package starlog

import (
	"bytes"
	"context"
	"errors"
	"io"
	"strings"
	"sync/atomic"
	"testing"
	"time"
)

func TestWriteBufferFlushAfterSwitchingOff(t *testing.T) {
	var buf bytes.Buffer
	logger := NewStarlog(&buf)
	logger.SetShowStd(false)
	logger.SetShowColor(false)

	logger.SetSwitching(true)
	logger.Infoln("first")
	logger.Infoln("second")

	if got := buf.String(); strings.Contains(got, "first") || strings.Contains(got, "second") {
		t.Fatalf("logs should stay buffered while switching=true, got: %q", got)
	}

	logger.SetSwitching(false)
	got := buf.String()
	if !strings.Contains(got, "first") || !strings.Contains(got, "second") {
		t.Fatalf("buffered logs were not flushed after switching=false, got: %q", got)
	}
}

func TestAsyncQueuePushFailureFallsBackToSyncHandler(t *testing.T) {
	resetAsyncMetricsForTest()
	defer func() {
		resetAsyncMetricsForTest()
		stackMu.Lock()
		if stacks != nil {
			_ = stacks.Close()
		}
		stackStarted = false
		stacks = nil
		stackStopChan = nil
		stackDoneChan = nil
		stackMu.Unlock()
	}()

	logger := NewStarlog(nil)
	logger.SetShowStd(false)
	var handled uint64
	logger.handlerFunc = func(data LogData) {
		atomic.AddUint64(&handled, 1)
	}

	alertCalled := make(chan struct{}, 1)
	SetAsyncErrorHandler(func(err error, data LogData) {
		select {
		case alertCalled <- struct{}{}:
		default:
		}
	})

	stackMu.Lock()
	stackStarted = true
	stacks = nil
	stackStopChan = nil
	stackDoneChan = nil
	stackMu.Unlock()

	logger.Infoln("trigger async fallback")

	if atomic.LoadUint64(&handled) != 1 {
		t.Fatalf("handler should be called once via sync fallback, got: %d", handled)
	}
	if GetAsyncDropCount() == 0 {
		t.Fatalf("async drop counter should increase on push failure")
	}
	select {
	case <-alertCalled:
	default:
		t.Fatalf("async alert handler should be invoked on push failure")
	}
}

func TestStarChanStackPushClosedReturnsEOF(t *testing.T) {
	stack := newStarChanStack(1)
	if err := stack.Close(); err != nil {
		t.Fatalf("Close failed: %v", err)
	}
	if err := stack.Push("x"); err != io.EOF {
		t.Fatalf("Push on closed stack should return io.EOF, got: %v", err)
	}
}

func TestStarChanStackTryPushFullReturnsQueueFull(t *testing.T) {
	stack := newStarChanStack(1)
	if err := stack.Push("first"); err != nil {
		t.Fatalf("Push failed: %v", err)
	}
	if err := stack.TryPush("second"); !errors.Is(err, errStackFull) {
		t.Fatalf("TryPush on full queue should return errStackFull, got: %v", err)
	}
}

func TestPendingWriteLimitDropOldest(t *testing.T) {
	var buf bytes.Buffer
	logger := NewStarlog(&buf)
	logger.SetShowStd(false)
	logger.SetShowColor(false)
	logger.SetPendingWriteLimit(2)
	logger.SetPendingDropPolicy(PendingDropOldest)

	logger.SetSwitching(true)
	logger.Infoln("one")
	logger.Infoln("two")
	logger.Infoln("three")
	logger.SetSwitching(false)

	got := buf.String()
	if strings.Contains(got, "one") {
		t.Fatalf("oldest pending log should be dropped, got %q", got)
	}
	if !strings.Contains(got, "two") || !strings.Contains(got, "three") {
		t.Fatalf("newer pending logs should remain, got %q", got)
	}
	if logger.GetPendingDropCount() != 1 {
		t.Fatalf("expected one dropped pending write, got %d", logger.GetPendingDropCount())
	}
}

func TestPendingWriteLimitBlockPolicy(t *testing.T) {
	var buf bytes.Buffer
	logger := NewStarlog(&buf)
	logger.SetShowStd(false)
	logger.SetShowColor(false)
	logger.SetPendingWriteLimit(1)
	logger.SetPendingDropPolicy(PendingBlock)
	logger.SetSwitching(true)
	logger.Infoln("one")

