core.js

import {Buffer} from 'node:buffer';
import * as Token from 'token-types';
import * as strtok3 from 'strtok3/core'; // eslint-disable-line n/file-extension-in-import
import {
	stringToBytes,
	tarHeaderChecksumMatches,
	uint32SyncSafeToken,
} from './util.js';
import {extensions, mimeTypes} from './supported.js';

const minimumBytes = 4100; // A fair amount of file-types are detectable within this range.

export async function fileTypeFromStream(stream) {
	const tokenizer = await strtok3.fromStream(stream);
	try {
		return await fileTypeFromTokenizer(tokenizer);
	} finally {
		await tokenizer.close();
	}
}

export async function fileTypeFromBuffer(input) {
	if (!(input instanceof Uint8Array || input instanceof ArrayBuffer)) {
		throw new TypeError(`Expected the \`input\` argument to be of type \`Uint8Array\` or \`Buffer\` or \`ArrayBuffer\`, got \`${typeof input}\``);
	}

	const buffer = input instanceof Uint8Array ? input : new Uint8Array(input);

	if (!(buffer?.length > 1)) {
		return;
	}

	return fileTypeFromTokenizer(strtok3.fromBuffer(buffer));
}

export async function fileTypeFromBlob(blob) {
	const buffer = await blob.arrayBuffer();
	return fileTypeFromBuffer(new Uint8Array(buffer));
}

function _check(buffer, headers, options) {
	options = {
		offset: 0,
		...options,
	};

	for (const [index, header] of headers.entries()) {
		// If a bitmask is set
		if (options.mask) {
			// If header doesn't equal `buf` with bits masked off
			if (header !== (options.mask[index] & buffer[index + options.offset])) {
				return false;
			}
		} else if (header !== buffer[index + options.offset]) {
			return false;
		}
	}

	return true;
}

export async function fileTypeFromTokenizer(tokenizer) {
	try {
		return new FileTypeParser().parse(tokenizer);
	} catch (error) {
		if (!(error instanceof strtok3.EndOfStreamError)) {
			throw error;
		}
	}
}

class FileTypeParser {
	check(header, options) {
		return _check(this.buffer, header, options);
	}

	checkString(header, options) {
		return this.check(stringToBytes(header), options);
	}

	async parse(tokenizer) {
		this.buffer = Buffer.alloc(minimumBytes);

		// Keep reading until EOF if the file size is unknown.
		if (tokenizer.fileInfo.size === undefined) {
			tokenizer.fileInfo.size = Number.MAX_SAFE_INTEGER;
		}

		this.tokenizer = tokenizer;

		await tokenizer.peekBuffer(this.buffer, {length: 12, mayBeLess: true});

		// -- 2-byte signatures --

		if (this.check([0x42, 0x4D])) {
			return {
				ext: 'bmp',
				mime: 'image/bmp',
			};
		}

		if (this.check([0x0B, 0x77])) {
			return {
				ext: 'ac3',
				mime: 'audio/vnd.dolby.dd-raw',
			};
		}

		if (this.check([0x78, 0x01])) {
			return {
				ext: 'dmg',
				mime: 'application/x-apple-diskimage',
			};
		}

		if (this.check([0x4D, 0x5A])) {
			return {
				ext: 'exe',
				mime: 'application/x-msdownload',
			};
		}

		if (this.check([0x25, 0x21])) {
			await tokenizer.peekBuffer(this.buffer, {length: 24, mayBeLess: true});

			if (
				this.checkString('PS-Adobe-', {offset: 2})
				&& this.checkString(' EPSF-', {offset: 14})
			) {
				return {
					ext: 'eps',
					mime: 'application/eps',
				};
			}

			return {
				ext: 'ps',
				mime: 'application/postscript',
			};
		}

		if (
			this.check([0x1F, 0xA0])
			|| this.check([0x1F, 0x9D])
		) {
			return {
				ext: 'Z',
				mime: 'application/x-compress',
			};
		}

