package classes

import (
	"context"
	"strconv"
	"strings"

	"git.golem15.com/golem15/summercms/modules/pact"
	xhtml "golang.org/x/net/html"
	"gorm.io/gorm"
)

// The MCP tools a Journal content descriptor names (pact.ContentDescriptor
// Tools, D-96): Journal fixes its own content.
const (
	toolUpdatePost  = "journal_update_post"
	toolFixHeadings = "journal_fix_headings"
	toolSetImageAlt = "journal_set_image_alt"
)

// contentFacts is what one locale's body says about itself: its images
// (src, alt, decorative, size attributes), its YouTube embeds and its
// heading outline, each in document order.
type contentFacts struct {
	images   []pact.ContentImage
	videos   []pact.ContentVideo
	headings []pact.ContentHeading
}

// parseContentFacts reads html once with the x/net/html tokenizer. An img
// without src is skipped; an img whose alt attribute is present and empty
// is decorative. A figure with data-embed="youtube" and a data-id is a
// video (the Blog Editor's embed placeholder). A heading's text is its
// text content with white space collapsed; a heading inside a heading is
// read as part of the outer one.
func parseContentFacts(html string) contentFacts {
	var out contentFacts
	if strings.TrimSpace(html) == "" {
		return out
	}
	z := xhtml.NewTokenizer(strings.NewReader(html))
	level := 0
	var text strings.Builder
	for {
		tt := z.Next()
		if tt == xhtml.ErrorToken {
			break
		}
		switch tt {
		case xhtml.TextToken:
			if level > 0 {
				text.WriteString(z.Token().Data)
			}
		case xhtml.StartTagToken, xhtml.SelfClosingTagToken:
			tok := z.Token()
			switch tok.Data {
			case "img":
				if img, ok := contentImage(tok); ok {
					out.images = append(out.images, img)
				}
			case "figure":
				if attr(tok, "data-embed") == "youtube" {
					if id := attr(tok, "data-id"); id != "" {
						out.videos = append(out.videos, pact.ContentVideo{Provider: "youtube", ID: id})
					}
				}
			case "h1", "h2", "h3", "h4", "h5", "h6":
				if level == 0 && tt == xhtml.StartTagToken {
					level = int(tok.Data[1] - '0')
					text.Reset()
				}
			}
			if level > 0 && tt == xhtml.StartTagToken && !inlineListTags[tok.Data] && !isHeading(tok.Data) {
				text.WriteByte(' ')
			}
		case xhtml.EndTagToken:
			tok := z.Token()
			if level > 0 && tok.Data == "h"+strconv.Itoa(level) {
				out.headings = append(out.headings, pact.ContentHeading{
					Level: level,
					Text:  strings.Join(strings.Fields(text.String()), " "),
				})
				level = 0
			}
		}
	}
	return out
}

func isHeading(name string) bool {
	return len(name) == 2 && name[0] == 'h' && name[1] >= '1' && name[1] <= '6'
}

func contentImage(tok xhtml.Token) (pact.ContentImage, bool) {
	src := strings.TrimSpace(attr(tok, "src"))
	if src == "" {
		return pact.ContentImage{}, false
	}
	img := pact.ContentImage{URL: src}
	if alt, has := attrOK(tok, "alt"); has {
		img.Alt = strings.TrimSpace(alt)
		img.Decorative = img.Alt == ""
	}
	img.Width, _ = strconv.Atoi(strings.TrimSpace(attr(tok, "width")))
	img.Height, _ = strconv.Atoi(strings.TrimSpace(attr(tok, "height")))
	if img.Width < 0 {
		img.Width = 0
	}
	if img.Height < 0 {
		img.Height = 0
	}
	return img, true
}

func attr(tok xhtml.Token, key string) string {
	v, _ := attrOK(tok, key)
	return v
}

func attrOK(tok xhtml.Token, key string) (string, bool) {
	for _, a := range tok.Attr {
		if a.Namespace == "" && a.Key == key {
			return a.Val, true
		}
	}
	return "", false
}

// topHeading is a record's TopHeading: 2 while the H1 setting is on (the
// page title is the H1), 0 (any level) while it is off.
func topHeading(h1ToH2 bool) int {
	if h1ToH2 {
		return 2
	}
	return 0
}

// postCategoryRefs maps each post id to its categories as journal-category
// references, by category name, ties by id (the order :category takes its
// first category in).
func postCategoryRefs(ctx context.Context, db *gorm.DB, ids []uint) (map[uint][]pact.ContentRef, error) {
	out := map[uint][]pact.ContentRef{}
	if len(ids) == 0 {
		return out, nil
	}
	var rows []struct {
		PostID     uint `gorm:"column:post_id"`
		CategoryID uint `gorm:"column:category_id"`
	}
	err := db.WithContext(ctx).Table("golem15_journal_posts_categories AS pc").
		Select("pc.post_id, pc.category_id").
		Joins("JOIN golem15_journal_categories c ON c.id = pc.category_id").
		Where("pc.post_id IN ?", ids).
		Order("pc.post_id ASC, c.name ASC, c.id ASC").
		Scan(&rows).Error
	if err != nil {
		return nil, err
	}
	for _, r := range rows {
		out[r.PostID] = append(out[r.PostID], pact.ContentRef{Type: MenuTypeCategory, ID: strconv.FormatUint(uint64(r.CategoryID), 10)})
	}
	return out, nil
}

// authorRow is the part of a backend user a descriptor shows.
type authorRow struct {
	ID         uint   `gorm:"column:id"`
	FirstName  string `gorm:"column:first_name"`
	LastName   string `gorm:"column:last_name"`
	Login      string `gorm:"column:login"`
	AuthorSlug string `gorm:"column:author_slug"`
}

// authorColumns is the only projection descriptors read from backend_users:
// no contact, credential or permission column.
const authorColumns = "id, COALESCE(first_name, '') AS first_name, COALESCE(last_name, '') AS last_name, " +
	"login, COALESCE(golem15_bloghub_author_slug, '') AS author_slug"

// name is the author's display name: first and last name, else the login.
func (a authorRow) name() string {
	if n := strings.TrimSpace(strings.TrimSpace(a.FirstName) + " " + strings.TrimSpace(a.LastName)); n != "" {
		return n
	}
	return a.Login
}

// slug is the :author value: the author slug, else the login (the author
// API's own lookup order).
func (a authorRow) slug() string {
	if a.AuthorSlug != "" {
		return a.AuthorSlug
	}
	return a.Login
}

// loadAuthors reads the live backend users with the given ids.
func loadAuthors(ctx context.Context, db *gorm.DB, ids []uint) (map[uint]authorRow, error) {
	out := map[uint]authorRow{}
	if len(ids) == 0 {
		return out, nil
	}
	var rows []authorRow
	if err := db.WithContext(ctx).Table("backend_users").Select(authorColumns).
		Where("deleted_at IS NULL AND id IN ?", ids).Find(&rows).Error; err != nil {
		return nil, err
	}
	for _, r := range rows {
		out[r.ID] = r
	}
	return out, nil
}