import { useMemo, useRef, useState, useEffect } from "react";
import { useLocation } from "wouter";
import { ChevronLeft, ChevronRight, Download, MoreVertical, Pencil, Plus, Share2, Trash2, Eye, EyeOff, Star, Upload, UserMinus, X, AlertTriangle } from "lucide-react";
import { useCalendar } from "@/store/calendar";
import { dateTimeKey, useSettings } from "@/store/settings";
import { addMonths, isSameDay, isToday, monthGrid, startOfDay, toLocalDateOnly } from "@/lib/dates";
import { BIRTHDAY_CALENDAR_ID } from "@/lib/birthdays";
import { subscriptionCalendarId } from "@/store/calendar";
import { useContacts } from "@/store/contacts";
import { formatMonthYear } from "@/lib/format";
import { formatWeekday } from "@/lib/datetime";
import { MenuItem, MenuSep, Popover, useMenu } from "@/ui/popover";
import { confirmDialog } from "@/ui/dialog";
import { toast } from "@/ui/toast";
import type { Calendar, Id } from "@/jmap/types";
import { CalendarDialog } from "./CalendarDialog";
import { ShareDialog } from "../settings/ShareDialog";
import { plural, t } from "@/lib/i18n";

export function CalendarSidebar() {
  const [location, navigate] = useLocation();
  const cal = useCalendar();
  const weekStart = useSettings((s) => s.settings.weekStart);
  const locale = useSettings((s) => dateTimeKey(s.settings));
  const parts = location.split("/");
  const view = parts[2] || "week";
  const dateStr = parts[3];
  const selected = useMemo(() => (dateStr ? new Date(`${dateStr}T00:00:00`) : new Date()), [dateStr]);
  const [anchor, setAnchor] = useState(() => startOfDay(selected));
  const grid = useMemo(() => monthGrid(anchor, weekStart), [anchor, weekStart]);
  const menu = useMenu();
  /*
   * The file picker for "Import iCAL file". A MenuItem is a button, so it
   * cannot wrap a hidden input the way the address-book import does; the input
   * lives at the end of the sidebar and the menu item reaches it through this.
   *
   * The calendar is remembered separately because opening the picker closes the
   * menu, and `menuCal` goes with it -- by the time a file comes back there
   * would be nothing left saying which calendar it was chosen for.
   */
  const fileRef = useRef<HTMLInputElement>(null);
  const importInto = useRef<Id | null>(null);

  /*
   * Handing the file over, which the browser only does from a click. The
   * revoke below is what keeps a calendar's worth of text from sitting in
   * memory after the download has started.
   */
  const exportFile = async (c: Calendar) => {
    try {
      const { text, count } = await cal.exportIcs(c.id);
      const url = URL.createObjectURL(new Blob([text], { type: "text/calendar" }));
      const a = document.createElement("a");
      a.href = url;
      a.download = `${c.name.replace(/[^\w.-]+/g, "_") || "calendar"}.ics`;
      a.click();
      URL.revokeObjectURL(url);
      toast.success(plural(count, { one: "Exported {n} event", other: "Exported {n} events" }));
    } catch (err) {
      toast.error(t("Could not export this calendar: {error}", { error: (err as Error).message }));
    }
  };

