package light_test

import (
	"context"
	"errors"
	"fmt"
	"sync"
	"testing"
	"time"

	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/mock"
	"github.com/stretchr/testify/require"
	dbm "github.com/tendermint/tm-db"

	"github.com/tendermint/tendermint/internal/test/factory"
	"github.com/tendermint/tendermint/libs/log"
	"github.com/tendermint/tendermint/light"
	"github.com/tendermint/tendermint/light/provider"
	provider_mocks "github.com/tendermint/tendermint/light/provider/mocks"
	dbs "github.com/tendermint/tendermint/light/store/db"
	"github.com/tendermint/tendermint/types"
)

const (
	chainID = "test"
)

var (
	keys     = genPrivKeys(4)
	vals     = keys.ToValidators(20, 10)
	bTime, _ = time.Parse(time.RFC3339, "2006-01-02T15:04:05Z")
	h1       = keys.GenSignedHeader(chainID, 1, bTime, nil, vals, vals,
		hash("app_hash"), hash("cons_hash"), hash("results_hash"), 0, len(keys))
	// 3/3 signed
	h2 = keys.GenSignedHeaderLastBlockID(chainID, 2, bTime.Add(30*time.Minute), nil, vals, vals,
		hash("app_hash"), hash("cons_hash"), hash("results_hash"), 0, len(keys), types.BlockID{Hash: h1.Hash()})
	// 3/3 signed
	h3 = keys.GenSignedHeaderLastBlockID(chainID, 3, bTime.Add(1*time.Hour), nil, vals, vals,
		hash("app_hash"), hash("cons_hash"), hash("results_hash"), 0, len(keys), types.BlockID{Hash: h2.Hash()})
	trustPeriod  = 4 * time.Hour
	trustOptions = light.TrustOptions{
		Period: 4 * time.Hour,
		Height: 1,
		Hash:   h1.Hash(),
	}
	valSet = map[int64]*types.ValidatorSet{
		1: vals,
		2: vals,
		3: vals,
		4: vals,
	}
	headerSet = map[int64]*types.SignedHeader{
		1: h1,
		// interim header (3/3 signed)
		2: h2,
		// last header (3/3 signed)
		3: h3,
	}
	l1 = &types.LightBlock{SignedHeader: h1, ValidatorSet: vals}
	l2 = &types.LightBlock{SignedHeader: h2, ValidatorSet: vals}
	l3 = &types.LightBlock{SignedHeader: h3, ValidatorSet: vals}
)

func TestValidateTrustOptions(t *testing.T) {
	testCases := []struct {
		err bool
		to  light.TrustOptions
	}{
		{
			false,
			trustOptions,
		},
		{
			true,
			light.TrustOptions{
				Period: -1 * time.Hour,
				Height: 1,
				Hash:   h1.Hash(),
			},
		},
		{
			true,
			light.TrustOptions{
				Period: 1 * time.Hour,
				Height: 0,
				Hash:   h1.Hash(),
			},
		},
		{
			true,
			light.TrustOptions{
				Period: 1 * time.Hour,
				Height: 1,
				Hash:   []byte("incorrect hash"),
			},
		},
	}

	for _, tc := range testCases {
		err := tc.to.ValidateBasic()
		if tc.err {
			assert.Error(t, err)
		} else {
			assert.NoError(t, err)
		}
	}

}

func TestClient_SequentialVerification(t *testing.T) {
	newKeys := genPrivKeys(4)
	newVals := newKeys.ToValidators(10, 1)
	differentVals, _ := factory.RandValidatorSet(10, 100)

