///! # 流动性池
///!
///! Liquidity Pool (AMM)
///! 提供自动做市商（AMM）机制和流动性管理
///!
///! **版本**: v1.0
///! **模块**: charter-std/defi/liquidity.ch

use utils::math::{safe_mul, safe_div, safe_add, safe_sub, sqrt};
use utils::crypto::sha3_384_hash;

// ============================================================================
// 流动性池结构
// ============================================================================

/// 流动性池
struct LiquidityPool {
    /// 池ID
    pool_id: Hash,
    
    /// 资产A
    asset_a: Address,
    
    /// 资产B
    asset_b: Address,
    
    /// 资产A储备量
    reserve_a: u256,
    
    /// 资产B储备量
    reserve_b: u256,
    
    /// LP代币总供应量
    total_lp_supply: u256,
    
    /// 手续费率（基点，例如30表示0.3%）
    fee_rate: u16,
    
    /// 累计手续费A
    accumulated_fee_a: u256,
    
    /// 累计手续费B
    accumulated_fee_b: u256,
    
    /// 最后更新时间
    last_updated: Timestamp,
    
    /// K值（恒定乘积）
    k_last: u256
}

/// 流动性提供者信息
struct LiquidityProvider {
    /// 提供者地址
    provider: Address,
    
    /// 池ID
    pool_id: Hash,
    
    /// LP代币数量
    lp_tokens: u256,
    
    /// 提供时间
    provided_at: Timestamp,
    
    /// 已领取奖励A
    claimed_reward_a: u256,
    
    /// 已领取奖励B
    claimed_reward_b: u256
}

/// 交换记录
struct SwapRecord {
    /// 交换ID
    swap_id: Hash,
    
    /// 池ID
    pool_id: Hash,
    
    /// 交换者
    swapper: Address,
    
    /// 输入资产
    asset_in: Address,
    
    /// 输入数量
    amount_in: u256,
    
    /// 输出资产
    asset_out: Address,
    
    /// 输出数量
    amount_out: u256,
    
    /// 手续费
    fee: u256,
    
    /// 时间戳
    timestamp: Timestamp
}

// ============================================================================
// 流动性事件
// ============================================================================

/// 添加流动性事件
event AddLiquidity {
    pool_id: Hash,
    provider: Address,
    amount_a: u256,
    amount_b: u256,
    lp_tokens: u256,
    timestamp: Timestamp
}

/// 移除流动性事件
event RemoveLiquidity {
    pool_id: Hash,
    provider: Address,
    amount_a: u256,
    amount_b: u256,
    lp_tokens: u256,
    timestamp: Timestamp
}

/// 交换事件
event Swap {
    swap_id: Hash,
    pool_id: Hash,
    swapper: Address,
    asset_in: Address,
    amount_in: u256,
    asset_out: Address,
    amount_out: u256,
    fee: u256,
    timestamp: Timestamp
}

/// 领取奖励事件
event ClaimRewards {
    pool_id: Hash,
    provider: Address,
    reward_a: u256,
    reward_b: u256,
    timestamp: Timestamp
}

// ============================================================================
// 流动性池协议
// ============================================================================

/// 流动性池协议
certificate LiquidityPoolProtocol {
    /// 流动性池 (pool_id => pool)
    let _pools: Map<Hash, LiquidityPool>;
    
    /// 流动性提供者 (provider => pool_id => lp_info)
    let _providers: Map<Address, Map<Hash, LiquidityProvider>>;
    
    /// 交换记录 (swap_id => record)
    let _swaps: Map<Hash, SwapRecord>;
    
    /// 池索引 (asset_a => asset_b => pool_id)
    let _pool_index: Map<Address, Map<Address, Hash>>;
    
    /// 管理员地址
    let _admin: Address;
    
    /// 默认手续费率（基点）
    let _default_fee_rate: u16;
    
    /// 最小流动性（防止除零）
    let _minimum_liquidity: u256;
    
    // ========== 构造函数 ==========
    
    constructor(fee_rate: u16) {
        require(fee_rate <= 1000, "Fee rate too high"); // 最高10%
        
        self._admin = msg.sender;
        self._default_fee_rate = fee_rate;
        self._minimum_liquidity = 1000; // 最小流动性锁定
    }
    
