package calldata

import (
	"encoding/binary"
	"encoding/hex"
	"fmt"
	"math/big"
	"strings"

	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/crypto"

	"github.com/fraktal/mev-beta/internal/validation"
	"github.com/fraktal/mev-beta/pkg/common/selectors"
	"github.com/fraktal/mev-beta/pkg/uniswap"
)

// safeConvertUint64ToInt is defined in multicall.go to avoid duplication

// SwapCall represents a decoded swap-like call discovered inside a multicall payload.
type SwapCall struct {
	Selector          string
	Protocol          string
	TokenIn           common.Address
	TokenOut          common.Address
	Recipient         common.Address
	AmountIn          *big.Int
	AmountOut         *big.Int
	AmountOutMinimum  *big.Int
	Fee               uint32
	Path              []common.Address
	Factory           common.Address
	PoolAddress       common.Address
	Deadline          *big.Int
	Raw               []byte
	nested            bool
	heuristicFallback bool
}

// DecodeSwapCallsFromMulticall walks a multicall payload and returns decoded swap calls.
func DecodeSwapCallsFromMulticall(data []byte, ctx *MulticallContext) ([]*SwapCall, error) {
	calls, err := decodeMulticallCalls(data)
	if err != nil {
		return nil, err
	}

	validator := getAddressValidator()
	results := make([]*SwapCall, 0)
	for _, call := range calls {
		results = append(results, decodeSwapCallRecursive(call, ctx, validator, 0)...)
	}

	if len(results) == 0 && ctx == nil {
		heuristicTokens := heuristicExtractTokens(calls, validator)
		if len(heuristicTokens) >= 2 {
			for i := 0; i+1 < len(heuristicTokens); i += 2 {
				swap := &SwapCall{
					Selector:          "heuristic",
					Protocol:          "Unclassified",
					TokenIn:           heuristicTokens[i],
					TokenOut:          heuristicTokens[i+1],
					heuristicFallback: true,
				}
				results = append(results, swap)
			}
		}
	}

	return results, nil
}

func normalizedSelector(sel string) string {
	return strings.TrimPrefix(strings.ToLower(sel), "0x")
}

func decodeSwapCallRecursive(call []byte, ctx *MulticallContext, validator *validation.AddressValidator, depth int) []*SwapCall {
	if len(call) < 4 || depth > 6 {
		return nil
	}

	selector := strings.ToLower(hex.EncodeToString(call[:4]))
	payload := call[4:]

	switch selector {
	case normalizedSelector(selectors.UniswapV3MulticallWithDeadline),
		normalizedSelector(selectors.UniswapV3MulticallWithBlockhash),
		normalizedSelector(selectors.UniswapV3Multicall):
		nested, err := DecodeSwapCallsFromMulticall(payload, ctx)
		if err != nil {
			recordSuspiciousMulticall(payload, 0, ctx)
			return nil
		}
		markNested(nested)
		return nested
	case normalizedSelector(selectors.UniversalRouterExecute), normalizedSelector(selectors.UniversalRouterExecutePayable):
		return decodeUniversalRouterExecute(payload, ctx, validator, depth+1)
	}

	if swap := decodeDirectSwap(selector, payload, ctx); swap != nil {
		swap.Raw = call
		return []*SwapCall{swap}
	}

	return nil
}

func decodeDirectSwap(selector string, payload []byte, ctx *MulticallContext) *SwapCall {
	switch selector {
	case normalizedSelector(selectors.UniswapV3ExactInputSingle), normalizedSelector(selectors.UniswapV3ExactInputSingleLegacy):
		return decodeExactInputSingle(payload, ctx)
	case normalizedSelector(selectors.UniswapV3ExactOutputSingle):
		return decodeExactOutputSingle(payload, ctx)
	case normalizedSelector(selectors.UniswapV3ExactInput), normalizedSelector(selectors.UniswapV3ExactInputLegacy):
		return decodeExactInput(payload, ctx)
	case normalizedSelector(selectors.UniswapV3ExactOutput), normalizedSelector(selectors.UniswapV3ExactOutputBytes):
		return decodeExactOutput(payload, ctx)
	case normalizedSelector(selectors.UniswapV2SwapExactTokensForTokens),
		normalizedSelector(selectors.UniswapV2SwapTokensForExactTokens),
		normalizedSelector(selectors.UniswapV2SwapExactETHForTokens),
		normalizedSelector(selectors.UniswapV2SwapExactTokensForETH),
		normalizedSelector(selectors.UniswapV2SwapExactTokensForTokensSupportingFee),
		normalizedSelector(selectors.UniswapV2SwapExactTokensForTokensSupportingFeeLegacy),
		normalizedSelector(selectors.UniswapV2SwapExactETHForTokensSupportingFee),
		normalizedSelector(selectors.UniswapV2SwapExactTokensForETHSupportingFee):
		return decodeUniswapV2Swap(selector, payload, ctx)
	case normalizedSelector(selectors.NonfungiblePositionManagerMint):
		return decodePositionManagerMint(payload, ctx)
	default:
		return nil
	}
}

