package api

import (
	"encoding/json"
	"errors"
	"net/http"
	"regexp"
	"strconv"
	"time"

	"github.com/google/uuid"

	"github.com/alchemistkay/guestguard/internal/domain"
	"github.com/alchemistkay/guestguard/internal/storage"
)

type eventHandler struct {
	repo     *storage.EventRepo
	collabs  *storage.CollaboratorRepo
	enforcer *tierEnforcer
}

type createEventRequest struct {
	Name        string         `json:"name"`
	Slug        string         `json:"slug"`
	EventDate   time.Time      `json:"event_date"`
	Venue       string         `json:"venue"`
	MaxCapacity int            `json:"max_capacity"`
	Settings    map[string]any `json:"settings"`
	Status      string         `json:"status"`
}

var slugRe = regexp.MustCompile(`^[a-z0-9]+(-[a-z0-9]+)*$`)

func (h *eventHandler) create(w http.ResponseWriter, r *http.Request) {
	hostID, ok := hostFromContext(w, r)
	if !ok {
		return
	}
	if !h.enforcer.allowEventCreate(w, r, hostID) {
		return
	}

	var req createEventRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "invalid json")
		return
	}

	if req.Name == "" {
		writeError(w, http.StatusBadRequest, "name is required")
		return
	}
	if !slugRe.MatchString(req.Slug) {
		writeError(w, http.StatusBadRequest, "slug must be lowercase alphanumeric with hyphens")
		return
	}
	if req.EventDate.IsZero() {
		writeError(w, http.StatusBadRequest, "event_date is required")
		return
	}

	status := domain.EventStatus(req.Status)
	if status == "" {
		status = domain.EventStatusDraft
	}
	if !status.Valid() {
		writeError(w, http.StatusBadRequest, "invalid status")
		return
	}

	ev, err := h.repo.Create(r.Context(), storage.CreateEventParams{
		HostID:      hostID,
		Name:        req.Name,
		Slug:        req.Slug,
		EventDate:   req.EventDate,
		Venue:       req.Venue,
		MaxCapacity: req.MaxCapacity,
		Settings:    req.Settings,
		Status:      status,
	})
	if err != nil {
		if errors.Is(err, domain.ErrSlugTaken) {
			writeError(w, http.StatusConflict, "slug already in use")
			return
		}
		writeError(w, http.StatusInternalServerError, "failed to create event")
		return
	}

	writeJSON(w, http.StatusCreated, ev)
}

// eventView wraps an Event with the caller's role so the dashboard UI can
// branch (e.g. hide the "Delete event" button for editors/viewers).
type eventView struct {
	*domain.Event
	YourRole domain.Role `json:"your_role"`
}

func (h *eventHandler) get(w http.ResponseWriter, r *http.Request) {
	hostID, ok := hostFromContext(w, r)
	if !ok {
		return
	}
	id, ok := parseIDParam(w, r, "id")
	if !ok {
		return
	}
	ev, role, ok := requireRole(w, r, h.repo, h.collabs, id, hostID, domain.RoleViewer)
	if !ok {
		return
	}
	writeJSON(w, http.StatusOK, eventView{Event: ev, YourRole: role})
}

func (h *eventHandler) list(w http.ResponseWriter, r *http.Request) {
	hostID, ok := hostFromContext(w, r)
	if !ok {
		return
	}

	q := r.URL.Query()
	limit := atoiOr(q.Get("limit"), 50)
	offset := atoiOr(q.Get("offset"), 0)