  const importFile = async (file: File) => {
    const calendarId = importInto.current;
    if (!calendarId) return;
    try {
      const { created, updated } = await cal.importIcs(await file.text(), calendarId);
      /*
       * The two counts are kept apart on purpose, the way the contacts import
       * keeps them. "Imported 40 events" over a file of 240 reads as a failure
       * when the other 200 were updated, and a re-import of a corrected export
       * -- the reason for doing this at all -- creates nothing and would
       * otherwise report importing nothing at all.
       */
      const imported = plural(created, { one: "Imported {n} event", other: "Imported {n} events" });
      const refreshed = plural(updated, { one: "{n} updated", other: "{n} updated" });
      if (!created) toast.success(plural(updated, { one: "Updated {n} event, nothing new", other: "Updated {n} events, nothing new" }));
      else if (updated) toast.success(`${imported} · ${refreshed}`);
      else toast.success(imported);
    } catch (err) {
      toast.error(t("Could not import this file: {error}", { error: (err as Error).message }));
    }
  };
  /* Added if the server says so or the reader's settings do; Stalwart will not
     always take the flag, so the settings carry it where it refuses. */
  const addedShares = new Set(useSettings((s) => s.settings).addedShares);
  const isAdded = (c: { accountId: string; calendar: { id: string; isSubscribed?: boolean } }) =>
    Boolean(c.calendar.isSubscribed) || addedShares.has(`${c.accountId}:${c.calendar.id}`);
  const sharedSubscribed = cal.sharedCalendars.filter(isAdded);
  const sharedAvailable = cal.sharedCalendars.filter((c) => !isAdded(c));
  const [menuCal, setMenuCal] = useState<Calendar | null>(null);
  const [editCal, setEditCal] = useState<Partial<Calendar> | null>(null);
  const [share, setShare] = useState<Calendar | null>(null);
  const instances = cal.instancesIn(grid[0]!, new Date(grid[41]!.getTime() + 86400000));
  const dow = useMemo(() => grid.slice(0, 7).map((d) => formatWeekday(d, "narrow")), [grid, locale]);

  if (!cal.available) return null;
  const birthdaysOn = useSettings((st) => st.settings.birthdayCalendar);
  const subscriptions = useSettings((st) => st.settings.icalSubscriptions);
  /*
   * Refreshed when the calendar is opened, and not on a timer. ihasmail has
   * nowhere to run a schedule -- no worker, no server-side state -- so the
   * honest guarantee is that a subscription is as current as the last time
   * somebody looked, which is also when it matters.
   */
  useEffect(() => {
    if (subscriptions.length) void useCalendar.getState().refreshSubscriptions();
  }, [subscriptions]);

  /*
   * The cards have to be loaded for there to be any birthdays to derive, and
   * the calendar is a view somebody can land on directly without ever opening
   * Contacts.
   */
  useEffect(() => {
    if (birthdaysOn && !useContacts.getState().loaded && !useContacts.getState().loading) void useContacts.getState().loadAll();
  }, [birthdaysOn]);

  const calendars = Object.values(cal.calendars).sort((a, b) => a.sortOrder - b.sortOrder || a.name.localeCompare(b.name));

