package scalebank

import (
	_ "embed"
	"encoding/json"
	"fmt"
	"strconv"
	"sync"

	"github.com/google/uuid"
)

//go:embed curated.json
var curatedJSON []byte

var (
	bankNS = uuid.MustParse("6b1e9c2a-4d5f-4a8b-9c0d-1e2f3a4b5c6d")
	once   sync.Once
	root   *Root
	loadErr error
)

// Root is the curated bank file.
type Root struct {
	Version    int        `json:"version"`
	Categories []Category `json:"categories"`
	Scales     []Scale    `json:"scales"`
}

// Category groups scales for explore UI.
type Category struct {
	Key         string   `json:"key"`
	Title       string   `json:"title"`
	Description string   `json:"description"`
	Icon        string   `json:"icon"`
	Slugs       []string `json:"slugs"`
	Featured    []string `json:"featured"`
}

// Scale is one exploration instrument.
type Scale struct {
	Slug          string     `json:"slug"`
	Category      string     `json:"category"`
	Title         string     `json:"title"`
	Description   string     `json:"description"`
	Icon          string     `json:"icon"`
	QuestionCount int        `json:"question_count"`
	Questions     []Question `json:"questions"`
	Disclaimer    string     `json:"disclaimer"`
}

// Question is prompt + options.
type Question struct {
	Prompt  string   `json:"prompt"`
	Options []Option `json:"options"`
}

// Option is a choice.
type Option struct {
	Key  string `json:"key"`
	Text string `json:"text"`
}

// CatalogOut is explore bank payload.
type CatalogOut struct {
	Featured   []FeaturedItem `json:"featured"`
	Categories []CategoryCard `json:"categories"`
}

// FeaturedItem is icon+title tile.
type FeaturedItem struct {
	Slug        string `json:"slug"`
	Title       string `json:"title"`
	Description string `json:"description"`
	CategoryKey string `json:"category_key"`
	Icon        string `json:"icon"`
	Path        string `json:"path"`
}

// CategoryCard is a category row / detail header.
type CategoryCard struct {
	Key         string         `json:"key"`
	Title       string         `json:"title"`
	Description string         `json:"description"`
	Icon        string         `json:"icon"`
	Count       int            `json:"count"`
	Featured    []FeaturedItem `json:"featured"`
	Path        string         `json:"path"`
}

// ScaleListItem is a scale in a category list.
type ScaleListItem struct {
	Slug          string `json:"slug"`
	Title         string `json:"title"`
	Description   string `json:"description"`
	Icon          string `json:"icon"`
	QuestionCount int    `json:"question_count"`
	Path          string `json:"path"`
}

func load() (*Root, error) {
	once.Do(func() {
		var r Root
		if err := json.Unmarshal(curatedJSON, &r); err != nil {
			loadErr = err
			return
		}
		root = &r
	})
	return root, loadErr
}

// MustLoad panics only in tests if embed broken; production returns error via helpers.
func MustLoad() *Root {
	r, err := load()
	if err != nil || r == nil {
		panic(fmt.Sprintf("scalebank: %v", err))
	}
	return r
}

func bySlug(r *Root) map[string]Scale {
	m := make(map[string]Scale, len(r.Scales))
	for _, s := range r.Scales {
		m[s.Slug] = s
	}
	return m
}

func catIcon(r *Root, key string) string {
	for _, c := range r.Categories {
		if c.Key == key {
			return c.Icon
		}
	}
	return "mbti"
}

func scaleIcon(s Scale) string {
	if s.Icon != "" {
		return s.Icon
	}
	return "mbti"
}

// Has reports whether slug is in the curated bank.
func Has(slug string) bool {
	r, err := load()
	if err != nil || r == nil {
		return false
	}
	_, ok := bySlug(r)[slug]
	return ok
}

// Catalog builds featured tiles + category cards.
func Catalog() (*CatalogOut, error) {
	r, err := load()
	if err != nil {
		return nil, err
	}
	m := bySlug(r)
	out := &CatalogOut{}
	for _, c := range r.Categories {
		card := CategoryCard{
			Key: c.Key, Title: c.Title, Description: c.Description, Icon: c.Icon,
			Count: len(c.Slugs), Path: "/explore/bank/" + c.Key,
		}
		for _, slug := range c.Featured {
			s, ok := m[slug]
			if !ok {
				continue
			}
			item := FeaturedItem{
				Slug: s.Slug, Title: s.Title, Description: s.Description,
				CategoryKey: c.Key, Icon: scaleIcon(s), Path: "/scales/" + s.Slug,
			}
			card.Featured = append(card.Featured, item)
			out.Featured = append(out.Featured, item)
		}
		out.Categories = append(out.Categories, card)
	}
	return out, nil
}

// CategoryScales lists scales in a category.
func CategoryScales(key string) (*CategoryCard, []ScaleListItem, error) {
	r, err := load()
	if err != nil {
		return nil, nil, err
	}
	m := bySlug(r)
	for _, c := range r.Categories {
		if c.Key != key {
			continue
		}
		card := CategoryCard{
			Key: c.Key, Title: c.Title, Description: c.Description, Icon: c.Icon,
			Count: len(c.Slugs), Path: "/explore/bank/" + c.Key,
		}
		items := make([]ScaleListItem, 0, len(c.Slugs))
		for _, slug := range c.Slugs {
			s, ok := m[slug]
			if !ok {
				continue
			}
			items = append(items, ScaleListItem{
				Slug: s.Slug, Title: s.Title, Description: s.Description, Icon: scaleIcon(s),
				QuestionCount: s.QuestionCount, Path: "/scales/" + s.Slug,
			})
		}
		return &card, items, nil
	}
	return nil, nil, fmt.Errorf("category not found")
}

// Get returns scale detail questions in repository-compatible shape fields.
func Get(slug string) (*Scale, error) {
	r, err := load()
	if err != nil {
		return nil, err
	}
	s, ok := bySlug(r)[slug]
	if !ok {
		return nil, fmt.Errorf("scale not found")
	}
	cp := s
	return &cp, nil
}

// QuestionID stable id for answer keys.
func QuestionID(slug string, index int) uuid.UUID {
	return uuid.NewSHA1(bankNS, []byte(fmt.Sprintf("%s/%d", slug, index)))
}

// ScoreSum maps option keys (1..n) to a soft exploration band.
func ScoreSum(answers map[string]string, questionCount int) (styleKey, label string, score, ceiling int) {
	sum := 0
	maxOpt := 1
	for _, v := range answers {
		n, err := strconv.Atoi(v)
		if err != nil || n < 1 {
			continue
		}
		sum += n
		if n > maxOpt {
			maxOpt = n
		}
	}
	ceiling = questionCount * maxOpt
	if ceiling <= 0 {
		ceiling = questionCount * 5
	}
	pct := 0
	if ceiling > 0 {
		pct = sum * 100 / ceiling
	}
	switch {
	case pct >= 75:
		return "high", "感受偏强烈型", sum, ceiling
	case pct >= 45:
		return "mid", "节奏适中型", sum, ceiling
	default:
		return "low", "感受偏轻柔型", sum, ceiling
	}
}