package uniswap

import (
	"context"
	"errors"
	"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/ethclient"
)

// PoolVersion represents the version of a DEX pool
type PoolVersion int

const (
	PoolVersionUnknown PoolVersion = iota
	PoolVersionV2      // Uniswap V2 style (uses getReserves)
	PoolVersionV3      // Uniswap V3 style (uses slot0)
	PoolVersionBalancer
	PoolVersionCurve
)

// String returns the string representation of the pool version
func (pv PoolVersion) String() string {
	switch pv {
	case PoolVersionV2:
		return "UniswapV2"
	case PoolVersionV3:
		return "UniswapV3"
	case PoolVersionBalancer:
		return "Balancer"
	case PoolVersionCurve:
		return "Curve"
	default:
		return "Unknown"
	}
}

// PoolDetector detects the version of a DEX pool
type PoolDetector struct {
	client *ethclient.Client

	// Cache of detected pool versions
	versionCache map[common.Address]PoolVersion
}

// NewPoolDetector creates a new pool detector
func NewPoolDetector(client *ethclient.Client) *PoolDetector {
	return &PoolDetector{
		client:       client,
		versionCache: make(map[common.Address]PoolVersion),
	}
}

// DetectPoolVersion detects the version of a pool by checking which functions it supports
func (pd *PoolDetector) DetectPoolVersion(ctx context.Context, poolAddress common.Address) (PoolVersion, error) {
	// Check cache first
	if version, exists := pd.versionCache[poolAddress]; exists {
		return version, nil
	}

	// Try V3 first (slot0 function)
	if pd.hasSlot0(ctx, poolAddress) {
		pd.versionCache[poolAddress] = PoolVersionV3
		return PoolVersionV3, nil
	}

	// Try V2 (getReserves function)
	if pd.hasGetReserves(ctx, poolAddress) {
		pd.versionCache[poolAddress] = PoolVersionV2
		return PoolVersionV2, nil
	}

	// Try Balancer (getPoolId function)
	if pd.hasGetPoolId(ctx, poolAddress) {
		pd.versionCache[poolAddress] = PoolVersionBalancer
		return PoolVersionBalancer, nil
	}

	// Unknown pool type
	pd.versionCache[poolAddress] = PoolVersionUnknown
	return PoolVersionUnknown, errors.New("unable to detect pool version")
}

// hasSlot0 checks if a pool has the slot0() function (Uniswap V3)
func (pd *PoolDetector) hasSlot0(ctx context.Context, poolAddress common.Address) bool {
	// Create minimal ABI for slot0 function
	slot0ABI := `[{
		"inputs": [],
		"name": "slot0",
		"outputs": [
			{"internalType": "uint160", "name": "sqrtPriceX96", "type": "uint160"},
			{"internalType": "int24", "name": "tick", "type": "int24"},
			{"internalType": "uint16", "name": "observationIndex", "type": "uint16"},
			{"internalType": "uint16", "name": "observationCardinality", "type": "uint16"},
			{"internalType": "uint16", "name": "observationCardinalityNext", "type": "uint16"},
			{"internalType": "uint8", "name": "feeProtocol", "type": "uint8"},
			{"internalType": "bool", "name": "unlocked", "type": "bool"}
		],
		"stateMutability": "view",
		"type": "function"
	}]`

	parsedABI, err := abi.JSON(strings.NewReader(slot0ABI))
	if err != nil {
		return false
	}

	data, err := parsedABI.Pack("slot0")
	if err != nil {
		return false
	}

	msg := ethereum.CallMsg{
		To:   &poolAddress,
		Data: data,
	}

	result, err := pd.client.CallContract(ctx, msg, nil)
	if err != nil {
		return false
	}

	// Check if result has the expected length for slot0 return values
	// slot0 returns 7 values, should be at least 7*32 = 224 bytes
	return len(result) >= 224
}

