package channel

import (
	"fmt"
	"sync"

	"gorm.io/gorm"

	"github.com/wangjia/pay/internal/model"
)

// Registry 按商户缓存已构造的渠道实例，避免每次下单都重新加载密钥。
type Registry struct {
	db    *gorm.DB
	mu    sync.RWMutex
	cache map[uint64]Channel
}

func NewRegistry(db *gorm.DB) *Registry {
	return &Registry{db: db, cache: make(map[uint64]Channel)}
}

// ByMerchantID 取（或构造）指定商户的渠道。
func (r *Registry) ByMerchantID(id uint64) (Channel, *model.Merchant, error) {
	var m model.Merchant
	if err := r.db.First(&m, "id = ? AND enabled = ?", id, true).Error; err != nil {
		return nil, nil, fmt.Errorf("商户不存在或已停用: %w", err)
	}
	ch, err := r.get(&m)
	return ch, &m, err
}

// AlipayByAppID 异步回调时用 app_id 反查商户并取其渠道（用于验签）。
func (r *Registry) AlipayByAppID(appID string) (Channel, *model.Merchant, error) {
	if appID == "" {
		return nil, nil, fmt.Errorf("回调缺少 app_id")
	}
	var m model.Merchant
	if err := r.db.First(&m, "channel = ? AND app_id = ? AND enabled = ?", "alipay", appID, true).Error; err != nil {
		return nil, nil, fmt.Errorf("找不到 app_id=%s 对应的支付宝商户: %w", appID, err)
	}
	ch, err := r.get(&m)
	return ch, &m, err
}

func (r *Registry) get(m *model.Merchant) (Channel, error) {
	r.mu.RLock()
	if ch, ok := r.cache[m.ID]; ok {
		r.mu.RUnlock()
		return ch, nil
	}
	r.mu.RUnlock()

	ch, err := Build(m)
	if err != nil {
		return nil, err
	}
	r.mu.Lock()
	r.cache[m.ID] = ch
	r.mu.Unlock()
	return ch, nil
}

// Invalidate 商户凭证变更后清缓存（预留给管理接口）。
func (r *Registry) Invalidate(id uint64) {
	r.mu.Lock()
	delete(r.cache, id)
	r.mu.Unlock()
}