	testCases := []struct {
		name         string
		otherHeaders map[int64]*types.SignedHeader // all except ^
		vals         map[int64]*types.ValidatorSet
		initErr      bool
		verifyErr    bool
	}{
		{
			"good",
			headerSet,
			valSet,
			false,
			false,
		},
		{
			"bad: different first header",
			map[int64]*types.SignedHeader{
				// different header
				1: keys.GenSignedHeader(chainID, 1, bTime.Add(1*time.Hour), nil, vals, vals,
					hash("app_hash"), hash("cons_hash"), hash("results_hash"), 0, len(keys)),
			},
			map[int64]*types.ValidatorSet{
				1: vals,
			},
			true,
			false,
		},
		{
			"bad: no first signed header",
			map[int64]*types.SignedHeader{},
			map[int64]*types.ValidatorSet{
				1: differentVals,
			},
			true,
			true,
		},
		{
			"bad: different first validator set",
			map[int64]*types.SignedHeader{
				1: h1,
			},
			map[int64]*types.ValidatorSet{
				1: differentVals,
			},
			true,
			true,
		},
		{
			"bad: 1/3 signed interim header",
			map[int64]*types.SignedHeader{
				// trusted header
				1: h1,
				// interim header (1/3 signed)
				2: keys.GenSignedHeader(chainID, 2, bTime.Add(1*time.Hour), nil, vals, vals,
					hash("app_hash"), hash("cons_hash"), hash("results_hash"), len(keys)-1, len(keys)),
				// last header (3/3 signed)
				3: keys.GenSignedHeader(chainID, 3, bTime.Add(2*time.Hour), nil, vals, vals,
					hash("app_hash"), hash("cons_hash"), hash("results_hash"), 0, len(keys)),
			},
			valSet,
			false,
			true,
		},
		{
			"bad: 1/3 signed last header",
			map[int64]*types.SignedHeader{
				// trusted header
				1: h1,
				// interim header (3/3 signed)
				2: keys.GenSignedHeader(chainID, 2, bTime.Add(1*time.Hour), nil, vals, vals,
					hash("app_hash"), hash("cons_hash"), hash("results_hash"), 0, len(keys)),
				// last header (1/3 signed)
				3: keys.GenSignedHeader(chainID, 3, bTime.Add(2*time.Hour), nil, vals, vals,
					hash("app_hash"), hash("cons_hash"), hash("results_hash"), len(keys)-1, len(keys)),
			},
			valSet,
			false,
			true,
		},
		{
			"bad: different validator set at height 3",
			headerSet,
			map[int64]*types.ValidatorSet{
				1: vals,
				2: vals,
				3: newVals,
			},
			false,
			true,
		},
	}

	for _, tc := range testCases {
		testCase := tc
		t.Run(testCase.name, func(t *testing.T) {
			ctx, cancel := context.WithCancel(context.Background())
			defer cancel()

			logger := log.NewTestingLogger(t)

			mockNode := mockNodeFromHeadersAndVals(testCase.otherHeaders, testCase.vals)
			mockNode.On("LightBlock", mock.Anything, mock.Anything).Return(nil, provider.ErrLightBlockNotFound)
			c, err := light.NewClient(
				ctx,
				chainID,
				trustOptions,
				mockNode,
				[]provider.Provider{mockNode},
				dbs.New(dbm.NewMemDB()),
				light.SequentialVerification(),
				light.Logger(logger),
			)

			if testCase.initErr {
				require.Error(t, err)
				return
			}

			require.NoError(t, err)

			_, err = c.VerifyLightBlockAtHeight(ctx, 3, bTime.Add(3*time.Hour))
			if testCase.verifyErr {
				assert.Error(t, err)
			} else {
				assert.NoError(t, err)
			}
			mockNode.AssertExpectations(t)
		})
	}
}

func TestClient_SkippingVerification(t *testing.T) {
	// required for 2nd test case
	newKeys := genPrivKeys(4)
	newVals := newKeys.ToValidators(10, 1)

	// 1/3+ of vals, 2/3- of newVals
	transitKeys := keys.Extend(3)
	transitVals := transitKeys.ToValidators(10, 1)

	testCases := []struct {
		name         string
		otherHeaders map[int64]*types.SignedHeader // all except ^
		vals         map[int64]*types.ValidatorSet
		initErr      bool
		verifyErr    bool
	}{
		{
			"good",
			map[int64]*types.SignedHeader{
				// trusted header
				1: h1,
				// last header (3/3 signed)
				3: h3,
			},
			valSet,
			false,
			false,
		},
		{
			"good, but val set changes by 2/3 (1/3 of vals is still present)",
			map[int64]*types.SignedHeader{
				// trusted header
				1: h1,
				3: transitKeys.GenSignedHeader(chainID, 3, bTime.Add(2*time.Hour), nil, transitVals, transitVals,
					hash("app_hash"), hash("cons_hash"), hash("results_hash"), 0, len(transitKeys)),
			},
			map[int64]*types.ValidatorSet{
				1: vals,
				2: vals,
				3: transitVals,
			},
			false,
			false,
		},
		{
			"good, but val set changes 100% at height 2",
			map[int64]*types.SignedHeader{
				// trusted header
				1: h1,
				// interim header (3/3 signed)
				2: keys.GenSignedHeader(chainID, 2, bTime.Add(1*time.Hour), nil, vals, newVals,
					hash("app_hash"), hash("cons_hash"), hash("results_hash"), 0, len(keys)),
				// last header (0/4 of the original val set signed)
				3: newKeys.GenSignedHeader(chainID, 3, bTime.Add(2*time.Hour), nil, newVals, newVals,
					hash("app_hash"), hash("cons_hash"), hash("results_hash"), 0, len(newKeys)),
			},
			map[int64]*types.ValidatorSet{
				1: vals,
				2: vals,
				3: newVals,
			},
			false,
			false,
		},
		{
			"bad: last header signed by newVals, interim header has no signers",
			map[int64]*types.SignedHeader{
				// trusted header
				1: h1,
				// last header (0/4 of the original val set signed)
				2: keys.GenSignedHeader(chainID, 2, bTime.Add(1*time.Hour), nil, vals, newVals,
					hash("app_hash"), hash("cons_hash"), hash("results_hash"), 0, 0),
				// last header (0/4 of the original val set signed)
				3: newKeys.GenSignedHeader(chainID, 3, bTime.Add(2*time.Hour), nil, newVals, newVals,
					hash("app_hash"), hash("cons_hash"), hash("results_hash"), 0, len(newKeys)),
			},
			map[int64]*types.ValidatorSet{
				1: vals,
				2: vals,
				3: newVals,
			},
			false,
			true,
		},
	}

