package store

import (
	"context"
)

// MenuItem is one entry of a blog's menu: either a page of the blog or a custom link.
type MenuItem struct {
	ID        int64
	PageID    *int64 // nil for custom links
	Label     string // custom links only; pages use their title
	URL       string // custom links only
	SortOrder int
	// joined from pages
	PageTitle string
	PageSlug  string
	IsHome    bool
}

// Text is what the visitor reads.
func (m MenuItem) Text() string {
	if m.PageID != nil {
		return m.PageTitle
	}
	return m.Label
}

// Href is where the entry points.
func (m MenuItem) Href() string {
	switch {
	case m.PageID == nil:
		return m.URL
	case m.IsHome:
		return "/"
	}
	return "/" + m.PageSlug
}

const menuCols = `m.id, m.page_id, m.label, m.url, m.sort_order, coalesce(p.title,''), coalesce(p.slug,''), coalesce(p.is_home,false)`

func (bs *BlogStore) ListMenu(ctx context.Context) ([]MenuItem, error) {
	rows, err := bs.db.Query(ctx, `SELECT `+menuCols+` FROM menu_items m LEFT JOIN pages p ON p.id=m.page_id
		ORDER BY m.sort_order, m.id`)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var out []MenuItem
	for rows.Next() {
		var m MenuItem
		if err := rows.Scan(&m.ID, &m.PageID, &m.Label, &m.URL, &m.SortOrder, &m.PageTitle, &m.PageSlug, &m.IsHome); err != nil {
			return nil, err
		}
		out = append(out, m)
	}
	return out, rows.Err()
}

// AddMenuPage appends a page to the menu; a page already in the menu is left where it is.
func (bs *BlogStore) AddMenuPage(ctx context.Context, pageID int64) error {
	return addMenuPage(ctx, bs.db, pageID)
}

func addMenuPage(ctx context.Context, db querier, pageID int64) error {
	_, err := db.Exec(ctx, `INSERT INTO menu_items (page_id, sort_order)
		SELECT id, (SELECT coalesce(max(sort_order),-1)+1 FROM menu_items)
		FROM pages WHERE id=$1 ON CONFLICT (page_id) WHERE page_id IS NOT NULL DO NOTHING`, pageID)
	return err
}

// SetPageInMenu adds or removes a page's menu entry.
func (bs *BlogStore) SetPageInMenu(ctx context.Context, pageID int64, on bool) error {
	if on {
		return bs.AddMenuPage(ctx, pageID)
	}
	_, err := bs.db.Exec(ctx, `DELETE FROM menu_items WHERE page_id=$1`, pageID)
	return err
}