package web

import (
	"context"
	"net/http"
	"strings"

	"git.arnef.de/arnef/nidus/internal/db"
	"git.arnef.de/arnef/nidus/internal/web/templates"
)

// icsURLValid does a light sanity check on a subscription URL: it must be
// http(s):// (fetched directly) or webcal:// (rewritten to https:// by
// internal/icssub before fetching), and within a reasonable length.
func icsURLValid(u string) bool {
	if len(u) == 0 || len(u) > 2048 {
		return false
	}
	return strings.HasPrefix(u, "http://") || strings.HasPrefix(u, "https://") || strings.HasPrefix(u, "webcal://")
}

// handleICSResource handles POST (create) and DELETE (remove) for the
// current user's ICS/webcal calendar subscriptions, mounted at
// /resources/ics.
func (s *Server) handleICSResource(w http.ResponseWriter, r *http.Request) {
	username := userFromContext(r.Context())

	// htmx v2 sends DELETE request parameters as URL query parameters, not
	// a request body (see internal/web/resources.go's handleResource).
	if r.Method == http.MethodDelete {
		r.PostForm = r.URL.Query()
	} else if err := r.ParseForm(); err != nil {
		http.Error(w, "invalid form", http.StatusBadRequest)
		return
	}
	name := strings.TrimSpace(r.PostForm.Get("name"))
	if !resourceNameRe.MatchString(name) {
		http.Error(w, "name must be 1-64 letters, digits, '-' or '_'", http.StatusBadRequest)
		return
	}

	switch r.Method {
	case http.MethodPost:
		url := strings.TrimSpace(r.PostForm.Get("url"))
		if !icsURLValid(url) {
			http.Error(w, "url must be a http://, https:// or webcal:// address", http.StatusBadRequest)
			return
		}
		color := strings.TrimSpace(r.PostForm.Get("color"))
		if color != "" && !hexColorRe.MatchString(color) {
			http.Error(w, "color must be a hex value like #3b82f6", http.StatusBadRequest)
			return
		}
		if err := s.dbase.CreateICSSubscription(username, name, url, color); err != nil {
			if err == db.ErrResourceExists {
				http.Error(w, "already exists", http.StatusConflict)
				return
			}
			if err == db.ErrReservedName {
				http.Error(w, "this name is reserved for a computed calendar", http.StatusConflict)
				return
			}
			s.logger.Error("creating ics subscription", "error", err)
			http.Error(w, "internal error", http.StatusInternalServerError)
			return
		}
	case http.MethodDelete:
		if err := s.dbase.DeleteICSSubscription(username, name); err != nil && err != db.ErrResourceNotFound {
			s.logger.Error("deleting ics subscription", "error", err)
			http.Error(w, "internal error", http.StatusInternalServerError)
			return
		}
	default:
		w.Header().Set("Allow", "POST, DELETE")
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}

	// The set of cards changed (one added/removed), so re-render the
	// whole #resources list rather than a single card.
	resources, err := s.resourceCards(username)
	if err != nil {
		s.logger.Error("listing resources", "error", err)
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	_ = templates.ResourceList(resources).Render(context.Background(), w)
}

// handleICSColor updates the color of one of the current user's ICS
// subscriptions, mounted at /resources/ics/color. It re-renders just that
// card (not the whole list), since the set of cards doesn't change.
func (s *Server) handleICSColor(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		w.Header().Set("Allow", "POST")
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}
	username := userFromContext(r.Context())
	if err := r.ParseForm(); err != nil {
		http.Error(w, "invalid form", http.StatusBadRequest)
		return
	}
	name := strings.TrimSpace(r.PostForm.Get("name"))
	color := strings.TrimSpace(r.PostForm.Get("color"))
	if !resourceNameRe.MatchString(name) {
		http.Error(w, "name must be 1-64 letters, digits, '-' or '_'", http.StatusBadRequest)
		return
	}
	if color != "" && !hexColorRe.MatchString(color) {
		http.Error(w, "color must be a hex value like #3b82f6", http.StatusBadRequest)
		return
	}
	if err := s.dbase.SetICSSubscriptionColor(username, name, color); err != nil && err != db.ErrResourceNotFound {
		s.logger.Error("setting ics subscription color", "error", err)
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}

	sub, err := s.dbase.GetICSSubscription(username, name)
	if err != nil {
		s.logger.Error("loading ics subscription", "error", err)
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}
	card := templates.ResourceCard{Kind: "ics", Name: sub.Name, Color: sub.Color, URL: sub.URL}
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	_ = templates.ResourceCardView(card).Render(r.Context(), w)
}