package scheduler

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

	"gitea.maximumdirect.net/ejr/feedkit/config"
	"gitea.maximumdirect.net/ejr/feedkit/event"
	"gitea.maximumdirect.net/ejr/feedkit/sources"
)

type testPollSource struct {
	name string
}

func (s testPollSource) Name() string { return s.name }

func (s testPollSource) Poll(context.Context) ([]event.Event, error) { return nil, nil }

type scriptedStreamSource struct {
	name  string
	mu    sync.Mutex
	calls int
	runs  []func(context.Context, chan<- event.Event) error
}

func (s *scriptedStreamSource) Name() string { return s.name }

func (s *scriptedStreamSource) Run(ctx context.Context, out chan<- event.Event) error {
	s.mu.Lock()
	call := s.calls
	s.calls++
	var run func(context.Context, chan<- event.Event) error
	if call < len(s.runs) {
		run = s.runs[call]
	}
	s.mu.Unlock()

	if run != nil {
		return run(ctx, out)
	}

	<-ctx.Done()
	return ctx.Err()
}

func (s *scriptedStreamSource) CallCount() int {
	s.mu.Lock()
	defer s.mu.Unlock()
	return s.calls
}

type capturingLogger struct {
	mu    sync.Mutex
	lines []string
}

func (l *capturingLogger) Logf(format string, args ...any) {
	l.mu.Lock()
	defer l.mu.Unlock()
	l.lines = append(l.lines, fmt.Sprintf(format, args...))
}

func (l *capturingLogger) Contains(substr string) bool {
	l.mu.Lock()
	defer l.mu.Unlock()
	for _, line := range l.lines {
		if strings.Contains(line, substr) {
			return true
		}
	}
	return false
}

func TestSchedulerRunRestartsPlainStreamErrors(t *testing.T) {
	src := &scriptedStreamSource{
		name: "stream-a",
		runs: []func(context.Context, chan<- event.Event) error{
			func(context.Context, chan<- event.Event) error { return errors.New("temporary failure") },
			func(context.Context, chan<- event.Event) error { return errors.New("temporary failure") },
		},
	}

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

	s := &Scheduler{
		Jobs: []Job{{
			Source: src,
			StreamBackoff: StreamBackoff{
				Initial: time.Millisecond,
				Max:     time.Millisecond,
			},
		}},
		Out: make(chan event.Event, 1),
	}

	errCh := make(chan error, 1)
	go func() { errCh <- s.Run(ctx) }()

	waitFor(t, func() bool { return src.CallCount() >= 3 })
	cancel()

	err := <-errCh
	if !errors.Is(err, context.Canceled) {
		t.Fatalf("Scheduler.Run() error = %v, want context canceled", err)
	}
	if src.CallCount() < 3 {
		t.Fatalf("stream call count = %d, want at least 3", src.CallCount())
	}
}

func TestSchedulerRunFatalStreamErrorReturns(t *testing.T) {
	base := errors.New("fatal failure")
	src := &scriptedStreamSource{
		name: "stream-fatal",
		runs: []func(context.Context, chan<- event.Event) error{
			func(context.Context, chan<- event.Event) error { return sources.StreamFatal(base) },
		},
	}

	s := &Scheduler{
		Jobs: []Job{{Source: src}},
		Out:  make(chan event.Event, 1),
	}

	err := s.Run(context.Background())
	if err == nil {
		t.Fatalf("Scheduler.Run() error = nil, want fatal error")
	}
	if !sources.IsStreamFatal(err) {
		t.Fatalf("Scheduler.Run() error = %v, want fatal classification", err)
	}
	if !errors.Is(err, base) {
		t.Fatalf("Scheduler.Run() error does not wrap base fatal error: %v", err)
	}
}

func TestSchedulerRunStopPolicyStopsOnlyThatSource(t *testing.T) {
	src := &scriptedStreamSource{
		name: "stream-stop",
		runs: []func(context.Context, chan<- event.Event) error{
			func(context.Context, chan<- event.Event) error { return errors.New("stop now") },
		},
	}

