beavergram/frontend/src/lib/api/media.ts

import { requestMedia } from "#lib/api/client.js";
import { getMessageMedia, transcribeMedia } from "#lib/api/endpoints.js";
import type { MediaRef } from "#lib/api/types.js";
import { accounts } from "#lib/stores/accounts.svelte.js";

const TRANSCRIBE_TRIES = 10;
const TRANSCRIBE_DELAY = 2000;

export type InlineMedia =
  | {
      state: "ready";
      mediaId: number;
      kind: string;
      mime: string | null;
      url: string;
      transcript: string | null;
    }
  | { state: "not-downloaded"; mediaId: number; kind: string }
  | { state: "missing" };

export interface ViewerItem {
  caption?: string;
  downloaded: boolean;
  fileName: string | null;
  fileSize: number | null;
  kind: string;
  mediaId: number | null;
  messageId: number;
  mime: string | null;
  src?: string;
}

export function viewerItemsFrom(
  messageId: number,
  media: MediaRef[]
): ViewerItem[] {
  if (media.length === 0) {
    return [
      {
        downloaded: false,
        fileName: null,
        fileSize: null,
        kind: "",
        mediaId: null,
        messageId,
        mime: null,
      },
    ];
  }
  return media.map((item) => ({
    downloaded: item.downloaded,
    fileName: item.file_name,
    fileSize: item.file_size,
    kind: item.kind,
    mediaId: item.id,
    messageId: item.message_id,
    mime: item.mime,
  }));
}

const PREVIEW_KINDS = new Set([
  "photo",
  "video",
  "video_note",
  "animation",
  "gif",
  "sticker",
  "voice",
  "audio",
]);

const PREVIEW_MIME_PREFIXES = ["image/", "video/", "audio/"];

export function isPreviewable(kind: string, mime: string | null): boolean {
  if (PREVIEW_KINDS.has(kind)) {
    return true;
  }
  return PREVIEW_MIME_PREFIXES.some((prefix) => mime?.startsWith(prefix));
}

const ACTIVE_MIMES = new Set([
  "text/html",
  "application/xhtml+xml",
  "image/svg+xml",
  "text/xml",
  "application/xml",
]);

export function isActiveContent(mime: string | null): boolean {
  return ACTIVE_MIMES.has(mime?.split(";", 1)[0].trim().toLowerCase() ?? "");
}

export type VisualKind = "image" | "video" | "other";

const VIDEO_KINDS = new Set(["video", "video_note", "animation", "gif"]);

export function visualKind(kind: string): VisualKind {
  if (kind === "photo") {
    return "image";
  }
  if (VIDEO_KINDS.has(kind)) {
    return "video";
  }
  return "other";
}

const STREAM_KINDS = new Set(["video", "video_note", "voice", "audio"]);
const STREAM_MIME_PREFIXES = ["video/", "audio/"];

export function isStreamable(kind: string, mime: string | null): boolean {
  return (
    STREAM_KINDS.has(kind) ||
    STREAM_MIME_PREFIXES.some((prefix) => mime?.startsWith(prefix))
  );
}

const MAX_CACHED = 200;

const ready = new Map<string, InlineMedia>();
const inflight = new Map<string, Promise<InlineMedia>>();

function remember(
  cache: Map<string, InlineMedia>,
  key: string,
  item: InlineMedia
) {
  cache.set(key, item);
  while (cache.size > MAX_CACHED) {
    const oldest = cache.keys().next();
    if (oldest.done) {
      return;
    }
    const stale = cache.get(oldest.value);
    cache.delete(oldest.value);
    if (stale?.state === "ready") {
      URL.revokeObjectURL(stale.url);
    }
  }
}

function cacheKey(account: number, chatId: number, messageId: number): string {
  return `${account}:${chatId}:${messageId}`;
}

function forget(cache: Map<string, InlineMedia>, key: string) {
  const stale = cache.get(key);
  cache.delete(key);
  if (stale?.state === "ready") {
    URL.revokeObjectURL(stale.url);
  }
}

export function forgetMedia(
  chatId: number,
  messageId: number,
  mediaId: number
): void {
  const account = accounts.selectedId;
  if (account !== null) {
    forget(ready, cacheKey(account, chatId, messageId));
    forget(byId, `${account}:${mediaId}`);
  }
}

