package api

import (
	"encoding/json"
	"html"
	"net/http"
	"strconv"
	"strings"
	"time"
	"unicode"

	"git.golem15.com/golem15/sm-journal-plugin/models"
	"git.golem15.com/golem15/summercms/modules/backpack"
	"git.golem15.com/golem15/summercms/modules/bouncer"
	"git.golem15.com/golem15/summercms/modules/cabana"
	"git.golem15.com/golem15/summercms/modules/lagoon"
	"git.golem15.com/golem15/summercms/modules/wire"
	"gorm.io/gorm"
)

const (
	defaultPerPage = 9
	maxPerPage     = 30
)

// Index is GET /_journal/api/v1/posts. Anonymous callers see published posts
// only; an editor with access_posts may include drafts unless ?published=true.
func Index(app *backpack.App) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		r = optionalBackendPrincipal(app, r)
		db, err := gdb(app)
		if err != nil {
			writeAPIError(w, http.StatusInternalServerError, "Internal server error")
			return
		}
		pr, _ := bouncer.User(r.Context())
		editor := isEditor(pr)

		perPage := clampPerPage(r.URL.Query().Get("per_page"))
		page := max(1, atoiDefault(r.URL.Query().Get("page"), 1))

		q := db.WithContext(r.Context()).Model(&models.Post{}).
			Preload("User").Preload("Categories").Preload("Tags")

		publishedOnly := true
		if editor {
			if _, ok := r.URL.Query()["published"]; ok {
				publishedOnly = queryBool(r.URL.Query().Get("published"))
			} else {
				publishedOnly = false
			}
		}
		if publishedOnly {
			q = applyPublished(q)
		}
		if editor {
			if raw := strings.TrimSpace(r.URL.Query().Get("author")); raw != "" {
				if id, err := strconv.ParseUint(raw, 10, 64); err == nil && id > 0 {
					q = q.Where("user_id = ?", id)
				}
			}
		}
		if cat := strings.TrimSpace(r.URL.Query().Get("category")); cat != "" {
			if ids := resolveCategoryIDs(db.WithContext(r.Context()), cat); len(ids) > 0 {
				q = q.Where("id IN (SELECT post_id FROM golem15_journal_posts_categories WHERE category_id IN (?))", ids)
			} else {
				q = q.Where("1 = 0")
			}
		}
		if tag := strings.TrimSpace(r.URL.Query().Get("tag")); tag != "" {
			q = applyTagFilter(q, db.WithContext(r.Context()), tag)
		}
		search := strings.TrimSpace(r.URL.Query().Get("search"))
		if len([]rune(search)) < 3 {
			search = ""
		}
		if search != "" {
			like := "%" + escapeLike(search) + "%"
			q = q.Where(
				"(title ILIKE ? ESCAPE '\\' OR slug ILIKE ? ESCAPE '\\' OR excerpt ILIKE ? ESCAPE '\\' OR content ILIKE ? ESCAPE '\\')",
				like, like, like, like,
			)
		}

		var total int64
		if err := q.Count(&total).Error; err != nil {
			writeAPIError(w, http.StatusInternalServerError, "Internal server error")
			return
		}

		sort := strings.TrimSpace(r.URL.Query().Get("sort"))
		order := listOrder(sort, queryBool(r.URL.Query().Get("pinned_first")))
		var posts []models.Post
		if err := q.Order(order).Offset((page - 1) * perPage).Limit(perPage).Find(&posts).Error; err != nil {
			writeAPIError(w, http.StatusInternalServerError, "Internal server error")
			return
		}
		rows := make([]map[string]any, 0, len(posts))
		for i := range posts {
			rows = append(rows, serializePost(&posts[i], db.WithContext(r.Context())))
		}
		wire.WriteJSON(w, http.StatusOK, lagoon.Paginate(rows, page, perPage, total))
	}
}

// Show is GET /_journal/api/v1/posts/{slug}. Task 2 fills JOURNAL-005.
func Show(app *backpack.App) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		r = optionalBackendPrincipal(app, r)
		writeAPIError(w, http.StatusNotFound, errPostNotFound)
	}
}