  return (
    <div style={{ padding: "4px 8px" }}>
      <div className="mini-cal">
        <div className="mc-head">
          <button className="icon-btn xs" onClick={() => setAnchor(addMonths(anchor, -1))} aria-label={t("Previous month")}><ChevronLeft size={16} /></button>
          <span>{formatMonthYear(anchor)}</span>
          <button className="icon-btn xs" onClick={() => setAnchor(addMonths(anchor, 1))} aria-label={t("Next month")}><ChevronRight size={16} /></button>
        </div>
        <div className="mc-grid">
          {dow.map((d, i) => <div key={i} className="mc-dow">{d}</div>)}
          {grid.map((d) => (
            <div key={d.toISOString()} className={`mc-day ${d.getMonth() !== anchor.getMonth() ? "other" : ""} ${isToday(d) ? "today" : ""} ${isSameDay(d, selected) ? "selected" : ""} ${instances.some((i) => i.start < new Date(d.getTime() + 86400000) && i.end > d) ? "has-events" : ""}`} onClick={() => navigate(`/calendar/${view === "month" ? "day" : view}/${toLocalDateOnly(d)}`)}>
              {d.getDate()}
            </div>
          ))}
        </div>
      </div>
      <div className="nav-section" style={{ paddingLeft: 4 }}>
        <span>{t("My calendars")}</span>
        <button className="icon-btn" title={t("New calendar")} onClick={() => setEditCal({})}><Plus size={16} /></button>
      </div>
      {/* Derived, so no context menu and nothing to share or make default --
          it is a switch, and Settings is where it is turned off entirely. */}
      {birthdaysOn && (
        <div
          className={`cal-list-item ${cal.hidden[BIRTHDAY_CALENDAR_ID] ? "hidden-cal" : ""}`}
          onClick={() => cal.toggleHidden(BIRTHDAY_CALENDAR_ID)}
          title={t("From the birthdays on your contacts. Nothing is stored.")}
        >
          <span className="cal-color" style={{ background: "#e0a33e", borderColor: "#e0a33e" }} />
          <span className="cal-name">{t("Birthdays")}</span>
        </div>
      )}
      {subscriptions.map((sub) => {
        const id = subscriptionCalendarId(sub.id);
        const failed = cal.subscriptionErrors[sub.id];
        const count = cal.subscriptionEvents[sub.id]?.length ?? 0;
        return (
          <div
            key={id}
            className={`cal-list-item ${cal.hidden[id] ? "hidden-cal" : ""}`}
            onClick={() => cal.toggleHidden(id)}
            title={failed ? t("Could not read this calendar: {reason}", { reason: failed }) : t("Subscribed to {url}", { url: sub.url })}
          >
            <span className="cal-color" style={{ background: sub.color, borderColor: sub.color }} />
            <span className="cal-name">{sub.name}</span>
            {/* A subscription that cannot be read says so here rather than
                drawing an empty calendar, which looks like a calendar with
                nothing in it. */}
            {failed ? <AlertTriangle size={12} className="faint" aria-label={t("Could not be read")} /> : count === 0 ? null : null}
          </div>
        );
      })}
      {calendars.map((c) => (
        <div key={c.id} className={`cal-list-item ${cal.hidden[c.id] ? "hidden-cal" : ""}`} onClick={() => cal.toggleHidden(c.id)} onContextMenu={(e) => { e.preventDefault(); setMenuCal(c); menu.openAt(e.clientX, e.clientY); }}>
          <span className="cal-color" style={{ background: c.color ?? "var(--accent)", borderColor: c.color ?? "var(--accent)" }} />
          <span className="cal-name">{c.name}</span>
          {Object.keys(c.shareWith ?? {}).length > 0 && <Share2 size={12} className="faint" aria-label={t("Shared")} />}
          {c.isDefault && <Star size={12} className="faint" />}
          <button className="icon-btn xs nav-more" onClick={(e) => { e.stopPropagation(); setMenuCal(c); menu.open(e); }} aria-label={t("Calendar options")}><MoreVertical size={14} /></button>
        </div>
      ))}
      {/* Calendars other people shared, split by whether the reader has added
          them. Stalwart returns every calendar in a reachable account with full
          rights, so "shared with me" and "there is an account here at all" look
          identical -- `isSubscribed` is the only thing that tells them apart,
          and adding one is a deliberate act rather than a guess on our part. */}
      {sharedSubscribed.length > 0 && (
        <>
          <div className="nav-section"><span>{t("Shared with me")}</span></div>
          {sharedSubscribed.map(({ accountId, accountName, calendar: c }) => {
            const key = `${accountId}:${c.id}`;
            return (
              <div key={key} className={`cal-list-item ${cal.hidden[key] ? "hidden-cal" : ""}`} onClick={() => cal.toggleHidden(key)} title={t("{name} — shared by {owner}", { name: c.name, owner: accountName })}>
                <span className="cal-color" style={{ background: c.color ?? "var(--accent)", borderColor: c.color ?? "var(--accent)" }} />
                <span className="cal-name">{c.name}</span>
                <button
                  className="icon-btn xs nav-more"
                  title={t("Remove from my calendar")}
                  aria-label={t("Remove from my calendar")}
                  onClick={(e) => { e.stopPropagation(); void cal.setSharedSubscribed(accountId, c.id, false); }}
                >
                  <X size={14} />
                </button>
              </div>
            );
          })}
        </>
      )}
      {sharedAvailable.length > 0 && (
        <>
          <div className="nav-section"><span>{t("Available to add")}</span></div>
          {sharedAvailable.map(({ accountId, accountName, calendar: c }) => (
            <div key={`${accountId}:${c.id}`} className="cal-list-item" title={t("{name} — from {owner}", { name: c.name, owner: accountName })}>
              <span className="cal-color" style={{ background: "transparent", borderColor: c.color ?? "var(--border-strong)" }} />
              <span className="cal-name faint">{c.name}</span>
              <button
                className="icon-btn xs nav-more"
                title={t("Add to my calendar")}
                aria-label={t("Add to my calendar")}
                onClick={(e) => { e.stopPropagation(); void cal.setSharedSubscribed(accountId, c.id, true); }}
              >
                <Plus size={14} />
              </button>
            </div>
          ))}
        </>
      )}