    // ========== 池管理 ==========
    
    /// 创建流动性池
    ///
    /// # 参数
    /// - `asset_a`: 资产A地址
    /// - `asset_b`: 资产B地址
    /// - `initial_a`: 初始资产A数量
    /// - `initial_b`: 初始资产B数量
    ///
    /// # 返回
    /// - `Hash`: 池ID
    pub fn create_pool(
        asset_a: Address,
        asset_b: Address,
        initial_a: u256,
        initial_b: u256
    ) -> Hash {
        require(!asset_a.is_zero(), "Invalid asset A");
        require(!asset_b.is_zero(), "Invalid asset B");
        require(asset_a != asset_b, "Assets must be different");
        require(initial_a > 0, "Initial A must be positive");
        require(initial_b > 0, "Initial B must be positive");
        
        // 确保资产顺序一致（A < B）
        let (token0, token1, amount0, amount1) = if asset_a < asset_b {
            (asset_a, asset_b, initial_a, initial_b)
        } else {
            (asset_b, asset_a, initial_b, initial_a)
        };
        
        // 检查池是否已存在
        if let Some(existing_pools) = self._pool_index.get(token0) {
            require(!existing_pools.contains_key(token1), "Pool already exists");
        }
        
        // 生成池ID
        let pool_id = self._generate_pool_id(token0, token1);
        
        // 计算初始LP代币数量（几何平均数）
        let initial_lp = sqrt(safe_mul(amount0, amount1));
        require(initial_lp > self._minimum_liquidity, "Insufficient initial liquidity");
        
        // 锁定最小流动性
        let lp_to_provider = safe_sub(initial_lp, self._minimum_liquidity);
        
        let pool = LiquidityPool {
            pool_id: pool_id,
            asset_a: token0,
            asset_b: token1,
            reserve_a: amount0,
            reserve_b: amount1,
            total_lp_supply: initial_lp,
            fee_rate: self._default_fee_rate,
            accumulated_fee_a: 0,
            accumulated_fee_b: 0,
            last_updated: block.timestamp,
            k_last: safe_mul(amount0, amount1)
        };
        
        self._pools[pool_id] = pool;
        
        // 更新索引
        if !self._pool_index.contains_key(token0) {
            self._pool_index[token0] = Map::new();
        }
        self._pool_index[token0][token1] = pool_id;
        
        // 记录流动性提供者
        if !self._providers.contains_key(msg.sender) {
            self._providers[msg.sender] = Map::new();
        }
        
        let lp_info = LiquidityProvider {
            provider: msg.sender,
            pool_id: pool_id,
            lp_tokens: lp_to_provider,
            provided_at: block.timestamp,
            claimed_reward_a: 0,
            claimed_reward_b: 0
        };
        
        self._providers[msg.sender][pool_id] = lp_info;
        
        // 实际需要转移资产到池中
        
        emit AddLiquidity {
            pool_id: pool_id,
            provider: msg.sender,
            amount_a: amount0,
            amount_b: amount1,
            lp_tokens: lp_to_provider,
            timestamp: block.timestamp
        };
        
        return pool_id;
    }
    
    /// 获取池信息
    ///
    /// # 参数
    /// - `pool_id`: 池ID
    ///
    /// # 返回
    /// - `LiquidityPool`: 池信息
    pub fn get_pool(pool_id: Hash) -> LiquidityPool {
        require(self._pools.contains_key(pool_id), "Pool not found");
        return self._pools[pool_id];
    }
    
    /// 通过资产对查找池
    ///
    /// # 参数
    /// - `asset_a`: 资产A地址
    /// - `asset_b`: 资产B地址
    ///
    /// # 返回
    /// - `Option<Hash>`: 池ID
    pub fn find_pool(asset_a: Address, asset_b: Address) -> Option<Hash> {
        let (token0, token1) = if asset_a < asset_b {
            (asset_a, asset_b)
        } else {
            (asset_b, asset_a)
        };
        
        return self._pool_index.get(token0)
            .and_then(|m| m.get(token1));
    }
    
