package api

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"regexp"
	"strconv"
	"strings"
	"time"
	"unicode"
	"unicode/utf8"

	"git.golem15.com/golem15/sm-journal-plugin/classes"
	"git.golem15.com/golem15/sm-journal-plugin/models"
	translate "git.golem15.com/golem15/sm-translate-plugin/classes"
	"git.golem15.com/golem15/summercms/modules/bouncer"
	"git.golem15.com/golem15/summercms/modules/cabana"
	"gorm.io/gorm"
)

var slugPattern = regexp.MustCompile(`(?i)^[a-z0-9/\:_\-\*\[\]\+\?\|]*$`)

func postIsPublished(p *models.Post) bool {
	if p == nil || !p.Published || p.PublishedAt == nil {
		return false
	}
	return p.PublishedAt.Before(time.Now())
}

func canViewDraft(p *models.Post, pr *bouncer.Principal) bool {
	if p == nil || pr == nil {
		return false
	}
	if p.UserID != nil && *p.UserID == pr.ID {
		return true
	}
	return cabana.Allows(pr, []string{permAccessOtherPosts})
}

func ctypeDigit(s string) bool {
	if s == "" {
		return false
	}
	for _, r := range s {
		if r < '0' || r > '9' {
			return false
		}
	}
	return true
}

func findPostBySlugOrID(db *gorm.DB, slug string) (*models.Post, error) {
	q := postQuery(db)
	var post models.Post
	if err := q.Where("slug = ?", slug).Take(&post).Error; err == nil {
		return &post, nil
	}
	if ctypeDigit(slug) {
		id, err := strconv.ParseUint(slug, 10, 64)
		if err == nil && id > 0 {
			var byID models.Post
			if err := postQuery(db).Where("id = ?", id).Take(&byID).Error; err == nil {
				return &byID, nil
			}
		}
	}
	return nil, gorm.ErrRecordNotFound
}

func findPostByID(db *gorm.DB, raw string) (*models.Post, error) {
	id, err := strconv.ParseUint(strings.TrimSpace(raw), 10, 64)
	if err != nil || id == 0 {
		return nil, gorm.ErrRecordNotFound
	}
	var post models.Post
	if err := postQuery(db).Where("id = ?", id).Take(&post).Error; err != nil {
		return nil, err
	}
	return &post, nil
}

func postQuery(db *gorm.DB) *gorm.DB {
	return db.Model(&models.Post{}).Preload("User").Preload("Categories").Preload("Tags")
}

func loadPostAssocs(db *gorm.DB, post *models.Post) error {
	if post == nil {
		return nil
	}
	return db.Preload("User").Preload("Categories").Preload("Tags").First(post, post.ID).Error
}

func serializeSibling(p *models.Post) any {
	if p == nil {
		return nil
	}
	return map[string]any{"id": p.ID, "title": p.Title, "slug": p.Slug}
}

func previousPost(db *gorm.DB, p *models.Post) *models.Post {
	return siblingPost(db, p, true)
}

func nextPost(db *gorm.DB, p *models.Post) *models.Post {
	return siblingPost(db, p, false)
}

func siblingPost(db *gorm.DB, p *models.Post, previous bool) *models.Post {
	if p == nil {
		return nil
	}
	op, dir := "<", "DESC"
	if previous {
		op, dir = ">", "ASC"
	}
	q := applyPublished(db.Model(&models.Post{})).Where("id <> ?", p.ID)
	if p.PublishedAt != nil {
		q = q.Where(
			"(published_at "+op+" ?) OR (published_at = ? AND id "+op+" ?)",
			p.PublishedAt, p.PublishedAt, p.ID,
		)
	}
	var out models.Post
	if err := q.Order("published_at " + dir + ", id " + dir).Take(&out).Error; err != nil {
		return nil
	}
	return &out
}

func relatedPosts(db *gorm.DB, p *models.Post, editor bool) []models.Post {
	if p == nil || len(p.Categories) == 0 {
		return []models.Post{}
	}
	ids := make([]uint, 0, len(p.Categories))
	for _, c := range p.Categories {
		ids = append(ids, c.ID)
	}
	q := db.Model(&models.Post{}).
		Preload("User").Preload("Categories").Preload("Tags").
		Where("id <> ?", p.ID).
		Where("id IN (SELECT post_id FROM golem15_journal_posts_categories WHERE category_id IN (?))", ids)
	if !editor {
		q = applyPublished(q)
	}
	var rows []models.Post
	if err := q.Order("published_at DESC").Limit(3).Find(&rows).Error; err != nil {
		return []models.Post{}
	}
	return rows
}