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

	s := &Scheduler{
		Jobs: []Job{{
			Source:           src,
			StreamExitPolicy: StreamExitPolicyStop,
		}},
		Out: make(chan event.Event, 1),
	}

	errCh := make(chan error, 1)
	go func() { errCh <- s.Run(ctx) }()

	waitFor(t, func() bool { return src.CallCount() >= 1 })
	time.Sleep(20 * time.Millisecond)

	select {
	case err := <-errCh:
		t.Fatalf("Scheduler.Run() returned early: %v", err)
	default:
	}

	if src.CallCount() != 1 {
		t.Fatalf("stream call count = %d, want 1", src.CallCount())
	}

	cancel()
	err := <-errCh
	if !errors.Is(err, context.Canceled) {
		t.Fatalf("Scheduler.Run() error = %v, want context canceled", err)
	}
}

func TestSchedulerRunFatalPolicyTreatsPlainErrorAsFatal(t *testing.T) {
	base := errors.New("plain failure")
	src := &scriptedStreamSource{
		name: "stream-fatal-policy",
		runs: []func(context.Context, chan<- event.Event) error{
			func(context.Context, chan<- event.Event) error { return base },
		},
	}

	s := &Scheduler{
		Jobs: []Job{{
			Source:           src,
			StreamExitPolicy: StreamExitPolicyFatal,
		}},
		Out: make(chan event.Event, 1),
	}

	err := s.Run(context.Background())
	if err == nil {
		t.Fatalf("Scheduler.Run() error = nil, want fatal-policy error")
	}
	if !errors.Is(err, base) {
		t.Fatalf("Scheduler.Run() error does not wrap base error: %v", err)
	}
}

func TestSchedulerRunNilExitRestartsAsUnexpected(t *testing.T) {
	logger := &capturingLogger{}
	src := &scriptedStreamSource{
		name: "stream-nil-exit",
		runs: []func(context.Context, chan<- event.Event) error{
			func(context.Context, chan<- event.Event) error { return nil },
		},
	}

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

	s := &Scheduler{
		Jobs: []Job{{
			Source: src,
			StreamBackoff: StreamBackoff{
				Initial: time.Millisecond,
				Max:     time.Millisecond,
			},
		}},
		Out:  make(chan event.Event, 1),
		Logf: logger.Logf,
	}

	errCh := make(chan error, 1)
	go func() { errCh <- s.Run(ctx) }()

	waitFor(t, func() bool { return src.CallCount() >= 2 })
	cancel()

	err := <-errCh
	if !errors.Is(err, context.Canceled) {
		t.Fatalf("Scheduler.Run() error = %v, want context canceled", err)
	}
	if !logger.Contains("exited unexpectedly without error") {
		t.Fatalf("expected log to mention unexpected nil stream exit")
	}
}

func TestSchedulerRunContextCancelDuringBackoff(t *testing.T) {
	src := &scriptedStreamSource{
		name: "stream-backoff-cancel",
		runs: []func(context.Context, chan<- event.Event) error{
			func(context.Context, chan<- event.Event) error { return errors.New("retry me") },
		},
	}

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

	s := &Scheduler{
		Jobs: []Job{{
			Source: src,
			StreamBackoff: StreamBackoff{
				Initial: time.Second,
				Max:     time.Second,
			},
		}},
		Out: make(chan event.Event, 1),
	}

	errCh := make(chan error, 1)
	go func() { errCh <- s.Run(ctx) }()

	waitFor(t, func() bool { return src.CallCount() >= 1 })
	cancel()

	err := <-errCh
	if !errors.Is(err, context.Canceled) {
		t.Fatalf("Scheduler.Run() error = %v, want context canceled", err)
	}
	time.Sleep(20 * time.Millisecond)
	if src.CallCount() != 1 {
		t.Fatalf("stream call count = %d, want 1", src.CallCount())
	}
}

