec![], 5, "".to_string())], &[&seller]);
    send(&mut svm, &[ix_create_order(&buyer.pubkey(), &seller.pubkey(), listing_id, 1, Currency::Sol, 0, None, None)], &[&buyer]);

    let listing_key = listing_pda(&seller.pubkey(), listing_id);
    let order = read_order(&svm, listing_key, buyer.pubkey(), 1);
    // Don't cancel — escrow is still AwaitingSellerConfirm

    let janitor = Keypair::new();
    svm.airdrop(&janitor.pubkey(), 1_000_000).unwrap();
    let result = try_send(&mut svm, &[ix_close_stale_order(&janitor.pubkey(), listing_key, buyer.pubkey(), 1, order.escrow_account)], &[&janitor]);
    assert!(result.is_err());
}

Step 2: Implement close_stale_order.rs

use anchor_lang::prelude::*;
use crate::state::OrderAccount;
use crate::error::SolistingError;

#[derive(Accounts)]
pub struct CloseStaleOrder<'info> {
    #[account(mut)]
    pub caller: Signer<'info>,

    #[account(
        mut,
        seeds = [b"order", order_account.listing.as_ref(), order_account.buyer.as_ref(), &order_account.order_id.to_le_bytes()],
        bump = order_account.bump,
        close = caller,
    )]
    pub order_account: Account<'info, OrderAccount>,

    /// CHECK: Descro EscrowAccount — must be in terminal state or closed
    pub escrow_account: UncheckedAccount<'info>,
}

pub fn handler(ctx: Context<CloseStaleOrder>) -> Result<()> {
    require!(
        ctx.accounts.escrow_account.key() == ctx.accounts.order_account.escrow_account,
        SolistingError::EscrowStateUnexpected
    );

    // Closed (zero data) escrow = already resolved = ok to clean up
    if !ctx.accounts.escrow_account.data_is_empty() {
        let data = ctx.accounts.escrow_account.try_borrow_data()?;
        if let Ok(escrow) = descro::EscrowAccount::try_deserialize(&mut data.as_ref()) {
            require!(
                escrow.state == descro::EscrowState::Cancelled
                    || escrow.state == descro::EscrowState::Complete,
                SolistingError::EscrowStateUnexpected
            );
        }
    }

    Ok(())
}

Step 3: Run tests

cargo build-sbf --manifest-path programs/solisting/Cargo.toml
cargo test --manifest-path programs/solisting/Cargo.toml --test test_orders -- close_stale 2>&1 | tail -10

Expected: PASS.

Step 4: Commit

git add programs/solisting/src/instructions/close_stale_order.rs programs/solisting/tests/
git commit -m "feat(solisting): implement close_stale_order for orphaned order cleanup"

Task 8: Wire Up `lib.rs` and `instructions.rs`, Full Build + Test

Step 1: Complete instructions.rs

#![allow(ambiguous_glob_reexports)]

pub mod accept_order;
pub mod cancel_order;
pub mod close_listing;
pub mod close_stale_order;
pub mod create_listing;
pub mod create_order;
pub mod reject_order;
pub mod update_listing;

pub use accept_order::*;
pub use cancel_order::*;
pub use close_listing::*;
pub use close_stale_order::*;
pub use create_listing::*;
pub use create_order::*;
pub use reject_order::*;
pub use update_listing::*;

Step 2: Complete lib.rs

pub mod error;
pub mod instructions;
pub mod oracle;
pub mod state;

use anchor_lang::prelude::*;
pub use error::*;
pub use instructions::*;
pub use state::*;

declare_id!("So1istingProgramID11111111111111111111111111"); // replace with: solana-keygen grind or anchor keys list

#[program]
pub mod solisting {
    use super::*;

    pub fn create_listing(ctx: Context<CreateListing>, listing_id: u64, canonical_currency: state::Currency, price: u64, canonical_oracle: Option<Pubkey>, alt_currencies: Vec<state::AltCurrencyConfig>, accepted_resolvers: Vec<Pubkey>, quantity: u32, metadata_uri: String) -> Result<()> {
        create_listing::handler(ctx, listing_id, canonical_currency, price, canonical_oracle, alt_currencies, accepted_resolvers, quantity, metadata_uri)
    }

    pub fn update_listing(ctx: Context<UpdateListing>, canonical_currency: state::Currency, price: u64, canonical_oracle: Option<Pubkey>, alt_currencies: Vec<state::AltCurrencyConfig>, accepted_resolvers: Vec<Pubkey>, quantity: u32, metadata_uri: String) -> Result<()> {
        update_listing::handler(ctx, canonical_currency, price, canonical_oracle, alt_currencies, accepted_resolvers, quantity, metadata_uri)
    }

    pub fn close_listing(ctx: Context<CloseListing>) -> Result<()> {
        close_listing::handler(ctx)
    }

    pub fn create_order(ctx: Context<CreateOrder>, order_id: u64, escrow_id: u64, resolver: Pubkey, payment_currency: state::Currency, expected_amount: u64, max_slippage_bps: u16) -> Result<()> {
        // canonical_oracle and target_oracle come from the account struct, not args
        create_order::handler(ctx, order_id, escrow_id, resolver, payment_currency, expected_amount, max_slippage_bps)
    }

    pub fn accept_order(ctx: Context<AcceptOrder>) -> Result<()> {
        accept_order::handler(ctx)
    }

    pub fn reject_order(ctx: Context<RejectOrder>) -> Result<()> {
        reject_order::handler(ctx)
    }

    pub fn cancel_order(ctx: Context<CancelOrder>) -> Result<()> {
        cancel_order::handler(ctx)
    }

    pub fn close_stale_order(ctx: Context<CloseStaleOrder>) -> Result<()> {
        close_stale_order::handler(ctx)
    }
}

Step 3: Build all three programs

cargo build-sbf --manifest-path programs/descro_ext_resolvers/Cargo.toml && \
cargo build-sbf --manifest-path programs/descro/Cargo.toml && \
cargo build-sbf --manifest-path programs/solisting/Cargo.toml

Expected: all three compile to .so without errors.

Step 4: Run full test suite

cargo test --manifest-path programs/descro_ext_resolvers/Cargo.toml 2>&1 | tail -5
cargo test --manifest-path programs/descro/Cargo.toml 2>&1 | tail -5
cargo test --manifest-path programs/solisting/Cargo.toml 2>&1 | tail -5

Expected: all green.

Step 5: Final commit

git add programs/solisting/ Cargo.toml Cargo.lock
git commit -m "feat(solisting): complete listing + order flow with canonical price model and oracle conversion"

Done

Full buyer-to-escrow flow across three programs:

solisting = coordination and discovery; single canonical price per listing; oracle-based alt-currency conversion at order time; never holds vault funds
descro = sole custodian of SOL vault; enforces AcceptancePolicy
descro_ext_resolvers = resolver registry; read by descro at seller_confirm time

Remaining items for future phases:

Implement descro_spl program → remove SplNotImplemented guard in create_order
Oracle LiteSVM mock: build a mock Pyth account data layout for test_orders.rs oracle path tests
Event emission (emit!()) for off-chain indexers
Guard against closing listing while pending orders exist (quantity_reserved > 0)
close_stale_order should also restore quantity_reserved on the listing (requires listing account to be passed in)

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