// Categories is GET /_journal/api/v1/categories. Task 2 fills the PHP list.
func Categories(app *backpack.App) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		wire.WriteJSON(w, http.StatusOK, map[string]any{"data": []any{}})
	}
}

// Tags is GET /_journal/api/v1/tags. Task 2 fills the PHP list.
func Tags(app *backpack.App) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		wire.WriteJSON(w, http.StatusOK, map[string]any{"data": []any{}})
	}
}

// RSS is GET /_journal/api/v1/rss. Task 3 fills the PHP RSS contract.
func RSS(app *backpack.App) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "application/rss+xml; charset=utf-8")
		w.WriteHeader(http.StatusOK)
		_, _ = w.Write([]byte(`<?xml version="1.0" encoding="UTF-8"?><rss version="2.0"><channel></channel></rss>`))
	}
}

// Store is POST /_journal/api/v1/posts. Task 2 fills field-by-field create.
func Store(app *backpack.App) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		if _, _, ok := requireBackendPrincipal(app, w, r); !ok {
			return
		}
		writeAPIError(w, http.StatusForbidden, errInsufficientPerms)
	}
}

// Update is PUT /_journal/api/v1/posts/{id}. Task 2 fills field-by-field update.
func Update(app *backpack.App) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		if _, _, ok := requireBackendPrincipal(app, w, r); !ok {
			return
		}
		writeAPIError(w, http.StatusForbidden, errInsufficientPerms)
	}
}

// Destroy is DELETE /_journal/api/v1/posts/{id}. Task 2 fills canEdit delete.
func Destroy(app *backpack.App) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		if _, _, ok := requireBackendPrincipal(app, w, r); !ok {
			return
		}
		writeAPIError(w, http.StatusForbidden, errInsufficientPerms)
	}
}

// UploadFeaturedImage is POST /_journal/api/v1/posts/{id}/featured-images.
func UploadFeaturedImage(app *backpack.App) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		if _, _, ok := requireBackendPrincipal(app, w, r); !ok {
			return
		}
		writeAPIError(w, http.StatusForbidden, errEditPermission)
	}
}

// DeleteFeaturedImage is DELETE /_journal/api/v1/posts/{id}/featured-images/{fileId}.
func DeleteFeaturedImage(app *backpack.App) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		if _, _, ok := requireBackendPrincipal(app, w, r); !ok {
			return
		}
		writeAPIError(w, http.StatusForbidden, errEditPermission)
	}
}

func clampPerPage(raw string) int {
	n := atoiDefault(raw, defaultPerPage)
	if n < 1 {
		n = 1
	}
	if n > maxPerPage {
		return maxPerPage
	}
	return n
}

func atoiDefault(raw string, fallback int) int {
	raw = strings.TrimSpace(raw)
	if raw == "" {
		return fallback
	}
	n, err := strconv.Atoi(raw)
	if err != nil {
		return fallback
	}
	return n
}

func queryBool(raw string) bool {
	s := strings.ToLower(strings.TrimSpace(raw))
	return s == "1" || s == "true" || s == "on" || s == "yes"
}

func applyPublished(q *gorm.DB) *gorm.DB {
	return q.Where("published = ? AND published_at IS NOT NULL AND published_at < ?", true, time.Now())
}

func listOrder(sort string, pinnedFirst bool) string {
	col, dir := "published_at", "DESC"
	parts := strings.Fields(sort)
	if len(parts) > 0 {
		switch strings.ToLower(parts[0]) {
		case "published_at", "created_at", "updated_at", "title", "id":
			col = strings.ToLower(parts[0])
		}
	}
	if len(parts) > 1 && strings.EqualFold(parts[1], "asc") {
		dir = "ASC"
	}
	order := col + " " + dir + ", id DESC"
	if pinnedFirst {
		return "is_pinned DESC, " + order
	}
	return order
}

func escapeLike(s string) string {
	s = strings.ReplaceAll(s, `\`, `\\`)
	s = strings.ReplaceAll(s, `%`, `\%`)
	s = strings.ReplaceAll(s, `_`, `\_`)
	return s
}

