lez-programs/amm/src/remove.rs

use std::num::NonZeroU128;

use amm_core::{
    assert_supported_fee_tier, compute_liquidity_token_pda_seed, compute_vault_pda_seed,
    PoolDefinition, MINIMUM_LIQUIDITY,
};
use nssa_core::{
    account::{AccountWithMetadata, Data},
    program::{AccountPostState, ChainedCall},
};

#[expect(clippy::too_many_arguments, reason = "TODO: Fix later")]
pub fn remove_liquidity(
    pool: AccountWithMetadata,
    vault_a: AccountWithMetadata,
    vault_b: AccountWithMetadata,
    pool_definition_lp: AccountWithMetadata,
    user_holding_a: AccountWithMetadata,
    user_holding_b: AccountWithMetadata,
    user_holding_lp: AccountWithMetadata,
    remove_liquidity_amount: NonZeroU128,
    min_amount_to_remove_token_a: u128,
    min_amount_to_remove_token_b: u128,
) -> (Vec<AccountPostState>, Vec<ChainedCall>) {
    let remove_liquidity_amount: u128 = remove_liquidity_amount.into();

    // 1. Fetch Pool state
    let pool_def_data = PoolDefinition::try_from(&pool.account.data)
        .expect("Remove liquidity: AMM Program expects a valid Pool Definition Account");
    assert_supported_fee_tier(pool_def_data.fees);

    assert!(
        pool_def_data.liquidity_pool_supply >= MINIMUM_LIQUIDITY,
        "Pool liquidity supply is below minimum liquidity"
    );
    assert_eq!(
        pool_def_data.liquidity_pool_id, pool_definition_lp.account_id,
        "LP definition mismatch"
    );
    assert_eq!(
        vault_a.account_id, pool_def_data.vault_a_id,
        "Vault A was not provided"
    );
    assert_eq!(
        vault_b.account_id, pool_def_data.vault_b_id,
        "Vault B was not provided"
    );

    let token_program_id = vault_a.account.program_owner;
    assert_eq!(
        user_holding_a.account.program_owner, token_program_id,
        "User Token A holding must be owned by the vault's Token Program"
    );
    assert_eq!(
        user_holding_b.account.program_owner, token_program_id,
        "User Token B holding must be owned by the vault's Token Program"
    );

    // Vault addresses do not need to be checked with PDA
    // calculation for setting authorization since stored
    // in the Pool Definition.
    let mut running_vault_a = vault_a.clone();
    let mut running_vault_b = vault_b.clone();
    running_vault_a.is_authorized = true;
    running_vault_b.is_authorized = true;

    assert!(
        min_amount_to_remove_token_a != 0,
        "Minimum withdraw amount must be nonzero"
    );
    assert!(
        min_amount_to_remove_token_b != 0,
        "Minimum withdraw amount must be nonzero"
    );

    // 2. Compute withdrawal amounts
    let user_holding_lp_data = token_core::TokenHolding::try_from(&user_holding_lp.account.data)
        .expect("Remove liquidity: AMM Program expects a valid Token Account for liquidity token");
    let token_core::TokenHolding::Fungible {
        definition_id: _,
        balance: user_lp_balance,
    } = user_holding_lp_data
    else {
        panic!(
            "Remove liquidity: AMM Program expects a valid Fungible Token Holding Account for liquidity token"
        );
    };

    assert!(
        user_lp_balance <= pool_def_data.liquidity_pool_supply,
        "Invalid liquidity account provided"
    );
    assert_eq!(
        user_holding_lp_data.definition_id(),
        pool_def_data.liquidity_pool_id,
        "Invalid liquidity account provided"
    );
    // Honest flows should never reach the permanent lock through a valid remove instruction, but
    // we still reject legacy or corrupted states that are already at the locked floor.
    assert!(
        pool_def_data.liquidity_pool_supply > MINIMUM_LIQUIDITY,
        "Pool only contains locked liquidity"
    );
    assert!(
        remove_liquidity_amount <= user_lp_balance,
        "Remove amount exceeds user LP balance"
    );
    let unlocked_liquidity = pool_def_data.liquidity_pool_supply - MINIMUM_LIQUIDITY;
    // The remove instruction never sees the LP lock account directly, so we must still refuse any
    // request that would burn through the permanent floor even if ownership is already corrupted.
    assert!(
        remove_liquidity_amount <= unlocked_liquidity,
        "Cannot remove locked minimum liquidity"
    );