func serializeCategoryTree(db *gorm.DB, includeEmpty bool) ([]map[string]any, error) {
	var cats []models.Category
	if err := db.Order("nest_left ASC NULLS LAST, id ASC").Find(&cats).Error; err != nil {
		return nil, err
	}
	counts := publishedPostCounts(db, "golem15_journal_posts_categories", "category_id")
	byParent := map[uint][]models.Category{}
	var roots []models.Category
	for _, c := range cats {
		if c.ParentID == nil || *c.ParentID == 0 {
			roots = append(roots, c)
			continue
		}
		byParent[*c.ParentID] = append(byParent[*c.ParentID], c)
	}
	out := make([]map[string]any, 0, len(roots))
	for i := range roots {
		if row := serializeCategoryNode(&roots[i], byParent, counts, includeEmpty); row != nil {
			out = append(out, row)
		}
	}
	return out, nil
}

func serializeCategoryNode(c *models.Category, byParent map[uint][]models.Category, counts map[uint]int64, includeEmpty bool) map[string]any {
	if c == nil {
		return nil
	}
	kids := byParent[c.ID]
	childRows := make([]map[string]any, 0, len(kids))
	for i := range kids {
		if row := serializeCategoryNode(&kids[i], byParent, counts, includeEmpty); row != nil {
			childRows = append(childRows, row)
		}
	}
	postCount := counts[c.ID]
	if !includeEmpty && postCount == 0 && len(childRows) == 0 {
		return nil
	}
	var desc any
	if c.Description != nil {
		desc = *c.Description
	}
	var parent any
	if c.ParentID != nil {
		parent = *c.ParentID
	}
	var depth any
	if c.NestDepth != nil {
		depth = *c.NestDepth
	}
	row := map[string]any{
		"id":          c.ID,
		"name":        c.Name,
		"slug":        c.Slug,
		"description": desc,
		"parent_id":   parent,
		"nest_depth":  depth,
		"post_count":  postCount,
	}
	if len(childRows) > 0 {
		row["children"] = childRows
	}
	return row
}

func serializeTagList(db *gorm.DB) ([]map[string]any, error) {
	var tags []models.Tag
	if err := db.Order("name ASC, id ASC").Find(&tags).Error; err != nil {
		return nil, err
	}
	counts := publishedPostCounts(db, "golem15_journal_posts_tags", "tag_id")
	out := make([]map[string]any, 0, len(tags))
	for _, tag := range tags {
		out = append(out, map[string]any{
			"id":         tag.ID,
			"name":       tag.Name,
			"slug":       tag.Slug,
			"post_count": counts[tag.ID],
		})
	}
	return out, nil
}

func publishedPostCounts(db *gorm.DB, pivot, fk string) map[uint]int64 {
	type row struct {
		ID    uint
		Count int64
	}
	var rows []row
	q := fmt.Sprintf(
		`SELECT p.%s AS id, COUNT(*) AS count
		 FROM %s p
		 INNER JOIN golem15_journal_posts posts ON posts.id = p.post_id
		 WHERE posts.published = TRUE AND posts.published_at IS NOT NULL AND posts.published_at < ?
		 GROUP BY p.%s`,
		fk, pivot, fk,
	)
	_ = db.Raw(q, time.Now()).Scan(&rows).Error
	out := map[uint]int64{}
	for _, r := range rows {
		out[r.ID] = r.Count
	}
	return out
}

func translationsOf(db *gorm.DB, p *models.Post) any {
	if db == nil || p == nil || p.ID == 0 {
		return []any{}
	}
	var locales []struct {
		Code      string
		IsDefault bool
	}
	if err := db.Table("golem15_translate_locales").
		Select("code, is_default").
		Where("is_enabled = ?", true).
		Find(&locales).Error; err != nil {
		return []any{}
	}
	out := map[string]any{}
	for _, loc := range locales {
		if loc.IsDefault {
			continue
		}
		attrs := map[string]any{}
		ctx := db.Statement.Context
		if ctx == nil {
			ctx = context.Background()
		}
		for _, field := range []string{"title", "slug", "content", "content_html", "excerpt", "metadata"} {
			val, ok, err := translate.TranslatedExact(ctx, db, p, field, loc.Code)
			if err != nil || !ok || val == nil {
				continue
			}
			s := strings.TrimSpace(fmt.Sprint(val))
			if s == "" {
				continue
			}
			attrs[field] = val
		}
		if len(attrs) > 0 {
			out[loc.Code] = attrs
		}
	}
	if len(out) == 0 {
		return []any{}
	}
	return out
}

