import { useCallback, useEffect, useMemo, useRef, useState } from "react";
import { useLocation, useSearch } from "wouter";
import { DEFAULT_SORT, useMail, type ListQuery } from "@/store/mail";
import { appliesTo, comparatorsFor } from "@/lib/listSort";
import type { Comparator } from "@/jmap/types";
import { useSettings } from "@/store/settings";
import { withBase } from "@/lib/basePath";
import { useCompose } from "@/store/compose";
import { buildFilter, describeFilter, parseQuery } from "@/lib/search";
import { keyboard } from "@/lib/keyboard";
import { useIsNarrow } from "@/ui/misc";
import { Splitter } from "@/ui/Splitter";
import { MessageList } from "./MessageList";
import { ThreadView } from "./ThreadView";
import { MailboxPicker } from "./MailboxPicker";
import { LabelPicker } from "./LabelPicker";
import type { Id } from "@/jmap/types";
import { confirmDialog } from "@/ui/dialog";
import { toast } from "@/ui/toast";
import { isUnknownMailbox } from "@/lib/mailboxRoute";
import { scheduledMailboxIdFrom, useScheduled } from "@/store/scheduled";
import { plural, t as translate, tNode } from "@/lib/i18n";
import { mailboxDisplayName } from "@/lib/mailboxName";

export function MailView({ mailboxId, threadId, search }: { mailboxId?: string; threadId?: string; search?: boolean }) {
  const [, navigate] = useLocation();
  const searchStr = useSearch();
  const mailboxes = useMail((s) => s.mailboxes);
  const mailboxesLoaded = useMail((s) => s.mailboxesLoaded);
  const inboxId = useMail((s) => s.roleId("inbox"));
  const query = useMail((s) => s.query);
  const list = useMail((s) => s.list);
  const settings = useSettings((s) => s.settings);
  const narrow = useIsNarrow();
  const [focusId, setFocusId] = useState<Id | null>(null);
  const [movePicker, setMovePicker] = useState<{ ids: Id[] } | null>(null);
  const [labelPicker, setLabelPicker] = useState<{ ids: Id[]; anchor: { x: number; y: number } } | null>(null);
  const reconcile = useScheduled((s) => s.reconcile);
  const scheduledId = useMail((s) => scheduledMailboxIdFrom(s.mailboxes));

  const q = useMemo(() => (search ? (new URLSearchParams(searchStr).get("q") ?? "") : ""), [search, searchStr]);

  // Redirect /mail → inbox
  useEffect(() => {
    if (!search && !mailboxId && inboxId) navigate(`/mail/${inboxId}`, { replace: true });
  }, [search, mailboxId, inboxId, navigate]);

  /*
   * A folder id this account does not have.
   *
   * It used to render the ordinary empty state -- "Nothing here. This folder is
   * empty." -- which is a claim about a folder that is not there, so a stale
   * link read as a folder that had emptied itself rather than one that was
   * gone (#111). Only reachable from outside the app: the sidebar links to ids
   * that exist.
   *
   * Inbox is the kinder landing than a dead end, but silently swapping one
   * folder for another would be its own small lie, so it says what happened.
   * `mailboxesLoaded` gates it: without that, every cold load redirects in the
   * moment before the folder list arrives.
   */
  useEffect(() => {
    if (!isUnknownMailbox({ mailboxId, mailboxes, loaded: mailboxesLoaded, search }) || !inboxId) return;
    toast.show(translate("That folder no longer exists. Showing your inbox instead."));
    navigate(`/mail/${inboxId}`, { replace: true });
  }, [search, mailboxId, mailboxesLoaded, mailboxes, inboxId, navigate]);

  /*
   * Search keeps newest-first whatever the setting says. A result list is
   * already ordered by the question that was asked, and putting unread at the
   * top of it answers a different one.
   */
  const sortForFolder = useCallback(
    (mailboxId: Id | null): Comparator[] => {
      const role = mailboxId ? useMail.getState().mailboxes[mailboxId]?.role : null;
      if (!appliesTo(settings.listSortScope, role)) return DEFAULT_SORT;
      return comparatorsFor(settings.listSortPreset, settings.listSortLevels);
    },
    [settings.listSortScope, settings.listSortPreset, settings.listSortLevels],
  );

