package services

import (
	"errors"
	"strings"
	"time"

	"gorm.io/gorm"

	"fotbal-club/internal/models"
)

// EngagementService encapsulates points, XP, achievements, and rewards

type EngagementService struct {
	DB *gorm.DB
}

// AwardPointsCapped applies simple anti-abuse caps per reason.
// - poll_vote: max 1 award per day
// - comment_create: max 10 awards per day
// - newsletter_subscribe: once per lifetime
func (s *EngagementService) AwardPointsCapped(userID uint, delta int64, reason string, meta map[string]interface{}) (*models.UserProfile, error) {
    if userID == 0 || delta == 0 { return nil, nil }
    if !s.canAwardMore(userID, strings.TrimSpace(reason)) {
        return s.EnsureProfile(userID) // return current profile without adding
    }
    return s.AwardPoints(userID, delta, reason, meta)
}

func (s *EngagementService) canAwardMore(userID uint, reason string) bool {
    now := time.Now()
    startOfDay := time.Date(now.Year(), now.Month(), now.Day(), 0, 0, 0, 0, now.Location())
    switch reason {
    case "poll_vote":
        var cnt int64
        _ = s.DB.Model(&models.PointsTransaction{}).
            Where("user_id = ? AND reason = ? AND created_at >= ?", userID, "poll_vote", startOfDay).
            Count(&cnt).Error
        return cnt < 1
    case "comment_create":
        var cnt int64
        _ = s.DB.Model(&models.PointsTransaction{}).
            Where("user_id = ? AND reason = ? AND created_at >= ?", userID, "comment_create", startOfDay).
            Count(&cnt).Error
        return cnt < 10
    case "newsletter_subscribe":
        var cnt int64
        _ = s.DB.Model(&models.PointsTransaction{}).
            Where("user_id = ? AND reason = ?", userID, "newsletter_subscribe").
            Count(&cnt).Error
        return cnt == 0
    default:
        return true
    }
}

func NewEngagementService(db *gorm.DB) *EngagementService { return &EngagementService{DB: db} }

// EnsureProfile creates a profile if missing
func (s *EngagementService) EnsureProfile(userID uint) (*models.UserProfile, error) {
	var up models.UserProfile
	if err := s.DB.Where("user_id = ?", userID).First(&up).Error; err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			up = models.UserProfile{UserID: userID, Points: 0, Level: 1, XP: 0}
			if err := s.DB.Create(&up).Error; err != nil { return nil, err }
			return &up, nil
		}
		return nil, err
	}
	return &up, nil
}

// AwardPoints adds points/xp and logs transaction; returns updated profile
func (s *EngagementService) AwardPoints(userID uint, delta int64, reason string, meta map[string]interface{}) (*models.UserProfile, error) {
	if userID == 0 || delta == 0 { return nil, nil }
	if _, err := s.EnsureProfile(userID); err != nil { return nil, err }
	pt := models.PointsTransaction{ UserID: userID, Delta: delta, XPDelta: delta, Reason: strings.TrimSpace(reason) }
	if meta != nil { pt.Meta = meta }
	if err := s.DB.Create(&pt).Error; err != nil { return nil, err }
	// Update profile atomically
	if err := s.DB.Model(&models.UserProfile{}).Where("user_id = ?", userID).
		Updates(map[string]interface{}{
			"points": gorm.Expr("points + ?", delta),
			"xp":     gorm.Expr("xp + ?", delta),
			"updated_at": time.Now(),
		}).Error; err != nil { return nil, err }
	// Recompute level
	var up models.UserProfile
	if err := s.DB.Where("user_id = ?", userID).First(&up).Error; err != nil { return nil, err }
	lvl := ComputeLevel(up.XP)
	if lvl != up.Level {
		_ = s.DB.Model(&models.UserProfile{}).Where("user_id = ?", userID).Update("level", lvl).Error
		up.Level = lvl
	}
	return &up, nil
}

// ComputeLevel returns level for given XP (simple quadratic growth)
func ComputeLevel(xp int64) int {
	// Level 1 at 0 xp, each level requires +100 * level xp increment approximately
	lvl := 1
	threshold := int64(100)
	remaining := xp
	for remaining >= threshold {
		remaining -= threshold
		lvl++
		threshold += int64(100)
		if lvl > 200 { break }
	}
	if lvl < 1 { lvl = 1 }
	return lvl
}

// CheckAndAwardAchievements evaluates basic achievements and awards when reached
func (s *EngagementService) CheckAndAwardAchievements(userID uint) error {
	if userID == 0 { return nil }
	// Preload completed achievements for user
	var done []models.UserAchievement
	_ = s.DB.Where("user_id = ?", userID).Find(&done).Error
	doneSet := map[uint]bool{}
	for _, ua := range done { doneSet[ua.AchievementID] = true }

	// Ensure default achievements exist
	defaults := []models.Achievement{
		{Code: "first_comment", Title: "První komentář", Description: "Napsal/a jste první komentář.", Points: 10, XP: 10, Active: true},
		{Code: "first_vote", Title: "První hlasování", Description: "Poprvé jste hlasoval/a v anketě.", Points: 8, XP: 8, Active: true},
		{Code: "newsletter_sub", Title: "Odběr novinek", Description: "Přihlášení k odběru newsletteru.", Points: 12, XP: 12, Active: true},
		{Code: "comments_10", Title: "Komentátor", Description: "10 komentářů!", Points: 20, XP: 20, Active: true},
		{Code: "votes_10", Title: "Hlasující", Description: "10 hlasování!", Points: 20, XP: 20, Active: true},
	}
	for _, a := range defaults {
		var existing models.Achievement
		if err := s.DB.Where("code = ?", a.Code).First(&existing).Error; err != nil {
			_ = s.DB.Create(&a).Error
		}
	}

	// Compute counts
	var commentCount int64
	_ = s.DB.Model(&models.Comment{}).Where("user_id = ?", userID).Count(&commentCount).Error
	var voteCount int64
	_ = s.DB.Model(&models.PollVote{}).Where("user_id = ?", userID).Count(&voteCount).Error
	var hasNewsletter bool
	if err := s.DB.Model(&models.NewsletterSubscription{}).Select("1").Where("LOWER(email) = (SELECT LOWER(email) FROM users WHERE id = ?) AND is_active = ?", userID, true).Limit(1).Scan(&hasNewsletter).Error; err != nil {
		// ignore
	}

	awardByCode := func(code string) {
		var a models.Achievement
		if err := s.DB.Where("code = ? AND active = ?", code, true).First(&a).Error; err == nil {
			var existing models.UserAchievement
			if err := s.DB.Where("user_id = ? AND achievement_id = ?", userID, a.ID).First(&existing).Error; errors.Is(err, gorm.ErrRecordNotFound) {
				_ = s.DB.Create(&models.UserAchievement{UserID: userID, AchievementID: a.ID}).Error
				_, _ = s.AwardPoints(userID, a.Points, "achievement:"+code, map[string]interface{}{"achievement_id": a.ID})
			}
		}
	}

	if commentCount >= 1 { awardByCode("first_comment") }
	if voteCount >= 1 { awardByCode("first_vote") }
	if hasNewsletter { awardByCode("newsletter_sub") }
	if commentCount >= 10 { awardByCode("comments_10") }
	if voteCount >= 10 { awardByCode("votes_10") }
	return nil
}