// hasGetReserves checks if a pool has the getReserves() function (Uniswap V2)
func (pd *PoolDetector) hasGetReserves(ctx context.Context, poolAddress common.Address) bool {
	// Create minimal ABI for getReserves function
	getReservesABI := `[{
		"inputs": [],
		"name": "getReserves",
		"outputs": [
			{"internalType": "uint112", "name": "_reserve0", "type": "uint112"},
			{"internalType": "uint112", "name": "_reserve1", "type": "uint112"},
			{"internalType": "uint32", "name": "_blockTimestampLast", "type": "uint32"}
		],
		"stateMutability": "view",
		"type": "function"
	}]`

	parsedABI, err := abi.JSON(strings.NewReader(getReservesABI))
	if err != nil {
		return false
	}

	data, err := parsedABI.Pack("getReserves")
	if err != nil {
		return false
	}

	msg := ethereum.CallMsg{
		To:   &poolAddress,
		Data: data,
	}

	result, err := pd.client.CallContract(ctx, msg, nil)
	if err != nil {
		return false
	}

	// Check if result has the expected length for getReserves return values
	// getReserves returns 3 values (uint112, uint112, uint32) = 96 bytes
	return len(result) >= 96
}

// hasGetPoolId checks if a pool has the getPoolId() function (Balancer)
func (pd *PoolDetector) hasGetPoolId(ctx context.Context, poolAddress common.Address) bool {
	// Create minimal ABI for getPoolId function
	getPoolIdABI := `[{
		"inputs": [],
		"name": "getPoolId",
		"outputs": [{"internalType": "bytes32", "name": "", "type": "bytes32"}],
		"stateMutability": "view",
		"type": "function"
	}]`

	parsedABI, err := abi.JSON(strings.NewReader(getPoolIdABI))
	if err != nil {
		return false
	}

	data, err := parsedABI.Pack("getPoolId")
	if err != nil {
		return false
	}

	msg := ethereum.CallMsg{
		To:   &poolAddress,
		Data: data,
	}

	result, err := pd.client.CallContract(ctx, msg, nil)
	if err != nil {
		return false
	}

	// Check if result is a bytes32 (32 bytes)
	return len(result) == 32
}

// GetReservesV2 fetches reserves from a Uniswap V2 style pool
func (pd *PoolDetector) GetReservesV2(ctx context.Context, poolAddress common.Address) (*big.Int, *big.Int, error) {
	getReservesABI := `[{
		"inputs": [],
		"name": "getReserves",
		"outputs": [
			{"internalType": "uint112", "name": "_reserve0", "type": "uint112"},
			{"internalType": "uint112", "name": "_reserve1", "type": "uint112"},
			{"internalType": "uint32", "name": "_blockTimestampLast", "type": "uint32"}
		],
		"stateMutability": "view",
		"type": "function"
	}]`

	parsedABI, err := abi.JSON(strings.NewReader(getReservesABI))
	if err != nil {
		return nil, nil, fmt.Errorf("failed to parse getReserves ABI: %w", err)
	}

	data, err := parsedABI.Pack("getReserves")
	if err != nil {
		return nil, nil, fmt.Errorf("failed to pack getReserves call: %w", err)
	}

	msg := ethereum.CallMsg{
		To:   &poolAddress,
		Data: data,
	}

	result, err := pd.client.CallContract(ctx, msg, nil)
	if err != nil {
		return nil, nil, fmt.Errorf("failed to call getReserves: %w", err)
	}

	unpacked, err := parsedABI.Unpack("getReserves", result)
	if err != nil {
		return nil, nil, fmt.Errorf("failed to unpack getReserves result: %w", err)
	}

	if len(unpacked) < 2 {
		return nil, nil, fmt.Errorf("unexpected number of return values from getReserves: got %d, expected 3", len(unpacked))
	}

	reserve0, ok := unpacked[0].(*big.Int)
	if !ok {
		return nil, nil, fmt.Errorf("failed to convert reserve0 to *big.Int")
	}

	reserve1, ok := unpacked[1].(*big.Int)
	if !ok {
		return nil, nil, fmt.Errorf("failed to convert reserve1 to *big.Int")
	}

	return reserve0, reserve1, nil
}

// ClearCache clears the version cache
func (pd *PoolDetector) ClearCache() {
	pd.versionCache = make(map[common.Address]PoolVersion)
}

// GetCachedVersion returns the cached version for a pool, if available
func (pd *PoolDetector) GetCachedVersion(poolAddress common.Address) (PoolVersion, bool) {
	version, exists := pd.versionCache[poolAddress]
	return version, exists
}