    // ========== 添加和移除流动性 ==========
    
    /// 添加流动性
    ///
    /// # 参数
    /// - `pool_id`: 池ID
    /// - `amount_a`: 资产A数量
    /// - `amount_b`: 资产B数量
    /// - `min_lp_tokens`: 最小LP代币数量（滑点保护）
    ///
    /// # 返回
    /// - `u256`: 获得的LP代币数量
    pub fn add_liquidity(
        pool_id: Hash,
        amount_a: u256,
        amount_b: u256,
        min_lp_tokens: u256
    ) -> u256 {
        require(self._pools.contains_key(pool_id), "Pool not found");
        require(amount_a > 0, "Amount A must be positive");
        require(amount_b > 0, "Amount B must be positive");
        
        let mut pool = self._pools[pool_id];
        
        // 计算最优添加比例
        let optimal_b = safe_mul(amount_a, pool.reserve_b) / pool.reserve_a;
        
        let (final_a, final_b) = if optimal_b <= amount_b {
            (amount_a, optimal_b)
        } else {
            let optimal_a = safe_mul(amount_b, pool.reserve_a) / pool.reserve_b;
            (optimal_a, amount_b)
        };
        
        // 计算LP代币数量
        let lp_tokens = if pool.total_lp_supply == 0 {
            sqrt(safe_mul(final_a, final_b))
        } else {
            let lp_a = safe_mul(final_a, pool.total_lp_supply) / pool.reserve_a;
            let lp_b = safe_mul(final_b, pool.total_lp_supply) / pool.reserve_b;
            if lp_a < lp_b { lp_a } else { lp_b }
        };
        
        require(lp_tokens >= min_lp_tokens, "Slippage too high");
        
        // 更新池状态
        pool.reserve_a = safe_add(pool.reserve_a, final_a);
        pool.reserve_b = safe_add(pool.reserve_b, final_b);
        pool.total_lp_supply = safe_add(pool.total_lp_supply, lp_tokens);
        pool.k_last = safe_mul(pool.reserve_a, pool.reserve_b);
        pool.last_updated = block.timestamp;
        
        self._pools[pool_id] = pool;
        
        // 更新流动性提供者信息
        if !self._providers.contains_key(msg.sender) {
            self._providers[msg.sender] = Map::new();
        }
        
        if let Some(mut lp_info) = self._providers[msg.sender].get(pool_id) {
            lp_info.lp_tokens = safe_add(lp_info.lp_tokens, lp_tokens);
            self._providers[msg.sender][pool_id] = lp_info;
        } else {
            let lp_info = LiquidityProvider {
                provider: msg.sender,
                pool_id: pool_id,
                lp_tokens: lp_tokens,
                provided_at: block.timestamp,
                claimed_reward_a: 0,
                claimed_reward_b: 0
            };
            self._providers[msg.sender][pool_id] = lp_info;
        }
        
        // 实际需要转移资产到池中
        
        emit AddLiquidity {
            pool_id: pool_id,
            provider: msg.sender,
            amount_a: final_a,
            amount_b: final_b,
            lp_tokens: lp_tokens,
            timestamp: block.timestamp
        };
        
        return lp_tokens;
    }
    
    /// 移除流动性
    ///
    /// # 参数
    /// - `pool_id`: 池ID
    /// - `lp_tokens`: LP代币数量
    /// - `min_amount_a`: 最小资产A数量（滑点保护）
    /// - `min_amount_b`: 最小资产B数量（滑点保护）
    ///
    /// # 返回
    /// - `(u256, u256)`: (资产A数量, 资产B数量)
    pub fn remove_liquidity(
        pool_id: Hash,
        lp_tokens: u256,
        min_amount_a: u256,
        min_amount_b: u256
    ) -> (u256, u256) {
        require(self._pools.contains_key(pool_id), "Pool not found");
        require(lp_tokens > 0, "LP tokens must be positive");
        require(self._providers.contains_key(msg.sender), "No liquidity provided");
        require(
            self._providers[msg.sender].contains_key(pool_id),
            "No liquidity in this pool"
        );
        
        let mut lp_info = self._providers[msg.sender][pool_id];
        require(lp_info.lp_tokens >= lp_tokens, "Insufficient LP tokens");
        
        let mut pool = self._pools[pool_id];
        
