DefiTuna AMM Smart Contract — Anchor Implementation Guide

TL;DR

DefiTuna AMM combines concentrated liquidity, on-chain limit orders, and leveraged liquidity provision in a unique AMM design. This article focuses on the Anchor smart contract that implements this protocol, specifically examining:

• Program Architecture: A hybrid AMM with integrated limit order book, implemented as a multi-instruction Anchor program
• Key Instructions: initialize_pool, create_position, place_limit_order, swap, leverage_position
• Account Structure: Complex PDA hierarchies for pools, positions, orders, and leveraged positions with proper rent management
• Mathematical Core: Concentrated liquidity calculations with leverage multipliers
• Security Patterns: Comprehensive validation, owner controls, and reentrancy protection through Solana's native constraints

Introduction

DefiTuna AMM represents an innovative approach to decentralized exchanges by integrating traditional AMM mechanics with orderbook-style limit orders and leverage capabilities. This Anchor smart contract implements the core on-chain logic that makes this possible, providing developers with a practical example of advanced Solana DeFi programming patterns.

The program follows a modular architecture with separate handlers for pool management, position creation, order placement, and swap execution. All state is managed through PDAs to ensure secure ownership and access control.

Architecture Diagrams

Account Relationships

Instruction Flow for Limit Order Execution

Account Structure

Account	Type	PDA Seeds	Purpose
Pool	State	["pool", base_mint, quote_mint]	Stores pool configuration and global state
Position	State	["position", pool, owner, position_id]	Tracks user's concentrated liquidity position
LimitOrder	State	["order", pool, owner, order_id]	Stores limit order parameters and status
LeveragedPosition	State	["leverage", pool, owner, leverage_id]	Manages leveraged liquidity positions
ProtocolConfig	State	["config"]	Global protocol parameters and fee accounts
Tick	State	["tick", pool, tick_index]	Stores liquidity data for specific price ticks

PDA Derivation Example

#[account]
#[derive(InitSpace)]
pub struct Pool {
    pub base_mint: Pubkey,
    pub quote_mint: Pubkey,
    pub fee_rate: u16, // basis points
    pub protocol_fee_rate: u16,
    pub tick_spacing: i32,
    pub current_tick_index: i32,
    pub liquidity: u128,
    pub sqrt_price: u128,
    pub fee_growth_global_0: u128,
    pub fee_growth_global_1: u128,
    pub protocol_fees_0: u64,
    pub protocol_fees_1: u64,
    pub bump: u8,
}

// PDA derivation for pool
let (pool_pda, pool_bump) = Pubkey::find_program_address(
    &[
        b"pool",
        base_mint.as_ref(),
        quote_mint.as_ref(),
    ],
    program_id
);

## Instruction Handlers Deep Dive

### 1. `initialize_pool` - Pool Creation

This instruction creates a new liquidity pool with specified parameters:

```rust
#[derive(Accounts)]
pub struct InitializePool<'info> {
    #[account(mut)]
    pub payer: Signer<'info>,
    
    #[account(
        init,
        payer = payer,
        space = 8 + Pool::INIT_SPACE,
        seeds = [
            b"pool",
            base_mint.key().as_ref(),
            quote_mint.key().as_ref()
        ],
        bump
    )]
    pub pool: Account<'info, Pool>,
    
    pub base_mint: Account<'info, Mint>,
    pub quote_mint: Account<'info, Mint>,
    
    pub system_program: Program<'info, System>,
}

pub fn initialize_pool(
    ctx: Context<InitializePool>,
    fee_rate: u16,
    tick_spacing: i32,
    initial_sqrt_price: u128,
) -> Result<()> {
    let pool = &mut ctx.accounts.pool;
    
    // Validate parameters
    require!(fee_rate <= MAX_FEE_RATE, ErrorCode::InvalidFeeRate);
    require!(tick_spacing > 0, ErrorCode::InvalidTickSpacing);
    
    // Initialize pool state
    pool.base_mint = ctx.accounts.base_mint.key();
    pool.quote_mint = ctx.accounts.quote_mint.key();
    pool.fee_rate = fee_rate;
    pool.tick_spacing = tick_spacing;
    pool.sqrt_price = initial_sqrt_price;
    pool.current_tick_index = calculate_tick_from_sqrt_price(initial_sqrt_price);
    pool.bump = ctx.bumps.pool;
    
    Ok(())
}

### 2. `create_position` - Concentrated Liquidity Position

Creates a position with liquidity concentrated between specified ticks:

```rust
#[derive(Accounts)]
#[instruction(position_id: u64)]
pub struct CreatePosition<'info> {
    #[account(mut)]
    pub owner: Signer<'info>,
    
    #[account(
        seeds = [
            b"pool",
            pool.base_mint.as_ref(),
            pool.quote_mint.as_ref()
        ],
        bump = pool.bump
    )]
    pub pool: Account<'info, Pool>,
    
    #[account(
        init,
        payer = owner,
        space = 8 + Position::INIT_SPACE,
        seeds = [
            b"position",
            pool.key().as_ref(),
            owner.key().as_ref(),
            &position_id.to_le_bytes()
        ],
        bump
    )]
    pub position: Account<'info, Position>,
    
    #[account(mut)]
    pub token_account_a: Account<'info, TokenAccount>,
    #[account(mut)]
    pub token_account_b: Account<'info, TokenAccount>,
    
    pub token_program: Program<'info, Token>,
    pub system_program: Program<'info, System>,
}

#[account]
#[derive(InitSpace)]
pub struct Position {
    pub pool: Pubkey,
    pub owner: Pubkey,
    pub liquidity: u128,
    pub tick_lower: i32,
    pub tick_upper: i32,
    pub fee_growth_inside_0_last: u128,
    pub fee_growth_inside_1_last: u128,
    pub tokens_owed_0: u64,
    pub tokens_owed_1: u64,
    pub bump: u8,
}

pub fn create_position(
    ctx: Context<CreatePosition>,
    position_id: u64,
    tick_lower: i32,
    tick_upper: i32,
    liquidity_delta: u128,
) -> Result<()> {
    let pool = &mut ctx.accounts.pool;
    let position = &mut ctx.accounts.position;
    
    // Validate tick bounds
    require!(tick_lower < tick_upper, ErrorCode::InvalidTickRange);
    require!(tick_lower % pool.tick_spacing == 0, ErrorCode::TickNotSpaced);
    require!(tick_upper % pool.tick_spacing == 0, ErrorCode::TickNotSpaced);
    
    // Calculate required token amounts
    let (amount_a, amount_b) = calculate_liquidity_amounts(
        pool.sqrt_price,
        tick_lower,
        tick_upper,
        liquidity_delta
    );
    
    // Transfer tokens from user
    transfer_tokens_in(
        &ctx.accounts.token_account_a,
        &ctx.accounts.token_account_b,
        amount_a,
        amount_b,
        &ctx.accounts.token_program,
        &ctx.accounts.owner
    )?;
    
    // Update position state
    position.pool = ctx.accounts.pool.key();
    position.owner = ctx.accounts.owner.key();
    position.liquidity = liquidity_delta;
    position.tick_lower = tick_lower;
    position.tick_upper = tick_upper;
    position.bump = ctx.bumps.position;
    
    // Update pool liquidity
    update_ticks_liquidity(pool, tick_lower, tick_upper, liquidity_delta, true)?;
    