func decodeUniversalRouterExecute(payload []byte, ctx *MulticallContext, validator *validation.AddressValidator, depth int) []*SwapCall {
	if len(payload) < 96 {
		return nil
	}

	commandsOffset, ok := readInt(payload[0:32])
	if !ok {
		return nil
	}

	inputsOffset, ok := readInt(payload[32:64])
	if !ok {
		return nil
	}

	commands, ok := readBytesAt(payload, commandsOffset)
	if !ok {
		return nil
	}

	inputs, ok := readBytesArrayAt(payload, inputsOffset)
	if !ok {
		return nil
	}

	var results []*SwapCall
	for idx, input := range inputs {
		if len(commands) > idx {
			// command interpretation can refine protocol selection later if needed.
		}
		results = append(results, decodeSwapCallRecursive(input, ctx, validator, depth+1)...)
	}
	return results
}

func decodeExactInputSingle(payload []byte, ctx *MulticallContext) *SwapCall {
	if len(payload) < 256 {
		return nil
	}

	tokenIn := common.BytesToAddress(payload[12:32])
	tokenOut := common.BytesToAddress(payload[44:64])
	fee := binary.BigEndian.Uint32(append(make([]byte, 1), payload[93:96]...))
	recipient := common.BytesToAddress(payload[108:128])
	deadline := new(big.Int).SetBytes(payload[128:160])
	amountIn := new(big.Int).SetBytes(payload[160:192])
	amountOutMin := new(big.Int).SetBytes(payload[192:224])

	swap := &SwapCall{
		Selector:         selectors.UniswapV3ExactInputSingle,
		Protocol:         defaultProtocol(contextProtocol(ctx), "UniswapV3"),
		TokenIn:          tokenIn,
		TokenOut:         tokenOut,
		Recipient:        recipient,
		Deadline:         deadline,
		AmountIn:         amountIn,
		AmountOutMinimum: amountOutMin,
		Fee:              uint32(fee),
		Path:             []common.Address{tokenIn, tokenOut},
	}

	swap.Factory = common.HexToAddress("0x1F98431c8aD98523631AE4a59f267346ea31F984")
	swap.ensurePoolAddress()
	return swap
}

func decodeExactInput(payload []byte, ctx *MulticallContext) *SwapCall {
	if len(payload) < 160 {
		return nil
	}

	pathOffset, ok := readInt(payload[0:32])
	if !ok {
		return nil
	}

	recipient := common.BytesToAddress(payload[44:64])
	deadline := new(big.Int).SetBytes(payload[64:96])
	amountIn := new(big.Int).SetBytes(payload[96:128])
	amountOutMin := new(big.Int).SetBytes(payload[128:160])

	pathBytes, ok := readBytesAt(payload, pathOffset)
	if !ok || len(pathBytes) < 40 {
		return nil
	}

	tokenIn, tokenOut, fee := parseUniswapV3Path(pathBytes)

	swap := &SwapCall{
		Selector:         selectors.UniswapV3ExactInput,
		Protocol:         defaultProtocol(contextProtocol(ctx), "UniswapV3"),
		TokenIn:          tokenIn,
		TokenOut:         tokenOut,
		Recipient:        recipient,
		Deadline:         deadline,
		AmountIn:         amountIn,
		AmountOutMinimum: amountOutMin,
		Fee:              fee,
	}

	swap.Factory = common.HexToAddress("0x1F98431c8aD98523631AE4a59f267346ea31F984")
	swap.ensurePoolAddress()
	return swap
}

