package driver

import (
	"context"
	"testing"

	"github.com/ethereum-optimism/optimism/op-node/rollup"
	"github.com/ethereum-optimism/optimism/op-service/eth"
	"github.com/ethereum-optimism/optimism/op-service/testlog"
	"github.com/ethereum-optimism/optimism/op-service/testutils"
	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/log"
	"github.com/stretchr/testify/require"
)

// TestOriginSelectorAdvances ensures that the origin selector
// advances the origin
//
// There are 2 L1 blocks at time 20 & 25. The L2 Head is at time 24.
// The next L2 time is 26 which is after the next L1 block time. There
// is no conf depth to stop the origin selection so block `b` should
// be the next L1 origin
func TestOriginSelectorAdvances(t *testing.T) {
	log := testlog.Logger(t, log.LvlCrit)
	cfg := &rollup.Config{
		MaxSequencerDrift: 500,
		BlockTime:         2,
	}
	l1 := &testutils.MockL1Source{}
	defer l1.AssertExpectations(t)
	a := eth.L1BlockRef{
		Hash:   common.Hash{'a'},
		Number: 10,
		Time:   20,
	}
	b := eth.L1BlockRef{
		Hash:       common.Hash{'b'},
		Number:     11,
		Time:       25,
		ParentHash: a.Hash,
	}
	l2Head := eth.L2BlockRef{
		L1Origin: a.ID(),
		Time:     24,
	}

	l1.ExpectL1BlockRefByHash(a.Hash, a, nil)
	l1.ExpectL1BlockRefByNumber(b.Number, b, nil)

	s := NewL1OriginSelector(log, cfg, l1)
	next, err := s.FindL1Origin(context.Background(), l2Head)
	require.Nil(t, err)
	require.Equal(t, b, next)
}

// TestOriginSelectorRespectsOriginTiming ensures that the origin selector
// does not pick an origin that is ahead of the next L2 block time
//
// There are 2 L1 blocks at time 20 & 25. The L2 Head is at time 22.
// The next L2 time is 24 which is before the next L1 block time. There
// is no conf depth to stop the LOS from potentially selecting block `b`
// but it should select block `a` because the L2 block time must be ahead
// of the the timestamp of it's L1 origin.
func TestOriginSelectorRespectsOriginTiming(t *testing.T) {
	log := testlog.Logger(t, log.LvlCrit)
	cfg := &rollup.Config{
		MaxSequencerDrift: 500,
		BlockTime:         2,
	}
	l1 := &testutils.MockL1Source{}
	defer l1.AssertExpectations(t)
	a := eth.L1BlockRef{
		Hash:   common.Hash{'a'},
		Number: 10,
		Time:   20,
	}
	b := eth.L1BlockRef{
		Hash:       common.Hash{'b'},
		Number:     11,
		Time:       25,
		ParentHash: a.Hash,
	}
	l2Head := eth.L2BlockRef{
		L1Origin: a.ID(),
		Time:     22,
	}

	l1.ExpectL1BlockRefByHash(a.Hash, a, nil)
	l1.ExpectL1BlockRefByNumber(b.Number, b, nil)

	s := NewL1OriginSelector(log, cfg, l1)
	next, err := s.FindL1Origin(context.Background(), l2Head)
	require.Nil(t, err)
	require.Equal(t, a, next)
}

// TestOriginSelectorRespectsConfDepth ensures that the origin selector
// will respect the confirmation depth requirement
//
// There are 2 L1 blocks at time 20 & 25. The L2 Head is at time 27.
// The next L2 time is 29 which enough to normally select block `b`
// as the origin, however block `b` is the L1 Head & the sequencer
// needs to wait until that block is confirmed enough before advancing.
func TestOriginSelectorRespectsConfDepth(t *testing.T) {
	log := testlog.Logger(t, log.LvlCrit)
	cfg := &rollup.Config{
		MaxSequencerDrift: 500,
		BlockTime:         2,
	}
	l1 := &testutils.MockL1Source{}
	defer l1.AssertExpectations(t)
	a := eth.L1BlockRef{
		Hash:   common.Hash{'a'},
		Number: 10,
		Time:   20,
	}
	b := eth.L1BlockRef{
		Hash:       common.Hash{'b'},
		Number:     11,
		Time:       25,
		ParentHash: a.Hash,
	}
	l2Head := eth.L2BlockRef{
		L1Origin: a.ID(),
		Time:     27,
	}

	l1.ExpectL1BlockRefByHash(a.Hash, a, nil)
	confDepthL1 := NewConfDepth(10, func() eth.L1BlockRef { return b }, l1)
	s := NewL1OriginSelector(log, cfg, confDepthL1)

	next, err := s.FindL1Origin(context.Background(), l2Head)
	require.Nil(t, err)
	require.Equal(t, a, next)
}

