# 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:
> 1. `2026-05-19-descro-buyer-flow.md` — adds `buyer_create_escrow`, `seller_confirm`, and symmetric `cancel` to descro
> 2. `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` + `canonical_amount`) as the sole source of truth. Alternative currencies (`alt_currencies`) are always converted from canonical at `create_order` time via an on-chain Pyth oracle — no independent price per currency, no arbitrage possible. The oracle account is only required when `alt_currencies` is non-empty.
- `OrderAccount` records the bilateral consent: which currency the buyer chose, the oracle-computed amount, and a pointer to the descro escrow.
- Four seller archetypes: (1) SOL-only, (2) SOL-primary + USDT via oracle, (3) USDT-only, (4) USDT-primary + SOL via oracle.
- `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-sdk-solana` 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-sdk-solana) |
| Create | `programs/solisting/src/lib.rs` | Program entrypoints + declare_id! |
| Create | `programs/solisting/src/state.rs` | `ListingAccount`, `OrderAccount`, `Currency` enum |
| Create | `programs/solisting/src/error.rs` | `SolistingError` enum |
| Create | `programs/solisting/src/oracle.rs` | Pyth price read + SOL↔stablecoin 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`**

```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.
# Verify latest compatible version at https://crates.io/crates/pyth-sdk-solana
pyth-sdk-solana = "0.10"

[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**

```bash
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**

```bash
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`**

```rust
use anchor_lang::prelude::*;

/// Payment currency identifier. Amounts are always in the currency's smallest unit:
/// Sol → Lamports (u64), Spl → token units defined by the mint's decimals field.
#[derive(AnchorSerialize, AnchorDeserialize, Clone, InitSpace, Debug, PartialEq)]
pub enum Currency {
    Sol,
    Spl { mint: 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 canonical_amount: u64,
    /// Other currencies the seller accepts. Amounts are always oracle-computed at create_order
    /// time — never stored independently. Empty = oracle never needed.
    #[max_len(3)]
    pub alt_currencies: Vec<Currency>,
    /// Pyth Price Feed account. Must be Some when alt_currencies is non-empty.
    /// The seller chooses which oracle they trust.
    pub price_oracle: Option<Pubkey>,
    /// 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 canonical_amount 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`**

```rust
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("alt_currencies is non-empty but price_oracle is None on the listing")]
    OracleRequired,
    #[msg("Oracle account key does not match listing.price_oracle")]
    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 reads a Pyth SOL/USD price feed and converts between SOL (Lamports) and a
stablecoin (6-decimal SPL token, e.g. USDT/USDC). Stablecoins are treated as exactly $1.00 —
no second feed needed for the stable side.

```rust
use anchor_lang::prelude::*;
use pyth_sdk_solana::load_price_feed_from_account_info;
use crate::error::SolistingError;
use crate::state::Currency;

/// Maximum age of the oracle price in seconds before it is considered stale.
const ORACLE_MAX_AGE_SECS: u64 = 60;

/// Reads the Pyth SOL/USD price feed and returns (price_i64, exponent_i32).
/// price_i64 * 10^exponent = USD per SOL.
/// Returns OraclePriceUnavailable if the price is stale or the feed account is invalid.
fn sol_usd_price(oracle_account: &AccountInfo) -> Result<(i64, i32)> {
    let feed = load_price_feed_from_account_info(oracle_account)
        .map_err(|_| error!(SolistingError::OraclePriceUnavailable))?;
    let now = Clock::get()?.unix_timestamp;
    let price = feed
        .get_price_no_older_than(now, ORACLE_MAX_AGE_SECS)
        .ok_or(error!(SolistingError::OraclePriceUnavailable))?;
    Ok((price.price, price.expo))
}

/// Converts `canonical_amount` (in `canonical_currency`) to `target_currency` units.
///
/// Supported conversions:
///   Sol → Spl (stablecoin 6 decimals): lamports → token_units
///   Spl (stablecoin 6 decimals) → Sol: token_units → lamports
///
/// Formula Sol → Spl (assuming 1 stablecoin = $1, 6 decimals):
///   stablecoin_units = lamports * price * 10^expo / 10^9 * 10^6
///                    = lamports * price * 10^(expo + 6 - 9)
///                    = lamports * price * 10^(expo - 3)
///   With expo=-8: stablecoin_units = lamports * price / 10^11
///
/// Uses u128 intermediate to avoid overflow (max ~1.8e19 in u64 is too small).
///
/// Slippage check: if the oracle-computed amount differs from `expected_amount` by more than
/// `max_slippage_bps` basis points, returns SlippageExceeded.
pub fn convert_with_slippage(
    oracle_account: &AccountInfo,
    canonical_currency: &Currency,
    canonical_amount: u64,
    target_currency: &Currency,
    expected_amount: u64,
    max_slippage_bps: u16,
) -> Result<u64> {
    let (price_raw, expo) = sol_usd_price(oracle_account)?;
    require!(price_raw > 0, SolistingError::OraclePriceUnavailable);