    let withdraw_amount_a = pool_def_data
        .reserve_a
        .checked_mul(remove_liquidity_amount)
        .expect("reserve_a * remove_liquidity_amount overflows u128")
        / pool_def_data.liquidity_pool_supply;
    let withdraw_amount_b = pool_def_data
        .reserve_b
        .checked_mul(remove_liquidity_amount)
        .expect("reserve_b * remove_liquidity_amount overflows u128")
        / pool_def_data.liquidity_pool_supply;

    // 3. Validate and slippage check
    assert!(
        withdraw_amount_a >= min_amount_to_remove_token_a,
        "Insufficient minimal withdraw amount (Token A) provided for liquidity amount"
    );
    assert!(
        withdraw_amount_b >= min_amount_to_remove_token_b,
        "Insufficient minimal withdraw amount (Token B) provided for liquidity amount"
    );

    // 4. Calculate LP to reduce cap by
    let delta_lp: u128 = remove_liquidity_amount;

    // 5. Update pool account
    let mut pool_post = pool.account.clone();
    let pool_post_definition = PoolDefinition {
        liquidity_pool_supply: pool_def_data
            .liquidity_pool_supply
            .checked_sub(delta_lp)
            .expect("liquidity_pool_supply - delta_lp underflows"),
        reserve_a: pool_def_data
            .reserve_a
            .checked_sub(withdraw_amount_a)
            .expect("reserve_a - withdraw_amount_a underflows"),
        reserve_b: pool_def_data
            .reserve_b
            .checked_sub(withdraw_amount_b)
            .expect("reserve_b - withdraw_amount_b underflows"),
        ..pool_def_data.clone()
    };

    pool_post.data = Data::from(&pool_post_definition);

    // Chaincall for Token A withdraw
    let call_token_a = ChainedCall::new(
        token_program_id,
        vec![running_vault_a, user_holding_a.clone()],
        &token_core::Instruction::Transfer {
            amount_to_transfer: withdraw_amount_a,
        },
    )
    .with_pda_seeds(vec![compute_vault_pda_seed(
        pool.account_id,
        pool_def_data.definition_token_a_id,
    )]);
    // Chaincall for Token B withdraw
    let call_token_b = ChainedCall::new(
        token_program_id,
        vec![running_vault_b, user_holding_b.clone()],
        &token_core::Instruction::Transfer {
            amount_to_transfer: withdraw_amount_b,
        },
    )
    .with_pda_seeds(vec![compute_vault_pda_seed(
        pool.account_id,
        pool_def_data.definition_token_b_id,
    )]);
    // Chaincall for LP adjustment
    let mut pool_definition_lp_auth = pool_definition_lp.clone();
    pool_definition_lp_auth.is_authorized = true;
    let call_token_lp = ChainedCall::new(
        token_program_id,
        vec![pool_definition_lp_auth, user_holding_lp.clone()],
        &token_core::Instruction::Burn {
            amount_to_burn: delta_lp,
        },
    )
    .with_pda_seeds(vec![compute_liquidity_token_pda_seed(pool.account_id)]);

    let chained_calls = vec![call_token_lp, call_token_b, call_token_a];

    let post_states = vec![
        AccountPostState::new(pool_post.clone()),
        AccountPostState::new(vault_a.account.clone()),
        AccountPostState::new(vault_b.account.clone()),
        AccountPostState::new(pool_definition_lp.account.clone()),
        AccountPostState::new(user_holding_a.account.clone()),
        AccountPostState::new(user_holding_b.account.clone()),
        AccountPostState::new(user_holding_lp.account.clone()),
    ];

    (post_states, chained_calls)
}