	done := make(chan struct{})
	go func() {
		logger.Infoln("two")
		close(done)
	}()

	blocked := false
	deadline := time.Now().Add(200 * time.Millisecond)
	for time.Now().Before(deadline) {
		select {
		case <-done:
			t.Fatalf("block policy should wait while queue is full and switching=true")
		default:
		}
		if logger.GetPendingBlockCount() > 0 {
			blocked = true
			break
		}
		time.Sleep(5 * time.Millisecond)
	}
	if !blocked {
		t.Fatalf("expected pending block count to increase")
	}

	logger.SetSwitching(false)

	select {
	case <-done:
	case <-time.After(300 * time.Millisecond):
		t.Fatalf("blocked write should continue after switching=false")
	}

	got := buf.String()
	if !strings.Contains(got, "one") || !strings.Contains(got, "two") {
		t.Fatalf("both logs should be persisted, got %q", got)
	}
	if logger.GetPendingDropCount() != 0 {
		t.Fatalf("block policy should avoid drops, got %d", logger.GetPendingDropCount())
	}
	stats := logger.GetPendingStats()
	if stats.BlockCount == 0 {
		t.Fatalf("pending stats should expose block count")
	}
}

func TestPendingStatsSnapshot(t *testing.T) {
	logger := NewStarlog(nil)
	logger.SetShowStd(false)
	logger.SetPendingWriteLimit(3)
	logger.SetPendingDropPolicy(PendingDropNewest)
	logger.SetSwitching(true)
	logger.Infoln("one")
	logger.Infoln("two")

	stats := logger.GetPendingStats()
	if stats.Limit != 3 {
		t.Fatalf("unexpected limit: %d", stats.Limit)
	}
	if stats.Length != 2 {
		t.Fatalf("unexpected pending length: %d", stats.Length)
	}
	if stats.Policy != PendingDropNewest {
		t.Fatalf("unexpected policy: %v", stats.Policy)
	}
	if !stats.Switching {
		t.Fatalf("expected switching flag true in stats snapshot")
	}
	if stats.PeakLength < 2 {
		t.Fatalf("expected peak length >= 2, got %d", stats.PeakLength)
	}

	logger.SetSwitching(false)
}

type errWriter struct{}

func (w *errWriter) Write(p []byte) (int, error) {
	return 0, errors.New("write failed")
}

func TestWriteErrorObservable(t *testing.T) {
	resetAsyncMetricsForTest()
	defer resetAsyncMetricsForTest()

	logger := NewStarlog(&errWriter{})
	logger.SetShowStd(false)
	logger.SetShowColor(false)

	observed := make(chan struct{}, 1)
	SetWriteErrorHandler(func(err error, data LogData) {
		if err != nil {
			select {
			case observed <- struct{}{}:
			default:
			}
		}
	})

	logger.Infoln("write error check")

	if GetWriteErrorCount() == 0 {
		t.Fatalf("write error count should increase")
	}
	select {
	case <-observed:
	default:
		t.Fatalf("write error handler should be invoked")
	}
}

func TestAsyncHandlerPanicDoesNotCrash(t *testing.T) {
	resetAsyncMetricsForTest()
	defer func() {
		resetAsyncMetricsForTest()
		StopStacks()
	}()

	logger := NewStarlog(nil)
	logger.SetShowStd(false)
	logger.SetHandler(func(LogData) {
		panic("boom")
	})

	logger.Infoln("panic safe")
	time.Sleep(20 * time.Millisecond)

	if GetAsyncDropCount() == 0 {
		t.Fatalf("panic in async handler should be reported as drop")
	}
}

func TestEntryHandlerTimeoutFallback(t *testing.T) {
	resetAsyncMetricsForTest()
	defer func() {
		resetAsyncMetricsForTest()
		StopStacks()
	}()

	logger := NewStarlog(nil)
	logger.SetShowStd(false)
	logger.SetEntryHandler(HandlerFunc(func(context.Context, *Entry) error {
		time.Sleep(80 * time.Millisecond)
		return nil
	}))
	logger.SetEntryHandlerTimeout(10 * time.Millisecond)

	begin := time.Now()
	logger.Infoln("entry timeout")
	cost := time.Since(begin)

	if cost > 60*time.Millisecond {
		t.Fatalf("entry handler timeout should protect main path, took %v", cost)
	}
	deadline := time.Now().Add(300 * time.Millisecond)
	for time.Now().Before(deadline) {
		if GetAsyncDropCount() > 0 {
			return
		}
		time.Sleep(5 * time.Millisecond)
	}
	t.Fatalf("entry handler timeout should be observable via async drop count")
}

func TestEntryHandlerQueueFullNoFallbackDoesNotBlock(t *testing.T) {
	resetAsyncMetricsForTest()
	defer func() {
		resetAsyncMetricsForTest()
		stackMu.Lock()
		stackStarted = false
		stacks = nil
		stackStopChan = nil
		stackDoneChan = nil
		stackMu.Unlock()
	}()