func decodeExactOutput(payload []byte, ctx *MulticallContext) *SwapCall {
	if len(payload) < 160 {
		return nil
	}

	pathOffset, ok := readInt(payload[0:32])
	if !ok {
		return nil
	}

	recipient := common.BytesToAddress(payload[44:64])
	deadline := new(big.Int).SetBytes(payload[64:96])
	amountOut := new(big.Int).SetBytes(payload[96:128])
	amountInMax := new(big.Int).SetBytes(payload[128:160])

	pathBytes, ok := readBytesAt(payload, pathOffset)
	if !ok || len(pathBytes) < 40 {
		return nil
	}

	tokenOut, tokenIn, fee := parseUniswapV3Path(pathBytes)

	swap := &SwapCall{
		Selector:  selectors.UniswapV3ExactOutput,
		Protocol:  defaultProtocol(contextProtocol(ctx), "UniswapV3"),
		TokenIn:   tokenIn,
		TokenOut:  tokenOut,
		Recipient: recipient,
		Deadline:  deadline,
		AmountIn:  amountInMax,
		AmountOut: amountOut,
		Fee:       fee,
	}
	swap.Factory = common.HexToAddress("0x1F98431c8aD98523631AE4a59f267346ea31F984")
	swap.ensurePoolAddress()
	return swap
}

func decodeExactOutputSingle(payload []byte, ctx *MulticallContext) *SwapCall {
	if len(payload) < 256 {
		return nil
	}

	tokenIn := common.BytesToAddress(payload[12:32])
	tokenOut := common.BytesToAddress(payload[44:64])
	fee := binary.BigEndian.Uint32(append(make([]byte, 1), payload[93:96]...))
	recipient := common.BytesToAddress(payload[108:128])
	deadline := new(big.Int).SetBytes(payload[128:160])
	amountOut := new(big.Int).SetBytes(payload[160:192])
	amountInMax := new(big.Int).SetBytes(payload[192:224])

	swap := &SwapCall{
		Selector:  selectors.UniswapV3ExactOutputSingle,
		Protocol:  defaultProtocol(contextProtocol(ctx), "UniswapV3"),
		TokenIn:   tokenIn,
		TokenOut:  tokenOut,
		Recipient: recipient,
		Deadline:  deadline,
		AmountIn:  amountInMax,
		AmountOut: amountOut,
		Fee:       uint32(fee),
		Path:      []common.Address{tokenIn, tokenOut},
	}

	swap.Factory = common.HexToAddress("0x1F98431c8aD98523631AE4a59f267346ea31F984")
	swap.ensurePoolAddress()
	return swap
}

func decodeUniswapV2Swap(selector string, payload []byte, ctx *MulticallContext) *SwapCall {
	if len(payload) < 160 {
		return nil
	}

	pathOffset, ok := readInt(payload[64:96])
	if !ok {
		return nil
	}

	path, ok := readAddressArray(payload, pathOffset)
	if !ok || len(path) < 2 {
		return nil
	}

	tokenIn := path[0]
	tokenOut := path[len(path)-1]
	protocol := defaultProtocol(contextProtocol(ctx), "UniswapV2")

	amountA := new(big.Int).SetBytes(payload[0:32])
	amountB := new(big.Int).SetBytes(payload[32:64])

	swap := &SwapCall{
		Selector: selector,
		Protocol: protocol,
		TokenIn:  tokenIn,
		TokenOut: tokenOut,
		Path:     path,
	}

	switch selector {
	case normalizedSelector(selectors.UniswapV2SwapExactTokensForTokens),
		normalizedSelector(selectors.UniswapV2SwapExactETHForTokens),
		normalizedSelector(selectors.UniswapV2SwapExactTokensForTokensSupportingFee),
		normalizedSelector(selectors.UniswapV2SwapExactTokensForTokensSupportingFeeLegacy),
		normalizedSelector(selectors.UniswapV2SwapExactETHForTokensSupportingFee),
		normalizedSelector(selectors.UniswapV2SwapExactTokensForETHSupportingFee):
		swap.AmountIn = amountA
		swap.AmountOutMinimum = amountB
	case normalizedSelector(selectors.UniswapV2SwapTokensForExactTokens),
		normalizedSelector(selectors.UniswapV2SwapTokensForExactETH),
		normalizedSelector(selectors.UniswapV2SwapETHForExactTokens):
		swap.AmountOut = amountA
		swap.AmountIn = amountB
	default:
		swap.AmountIn = amountA
		swap.AmountOut = amountB
	}

