import yauzl from "yauzl";
import { open as fsOpen, stat as fsStat } from "fs/promises";
import path from "path";
import { Readable } from "stream";
import { childLogger } from "../util/logger.js";
const log = childLogger("zip-reader");
/**
 * Read the central directory of a ZIP file without extracting any contents.
 * For multipart ZIPs (.zip.001, .zip.002 etc.), uses a custom random-access
 * reader that spans all parts seamlessly so yauzl can find the central
 * directory at the end of the combined data.
 */
export async function readZipCentralDirectory(filePaths) {
    if (filePaths.length === 1) {
        return readSingleZip(filePaths[0]);
    }
    // Multipart: use a spanning random-access reader
    return readMultipartZip(filePaths);
}
/** Read a single (non-split) ZIP file. */
function readSingleZip(targetFile) {
    return new Promise((resolve) => {
        yauzl.open(targetFile, { lazyEntries: true, autoClose: true }, (err, zipFile) => {
            if (err) {
                log.warn({ err, file: targetFile }, "Failed to open ZIP for reading");
                resolve([]);
                return;
            }
            const entries = [];
            zipFile.readEntry();
            zipFile.on("entry", (entry) => {
                if (!entry.fileName.endsWith("/")) {
                    const ext = path.extname(entry.fileName).toLowerCase();
                    entries.push({
                        path: entry.fileName,
                        fileName: path.basename(entry.fileName),
                        extension: ext ? ext.slice(1) : null,
                        compressedSize: BigInt(entry.compressedSize),
                        uncompressedSize: BigInt(entry.uncompressedSize),
                        crc32: entry.crc32 !== 0 ? entry.crc32.toString(16).padStart(8, "0") : null,
                    });
                }
                zipFile.readEntry();
            });
            zipFile.on("end", () => resolve(entries));
            zipFile.on("error", (error) => {
                log.warn({ error, file: targetFile }, "Error reading ZIP entries");
                resolve(entries);
            });
        });
    });
}
/**
 * Read a multipart split ZIP using yauzl's RandomAccessReader API.
 * This creates a virtual "file" that spans all parts so yauzl can
 * seek freely across the entire archive to read the central directory.
 */
async function readMultipartZip(filePaths) {
    // Get sizes of all parts
    const partSizes = [];
    for (const fp of filePaths) {
        const s = await fsStat(fp);
        partSizes.push(s.size);
    }
    const totalSize = partSizes.reduce((a, b) => a + b, 0);
    log.debug({ parts: filePaths.length, totalSize }, "Reading multipart ZIP via spanning reader");
    return new Promise((resolve) => {
        const reader = createMultiPartReader(filePaths, partSizes);
        yauzl.fromRandomAccessReader(reader, totalSize, { lazyEntries: true, autoClose: true }, (err, zipFile) => {
            if (err) {
                log.warn({ err }, "Failed to open multipart ZIP for reading");
                reader.close(() => { });
                resolve([]);
                return;
            }
            const entries = [];
            zipFile.readEntry();
            zipFile.on("entry", (entry) => {
                if (!entry.fileName.endsWith("/")) {
                    const ext = path.extname(entry.fileName).toLowerCase();
                    entries.push({
                        path: entry.fileName,
                        fileName: path.basename(entry.fileName),
                        extension: ext ? ext.slice(1) : null,
                        compressedSize: BigInt(entry.compressedSize),
                        uncompressedSize: BigInt(entry.uncompressedSize),
                        crc32: entry.crc32 !== 0 ? entry.crc32.toString(16).padStart(8, "0") : null,
                    });
                }
                zipFile.readEntry();
            });
            zipFile.on("end", () => {
                log.info({ entries: entries.length }, "Multipart ZIP entries read");
                resolve(entries);
            });
            zipFile.on("error", (error) => {
                log.warn({ error }, "Error reading multipart ZIP entries");
                resolve(entries);
            });
        });
    });
}
/**
 * Create a yauzl RandomAccessReader that reads across multiple split part files.
 * Maps a global offset to the correct part file and local offset.
 *
 * Uses Object.create to properly inherit from yauzl.RandomAccessReader
 * (whose constructor + prototype is defined at runtime, not as a TS class).
 */
function createMultiPartReader(filePaths, partSizes) {
    // Build cumulative offset table
    const partOffsets = [];
    let offset = 0;
    for (const size of partSizes) {
        partOffsets.push(offset);
        offset += size;
    }
    // Create an instance by calling the parent constructor
    // eslint-disable-next-line @typescript-eslint/no-explicit-any
    const reader = new yauzl.RandomAccessReader();
    // Override _readStreamForRange — yauzl calls this to read a range of bytes
    // eslint-disable-next-line @typescript-eslint/no-explicit-any
    reader._readStreamForRange = function (start, end) {
        const readable = new Readable({ read() { } });
        readRange(start, end, readable).catch((err) => {
            readable.destroy(err);
        });
        return readable;
    };
    async function readRange(start, end, readable) {
        let remaining = end - start;
        let globalOffset = start;
        while (remaining > 0) {
            // Find which part this offset falls in
            let partIdx = partOffsets.length - 1;
            for (let i = 0; i < partOffsets.length; i++) {
                if (i + 1 < partOffsets.length && globalOffset < partOffsets[i + 1]) {
                    partIdx = i;
                    break;
                }
            }
            const localOffset = globalOffset - partOffsets[partIdx];
            const partRemaining = partSizes[partIdx] - localOffset;
            const toRead = Math.min(remaining, partRemaining);
            const fh = await fsOpen(filePaths[partIdx], "r");
            try {
                const buf = Buffer.alloc(toRead);
                const { bytesRead } = await fh.read(buf, 0, toRead, localOffset);
                readable.push(buf.subarray(0, bytesRead));
                remaining -= bytesRead;
                globalOffset += bytesRead;
            }
            finally {
                await fh.close();
            }
        }
        readable.push(null); // Signal end of stream
    }
    return reader;
}
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