package logging

import (
	"bytes"
	"errors"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"sync/atomic"
	"testing"
	"time"

	log "github.com/sirupsen/logrus"
)

func TestWeeklyLogRotationShiftsAndRetainsExactGenerations(t *testing.T) {
	directory := t.TempDir()
	path := filepath.Join(directory, "hardlink.log")
	writeLogTestFile(t, path, "active")
	for generation := 1; generation <= 14; generation++ {
		writeLogTestFile(t, weeklyLogTestGeneration(path, generation), fmt.Sprintf("generation-%d", generation))
	}
	writeLogTestFile(t, weeklyLogTestGeneration(path, 19), "generation-19")
	for name, contents := range map[string]string{
		"hardlink.backup.14.log": "related-looking backup",
		"another.14.log":         "unrelated log",
		"hardlink.14.log.bak":    "different extension",
	} {
		writeLogTestFile(t, filepath.Join(directory, name), contents)
	}

	sunday := time.Date(2026, time.August, 9, 12, 0, 0, 0, time.UTC)
	setLogTestModTime(t, path, sunday)
	writer := newLogTestWriter(t, path, sunday, weeklyLogRuntime{})
	writer.rotateIfNeeded(time.Date(2026, time.August, 10, 0, 0, 0, 0, time.UTC))
	if err := writer.Close(); err != nil {
		t.Fatal(err)
	}

	requireLogTestContents(t, path, "")
	requireLogTestContents(t, weeklyLogTestGeneration(path, 1), "active")
	requireLogTestContents(t, weeklyLogTestGeneration(path, 2), "generation-1")
	requireLogTestContents(t, weeklyLogTestGeneration(path, 13), "generation-12")
	for _, generation := range []int{14, 19} {
		if _, err := os.Stat(weeklyLogTestGeneration(path, generation)); !errors.Is(err, os.ErrNotExist) {
			t.Errorf("generation %d exists after rotation, want removed: %v", generation, err)
		}
	}
	for name, contents := range map[string]string{
		"hardlink.backup.14.log": "related-looking backup",
		"another.14.log":         "unrelated log",
		"hardlink.14.log.bak":    "different extension",
	} {
		requireLogTestContents(t, filepath.Join(directory, name), contents)
	}
}

func TestWeeklyLogRotationOccursOncePerWeek(t *testing.T) {
	directory := t.TempDir()
	path := filepath.Join(directory, "hardlink.log")
	writeLogTestFile(t, path, "week-zero\n")
	sunday := time.Date(2026, time.January, 4, 18, 0, 0, 0, time.UTC)
	setLogTestModTime(t, path, sunday)
	writer := newLogTestWriter(t, path, sunday, weeklyLogRuntime{})

	writer.rotateIfNeeded(time.Date(2026, time.January, 4, 23, 59, 59, 0, time.UTC))
	if _, err := os.Stat(weeklyLogTestGeneration(path, 1)); !errors.Is(err, os.ErrNotExist) {
		t.Fatalf("rotation before Monday: %v, want no generation", err)
	}
	writer.rotateIfNeeded(time.Date(2026, time.January, 5, 0, 0, 0, 0, time.UTC))
	if _, err := writer.Write([]byte("week-one\n")); err != nil {
		t.Fatal(err)
	}
	writer.rotateIfNeeded(time.Date(2026, time.January, 6, 12, 0, 0, 0, time.UTC))
	if err := writer.Close(); err != nil {
		t.Fatal(err)
	}

	requireLogTestContents(t, weeklyLogTestGeneration(path, 1), "week-zero\n")
	requireLogTestContents(t, path, "week-one\n")
	if _, err := os.Stat(weeklyLogTestGeneration(path, 2)); !errors.Is(err, os.ErrNotExist) {
		t.Errorf("same-week rotation created generation 2: %v", err)
	}
}

func TestWeeklyLogStartupRotatesOnceAfterSeveralMissedWeeks(t *testing.T) {
	directory := t.TempDir()
	path := filepath.Join(directory, "hardlink.log")
	writeLogTestFile(t, path, "old active")
	writeLogTestFile(t, weeklyLogTestGeneration(path, 1), "older history")
	setLogTestModTime(t, path, time.Date(2026, time.January, 5, 12, 0, 0, 0, time.UTC))

	now := time.Date(2026, time.February, 23, 9, 0, 0, 0, time.UTC)
	writer := newLogTestWriter(t, path, now, weeklyLogRuntime{})
	if err := writer.Close(); err != nil {
		t.Fatal(err)
	}

	requireLogTestContents(t, weeklyLogTestGeneration(path, 1), "old active")
	requireLogTestContents(t, weeklyLogTestGeneration(path, 2), "older history")
	if _, err := os.Stat(weeklyLogTestGeneration(path, 3)); !errors.Is(err, os.ErrNotExist) {
		t.Errorf("missed weeks created generation 3: %v", err)
	}
}

