package achievement

import (
	"context"
	"errors"
	"fmt"

	"gorm.io/gorm"
)

var ErrThemeNotFound = errors.New("achievement theme not found")

type Service struct {
	db *gorm.DB
}

func NewService(db *gorm.DB) *Service {
	return &Service{db: db}
}

type UserAchievement struct {
	ThemeID   uint    `json:"theme_id"`
	ThemeName string  `json:"theme_name"`
	ThemeKey  string  `json:"theme_key"`
	ThemeIcon string  `json:"theme_icon"`
	Days      int     `json:"days"`
	Current   *Level  `json:"current"`
	Next      *Level  `json:"next,omitempty"`
	Progress  float64 `json:"progress"`
}

func (s *Service) ListActiveThemes(ctx context.Context) ([]Theme, error) {
	var themes []Theme
	err := s.db.WithContext(ctx).
		Where("is_active = ?", true).
		Preload("Levels", func(db *gorm.DB) *gorm.DB {
			return db.Order("required_days ASC, sort_order ASC")
		}).
		Order("sort_order ASC, id ASC").
		Find(&themes).Error
	if err != nil {
		return nil, fmt.Errorf("list active themes: %w", err)
	}
	return themes, nil
}

func (s *Service) GetUserAchievement(ctx context.Context, themeID uint, days int) (*UserAchievement, error) {
	var theme Theme
	err := s.db.WithContext(ctx).
		Preload("Levels", func(db *gorm.DB) *gorm.DB {
			return db.Order("required_days ASC, sort_order ASC")
		}).
		First(&theme, themeID).Error
	if err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, ErrThemeNotFound
		}
		return nil, fmt.Errorf("get theme: %w", err)
	}

	if days < 0 {
		days = 0
	}

	result := &UserAchievement{
		ThemeID:   theme.ID,
		ThemeName: theme.Name,
		ThemeKey:  theme.Key,
		ThemeIcon: theme.Icon,
		Days:      days,
	}

	for i, level := range theme.Levels {
		if days >= level.RequiredDays {
			lvl := level
			result.Current = &lvl
			if i+1 < len(theme.Levels) {
				next := theme.Levels[i+1]
				result.Next = &next
			}
		}
	}

	if result.Current != nil && result.Next != nil {
		rangeTotal := result.Next.RequiredDays - result.Current.RequiredDays
		rangeDone := days - result.Current.RequiredDays
		if rangeTotal > 0 {
			result.Progress = float64(rangeDone) / float64(rangeTotal)
		}
	} else if result.Current != nil && result.Next == nil {
		result.Progress = 1.0
	}

	return result, nil
}

func (s *Service) SeedDefaults(ctx context.Context) error {
	var count int64
	if err := s.db.WithContext(ctx).Model(&Theme{}).Count(&count).Error; err != nil {
		return fmt.Errorf("count themes: %w", err)
	}
	if count > 0 {
		return nil
	}

	themes := []struct {
		Name   string
		Key    string
		Icon   string
		Levels []struct {
			Name         string
			RequiredDays int
		}
	}{
		{
			Name: "修仙", Key: "xiuxian", Icon: "⚔️",
			Levels: []struct {
				Name         string
				RequiredDays int
			}{
				{"炼体", 0}, {"练气", 3}, {"筑基", 7}, {"金丹", 30}, {"元婴", 90}, {"化神", 365},
			},
		},
		{
			Name: "军队", Key: "army", Icon: "🎖️",
			Levels: []struct {
				Name         string
				RequiredDays int
			}{
				{"新兵", 0}, {"排长", 3}, {"连长", 7}, {"营长", 30}, {"师长", 90}, {"大将", 365},
			},
		},
		{
			Name: "魔法", Key: "magic", Icon: "🔮",
			Levels: []struct {
				Name         string
				RequiredDays int
			}{
				{"学徒", 0}, {"术士", 3}, {"大术士", 7}, {"元素师", 30}, {"大魔导师", 90}, {"圣导师", 365},
			},
		},
		{
			Name: "武侠", Key: "wuxia", Icon: "🗡️",
			Levels: []struct {
				Name         string
				RequiredDays int
			}{
				{"徒弟", 0}, {"掌门弟子", 3}, {"门派高手", 7}, {"大侠", 30}, {"剑仙", 90}, {"武圣", 365},
			},
		},
		{
			Name: "电竞", Key: "esports", Icon: "🏆",
			Levels: []struct {
				Name         string
				RequiredDays int
			}{
				{"青铜", 0}, {"白银", 3}, {"黄金", 7}, {"铂金", 30}, {"钻石", 90}, {"王者", 365},
			},
		},
	}

	for i, t := range themes {
		theme := Theme{
			Name:      t.Name,
			Key:       t.Key,
			Icon:      t.Icon,
			SortOrder: i,
			IsActive:  true,
		}
		if err := s.db.WithContext(ctx).Create(&theme).Error; err != nil {
			return fmt.Errorf("seed theme %s: %w", t.Key, err)
		}
		for j, l := range t.Levels {
			level := Level{
				ThemeID:      theme.ID,
				Name:         l.Name,
				RequiredDays: l.RequiredDays,
				SortOrder:    j,
			}
			if err := s.db.WithContext(ctx).Create(&level).Error; err != nil {
				return fmt.Errorf("seed level %s/%s: %w", t.Key, l.Name, err)
			}
		}
	}

	return nil
}