	SetAsyncFallbackToSync(false)

	logger := NewStarlog(nil)
	logger.SetShowStd(false)
	var handled uint64
	logger.SetEntryHandler(HandlerFunc(func(context.Context, *Entry) error {
		atomic.AddUint64(&handled, 1)
		time.Sleep(80 * time.Millisecond)
		return nil
	}))

	stackMu.Lock()
	stackStarted = true
	stacks = newStarChanStack(1)
	stackStopChan = nil
	stackDoneChan = nil
	stackMu.Unlock()

	if err := stacks.Push(logTransfer{
		handlerFunc: func(LogData) {
			time.Sleep(80 * time.Millisecond)
		},
	}); err != nil {
		t.Fatalf("prepare full async queue failed: %v", err)
	}

	begin := time.Now()
	logger.Infoln("entry queue full")
	cost := time.Since(begin)

	if cost > 60*time.Millisecond {
		t.Fatalf("entry handler should not block when queue is full, took %v", cost)
	}
	if atomic.LoadUint64(&handled) != 0 {
		t.Fatalf("entry handler should be dropped when queue is full and fallback disabled, got %d", handled)
	}
	if GetAsyncDropCount() == 0 {
		t.Fatalf("queue-full drop should be observable")
	}
}

func TestWriteMethodNameCompatibility(t *testing.T) {
	logger := NewStarlog(nil)
	logger.StopWrite()
	if !logger.IsWriteStopped() || !logger.IsWriteStoed() {
		t.Fatalf("both write-stop getters should report true")
	}
	logger.EnableWrite()
	if logger.IsWriteStopped() || logger.IsWriteStoed() {
		t.Fatalf("EnableWrite should resume writer for both getter names")
	}
}

func TestLevelFilterAPI(t *testing.T) {
	var buf bytes.Buffer
	logger := NewStarlog(&buf)
	logger.SetShowStd(false)
	logger.SetShowColor(false)
	logger.SetShowOriginFile(false)
	logger.SetShowFuncName(false)
	logger.SetShowFlag(false)

	if !logger.IsLevelEnabled(LvDebug) {
		t.Fatalf("debug level should be enabled by default")
	}
	logger.SetLevel(LvWarning)
	if logger.GetLevel() != LvWarning {
		t.Fatalf("unexpected level threshold: %d", logger.GetLevel())
	}
	if logger.IsLevelEnabled(LvInfo) {
		t.Fatalf("info should be filtered by warning threshold")
	}
	if !logger.IsLevelEnabled(LvError) {
		t.Fatalf("error should be enabled by warning threshold")
	}

	logger.Infoln("filtered")
	logger.Warningln("visible")
	logStr := buf.String()
	if strings.Contains(logStr, "filtered") {
		t.Fatalf("info log should be filtered, got %q", logStr)
	}
	if !strings.Contains(logStr, "visible") {
		t.Fatalf("warning log should remain, got %q", logStr)
	}
}

func TestParseLevel(t *testing.T) {
	tests := map[string]int{
		"debug":    LvDebug,
		"INFO":     LvInfo,
		"notice":   LvNotice,
		"warn":     LvWarning,
		"warning":  LvWarning,
		"err":      LvError,
		"critical": LvCritical,
		"panic":    LvPanic,
		"fatal":    LvFatal,
		"7":        7,
	}
	for input, expected := range tests {
		parsed, err := ParseLevel(input)
		if err != nil {
			t.Fatalf("ParseLevel(%q) returned error: %v", input, err)
		}
		if parsed != expected {
			t.Fatalf("ParseLevel(%q)=%d, want %d", input, parsed, expected)
		}
	}

	_, err := ParseLevel("unknown-level")
	if !errors.Is(err, ErrInvalidLevel) {
		t.Fatalf("ParseLevel invalid input should return ErrInvalidLevel, got %v", err)
	}
}