  // Build & run the list query
  const listQuery = useMemo<ListQuery | null>(() => {
    if (search) {
      if (!q) return null;
      const parsed = parseQuery(q);
      const filter = buildFilter(parsed, mailboxes, null);
      const inMb = parsed.in ? (Object.values(mailboxes).find((m) => m.name.toLowerCase() === parsed.in!.toLowerCase())?.id ?? null) : null;
      return { key: "", filter, sort: DEFAULT_SORT, collapseThreads: settings.conversationMode, mailboxId: inMb, label: describeFilter(parsed) };
    }
    if (!mailboxId) return null;
    const mb = mailboxes[mailboxId];
    // Scheduled joins Drafts and Sent as a folder of individual messages: they
    // are outgoing, and collapsing them into their threads hides them.
    const isDraftsOrSent = mb?.role === "drafts" || mb?.role === "sent" || mailboxId === scheduledId;
    return { key: "", filter: { inMailbox: mailboxId }, sort: sortForFolder(mailboxId), collapseThreads: settings.conversationMode && !isDraftsOrSent, mailboxId };
  }, [search, q, mailboxId, mailboxes, settings.conversationMode, scheduledId]);

  useEffect(() => {
    if (listQuery && mailboxesLoaded) void query(listQuery);
  }, [listQuery, query, mailboxesLoaded]);

  // Nothing moves a message out of Scheduled when its hold expires, so settle
  // the folder up on the way in: sent messages to Sent, cancelled ones back to
  // Drafts, and refresh what is still waiting.
  useEffect(() => {
    if (mailboxesLoaded && mailboxId && mailboxId === scheduledId) void reconcile();
  }, [mailboxId, scheduledId, mailboxesLoaded, reconcile]);

  /*
   * With conversation view off, a row is a message rather than a thread, and
   * opening one must show that message and highlight that row -- not its whole
   * thread and every sibling row in the list.
   *
   * The thread id stays in the path, so loading is unchanged; the message rides
   * in `m`. Putting it in the URL rather than in memory is what makes a reload
   * or a shared link land back on the same message, and dropping the parameter
   * degrades to the conversation, which is the right thing for a link sent to
   * somebody whose setting differs.
   */
  const openThread = useCallback(
    (tid: Id | null, messageId?: Id | null) => {
      const base = search ? `/search` : `/mail/${mailboxId}`;
      const params = new URLSearchParams();
      if (search) params.set("q", q);
      if (tid && messageId) params.set("m", messageId);
      const qs = params.size ? `?${params}` : "";
      navigate(tid ? `${base}/${tid}${qs}` : `${base}${qs}`);
    },
    [navigate, search, mailboxId, q],
  );

  /**
   * The message the URL singles out, if any. Only meaningful with conversation
   * view off; ThreadView decides what to do when the id names nothing in the
   * thread, since it is the part that knows what the thread holds.
   */
  const openMessageId = useMemo(() => {
    if (settings.conversationMode) return null;
    const m = new URLSearchParams(searchStr).get("m");
    return m || null;
  }, [settings.conversationMode, searchStr]);

  // Row ids in list + helpers for keyboard nav
  const ids = list?.ids ?? [];
  const emails = useMail((s) => s.emails);
  const threads = useMail((s) => s.threads);
  const selected = useMail((s) => s.selected);
  const selectedAll = useMail((s) => s.selectedAll);

  const rowThreadId = useCallback((rowId: Id) => emails[rowId]?.threadId, [emails]);
  const currentRowIndex = useMemo(() => {
    if (focusId) {
      const i = ids.indexOf(focusId);
      if (i >= 0) return i;
    }
    // A cold load has no focus yet. With conversation view off the URL names the
    // row exactly; matching on the thread instead would land on whichever of its
    // messages sorts first, so j/k and the scroll-into-view would start from the
    // wrong row on any thread with more than one message in the folder.
    if (openMessageId) {
      const i = ids.indexOf(openMessageId);
      if (i >= 0) return i;
    }
    if (threadId) return ids.findIndex((id) => rowThreadId(id) === threadId);
    return -1;
  }, [ids, focusId, openMessageId, threadId, rowThreadId]);

