package fault

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

	"github.com/ethereum-optimism/optimism/op-challenger/game/fault/types"

	"github.com/ethereum/go-ethereum/accounts/abi/bind"
	"github.com/ethereum/go-ethereum/common"
	"github.com/stretchr/testify/require"
)

var (
	mockClaimDataError    = fmt.Errorf("claim data errored")
	mockClaimLenError     = fmt.Errorf("claim len errored")
	mockMaxGameDepthError = fmt.Errorf("max game depth errored")
	mockPrestateError     = fmt.Errorf("prestate errored")
	mockStatusError       = fmt.Errorf("status errored")
)

// TestLoader_GetGameStatus tests fetching the game status.
func TestLoader_GetGameStatus(t *testing.T) {
	tests := []struct {
		name          string
		status        uint8
		expectedError bool
	}{
		{
			name:   "challenger won status",
			status: uint8(types.GameStatusChallengerWon),
		},
		{
			name:   "defender won status",
			status: uint8(types.GameStatusDefenderWon),
		},
		{
			name:   "in progress status",
			status: uint8(types.GameStatusInProgress),
		},
		{
			name:          "error bubbled up",
			expectedError: true,
		},
	}

	for _, test := range tests {
		t.Run(test.name, func(t *testing.T) {
			mockCaller := newMockCaller()
			mockCaller.status = test.status
			mockCaller.statusError = test.expectedError
			loader := NewLoader(mockCaller)
			status, err := loader.GetGameStatus(context.Background())
			if test.expectedError {
				require.ErrorIs(t, err, mockStatusError)
			} else {
				require.NoError(t, err)
				require.Equal(t, types.GameStatus(test.status), status)
			}
		})
	}
}

// TestLoader_FetchGameDepth tests fetching the game depth.
func TestLoader_FetchGameDepth(t *testing.T) {
	t.Run("Succeeds", func(t *testing.T) {
		mockCaller := newMockCaller()
		mockCaller.maxGameDepth = 10
		loader := NewLoader(mockCaller)
		depth, err := loader.FetchGameDepth(context.Background())
		require.NoError(t, err)
		require.Equal(t, uint64(10), depth)
	})

	t.Run("Errors", func(t *testing.T) {
		mockCaller := newMockCaller()
		mockCaller.maxGameDepthError = true
		loader := NewLoader(mockCaller)
		depth, err := loader.FetchGameDepth(context.Background())
		require.ErrorIs(t, mockMaxGameDepthError, err)
		require.Equal(t, depth, uint64(0))
	})
}

// TestLoader_FetchAbsolutePrestateHash tests fetching the absolute prestate hash.
func TestLoader_FetchAbsolutePrestateHash(t *testing.T) {
	t.Run("Succeeds", func(t *testing.T) {
		mockCaller := newMockCaller()
		loader := NewLoader(mockCaller)
		prestate, err := loader.FetchAbsolutePrestateHash(context.Background())
		require.NoError(t, err)
		require.ElementsMatch(t, common.HexToHash("0xdEad"), prestate)
	})

	t.Run("Errors", func(t *testing.T) {
		mockCaller := newMockCaller()
		mockCaller.prestateError = true
		loader := NewLoader(mockCaller)
		prestate, err := loader.FetchAbsolutePrestateHash(context.Background())
		require.Error(t, err)
		require.ElementsMatch(t, common.Hash{}, prestate)
	})
}

