buy_exact_quote_in_v3

// discriminator e1f7501ed5b38488 ; handler fn_2453d -> logic fn_2835c (programs/pump/src/trade_v3.rs)
// accounts (17): 0 global, 1 base_mint, 2 quote_mint, 3 base_token_program, 4 quote_token_program,
//   5 bonding_curve (mut), 6 curve_base_ata (mut), 7 curve_quote_ata (mut, unused for SOL), 8 user (signer),
//   9 user_base_ata (mut), 10 user_quote_ata (mut), 11 user_volume_accumulator (mut), 12 fee_config (pump fees program),
//   13 buyback_fee_recipient (SOL wallet or its quote ATA, mut), 14 system_program, 15 event_authority, 16 program
pub fn buy_exact_quote_in_v3(ctx, spendable_quote_in: u64, min_tokens_out: u64, flag: Option<bool> /* byte 16: 0/1, other -> error */) {
    msg!("Instruction: BuyExactQuoteInV3");
    trade_v3_accounts_validate(ctx)?;                  // fn_1f826: PDAs, owners, mints, user_volume_accumulator init
    let curve = &mut ctx.bonding_curve;
    require!(!curve.complete ...);                     // fn_076ea / fn_0f4b6 state checks
    require!(min_tokens_out != 0, 6020);               // pc 28377
    require!(spendable_quote_in != 0, 6041);           // pc 28379
    let fee_exempt = ctx.user.key == global.fee_exempt_key;   // global +0x288, pc 283a2
    let (net, protocol_fee, creator_fee, p_bps, c_bps);
    if fee_exempt {
        net = spendable_quote_in; protocol_fee = 0; creator_fee = 0;    // pc 2845a
    } else {
        // fn_0f803 / fn_109ae: bps from FeeConfig. Market-cap tier for SOL/known quote mints
        // (mcap = v_quote*supply/v_token), flat fees otherwise. Current config: 95 / 30 in every tier.
        // If global enables it and curve.creator_fee_bps != 0 -> c_bps = curve.creator_fee_bps.
        (p_bps, c_bps) = select_fee_bps(fee_config, curve, quote_mint);
        if curve.creator == Pubkey::default() { c_bps = 0; }
        // fn_0f91f
        net = spendable_quote_in * 10_000 / (10_000 + p_bps + c_bps);          // floor
        protocol_fee = ceil(net * p_bps / 10_000);
        creator_fee  = ceil(net * c_bps / 10_000);
        if net + protocol_fee + creator_fee > spendable_quote_in {
            net -= net + protocol_fee + creator_fee - spendable_quote_in;      // fees are not recomputed
        }
        require!(net != 0, 6041);
    }
    // fn_1347e / fn_105eb  (note the -1)
    let mut tokens = (net - 1) * curve.virtual_token_reserves / (curve.virtual_quote_reserves + net - 1);
    require!(tokens != 0);                                                       // pc 283cb
    if tokens > curve.real_token_reserves {                                      // pc 2847d
        // partial fill allowed unless (curve flag +162 set or user is fee-exempt) and flag == false -> 6021
        tokens = curve.real_token_reserves;
        let q = curve.virtual_quote_reserves * tokens / (curve.virtual_token_reserves - tokens) + 1; // fn_13385
        (protocol_fee, creator_fee) = compute_trade_fees(q);                     // fn_0f803, ceil each
        let cost = q + protocol_fee + creator_fee;
        require!(cost <= spendable_quote_in, 6002);                              // pc 2855b
        net = q;
    } else {
        require!(tokens >= min_tokens_out, 6042);                                // pc 284bc slippage
    }
    // settle: fn_0fd9b
    curve.virtual_token_reserves -= tokens; curve.real_token_reserves -= tokens;  // fn_134f5
    curve.virtual_quote_reserves += net;     curve.real_quote_reserves += net;
    token::transfer_checked(curve_base_ata -> user_base_ata, tokens, signer = ["bonding-curve", base_mint]); // fn_1148a
    if user_volume_accumulator.user == default { user_volume_accumulator.user = user; }
    // fn_136f2
    let buyback = if curve.flag154 { 0 } else { protocol_fee * global.buyback_bps / 10_000 }; // 5000 bps now
    curve.accrued_protocol_fee += protocol_fee - buyback;   // curve +120, stays in the curve
    curve.accrued_creator_fee  += creator_fee;              // curve +112, stays in the curve
    let total = net + protocol_fee + creator_fee;
    // fn_1229d / fn_11ad5 / fn_1202e
    if quote_mint == WSOL {
        system_transfer(user -> bonding_curve, total - buyback);
        system_transfer(user -> buyback_fee_recipient, buyback);
    } else {
        token::transfer_checked(user_quote_ata -> curve_quote_ata, total - buyback);
        token::transfer_checked(user_quote_ata -> buyback_fee_recipient_quote_ata, buyback);
    }
    emit!(TradeEvent { mint, quote_amount: .., token_amount: tokens, is_buy: true, user, reserves.., fee_recipient,
                       fee_bps: p_bps, fee: protocol_fee, creator, creator_fee_bps: c_bps, creator_fee,
                       ix_name: "buy_exact_quote_in", .. });  // fn_10150
}