package logging

import (
	"context"
	"io"
	"log/slog"
	"os"
	"path/filepath"
	"strings"
	"testing"

	"github.com/lmittmann/tint"
)

// saveGlobals restores the package level and the default slog logger after a
// test that changes them.
func saveGlobals(t *testing.T) {
	t.Helper()
	level := logLevel.Level()
	def := slog.Default()
	t.Cleanup(func() {
		logLevel.Set(level)
		slog.SetDefault(def)
		Shutdown()
	})
}

func TestLevels(t *testing.T) {
	saveGlobals(t)
	slog.SetDefault(slog.New(slog.NewTextHandler(io.Discard, nil)))

	SetLevel(slog.LevelInfo)
	if IsDebugEnabled() {
		t.Fatal("debug enabled at info level")
	}
	EnableDebug()
	if !IsDebugEnabled() {
		t.Fatal("EnableDebug did not enable debug")
	}

	// EnableDebug must not raise a level that is already more verbose.
	SetLevel(slog.LevelDebug - 4)
	EnableDebug()
	if got := logLevel.Level(); got != slog.LevelDebug-4 {
		t.Fatalf("level = %v, want %v", got, slog.LevelDebug-4)
	}

	SetLevel(slog.LevelError)
	if IsDebugEnabled() {
		t.Fatal("debug enabled at error level")
	}
}

// wrapper is a handler that wraps another, as middleware handlers do.
type wrapper struct{ slog.Handler }

func TestIsJSONHandler(t *testing.T) {
	tests := []struct {
		name string
		h    slog.Handler
		want bool
	}{
		{"json", slog.NewJSONHandler(io.Discard, nil), true},
		{"text", slog.NewTextHandler(io.Discard, nil), false},
		{"tint", tint.NewTextHandler(io.Discard, nil), false},
		{"nil", nil, false},
		{"json with attrs", slog.NewJSONHandler(io.Discard, nil).WithAttrs(
			[]slog.Attr{slog.String("k", "v")}), true},
		// Only slog's own JSON handler is recognised, not one wrapped in another.
		{"wrapped json", wrapper{slog.NewJSONHandler(io.Discard, nil)}, false},
	}
	for _, tc := range tests {
		t.Run(tc.name, func(t *testing.T) {
			if got := IsJSONHandler(tc.h); got != tc.want {
				t.Fatalf("IsJSONHandler = %v, want %v", got, tc.want)
			}
		})
	}
}

func TestLogToFileWritesJSON(t *testing.T) {
	saveGlobals(t)
	SetLevel(slog.LevelInfo)
	path := filepath.Join(t.TempDir(), "app.log")

	if err := LogToFile(path); err != nil {
		t.Fatal(err)
	}
	if st, err := os.Stat(path); err != nil {
		t.Fatal(err)
	} else if perm := st.Mode().Perm(); perm != 0o600 {
		t.Errorf("log file permissions = %o, want 600", perm)
	}
	if !IsJSONHandler(slog.Default().Handler()) {
		t.Fatal("default handler is not JSON after LogToFile")
	}
	slog.Info("hello file", "k", "v")
	slog.Debug("hidden")

	//nolint:gosec // G304: reading a file the test created in t.TempDir
	data, err := os.ReadFile(path)
	if err != nil {
		t.Fatal(err)
	}
	s := string(data)
	if !strings.Contains(s, `"msg":"hello file"`) || !strings.Contains(s, `"k":"v"`) {
		t.Fatalf("log file missing entry: %s", s)
	}
	if strings.Contains(s, "hidden") {
		t.Fatalf("debug line written at info level: %s", s)
	}
}

func TestLogToFileBadPath(t *testing.T) {
	saveGlobals(t)
	if err := LogToFile(filepath.Join(t.TempDir(), "missing", "app.log")); err == nil {
		t.Fatal("expected an error for a path in a missing directory")
	}
}

func TestLogToFileTracksFile(t *testing.T) {
	saveGlobals(t)
	if err := LogToFile(filepath.Join(t.TempDir(), "app.log")); err != nil {
		t.Fatal(err)
	}
	if !IsFileLogger() {
		t.Fatal("IsFileLogger() = false after LogToFile")
	}
	if err := Shutdown(); err != nil {
		t.Fatal(err)
	}
	if IsFileLogger() {
		t.Fatal("IsFileLogger() = true after Shutdown")
	}
}

func TestShutdownWithoutFile(t *testing.T) {
	if err := Shutdown(); err != nil {
		t.Fatal(err)
	}
	if IsFileLogger() {
		t.Fatal("IsFileLogger() = true with no file")
	}
}

func TestLogToTerminal(t *testing.T) {
	saveGlobals(t)
	LogToTerminal()
	h := slog.Default().Handler()
	if IsJSONHandler(h) {
		t.Fatal("terminal handler reported as JSON")
	}
	SetLevel(slog.LevelWarn)
	if h.Enabled(context.Background(), slog.LevelInfo) {
		t.Fatal("terminal handler ignores the package level")
	}
}