func TestWeeklyLogSchedulerUsesLocalMondayBoundary(t *testing.T) {
	location, err := time.LoadLocation("Europe/London")
	if err != nil {
		t.Fatal(err)
	}
	directory := t.TempDir()
	path := filepath.Join(directory, "hardlink.log")
	writeLogTestFile(t, path, "sunday")
	sunday := time.Date(2026, time.March, 29, 0, 0, 0, 0, location)
	setLogTestModTime(t, path, sunday)

	clock := &atomic.Pointer[time.Time]{}
	clock.Store(&sunday)
	created := make(chan *logTestTimer, 2)
	rotated := make(chan struct{})
	runtime := weeklyLogRuntime{
		now: func() time.Time { return *clock.Load() },
		newTimer: func(duration time.Duration) logRotationTimer {
			timer := &logTestTimer{duration: duration, ch: make(chan time.Time, 1)}
			created <- timer
			return timer
		},
		rename: func(oldPath, newPath string) error {
			err := os.Rename(oldPath, newPath)
			if oldPath == path && err == nil {
				close(rotated)
			}
			return err
		},
	}
	writer, err := newWeeklyLogWriter(path, location, runtime)
	if err != nil {
		t.Fatal(err)
	}
	timer := <-created
	if timer.duration != 23*time.Hour {
		t.Fatalf("timer duration = %v, want 23h across DST boundary", timer.duration)
	}
	monday := time.Date(2026, time.March, 30, 0, 0, 0, 0, location)
	clock.Store(&monday)
	timer.ch <- monday
	<-rotated
	if err := writer.Close(); err != nil {
		t.Fatal(err)
	}
	requireLogTestContents(t, weeklyLogTestGeneration(path, 1), "sunday")
}

func TestWeeklyLogConcurrentWritesRemainCompleteAcrossRotation(t *testing.T) {
	directory := t.TempDir()
	path := filepath.Join(directory, "hardlink.log")
	sunday := time.Date(2026, time.August, 9, 12, 0, 0, 0, time.UTC)
	writer := newLogTestWriter(t, path, sunday, weeklyLogRuntime{})

	const goroutines = 8
	const recordsPerGoroutine = 100
	writeErrors := make(chan error, goroutines)
	var writers sync.WaitGroup
	writers.Add(goroutines)
	for worker := 0; worker < goroutines; worker++ {
		go func() {
			defer writers.Done()
			for record := 0; record < recordsPerGoroutine; record++ {
				if _, err := writer.Write([]byte(fmt.Sprintf("%d:%d\n", worker, record))); err != nil {
					writeErrors <- err
					return
				}
			}
		}()
	}
	writer.rotateIfNeeded(time.Date(2026, time.August, 10, 0, 0, 0, 0, time.UTC))
	writers.Wait()
	close(writeErrors)
	for err := range writeErrors {
		t.Errorf("weeklyLogWriter.Write() error = %v, want nil", err)
	}
	if err := writer.Close(); err != nil {
		t.Fatal(err)
	}

	contents := readLogTestFile(t, weeklyLogTestGeneration(path, 1)) + readLogTestFile(t, path)
	lines := strings.Split(strings.TrimSpace(contents), "\n")
	if len(lines) != goroutines*recordsPerGoroutine {
		t.Fatalf("record count = %d, want %d", len(lines), goroutines*recordsPerGoroutine)
	}
	seen := make(map[string]bool, len(lines))
	for _, line := range lines {
		if _, _, ok := strings.Cut(line, ":"); !ok {
			t.Fatalf("record %q has no separator", line)
		}
		seen[line] = true
	}
	if len(seen) != goroutines*recordsPerGoroutine {
		t.Errorf("unique record count = %d, want %d", len(seen), goroutines*recordsPerGoroutine)
	}
}

func TestWeeklyLogCloseWaitsForRotationAndIsIdempotent(t *testing.T) {
	directory := t.TempDir()
	path := filepath.Join(directory, "hardlink.log")
	writeLogTestFile(t, path, "active")
	sunday := time.Date(2026, time.August, 9, 12, 0, 0, 0, time.UTC)
	setLogTestModTime(t, path, sunday)
	started := make(chan struct{})
	release := make(chan struct{})
	runtime := weeklyLogRuntime{rename: func(oldPath, newPath string) error {
		if oldPath == path {
			close(started)
			<-release
		}
		return os.Rename(oldPath, newPath)
	}}
	writer := newLogTestWriter(t, path, sunday, runtime)
	rotationDone := make(chan struct{})
	go func() {
		writer.rotateIfNeeded(time.Date(2026, time.August, 10, 0, 0, 0, 0, time.UTC))
		close(rotationDone)
	}()
	<-started

	closeDone := make(chan error, 1)
	go func() { closeDone <- writer.Close() }()
	select {
	case err := <-closeDone:
		t.Fatalf("weeklyLogWriter.Close() during rotation returned %v, want blocked", err)
	case <-time.After(20 * time.Millisecond):
	}
	close(release)
	<-rotationDone
	if err := <-closeDone; err != nil {
		t.Fatal(err)
	}
	if err := writer.Close(); err != nil {
		t.Errorf("second weeklyLogWriter.Close() error = %v, want nil", err)
	}
	if _, err := writer.Write([]byte("after close")); !errors.Is(err, os.ErrClosed) {
		t.Errorf("weeklyLogWriter.Write() after close error = %v, want os.ErrClosed", err)
	}
}