    Ok(())
}

### 3. `place_limit_order` - Orderbook Integration

Creates a limit order that sits on the order book until matched:

```rust
#[derive(Accounts)]
#[instruction(order_id: u64)]
pub struct PlaceLimitOrder<'info> {
    #[account(mut)]
    pub owner: Signer<'info>,
    
    #[account(
        seeds = [
            b"pool",
            pool.base_mint.as_ref(),
            pool.quote_mint.as_ref()
        ],
        bump = pool.bump
    )]
    pub pool: Account<'info, Pool>,
    
    #[account(
        init,
        payer = owner,
        space = 8 + LimitOrder::INIT_SPACE,
        seeds = [
            b"order",
            pool.key().as_ref(),
            owner.key().as_ref(),
            &order_id.to_le_bytes()
        ],
        bump
    )]
    pub order: Account<'info, LimitOrder>,
    
    #[account(
        mut,
        token::mint = pool.base_mint,
        token::authority = owner
    )]
    pub user_token_account: Account<'info, TokenAccount>,
    
    #[account(
        init,
        payer = owner,
        token::mint = pool.base_mint,
        token::authority = order,
        seeds = [
            b"order_vault",
            order.key().as_ref()
        ],
        bump
    )]
    pub order_vault: Account<'info, TokenAccount>,
    
    pub token_program: Program<'info, Token>,
    pub system_program: Program<'info, System>,
}

#[account]
#[derive(InitSpace)]
pub struct LimitOrder {
    pub pool: Pubkey,
    pub owner: Pubkey,
    pub order_id: u64,
    pub tick: i32,
    pub amount: u64,
    pub is_bid: bool,
    pub filled_amount: u64,
    pub status: OrderStatus,
    pub bump: u8,
}

pub fn place_limit_order(
    ctx: Context<PlaceLimitOrder>,
    order_id: u64,
    tick: i32,
    amount: u64,
    is_bid: bool,
) -> Result<()> {
    let order = &mut ctx.accounts.order;
    
    // Validate tick alignment
    let pool = &ctx.accounts.pool;
    require!(tick % pool.tick_spacing == 0, ErrorCode::TickNotSpaced);
    
    // Transfer tokens to order vault
    let transfer_ctx = CpiContext::new(
        ctx.accounts.token_program.to_account_info(),
        Transfer {
            from: ctx.accounts.user_token_account.to_account_info(),
            to: ctx.accounts.order_vault.to_account_info(),
            authority: ctx.accounts.owner.to_account_info(),
        }
    );
    
    transfer(transfer_ctx, amount)?;
    
    // Initialize order
    order.pool = ctx.accounts.pool.key();
    order.owner = ctx.accounts.owner.key();
    order.order_id = order_id;
    order.tick = tick;
    order.amount = amount;
    order.is_bid = is_bid;
    order.filled_amount = 0;
    order.status = OrderStatus::Open;
    order.bump = ctx.bumps.order;
    
    // Emit order placed event
    emit!(OrderPlaced {
        pool: ctx.accounts.pool.key(),
        owner: ctx.accounts.owner.key(),
        order_id,
        tick,
        amount,
        is_bid,
        timestamp: Clock::get()?.unix_timestamp,
    });
    
    Ok(())
}

### 4. `swap` - Execution with Order Matching

Executes a swap, potentially matching against limit orders:

```rust
pub fn swap(
    ctx: Context<Swap>,
    amount: u64,
    sqrt_price_limit: u128,
    is_exact_input: bool,
) -> Result<()> {
    let pool = &mut ctx.accounts.pool;
    
    // Calculate swap amounts
    let (amount_in, amount_out, sqrt_price_new, liquidity) =
        compute_swap_step(
            pool.sqrt_price,
            sqrt_price_limit,
            pool.liquidity,
            amount,
            pool.fee_rate,
            is_exact_input
        )?;
    
    // Check against limit orders in this tick range
    let matched_orders = find_matching_orders(
        pool,
        pool.current_tick_index,
        get_tick_from_sqrt_price(sqrt_price_new),
        !is_exact_input // opposite side of trade
    );
    
    let mut total_matched = 0;
    for order_info in matched_orders {
        let order_account = &ctx.remaining_accounts[order_info.index];
        let mut order = Account::<LimitOrder>::try_from(order_account)?;
        
        let match_amount = min(order.amount - order.filled_amount, amount_out - total_matched);
        
        // Execute against limit order
        execute_against_limit_order(
            &mut order,
            match_amount,
            &ctx.accounts.token_program,
            &ctx.accounts.user_token_account,
            &ctx.accounts.order_vaults[order_info.vault_index]
        )?;
        
        total_matched += match_amount;
        if total_matched >= amount_out {
            break;
        }
    }
    
    // Update pool state
    pool.sqrt_price = sqrt_price_new;
    pool.liquidity = liquidity;
    
    // Apply fees
    let protocol_fee = amount_in
        .checked_mul(pool.protocol_fee_rate as u64)
        .unwrap()
        .checked_div(10_000)
        .unwrap();
    
    if is_exact_input {
        pool.protocol_fees_0 = pool.protocol_fees_0
            .checked_add(protocol_fee)
            .unwrap();
    } else {
        pool.protocol_fees_1 = pool.protocol_fees_1
            .checked_add(protocol_fee)
            .unwrap();
    }
    
