package api

import (
	"net/http"
	"regexp"
	"strconv"

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

// GroupPattern is the {group} constraint of the HTML sitemap group route:
// a file group slug.
const GroupPattern = `[a-z0-9][a-z0-9-]{0,63}`

// localePattern is the form a locale query value must have.
var localePattern = regexp.MustCompile(`^[a-z]{2,3}([-_][A-Za-z0-9]{2,8})*$`)

// pagePattern is the form of the page query value: 1 to 6 digits.
var pagePattern = regexp.MustCompile(`^[0-9]{1,6}$`)

// htmlRequest checks the shared parts of an HTML sitemap request and
// returns the settings and database, or answers 404 (the HTML sitemap is
// off, a malformed locale) or 500 itself.
func htmlRequest(app func() *backpack.App, w http.ResponseWriter, r *http.Request) (classes.HTMLSitemap, bool) {
	w.Header().Set("X-Robots-Tag", "noindex")
	w.Header().Set("Cache-Control", "no-cache, private")
	a := app()
	if a == nil {
		http.NotFound(w, r)
		return classes.HTMLSitemap{}, false
	}
	if loc := r.URL.Query().Get("locale"); loc != "" && !localePattern.MatchString(loc) {
		http.NotFound(w, r)
		return classes.HTMLSitemap{}, false
	}
	db, ok := a.Lookup[*gorm.DB]()
	if !ok || db == nil {
		http.Error(w, "Internal Server Error", http.StatusInternalServerError)
		return classes.HTMLSitemap{}, false
	}
	return classes.HTMLSitemap{App: a, DB: db.WithContext(r.Context())}, true
}

// HTMLOverview serves GET /_sitemap/api/v1/html?locale=: the HTML sitemap
// overview (D-34; classes.HTMLSitemap.Overview). It lists exactly the
// addresses of the XML sitemaps and answers 404 while the HTML sitemap is
// off. Every answer carries X-Robots-Tag: noindex.
func HTMLOverview(app func() *backpack.App) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		h, ok := htmlRequest(app, w, r)
		if !ok {
			return
		}
		settings, err := classes.LoadSettings(h.DB)
		if err != nil {
			http.Error(w, "Internal Server Error", http.StatusInternalServerError)
			return
		}
		if !settings.HTMLEnabled {
			http.NotFound(w, r)
			return
		}
		out, err := h.Overview(r.Context(), settings, r.URL.Query().Get("locale"))
		if err != nil {
			log.Error("golem15.sitemap: html overview", "error", err)
			http.Error(w, "Internal Server Error", http.StatusInternalServerError)
			return
		}
		wire.WriteJSON(w, http.StatusOK, out)
	}
}

// HTMLGroup serves GET /_sitemap/api/v1/html/{group}?locale=&page=: one
// page (from 1, the default) of a group (classes.HTMLSitemap.Group). An
// unknown group, a page past the last, a malformed page or the HTML
// sitemap off answer 404.
func HTMLGroup(app func() *backpack.App) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		h, ok := htmlRequest(app, w, r)
		if !ok {
			return
		}
		page := 1
		if raw := r.URL.Query().Get("page"); raw != "" {
			n, err := strconv.Atoi(raw)
			if !pagePattern.MatchString(raw) || err != nil || n < 1 {
				http.NotFound(w, r)
				return
			}
			page = n
		}
		settings, err := classes.LoadSettings(h.DB)
		if err != nil {
			http.Error(w, "Internal Server Error", http.StatusInternalServerError)
			return
		}
		if !settings.HTMLEnabled {
			http.NotFound(w, r)
			return
		}
		out, found, err := h.Group(r.Context(), settings, r.URL.Query().Get("locale"), r.PathValue("group"), page)
		if err != nil {
			log.Error("golem15.sitemap: html group", "error", err)
			http.Error(w, "Internal Server Error", http.StatusInternalServerError)
			return
		}
		if !found {
			http.NotFound(w, r)
			return
		}
		wire.WriteJSON(w, http.StatusOK, out)
	}
}