	bctx, bcancel := context.WithCancel(context.Background())
	defer bcancel()

	for _, tc := range testCases {
		tc := tc
		t.Run(tc.name, func(t *testing.T) {
			ctx, cancel := context.WithCancel(bctx)
			defer cancel()
			logger := log.NewTestingLogger(t)

			mockNode := mockNodeFromHeadersAndVals(tc.otherHeaders, tc.vals)
			mockNode.On("LightBlock", mock.Anything, mock.Anything).Return(nil, provider.ErrLightBlockNotFound)
			c, err := light.NewClient(
				ctx,
				chainID,
				trustOptions,
				mockNode,
				[]provider.Provider{mockNode},
				dbs.New(dbm.NewMemDB()),
				light.SkippingVerification(light.DefaultTrustLevel),
				light.Logger(logger),
			)
			if tc.initErr {
				require.Error(t, err)
				return
			}

			require.NoError(t, err)

			_, err = c.VerifyLightBlockAtHeight(ctx, 3, bTime.Add(3*time.Hour))
			if tc.verifyErr {
				assert.Error(t, err)
			} else {
				assert.NoError(t, err)
			}
		})
	}

}

// start from a large light block to make sure that the pivot height doesn't select a height outside
// the appropriate range
func TestClientLargeBisectionVerification(t *testing.T) {
	numBlocks := int64(300)
	mockHeaders, mockVals, _ := genLightBlocksWithKeys(chainID, numBlocks, 101, 2, bTime)

	lastBlock := &types.LightBlock{SignedHeader: mockHeaders[numBlocks], ValidatorSet: mockVals[numBlocks]}
	mockNode := &provider_mocks.Provider{}
	mockNode.On("LightBlock", mock.Anything, numBlocks).
		Return(lastBlock, nil)

	mockNode.On("LightBlock", mock.Anything, int64(200)).
		Return(&types.LightBlock{SignedHeader: mockHeaders[200], ValidatorSet: mockVals[200]}, nil)

	mockNode.On("LightBlock", mock.Anything, int64(256)).
		Return(&types.LightBlock{SignedHeader: mockHeaders[256], ValidatorSet: mockVals[256]}, nil)

	mockNode.On("LightBlock", mock.Anything, int64(0)).Return(lastBlock, nil)

	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	trustedLightBlock, err := mockNode.LightBlock(ctx, int64(200))
	require.NoError(t, err)
	c, err := light.NewClient(
		ctx,
		chainID,
		light.TrustOptions{
			Period: 4 * time.Hour,
			Height: trustedLightBlock.Height,
			Hash:   trustedLightBlock.Hash(),
		},
		mockNode,
		[]provider.Provider{mockNode},
		dbs.New(dbm.NewMemDB()),
		light.SkippingVerification(light.DefaultTrustLevel),
	)
	require.NoError(t, err)
	h, err := c.Update(ctx, bTime.Add(300*time.Minute))
	assert.NoError(t, err)
	height, err := c.LastTrustedHeight()
	require.NoError(t, err)
	require.Equal(t, numBlocks, height)
	h2, err := mockNode.LightBlock(ctx, numBlocks)
	require.NoError(t, err)
	assert.Equal(t, h, h2)
	mockNode.AssertExpectations(t)
}

func TestClientBisectionBetweenTrustedHeaders(t *testing.T) {
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	mockFullNode := mockNodeFromHeadersAndVals(headerSet, valSet)
	c, err := light.NewClient(
		ctx,
		chainID,
		light.TrustOptions{
			Period: 4 * time.Hour,
			Height: 1,
			Hash:   h1.Hash(),
		},
		mockFullNode,
		[]provider.Provider{mockFullNode},
		dbs.New(dbm.NewMemDB()),
		light.SkippingVerification(light.DefaultTrustLevel),
	)
	require.NoError(t, err)