  /** Email ids affected by an action on rows (selection or focused/open row). */
  const targetIds = useCallback(
    async (rowIds?: Id[]): Promise<Id[]> => {
      /*
       * Everything the query matches, rather than the rows that happen to be
       * loaded. Resolved from the server here and not expanded below: the
       * uncollapsed query already returns every message, and the expansion
       * below walks loaded Email objects, which is exactly what these are not.
       *
       * Only when the action came from the selection. An action aimed at one
       * row -- a right-click, a swipe -- means that row, whatever is ticked.
       */
      if (!rowIds && selectedAll) return await useMail.getState().queryAllIds();
      const rows = rowIds ?? (Object.keys(selected).length ? Object.keys(selected) : focusId ? [focusId] : threadId ? ids.filter((id) => rowThreadId(id) === threadId) : []);
      const out = new Set<Id>();
      for (const r of rows) {
        const e = emails[r];
        if (!e) continue;
        if (list?.collapseThreads) {
          const t = threads[e.threadId];
          const inScope = t ? t.emailIds.filter((id) => (list.mailboxId ? emails[id]?.mailboxIds[list.mailboxId] : true)) : [r];
          for (const id of inScope.length ? inScope : [r]) out.add(id);
        } else out.add(r);
      }
      return [...out];
    },
    [selected, selectedAll, focusId, threadId, ids, rowThreadId, emails, threads, list],
  );

  const afterAction = useCallback(
    (removed: boolean) => {
      useMail.getState().clearSelection();
      if (!removed) return;

      /*
       * Move the focused row off the message that just went away.
       *
       * Nothing did this before, so `focusId` kept pointing at a row that was
       * no longer in the list, and two separate complaints in #71 fell out of
       * it. `targetIds()` falls back to the focused id, so the next `#`
       * re-targeted the deleted message -- which the optimistic update had
       * already marked as being in Deleted Items, making it look like a
       * permanent delete and raising a confirmation the setting had turned
       * off. And `moveFocus` reads `ids.indexOf(focusId)`, which was -1, which
       * it treats as "before the start" -- so `k` clamped to the top of the
       * list.
       *
       * Clicking a row was unaffected, because that sets focus to a row that
       * exists, which is why it only ever happened from the keyboard.
       *
       * `currentRowIndex` here is the value from the render that started this
       * action, so it is the index the message had *before* it was removed.
       * The row that slid into that slot is the one to focus.
       */
      const wasAt = currentRowIndex;
      const freshIds = useMail.getState().list?.ids ?? [];
      if (!freshIds.length) {
        setFocusId(null);
      } else if (wasAt >= 0) {
        const want = settings.autoAdvance === "newer" ? wasAt - 1 : wasAt;
        const next = freshIds[Math.max(0, Math.min(want, freshIds.length - 1))];
        if (next) setFocusId(next);
      }

      // auto-advance
      if (threadId) {
        const idx = currentRowIndex;
        const adv = settings.autoAdvance;
        if (adv === "list" || idx < 0) openThread(null);
        else {
          const next = adv === "older" ? ids[idx + 1] : ids[idx - 1];
          const nt = next ? rowThreadId(next) : undefined;
          if (nt) openThread(nt);
          else openThread(null);
        }
      }
    },
    [threadId, currentRowIndex, settings.autoAdvance, ids, rowThreadId, openThread, setFocusId],
  );