        // 计算可取回的资产数量
        let amount_a = safe_mul(lp_tokens, pool.reserve_a) / pool.total_lp_supply;
        let amount_b = safe_mul(lp_tokens, pool.reserve_b) / pool.total_lp_supply;
        
        require(amount_a >= min_amount_a, "Slippage too high for A");
        require(amount_b >= min_amount_b, "Slippage too high for B");
        
        // 更新池状态
        pool.reserve_a = safe_sub(pool.reserve_a, amount_a);
        pool.reserve_b = safe_sub(pool.reserve_b, amount_b);
        pool.total_lp_supply = safe_sub(pool.total_lp_supply, lp_tokens);
        pool.k_last = safe_mul(pool.reserve_a, pool.reserve_b);
        pool.last_updated = block.timestamp;
        
        self._pools[pool_id] = pool;
        
        // 更新流动性提供者信息
        lp_info.lp_tokens = safe_sub(lp_info.lp_tokens, lp_tokens);
        self._providers[msg.sender][pool_id] = lp_info;
        
        // 实际需要转移资产给提供者
        
        emit RemoveLiquidity {
            pool_id: pool_id,
            provider: msg.sender,
            amount_a: amount_a,
            amount_b: amount_b,
            lp_tokens: lp_tokens,
            timestamp: block.timestamp
        };
        
        return (amount_a, amount_b);
    }
    
    // ========== 交换 ==========
    
    /// 交换（精确输入）
    ///
    /// # 参数
    /// - `pool_id`: 池ID
    /// - `asset_in`: 输入资产
    /// - `amount_in`: 输入数量
    /// - `min_amount_out`: 最小输出数量（滑点保护）
    ///
    /// # 返回
    /// - `u256`: 输出数量
    pub fn swap_exact_input(
        pool_id: Hash,
        asset_in: Address,
        amount_in: u256,
        min_amount_out: u256
    ) -> u256 {
        require(self._pools.contains_key(pool_id), "Pool not found");
        require(amount_in > 0, "Amount in must be positive");
        
        let mut pool = self._pools[pool_id];
        
        // 确定输入输出资产
        let (reserve_in, reserve_out, asset_out) = if asset_in == pool.asset_a {
            (pool.reserve_a, pool.reserve_b, pool.asset_b)
        } else if asset_in == pool.asset_b {
            (pool.reserve_b, pool.reserve_a, pool.asset_a)
        } else {
            revert("Invalid asset");
        };
        
        // 计算输出数量（扣除手续费）
        let amount_in_with_fee = safe_mul(amount_in, (10000 - pool.fee_rate) as u256);
        let numerator = safe_mul(amount_in_with_fee, reserve_out);
        let denominator = safe_add(safe_mul(reserve_in, 10000), amount_in_with_fee);
        let amount_out = numerator / denominator;
        
        require(amount_out >= min_amount_out, "Slippage too high");
        require(amount_out < reserve_out, "Insufficient liquidity");
        
        // 计算手续费
        let fee = safe_mul(amount_in, pool.fee_rate as u256) / 10000;
        
        // 更新储备量
        if asset_in == pool.asset_a {
            pool.reserve_a = safe_add(pool.reserve_a, amount_in);
            pool.reserve_b = safe_sub(pool.reserve_b, amount_out);
            pool.accumulated_fee_a = safe_add(pool.accumulated_fee_a, fee);
        } else {
            pool.reserve_b = safe_add(pool.reserve_b, amount_in);
            pool.reserve_a = safe_sub(pool.reserve_a, amount_out);
            pool.accumulated_fee_b = safe_add(pool.accumulated_fee_b, fee);
        }
        
        pool.k_last = safe_mul(pool.reserve_a, pool.reserve_b);
        pool.last_updated = block.timestamp;
        
        self._pools[pool_id] = pool;
        
        // 生成交换ID
        let swap_id = self._generate_swap_id(pool_id, msg.sender);
        
        // 记录交换
        let swap_record = SwapRecord {
            swap_id: swap_id,
            pool_id: pool_id,
            swapper: msg.sender,
            asset_in: asset_in,
            amount_in: amount_in,
            asset_out: asset_out,
            amount_out: amount_out,
            fee: fee,
            timestamp: block.timestamp
        };
        
        self._swaps[swap_id] = swap_record;
        
