package logger

import (
	"context"
	"log/slog"
	"os"
	"testing"
	"time"
)

func TestParseLevel(t *testing.T) {
	tests := []struct {
		name        string
		input       string
		expected    slog.Level
		expectError bool
	}{
		{"empty string", "", slog.LevelInfo, false},
		{"DEBUG upper", "DEBUG", slog.LevelDebug, false},
		{"debug lower", "debug", slog.LevelDebug, false},
		{"INFO upper", "INFO", slog.LevelInfo, false},
		{"info lower", "info", slog.LevelInfo, false},
		{"WARN upper", "WARN", slog.LevelWarn, false},
		{"warn lower", "warn", slog.LevelWarn, false},
		{"ERROR upper", "ERROR", slog.LevelError, false},
		{"error lower", "error", slog.LevelError, false},
		{"invalid level", "invalid", slog.LevelInfo, true},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			level, err := ParseLevel(tt.input)
			if tt.expectError {
				if err == nil {
					t.Errorf("expected error for input %q, got nil", tt.input)
				}
			} else {
				if err != nil {
					t.Errorf("unexpected error for input %q: %v", tt.input, err)
				}
				if level != tt.expected {
					t.Errorf("expected level %v for input %q, got %v", tt.expected, tt.input, level)
				}
			}
		})
	}
}

func TestSetLevel(t *testing.T) {
	// Store original level to restore later
	originalLevel := Level.Level()
	defer Level.Set(originalLevel)

	SetLevel(slog.LevelDebug)
	if Level.Level() != slog.LevelDebug {
		t.Errorf("expected Level to be Debug, got %v", Level.Level())
	}

	SetLevel(slog.LevelError)
	if Level.Level() != slog.LevelError {
		t.Errorf("expected Level to be Error, got %v", Level.Level())
	}
}

func TestSetOTLPLevel(t *testing.T) {
	// Store original level to restore later
	originalLevel := OTLPLevel.Level()
	defer OTLPLevel.Set(originalLevel)

	SetOTLPLevel(slog.LevelWarn)
	if OTLPLevel.Level() != slog.LevelWarn {
		t.Errorf("expected OTLPLevel to be Warn, got %v", OTLPLevel.Level())
	}

	SetOTLPLevel(slog.LevelDebug)
	if OTLPLevel.Level() != slog.LevelDebug {
		t.Errorf("expected OTLPLevel to be Debug, got %v", OTLPLevel.Level())
	}
}

func TestOTLPLevelHandler(t *testing.T) {
	// Create a mock handler that counts calls
	callCount := 0
	mockHandler := &mockHandler{
		handleFunc: func(ctx context.Context, r slog.Record) error {
			callCount++
			return nil
		},
	}

	// Set OTLP level to Warn
	originalLevel := OTLPLevel.Level()
	defer OTLPLevel.Set(originalLevel)
	OTLPLevel.Set(slog.LevelWarn)

	// Create OTLP level handler
	handler := newOTLPLevelHandler(mockHandler)

	ctx := context.Background()

	// Test that Debug and Info are filtered out
	if handler.Enabled(ctx, slog.LevelDebug) {
		t.Error("Debug level should be disabled when OTLP level is Warn")
	}
	if handler.Enabled(ctx, slog.LevelInfo) {
		t.Error("Info level should be disabled when OTLP level is Warn")
	}

	// Test that Warn and Error are enabled
	if !handler.Enabled(ctx, slog.LevelWarn) {
		t.Error("Warn level should be enabled when OTLP level is Warn")
	}
	if !handler.Enabled(ctx, slog.LevelError) {
		t.Error("Error level should be enabled when OTLP level is Warn")
	}

	// Test that Handle respects level filtering
	now := time.Now()
	debugRecord := slog.NewRecord(now, slog.LevelDebug, "debug message", 0)
	warnRecord := slog.NewRecord(now, slog.LevelWarn, "warn message", 0)

	handler.Handle(ctx, debugRecord)
	if callCount != 0 {
		t.Error("Debug record should not be passed to underlying handler")
	}

	handler.Handle(ctx, warnRecord)
	if callCount != 1 {
		t.Error("Warn record should be passed to underlying handler")
	}
}

func TestEnvironmentVariables(t *testing.T) {
	tests := []struct {
		name         string
		envVar       string
		envValue     string
		configPrefix string
		testFunc     func(t *testing.T)
	}{
		{
			name:     "LOG_LEVEL sets stderr level",
			envVar:   "LOG_LEVEL",
			envValue: "ERROR",
			testFunc: func(t *testing.T) {
				// Reset the setup state
				resetLoggerSetup()

				// Call setupStdErrHandler which should read the env var
				handler := setupStdErrHandler()
				if handler == nil {
					t.Fatal("setupStdErrHandler returned nil")
				}

				if Level.Level() != slog.LevelError {
					t.Errorf("expected Level to be Error after setting LOG_LEVEL=ERROR, got %v", Level.Level())
				}
			},
		},
		{
			name:         "Prefixed LOG_LEVEL",
			envVar:       "TEST_LOG_LEVEL",
			envValue:     "DEBUG",
			configPrefix: "TEST",
			testFunc: func(t *testing.T) {
				ConfigPrefix = "TEST"
				defer func() { ConfigPrefix = "" }()

				resetLoggerSetup()
				handler := setupStdErrHandler()
				if handler == nil {
					t.Fatal("setupStdErrHandler returned nil")
				}

				if Level.Level() != slog.LevelDebug {
					t.Errorf("expected Level to be Debug after setting TEST_LOG_LEVEL=DEBUG, got %v", Level.Level())
				}
			},
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			// Store original env value and level
			originalEnv := os.Getenv(tt.envVar)
			originalLevel := Level.Level()
			defer func() {
				os.Setenv(tt.envVar, originalEnv)
				Level.Set(originalLevel)
			}()

			// Set test environment variable
			os.Setenv(tt.envVar, tt.envValue)

			// Run the test
			tt.testFunc(t)
		})
	}
}

// mockHandler is a simple mock implementation of slog.Handler for testing
type mockHandler struct {
	handleFunc func(ctx context.Context, r slog.Record) error
}

func (m *mockHandler) Enabled(ctx context.Context, level slog.Level) bool {
	return true
}

func (m *mockHandler) Handle(ctx context.Context, r slog.Record) error {
	if m.handleFunc != nil {
		return m.handleFunc(ctx, r)
	}
	return nil
}

func (m *mockHandler) WithAttrs(attrs []slog.Attr) slog.Handler {
	return m
}

func (m *mockHandler) WithGroup(name string) slog.Handler {
	return m
}

// resetLoggerSetup resets the sync.Once instances for testing
func resetLoggerSetup() {
	// Reset package-level variables
	textLogger = nil
	otlpLogger = nil
	multiLogger = nil

	// Note: We can't easily reset sync.Once instances in tests,
	// but for the specific test we're doing (environment variable parsing)
	// we can test the setupStdErrHandler function directly
}