package calendar

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

	"github.com/go-chi/chi/v5"

	"github.com/ultisuite/ulti-backend/internal/api/apiresponse"
	"github.com/ultisuite/ulti-backend/internal/api/apivalidate"
	"github.com/ultisuite/ulti-backend/internal/api/middleware"
	"github.com/ultisuite/ulti-backend/internal/api/query"
	meetpkg "github.com/ultisuite/ulti-backend/internal/meet"
	"github.com/ultisuite/ulti-backend/internal/nextcloud"
	"github.com/ultisuite/ulti-backend/internal/permission"
)

type Handler struct {
	svc    *Service
	logger *slog.Logger
}

func NewHandler(nc *nextcloud.Client, meetCfg *meetpkg.Config) *Handler {
	return &Handler{
		svc:    NewService(nc, meetCfg),
		logger: slog.Default().With("component", "calendar-api"),
	}
}

func (h *Handler) Routes() chi.Router {
	r := chi.NewRouter()
	read := middleware.RequirePermission(permission.ResourceCalendar, permission.LevelRead)
	write := middleware.RequirePermission(permission.ResourceCalendar, permission.LevelWrite)

	r.With(read).Get("/", h.ListCalendars)
	r.With(read).Get("/{calID}/events", h.ListEvents)
	r.With(read).Post("/freebusy", h.FreeBusy)
	r.With(write).Post("/{calID}/events", h.CreateEvent)
	r.With(write).Put("/events/*", h.UpdateEvent)
	r.With(write).Post("/events/response/*", h.RespondToInvitation)
	r.With(write).Post("/events/meet-link/*", h.CreateMeetLink)
	r.With(write).Delete("/events/*", h.DeleteEvent)
	return r
}

func (h *Handler) ListCalendars(w http.ResponseWriter, r *http.Request) {
	claims := middleware.ClaimsFromContext(r.Context())
	cals, err := h.svc.ListCalendars(r.Context(), claims.Sub)
	if err != nil {
		h.logger.Error("list calendars", "error", err)
		apivalidate.WriteInternal(w, r)
		return
	}
	apiresponse.WriteJSON(w, http.StatusOK, map[string]any{"calendars": cals})
}

func (h *Handler) ListEvents(w http.ResponseWriter, r *http.Request) {
	claims := middleware.ClaimsFromContext(r.Context())
	params, err := query.ParseListRequest(r)
	if err != nil {
		apivalidate.WriteQueryError(w, r, err)
		return
	}

	result, err := h.svc.ListEvents(r.Context(), claims.Sub, chi.URLParam(r, "calID"), params)
	if err != nil {
		h.logger.Error("list events", "error", err)
		apivalidate.WriteInternal(w, r)
		return
	}
	apiresponse.WriteJSON(w, http.StatusOK, result)
}

func (h *Handler) FreeBusy(w http.ResponseWriter, r *http.Request) {
	claims := middleware.ClaimsFromContext(r.Context())

	var req freeBusyRequest
	if err := apivalidate.DecodeJSON(w, r, maxRequestBody, &req); err != nil {
		return
	}
	ncReq, verr := validateFreeBusy(&req)
	if verr != nil {
		apivalidate.WriteValidationError(w, r, verr)
		return
	}

	result, err := h.svc.FreeBusy(r.Context(), claims.Sub, ncReq)
	if err != nil {
		h.logger.Error("free/busy", "error", err)
		apivalidate.WriteInternal(w, r)
		return
	}
	apiresponse.WriteJSON(w, http.StatusOK, result)
}

func (h *Handler) CreateEvent(w http.ResponseWriter, r *http.Request) {
	claims := middleware.ClaimsFromContext(r.Context())

	var event nextcloud.Event
	if err := apivalidate.DecodeJSON(w, r, maxRequestBody, &event); err != nil {
		return
	}
	if verr := validateCreateEvent(&event); verr != nil {
		apivalidate.WriteValidationError(w, r, verr)
		return
	}

	if err := h.svc.CreateEvent(r.Context(), claims.Sub, chi.URLParam(r, "calID"), &event); err != nil {
		h.logger.Error("create event", "error", err)
		apivalidate.WriteInternal(w, r)
		return
	}
	w.WriteHeader(http.StatusCreated)
}

func (h *Handler) UpdateEvent(w http.ResponseWriter, r *http.Request) {
	claims := middleware.ClaimsFromContext(r.Context())
	eventPath := strings.TrimSuffix(chi.URLParam(r, "*"), "/")
	if verr := validateDeletePath(eventPath); verr != nil {
		apivalidate.WriteValidationError(w, r, verr)
		return
	}
	ifMatch := strings.TrimSpace(r.Header.Get("If-Match"))
	if ifMatch == "" {
		apivalidate.WriteValidationError(w, r, apivalidate.NewValidationError(apivalidate.FieldDetail{
			Field: "If-Match", Message: "required",
		}))
		return
	}