// TestOriginSelectorStrictConfDepth ensures that the origin selector will maintain the sequencer conf depth,
// even while the time delta between the current L1 origin and the next
// L2 block is greater than the sequencer drift.
// It's more important to maintain safety with an empty block than to maintain liveness with poor conf depth.
//
// There are 2 L1 blocks at time 20 & 25. The L2 Head is at time 27.
// The next L2 time is 29. The sequencer drift is 8 so the L2 head is
// valid with origin `a`, but the next L2 block is not valid with origin `b.`
// This is because 29 (next L2 time) > 20 (origin) + 8 (seq drift) => invalid block.
// We maintain confirmation distance, even though we would shift to the next origin if we could.
func TestOriginSelectorStrictConfDepth(t *testing.T) {
	log := testlog.Logger(t, log.LvlCrit)
	cfg := &rollup.Config{
		MaxSequencerDrift: 8,
		BlockTime:         2,
	}
	l1 := &testutils.MockL1Source{}
	defer l1.AssertExpectations(t)
	a := eth.L1BlockRef{
		Hash:   common.Hash{'a'},
		Number: 10,
		Time:   20,
	}
	b := eth.L1BlockRef{
		Hash:       common.Hash{'b'},
		Number:     11,
		Time:       25,
		ParentHash: a.Hash,
	}
	l2Head := eth.L2BlockRef{
		L1Origin: a.ID(),
		Time:     27,
	}

	l1.ExpectL1BlockRefByHash(a.Hash, a, nil)
	confDepthL1 := NewConfDepth(10, func() eth.L1BlockRef { return b }, l1)
	s := NewL1OriginSelector(log, cfg, confDepthL1)

	_, err := s.FindL1Origin(context.Background(), l2Head)
	require.ErrorContains(t, err, "sequencer time drift")
}

// TestOriginSelectorSeqDriftRespectsNextOriginTime
//
// There are 2 L1 blocks at time 20 & 100. The L2 Head is at time 27.
// The next L2 time is 29. Even though the next L2 time is past the seq
// drift, the origin should remain on block `a` because the next origin's
// time is greater than the next L2 time.
func TestOriginSelectorSeqDriftRespectsNextOriginTime(t *testing.T) {
	log := testlog.Logger(t, log.LvlCrit)
	cfg := &rollup.Config{
		MaxSequencerDrift: 8,
		BlockTime:         2,
	}
	l1 := &testutils.MockL1Source{}
	defer l1.AssertExpectations(t)
	a := eth.L1BlockRef{
		Hash:   common.Hash{'a'},
		Number: 10,
		Time:   20,
	}
	b := eth.L1BlockRef{
		Hash:       common.Hash{'b'},
		Number:     11,
		Time:       100,
		ParentHash: a.Hash,
	}
	l2Head := eth.L2BlockRef{
		L1Origin: a.ID(),
		Time:     27,
	}

	l1.ExpectL1BlockRefByHash(a.Hash, a, nil)
	l1.ExpectL1BlockRefByNumber(b.Number, b, nil)

	s := NewL1OriginSelector(log, cfg, l1)
	next, err := s.FindL1Origin(context.Background(), l2Head)
	require.Nil(t, err)
	require.Equal(t, a, next)
}

// TestOriginSelectorHandlesLateL1Blocks tests the forced repeat of the previous origin,
// but with a conf depth that first prevents it from learning about the need to repeat.
//
// There are 2 L1 blocks at time 20 & 100. The L2 Head is at time 27.
// The next L2 time is 29. Even though the next L2 time is past the seq
// drift, the origin should remain on block `a` because the next origin's
// time is greater than the next L2 time.
// Due to a conf depth of 2, block `b` is not immediately visible,
// and the origin selection should fail until it is visible, by waiting for block `c`.
func TestOriginSelectorHandlesLateL1Blocks(t *testing.T) {
	log := testlog.Logger(t, log.LvlCrit)
	cfg := &rollup.Config{
		MaxSequencerDrift: 8,
		BlockTime:         2,
	}
	l1 := &testutils.MockL1Source{}
	defer l1.AssertExpectations(t)
	a := eth.L1BlockRef{
		Hash:   common.Hash{'a'},
		Number: 10,
		Time:   20,
	}
	b := eth.L1BlockRef{
		Hash:       common.Hash{'b'},
		Number:     11,
		Time:       100,
		ParentHash: a.Hash,
	}
	c := eth.L1BlockRef{
		Hash:       common.Hash{'c'},
		Number:     12,
		Time:       150,
		ParentHash: b.Hash,
	}
	d := eth.L1BlockRef{
		Hash:       common.Hash{'d'},
		Number:     13,
		Time:       200,
		ParentHash: c.Hash,
	}
	l2Head := eth.L2BlockRef{
		L1Origin: a.ID(),
		Time:     27,
	}

	// l2 head does not change, so we start at the same origin again and again until we meet the conf depth
	l1.ExpectL1BlockRefByHash(a.Hash, a, nil)
	l1.ExpectL1BlockRefByHash(a.Hash, a, nil)
	l1.ExpectL1BlockRefByHash(a.Hash, a, nil)
	l1.ExpectL1BlockRefByNumber(b.Number, b, nil)

	l1Head := b
	confDepthL1 := NewConfDepth(2, func() eth.L1BlockRef { return l1Head }, l1)
	s := NewL1OriginSelector(log, cfg, confDepthL1)

	_, err := s.FindL1Origin(context.Background(), l2Head)
	require.ErrorContains(t, err, "sequencer time drift")

	l1Head = c
	_, err = s.FindL1Origin(context.Background(), l2Head)
	require.ErrorContains(t, err, "sequencer time drift")

	l1Head = d
	next, err := s.FindL1Origin(context.Background(), l2Head)
	require.Nil(t, err)
	require.Equal(t, a, next, "must stay on a because the L1 time may not be higher than the L2 time")
}