func TestNextStreamBackoffCapsAtMax(t *testing.T) {
	if got := nextStreamBackoff(500*time.Millisecond, 2*time.Second); got != time.Second {
		t.Fatalf("nextStreamBackoff() = %s, want 1s", got)
	}
	if got := nextStreamBackoff(time.Second, 2*time.Second); got != 2*time.Second {
		t.Fatalf("nextStreamBackoff() = %s, want 2s", got)
	}
	if got := nextStreamBackoff(2*time.Second, 2*time.Second); got != 2*time.Second {
		t.Fatalf("nextStreamBackoff() = %s, want 2s", got)
	}
}

func TestStreamRunWasStableAfterFiveMinutes(t *testing.T) {
	start := time.Date(2026, 3, 29, 12, 0, 0, 0, time.UTC)
	if streamRunWasStable(start, start.Add(4*time.Minute+59*time.Second)) {
		t.Fatalf("streamRunWasStable() = true, want false")
	}
	if !streamRunWasStable(start, start.Add(5*time.Minute)) {
		t.Fatalf("streamRunWasStable() = false, want true")
	}
}

func TestJobFromSourceConfigPollSource(t *testing.T) {
	job, err := JobFromSourceConfig(testPollSource{name: "poll-a"}, config.SourceConfig{
		Name:   "poll-a",
		Driver: "poll_driver",
		Every:  config.Duration{Duration: time.Minute},
	})
	if err != nil {
		t.Fatalf("JobFromSourceConfig() error = %v", err)
	}
	if job.Every != time.Minute {
		t.Fatalf("Job.Every = %s, want 1m", job.Every)
	}
}

func TestJobFromSourceConfigPollSourceRejectsStreamParams(t *testing.T) {
	_, err := JobFromSourceConfig(testPollSource{name: "poll-a"}, config.SourceConfig{
		Name:   "poll-a",
		Driver: "poll_driver",
		Every:  config.Duration{Duration: time.Minute},
		Params: map[string]any{
			"stream_exit_policy": "restart",
		},
	})
	if err == nil {
		t.Fatalf("JobFromSourceConfig() error = nil, want rejection")
	}
	if !strings.Contains(err.Error(), "only valid for stream sources") {
		t.Fatalf("JobFromSourceConfig() error = %q", err)
	}
}

func TestJobFromSourceConfigStreamSourceParsesDefaultsAndOverrides(t *testing.T) {
	src := &scriptedStreamSource{name: "stream-a"}

	job, err := JobFromSourceConfig(src, config.SourceConfig{
		Name:   "stream-a",
		Driver: "stream_driver",
		Mode:   config.SourceModeStream,
		Params: map[string]any{
			"stream_exit_policy":     "stop",
			"stream_backoff_initial": "2s",
			"stream_backoff_max":     "10s",
			"stream_backoff_jitter":  "500ms",
		},
	})
	if err != nil {
		t.Fatalf("JobFromSourceConfig() error = %v", err)
	}
	if job.StreamExitPolicy != StreamExitPolicyStop {
		t.Fatalf("Job.StreamExitPolicy = %q, want %q", job.StreamExitPolicy, StreamExitPolicyStop)
	}
	if job.StreamBackoff.Initial != 2*time.Second {
		t.Fatalf("Job.StreamBackoff.Initial = %s, want 2s", job.StreamBackoff.Initial)
	}
	if job.StreamBackoff.Max != 10*time.Second {
		t.Fatalf("Job.StreamBackoff.Max = %s, want 10s", job.StreamBackoff.Max)
	}
	if job.StreamBackoff.Jitter != 500*time.Millisecond {
		t.Fatalf("Job.StreamBackoff.Jitter = %s, want 500ms", job.StreamBackoff.Jitter)
	}

