import { readFile, rename, copyFile, unlink, stat } from "fs/promises";
import { config } from "../util/config.js";
import { childLogger } from "../util/logger.js";
import { isArchiveAttachment } from "../archive/detect.js";
const log = childLogger("download");
/** Maximum number of pages to scan per channel/topic to prevent infinite loops */
export const MAX_SCAN_PAGES = 5000;
/** Timeout for a single TDLib API call (ms) */
export const INVOKE_TIMEOUT_MS = 120_000; // 2 minutes
/**
 * Invoke a TDLib method with a timeout to prevent indefinite hangs.
 * If TDLib does not respond within the timeout, the promise rejects.
 */
export async function invokeWithTimeout(client, 
// eslint-disable-next-line @typescript-eslint/no-explicit-any
request, timeoutMs = INVOKE_TIMEOUT_MS) {
    return new Promise((resolve, reject) => {
        const timer = setTimeout(() => {
            reject(new Error(`TDLib invoke timed out after ${timeoutMs}ms for ${request._}`));
        }, timeoutMs);
        client.invoke(request)
            .then((result) => {
            clearTimeout(timer);
            resolve(result);
        })
            .catch((err) => {
            clearTimeout(timer);
            reject(err);
        });
    });
}
/**
 * Fetch messages from a channel, stopping once we've scanned past the
 * last-processed boundary (with one page of lookback for multipart safety).
 * Collects both archive attachments AND photo messages (for preview matching).
 * Returns messages in chronological order (oldest first).
 *
 * When `lastProcessedMessageId` is null (first run), scans everything.
 * The worker applies a post-grouping filter to skip fully-processed sets,
 * and keeps `packageExistsBySourceMessage` as a safety net.
 *
 * Safety features:
 *  - Max page limit to prevent infinite loops
 *  - Stuck detection: breaks if from_message_id stops advancing
 *  - Timeout on each TDLib API call
 */
export async function getChannelMessages(client, chatId, lastProcessedMessageId, limit = 100, onProgress) {
    const archives = [];
    const photos = [];
    const boundary = lastProcessedMessageId ? Number(lastProcessedMessageId) : null;
    let currentFromId = 0;
    let totalScanned = 0;
    let pageCount = 0;
    // eslint-disable-next-line no-constant-condition
    while (true) {
        if (pageCount >= MAX_SCAN_PAGES) {
            log.warn({ chatId: chatId.toString(), pageCount, totalScanned }, "Hit max page limit for channel scan, stopping");
            break;
        }
        pageCount++;
        const previousFromId = currentFromId;
        const result = await invokeWithTimeout(client, {
            _: "getChatHistory",
            chat_id: Number(chatId),
            from_message_id: currentFromId,
            offset: 0,
            limit: Math.min(limit, 100),
            only_local: false,
        });
        if (!result.messages || result.messages.length === 0)
            break;
        totalScanned += result.messages.length;
        for (const msg of result.messages) {
            // Check for archive documents
            const doc = msg.content?.document;
            if (doc?.file_name && doc.document && isArchiveAttachment(doc.file_name)) {
                archives.push({
                    id: BigInt(msg.id),
                    fileName: doc.file_name,
                    fileId: String(doc.document.id),
                    fileSize: BigInt(doc.document.size),
                    date: new Date(msg.date * 1000),
                });
                continue;
            }
            // Check for photo messages (potential previews)
            const photo = msg.content?.photo;
            const caption = msg.content?.caption?.text ?? "";
            if (photo?.sizes && photo.sizes.length > 0) {
                const smallest = photo.sizes[0];
                photos.push({
                    id: BigInt(msg.id),
                    date: new Date(msg.date * 1000),
                    caption,
                    fileId: String(smallest.photo.id),
                    fileSize: smallest.photo.size || smallest.photo.expected_size,
                });
            }
        }
        // Report scanning progress after each page
        onProgress?.(totalScanned);
        currentFromId = result.messages[result.messages.length - 1].id;
        // Stuck detection: if from_message_id didn't advance, break to prevent infinite loop
        if (currentFromId === previousFromId) {
            log.warn({ chatId: chatId.toString(), currentFromId, totalScanned }, "Pagination stuck (from_message_id not advancing), breaking");
            break;
        }
        // Stop scanning once we've gone past the boundary (this page is the lookback)
        if (boundary && currentFromId < boundary)
            break;
        if (result.messages.length < Math.min(limit, 100))
            break;
        // Rate limit delay
        await sleep(config.apiDelayMs);
    }
    log.info({ chatId: chatId.toString(), archives: archives.length, photos: photos.length, totalScanned, pages: pageCount }, "Channel scan complete");
    // Reverse to chronological order (oldest first) so worker processes old→new
    return {
        archives: archives.reverse(),
        photos: photos.reverse(),
        totalScanned,
    };
}
/**
 * Download a photo thumbnail from Telegram and return its raw bytes.
 * Uses synchronous download (photos are small, typically < 100KB).
 * Returns null if download fails (non-critical).
 */
export async function downloadPhotoThumbnail(client, fileId) {
    const numericId = parseInt(fileId, 10);
    try {
        const result = (await client.invoke({
            _: "downloadFile",
            file_id: numericId,
            priority: 1, // Low priority — thumbnails are nice-to-have
            offset: 0,
            limit: 0,
            synchronous: true, // Small file — wait for it
        }));
        if (result?.local?.is_downloading_completed && result.local.path) {
            const data = await readFile(result.local.path);
            log.debug({ fileId, bytes: data.length }, "Downloaded photo thumbnail");
            return data;
        }
    }
    catch (err) {
        log.warn({ fileId, err }, "Failed to download photo thumbnail");
    }
    return null;
}
/**
 * Download a file from Telegram to a local path with progress tracking
 * and integrity verification.
