package notice

import (
	"fmt"
	"sync"
)

type Factory struct {
	mu        sync.RWMutex       `json:"-" dc:"实例缓存读写锁"`
	configs   map[Channel]Config `json:"-" dc:"按渠道保存的初始化配置"`
	instances map[Channel]Sender `json:"-" dc:"按渠道缓存的 Sender 实例"`
}

func NewFactory(configs map[Channel]Config) *Factory {
	cloned := make(map[Channel]Config, len(configs))
	for channel, config := range configs {
		cloned[channel] = config
	}
	return &Factory{configs: cloned, instances: make(map[Channel]Sender)}
}

func (f *Factory) Get(channel Channel) (Sender, error) {
	if f == nil {
		return nil, fmt.Errorf("%w: factory is nil", ErrChannelNotConfigured)
	}
	f.mu.RLock()
	instance, ok := f.instances[channel]
	f.mu.RUnlock()
	if ok {
		return instance, nil
	}

	f.mu.Lock()
	defer f.mu.Unlock()
	if instance, ok = f.instances[channel]; ok {
		return instance, nil
	}
	config, ok := f.configs[channel]
	if !ok {
		return nil, fmt.Errorf("%w: %s", ErrChannelNotConfigured, channel)
	}
	instance, err := New(channel, config)
	if err != nil {
		return nil, err
	}
	f.instances[channel] = instance
	return instance, nil
}