package dex

import (
	"context"
	"fmt"
	"math/big"
	"strings"

	"github.com/ethereum/go-ethereum"
	"github.com/ethereum/go-ethereum/accounts/abi"
	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/core/types"
	"github.com/ethereum/go-ethereum/ethclient"
)

// SushiSwapDecoder implements DEXDecoder for SushiSwap
type SushiSwapDecoder struct {
	*BaseDecoder
	pairABI   abi.ABI
	routerABI abi.ABI
}

// SushiSwap Pair ABI (minimal, compatible with UniswapV2)
const sushiSwapPairABI = `[
	{
		"constant": true,
		"inputs": [],
		"name": "getReserves",
		"outputs": [
			{"internalType": "uint112", "name": "reserve0", "type": "uint112"},
			{"internalType": "uint112", "name": "reserve1", "type": "uint112"},
			{"internalType": "uint32", "name": "blockTimestampLast", "type": "uint32"}
		],
		"payable": false,
		"stateMutability": "view",
		"type": "function"
	},
	{
		"constant": true,
		"inputs": [],
		"name": "token0",
		"outputs": [{"internalType": "address", "name": "", "type": "address"}],
		"payable": false,
		"stateMutability": "view",
		"type": "function"
	},
	{
		"constant": true,
		"inputs": [],
		"name": "token1",
		"outputs": [{"internalType": "address", "name": "", "type": "address"}],
		"payable": false,
		"stateMutability": "view",
		"type": "function"
	}
]`

// SushiSwap Router ABI (minimal)
const sushiSwapRouterABI = `[
	{
		"inputs": [
			{"internalType": "uint256", "name": "amountIn", "type": "uint256"},
			{"internalType": "uint256", "name": "amountOutMin", "type": "uint256"},
			{"internalType": "address[]", "name": "path", "type": "address[]"},
			{"internalType": "address", "name": "to", "type": "address"},
			{"internalType": "uint256", "name": "deadline", "type": "uint256"}
		],
		"name": "swapExactTokensForTokens",
		"outputs": [{"internalType": "uint256[]", "name": "amounts", "type": "uint256[]"}],
		"stateMutability": "nonpayable",
		"type": "function"
	},
	{
		"inputs": [
			{"internalType": "uint256", "name": "amountOut", "type": "uint256"},
			{"internalType": "uint256", "name": "amountInMax", "type": "uint256"},
			{"internalType": "address[]", "name": "path", "type": "address[]"},
			{"internalType": "address", "name": "to", "type": "address"},
			{"internalType": "uint256", "name": "deadline", "type": "uint256"}
		],
		"name": "swapTokensForExactTokens",
		"outputs": [{"internalType": "uint256[]", "name": "amounts", "type": "uint256[]"}],
		"stateMutability": "nonpayable",
		"type": "function"
	}
]`

// NewSushiSwapDecoder creates a new SushiSwap decoder
func NewSushiSwapDecoder(client *ethclient.Client) *SushiSwapDecoder {
	pairABI, _ := abi.JSON(strings.NewReader(sushiSwapPairABI))
	routerABI, _ := abi.JSON(strings.NewReader(sushiSwapRouterABI))

	return &SushiSwapDecoder{
		BaseDecoder: NewBaseDecoder(ProtocolSushiSwap, client),
		pairABI:     pairABI,
		routerABI:   routerABI,
	}
}

// DecodeSwap decodes a SushiSwap swap transaction
func (d *SushiSwapDecoder) DecodeSwap(tx *types.Transaction) (*SwapInfo, error) {
	data := tx.Data()
	if len(data) < 4 {
		return nil, fmt.Errorf("transaction data too short")
	}

	method, err := d.routerABI.MethodById(data[:4])
	if err != nil {
		return nil, fmt.Errorf("failed to get method: %w", err)
	}

	var swapInfo *SwapInfo

	switch method.Name {
	case "swapExactTokensForTokens":
		params := make(map[string]interface{})
		if err := method.Inputs.UnpackIntoMap(params, data[4:]); err != nil {
			return nil, fmt.Errorf("failed to unpack params: %w", err)
		}

		path := params["path"].([]common.Address)
		if len(path) < 2 {
			return nil, fmt.Errorf("invalid swap path length: %d", len(path))
		}

		swapInfo = &SwapInfo{
			Protocol:  ProtocolSushiSwap,
			TokenIn:   path[0],
			TokenOut:  path[len(path)-1],
			AmountIn:  params["amountIn"].(*big.Int),
			AmountOut: params["amountOutMin"].(*big.Int),
			Recipient: params["to"].(common.Address),
			Deadline:  params["deadline"].(*big.Int),
			Fee:       big.NewInt(30), // 0.3% fee
		}

	case "swapTokensForExactTokens":
		params := make(map[string]interface{})
		if err := method.Inputs.UnpackIntoMap(params, data[4:]); err != nil {
			return nil, fmt.Errorf("failed to unpack params: %w", err)
		}