    let computed = match (canonical_currency, target_currency) {
        (Currency::Sol, Currency::Spl { .. }) => {
            // lamports → stablecoin units (6 decimals, $1 peg)
            // = lamports * price_raw / 10^(9 - 6 + (-expo))
            // = lamports * price_raw / 10^(3 - expo)   [expo is negative, so 3 - expo > 3]
            let shift: u32 = (3i32 - expo) as u32; // expo=-8 → shift=11
            let intermediate = (canonical_amount as u128)
                .checked_mul(price_raw as u128)
                .ok_or(error!(SolistingError::OraclePriceUnavailable))?;
            let divisor = 10u128.pow(shift);
            u64::try_from(intermediate / divisor)
                .map_err(|_| error!(SolistingError::OraclePriceUnavailable))?
        }
        (Currency::Spl { .. }, Currency::Sol) => {
            // stablecoin units (6 decimals, $1 peg) → lamports
            // = token_units * 10^9 / (price_raw * 10^expo)
            // = token_units * 10^9 / price_raw * 10^(-expo)
            // = token_units * 10^(9 + (-expo)) / price_raw
            // = token_units * 10^(9 - expo) / price_raw  [expo negative, so 9 - expo > 9]
            // Example expo=-8: = token_units * 10^17 / price_raw
            // Then divide out the stablecoin decimals (6):
            // = token_units * 10^(9 - expo - 6) / price_raw = token_units * 10^(3 - expo) / price_raw
            let shift: u32 = (3i32 - expo) as u32; // expo=-8 → shift=11
            let numerator = (canonical_amount as u128)
                .checked_mul(10u128.pow(shift))
                .ok_or(error!(SolistingError::OraclePriceUnavailable))?;
            u64::try_from(numerator / price_raw as u128)
                .map_err(|_| error!(SolistingError::OraclePriceUnavailable))?
        }
        _ => return Err(error!(SolistingError::OraclePriceUnavailable)),
    };

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

    Ok(computed)
}
```

- [ ] **Step 4: Verify `state.rs` compiles in isolation (no instruction files yet)**

```bash
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**

```bash
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`**

```rust
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,
        vec![],         // no alt_currencies
        None,           // no oracle
        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.canonical_amount, price);
    assert_eq!(listing.alt_currencies.len(), 0);
    assert_eq!(listing.price_oracle, None);
    assert_eq!(listing.quantity, 10);
    assert_eq!(listing.quantity_reserved, 0);
    assert!(listing.is_active);
}

#[test]
fn create_listing_with_alt_currency_requires_oracle() {
    // alt_currencies non-empty but price_oracle = None → should fail
    let (mut svm, seller, _) = setup();
    let usdt_mint = Pubkey::new_unique();
    let ix = ix_create_listing(
        &seller.pubkey(),
        42,
        Currency::Sol,
        1_000_000_000,
        vec![Currency::Spl { mint: usdt_mint }],
        None, // oracle missing — must fail
        vec![],
        5,
        "ipfs://x".to_string(),
    );
    let result = try_send(&mut svm, &[ix], &[&seller]);
    assert!(result.is_err());
}

#[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, vec![], None, 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,
        vec![],
        None,
        vec![],
        20,
        "ipfs://new".to_string(),
    );
    send(&mut svm, &[ix_update], &[&seller]);

    let listing = read_listing(&svm, &seller.pubkey(), listing_id);
    assert_eq!(listing.canonical_amount, 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, vec![], None, 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)**

```bash
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`**

```rust
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,
    canonical_amount: u64,
    alt_currencies: Vec<Currency>,
    price_oracle: Option<Pubkey>,
    accepted_resolvers: Vec<Pubkey>,
    quantity: u32,
    metadata_uri: String,
) -> Result<()> {
    require!(
        alt_currencies.is_empty() || price_oracle.is_some(),
        SolistingError::OracleRequired
    );

    let listing = &mut ctx.accounts.listing_account;
    listing.seller = ctx.accounts.seller.key();
    listing.canonical_currency = canonical_currency;
    listing.canonical_amount = canonical_amount;
    listing.alt_currencies = alt_currencies;
    listing.price_oracle = price_oracle;
    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`**

```rust
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,
    canonical_amount: u64,
    alt_currencies: Vec<Currency>,
    price_oracle: Option<Pubkey>,
    accepted_resolvers: Vec<Pubkey>,
    quantity: u32,
    metadata_uri: String,
) -> Result<()> {
    require!(
        alt_currencies.is_empty() || price_oracle.is_some(),
        SolistingError::OracleRequired
    );

    let listing = &mut ctx.accounts.listing_account;
    listing.canonical_currency = canonical_currency;
    listing.canonical_amount = canonical_amount;
    listing.alt_currencies = alt_currencies;
    listing.price_oracle = price_oracle;
    listing.accepted_resolvers = accepted_resolvers;
    listing.quantity = quantity;
    listing.metadata_uri = metadata_uri;
    Ok(())
}
```