  const actions = useMemo(
    () => ({
      archive: async (rows?: Id[]) => {
        const t = await targetIds(rows);
        if (!t.length) return;
        await useMail.getState().archive(t);
        afterAction(true);
      },
      trash: async (rows?: Id[]) => {
        const t = await targetIds(rows);
        if (!t.length) return;
        const mail = useMail.getState();
        const trashId = mail.roleId("trash");
        const permanent = t.every((id) => trashId && mail.emails[id]?.mailboxIds[trashId]);
        if (permanent || settings.confirmDelete) {
          // "message(s)" was doing the work a plural form should: every
          // language that inflects got a parenthesis instead of agreement.
          const ok = await confirmDialog({
            title: permanent ? translate("Delete forever?") : translate("Delete?"),
            message: permanent
              ? plural(t.length, { one: "{n} message will be permanently deleted.", other: "{n} messages will be permanently deleted." })
              : plural(t.length, { one: "Move {n} message to Trash?", other: "Move {n} messages to Trash?" }),
            confirmLabel: translate("Delete"),
            danger: permanent,
          });
          if (!ok) return;
        }
        await mail.trash(t);
        afterAction(true);
      },
      spam: async (rows?: Id[]) => {
        const t = await targetIds(rows);
        if (!t.length) return;
        const mail = useMail.getState();
        const junk = mail.roleId("junk");
        const inJunk = t.every((id) => junk && mail.emails[id]?.mailboxIds[junk]);
        await mail.spam(t, !inJunk);
        afterAction(true);
      },
      read: async (read: boolean, rows?: Id[]) => {
        const t = await targetIds(rows);
        if (t.length) await useMail.getState().markRead(t, read);
        useMail.getState().clearSelection();
      },
      star: async (on: boolean, rows?: Id[]) => {
        const t = await targetIds(rows);
        if (t.length) await useMail.getState().star(t, on);
      },
      move: async (rows?: Id[]) => {
        const t = await targetIds(rows);
        if (t.length) setMovePicker({ ids: t });
      },
      label: async (rows: Id[] | undefined, anchor: { x: number; y: number }) => {
        const t = await targetIds(rows);
        if (t.length) setLabelPicker({ ids: t, anchor });
      },
      moveTo: async (ids: Id[], mailboxId: Id) => {
        await useMail.getState().move(ids, mailboxId);
        afterAction(true);
      },
    }),
    [targetIds, afterAction, settings.confirmDelete],
  );