		path := params["path"].([]common.Address)
		if len(path) < 2 {
			return nil, fmt.Errorf("invalid swap path length: %d", len(path))
		}

		swapInfo = &SwapInfo{
			Protocol:  ProtocolSushiSwap,
			TokenIn:   path[0],
			TokenOut:  path[len(path)-1],
			AmountIn:  params["amountInMax"].(*big.Int),
			AmountOut: params["amountOut"].(*big.Int),
			Recipient: params["to"].(common.Address),
			Deadline:  params["deadline"].(*big.Int),
			Fee:       big.NewInt(30), // 0.3% fee
		}

	default:
		return nil, fmt.Errorf("unsupported method: %s", method.Name)
	}

	return swapInfo, nil
}

// GetPoolReserves fetches current pool reserves for SushiSwap
func (d *SushiSwapDecoder) GetPoolReserves(ctx context.Context, client *ethclient.Client, poolAddress common.Address) (*PoolReserves, error) {
	// Get reserves
	reservesData, err := client.CallContract(ctx, ethereum.CallMsg{
		To:   &poolAddress,
		Data: d.pairABI.Methods["getReserves"].ID,
	}, nil)
	if err != nil {
		return nil, fmt.Errorf("failed to get reserves: %w", err)
	}

	var reserves struct {
		Reserve0           *big.Int
		Reserve1           *big.Int
		BlockTimestampLast uint32
	}
	if err := d.pairABI.UnpackIntoInterface(&reserves, "getReserves", reservesData); err != nil {
		return nil, fmt.Errorf("failed to unpack reserves: %w", err)
	}

	// Get token0
	token0Data, err := client.CallContract(ctx, ethereum.CallMsg{
		To:   &poolAddress,
		Data: d.pairABI.Methods["token0"].ID,
	}, nil)
	if err != nil {
		return nil, fmt.Errorf("failed to get token0: %w", err)
	}
	token0 := common.BytesToAddress(token0Data)

	// Get token1
	token1Data, err := client.CallContract(ctx, ethereum.CallMsg{
		To:   &poolAddress,
		Data: d.pairABI.Methods["token1"].ID,
	}, nil)
	if err != nil {
		return nil, fmt.Errorf("failed to get token1: %w", err)
	}
	token1 := common.BytesToAddress(token1Data)

	return &PoolReserves{
		Token0:      token0,
		Token1:      token1,
		Reserve0:    reserves.Reserve0,
		Reserve1:    reserves.Reserve1,
		Protocol:    ProtocolSushiSwap,
		PoolAddress: poolAddress,
		Fee:         big.NewInt(30), // 0.3% fee
	}, nil
}

// CalculateOutput calculates expected output for SushiSwap using constant product formula
func (d *SushiSwapDecoder) CalculateOutput(amountIn *big.Int, reserves *PoolReserves, tokenIn common.Address) (*big.Int, error) {
	if amountIn == nil || amountIn.Sign() <= 0 {
		return nil, fmt.Errorf("invalid amountIn")
	}

	var reserveIn, reserveOut *big.Int
	if tokenIn == reserves.Token0 {
		reserveIn = reserves.Reserve0
		reserveOut = reserves.Reserve1
	} else if tokenIn == reserves.Token1 {
		reserveIn = reserves.Reserve1
		reserveOut = reserves.Reserve0
	} else {
		return nil, fmt.Errorf("tokenIn not in pool")
	}

	if reserveIn.Sign() == 0 || reserveOut.Sign() == 0 {
		return nil, fmt.Errorf("insufficient liquidity")
	}

	// Constant product formula: (x + Δx * 0.997) * (y - Δy) = x * y
	// Solving for Δy: Δy = (Δx * 0.997 * y) / (x + Δx * 0.997)

	amountInWithFee := new(big.Int).Mul(amountIn, big.NewInt(997)) // 0.3% fee = 99.7% of amount
	numerator := new(big.Int).Mul(amountInWithFee, reserveOut)
	denominator := new(big.Int).Add(
		new(big.Int).Mul(reserveIn, big.NewInt(1000)),
		amountInWithFee,
	)

	amountOut := new(big.Int).Div(numerator, denominator)
	return amountOut, nil
}

// GetQuote gets a price quote for SushiSwap
func (d *SushiSwapDecoder) GetQuote(ctx context.Context, client *ethclient.Client, tokenIn, tokenOut common.Address, amountIn *big.Int) (*PriceQuote, error) {
	// TODO: Implement actual pool lookup via factory
	// For now, return error
	return nil, fmt.Errorf("GetQuote not yet implemented for SushiSwap")
}

// IsValidPool checks if a pool is a valid SushiSwap pool
func (d *SushiSwapDecoder) IsValidPool(ctx context.Context, client *ethclient.Client, poolAddress common.Address) (bool, error) {
	// Try to call getReserves() - if it succeeds, it's a valid pool
	_, err := client.CallContract(ctx, ethereum.CallMsg{
		To:   &poolAddress,
		Data: d.pairABI.Methods["getReserves"].ID,
	}, nil)

	return err == nil, nil
}