	swap.Recipient = common.BytesToAddress(payload[96+12 : 128])
	swap.Deadline = new(big.Int).SetBytes(payload[128:160])

	if strings.Contains(strings.ToLower(protocol), "sushi") {
		swap.Factory = common.HexToAddress("0xC0AEe478e3658e2610c5F7A4A2E1777cE9e4f2Ac")
	} else {
		// Default to canonical Arbitrum Uniswap V2 factory (f1d7cc...) set in parser.
		swap.Factory = common.HexToAddress("0xf1D7CC64Fb4452F05c498126312eBE29f30Fbcf9")
	}

	swap.ensureV2PoolAddress()
	return swap
}

func decodePositionManagerMint(payload []byte, ctx *MulticallContext) *SwapCall {
	if len(payload) < 320 {
		return nil
	}

	paramsOffset, ok := readInt(payload[0:32])
	if !ok {
		return nil
	}

	paramsStart := paramsOffset
	if paramsStart+352 > len(payload) {
		return nil
	}
	params := payload[paramsStart : paramsStart+352]

	token0 := common.BytesToAddress(params[12:32])
	token1 := common.BytesToAddress(params[44:64])
	fee := binary.BigEndian.Uint32(append(make([]byte, 1), params[93:96]...))
	amount0Desired := new(big.Int).SetBytes(params[160:192])
	amount1Desired := new(big.Int).SetBytes(params[192:224])
	recipient := common.BytesToAddress(params[276:296])
	deadline := new(big.Int).SetBytes(params[296:328])

	swap := &SwapCall{
		Selector:  selectors.NonfungiblePositionManagerMint,
		Protocol:  defaultProtocol(contextProtocol(ctx), "UniswapV3"),
		TokenIn:   token0,
		TokenOut:  token1,
		Fee:       fee,
		AmountIn:  amount0Desired,
		AmountOut: amount1Desired,
		Recipient: recipient,
		Deadline:  deadline,
	}
	swap.Factory = common.HexToAddress("0x1F98431c8aD98523631AE4a59f267346ea31F984")
	swap.ensurePoolAddress()
	return swap
}

func (sc *SwapCall) ensurePoolAddress() {
	if sc.PoolAddress != (common.Address{}) {
		return
	}

	if sc.Factory == (common.Address{}) || sc.TokenIn == (common.Address{}) || sc.TokenOut == (common.Address{}) {
		return
	}

	fee := int64(sc.Fee)
	if fee == 0 {
		fee = 3000
	}
	sc.PoolAddress = uniswap.CalculatePoolAddress(sc.Factory, sc.TokenIn, sc.TokenOut, fee)
}

func (sc *SwapCall) ensureV2PoolAddress() {
	if sc.PoolAddress != (common.Address{}) {
		return
	}
	if sc.Factory == (common.Address{}) || sc.TokenIn == (common.Address{}) || sc.TokenOut == (common.Address{}) {
		return
	}

	token0 := sc.TokenIn
	token1 := sc.TokenOut
	if token0.Big().Cmp(token1.Big()) > 0 {
		token0, token1 = token1, token0
	}

	keccakInput := append(token0.Bytes(), token1.Bytes()...)
	salt := crypto.Keccak256(keccakInput)
	initCodeHash := common.HexToHash("0x96e8ac4277198ff8b6f785478aa9a39f403cb768dd02cbee326c3e7da348845f")

	data := make([]byte, 0, 85)
	data = append(data, 0xff)
	data = append(data, sc.Factory.Bytes()...)
	data = append(data, salt...)
	data = append(data, initCodeHash.Bytes()...)