func readJSONObject(r *http.Request) (map[string]any, error) {
	if r == nil || r.Body == nil {
		return map[string]any{}, nil
	}
	defer r.Body.Close()
	raw, err := io.ReadAll(io.LimitReader(r.Body, 1<<20))
	if err != nil {
		return nil, err
	}
	if len(strings.TrimSpace(string(raw))) == 0 {
		return map[string]any{}, nil
	}
	dec := json.NewDecoder(strings.NewReader(string(raw)))
	dec.UseNumber()
	var body map[string]any
	if err := dec.Decode(&body); err != nil {
		return nil, err
	}
	if body == nil {
		body = map[string]any{}
	}
	return body, nil
}

func publishedFlag(body map[string]any) bool {
	v, ok := body["published"]
	if !ok {
		return false
	}
	return asBool(v)
}

func asBool(v any) bool {
	switch t := v.(type) {
	case bool:
		return t
	case json.Number:
		n, _ := t.Int64()
		return n != 0
	case float64:
		return t != 0
	case string:
		s := strings.ToLower(strings.TrimSpace(t))
		return s == "1" || s == "true" || s == "on" || s == "yes"
	default:
		return false
	}
}

func asString(v any) string {
	if v == nil {
		return ""
	}
	switch t := v.(type) {
	case string:
		return t
	case json.Number:
		return t.String()
	default:
		return strings.TrimSpace(fmt.Sprint(v))
	}
}

func asUint(v any) (uint, bool) {
	switch t := v.(type) {
	case json.Number:
		n, err := t.Int64()
		if err != nil || n <= 0 {
			return 0, false
		}
		return uint(n), true
	case float64:
		if t <= 0 || t != float64(uint64(t)) {
			return 0, false
		}
		return uint(t), true
	case string:
		n, err := strconv.ParseUint(strings.TrimSpace(t), 10, 64)
		if err != nil || n == 0 {
			return 0, false
		}
		return uint(n), true
	default:
		return 0, false
	}
}

func parsePublishedAt(v any) (*time.Time, error) {
	if v == nil {
		return nil, nil
	}
	s := strings.TrimSpace(asString(v))
	if s == "" {
		return nil, nil
	}
	for _, layout := range []string{time.RFC3339Nano, time.RFC3339, "2006-01-02 15:04:05", "2006-01-02"} {
		if ts, err := time.Parse(layout, s); err == nil {
			return &ts, nil
		}
	}
	return nil, fmt.Errorf("invalid date")
}

func jsonPtr(v any) *string {
	if v == nil {
		return nil
	}
	switch t := v.(type) {
	case string:
		s := strings.TrimSpace(t)
		if s == "" {
			return nil
		}
		return &s
	default:
		raw, err := json.Marshal(v)
		if err != nil {
			return nil
		}
		s := string(raw)
		return &s
	}
}

func slugify(title string) string {
	s := strings.ToLower(strings.TrimSpace(title))
	var b strings.Builder
	prevDash := false
	for _, r := range s {
		switch {
		case r >= 'a' && r <= 'z', r >= '0' && r <= '9':
			b.WriteRune(r)
			prevDash = false
		case unicode.IsLetter(r) || unicode.IsNumber(r):
			b.WriteRune(unicode.ToLower(r))
			prevDash = false
		default:
			if !prevDash && b.Len() > 0 {
				b.WriteByte('-')
				prevDash = true
			}
		}
	}
	return strings.Trim(b.String(), "-")
}

func generateUniqueSlug(db *gorm.DB, title string, exceptID uint) string {
	base := slugify(title)
	if base == "" {
		base = "post"
	}
	slug := base
	for n := 1; ; n++ {
		q := db.Model(&models.Post{}).Where("slug = ?", slug)
		if exceptID > 0 {
			q = q.Where("id <> ?", exceptID)
		}
		var count int64
		_ = q.Count(&count).Error
		if count == 0 {
			return slug
		}
		slug = fmt.Sprintf("%s-%d", base, n)
	}
}