	_, err = c.VerifyLightBlockAtHeight(ctx, 3, bTime.Add(2*time.Hour))
	require.NoError(t, err)

	// confirm that the client already doesn't have the light block
	_, err = c.TrustedLightBlock(2)
	require.Error(t, err)

	// verify using bisection the light block between the two trusted light blocks
	_, err = c.VerifyLightBlockAtHeight(ctx, 2, bTime.Add(1*time.Hour))
	assert.NoError(t, err)
	mockFullNode.AssertExpectations(t)
}

func TestClient_Cleanup(t *testing.T) {
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	logger := log.NewTestingLogger(t)

	mockFullNode := &provider_mocks.Provider{}
	mockFullNode.On("LightBlock", mock.Anything, int64(1)).Return(l1, nil)
	c, err := light.NewClient(
		ctx,
		chainID,
		trustOptions,
		mockFullNode,
		[]provider.Provider{mockFullNode},
		dbs.New(dbm.NewMemDB()),
		light.Logger(logger),
	)
	require.NoError(t, err)
	_, err = c.TrustedLightBlock(1)
	require.NoError(t, err)

	err = c.Cleanup()
	require.NoError(t, err)

	// Check no light blocks exist after Cleanup.
	l, err := c.TrustedLightBlock(1)
	assert.Error(t, err)
	assert.Nil(t, l)
	mockFullNode.AssertExpectations(t)
}

// trustedHeader.Height == options.Height
func TestClientRestoresTrustedHeaderAfterStartup(t *testing.T) {
	bctx, bcancel := context.WithCancel(context.Background())
	defer bcancel()

	// 1. options.Hash == trustedHeader.Hash
	t.Run("hashes should match", func(t *testing.T) {
		ctx, cancel := context.WithCancel(bctx)
		defer cancel()

		logger := log.NewTestingLogger(t)

		mockNode := &provider_mocks.Provider{}
		trustedStore := dbs.New(dbm.NewMemDB())
		err := trustedStore.SaveLightBlock(l1)
		require.NoError(t, err)

		c, err := light.NewClient(
			ctx,
			chainID,
			trustOptions,
			mockNode,
			[]provider.Provider{mockNode},
			trustedStore,
			light.Logger(logger),
		)
		require.NoError(t, err)

		l, err := c.TrustedLightBlock(1)
		assert.NoError(t, err)
		assert.NotNil(t, l)
		assert.Equal(t, l.Hash(), h1.Hash())
		assert.Equal(t, l.ValidatorSet.Hash(), h1.ValidatorsHash.Bytes())
		mockNode.AssertExpectations(t)
	})

	// 2. options.Hash != trustedHeader.Hash
	t.Run("hashes should not match", func(t *testing.T) {
		ctx, cancel := context.WithCancel(bctx)
		defer cancel()

		trustedStore := dbs.New(dbm.NewMemDB())
		err := trustedStore.SaveLightBlock(l1)
		require.NoError(t, err)

		logger := log.NewTestingLogger(t)

		// header1 != h1
		header1 := keys.GenSignedHeader(chainID, 1, bTime.Add(1*time.Hour), nil, vals, vals,
			hash("app_hash"), hash("cons_hash"), hash("results_hash"), 0, len(keys))
		mockNode := &provider_mocks.Provider{}

		c, err := light.NewClient(
			ctx,
			chainID,
			light.TrustOptions{
				Period: 4 * time.Hour,
				Height: 1,
				Hash:   header1.Hash(),
			},
			mockNode,
			[]provider.Provider{mockNode},
			trustedStore,
			light.Logger(logger),
		)
		require.NoError(t, err)

		l, err := c.TrustedLightBlock(1)
		assert.NoError(t, err)
		if assert.NotNil(t, l) {
			// client take the trusted store and ignores the trusted options
			assert.Equal(t, l.Hash(), l1.Hash())
			assert.NoError(t, l.ValidateBasic(chainID))
		}
		mockNode.AssertExpectations(t)
	})
}

func TestClient_Update(t *testing.T) {
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	mockFullNode := &provider_mocks.Provider{}
	mockFullNode.On("LightBlock", mock.Anything, int64(0)).Return(l3, nil)
	mockFullNode.On("LightBlock", mock.Anything, int64(1)).Return(l1, nil)
	mockFullNode.On("LightBlock", mock.Anything, int64(3)).Return(l3, nil)

	logger := log.NewTestingLogger(t)

	c, err := light.NewClient(
		ctx,
		chainID,
		trustOptions,
		mockFullNode,
		[]provider.Provider{mockFullNode},
		dbs.New(dbm.NewMemDB()),
		light.Logger(logger),
	)
	require.NoError(t, err)