    Ok(())
}

### 5. `leverage_position` - Leveraged Liquidity

Enables leveraged liquidity provision with up to 5x multiplier:

```rust
pub fn leverage_position(
    ctx: Context<LeveragePosition>,
    leverage_id: u64,
    position_key: Pubkey,
    leverage_multiplier: u8,
    collateral_amount: u64,
) -> Result<()> {
    require!(leverage_multiplier >= 1, ErrorCode::InvalidLeverage);
    require!(leverage_multiplier <= MAX_LEVERAGE, ErrorCode::ExceedsMaxLeverage);
    
    let position = &ctx.accounts.position;
    let leveraged_position = &mut ctx.accounts.leveraged_position;
    
    // Calculate borrowed amounts
    let total_liquidity_value = calculate_position_value(position, ctx.accounts.pool.sqrt_price);
    let collateral_value = calculate_token_value(collateral_amount, ctx.accounts.pool.sqrt_price);
    
    let max_borrow_value = collateral_value
        .checked_mul(leverage_multiplier as u64)
        .unwrap()
        .checked_sub(collateral_value)
        .unwrap();
    
    // Create leveraged position
    leveraged_position.position = position_key;
    leveraged_position.owner = ctx.accounts.owner.key();
    leveraged_position.leverage_multiplier = leverage_multiplier;
    leveraged_position.collateral_amount = collateral_amount;
    leveraged_position.borrowed_amount_0 = calculate_borrow_amount_0(total_liquidity_value, max_borrow_value);
    leveraged_position.borrowed_amount_1 = calculate_borrow_amount_1(total_liquidity_value, max_borrow_value);
    leveraged_position.bump = ctx.bumps.leveraged_position;
    
    // Health check: ensure position remains safe
    let health_ratio = calculate_health_ratio(leveraged_position, ctx.accounts.pool.sqrt_price);
    require!(health_ratio > MIN_HEALTH_RATIO, ErrorCode::InsufficientCollateral);
    
    Ok(())
}

## Mathematical Formulas

### Concentrated Liquidity Calculations

The amount of token X and Y required for a liquidity position between ticks $t_L$ and $t_U$ is given by:

$$
\Delta x = \Delta L \cdot \left( \frac{1}{\sqrt{P}} - \frac{1}{\sqrt{P_U}} \right)
$$

$$
\Delta y = \Delta L \cdot \left( \sqrt{P} - \sqrt{P_L} \right)
$$

Where:
- $\Delta L$ is the liquidity delta
- $\sqrt{P}$ is the current square root price
- $\sqrt{P_L}, \sqrt{P_U}$ are square root prices at lower and upper ticks

### Swap Computation

For a swap with fee $f$ (in basis points):

Effective amount in after fees:

$$
\Delta x_{eff} = \Delta x \cdot \left(1 - \frac{f}{10^4}\right)
$$

Output amount:

$$
\Delta y = \frac{y \cdot \Delta x_{eff}}{x + \Delta x_{eff}}
$$

### Leverage Health Ratio

$$
\text{Health Ratio} = \frac{\text{Position Value}}{\text{Borrowed Value} \cdot \text{Liquidation Threshold}}
$$

Positions are liquidated when:

$$
\text{Health Ratio} < 1
$$

## Solana & Anchor Best Practices

### 1. Account Validation Patterns

Always validate accounts using Anchor's type system:

```rust
#[account(
    constraint = token_account.mint == pool.base_mint,
    constraint = token_account.owner == owner.key()
)]
pub token_account: Account<'info, TokenAccount>,

### 2. Compute Unit Optimization

Use iteration limits and batch processing for order matching:

```rust
const MAX_ORDERS_PER_SWAP: usize = 10;

for i in 0..min(remaining_orders.len(), MAX_ORDERS_PER_SWAP) {
    // Process order
    if compute_units_remaining() < SAFE_COMPUTE_LIMIT {
        break;
    }
}

### 3. Token-2022 Compatibility

Handle transfer fees by checking received amounts:

```rust
let balance_before = token_account.amount;
transfer(transfer_ctx, amount)?;
let balance_after = token_account.reload()?.amount;
let received_amount = balance_after.checked_sub(balance_before).unwrap();

### 4. Event Emission for Indexers

Emit structured events for easy off-chain processing:

```rust
#[event]
pub struct SwapEvent {
    pub pool: Pubkey,
    pub trader: Pubkey,
    pub amount_in: u64,
    pub amount_out: u64,
    pub sqrt_price_before: u128,
    pub sqrt_price_after: u128,
    pub liquidity: u128,
    pub timestamp: i64,
}

## Security Considerations

### 1. Access Control

All critical operations use PDA-based authority:

```rust
#[account(
    seeds = [b"config"],
    bump = config.bump,
    constraint = config.admin == admin.key()
)]
pub config: Account<'info, ProtocolConfig>,

### 2. Input Validation

Validate all user inputs with appropriate bounds:

```rust
require!(tick_lower < tick_upper, ErrorCode::InvalidTickRange);
require!(fee_rate <= MAX_FEE_RATE, ErrorCode::InvalidFeeRate);
require!(amount > 0, ErrorCode::ZeroAmount);

### 3. Arithmetic Safety

Use checked arithmetic to prevent overflows:

```rust
let total = amount_a
    .checked_add(amount_b)
    .ok_or(ErrorCode::ArithmeticOverflow)?;