// TestLoader_FetchClaims tests fetching claims.
func TestLoader_FetchClaims(t *testing.T) {
	t.Run("Succeeds", func(t *testing.T) {
		mockCaller := newMockCaller()
		expectedClaims := mockCaller.returnClaims
		loader := NewLoader(mockCaller)
		claims, err := loader.FetchClaims(context.Background())
		require.NoError(t, err)
		require.ElementsMatch(t, []types.Claim{
			{
				ClaimData: types.ClaimData{
					Value:    expectedClaims[0].Claim,
					Position: types.NewPositionFromGIndex(expectedClaims[0].Position.Uint64()),
				},
				Parent: types.ClaimData{
					Value:    expectedClaims[0].Claim,
					Position: types.NewPositionFromGIndex(expectedClaims[0].Position.Uint64()),
				},
				Countered:     false,
				Clock:         uint64(0),
				ContractIndex: 0,
			},
			{
				ClaimData: types.ClaimData{
					Value:    expectedClaims[1].Claim,
					Position: types.NewPositionFromGIndex(expectedClaims[1].Position.Uint64()),
				},
				Parent: types.ClaimData{
					Value:    expectedClaims[0].Claim,
					Position: types.NewPositionFromGIndex(expectedClaims[1].Position.Uint64()),
				},
				Countered:     false,
				Clock:         uint64(0),
				ContractIndex: 1,
			},
			{
				ClaimData: types.ClaimData{
					Value:    expectedClaims[2].Claim,
					Position: types.NewPositionFromGIndex(expectedClaims[2].Position.Uint64()),
				},
				Parent: types.ClaimData{
					Value:    expectedClaims[0].Claim,
					Position: types.NewPositionFromGIndex(expectedClaims[2].Position.Uint64()),
				},
				Countered:     false,
				Clock:         uint64(0),
				ContractIndex: 2,
			},
		}, claims)
	})

	t.Run("Claim Data Errors", func(t *testing.T) {
		mockCaller := newMockCaller()
		mockCaller.claimDataError = true
		loader := NewLoader(mockCaller)
		claims, err := loader.FetchClaims(context.Background())
		require.ErrorIs(t, err, mockClaimDataError)
		require.Empty(t, claims)
	})

	t.Run("Claim Len Errors", func(t *testing.T) {
		mockCaller := newMockCaller()
		mockCaller.claimLenError = true
		loader := NewLoader(mockCaller)
		claims, err := loader.FetchClaims(context.Background())
		require.ErrorIs(t, err, mockClaimLenError)
		require.Empty(t, claims)
	})
}

type mockCaller struct {
	claimDataError    bool
	claimLenError     bool
	maxGameDepthError bool
	prestateError     bool
	statusError       bool
	maxGameDepth      uint64
	currentIndex      uint64
	status            uint8
	returnClaims      []struct {
		ParentIndex uint32
		Countered   bool
		Claim       [32]byte
		Position    *big.Int
		Clock       *big.Int
	}
}

func newMockCaller() *mockCaller {
	return &mockCaller{
		returnClaims: []struct {
			ParentIndex uint32
			Countered   bool
			Claim       [32]byte
			Position    *big.Int
			Clock       *big.Int
		}{
			{
				Claim:     [32]byte{0x00},
				Position:  big.NewInt(0),
				Countered: false,
				Clock:     big.NewInt(0),
			},
			{
				Claim:     [32]byte{0x01},
				Position:  big.NewInt(0),
				Countered: false,
				Clock:     big.NewInt(0),
			},
			{
				Claim:     [32]byte{0x02},
				Position:  big.NewInt(0),
				Countered: false,
				Clock:     big.NewInt(0),
			},
		},
	}
}

func (m *mockCaller) ClaimData(opts *bind.CallOpts, arg0 *big.Int) (struct {
	ParentIndex uint32
	Countered   bool
	Claim       [32]byte
	Position    *big.Int
	Clock       *big.Int
}, error) {
	if m.claimDataError {
		return struct {
			ParentIndex uint32
			Countered   bool
			Claim       [32]byte
			Position    *big.Int
			Clock       *big.Int
		}{}, mockClaimDataError
	}
	returnClaim := m.returnClaims[m.currentIndex]
	m.currentIndex++
	return returnClaim, nil
}

func (m *mockCaller) Status(opts *bind.CallOpts) (uint8, error) {
	if m.statusError {
		return 0, mockStatusError
	}
	return m.status, nil
}

func (m *mockCaller) ClaimDataLen(opts *bind.CallOpts) (*big.Int, error) {
	if m.claimLenError {
		return big.NewInt(0), mockClaimLenError
	}
	return big.NewInt(int64(len(m.returnClaims))), nil
}

func (m *mockCaller) MAXGAMEDEPTH(opts *bind.CallOpts) (*big.Int, error) {
	if m.maxGameDepthError {
		return nil, mockMaxGameDepthError
	}
	return big.NewInt(int64(m.maxGameDepth)), nil
}

func (m *mockCaller) ABSOLUTEPRESTATE(opts *bind.CallOpts) ([32]byte, error) {
	if m.prestateError {
		return [32]byte{}, mockPrestateError
	}
	return common.HexToHash("0xdEad"), nil
}
