package logging

import (
	"context"
	"errors"
	"log/slog"
)

// MultiHandler sends log records to multiple handlers.
type MultiHandler struct {
	handlers []slog.Handler
}

func NewMultiHandler(handlers ...slog.Handler) *MultiHandler {
	return &MultiHandler{handlers: handlers}
}

// Enabled reports whether any handler handles records at the given level.
func (h *MultiHandler) Enabled(ctx context.Context, level slog.Level) bool {
	for _, handler := range h.handlers {
		if handler.Enabled(ctx, level) {
			return true
		}
	}
	return false
}

// Handle sends the record to all enabled handlers.
// It continues processing all handlers even if one fails, and returns
// a combined error of all failures using errors.Join.
func (h *MultiHandler) Handle(ctx context.Context, r slog.Record) error {
	var errs []error
	for _, handler := range h.handlers {
		if handler.Enabled(ctx, r.Level) {
			if err := handler.Handle(ctx, r.Clone()); err != nil {
				errs = append(errs, err)
			}
		}
	}
	return errors.Join(errs...)
}

// WithAttrs returns a new MultiHandler with the given attributes added to all handlers.
func (h *MultiHandler) WithAttrs(attrs []slog.Attr) slog.Handler {
	handlers := make([]slog.Handler, len(h.handlers))
	for i, handler := range h.handlers {
		handlers[i] = handler.WithAttrs(attrs)
	}
	return &MultiHandler{handlers: handlers}
}

// WithGroup returns a new MultiHandler with the given group name applied to all handlers.
func (h *MultiHandler) WithGroup(name string) slog.Handler {
	handlers := make([]slog.Handler, len(h.handlers))
	for i, handler := range h.handlers {
		handlers[i] = handler.WithGroup(name)
	}
	return &MultiHandler{handlers: handlers}
}

var _ slog.Handler = (*MultiHandler)(nil)