func buildNewPost(r *http.Request, db *gorm.DB, pr *bouncer.Principal, body map[string]any) (*models.Post, map[string][]string) {
	errs := map[string][]string{}
	title := strings.TrimSpace(asString(body["title"]))
	if title == "" {
		errs["title"] = []string{"The title field is required."}
	} else if utf8.RuneCountInString(title) > 255 {
		errs["title"] = []string{"The title may not be greater than 255 characters."}
	}
	content := asString(body["content"])
	if strings.TrimSpace(content) == "" {
		errs["content"] = []string{"The content field is required."}
	}
	slug := strings.TrimSpace(asString(body["slug"]))
	if slug == "" {
		slug = generateUniqueSlug(db, title, 0)
	} else if !slugPattern.MatchString(slug) {
		errs["slug"] = []string{"The slug format is invalid."}
	} else if slugTaken(db, slug, 0) {
		errs["slug"] = []string{"The slug has already been taken."}
	}
	if _, has := body["published_at"]; has {
		if _, err := parsePublishedAt(body["published_at"]); err != nil {
			errs["published_at"] = []string{"The published at is not a valid date."}
		}
	}
	if catErr := validateCategoryIDs(db, body["categories"]); catErr != nil {
		errs["categories"] = []string{catErr.Error()}
	}
	if transErr := validateTranslations(body["translations"]); transErr != nil {
		errs["translations"] = []string{transErr.Error()}
	}
	if len(errs) > 0 {
		return nil, errs
	}
	html, err := classes.FormatHTML(content)
	if err != nil {
		return nil, map[string][]string{"content": {err.Error()}}
	}
	userID := pr.ID
	post := &models.Post{
		Title:       title,
		Slug:        slug,
		Content:     content,
		ContentHTML: html,
		Excerpt:     strings.TrimSpace(asString(body["excerpt"])),
		Published:   asBool(body["published"]),
		IsPinned:    asBool(body["is_pinned"]),
		UserID:      &userID,
	}
	if _, has := body["published_at"]; has {
		ts, _ := parsePublishedAt(body["published_at"])
		post.PublishedAt = ts
	}
	if _, has := body["metadata"]; has {
		post.Metadata = jsonPtr(body["metadata"])
	}
	if _, has := body["sources"]; has {
		post.Sources = jsonPtr(body["sources"])
	}
	_ = r
	return post, nil
}

func applyPostUpdate(r *http.Request, db *gorm.DB, post *models.Post, body map[string]any) map[string][]string {
	errs := map[string][]string{}
	if _, has := body["title"]; has {
		title := strings.TrimSpace(asString(body["title"]))
		if title == "" {
			errs["title"] = []string{"The title field is required."}
		} else if utf8.RuneCountInString(title) > 255 {
			errs["title"] = []string{"The title may not be greater than 255 characters."}
		} else {
			post.Title = title
		}
	}
	if _, has := body["slug"]; has {
		slug := strings.TrimSpace(asString(body["slug"]))
		if slug != "" && !slugPattern.MatchString(slug) {
			errs["slug"] = []string{"The slug format is invalid."}
		} else if slug != "" && slugTaken(db, slug, post.ID) {
			errs["slug"] = []string{"The slug has already been taken."}
		} else if slug != "" {
			post.Slug = slug
		}
	}
	if _, has := body["content"]; has {
		content := asString(body["content"])
		if strings.TrimSpace(content) == "" {
			errs["content"] = []string{"The content field is required."}
		} else {
			html, err := classes.FormatHTML(content)
			if err != nil {
				errs["content"] = []string{err.Error()}
			} else {
				post.Content = content
				post.ContentHTML = html
			}
		}
	}
	if _, has := body["excerpt"]; has {
		post.Excerpt = strings.TrimSpace(asString(body["excerpt"]))
	}
	if _, has := body["published"]; has {
		post.Published = asBool(body["published"])
	}
	if _, has := body["is_pinned"]; has {
		post.IsPinned = asBool(body["is_pinned"])
	}
	if _, has := body["published_at"]; has {
		ts, err := parsePublishedAt(body["published_at"])
		if err != nil {
			errs["published_at"] = []string{"The published at is not a valid date."}
		} else {
			post.PublishedAt = ts
		}
	}
	if _, has := body["metadata"]; has {
		post.Metadata = jsonPtr(body["metadata"])
	}
	if _, has := body["sources"]; has {
		post.Sources = jsonPtr(body["sources"])
	}
	if catErr := validateCategoryIDs(db, body["categories"]); catErr != nil {
		errs["categories"] = []string{catErr.Error()}
	}
	if transErr := validateTranslations(body["translations"]); transErr != nil {
		errs["translations"] = []string{transErr.Error()}
	}
	if len(errs) > 0 {
		return errs
	}
	_ = r
	return nil
}

func slugTaken(db *gorm.DB, slug string, exceptID uint) bool {
	q := db.Model(&models.Post{}).Where("slug = ?", slug)
	if exceptID > 0 {
		q = q.Where("id <> ?", exceptID)
	}
	var n int64
	_ = q.Count(&n).Error
	return n > 0
}