	defaultJob, err := JobFromSourceConfig(src, config.SourceConfig{
		Name:   "stream-default",
		Driver: "stream_driver",
		Mode:   config.SourceModeStream,
	})
	if err != nil {
		t.Fatalf("JobFromSourceConfig() default error = %v", err)
	}
	if defaultJob.StreamExitPolicy != StreamExitPolicyRestart {
		t.Fatalf("default Job.StreamExitPolicy = %q, want restart", defaultJob.StreamExitPolicy)
	}
	if defaultJob.StreamBackoff.Initial != defaultStreamBackoffInitial {
		t.Fatalf("default Job.StreamBackoff.Initial = %s, want %s", defaultJob.StreamBackoff.Initial, defaultStreamBackoffInitial)
	}
	if defaultJob.StreamBackoff.Max != defaultStreamBackoffMax {
		t.Fatalf("default Job.StreamBackoff.Max = %s, want %s", defaultJob.StreamBackoff.Max, defaultStreamBackoffMax)
	}
	if defaultJob.StreamBackoff.Jitter != defaultStreamBackoffJitter {
		t.Fatalf("default Job.StreamBackoff.Jitter = %s, want %s", defaultJob.StreamBackoff.Jitter, defaultStreamBackoffJitter)
	}
}

func TestJobFromSourceConfigStreamSourceRejectsInvalidSettings(t *testing.T) {
	src := &scriptedStreamSource{name: "stream-b"}

	_, err := JobFromSourceConfig(src, config.SourceConfig{
		Name:   "stream-b",
		Driver: "stream_driver",
		Mode:   config.SourceModeStream,
		Params: map[string]any{
			"stream_exit_policy": "sometimes",
		},
	})
	if err == nil {
		t.Fatalf("JobFromSourceConfig() error = nil, want invalid policy error")
	}
	if !strings.Contains(err.Error(), "stream_exit_policy") {
		t.Fatalf("JobFromSourceConfig() error = %q", err)
	}

	_, err = JobFromSourceConfig(src, config.SourceConfig{
		Name:   "stream-b",
		Driver: "stream_driver",
		Mode:   config.SourceModeStream,
		Params: map[string]any{
			"stream_backoff_initial": "0s",
		},
	})
	if err == nil {
		t.Fatalf("JobFromSourceConfig() error = nil, want invalid initial backoff error")
	}
	if !strings.Contains(err.Error(), "stream_backoff_initial") {
		t.Fatalf("JobFromSourceConfig() error = %q", err)
	}

	_, err = JobFromSourceConfig(src, config.SourceConfig{
		Name:   "stream-b",
		Driver: "stream_driver",
		Mode:   config.SourceModeStream,
		Params: map[string]any{
			"stream_backoff_initial": "2s",
			"stream_backoff_max":     "1s",
		},
	})
	if err == nil {
		t.Fatalf("JobFromSourceConfig() error = nil, want invalid max backoff error")
	}
	if !strings.Contains(err.Error(), "stream_backoff_max") {
		t.Fatalf("JobFromSourceConfig() error = %q", err)
	}
}

func TestJobFromSourceConfigStreamSourceRejectsEvery(t *testing.T) {
	src := &scriptedStreamSource{name: "stream-c"}

	_, err := JobFromSourceConfig(src, config.SourceConfig{
		Name:   "stream-c",
		Driver: "stream_driver",
		Mode:   config.SourceModeStream,
		Every:  config.Duration{Duration: time.Minute},
	})
	if err == nil {
		t.Fatalf("JobFromSourceConfig() error = nil, want every rejection")
	}
	if !strings.Contains(err.Error(), "sources[].every must be omitted") {
		t.Fatalf("JobFromSourceConfig() error = %q", err)
	}
}

func waitFor(t *testing.T, cond func() bool) {
	t.Helper()

	deadline := time.Now().Add(2 * time.Second)
	for time.Now().Before(deadline) {
		if cond() {
			return
		}
		time.Sleep(10 * time.Millisecond)
	}
	t.Fatalf("condition not satisfied before timeout")
}