- [ ] **Step 5: Write `close_listing.rs`**

```rust
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)**

```rust
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,
    canonical_amount: u64,
    alt_currencies: Vec<Currency>,
    price_oracle: Option<Pubkey>,
    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,
    canonical_amount: u64,
    alt_currencies: Vec<Currency>,
    price_oracle: Option<Pubkey>,
    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`:
```rust
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):
```rust
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,
        canonical_amount: u64,
        alt_currencies: Vec<state::Currency>,
        price_oracle: Option<Pubkey>,
        accepted_resolvers: Vec<Pubkey>,
        quantity: u32,
        metadata_uri: String,
    ) -> Result<()> {
        create_listing::handler(
            ctx, listing_id, canonical_currency, canonical_amount,
            alt_currencies, price_oracle, accepted_resolvers, quantity, metadata_uri,
        )
    }

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

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

- [ ] **Step 8: Build and run listing tests**

```bash
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**

```bash
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`**

```rust
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.canonical_amount 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, vec![], None, 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, vec![], None, 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, vec![], None, 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)], &[&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)], &[&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, vec![], None, 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 }, 0, 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, vec![], None, 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, Pubkey::new_unique(),
    )], &[&buyer]);
    assert!(result.is_err());
}
```

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

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

Expected: compile errors.

- [ ] **Step 3: Implement `create_order.rs`**

```rust
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 price feed account. Required when payment_currency != canonical_currency.
    /// Pass SystemProgram ID as a no-op placeholder when oracle is not needed.
    pub 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 {
        // No oracle needed — pay canonical amount directly
        listing.canonical_amount
    } else {
        // Must be an accepted alt_currency
        require!(
            listing.alt_currencies.contains(&payment_currency),
            SolistingError::CurrencyNotAccepted
        );
        // Oracle must be configured on listing
        let oracle_key = listing.price_oracle.ok_or(error!(SolistingError::OracleRequired))?;
        require!(
            ctx.accounts.oracle.key() == oracle_key,
            SolistingError::OracleMismatch
        );
        oracle::convert_with_slippage(
            ctx.accounts.oracle.as_ref(),
            &listing.canonical_currency,
            listing.canonical_amount,
            &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`.

```rust
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()
}

// ix_create_order: derive escrow_id from order_pda bytes[0..8], pass SystemProgram as oracle placeholder
pub fn ix_create_order(
    buyer: &Pubkey,
    seller: &Pubkey,
    listing_id: u64,
    order_id: u64,
    payment_currency: Currency,
    max_slippage_bps: u16,
    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, 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,
    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 oracle_key = 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 list")
}
```

- [ ] **Step 5: Run tests**

```bash
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**

```bash
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**

```rust
#[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, vec![], None, 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)], &[&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`**

```rust
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**

```bash
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**

```bash
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**

```rust
#[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, vec![], None, vec![], 5, "".to_string())], &[&seller]);
    send(&mut svm, &[ix_create_order(&buyer.pubkey(), &seller.pubkey(), listing_id, 1, Currency::Sol, 0, 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, vec![], None, vec![], 5, "".to_string())], &[&seller]);
    send(&mut svm, &[ix_create_order(&buyer.pubkey(), &seller.pubkey(), listing_id, 1, Currency::Sol, 0, 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, vec![], None, vec![], 5, "".to_string())], &[&seller]);
    send(&mut svm, &[ix_create_order(&buyer.pubkey(), &seller.pubkey(), listing_id, 1, Currency::Sol, 0, 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`**

```rust
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`.

```rust
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**

```bash
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**

```bash
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**

```rust
#[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, vec![], None, vec![], 5, "".to_string())], &[&seller]);
    send(&mut svm, &[ix_create_order(&buyer.pubkey(), &seller.pubkey(), listing_id, 1, Currency::Sol, 0, 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, vec![], None, vec![], 5, "".to_string())], &[&seller]);
    send(&mut svm, &[ix_create_order(&buyer.pubkey(), &seller.pubkey(), listing_id, 1, Currency::Sol, 0, 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`**

```rust
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**

```bash
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**

```bash
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`**

```rust
#![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`**

```rust
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, canonical_amount: u64, alt_currencies: Vec<state::Currency>, price_oracle: Option<Pubkey>, accepted_resolvers: Vec<Pubkey>, quantity: u32, metadata_uri: String) -> Result<()> {
        create_listing::handler(ctx, listing_id, canonical_currency, canonical_amount, alt_currencies, price_oracle, accepted_resolvers, quantity, metadata_uri)
    }

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

```bash
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**

```bash
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**

```bash
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)