  // Keyboard shortcuts for the list/thread
  const focusRef = useRef(focusId);
  focusRef.current = focusId;
  useEffect(() => {
    const moveFocus = (delta: number) => {
      // A focused id that is no longer in the list gives -1, which must not be
      // read as "just before the first row" -- that is what sent `k` to the
      // top. Fall back to where the list thinks we are instead.
      const fromFocus = focusRef.current ? ids.indexOf(focusRef.current) : -1;
      const cur = fromFocus >= 0 ? fromFocus : currentRowIndex;
      const next = Math.max(0, Math.min(ids.length - 1, (cur < 0 ? (delta > 0 ? -1 : 0) : cur) + delta));
      const id = ids[next];
      if (!id) return;
      setFocusId(id);
      if (threadId && settings.readingPane !== "off") {
        const t = rowThreadId(id);
        if (t) openThread(t);
      }
      document.querySelector<HTMLElement>(`[data-row-id="${CSS.escape(id)}"]`)?.scrollIntoView({ block: "nearest" });
    };
    return keyboard.pushScope("mail", [
      { keys: "j", description: "Next conversation", group: "Mail", handler: () => moveFocus(1) },
      { keys: "k", description: "Previous conversation", group: "Mail", handler: () => moveFocus(-1) },
      { keys: "arrowdown", description: "", group: "Mail", handler: () => moveFocus(1) },
      { keys: "arrowup", description: "", group: "Mail", handler: () => moveFocus(-1) },
      { keys: "o", description: "Open conversation", group: "Mail", handler: () => { const id = focusRef.current; const t = id ? rowThreadId(id) : undefined; if (t) openThread(t); } },
      { keys: "enter", description: "", group: "Mail", handler: () => { const id = focusRef.current; const t = id ? rowThreadId(id) : undefined; if (t) { openThread(t); return; } return false; } },
      { keys: "u", description: "Back to list", group: "Mail", handler: () => openThread(null) },
      { keys: "esc", description: "Back to list / clear selection", group: "Mail", handler: () => { if (Object.keys(useMail.getState().selected).length) useMail.getState().clearSelection(); else openThread(null); } },
      { keys: "x", description: "Select conversation", group: "Mail", handler: () => { const id = focusRef.current ?? ids[currentRowIndex]; if (id) useMail.getState().select([id], !useMail.getState().selected[id]); } },
      { keys: "e", description: "Archive", group: "Actions", handler: () => void actions.archive() },
      { keys: "y", description: "", group: "Actions", handler: () => void actions.archive() },
      { keys: "#", description: "Delete", group: "Actions", handler: () => void actions.trash() },
      { keys: "delete", description: "", group: "Actions", handler: () => void actions.trash() },
      { keys: "!", description: "Report spam / not spam", group: "Actions", handler: () => void actions.spam() },
      { keys: "s", description: "Star / unstar", group: "Actions", handler: () => { void (async () => { const t = await targetIds(); const on = !t.every((id) => emails[id]?.keywords.$flagged); void actions.star(on); })(); } },
      { keys: "shift+i", description: "Mark as read", group: "Actions", handler: () => void actions.read(true) },
      { keys: "shift+u", description: "Mark as unread", group: "Actions", handler: () => void actions.read(false) },
      { keys: "v", description: "Move to…", group: "Actions", handler: () => actions.move() },
      { keys: "l", description: "Label…", group: "Actions", handler: () => actions.label(undefined, { x: window.innerWidth / 2, y: 80 }) },
      { keys: "*+a", description: "", group: "Actions", handler: () => useMail.getState().selectAll() },
      { keys: "mod+a", description: "Select all", group: "Mail", handler: () => { useMail.getState().selectAll(); } },
      { keys: "r", description: "Reply", group: "Conversation", handler: () => window.dispatchEvent(new CustomEvent("ihm:reply", { detail: "reply" })) },
      { keys: "a", description: "Reply all", group: "Conversation", handler: () => window.dispatchEvent(new CustomEvent("ihm:reply", { detail: "replyAll" })) },
      { keys: "f", description: "Forward", group: "Conversation", handler: () => window.dispatchEvent(new CustomEvent("ihm:reply", { detail: "forward" })) },
      { keys: "n", description: "Next message in conversation", group: "Conversation", handler: () => window.dispatchEvent(new CustomEvent("ihm:msg-nav", { detail: 1 })) },
      { keys: "p", description: "Previous message in conversation", group: "Conversation", handler: () => window.dispatchEvent(new CustomEvent("ihm:msg-nav", { detail: -1 })) },
      { keys: "]", description: "Archive and next", group: "Conversation", handler: () => void actions.archive() },
    ]);
  }, [ids, currentRowIndex, threadId, settings.readingPane, rowThreadId, openThread, actions, targetIds, emails]);

  const openDraft = useCompose((s) => s.openDraftEmail);
  const onOpenRow = useCallback(
    (rowId: Id) => {
      const e = emails[rowId];
      if (!e) return;
      setFocusId(rowId);
      const mb = mailboxId ? mailboxes[mailboxId] : undefined;
      if (mb?.role === "drafts" && e.keywords.$draft) {
        void openDraft(e);
        return;
      }
      openThread(e.threadId, settings.conversationMode ? null : rowId);
    },
    [emails, mailboxId, mailboxes, openThread, openDraft, settings.conversationMode],
  );