        // 实际需要转移资产
        
        emit Swap {
            swap_id: swap_id,
            pool_id: pool_id,
            swapper: msg.sender,
            asset_in: asset_in,
            amount_in: amount_in,
            asset_out: asset_out,
            amount_out: amount_out,
            fee: fee,
            timestamp: block.timestamp
        };
        
        return amount_out;
    }
    
    /// 交换（精确输出）
    ///
    /// # 参数
    /// - `pool_id`: 池ID
    /// - `asset_out`: 输出资产
    /// - `amount_out`: 输出数量
    /// - `max_amount_in`: 最大输入数量（滑点保护）
    ///
    /// # 返回
    /// - `u256`: 输入数量
    pub fn swap_exact_output(
        pool_id: Hash,
        asset_out: Address,
        amount_out: u256,
        max_amount_in: u256
    ) -> u256 {
        require(self._pools.contains_key(pool_id), "Pool not found");
        require(amount_out > 0, "Amount out must be positive");
        
        let mut pool = self._pools[pool_id];
        
        // 确定输入输出资产
        let (reserve_in, reserve_out, asset_in) = if asset_out == pool.asset_a {
            (pool.reserve_b, pool.reserve_a, pool.asset_b)
        } else if asset_out == pool.asset_b {
            (pool.reserve_a, pool.reserve_b, pool.asset_a)
        } else {
            revert("Invalid asset");
        };
        
        require(amount_out < reserve_out, "Insufficient liquidity");
        
        // 计算输入数量（包含手续费）
        let numerator = safe_mul(safe_mul(reserve_in, amount_out), 10000);
        let denominator = safe_mul(
            safe_sub(reserve_out, amount_out),
            (10000 - pool.fee_rate) as u256
        );
        let amount_in = safe_add(numerator / denominator, 1); // 向上取整
        
        require(amount_in <= max_amount_in, "Slippage too high");
        
        // 计算手续费
        let fee = safe_mul(amount_in, pool.fee_rate as u256) / 10000;
        
        // 更新储备量
        if asset_out == pool.asset_a {
            pool.reserve_b = safe_add(pool.reserve_b, amount_in);
            pool.reserve_a = safe_sub(pool.reserve_a, amount_out);
            pool.accumulated_fee_b = safe_add(pool.accumulated_fee_b, fee);
        } else {
            pool.reserve_a = safe_add(pool.reserve_a, amount_in);
            pool.reserve_b = safe_sub(pool.reserve_b, amount_out);
            pool.accumulated_fee_a = safe_add(pool.accumulated_fee_a, fee);
        }
        
        pool.k_last = safe_mul(pool.reserve_a, pool.reserve_b);
        pool.last_updated = block.timestamp;
        
        self._pools[pool_id] = pool;
        
        // 生成交换ID
        let swap_id = self._generate_swap_id(pool_id, msg.sender);
        
        // 记录交换
        let swap_record = SwapRecord {
            swap_id: swap_id,
            pool_id: pool_id,
            swapper: msg.sender,
            asset_in: asset_in,
            amount_in: amount_in,
            asset_out: asset_out,
            amount_out: amount_out,
            fee: fee,
            timestamp: block.timestamp
        };
        
        self._swaps[swap_id] = swap_record;
        
        emit Swap {
            swap_id: swap_id,
            pool_id: pool_id,
            swapper: msg.sender,
            asset_in: asset_in,
            amount_in: amount_in,
            asset_out: asset_out,
            amount_out: amount_out,
            fee: fee,
            timestamp: block.timestamp
        };
        
        return amount_in;
    }
    
    /// 获取输出数量（不执行交换）
    ///
    /// # 参数
    /// - `pool_id`: 池ID
    /// - `asset_in`: 输入资产
    /// - `amount_in`: 输入数量
    ///
    /// # 返回
    /// - `u256`: 输出数量
    pub fn get_amount_out(
        pool_id: Hash,
        asset_in: Address,
        amount_in: u256
    ) -> u256 {
        require(self._pools.contains_key(pool_id), "Pool not found");
        
        let pool = self._pools[pool_id];
        
        let (reserve_in, reserve_out) = if asset_in == pool.asset_a {
            (pool.reserve_a, pool.reserve_b)
        } else {
            (pool.reserve_b, pool.reserve_a)
        };
        
