package store

import (
	"context"
	"encoding/json"
)

// SaveDesign stores the design form in one go: the theme, the modules of every
// area and the menu, so a half-applied save is impossible. mods and menu are
// the complete new state in display order: rows with an ID are updated, rows
// without one inserted, and anything else is deleted.
func (bs *BlogStore) SaveDesign(ctx context.Context, theme json.RawMessage, mods []Module, menu []MenuItem) error {
	tx, err := bs.db.Begin(ctx)
	if err != nil {
		return err
	}
	defer tx.Rollback(ctx)
	if _, err := tx.Exec(ctx, `UPDATE settings SET theme=$1, updated_at=now()`, theme); err != nil {
		return err
	}

	keep := []int64{}
	for _, m := range mods {
		if m.ID != 0 {
			keep = append(keep, m.ID)
		}
	}
	if _, err := tx.Exec(ctx, `DELETE FROM modules WHERE id <> ALL($1)`, keep); err != nil {
		return err
	}
	order := map[string]int{} // sort_order restarts in every area
	for _, m := range mods {
		pos := order[m.Area]
		order[m.Area]++
		if m.ID != 0 { // area and kind never change
			_, err = tx.Exec(ctx, `UPDATE modules SET title=$2, body=$3, count=$4, sort_order=$5, updated_at=now() WHERE id=$1`, m.ID, m.Title, m.Body, m.Count, pos)
		} else {
			_, err = tx.Exec(ctx, `INSERT INTO modules (area, kind, title, body, count, sort_order) VALUES ($1,$2,$3,$4,$5,$6)`, m.Area, m.Kind, m.Title, m.Body, m.Count, pos)
		}
		if err != nil {
			return wrap(err)
		}
	}

	keep = keep[:0]
	for _, it := range menu {
		if it.ID != 0 {
			keep = append(keep, it.ID)
		}
	}
	if _, err := tx.Exec(ctx, `DELETE FROM menu_items WHERE id <> ALL($1)`, keep); err != nil {
		return err
	}
	for i, it := range menu {
		switch {
		case it.ID != 0:
			_, err = tx.Exec(ctx, `UPDATE menu_items SET label=$2, url=$3, sort_order=$4 WHERE id=$1`, it.ID, it.Label, it.URL, i)
		case it.PageID != nil: // a page deleted meanwhile simply adds nothing
			_, err = tx.Exec(ctx, `INSERT INTO menu_items (page_id, sort_order) SELECT id, $2 FROM pages WHERE id=$1
				ON CONFLICT (page_id) WHERE page_id IS NOT NULL DO UPDATE SET sort_order=excluded.sort_order`, *it.PageID, i)
		default:
			_, err = tx.Exec(ctx, `INSERT INTO menu_items (label, url, sort_order) VALUES ($1,$2,$3)`, it.Label, it.URL, i)
		}
		if err != nil {
			return wrap(err)
		}
	}
	return tx.Commit(ctx)
}