package logger

import (
	"context"
	"fmt"
	"log/slog"
	"os"
)

type contextKey struct{}

// New constructs a root logger for the configured format and level.
func New(format, level string) *slog.Logger {
	var parsed slog.Level
	if err := parsed.UnmarshalText([]byte(level)); err != nil {
		_, _ = fmt.Fprintf(os.Stderr, "invalid log level %q, falling back to info\n", level)
		parsed = slog.LevelInfo
	}

	opts := &slog.HandlerOptions{Level: parsed}
	if format == "json" {
		return slog.New(slog.NewJSONHandler(os.Stdout, opts))
	}
	return slog.New(slog.NewTextHandler(os.Stdout, opts))
}

// WithLogger attaches a logger to the provided context.
func WithLogger(ctx context.Context, l *slog.Logger) context.Context {
	return context.WithValue(ctx, contextKey{}, l)
}

// FromContext retrieves a logger from context and falls back to slog.Default().
func FromContext(ctx context.Context) *slog.Logger {
	if l, ok := ctx.Value(contextKey{}).(*slog.Logger); ok && l != nil {
		return l
	}
	return slog.Default()
}