### 4. Reentrancy Protection

Solana's transaction model prevents reentrancy, but validate cross-program interactions:

```rust
// Ensure token accounts belong to the expected mints
require!(
    token_account_a.mint == pool.base_mint &&
    token_account_b.mint == pool.quote_mint,
    ErrorCode::InvalidTokenAccount
);

### 5. Oracle Manipulation Protection

Use time-weighted prices for sensitive operations:

```rust
let price = calculate_time_weighted_price(
    pool.sqrt_price_history,
    Clock::get()?.unix_timestamp
);

## How to Use This Contract

### Building and Deploying

```bash
# Build the program
anchor build

# Deploy to devnet
anchor deploy --provider.cluster devnet

# Verify deployment
solana program show --programs

### Example TypeScript Client

```typescript
import * as anchor from "@coral-xyz/anchor";
import { Program } from "@coral-xyz/anchor";
import { DefiTunaAmm } from "../target/types/defi_tuna_amm";

async function createPosition() {
  const provider = anchor.AnchorProvider.env();
  anchor.setProvider(provider);
  
  const program = anchor.workspace.DefiTunaAmm as Program<DefiTunaAmm>;
  
  const [poolPda] = anchor.web3.PublicKey.findProgramAddressSync(
    [
      Buffer.from("pool"),
      baseMint.toBuffer(),
      quoteMint.toBuffer()
    ],
    program.programId
  );
  
  const positionId = new anchor.BN(Date.now());
  const [positionPda] = anchor.web3.PublicKey.findProgramAddressSync(
    [
      Buffer.from("position"),
      poolPda.toBuffer(),
      provider.wallet.publicKey.toBuffer(),
      positionId.toArrayLike(Buffer, "le", 8)
    ],
    program.programId
  );
  
  const tx = await program.methods
    .createPosition(
      positionId,
      -6000, // tick_lower
      6000,  // tick_upper
      new anchor.BN(1000000) // liquidity
    )
    .accounts({
      pool: poolPda,
      position: positionPda,
      owner: provider.wallet.publicKey,
      tokenAccountA: tokenAccountA,
      tokenAccountB: tokenAccountB,
    })
    .rpc();
    
  console.log("Transaction signature:", tx);
}

### Required Pre-Instructions

For complex operations like leveraged positions, you may need to:

1. Create associated token accounts
2. Approve token transfers
3. Initialize required PDAs
4. Fund accounts with minimum rent

## Extending the Contract

### Adding New Instructions

1. Define new account structs in `#[derive(Accounts)]`
2. Implement handler function with proper validation
3. Add to the `lib.rs` module exports
4. Update IDL generation

### Customization Points

- **Fee Models**: Modify `compute_swap_step` for dynamic fees
- **Order Types**: Extend `LimitOrder` for different order types (FOK, IOC)
- **Leverage Models**: Add new collateral types or liquidation mechanisms
- **Oracle Integration**: Incorporate Pyth or Switchboard for price feeds

### Testing Strategies

```rust
#[tokio::test]
async fn test_swap_with_limit_order_match() {
    let mut test = ProgramTest::new(
        "defi_tuna_amm",
        id(),
        processor!(processor::Processor::process)
    );
    
    // Add accounts and mints
    test.add_account(mint_pubkey, mint_account);
    
    let (mut banks_client, payer, recent_blockhash) = test.start().await;
    
    // Create and place limit order
    let place_order_ix = Instruction {
        program_id: id(),
        accounts: place_order_accounts,
        data: place_order_data,
    };
    
    // Execute swap that should match
    let swap_ix = Instruction {
        program_id: id(),
        accounts: swap_accounts,
        data: swap_data,
    };
    
    let transaction = Transaction::new_signed_with_payer(
        &[place_order_ix, swap_ix],
        Some(&payer.pubkey()),
        &[&payer],
        recent_blockhash
    );
    
    banks_client.process_transaction(transaction).await.unwrap();
}

## Conclusion

The DefiTuna AMM smart contract demonstrates advanced Anchor patterns for building sophisticated DeFi protocols on Solana. By combining concentrated liquidity, limit orders, and leverage in a single program, it showcases how to manage complex state relationships while maintaining security and efficiency.

Key takeaways for developers:
1. Use PDA hierarchies for secure ownership and access control
2. Implement mathematical operations with overflow protection
3. Design for composability with other Solana programs
4. Emit comprehensive events for off-chain indexing
5. Optimize for compute units in iteration-heavy operations

This contract serves as a foundation for building next-generation AMMs that bridge the gap between traditional order books and automated market makers.