import { Action, ActionPanel, Icon, LaunchType, List, launchCommand } from "@vicinae/api";
import { useCallback, useEffect, useMemo, useState } from "react";
import { readAttachment } from "../attachments";
import { useChat } from "../hooks/useChat";
import { useVisionSupport } from "../hooks/useVision";
import { buildThreadMarkdown, renderAttachments, type TranscriptOptions } from "../markdown";
import { getLamPreferences } from "../preferences";
import { deleteSession, listSessions, loadSession, summarizeSession } from "../sessions";
import { resolveStartup } from "../startup";
import { buildThread } from "../thread";
import type { PendingAttachment, Session, SessionSummary } from "../types";
import { recencyGroup, truncate } from "../utils";

/**
 * The chat surface: conversations on the left, the open conversation on the right.
 *
 * Modelled on Raycast's AI chat, as far as Vicinae allows:
 *
 * - The sidebar lists conversations by title only, grouped into recency
 *   sections, which buys the recency cue a timestamp on every row was trying to
 *   convey while leaving the title room to be readable.
 * - User and assistant stay visually distinct. Raycast uses right-aligned
 *   bubbles; markdown has no alignment control, so a dimmed blockquote for the
 *   question and body text for the answer is the available equivalent.
 * - Raycast pins its composer to the bottom. Vicinae's search bar is fixed at
 *   the top of the window, so that part cannot be matched.
 *
 * ## Why every row carries the same detail
 *
 * The right pane always shows the *open* conversation, not the highlighted one.
 * That is by design rather than laziness: Vicinae exposes no way to set the
 * selected row, so when ⌘N starts a new chat, the selection can stay on the row
 * the user was on and the pane would keep rendering the previous conversation.
 * Rendering the active thread on every row makes the pane follow the chat the
 * user is actually in, whatever the selection happens to be. Switching
 * conversations is explicit: Return on an empty search bar, or the action panel.
 *
 * ## Other constraints
 *
 * - The search bar is the composer. It is the only always-focused text input in
 *   a `List`, which is what makes "hit a hotkey, then just start typing" work.
 * - `filtering` is off, because the left column is a conversation switcher. The
 *   builtin fuzzy filter would hide rows as the user types their question.
 * - `Detail` accepts no typed input (`onSearchTextChange` exists only on `List`,
 *   `Grid`, `Form` and `Dropdown`), so the left column cannot be dropped: it is
 *   the text box.
 * - Conversations are ordered most-recently-updated first. Vicinae resets list
 *   selection to the first row on every model change
 *   (`GenericListView.selectFirstOnReset`), and streaming changes the model on
 *   every flush, so ordering by recency keeps the chat in progress near the top.
 * - Capturing a region does **not** happen here. It is delegated to the `snip`
 *   command, because this view owns a window and the window would be in the
 *   shot. See {@link ChatViewProps}.
 */

const EMPTY_TRANSCRIPT = "**Ask Lam anything**\n\nType a question in the search bar and press Return.";

/** Sent when a snip is attached and Return is pressed before anything is typed. */
const DEFAULT_IMAGE_PROMPT = "What is in this image?";

/** The reminder shown while a snip is attached but not yet sent. */
const PENDING_NOTE = "_Ask a question about it, or press Return to send it as it is._";

export interface ChatViewProps {
  /** Opens a specific conversation instead of resuming the latest one. */
  initialSession?: Session;
  /** Text handed over by a deeplink or fallback command. */
  initialPrompt?: string;
  /** A conversation to reload by id, which is how the snip command hands one back. */
  initialSessionId?: string;
  /** A captured image to read in, which is how the snip command hands one over. */
  initialAttachmentPath?: string;
  /** Something the launching command needs to say, such as a failed capture. */
  launchNote?: string;
}

interface SessionRow {
  id: string;
  title: string;
  updatedAt: number;
  isActive: boolean;
}

export function ChatView({
  initialSession,
  initialPrompt,
  initialSessionId,
  initialAttachmentPath,
  launchNote,
}: ChatViewProps) {
  const preferences = useMemo(() => getLamPreferences(), []);
  const chat = useChat({ preferences, initialSession });
  const { replaceSession } = chat;
  const { canSeeImages } = useVisionSupport(preferences);

  const [input, setInput] = useState(initialPrompt ?? "");
  const [summaries, setSummaries] = useState<SessionSummary[] | undefined>(undefined);
  // One flag, not two. See the startup effect below for why that matters.
  const [startup, setStartup] = useState<"loading" | "ready">(initialSession ? "ready" : "loading");
  // A captured image is held here until the user says what they want to know
  // about it. Nothing is sent to the model on capture alone.
  const [pending, setPending] = useState<PendingAttachment | undefined>(undefined);
  const [snipNote, setSnipNote] = useState<string | undefined>(undefined);

  const activeId = chat.session.id;

  const reload = useCallback(() => {
    void listSessions()
      .then(setSummaries)
      .catch(() => setSummaries([]));
  }, []);