	var event nextcloud.Event
	if err := apivalidate.DecodeJSON(w, r, maxRequestBody, &event); err != nil {
		return
	}
	if verr := validateCreateEvent(&event); verr != nil {
		apivalidate.WriteValidationError(w, r, verr)
		return
	}

	etag, err := h.svc.UpdateEvent(r.Context(), claims.Sub, eventPath, ifMatch, &event)
	if err != nil {
		if errors.Is(err, nextcloud.ErrETagMismatch) {
			apiresponse.WriteError(w, r, http.StatusPreconditionFailed, "etag_mismatch", "etag does not match current resource version", nil)
			return
		}
		h.logger.Error("update event", "error", err)
		apivalidate.WriteInternal(w, r)
		return
	}
	apiresponse.WriteJSON(w, http.StatusOK, map[string]any{"etag": etag})
}

func (h *Handler) RespondToInvitation(w http.ResponseWriter, r *http.Request) {
	claims := middleware.ClaimsFromContext(r.Context())
	eventPath := strings.TrimSuffix(chi.URLParam(r, "*"), "/")
	if verr := validateDeletePath(eventPath); verr != nil {
		apivalidate.WriteValidationError(w, r, verr)
		return
	}
	var req respondInvitationRequest
	if err := apivalidate.DecodeJSON(w, r, maxRequestBody, &req); err != nil {
		return
	}
	if strings.TrimSpace(req.Email) == "" {
		req.Email = claims.Email
	}
	normalized, verr := validateRespondInvitation(&req)
	if verr != nil {
		apivalidate.WriteValidationError(w, r, verr)
		return
	}
	etag, err := h.svc.RespondToInvitation(r.Context(), claims.Sub, eventPath, normalized.Email, normalized.Response, normalized.IfMatch)
	if err != nil {
		switch {
		case errors.Is(err, nextcloud.ErrAttendeeNotFound):
			apiresponse.WriteError(w, r, http.StatusNotFound, "attendee_not_found", "attendee not found in event", nil)
		case errors.Is(err, nextcloud.ErrETagMismatch):
			apiresponse.WriteError(w, r, http.StatusPreconditionFailed, "etag_mismatch", "etag does not match current resource version", nil)
		default:
			h.logger.Error("respond invitation", "error", err)
			apivalidate.WriteInternal(w, r)
		}
		return
	}
	apiresponse.WriteJSON(w, http.StatusOK, map[string]any{"etag": etag})
}

func (h *Handler) CreateMeetLink(w http.ResponseWriter, r *http.Request) {
	claims := middleware.ClaimsFromContext(r.Context())
	eventPath := strings.TrimSuffix(chi.URLParam(r, "*"), "/")
	if verr := validateDeletePath(eventPath); verr != nil {
		apivalidate.WriteValidationError(w, r, verr)
		return
	}
	var req createMeetLinkRequest
	if r.ContentLength > 0 {
		if err := apivalidate.DecodeJSON(w, r, maxRequestBody, &req); err != nil {
			return
		}
	}
	if verr := validateCreateMeetLink(&req); verr != nil {
		apivalidate.WriteValidationError(w, r, verr)
		return
	}
	meetURL, etag, err := h.svc.CreateMeetLink(r.Context(), claims.Sub, claims.Name, claims.Email, eventPath, req.IfMatch)
	if err != nil {
		if errors.Is(err, ErrMeetDisabled) {
			apiresponse.WriteError(w, r, http.StatusConflict, "meet_disabled", "meet integration is disabled", nil)
			return
		}
		if errors.Is(err, nextcloud.ErrETagMismatch) {
			apiresponse.WriteError(w, r, http.StatusPreconditionFailed, "etag_mismatch", "etag does not match current resource version", nil)
			return
		}
		h.logger.Error("create meet link", "error", err)
		apivalidate.WriteInternal(w, r)
		return
	}
	apiresponse.WriteJSON(w, http.StatusOK, map[string]any{
		"meet_url": meetURL,
		"etag":     etag,
	})
}

func (h *Handler) DeleteEvent(w http.ResponseWriter, r *http.Request) {
	claims := middleware.ClaimsFromContext(r.Context())
	eventPath := chi.URLParam(r, "*")
	if verr := validateDeletePath(eventPath); verr != nil {
		apivalidate.WriteValidationError(w, r, verr)
		return
	}
	if err := h.svc.DeleteEvent(r.Context(), claims.Sub, eventPath); err != nil {
		h.logger.Error("delete event", "error", err)
		apivalidate.WriteInternal(w, r)
		return
	}
	w.WriteHeader(http.StatusNoContent)
}