package service

import (
	"errors"
	"fmt"
	"time"

	"github.com/sundynix/pets-be/internal/model"
)

// ErrAIQuotaExceeded 今日 AI 次数用完
var ErrAIQuotaExceeded = errors.New("今日 AI 次数已用完")

// AI 调用是真金白银，不设上限等于把钱包交给用户。
// 额度按「用户 + 自然日」计，从后台配置读，改完立刻生效。
const (
	aiKindChat    = "chat"    // 问问 AI
	aiKindSymptom = "symptom" // 异常观察评估
	aiKindPlan    = "plan"    // AI 生成计划
)

// aiQuotaConfig 从后台配置取每日额度。取不到就用保守默认值，
// 绝不「取不到就不限制」——那正是配置出问题时最不该发生的事。
func (s *Service) aiQuotaConfig() model.AIQuotaConfig {
	var c model.AIQuotaConfig
	if err := s.db.First(&c, "id = ?", "1").Error; err != nil {
		return model.AIQuotaConfig{DailyChat: 20, DailySymptom: 10, DailyPlan: 5, Enabled: true}
	}
	return c
}

// aiDailyLimit 某类 AI 功能的每日上限；<=0 表示不限
func (s *Service) aiDailyLimit(kind string) (int, bool) {
	c := s.aiQuotaConfig()
	if !c.Enabled {
		return 0, false
	}
	switch kind {
	case aiKindChat:
		return c.DailyChat, true
	case aiKindSymptom:
		return c.DailySymptom, true
	case aiKindPlan:
		return c.DailyPlan, true
	}
	return 0, false
}

// consumeAIQuota 扣一次额度。超限返回 ErrAIQuotaExceeded，调用方要在真正
// 请求大模型之前调用它——扣完再调，失败也算用掉一次，避免刷接口空转烧钱。
func (s *Service) consumeAIQuota(userID, kind string) error {
	limit, on := s.aiDailyLimit(kind)
	if !on || limit <= 0 {
		return nil
	}
	day := time.Now().Format("2006-01-02")
	var u model.AIUsage
	err := s.db.Where("user_id = ? AND day = ? AND kind = ?", userID, day, kind).First(&u).Error
	if err == nil {
		if u.Count >= limit {
			return fmt.Errorf("%w（每天 %d 次，明天恢复）", ErrAIQuotaExceeded, limit)
		}
		return s.db.Model(&model.AIUsage{}).Where("id = ?", u.ID).
			UpdateColumn("count", u.Count+1).Error
	}
	return s.db.Create(&model.AIUsage{UserID: userID, Day: day, Kind: kind, Count: 1}).Error
}

// AIQuotaLeft 返回各类今日剩余次数，给小程序显示
func (s *Service) AIQuotaLeft(userID string) map[string]any {
	c := s.aiQuotaConfig()
	day := time.Now().Format("2006-01-02")
	var rows []model.AIUsage
	s.db.Where("user_id = ? AND day = ?", userID, day).Find(&rows)
	used := map[string]int{}
	for _, r := range rows {
		used[r.Kind] = r.Count
	}
	left := func(limit int, kind string) int {
		if !c.Enabled || limit <= 0 {
			return -1 // -1 表示不限
		}
		if n := limit - used[kind]; n > 0 {
			return n
		}
		return 0
	}
	return map[string]any{
		"enabled": c.Enabled,
		"chat":    left(c.DailyChat, aiKindChat),
		"symptom": left(c.DailySymptom, aiKindSymptom),
		"plan":    left(c.DailyPlan, aiKindPlan),
	}
}

// GetAIQuotaConfig / SaveAIQuotaConfig 后台读写
func (s *Service) GetAIQuotaConfig() model.AIQuotaConfig { return s.aiQuotaConfig() }

func (s *Service) SaveAIQuotaConfig(in model.AIQuotaConfig) (model.AIQuotaConfig, error) {
	c := s.aiQuotaConfig()
	c.ID = "1"
	c.Enabled = in.Enabled
	c.DailyChat = maxInt(in.DailyChat, 0)
	c.DailySymptom = maxInt(in.DailySymptom, 0)
	c.DailyPlan = maxInt(in.DailyPlan, 0)
	if err := s.db.Save(&c).Error; err != nil {
		return c, err
	}
	return c, nil
}