  // Refreshed after each turn so the sidebar picks up a newly created chat.
  useEffect(() => {
    reload();
  }, [reload, chat.session.updatedAt]);

  /**
   * Everything that has to happen before the first render, in one place.
   *
   * This used to be two effects guarding two booleans, and a hand-off launch
   * satisfied the guard of *both* while setting neither, so `resumed` stayed
   * false and the view sat on "Loading conversations…" forever. Anything that
   * blocks the first render belongs in one effect with one flag, and the flag is
   * cleared in a `finally` so that no branch, including a thrown one, can leave
   * the view spinning.
   */
  useEffect(() => {
    let cancelled = false;

    void (async () => {
      try {
        const outcome = await resolveStartup(
          {
            hasInitialSession: Boolean(initialSession),
            initialSessionId,
            initialAttachmentPath,
            resumeTimeoutMs: preferences.resumeTimeoutMs,
            now: Date.now(),
          },
          { loadSession, listSessions, readAttachment },
        );

        if (cancelled) return;

        if (outcome.session) replaceSession(outcome.session);
        if (outcome.attachment) setPending(outcome.attachment);
        if (outcome.attachmentError) {
          setSnipNote(`**Could not open the screenshot:** ${outcome.attachmentError}`);
        }
      } finally {
        if (!cancelled) setStartup("ready");
      }
    })();

    return () => {
      cancelled = true;
    };
  }, [initialSession, initialSessionId, initialAttachmentPath, preferences.resumeTimeoutMs, replaceSession]);

  const thread = useMemo(
    () =>
      buildThread(chat.session.turns, {
        isStreaming: chat.isStreaming,
        response: chat.streamingResponse,
        thinking: chat.streamingThinking,
        status: chat.status,
      }),
    [chat.session.turns, chat.isStreaming, chat.streamingResponse, chat.streamingThinking, chat.status],
  );

  const transcriptOptions = useMemo<TranscriptOptions>(
    () => ({ showToolCalls: preferences.showToolCalls, showReasoning: preferences.showReasoning }),
    [preferences.showToolCalls, preferences.showReasoning],
  );

  /**
   * The transcript, preceded by any notes about this view's own state.
   *
   * Notes go first because the transcript reads newest-first: the top of the
   * panel is the text directly under the search bar, which is where the user is
   * already looking.
   */
  const threadMarkdown = useMemo(() => {
    const notes = [
      launchNote,
      snipNote,
      // The preview comes first so the captured image is visible before the user
      // decides what to ask about it, rather than only after sending.
      pending ? `${renderAttachments([pending])}\n\n${PENDING_NOTE}` : undefined,
    ].filter((note): note is string => Boolean(note));

    // The placeholder is what tells a user that the search bar is the composer.
    // When a note above already says that, printing both put the same
    // instruction twice, one line under the other.
    const empty = notes.length === 0 ? EMPTY_TRANSCRIPT : "";
    const transcript =
      thread.length === 0 ? empty : buildThreadMarkdown(thread, transcriptOptions);

    return [...notes, transcript].filter((part) => part.length > 0).join("\n\n");
  }, [launchNote, snipNote, pending, thread, transcriptOptions]);

  const rows: SessionRow[] = useMemo(() => {
    const base = summaries ?? [];

    const mapped: SessionRow[] = base.map((summary) => ({
      id: summary.id,
      title: summary.title,
      updatedAt: summary.updatedAt,
      isActive: summary.id === activeId,
    }));

    // A conversation that has not finished a turn yet is not in the index.
    if (base.some((summary) => summary.id === activeId)) return mapped;

    const active = summarizeSession(chat.session);
    return [{ id: active.id, title: active.title, updatedAt: active.updatedAt, isActive: true }, ...mapped];
  }, [summaries, activeId, chat.session]);

  /**
   * Groups the sidebar into recency sections. Rows are already sorted by
   * recency, so each group stays contiguous and can be built in one pass.
   */
  const sections = useMemo(() => {
    const grouped: { title: string; rows: SessionRow[] }[] = [];

    for (const row of rows) {
      const label = recencyGroup(row.updatedAt);
      const current = grouped[grouped.length - 1];
      if (current && current.title === label) current.rows.push(row);
      else grouped.push({ title: label, rows: [row] });
    }

    return grouped;
  }, [rows]);

  const openSession = useCallback(
    (id: string) => {
      void loadSession(id).then((session) => {
        if (session) replaceSession(session);
      });
    },
    [replaceSession],
  );

  const removeSession = useCallback(
    (id: string) => {
      void (async () => {
        await deleteSession(id);
        if (id === activeId) chat.newSession();
        reload();
      })();
    },
    [activeId, chat, reload],
  );