func resolveCategoryIDs(db *gorm.DB, input string) []uint {
	var cat models.Category
	if id, err := strconv.ParseUint(input, 10, 64); err == nil && id > 0 {
		if err := db.Where("id = ?", id).Take(&cat).Error; err != nil {
			return nil
		}
	} else if err := db.Where("slug = ?", input).Take(&cat).Error; err != nil {
		return nil
	}
	ids := []uint{cat.ID}
	if cat.NestLeft == nil || cat.NestRight == nil {
		return ids
	}
	var kids []models.Category
	if err := db.Where("nest_left > ? AND nest_right < ?", *cat.NestLeft, *cat.NestRight).Find(&kids).Error; err != nil {
		return ids
	}
	for _, kid := range kids {
		ids = append(ids, kid.ID)
	}
	return ids
}

func applyTagFilter(q, db *gorm.DB, input string) *gorm.DB {
	var tag models.Tag
	if id, err := strconv.ParseUint(input, 10, 64); err == nil && id > 0 {
		if err := db.Where("id = ?", id).Take(&tag).Error; err != nil {
			return q.Where("1 = 0")
		}
	} else if err := db.Where("slug = ?", input).Take(&tag).Error; err != nil {
		return q.Where("1 = 0")
	}
	return q.Where("id IN (SELECT post_id FROM golem15_journal_posts_tags WHERE tag_id = ?)", tag.ID)
}

func serializePost(p *models.Post, db *gorm.DB) map[string]any {
	if p == nil {
		return map[string]any{}
	}
	cats := make([]map[string]any, 0, len(p.Categories))
	for _, c := range p.Categories {
		cats = append(cats, map[string]any{"id": c.ID, "name": c.Name, "slug": c.Slug})
	}
	tags := make([]map[string]any, 0, len(p.Tags))
	for _, t := range p.Tags {
		tags = append(tags, map[string]any{"id": t.ID, "name": t.Name, "slug": t.Slug})
	}
	featured := featuredImages(db, p)
	var featuredURL any
	if len(featured) > 0 {
		featuredURL = featured[0]["url"]
	}
	row := map[string]any{
		"id":                 p.ID,
		"title":              p.Title,
		"slug":               p.Slug,
		"excerpt":            p.Excerpt,
		"content":            p.Content,
		"content_html":       p.ContentHTML,
		"reading_time":       readingTime(p.ContentHTML),
		"published":          p.Published,
		"published_at":       carbonTime(p.PublishedAt),
		"is_pinned":          p.IsPinned,
		"metadata":           jsonField(p.Metadata),
		"sources":            jsonField(p.Sources),
		"author":             serializeAuthor(p.User),
		"categories":         cats,
		"tags":               tags,
		"featured_images":    featured,
		"featured_image_url": featuredURL,
		"translations":       []any{},
		"created_at":         carbonTime(p.CreatedAt),
		"updated_at":         carbonTime(p.UpdatedAt),
	}
	return row
}

func serializeAuthor(user *cabana.BackendUser) any {
	if user == nil {
		return nil
	}
	return map[string]any{
		"id":         user.ID,
		"first_name": user.FirstName,
		"last_name":  user.LastName,
		"login":      user.Login,
	}
}

func featuredImages(_ *gorm.DB, _ *models.Post) []map[string]any {
	return []map[string]any{}
}

func jsonField(raw *string) any {
	if raw == nil || strings.TrimSpace(*raw) == "" {
		return nil
	}
	var v any
	if err := json.Unmarshal([]byte(*raw), &v); err != nil {
		return *raw
	}
	return v
}

func carbonTime(t *time.Time) any {
	if t == nil {
		return nil
	}
	return wire.Time{Time: *t}
}

func readingTime(htmlSrc string) int {
	plain := stripTags(htmlSrc)
	words := 0
	inWord := false
	for _, r := range plain {
		if unicode.IsSpace(r) {
			inWord = false
			continue
		}
		if !inWord {
			words++
			inWord = true
		}
	}
	if words == 0 {
		return 0
	}
	n := (words + 199) / 200
	if n < 1 {
		return 1
	}
	return n
}

func stripTags(s string) string {
	var b strings.Builder
	inTag := false
	for _, r := range s {
		switch {
		case r == '<':
			inTag = true
		case r == '>':
			inTag = false
		case !inTag:
			b.WriteRune(r)
		}
	}
	return html.UnescapeString(b.String())
}