async function resolve(
  chatId: number,
  messageId: number
): Promise<InlineMedia> {
  let meta: Awaited<ReturnType<typeof getMessageMedia>>;
  try {
    meta = await getMessageMedia(chatId, messageId);
  } catch {
    return { state: "missing" };
  }
  if (!meta.downloaded) {
    return { kind: meta.kind, mediaId: meta.id, state: "not-downloaded" };
  }
  const blob = await requestMedia(meta.id);
  if (blob.state === "ready") {
    return {
      kind: meta.kind,
      mediaId: meta.id,
      mime: blob.mime,
      state: "ready",
      transcript: meta.extracted_text,
      url: blob.url,
    };
  }
  if (blob.state === "not-downloaded") {
    return { kind: meta.kind, mediaId: meta.id, state: "not-downloaded" };
  }
  return { state: "missing" };
}

const byId = new Map<string, InlineMedia>();
const byIdInflight = new Map<string, Promise<InlineMedia>>();

async function resolveById(media: MediaRef): Promise<InlineMedia> {
  if (media.id === null) {
    return { state: "missing" };
  }
  if (!media.downloaded) {
    return { kind: media.kind, mediaId: media.id, state: "not-downloaded" };
  }
  const blob = await requestMedia(media.id);
  if (blob.state === "ready") {
    return {
      kind: media.kind,
      mediaId: media.id,
      mime: blob.mime,
      state: "ready",
      transcript: null,
      url: blob.url,
    };
  }
  if (blob.state === "not-downloaded") {
    return { kind: media.kind, mediaId: media.id, state: "not-downloaded" };
  }
  return { state: "missing" };
}

export function loadMediaItem(media: MediaRef): Promise<InlineMedia> {
  const account = accounts.selectedId;
  if (account === null || media.id === null) {
    return Promise.resolve<InlineMedia>({ state: "missing" });
  }
  const key = `${account}:${media.id}`;
  const cached = byId.get(key);
  if (cached) {
    return Promise.resolve(cached);
  }
  const existing = byIdInflight.get(key);
  if (existing) {
    return existing;
  }
  const promise = resolveById(media)
    .then((result) => {
      if (result.state === "ready") {
        remember(byId, key, result);
      }
      return result;
    })
    .finally(() => {
      byIdInflight.delete(key);
    });
  byIdInflight.set(key, promise);
  return promise;
}

function patchTranscript(
  chatId: number,
  messageId: number,
  text: string
): void {
  const account = accounts.selectedId;
  if (account === null) {
    return;
  }
  const cached = ready.get(cacheKey(account, chatId, messageId));
  if (cached?.state === "ready") {
    cached.transcript = text;
  }
}

export async function requestTranscription(
  chatId: number,
  messageId: number
): Promise<string | null> {
  await transcribeMedia(chatId, messageId);
  for (let i = 0; i < TRANSCRIBE_TRIES; i += 1) {
    // biome-ignore lint/performance/noAwaitInLoops: polling waits between tries on purpose
    await new Promise((done) => {
      setTimeout(done, TRANSCRIBE_DELAY);
    });
    try {
      const meta = await getMessageMedia(chatId, messageId);
      if (meta.extracted_text) {
        patchTranscript(chatId, messageId, meta.extracted_text);
        return meta.extracted_text;
      }
    } catch {
      return null;
    }
  }
  return null;
}

export function loadInlineMedia(
  chatId: number,
  messageId: number
): Promise<InlineMedia> {
  const account = accounts.selectedId;
  if (account === null) {
    return Promise.resolve<InlineMedia>({ state: "missing" });
  }
  const key = cacheKey(account, chatId, messageId);
  const cached = ready.get(key);
  if (cached) {
    return Promise.resolve(cached);
  }
  const existing = inflight.get(key);
  if (existing) {
    return existing;
  }
  const promise = resolve(chatId, messageId)
    .then((result) => {
      if (result.state === "ready") {
        remember(ready, key, result);
      }
      return result;
    })
    .finally(() => {
      inflight.delete(key);
    });
  inflight.set(key, promise);
  return promise;
}