  /** The snip a "show me the screenshot" action would open: the pending one, else the newest. */
  const latestAttachment =
    pending ?? [...chat.session.turns].reverse().find((turn) => turn.attachments.length > 0)?.attachments[0];

  const send = useCallback(
    (text: string) => {
      const typed = text.trim();
      // With a snip attached, Return has to send even before anything is typed,
      // otherwise the only way to ask about an image is to type out a question
      // the image already implies.
      const prompt = typed || (pending ? DEFAULT_IMAGE_PROMPT : "");
      if (!prompt) return;

      chat.ask(prompt, pending);
      setPending(undefined);
      setSnipNote(undefined);
      setInput("");
    },
    [chat.ask, pending],
  );

  const hasPrompt = input.trim().length > 0 || pending !== undefined;

  const stopAction = <Action title="Stop Generating" icon={Icon.Stop} onAction={chat.cancel} />;
  const sendAction = <Action title="Send" icon={Icon.SpeechBubble} onAction={() => send(input)} />;

  const newChatAction = (
    <Action
      title="New Chat"
      icon={Icon.Plus}
      shortcut={{ key: "n", modifiers: ["cmd"] }}
      onAction={chat.newSession}
    />
  );

  /**
   * Hands the capture to the `snip` command instead of doing it here.
   *
   * Two reasons, both structural. The window has to be out of the way, and only
   * the snip command is positioned to close it before the selector appears. And
   * launching a different command is what makes the hand-off safe: Vicinae's
   * `activateEntrypoint` treats a launch of the *currently active* view command
   * as a toggle and closes the window instead of reopening it, so relaying
   * through `snip` avoids ever asking for `chat` while `chat` is active.
   *
   * Absent while streaming, because the hand-off unloads this view and would
   * abandon an answer mid-sentence.
   */
  const snipAction =
    canSeeImages && !chat.isStreaming ? (
      <Action
        title="Snip a Region"
        icon={Icon.Screenshot}
        shortcut={{ key: "s", modifiers: ["cmd", "shift"] }}
        onAction={() =>
          void launchCommand({
            name: "snip",
            type: LaunchType.UserInitiated,
            context: { sessionId: chat.session.id },
          })
        }
      />
    ) : null;

  // A screenshot is a file, so it opens in the system image viewer. Without this
  // the only way to see what was sent would be to find it on disk by hand.
  const openSnipAction = latestAttachment ? (
    <Action.Open title="Open Screenshot" icon={Icon.Image} target={latestAttachment.path} />
  ) : null;

  /**
   * The primary action adapts to the search bar. With text in it, Return sends;
   * with it empty (where sending would be a no-op anyway), Return opens the
   * highlighted conversation instead. A pending snip counts as text, so Return
   * sends it rather than navigating away.
   */
  const rowActions = (row: SessionRow) => {
    const openAction = (
      <Action title="Open Conversation" icon={Icon.CheckCircle} onAction={() => openSession(row.id)} />
    );

    return (
      <ActionPanel>
        {chat.isStreaming ? stopAction : hasPrompt ? sendAction : openAction}
        {hasPrompt ? openAction : null}
        {newChatAction}
        {snipAction}
        {openSnipAction}
        <Action
          title="Delete Conversation"
          icon={Icon.Trash}
          style="destructive"
          // The key macOS labels "delete" is backspace. Vicinae's key map has
          // `"backspace" -> Qt::Key_Backspace`, which it renders as the ⌫ token.
          shortcut={{ key: "backspace", modifiers: ["cmd", "shift"] }}
          onAction={() => removeSession(row.id)}
        />
      </ActionPanel>
    );
  };

  if (startup === "loading" || summaries === undefined) {
    return <List isLoading navigationTitle="Lam" searchBarPlaceholder="Loading conversations…" />;
  }

  const placeholder = chat.status ? `${chat.status}. Press ⏎ to stop` : "Lam is thinking. Press ⏎ to stop";

  const idlePlaceholder = pending ? "Ask about the screenshot…" : "Ask Lam anything…";

  return (
    <List
      isLoading={chat.isStreaming}
      isShowingDetail
      filtering={false}
      searchText={input}
      onSearchTextChange={setInput}
      // Raycast puts the conversation title in a header; Vicinae's nearest
      // equivalent is the status-bar title, so the open chat is named there too.
      navigationTitle={truncate(chat.session.title, 40)}
      searchBarPlaceholder={chat.isStreaming ? placeholder : idlePlaceholder}
      actions={
        <ActionPanel>
          {chat.isStreaming ? stopAction : sendAction}
          {newChatAction}
          {snipAction}
          {openSnipAction}
        </ActionPanel>
      }
    >
      {sections.map((section) => (
        <List.Section key={section.title} title={section.title}>
          {section.rows.map((row) => (
            <List.Item
              key={row.id}
              id={row.id}
              icon={row.isActive ? Icon.CheckCircle : Icon.SpeechBubble}
              title={row.title}
              // Title only. Raycast's sidebar shows nothing else, and stacking a
              // subtitle plus a timestamp on a 38px row elided the title down to
              // a few characters. The check icon is what marks the open chat.
              detail={<List.Item.Detail markdown={threadMarkdown} isLoading={chat.isStreaming} />}
              actions={rowActions(row)}
            />
          ))}
        </List.Section>
      ))}
    </List>
  );
}