func TestWeeklyLogRotationFailureIsNonRecursiveAndPreservesWrites(t *testing.T) {
	directory := t.TempDir()
	path := filepath.Join(directory, "hardlink.log")
	writeLogTestFile(t, path, "before\n")
	sunday := time.Date(2026, time.August, 9, 12, 0, 0, 0, time.UTC)
	setLogTestModTime(t, path, sunday)
	var diagnostics bytes.Buffer
	runtime := weeklyLogRuntime{
		rename: func(oldPath, newPath string) error {
			if oldPath == path {
				return errors.New("injected rename failure")
			}
			return os.Rename(oldPath, newPath)
		},
		diagnostic: &diagnostics,
	}
	writer := newLogTestWriter(t, path, sunday, runtime)
	writer.rotateIfNeeded(time.Date(2026, time.August, 10, 0, 0, 0, 0, time.UTC))
	if _, err := writer.Write([]byte("after\n")); err != nil {
		t.Fatalf("weeklyLogWriter.Write() after failed rotation error = %v, want nil", err)
	}
	if err := writer.Close(); err != nil {
		t.Fatal(err)
	}

	requireLogTestContents(t, path, "before\nafter\n")
	if !strings.Contains(diagnostics.String(), "weekly_log_rotation_failed") || !strings.Contains(diagnostics.String(), "injected rename failure") {
		t.Errorf("rotation diagnostic = %q, want action and injected error", diagnostics.String())
	}
	if strings.Contains(readLogTestFile(t, path), "weekly log rotation failed") {
		t.Error("rotation diagnostic recursively entered active log")
	}
}

func TestSetupLoggingKeepsFilenameAndJSONFormat(t *testing.T) {
	logger := log.StandardLogger()
	previousOutput := logger.Out
	previousFormatter := logger.Formatter
	previousLevel := logger.Level
	t.Cleanup(func() {
		logger.SetOutput(previousOutput)
		logger.SetFormatter(previousFormatter)
		logger.SetLevel(previousLevel)
	})

	directory := filepath.Join(t.TempDir(), "nested", "logs")
	writer, err := SetupLogging(directory, "hardlink", "v-test")
	if err != nil {
		t.Fatal(err)
	}
	log.WithField("probe", "value").Info("test record")
	if err := writer.Close(); err != nil {
		t.Fatal(err)
	}

	contents := readLogTestFile(t, filepath.Join(directory, "hardlink.log"))
	for _, want := range []string{`"buildVersion":"v-test"`, `"msg":"Logging initialized"`, `"probe":"value"`, `"msg":"test record"`} {
		if !strings.Contains(contents, want) {
			t.Errorf("hardlink.log contents missing %q: %s", want, contents)
		}
	}
	if _, err := os.Stat(filepath.Join(directory, "hardlink.1.log")); !errors.Is(err, os.ErrNotExist) {
		t.Errorf("SetupLogging() created archive during current week: %v", err)
	}
}

type logTestTimer struct {
	duration time.Duration
	ch       chan time.Time
	stopped  atomic.Bool
}

func (t *logTestTimer) C() <-chan time.Time {
	return t.ch
}

func (t *logTestTimer) Stop() bool {
	return !t.stopped.Swap(true)
}

func newLogTestWriter(t *testing.T, path string, now time.Time, overrides weeklyLogRuntime) *weeklyLogWriter {
	t.Helper()
	runtime := defaultWeeklyLogRuntime()
	runtime.now = func() time.Time { return now }
	if overrides.now != nil {
		runtime.now = overrides.now
	}
	if overrides.newTimer != nil {
		runtime.newTimer = overrides.newTimer
	}
	if overrides.rename != nil {
		runtime.rename = overrides.rename
	}
	if overrides.diagnostic != nil {
		runtime.diagnostic = overrides.diagnostic
	}
	writer, err := newWeeklyLogWriter(path, now.Location(), runtime)
	if err != nil {
		t.Fatal(err)
	}
	return writer
}

func weeklyLogTestGeneration(path string, generation int) string {
	extension := filepath.Ext(path)
	return fmt.Sprintf("%s.%d%s", strings.TrimSuffix(path, extension), generation, extension)
}

func writeLogTestFile(t *testing.T, path, contents string) {
	t.Helper()
	if err := os.WriteFile(path, []byte(contents), 0o600); err != nil {
		t.Fatal(err)
	}
}

func setLogTestModTime(t *testing.T, path string, value time.Time) {
	t.Helper()
	if err := os.Chtimes(path, value, value); err != nil {
		t.Fatal(err)
	}
}

func readLogTestFile(t *testing.T, path string) string {
	t.Helper()
	contents, err := os.ReadFile(path)
	if err != nil {
		t.Fatal(err)
	}
	return string(contents)
}

func requireLogTestContents(t *testing.T, path, want string) {
	t.Helper()
	if got := readLogTestFile(t, path); got != want {
		t.Errorf("%s contents = %q, want %q", filepath.Base(path), got, want)
	}
}

var _ io.WriteCloser = (*weeklyLogWriter)(nil)