package calldata

import (
	"encoding/hex"
	"encoding/json"
	"os"
	"path/filepath"
	"strings"
	"testing"
)

type payloadFixture struct {
	Protocol    string `json:"protocol"`
	Function    string `json:"function"`
	FunctionSig string `json:"function_sig"`
	InputData   string `json:"input_data"`
}

func loadPayload(t *testing.T, name string) payloadFixture {
	t.Helper()
	fullPath := filepath.Join("testdata", "payloads", name)
	raw, err := os.ReadFile(fullPath)
	if err != nil {
		t.Fatalf("failed to read payload fixture %s: %v", name, err)
	}
	var pf payloadFixture
	if err := json.Unmarshal(raw, &pf); err != nil {
		t.Fatalf("failed to unmarshal payload %s: %v", name, err)
	}
	return pf
}

func decodeDirect(raw []byte, ctx *MulticallContext) []*SwapCall {
	validator := getAddressValidator()
	return decodeSwapCallRecursive(raw, ctx, validator, 0)
}

func TestCapturedPayloadDecoding(t *testing.T) {
	cases := []struct {
		name           string
		fixture        string
		expectSwaps    int
		expectSelector string
		tokenIn        string
		tokenOut       string
		verifyProtocol string
		isMulticall    bool
	}{
		{
			name:           "uniswap_v3_exact_output_single",
			fixture:        "uniswapv3_exact_output_single.json",
			expectSwaps:    1,
			expectSelector: "db3e2198",
			tokenIn:        "0xff970a61a04b1ca14834a43f5de4533ebddb5cc8",
			tokenOut:       "0x912ce59144191c1204e64559fe8253a0e49e6548",
			verifyProtocol: "UniswapV3",
		},
		{
			name:           "uniswap_v3_exact_input_single",
			fixture:        "uniswapv3_exact_input_single.json",
			expectSwaps:    1,
			expectSelector: "414bf389",
			tokenIn:        "0x82af49447d8a07e3bd95bd0d56f35241523fbab1",
			tokenOut:       "0x440017a1b021006d556d7fc06a54c32e42eb745b",
			verifyProtocol: "UniswapV3",
		},
		{
			name:           "uniswap_v2_swap_exact_tokens",
			fixture:        "uniswapv2_exact_tokens.json",
			expectSwaps:    1,
			expectSelector: "38ed1739",
			tokenIn:        "0x03f6921f6e948016631ce796331294d5a863a9ee",
			tokenOut:       "0xdcc9691793633176acf5cfdc1a658cb3b982e2fb",
			verifyProtocol: "UniswapV2",
		},
		{
			name:        "multicall_without_recognised_swaps",
			fixture:     "multicall_uniswap.json",
			expectSwaps: 0,
			isMulticall: true,
		},
		{
			name:        "uniswap_v3_decrease_liquidity",
			fixture:     "uniswapv3_decrease_liquidity.json",
			expectSwaps: 0,
		},
	}

	for _, tc := range cases {
		t.Run(tc.name, func(t *testing.T) {
			payload := loadPayload(t, tc.fixture)
			raw, err := hex.DecodeString(strings.TrimPrefix(payload.InputData, "0x"))
			if err != nil {
				t.Fatalf("failed to decode input data: %v", err)
			}
			if len(raw) < 4 {
				t.Fatalf("payload too short: %d bytes", len(raw))
			}

			ctx := &MulticallContext{Protocol: payload.Protocol}
			var swaps []*SwapCall
			if tc.isMulticall {
				swaps, err = DecodeSwapCallsFromMulticall(raw[4:], ctx)
				if err != nil {
					t.Fatalf("multicall decode failed: %v", err)
				}
			} else {
				swaps = decodeDirect(raw, ctx)
			}

			if len(swaps) != tc.expectSwaps {
				selector := strings.ToLower(hex.EncodeToString(raw[:4]))
				if !tc.isMulticall {
					// attempt direct decode based on selector for diagnostics
					var diag *SwapCall
					switch selector {
					case "414bf389":
						diag = decodeExactInputSingle(raw[4:], ctx)
					case "db3e2198":
						diag = decodeExactInput(raw[4:], ctx)
					case "38ed1739":
						diag = decodeUniswapV2Swap(selector, raw[4:], ctx)
					}
					if diag != nil {
						t.Fatalf("expected %d swaps, got %d (selector=%s, diag=%s)", tc.expectSwaps, len(swaps), selector, diag.String())
					}
				}
				t.Fatalf("expected %d swaps, got %d (selector=%s)", tc.expectSwaps, len(swaps), selector)
			}

			if tc.expectSwaps == 0 {
				return
			}

			swap := swaps[0]
			if !selectorsMatch(swap.Selector, tc.expectSelector) {
				t.Fatalf("expected selector %s, got %s", tc.expectSelector, swap.Selector)
			}
			if !strings.EqualFold(swap.TokenIn.Hex(), tc.tokenIn) {
				t.Fatalf("expected tokenIn %s, got %s", tc.tokenIn, swap.TokenIn.Hex())
			}
			if !strings.EqualFold(swap.TokenOut.Hex(), tc.tokenOut) {
				t.Fatalf("expected tokenOut %s, got %s", tc.tokenOut, swap.TokenOut.Hex())
			}
			if tc.verifyProtocol != "" && !strings.EqualFold(swap.Protocol, tc.verifyProtocol) {
				t.Fatalf("expected protocol %s, got %s", tc.verifyProtocol, swap.Protocol)
			}

			if selectorEquals(tc.expectSelector, "db3e2198") {
				if swap.AmountOut == nil || swap.AmountOut.Sign() == 0 {
					t.Fatalf("expected non-zero amountOut for exactOutputSingle")
				}
			}

			if selectorEquals(tc.expectSelector, "414bf389") || selectorEquals(tc.expectSelector, "38ed1739") {
				if swap.AmountIn == nil || swap.AmountIn.Sign() == 0 {
					t.Fatalf("expected non-zero amountIn for selector %s", tc.expectSelector)
				}
			}
		})
	}
}

func normalizeSelectorHex(sel string) string {
	s := strings.TrimSpace(strings.ToLower(sel))
	return strings.TrimPrefix(s, "0x")
}

func selectorEquals(a, b string) bool {
	return normalizeSelectorHex(a) == normalizeSelectorHex(b)
}

func selectorsMatch(actual, expected string) bool {
	return selectorEquals(actual, expected)
}