func validateCategoryIDs(db *gorm.DB, raw any) error {
	if raw == nil {
		return nil
	}
	ids, ok := asUintSlice(raw)
	if !ok {
		return fmt.Errorf("The categories must be an array.")
	}
	for _, id := range ids {
		var n int64
		if err := db.Model(&models.Category{}).Where("id = ?", id).Count(&n).Error; err != nil || n == 0 {
			return fmt.Errorf("The selected categories is invalid.")
		}
	}
	return nil
}

func validateTranslations(raw any) error {
	if raw == nil {
		return nil
	}
	m, ok := raw.(map[string]any)
	if !ok {
		return fmt.Errorf("The translations must be an array.")
	}
	for _, v := range m {
		attrs, ok := v.(map[string]any)
		if !ok {
			continue
		}
		if slug := strings.TrimSpace(asString(attrs["slug"])); slug != "" && !slugPattern.MatchString(slug) {
			return fmt.Errorf("The translations slug format is invalid.")
		}
		if title := asString(attrs["title"]); utf8.RuneCountInString(title) > 255 {
			return fmt.Errorf("The translations title may not be greater than 255 characters.")
		}
	}
	return nil
}

func asUintSlice(raw any) ([]uint, bool) {
	switch t := raw.(type) {
	case []any:
		out := make([]uint, 0, len(t))
		for _, item := range t {
			id, ok := asUint(item)
			if !ok {
				return nil, false
			}
			out = append(out, id)
		}
		return out, true
	default:
		return nil, false
	}
}

func applyPostAssocs(ctx context.Context, db *gorm.DB, post *models.Post, body map[string]any) error {
	if _, has := body["categories"]; has {
		ids, _ := asUintSlice(body["categories"])
		if err := db.Where("post_id = ?", post.ID).Delete(&models.PostCategory{}).Error; err != nil {
			return err
		}
		for _, id := range ids {
			if err := db.Create(&models.PostCategory{PostID: post.ID, CategoryID: id}).Error; err != nil {
				return err
			}
		}
	}
	if _, has := body["tags"]; has {
		ids, err := resolveTagIDs(db, body["tags"])
		if err != nil {
			return err
		}
		if err := db.Where("post_id = ?", post.ID).Delete(&models.PostTag{}).Error; err != nil {
			return err
		}
		for _, id := range ids {
			if err := db.Create(&models.PostTag{PostID: post.ID, TagID: id}).Error; err != nil {
				return err
			}
		}
	}
	if raw, has := body["translations"]; has {
		if err := syncTranslations(ctx, db, post, raw); err != nil {
			return err
		}
	}
	return nil
}

func resolveTagIDs(db *gorm.DB, raw any) ([]uint, error) {
	items, ok := raw.([]any)
	if !ok {
		if raw == nil {
			return nil, nil
		}
		return nil, fmt.Errorf("tags must be an array")
	}
	var ids []uint
	for _, item := range items {
		if id, ok := asUint(item); ok {
			var n int64
			if err := db.Model(&models.Tag{}).Where("id = ?", id).Count(&n).Error; err != nil {
				return nil, err
			}
			if n > 0 {
				ids = append(ids, id)
			}
			continue
		}
		name := strings.TrimSpace(asString(item))
		if name == "" {
			continue
		}
		slug := slugify(name)
		var tag models.Tag
		err := db.Where("name = ? OR slug = ?", name, slug).Take(&tag).Error
		if err == nil {
			ids = append(ids, tag.ID)
			continue
		}
		if slug == "" {
			slug = "tag"
		}
		tag = models.Tag{Name: name, Slug: slug}
		if err := db.Create(&tag).Error; err != nil {
			return nil, err
		}
		ids = append(ids, tag.ID)
	}
	return ids, nil
}

func syncTranslations(ctx context.Context, db *gorm.DB, post *models.Post, raw any) error {
	m, ok := raw.(map[string]any)
	if !ok {
		return nil
	}
	fields := []string{"title", "slug", "content", "content_html", "excerpt", "metadata"}
	for locale, v := range m {
		attrs, ok := v.(map[string]any)
		if !ok {
			continue
		}
		if content := asString(attrs["content"]); strings.TrimSpace(content) != "" && strings.TrimSpace(asString(attrs["content_html"])) == "" {
			html, err := classes.FormatHTML(content)
			if err != nil {
				return err
			}
			attrs["content_html"] = html
		}
		for _, field := range fields {
			if val, has := attrs[field]; has && val != nil {
				if err := translate.SetTranslated(ctx, db, post, field, locale, val); err != nil {
					return err
				}
			}
		}
	}
	return nil
}