      <Popover anchor={menu.anchor} onClose={menu.close} width={220}>
        {menuCal && (
          <>
            <MenuItem icon={cal.hidden[menuCal.id] ? <Eye size={16} /> : <EyeOff size={16} />} label={cal.hidden[menuCal.id] ? "Show" : "Hide"} onClick={() => cal.toggleHidden(menuCal.id)} />
            <MenuItem icon={<Pencil size={16} />} label={t("Edit")} onClick={() => setEditCal(menuCal)} />
            <MenuItem
              icon={<Upload size={16} />}
              label={t("Import iCAL file…")}
              disabled={!menuCal.myRights.mayWriteAll && !menuCal.myRights.mayWriteOwn}
              onClick={() => {
                importInto.current = menuCal.id;
                fileRef.current?.click();
              }}
            />
            {/* No rights test: exporting is reading, and a calendar you cannot
                read is not in this list to begin with. */}
            <MenuItem icon={<Download size={16} />} label={t("Export iCAL file")} onClick={() => void exportFile(menuCal)} />
            <MenuItem icon={<Share2 size={16} />} label={t("Share…")} onClick={() => setShare(menuCal)} disabled={!menuCal.myRights.mayShare} />
            {/* Revoking every share at once, without walking the dialog and
                removing people one at a time. Only offered when there is
                something to revoke. */}
            {Object.keys(menuCal.shareWith ?? {}).length > 0 && (
              <MenuItem
                icon={<UserMinus size={16} />}
                label={t("Stop sharing")}
                disabled={!menuCal.myRights.mayShare}
                onClick={async () => {
                  const who = Object.keys(menuCal.shareWith ?? {}).length;
                  if (!(await confirmDialog({
                    title: t("Stop sharing “{name}”?", { name: menuCal.name }),
                    message: plural(who, { one: "{n} person will lose access. Events in it are not affected.", other: "{n} people will lose access. Events in it are not affected." }),
                    confirmLabel: t("Stop sharing"),
                    danger: true,
                  }))) return;
                  try {
                    await cal.updateCalendar(menuCal.id, { shareWith: null });
                    toast.success(t("No longer shared"));
                  } catch (err) {
                    toast.error((err as Error).message);
                  }
                }}
              />
            )}
            <MenuItem icon={<Star size={16} />} label={t("Make default")} disabled={menuCal.isDefault} onClick={() => void cal.updateCalendar(menuCal.id, { isDefault: true } as Partial<Calendar>).catch((err) => toast.error((err as Error).message))} />
            <MenuSep />
            <MenuItem danger icon={<Trash2 size={16} />} label={t("Delete")} disabled={!menuCal.myRights.mayDelete} onClick={async () => { if (await confirmDialog({ title: t("Delete “{name}”?", { name: menuCal.name }), message: t("All events in this calendar will be deleted."), confirmLabel: t("Delete"), danger: true })) void cal.destroyCalendar(menuCal.id).catch((err) => toast.error((err as Error).message)); }} />
          </>
        )}
      </Popover>
      {/* Cleared after every pick, so choosing the same file twice still counts
          as a change and fires again. */}
      <input
        ref={fileRef}
        type="file"
        accept=".ics,.ical,text/calendar"
        hidden
        onChange={(e) => {
          const file = e.target.files?.[0];
          e.target.value = "";
          if (file) void importFile(file);
        }}
      />
      {editCal && <CalendarDialog calendar={editCal} onClose={() => setEditCal(null)} />}
      {share && <ShareDialog kind="Calendar" id={share.id} name={share.name} shareWith={share.shareWith} onClose={() => setShare(null)} />}
    </div>
  );
}