	// should result in downloading & verifying header #3
	l, err := c.Update(ctx, bTime.Add(2*time.Hour))
	assert.NoError(t, err)
	if assert.NotNil(t, l) {
		assert.EqualValues(t, 3, l.Height)
		assert.NoError(t, l.ValidateBasic(chainID))
	}
	mockFullNode.AssertExpectations(t)
}

func TestClient_Concurrency(t *testing.T) {
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	logger := log.NewTestingLogger(t)

	mockFullNode := &provider_mocks.Provider{}
	mockFullNode.On("LightBlock", mock.Anything, int64(2)).Return(l2, nil)
	mockFullNode.On("LightBlock", mock.Anything, int64(1)).Return(l1, nil)
	c, err := light.NewClient(
		ctx,
		chainID,
		trustOptions,
		mockFullNode,
		[]provider.Provider{mockFullNode},
		dbs.New(dbm.NewMemDB()),
		light.Logger(logger),
	)
	require.NoError(t, err)

	_, err = c.VerifyLightBlockAtHeight(ctx, 2, bTime.Add(2*time.Hour))
	require.NoError(t, err)

	var wg sync.WaitGroup
	for i := 0; i < 100; i++ {
		wg.Add(1)
		go func() {
			defer wg.Done()

			// NOTE: Cleanup, Stop, VerifyLightBlockAtHeight and Verify are not supposed
			// to be concurrently safe.

			assert.Equal(t, chainID, c.ChainID())

			_, err := c.LastTrustedHeight()
			assert.NoError(t, err)

			_, err = c.FirstTrustedHeight()
			assert.NoError(t, err)

			l, err := c.TrustedLightBlock(1)
			assert.NoError(t, err)
			assert.NotNil(t, l)
		}()
	}

	wg.Wait()
	mockFullNode.AssertExpectations(t)
}

func TestClient_AddProviders(t *testing.T) {
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	mockFullNode := mockNodeFromHeadersAndVals(map[int64]*types.SignedHeader{
		1: h1,
		2: h2,
	}, valSet)
	logger := log.NewTestingLogger(t)

	c, err := light.NewClient(
		ctx,
		chainID,
		trustOptions,
		mockFullNode,
		[]provider.Provider{mockFullNode},
		dbs.New(dbm.NewMemDB()),
		light.Logger(logger),
	)
	require.NoError(t, err)

	closeCh := make(chan struct{})
	go func() {
		// run verification concurrently to make sure it doesn't dead lock
		_, err = c.VerifyLightBlockAtHeight(ctx, 2, bTime.Add(2*time.Hour))
		require.NoError(t, err)
		close(closeCh)
	}()

	// NOTE: the light client doesn't check uniqueness of providers
	c.AddProvider(mockFullNode)
	require.Len(t, c.Witnesses(), 2)
	select {
	case <-closeCh:
	case <-time.After(5 * time.Second):
		t.Fatal("concurent light block verification failed to finish in 5s")
	}
	mockFullNode.AssertExpectations(t)
}

func TestClientReplacesPrimaryWithWitnessIfPrimaryIsUnavailable(t *testing.T) {
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	mockFullNode := &provider_mocks.Provider{}
	mockFullNode.On("LightBlock", mock.Anything, mock.Anything).Return(l1, nil)

	mockDeadNode := &provider_mocks.Provider{}
	mockDeadNode.On("LightBlock", mock.Anything, mock.Anything).Return(nil, provider.ErrNoResponse)

	logger := log.NewTestingLogger(t)

	c, err := light.NewClient(
		ctx,
		chainID,
		trustOptions,
		mockDeadNode,
		[]provider.Provider{mockDeadNode, mockFullNode},
		dbs.New(dbm.NewMemDB()),
		light.Logger(logger),
	)

	require.NoError(t, err)
	_, err = c.Update(ctx, bTime.Add(2*time.Hour))
	require.NoError(t, err)

	// the primary should no longer be the deadNode
	assert.NotEqual(t, c.Primary(), mockDeadNode)

