package logz

import "context"

// ctxRequestIDKey is the context key for the request correlation ID.
type ctxRequestIDKey struct{}

// ctxExtraFieldsKey is the context key for arbitrary logging fields.
type ctxExtraFieldsKey struct{}

// WithRequestID adds a request correlation ID to the context.
func WithRequestID(ctx context.Context, id string) context.Context {
	return context.WithValue(ctx, ctxRequestIDKey{}, id)
}

// GetRequestID retrieves the correlation ID from the context.
// Returns "" if not present or if ctx is nil.
func GetRequestID(ctx context.Context) string {
	if ctx == nil {
		return ""
	}
	id, _ := ctx.Value(ctxRequestIDKey{}).(string)
	return id
}

// WithField adds a single key-value pair to the context for logging.
func WithField(ctx context.Context, key string, value any) context.Context {
	return WithFields(ctx, map[string]any{key: value})
}

// WithFields adds multiple key-value pairs to the context for logging.
// Merges with any existing fields — does not overwrite the whole map.
func WithFields(ctx context.Context, fields map[string]any) context.Context {
	existing, _ := ctx.Value(ctxExtraFieldsKey{}).(map[string]any)
	newMap := make(map[string]any, len(existing)+len(fields))
	for k, v := range existing {
		newMap[k] = v
	}
	for k, v := range fields {
		newMap[k] = v
	}
	return context.WithValue(ctx, ctxExtraFieldsKey{}, newMap)
}