	// Block C: the dashboard shows every event the user has any role on,
	// not just events they own. The collaborators repo gives us the id set;
	// the events repo paginates the merged list.
	collabIDs, err := h.collabs.ListEventIDsForUser(r.Context(), hostID)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "failed to resolve memberships")
		return
	}
	events, err := h.repo.ListForUser(r.Context(), hostID, collabIDs, limit, offset)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "failed to list events")
		return
	}
	if events == nil {
		events = []*domain.Event{}
	}
	writeJSON(w, http.StatusOK, map[string]any{
		"events": events,
		"limit":  limit,
		"offset": offset,
	})
}

type updateEventRequest struct {
	Name        *string         `json:"name"`
	Slug        *string         `json:"slug"`
	EventDate   *time.Time      `json:"event_date"`
	Venue       *string         `json:"venue"`
	MaxCapacity *int            `json:"max_capacity"`
	Settings    *map[string]any `json:"settings"`
	Status      *string         `json:"status"`
}

func (h *eventHandler) update(w http.ResponseWriter, r *http.Request) {
	hostID, ok := hostFromContext(w, r)
	if !ok {
		return
	}
	id, ok := parseIDParam(w, r, "id")
	if !ok {
		return
	}
	// Block C: editor+ can patch event metadata. The plan reserves DELETE
	// (and the existing host_id row) for owners only.
	if _, _, ok := requireRole(w, r, h.repo, h.collabs, id, hostID, domain.RoleEditor); !ok {
		return
	}

	var req updateEventRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "invalid json")
		return
	}

	params := storage.UpdateEventParams{
		Name:        req.Name,
		EventDate:   req.EventDate,
		Venue:       req.Venue,
		MaxCapacity: req.MaxCapacity,
		Settings:    req.Settings,
	}
	if req.Slug != nil {
		if !slugRe.MatchString(*req.Slug) {
			writeError(w, http.StatusBadRequest, "slug must be lowercase alphanumeric with hyphens")
			return
		}
		params.Slug = req.Slug
	}
	if req.Status != nil {
		s := domain.EventStatus(*req.Status)
		if !s.Valid() {
			writeError(w, http.StatusBadRequest, "invalid status")
			return
		}
		params.Status = &s
	}

	ev, err := h.repo.UpdateByID(r.Context(), id, params)
	if err != nil {
		switch {
		case errors.Is(err, domain.ErrEventNotFound):
			writeError(w, http.StatusNotFound, "event not found")
		case errors.Is(err, domain.ErrSlugTaken):
			writeError(w, http.StatusConflict, "slug already in use")
		default:
			writeError(w, http.StatusInternalServerError, "failed to update event")
		}
		return
	}
	writeJSON(w, http.StatusOK, ev)
}

func (h *eventHandler) delete(w http.ResponseWriter, r *http.Request) {
	hostID, ok := hostFromContext(w, r)
	if !ok {
		return
	}
	id, ok := parseIDParam(w, r, "id")
	if !ok {
		return
	}
	// Block C: only owners can delete an event. Editors get 403; viewers
	// and non-members get 404.
	if _, _, ok := requireRole(w, r, h.repo, h.collabs, id, hostID, domain.RoleOwner); !ok {
		return
	}
	if err := h.repo.DeleteByID(r.Context(), id); err != nil {
		if errors.Is(err, domain.ErrEventNotFound) {
			writeError(w, http.StatusNotFound, "event not found")
			return
		}
		writeError(w, http.StatusInternalServerError, "failed to delete event")
		return
	}
	w.WriteHeader(http.StatusNoContent)
}

func parseIDParam(w http.ResponseWriter, r *http.Request, name string) (uuid.UUID, bool) {
	return parseRawUUID(w, name, r.PathValue(name))
}

func parseRawUUID(w http.ResponseWriter, name, raw string) (uuid.UUID, bool) {
	if raw == "" {
		writeError(w, http.StatusBadRequest, name+" is required")
		return uuid.Nil, false
	}
	id, err := uuid.Parse(raw)
	if err != nil {
		writeError(w, http.StatusBadRequest, name+" must be a valid uuid")
		return uuid.Nil, false
	}
	return id, true
}

func atoiOr(s string, fallback int) int {
	if s == "" {
		return fallback
	}
	if n, err := strconv.Atoi(s); err == nil {
		return n
	}
	return fallback
}