	// we should still have the dead node as a witness because it
	// hasn't repeatedly been unresponsive yet
	assert.Equal(t, 2, len(c.Witnesses()))
	mockDeadNode.AssertExpectations(t)
	mockFullNode.AssertExpectations(t)
}

func TestClientReplacesPrimaryWithWitnessIfPrimaryDoesntHaveBlock(t *testing.T) {
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	mockFullNode := &provider_mocks.Provider{}
	mockFullNode.On("LightBlock", mock.Anything, mock.Anything).Return(l1, nil)

	logger := log.NewTestingLogger(t)

	mockDeadNode := &provider_mocks.Provider{}
	mockDeadNode.On("LightBlock", mock.Anything, mock.Anything).Return(nil, provider.ErrLightBlockNotFound)
	c, err := light.NewClient(
		ctx,
		chainID,
		trustOptions,
		mockDeadNode,
		[]provider.Provider{mockDeadNode, mockFullNode},
		dbs.New(dbm.NewMemDB()),
		light.Logger(logger),
	)
	require.NoError(t, err)
	_, err = c.Update(ctx, bTime.Add(2*time.Hour))
	require.NoError(t, err)

	// we should still have the dead node as a witness because it
	// hasn't repeatedly been unresponsive yet
	assert.Equal(t, 2, len(c.Witnesses()))
	mockDeadNode.AssertExpectations(t)
	mockFullNode.AssertExpectations(t)
}

func TestClient_BackwardsVerification(t *testing.T) {
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	logger := log.NewTestingLogger(t)

	{
		headers, vals, _ := genLightBlocksWithKeys(chainID, 9, 3, 0, bTime)
		delete(headers, 1)
		delete(headers, 2)
		delete(vals, 1)
		delete(vals, 2)
		mockLargeFullNode := mockNodeFromHeadersAndVals(headers, vals)
		trustHeader, _ := mockLargeFullNode.LightBlock(ctx, 6)

		c, err := light.NewClient(
			ctx,
			chainID,
			light.TrustOptions{
				Period: 4 * time.Minute,
				Height: trustHeader.Height,
				Hash:   trustHeader.Hash(),
			},
			mockLargeFullNode,
			[]provider.Provider{mockLargeFullNode},
			dbs.New(dbm.NewMemDB()),
			light.Logger(logger),
		)
		require.NoError(t, err)

		// 1) verify before the trusted header using backwards => expect no error
		h, err := c.VerifyLightBlockAtHeight(ctx, 5, bTime.Add(6*time.Minute))
		require.NoError(t, err)
		if assert.NotNil(t, h) {
			assert.EqualValues(t, 5, h.Height)
		}

		// 2) untrusted header is expired but trusted header is not => expect no error
		h, err = c.VerifyLightBlockAtHeight(ctx, 3, bTime.Add(8*time.Minute))
		assert.NoError(t, err)
		assert.NotNil(t, h)

		// 3) already stored headers should return the header without error
		h, err = c.VerifyLightBlockAtHeight(ctx, 5, bTime.Add(6*time.Minute))
		assert.NoError(t, err)
		assert.NotNil(t, h)

		// 4a) First verify latest header
		_, err = c.VerifyLightBlockAtHeight(ctx, 9, bTime.Add(9*time.Minute))
		require.NoError(t, err)

		// 4b) Verify backwards using bisection => expect no error
		_, err = c.VerifyLightBlockAtHeight(ctx, 7, bTime.Add(9*time.Minute))
		assert.NoError(t, err)
		// shouldn't have verified this header in the process
		_, err = c.TrustedLightBlock(8)
		assert.Error(t, err)

		// 5) Try bisection method, but closest header (at 7) has expired
		// so expect error
		_, err = c.VerifyLightBlockAtHeight(ctx, 8, bTime.Add(12*time.Minute))
		assert.Error(t, err)
		mockLargeFullNode.AssertExpectations(t)

	}
	{
		// 8) provides incorrect hash
		headers := map[int64]*types.SignedHeader{
			2: keys.GenSignedHeader(chainID, 2, bTime.Add(30*time.Minute), nil, vals, vals,
				hash("app_hash2"), hash("cons_hash23"), hash("results_hash30"), 0, len(keys)),
			3: h3,
		}
		vals := valSet
		mockNode := mockNodeFromHeadersAndVals(headers, vals)
		c, err := light.NewClient(
			ctx,
			chainID,
			light.TrustOptions{
				Period: 1 * time.Hour,
				Height: 3,
				Hash:   h3.Hash(),
			},
			mockNode,
			[]provider.Provider{mockNode},
			dbs.New(dbm.NewMemDB()),
			light.Logger(logger),
		)
		require.NoError(t, err)

