Buy Token

Purchases tokens from the bonding curve using SOL.

Instruction INDEX

2

Instruction

SCBondingCurveInstruction::BuyToken {
    pda_token_nonce: u8,
    sol_to_spend: u64,
    min_token_to_receive: u64,
    logging_account_bump: u8,
}

Parameters

Parameter	Type	Description
pda_token_nonce	u8	Nonce for the token owner PDA
sol_to_spend	u64	Amount of SOL to spend in lamports
min_token_to_receive	u64	Minimum acceptable token amount to receive (slippage protection)
logging_account_bump	u8	Bump for the logging authority PDA

Account Setup

#	Account	Description	Derivation
1	Payer account	Transaction signer (User wallet)	-
2	System program	System program	SystemProgram.programId
3	Token program	SPL Token program	TOKEN_PROGRAM_ID
4	Token owner PDA	Bonding curve account	[Buffer.from("token_owner"), mint.toBuffer(), [nonce]]
5	Token mint	Token mint address	Provided by user
6	Owner token account	Token account for PDA	getAssociatedTokenAddress(mint, ownerPDA, true)
7	User token account	User's token account	getAssociatedTokenAddress(mint, userWallet, false)
8	Fee account	Platform fee account	Fixed address (see Reference section)
9	Properties account	Platform configuration	[Buffer.from("settings")]
10	Program account	SC Bonding Curve program	SC Bonding Curve program ID
11	Log authority account	For structured logs	[Buffer.from("logging_authority")]

Function Logic

1. Verifies the PDA token owner matches the expected PDA for the token mint

2. Retrieves platform fee from properties account (currently 1%)

3. Calculates amount without fee (99% of sol_to_spend)

4. Retrieves current pool balances (virtual + real SOL and tokens)

5. Calculates expected token amount using the bonding curve formula

6. Verifies expected token amount meets minimum specified (slippage check)

7. Checks if purchase would finalize the token sale

8. If finalizing, adjusts amounts accordingly and marks the token as finalized

9. Transfers SOL to the bonding curve and fee account

10. Transfers tokens to the user

11. Updates pool balances in the bonding curve account

12. Records buy data in logs

Price Calculation

token_amount = pool_token_balance * sol_amount / (pool_sol_balance + sol_amount)

Where:

• pool_token_balance = virtual_token + real_token

• pool_sol_balance = virtual_sol + real_sol

• sol_amount = amount of SOL after fee deduction

Notes

• The platform fee is deducted from the SOL amount before calculating token amount

• If the purchase would leave less than POOL_MIGRATION_RESERVES tokens in the pool, the token sale is finalized

• A finalized token can no longer be traded on the bonding curve and is ready for migration

Example Usage

// Derive PDAs and other accounts
const [tokenOwnerPDA, pdaTokenNonce] = PublicKey.findProgramAddressSync(
  [Buffer.from("token_owner"), tokenMint.toBuffer()],
  SC_BONDING_CURVE_PROGRAM_ID
)

const [propertiesAccount] = PublicKey.findProgramAddressSync(
  [Buffer.from("settings")],
  SC_BONDING_CURVE_PROGRAM_ID
)

const [logAuthority, logAuthorityBump] = PublicKey.findProgramAddressSync(
  [Buffer.from("logging_authority")],
  SC_BONDING_CURVE_PROGRAM_ID
)

// Get token accounts
const ownerTokenAccount = getAssociatedTokenAddressSync(tokenMint, tokenOwnerPDA, true)

const userTokenAccount = getAssociatedTokenAddressSync(tokenMint, wallet.publicKey, false)

// Create instruction data buffer
const data = Buffer.alloc(18)
data.writeUint8(2, 0) // Instruction code for BuyToken
data.writeUint8(pdaTokenNonce, 1) // PDA nonce
data.writeBigUInt64LE(solToSpend, 2) // SOL amount
data.writeBigUInt64LE(minTokenToReceive, 10) // Minimum tokens
data.writeUint8(logAuthorityBump, 18) // Log authority bump

const buyTokenIx = new TransactionInstruction({
  programId: SC_BONDING_CURVE_PROGRAM_ID,
  keys: [
    { pubkey: wallet.publicKey, isSigner: true, isWritable: true },
    { pubkey: SystemProgram.programId, isSigner: false, isWritable: false },
    { pubkey: TOKEN_PROGRAM_ID, isSigner: false, isWritable: false },
    { pubkey: tokenOwnerPDA, isSigner: false, isWritable: true },
    { pubkey: tokenMint, isSigner: false, isWritable: false },
    { pubkey: ownerTokenAccount, isSigner: false, isWritable: true },
    { pubkey: userTokenAccount, isSigner: false, isWritable: true },
    { pubkey: FEE_ACCOUNT, isSigner: false, isWritable: true },
    { pubkey: propertiesAccount, isSigner: false, isWritable: false },
    { pubkey: SC_BONDING_CURVE_PROGRAM_ID, isSigner: false, isWritable: false },
    { pubkey: logAuthority, isSigner: false, isWritable: false },
  ],
  data: data,
})