package web

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

	"github.com/yourusername/caldav-server/internal/db"
	"github.com/yourusername/caldav-server/internal/web/templates"
)

// resourceNameRe restricts calendar/address book names to characters that
// are safe as both a URL path segment and a filesystem directory name.
var resourceNameRe = regexp.MustCompile(`^[a-zA-Z0-9_-]{1,64}$`)

// hexColorRe validates the 6-digit hex color format produced by an HTML
// <input type="color">, e.g. "#3b82f6".
var hexColorRe = regexp.MustCompile(`^#[0-9a-fA-F]{6}$`)

// handleCalendarResource handles POST (create) and DELETE (remove) for
// the current user's own calendars, mounted at /resources/calendar.
func (s *Server) handleCalendarResource(w http.ResponseWriter, r *http.Request) {
	s.handleResource(w, r, "calendar")
}

func (s *Server) handleAddressBookResource(w http.ResponseWriter, r *http.Request) {
	s.handleResource(w, r, "addressbook")
}

// handleCalendarColor updates the color of one of the current user's own
// calendars, mounted at /resources/calendar/color. It re-renders just
// that calendar's card (not the whole list), since the set of cards
// doesn't change.
func (s *Server) handleCalendarColor(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.SetCalendarColor(username, name, color); err != nil && err != db.ErrResourceNotFound {
		s.logger.Error("setting calendar color", "error", err)
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}

	card, err := s.resourceCardFor(username, "calendar", name)
	if err != nil {
		s.logger.Error("rendering resource card", "error", err)
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	_ = templates.ResourceCardView(card).Render(r.Context(), w)
}

// handleBirthdayColor updates the current user's display color for the
// synthetic "Birthdays" calendar, mounted at /resources/birthdays/color.
// It re-renders just that card (not the whole list), since the set of
// cards doesn't change.
func (s *Server) handleBirthdayColor(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
	}
	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.SetBirthdayCalendarColor(username, color); err != nil {
		s.logger.Error("setting birthday calendar color", "error", err)
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}

	card := templates.ResourceCard{Kind: "calendar", Name: "Birthdays", Color: s.birthdayCalendarColor(username), Virtual: true}
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	_ = templates.ResourceCardView(card).Render(r.Context(), w)
}

func (s *Server) handleResource(w http.ResponseWriter, r *http.Request, kind string) {
	username := userFromContext(r.Context())

	// htmx v2 sends DELETE request parameters as URL query parameters, not
	// a request body — unlike POST/PUT/PATCH (see internal/web/shares.go).
	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
	}

	collPrefix := "col/calendars/"
	if kind == "addressbook" {
		collPrefix = "col/addressbooks/"
	}

	switch r.Method {
	case http.MethodPost:
		var err error
		if kind == "calendar" {
			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
			}
			err = s.dbase.CreateCalendarWithColor(username, name, color)
		} else {
			err = s.dbase.CreateAddressBook(username, name)
		}
		if 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 resource", "kind", kind, "error", err)
			http.Error(w, "internal error", http.StatusInternalServerError)
			return
		}
		if err := s.store.EnsureCollection(username, collPrefix+name); err != nil {
			s.logger.Error("creating resource storage", "kind", kind, "error", err)
			http.Error(w, "internal error", http.StatusInternalServerError)
			return
		}
	case http.MethodDelete:
		var err error
		if kind == "calendar" {
			err = s.dbase.DeleteCalendar(username, name)
		} else {
			err = s.dbase.DeleteAddressBook(username, name)
		}
		if err != nil && err != db.ErrResourceNotFound {
			s.logger.Error("deleting resource", "kind", kind, "error", err)
			http.Error(w, "internal error", http.StatusInternalServerError)
			return
		}
		if err := s.store.DeleteCollection(username, collPrefix+name); err != nil {
			s.logger.Warn("deleting resource storage", "kind", kind, "error", err)
		}
	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)
}