 *
 * Progress flow:
 *  1. Starts async download via TDLib
 *  2. Listens for `updateFile` events to track download progress
 *  3. Logs progress at every 10% increment
 *  4. Once complete, verifies the local file size matches the expected size
 *  5. Moves the file from TDLib's cache to the destination path
 *
 * Verification:
 *  - Compares actual file size on disk to the expected size from Telegram
 *  - Throws on mismatch (partial/corrupt download)
 *  - Throws on timeout (configurable, scales with file size)
 *  - Throws if download stops without completing (network error, etc.)
 */
export async function downloadFile(client, fileId, destPath, expectedSize, fileName, onProgress) {
    const numericId = parseInt(fileId, 10);
    const totalBytes = Number(expectedSize);
    log.info({ fileId, fileName, destPath, totalBytes }, "Starting file download");
    // Report initial progress
    onProgress?.({
        fileId,
        fileName,
        downloadedBytes: 0,
        totalBytes,
        percent: 0,
        isComplete: false,
    });
    return new Promise((resolve, reject) => {
        let lastLoggedPercent = 0;
        let settled = false;
        // Timeout: 10 minutes per GB, minimum 5 minutes
        const timeoutMs = Math.max(5 * 60_000, (totalBytes / (1024 * 1024 * 1024)) * 10 * 60_000);
        const timer = setTimeout(() => {
            if (!settled) {
                settled = true;
                cleanup();
                reject(new Error(`Download timed out after ${Math.round(timeoutMs / 60_000)}min for ${fileName}`));
            }
        }, timeoutMs);
        // Listen for file update events to track progress
        // eslint-disable-next-line @typescript-eslint/no-explicit-any
        const handleUpdate = (update) => {
            if (update?._ !== "updateFile")
                return;
            const file = update.file;
            if (!file || file.id !== numericId)
                return;
            const downloaded = file.local.downloaded_size;
            const percent = totalBytes > 0 ? Math.round((downloaded / totalBytes) * 100) : 0;
            // Log at every 10% increment
            if (percent >= lastLoggedPercent + 10) {
                lastLoggedPercent = percent - (percent % 10);
                log.info({ fileId, fileName, downloaded, totalBytes, percent: `${percent}%` }, "Download progress");
            }
            // Report to callback
            onProgress?.({
                fileId,
                fileName,
                downloadedBytes: downloaded,
                totalBytes,
                percent,
                isComplete: file.local.is_downloading_completed,
            });
            // Download finished
            if (file.local.is_downloading_completed) {
                if (!settled) {
                    settled = true;
                    cleanup();
                    verifyAndMove(file.local.path, destPath, totalBytes, fileName, fileId)
                        .then(resolve)
                        .catch(reject);
                }
            }
            // Download stopped without completing (network error, cancelled, etc.)
            if (!file.local.is_downloading_active &&
                !file.local.is_downloading_completed) {
                if (!settled) {
                    settled = true;
                    cleanup();
                    reject(new Error(`Download stopped unexpectedly for ${fileName} ` +
                        `(${downloaded}/${totalBytes} bytes, ${percent}%)`));
                }
            }
        };
        const cleanup = () => {
            clearTimeout(timer);
            client.off("update", handleUpdate);
        };
        // Subscribe to updates BEFORE starting download
        client.on("update", handleUpdate);
        // Start async download (non-blocking — progress via updateFile events)
        client
            .invoke({
            _: "downloadFile",
            file_id: numericId,
            priority: 32,
            offset: 0,
            limit: 0,
            synchronous: false,
        })
            .then((result) => {
            // If the file was already cached locally, invoke returns immediately
            const file = result;
            if (file?.local?.is_downloading_completed && !settled) {
                settled = true;
                cleanup();
                verifyAndMove(file.local.path, destPath, totalBytes, fileName, fileId)
                    .then(resolve)
                    .catch(reject);
            }
        })
            .catch((err) => {
            if (!settled) {
                settled = true;
                cleanup();
                reject(err);
            }
        });
    });
}
/**
 * Verify the downloaded file's size matches the expected size,
 * then move it to the destination path.
 */
async function verifyAndMove(localPath, destPath, expectedBytes, fileName, fileId) {
    const stats = await stat(localPath);
    const actualBytes = stats.size;
    if (expectedBytes > 0 && actualBytes !== expectedBytes) {
        log.error({ fileId, fileName, expectedBytes, actualBytes }, "Download size mismatch — file is incomplete or corrupted");
        throw new Error(`Download verification failed for ${fileName}: ` +
            `expected ${expectedBytes} bytes, got ${actualBytes} bytes`);
    }
    log.info({ fileId, fileName, bytes: actualBytes, destPath }, "File verified and complete");
    // Move from TDLib's cache to our temp directory.
    // Use rename first (fast, same filesystem), fall back to copy+delete
    // when source and destination are on different filesystems (EXDEV).
    try {
        await rename(localPath, destPath);
    }
    catch (err) {
        if (err.code === "EXDEV") {
            log.debug({ fileId, fileName }, "Cross-device rename — falling back to copy + unlink");
            await copyFile(localPath, destPath);
            await unlink(localPath);
        }
        else {
            throw err;
        }
    }
}
function sleep(ms) {
    return new Promise((resolve) => setTimeout(resolve, ms));
}
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