	hash := crypto.Keccak256(data)
	var addr common.Address
	copy(addr[:], hash[12:])
	sc.PoolAddress = addr
}

func markNested(calls []*SwapCall) {
	for _, c := range calls {
		if c != nil {
			c.nested = true
		}
	}
}

func contextProtocol(ctx *MulticallContext) string {
	if ctx == nil {
		return ""
	}
	return ctx.Protocol
}

func defaultProtocol(primary, fallback string) string {
	if strings.TrimSpace(primary) != "" {
		return primary
	}
	return fallback
}

func parseUniswapV3Path(path []byte) (common.Address, common.Address, uint32) {
	if len(path) < 40 {
		return common.Address{}, common.Address{}, 0
	}

	tokenIn := common.BytesToAddress(path[:20])
	tokenOut := common.BytesToAddress(path[len(path)-20:])
	fee := uint32(0)
	if len(path) >= 23 {
		feeBytes := path[20:23]
		fee = uint32(feeBytes[0])<<16 | uint32(feeBytes[1])<<8 | uint32(feeBytes[2])
	}
	return tokenIn, tokenOut, fee
}

func readInt(word []byte) (int, bool) {
	if len(word) != 32 {
		return 0, false
	}
	val := new(big.Int).SetBytes(word)
	if !val.IsUint64() {
		return 0, false
	}
	return safeConvertUint64ToInt(val.Uint64()), true
}

func readBytesAt(payload []byte, offset int) ([]byte, bool) {
	cur := offset
	for depth := 0; depth < 4; depth++ {
		if cur < 0 || cur+32 > len(payload) {
			return nil, false
		}

		word := new(big.Int).SetBytes(payload[cur : cur+32])
		if !word.IsUint64() {
			return nil, false
		}
		val := safeConvertUint64ToInt(word.Uint64())

		// Attempt to treat the value as a pointer to the actual data block.
		if val > 0 {
			offsets := []int{}
			candidate := val + cur
			if candidate >= 0 {
				offsets = append(offsets, candidate)
			}
			offsets = append(offsets, val)
			followed := false
			for _, ptr := range offsets {
				if ptr < 0 || ptr+32 > len(payload) {
					continue
				}
				lengthWord := new(big.Int).SetBytes(payload[ptr : ptr+32])
				if !lengthWord.IsUint64() {
					continue
				}
				size := safeConvertUint64ToInt(lengthWord.Uint64())
				start := ptr + 32
				end := start + size
				if size >= 0 && end <= len(payload) {
					return payload[start:end], true
				}
				cur = ptr
				followed = true
				break
			}
			if followed {
				continue
			}
		}

		// Fallback: treat the value as the length relative to the current offset.
		size := val
		start := cur + 32
		end := start + size
		if size >= 0 && end <= len(payload) {
			return payload[start:end], true
		}

		if val == cur {
			break
		}
		cur = val
	}

	return nil, false
}

func readBytesArrayAt(payload []byte, offset int) ([][]byte, bool) {
	if offset < 0 || offset+32 > len(payload) {
		return nil, false
	}
	length := new(big.Int).SetBytes(payload[offset : offset+32])
	if !length.IsUint64() {
		return nil, false
	}
	count := safeConvertUint64ToInt(length.Uint64())
	result := make([][]byte, 0, count)

	for i := 0; i < count; i++ {
		entryOffsetWord := payload[offset+32+i*32 : offset+32+(i+1)*32]
		entryOffset, ok := readInt(entryOffsetWord)
		if !ok {
			return nil, false
		}
		start := offset + entryOffset
		entry, ok := readBytesAt(payload, start)
		if !ok {
			return nil, false
		}
		result = append(result, entry)
	}

	return result, true
}

func readAddressArray(payload []byte, offset int) ([]common.Address, bool) {
	if offset < 0 || offset+32 > len(payload) {
		return nil, false
	}
	length := new(big.Int).SetBytes(payload[offset : offset+32])
	if !length.IsUint64() {
		return nil, false
	}
	count := safeConvertUint64ToInt(length.Uint64())
	start := offset + 32
	end := start + count*32
	if count <= 0 || end > len(payload) {
		return nil, false
	}

	addresses := make([]common.Address, 0, count)
	for i := 0; i < count; i++ {
		word := payload[start+i*32 : start+(i+1)*32]
		addresses = append(addresses, common.BytesToAddress(word[12:]))
	}
	return addresses, true
}

func (sc *SwapCall) String() string {
	return fmt.Sprintf("%s %s->%s selector=%s", sc.Protocol, sc.TokenIn.Hex(), sc.TokenOut.Hex(), sc.Selector)
}