		_, err = c.VerifyLightBlockAtHeight(ctx, 2, bTime.Add(1*time.Hour).Add(1*time.Second))
		assert.Error(t, err)
		mockNode.AssertExpectations(t)
	}
}

func TestClient_NewClientFromTrustedStore(t *testing.T) {
	// 1) Initiate DB and fill with a "trusted" header
	db := dbs.New(dbm.NewMemDB())
	err := db.SaveLightBlock(l1)
	require.NoError(t, err)
	mockNode := &provider_mocks.Provider{}

	c, err := light.NewClientFromTrustedStore(
		chainID,
		trustPeriod,
		mockNode,
		[]provider.Provider{mockNode},
		db,
	)
	require.NoError(t, err)

	// 2) Check light block exists
	h, err := c.TrustedLightBlock(1)
	assert.NoError(t, err)
	assert.EqualValues(t, l1.Height, h.Height)
	mockNode.AssertExpectations(t)
}

func TestClientRemovesWitnessIfItSendsUsIncorrectHeader(t *testing.T) {
	logger := log.NewTestingLogger(t)

	// different headers hash then primary plus less than 1/3 signed (no fork)
	headers1 := map[int64]*types.SignedHeader{
		1: h1,
		2: keys.GenSignedHeaderLastBlockID(chainID, 2, bTime.Add(30*time.Minute), nil, vals, vals,
			hash("app_hash2"), hash("cons_hash"), hash("results_hash"),
			len(keys), len(keys), types.BlockID{Hash: h1.Hash()}),
	}
	vals1 := map[int64]*types.ValidatorSet{
		1: vals,
		2: vals,
	}
	mockBadNode1 := mockNodeFromHeadersAndVals(headers1, vals1)
	mockBadNode1.On("LightBlock", mock.Anything, mock.Anything).Return(nil, provider.ErrLightBlockNotFound)

	// header is empty
	headers2 := map[int64]*types.SignedHeader{
		1: h1,
		2: h2,
	}
	vals2 := map[int64]*types.ValidatorSet{
		1: vals,
		2: vals,
	}
	mockBadNode2 := mockNodeFromHeadersAndVals(headers2, vals2)
	mockBadNode2.On("LightBlock", mock.Anything, mock.Anything).Return(nil, provider.ErrLightBlockNotFound)

	mockFullNode := mockNodeFromHeadersAndVals(headerSet, valSet)

	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	lb1, _ := mockBadNode1.LightBlock(ctx, 2)
	require.NotEqual(t, lb1.Hash(), l1.Hash())

	c, err := light.NewClient(
		ctx,
		chainID,
		trustOptions,
		mockFullNode,
		[]provider.Provider{mockBadNode1, mockBadNode2},
		dbs.New(dbm.NewMemDB()),
		light.Logger(logger),
	)
	// witness should have behaved properly -> no error
	require.NoError(t, err)
	assert.EqualValues(t, 2, len(c.Witnesses()))

	// witness behaves incorrectly -> removed from list, no error
	l, err := c.VerifyLightBlockAtHeight(ctx, 2, bTime.Add(2*time.Hour))
	assert.NoError(t, err)
	assert.EqualValues(t, 1, len(c.Witnesses()))
	// light block should still be verified
	assert.EqualValues(t, 2, l.Height)

	// remaining witnesses don't have light block -> error
	_, err = c.VerifyLightBlockAtHeight(ctx, 3, bTime.Add(2*time.Hour))
	if assert.Error(t, err) {
		assert.Equal(t, light.ErrFailedHeaderCrossReferencing, err)
	}
	// witness does not have a light block -> left in the list
	assert.EqualValues(t, 1, len(c.Witnesses()))
	mockBadNode1.AssertExpectations(t)
	mockBadNode2.AssertExpectations(t)
}

func TestClient_TrustedValidatorSet(t *testing.T) {
	logger := log.NewTestingLogger(t)

	differentVals, _ := factory.RandValidatorSet(10, 100)
	mockBadValSetNode := mockNodeFromHeadersAndVals(
		map[int64]*types.SignedHeader{
			1: h1,
			// 3/3 signed, but validator set at height 2 below is invalid -> witness
			// should be removed.
			2: keys.GenSignedHeaderLastBlockID(chainID, 2, bTime.Add(30*time.Minute), nil, vals, vals,
				hash("app_hash2"), hash("cons_hash"), hash("results_hash"),
				0, len(keys), types.BlockID{Hash: h1.Hash()}),
		},
		map[int64]*types.ValidatorSet{
			1: vals,
			2: differentVals,
		})
	mockFullNode := mockNodeFromHeadersAndVals(
		map[int64]*types.SignedHeader{
			1: h1,
			2: h2,
		},
		map[int64]*types.ValidatorSet{
			1: vals,
			2: vals,
		})

