package slog

import (
	"bytes"
	"errors"
	"os"
	"strings"
	"testing"
)

type stubLoggerWriter struct {
	printErr   error
	closeErr   error
	printCalls int
	closeCalls int
}

func (w *stubLoggerWriter) Close() error {
	w.closeCalls++
	return w.closeErr
}

func (w *stubLoggerWriter) Write(p []byte) (int, error) {
	return len(p), nil
}

func (w *stubLoggerWriter) Print(_ LogLevel, _ string, _ []*MethodTraceback, _ ...any) error {
	w.printCalls++
	return w.printErr
}

func TestLoggerCloseReturnsJoinedErrorsWithoutRelogging(t *testing.T) {
	firstErr := errors.New("first close failed")
	secondErr := errors.New("second close failed")
	first := &stubLoggerWriter{closeErr: firstErr}
	second := &stubLoggerWriter{closeErr: secondErr}

	logger := CreateLogger().AddWriters(first, second)
	err := logger.Close()
	if !errors.Is(err, firstErr) {
		t.Fatalf("Close() error should include first writer error, got %v", err)
	}
	if !errors.Is(err, secondErr) {
		t.Fatalf("Close() error should include second writer error, got %v", err)
	}
	if first.printCalls != 0 || second.printCalls != 0 {
		t.Fatalf("Close() should not log through writers again, got print calls first=%d second=%d", first.printCalls, second.printCalls)
	}
	if first.closeCalls != 1 || second.closeCalls != 1 {
		t.Fatalf("Close() should close each writer once, got close calls first=%d second=%d", first.closeCalls, second.closeCalls)
	}
	if err := logger.Close(); err != nil {
		t.Fatalf("second Close() should be a no-op, got %v", err)
	}
}

func TestLoggerPrintDoesNotRecurseOnWriterError(t *testing.T) {
	oldStderr := os.Stderr
	stderrFile, err := os.CreateTemp(t.TempDir(), "stderr")
	if err != nil {
		t.Fatalf("CreateTemp() error = %v", err)
	}
	os.Stderr = stderrFile
	t.Cleanup(func() {
		os.Stderr = oldStderr
		_ = stderrFile.Close()
	})

	bad := &stubLoggerWriter{printErr: errors.New("print failed")}
	good := &stubLoggerWriter{}

	logger := CreateLogger().AddWriters(bad, good)
	logger.Error("boom")

	if bad.printCalls != 1 {
		t.Fatalf("bad writer should be called once, got %d", bad.printCalls)
	}
	if good.printCalls != 1 {
		t.Fatalf("good writer should be called once, got %d", good.printCalls)
	}
}

func TestCreateTextWriterCloseOnNonCloserIsNoOp(t *testing.T) {
	writer := CreateTextWriter(&bytes.Buffer{}, false, false)
	if err := writer.Close(); err != nil {
		t.Fatalf("Close() error = %v", err)
	}
}

func TestCreateTextWriterDoesNotCloseExternalCloser(t *testing.T) {
	file, err := os.CreateTemp(t.TempDir(), "text-writer")
	if err != nil {
		t.Fatalf("CreateTemp() error = %v", err)
	}
	t.Cleanup(func() {
		_ = file.Close()
	})

	writer := CreateTextWriter(file, false, false)
	if err := writer.Close(); err != nil {
		t.Fatalf("Close() error = %v", err)
	}
	if _, err := file.WriteString("still open"); err != nil {
		t.Fatalf("CreateTextWriter() should not close external writers, got %v", err)
	}
}

func TestCreateJsonWriterCloseOnNonCloserIsNoOp(t *testing.T) {
	writer := CreateJsonWriter(&bytes.Buffer{}, false)
	if err := writer.Close(); err != nil {
		t.Fatalf("Close() error = %v", err)
	}
}

func TestCreateJsonWriterDoesNotCloseExternalCloser(t *testing.T) {
	file, err := os.CreateTemp(t.TempDir(), "json-writer")
	if err != nil {
		t.Fatalf("CreateTemp() error = %v", err)
	}
	t.Cleanup(func() {
		_ = file.Close()
	})

	writer := CreateJsonWriter(file, false)
	if err := writer.Close(); err != nil {
		t.Fatalf("Close() error = %v", err)
	}
	if _, err := file.WriteString("still open"); err != nil {
		t.Fatalf("CreateJsonWriter() should not close external writers, got %v", err)
	}
}

func TestCreateTextStdoutWriterDoesNotCloseStdout(t *testing.T) {
	stdoutFile := swapStdout(t)

	writer := CreateTextStdoutWriter(false, false)
	if err := writer.Close(); err != nil {
		t.Fatalf("Close() error = %v", err)
	}
	if _, err := stdoutFile.WriteString("still open"); err != nil {
		t.Fatalf("stdout writer Close() should not close stdout, got %v", err)
	}
}

func TestCreateJsonStdoutWriterDoesNotCloseStdout(t *testing.T) {
	stdoutFile := swapStdout(t)

	writer := CreateJsonStdoutWriter(false)
	if err := writer.Close(); err != nil {
		t.Fatalf("Close() error = %v", err)
	}
	if _, err := stdoutFile.WriteString("still open"); err != nil {
		t.Fatalf("stdout writer Close() should not close stdout, got %v", err)
	}
}

func TestGetFullTracebackSkipsRuntimeAndSlogFrames(t *testing.T) {
	tracebacks := captureTracebackForTest()
	if len(tracebacks) == 0 {
		t.Fatal("expected at least one traceback frame")
	}

	first := tracebacks[0]
	if first.Method != "captureTracebackForTest" {
		t.Fatalf("first frame should be the nearest user frame, got %s", first.Method)
	}
	for _, tb := range tracebacks {
		if strings.HasPrefix(tb.Signature, "runtime.") {
			t.Fatalf("runtime frame should be filtered out, got %s", tb.Signature)
		}
		if _, ok := internalTracebackMethods[tb.Method]; ok {
			t.Fatalf("internal slog frame should be filtered out, got %s", tb.Signature)
		}
	}
}

func TestGetTracebackReturnsNearestUserFrame(t *testing.T) {
	tb := captureSingleTracebackForTest()
	if tb == nil {
		t.Fatal("expected traceback frame")
	}
	if tb.Method != "captureSingleTracebackForTest" {
		t.Fatalf("expected nearest user frame, got %s", tb.Method)
	}
	if strings.HasPrefix(tb.Signature, "runtime.") {
		t.Fatalf("runtime frame should be filtered out, got %s", tb.Signature)
	}
	if _, ok := internalTracebackMethods[tb.Method]; ok {
		t.Fatalf("internal slog frame should be filtered out, got %s", tb.Signature)
	}
}

func swapStdout(t *testing.T) *os.File {
	t.Helper()

	oldStdout := os.Stdout
	stdoutFile, err := os.CreateTemp(t.TempDir(), "stdout")
	if err != nil {
		t.Fatalf("CreateTemp() error = %v", err)
	}
	os.Stdout = stdoutFile
	t.Cleanup(func() {
		os.Stdout = oldStdout
		_ = stdoutFile.Close()
	})
	return stdoutFile
}

func captureTracebackForTest() []*MethodTraceback {
	return getFullTraceback(0)
}

func captureSingleTracebackForTest() *MethodTraceback {
	return getTraceback()
}