        let amount_in_with_fee = safe_mul(amount_in, (10000 - pool.fee_rate) as u256);
        let numerator = safe_mul(amount_in_with_fee, reserve_out);
        let denominator = safe_add(safe_mul(reserve_in, 10000), amount_in_with_fee);
        
        return numerator / denominator;
    }
    
    // ========== 奖励管理 ==========
    
    /// 计算待领取奖励
    ///
    /// # 参数
    /// - `pool_id`: 池ID
    /// - `provider`: 提供者地址
    ///
    /// # 返回
    /// - `(u256, u256)`: (奖励A, 奖励B)
    pub fn calculate_rewards(
        pool_id: Hash,
        provider: Address
    ) -> (u256, u256) {
        require(self._pools.contains_key(pool_id), "Pool not found");
        require(self._providers.contains_key(provider), "No liquidity provided");
        require(
            self._providers[provider].contains_key(pool_id),
            "No liquidity in this pool"
        );
        
        let pool = self._pools[pool_id];
        let lp_info = self._providers[provider][pool_id];
        
        // 计算份额
        let share = safe_mul(lp_info.lp_tokens, 1e18) / pool.total_lp_supply;
        
        // 计算奖励
        let reward_a = safe_sub(
            safe_mul(pool.accumulated_fee_a, share) / 1e18,
            lp_info.claimed_reward_a
        );
        
        let reward_b = safe_sub(
            safe_mul(pool.accumulated_fee_b, share) / 1e18,
            lp_info.claimed_reward_b
        );
        
        return (reward_a, reward_b);
    }
    
    /// 领取奖励
    ///
    /// # 参数
    /// - `pool_id`: 池ID
    ///
    /// # 返回
    /// - `(u256, u256)`: (奖励A, 奖励B)
    pub fn claim_rewards(pool_id: Hash) -> (u256, u256) {
        let (reward_a, reward_b) = self.calculate_rewards(pool_id, msg.sender);
        
        require(reward_a > 0 || reward_b > 0, "No rewards to claim");
        
        // 更新已领取奖励
        let mut lp_info = self._providers[msg.sender][pool_id];
        lp_info.claimed_reward_a = safe_add(lp_info.claimed_reward_a, reward_a);
        lp_info.claimed_reward_b = safe_add(lp_info.claimed_reward_b, reward_b);
        self._providers[msg.sender][pool_id] = lp_info;
        
        // 实际需要转移奖励
        
        emit ClaimRewards {
            pool_id: pool_id,
            provider: msg.sender,
            reward_a: reward_a,
            reward_b: reward_b,
            timestamp: block.timestamp
        };
        
        return (reward_a, reward_b);
    }
    
    // ========== 查询函数 ==========
    
    /// 获取流动性提供者信息
    ///
    /// # 参数
    /// - `provider`: 提供者地址
    /// - `pool_id`: 池ID
    ///
    /// # 返回
    /// - `Option<LiquidityProvider>`: 提供者信息
    pub fn get_provider_info(
        provider: Address,
        pool_id: Hash
    ) -> Option<LiquidityProvider> {
        return self._providers.get(provider)
            .and_then(|m| m.get(pool_id));
    }
    
    /// 获取交换记录
    ///
    /// # 参数
    /// - `swap_id`: 交换ID
    ///
    /// # 返回
    /// - `SwapRecord`: 交换记录
    pub fn get_swap(swap_id: Hash) -> SwapRecord {
        require(self._swaps.contains_key(swap_id), "Swap not found");
        return self._swaps[swap_id];
    }
    
    // ========== 内部函数 ==========
    
    /// 生成池ID
    fn _generate_pool_id(asset_a: Address, asset_b: Address) -> Hash {
        let mut data = Bytes::new();
        data.extend(asset_a.as_bytes());
        data.extend(asset_b.as_bytes());
        return sha3_384_hash(data);
    }
    
    /// 生成交换ID
    fn _generate_swap_id(pool_id: Hash, swapper: Address) -> Hash {
        let mut data = Bytes::new();
        data.extend(pool_id.as_bytes());
        data.extend(swapper.as_bytes());
        data.extend(block.timestamp.to_bytes());
        data.extend(tx.hash.as_bytes());
        return sha3_384_hash(data);
    }
}