	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	c, err := light.NewClient(
		ctx,
		chainID,
		trustOptions,
		mockFullNode,
		[]provider.Provider{mockBadValSetNode, mockFullNode},
		dbs.New(dbm.NewMemDB()),
		light.Logger(logger),
	)
	require.NoError(t, err)
	assert.Equal(t, 2, len(c.Witnesses()))

	_, err = c.VerifyLightBlockAtHeight(ctx, 2, bTime.Add(2*time.Hour).Add(1*time.Second))
	assert.NoError(t, err)
	assert.Equal(t, 1, len(c.Witnesses()))
	mockBadValSetNode.AssertExpectations(t)
	mockFullNode.AssertExpectations(t)
}

func TestClientPrunesHeadersAndValidatorSets(t *testing.T) {
	mockFullNode := mockNodeFromHeadersAndVals(
		map[int64]*types.SignedHeader{
			1: h1,
			3: h3,
			0: h3,
		},
		map[int64]*types.ValidatorSet{
			1: vals,
			3: vals,
			0: vals,
		})

	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	logger := log.NewTestingLogger(t)

	c, err := light.NewClient(
		ctx,
		chainID,
		trustOptions,
		mockFullNode,
		[]provider.Provider{mockFullNode},
		dbs.New(dbm.NewMemDB()),
		light.Logger(logger),
		light.PruningSize(1),
	)
	require.NoError(t, err)
	_, err = c.TrustedLightBlock(1)
	require.NoError(t, err)

	h, err := c.Update(ctx, bTime.Add(2*time.Hour))
	require.NoError(t, err)
	require.Equal(t, int64(3), h.Height)

	_, err = c.TrustedLightBlock(1)
	assert.Error(t, err)
	mockFullNode.AssertExpectations(t)
}

func TestClientEnsureValidHeadersAndValSets(t *testing.T) {
	emptyValSet := &types.ValidatorSet{
		Validators: nil,
		Proposer:   nil,
	}

	testCases := []struct {
		headers map[int64]*types.SignedHeader
		vals    map[int64]*types.ValidatorSet

		errorToThrow error
		errorHeight  int64

		err bool
	}{
		{
			headers: map[int64]*types.SignedHeader{
				1: h1,
				3: h3,
			},
			vals: map[int64]*types.ValidatorSet{
				1: vals,
				3: vals,
			},
			err: false,
		},
		{
			headers: map[int64]*types.SignedHeader{
				1: h1,
			},
			vals: map[int64]*types.ValidatorSet{
				1: vals,
			},
			errorToThrow: provider.ErrBadLightBlock{Reason: errors.New("nil header or vals")},
			errorHeight:  3,
			err:          true,
		},
		{
			headers: map[int64]*types.SignedHeader{
				1: h1,
			},
			errorToThrow: provider.ErrBadLightBlock{Reason: errors.New("nil header or vals")},
			errorHeight:  3,
			vals:         valSet,
			err:          true,
		},
		{
			headers: map[int64]*types.SignedHeader{
				1: h1,
				3: h3,
			},
			vals: map[int64]*types.ValidatorSet{
				1: vals,
				3: emptyValSet,
			},
			err: true,
		},
	}

	for i, tc := range testCases {
		testCase := tc
		t.Run(fmt.Sprintf("case: %d", i), func(t *testing.T) {
			ctx, cancel := context.WithCancel(context.Background())
			defer cancel()

			mockBadNode := mockNodeFromHeadersAndVals(testCase.headers, testCase.vals)
			if testCase.errorToThrow != nil {
				mockBadNode.On("LightBlock", mock.Anything, testCase.errorHeight).Return(nil, testCase.errorToThrow)
			}

			c, err := light.NewClient(
				ctx,
				chainID,
				trustOptions,
				mockBadNode,
				[]provider.Provider{mockBadNode, mockBadNode},
				dbs.New(dbm.NewMemDB()),
			)
			require.NoError(t, err)

			_, err = c.VerifyLightBlockAtHeight(ctx, 3, bTime.Add(2*time.Hour))
			if testCase.err {
				assert.Error(t, err)
			} else {
				assert.NoError(t, err)
			}
			mockBadNode.AssertExpectations(t)
		})
	}
}