// Package api holds the menu plugin's public read API.
package api

import (
	"errors"
	"log/slog"
	"net/http"
	"regexp"

	"git.golem15.com/golem15/sm-menu-plugin/classes"
	"git.golem15.com/golem15/sm-menu-plugin/models"
	"git.golem15.com/golem15/summercms/modules/backpack"
	"git.golem15.com/golem15/summercms/modules/signpost"
	"git.golem15.com/golem15/summercms/modules/wire"
	"gorm.io/gorm"
)

// codePattern is the shape of a menu code the API serves: letters, digits,
// dashes and underscores. Anything else is the JSON 404, so every miss has
// the same body.
var codePattern = regexp.MustCompile(`^[A-Za-z0-9_-]+$`)

// Menu is the data object of GET /_menu/api/v1/menus/{code}.
type Menu struct {
	Code     string         `json:"code"`
	Name     string         `json:"name"`
	CSSClass *string        `json:"css_class"`
	Items    []classes.Item `json:"items"`
}

// Show is GET /_menu/api/v1/menus/{code}?locale=xx, anonymous. It serves the
// active menu with code and its published entries as a tree
// (classes.BuildTree), resolving registry entries through the framework's
// menu item type registry for the requested locale. An unknown or inactive
// menu is 404 {"error":"Menu not found"}.
func Show(app *backpack.App) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		code := r.PathValue("code")
		if !codePattern.MatchString(code) {
			writeError(w, http.StatusNotFound, "Menu not found")
			return
		}
		db, err := gdb(app)
		if err != nil {
			writeError(w, http.StatusInternalServerError, "Internal server error")
			return
		}
		db = db.WithContext(r.Context())
		var menus []models.Menu
		if err := db.Where("code = ? AND is_active = ?", code, true).Order("id ASC").Limit(1).Find(&menus).Error; err != nil {
			slog.Default().Error("menu api: load menu", "code", code, "error", err)
			writeError(w, http.StatusInternalServerError, "Internal server error")
			return
		}
		if len(menus) == 0 {
			writeError(w, http.StatusNotFound, "Menu not found")
			return
		}
		menu := menus[0]
		var entries []models.MenuEntry
		if err := db.Where("menu_id = ? AND is_published = ?", menu.ID, true).
			Order("sort_order ASC NULLS LAST, id ASC").Find(&entries).Error; err != nil {
			slog.Default().Error("menu api: load entries", "code", code, "error", err)
			writeError(w, http.StatusInternalServerError, "Internal server error")
			return
		}
		var registry classes.Resolver
		if reg, ok := app.Lookup[*signpost.Registry](); ok && reg != nil {
			registry = reg
		}
		items := classes.BuildTree(r.Context(), entries, classes.TreeOptions{
			Registry: registry,
			Locale:   r.URL.Query().Get("locale"),
		})
		var css *string
		if menu.CSSClass != nil && *menu.CSSClass != "" {
			css = menu.CSSClass
		}
		wire.WriteJSON(w, http.StatusOK, map[string]any{"data": Menu{
			Code:     menu.Code,
			Name:     menu.Name,
			CSSClass: css,
			Items:    items,
		}})
	}
}

func writeError(w http.ResponseWriter, status int, message string) {
	wire.WriteJSON(w, status, map[string]any{"error": message})
}

func gdb(app *backpack.App) (*gorm.DB, error) {
	if app == nil {
		return nil, errors.New("menu api: application is not configured")
	}
	db, ok := app.Lookup[*gorm.DB]()
	if !ok || db == nil {
		return nil, errors.New("menu api: database is not configured")
	}
	return db, nil
}