  const title = search ? translate("Search: {query}", { query: listQuery?.label ?? q }) : (mailboxId && mailboxDisplayName(mailboxes[mailboxId])) || translate("Mail");
  const reading = Boolean(threadId);
  const paneClass = settings.readingPane === "bottom" ? "pane-bottom" : settings.readingPane === "off" ? "pane-off" : "pane-right";
  const showList = !(settings.readingPane === "off" && reading) && !(narrow && reading);
  const showReading = settings.readingPane !== "off" || reading;
  const layoutRef = useRef<HTMLDivElement>(null);
  const updateSettings = useSettings((s) => s.update);
  const [liveSize, setLiveSize] = useState<number | null>(null);
  // Mirrors liveSize for the end of a key press, which follows the resize in
  // the same tick -- before the state could have come back round.
  const liveSizeRef = useRef<number | null>(null);
  const paneSize = liveSize ?? (settings.readingPane === "bottom" ? settings.listPaneHeight : settings.listPaneWidth);
  const onSplit = (delta: number) => {
    const el = layoutRef.current;
    const total = el ? (settings.readingPane === "bottom" ? el.clientHeight : el.clientWidth) : 1200;
    const min = settings.readingPane === "bottom" ? 160 : 320;
    const max = Math.max(min, total - (settings.readingPane === "bottom" ? 200 : 420));
    const next = Math.min(max, Math.max(min, (liveSizeRef.current ?? paneSize) + delta));
    liveSizeRef.current = next;
    setLiveSize(next);
  };
  const onSplitEnd = () => {
    const size = liveSizeRef.current;
    liveSizeRef.current = null;
    setLiveSize(null);
    if (size != null) updateSettings(settings.readingPane === "bottom" ? { listPaneHeight: size } : { listPaneWidth: size });
  };

  return (
    <div ref={layoutRef} className={`mail-layout ${paneClass} ${reading ? "reading" : ""}`} style={{ "--list-size": `${paneSize}px` } as React.CSSProperties}>
      {showList && (
        <MessageList
          title={title}
          list={list}
          openThreadId={threadId ?? null}
          openMessageId={openMessageId}
          focusId={focusId}
          setFocusId={setFocusId}
          onOpen={onOpenRow}
          actions={actions}
          mailboxId={mailboxId ?? null}
          isSearch={Boolean(search)}
        />
      )}
      {showList && showReading && settings.readingPane !== "off" && !narrow && (
        <Splitter direction={settings.readingPane === "bottom" ? "horizontal" : "vertical"} onResize={onSplit} onEnd={onSplitEnd} onReset={() => updateSettings(settings.readingPane === "bottom" ? { listPaneHeight: 340 } : { listPaneWidth: 520 })} ariaLabel={translate("Resize message list")} />
      )}
      {showReading && (
        <div className="mail-reading-pane">
          {threadId ? (
            <ThreadView key={`${threadId}:${openMessageId ?? ""}`} threadId={threadId} messageId={openMessageId} mailboxId={mailboxId ?? null} onBack={() => openThread(null)} actions={actions} onNavigate={(delta) => { const idx = currentRowIndex; const next = ids[idx + delta]; const t = next ? rowThreadId(next) : undefined; if (t) { setFocusId(next!); openThread(t, settings.conversationMode ? null : next!); } }} hasPrev={currentRowIndex > 0} hasNext={currentRowIndex >= 0 && currentRowIndex < ids.length - 1} />
          ) : (
            <div className="no-thread">
              <img src={withBase("/img/logo.png")} alt="" />
              <div>
                {list?.total
                  ? settings.conversationMode
                    ? plural(list.total, { one: "{n} conversation", other: "{n} conversations" })
                    : plural(list.total, { one: "{n} message", other: "{n} messages" })
                  : settings.conversationMode
                    ? translate("No conversation selected")
                    : translate("No message selected")}
              </div>
              <div className="hint">
                {settings.conversationMode
                  ? tNode("Select a conversation to read it here · Press {key} for shortcuts", { key: <kbd className="kbd">?</kbd> })
                  : tNode("Select a message to read it here · Press {key} for shortcuts", { key: <kbd className="kbd">?</kbd> })}
              </div>
            </div>
          )}
        </div>
      )}
      {movePicker && (
        <MailboxPicker
          title={plural(movePicker.ids.length, { one: "Move {n} message to…", other: "Move {n} messages to…" })}
          onClose={() => setMovePicker(null)}
          onPick={(mbId) => {
            setMovePicker(null);
            void actions.moveTo(movePicker.ids, mbId);
          }}
        />
      )}
      {labelPicker && (
        <LabelPicker
          ids={labelPicker.ids}
          anchor={labelPicker.anchor}
          onClose={() => setLabelPicker(null)}
          onApplied={() => toast.show(translate("Labels updated"))}
        />
      )}
    </div>
  );
}