		// -- 3-byte signatures --

		if (this.check([0xEF, 0xBB, 0xBF])) { // UTF-8-BOM
			// Strip off UTF-8-BOM
			this.tokenizer.ignore(3);
			return this.parse(tokenizer);
		}

		if (this.check([0x47, 0x49, 0x46])) {
			return {
				ext: 'gif',
				mime: 'image/gif',
			};
		}

		if (this.check([0x49, 0x49, 0xBC])) {
			return {
				ext: 'jxr',
				mime: 'image/vnd.ms-photo',
			};
		}

		if (this.check([0x1F, 0x8B, 0x8])) {
			return {
				ext: 'gz',
				mime: 'application/gzip',
			};
		}

		if (this.check([0x42, 0x5A, 0x68])) {
			return {
				ext: 'bz2',
				mime: 'application/x-bzip2',
			};
		}

		if (this.checkString('ID3')) {
			await tokenizer.ignore(6); // Skip ID3 header until the header size
			const id3HeaderLength = await tokenizer.readToken(uint32SyncSafeToken);
			if (tokenizer.position + id3HeaderLength > tokenizer.fileInfo.size) {
				// Guess file type based on ID3 header for backward compatibility
				return {
					ext: 'mp3',
					mime: 'audio/mpeg',
				};
			}

			await tokenizer.ignore(id3HeaderLength);
			return fileTypeFromTokenizer(tokenizer); // Skip ID3 header, recursion
		}

		// Musepack, SV7
		if (this.checkString('MP+')) {
			return {
				ext: 'mpc',
				mime: 'audio/x-musepack',
			};
		}

		if (
			(this.buffer[0] === 0x43 || this.buffer[0] === 0x46)
			&& this.check([0x57, 0x53], {offset: 1})
		) {
			return {
				ext: 'swf',
				mime: 'application/x-shockwave-flash',
			};
		}

		// -- 4-byte signatures --

		// Requires a sample size of 4 bytes
		if (this.check([0xFF, 0xD8, 0xFF])) {
			if (this.check([0xF7], {offset: 3})) { // JPG7/SOF55, indicating a ISO/IEC 14495 / JPEG-LS file
				return {
					ext: 'jls',
					mime: 'image/jls',
				};
			}

			return {
				ext: 'jpg',
				mime: 'image/jpeg',
			};
		}

		if (this.checkString('FLIF')) {
			return {
				ext: 'flif',
				mime: 'image/flif',
			};
		}

		if (this.checkString('8BPS')) {
			return {
				ext: 'psd',
				mime: 'image/vnd.adobe.photoshop',
			};
		}

		if (this.checkString('WEBP', {offset: 8})) {
			return {
				ext: 'webp',
				mime: 'image/webp',
			};
		}

		// Musepack, SV8
		if (this.checkString('MPCK')) {
			return {
				ext: 'mpc',
				mime: 'audio/x-musepack',
			};
		}

		if (this.checkString('FORM')) {
			return {
				ext: 'aif',
				mime: 'audio/aiff',
			};
		}

		if (this.checkString('icns', {offset: 0})) {
			return {
				ext: 'icns',
				mime: 'image/icns',
			};
		}

		// Zip-based file formats
		// Need to be before the `zip` check
		if (this.check([0x50, 0x4B, 0x3, 0x4])) { // Local file header signature
			try {
				while (tokenizer.position + 30 < tokenizer.fileInfo.size) {
					await tokenizer.readBuffer(this.buffer, {length: 30});

					// https://en.wikipedia.org/wiki/Zip_(file_format)#File_headers
					const zipHeader = {
						compressedSize: this.buffer.readUInt32LE(18),
						uncompressedSize: this.buffer.readUInt32LE(22),
						filenameLength: this.buffer.readUInt16LE(26),
						extraFieldLength: this.buffer.readUInt16LE(28),
					};

					zipHeader.filename = await tokenizer.readToken(new Token.StringType(zipHeader.filenameLength, 'utf-8'));
					await tokenizer.ignore(zipHeader.extraFieldLength);

					// Assumes signed `.xpi` from addons.mozilla.org
					if (zipHeader.filename === 'META-INF/mozilla.rsa') {
						return {
							ext: 'xpi',
							mime: 'application/x-xpinstall',
						};
					}

					if (zipHeader.filename.endsWith('.rels') || zipHeader.filename.endsWith('.xml')) {
						const type = zipHeader.filename.split('/')[0];
						switch (type) {
							case '_rels':
								break;
							case 'word':
								return {
									ext: 'docx',
									mime: 'application/vnd.openxmlformats-officedocument.wordprocessingml.document',
								};
							case 'ppt':
								return {
									ext: 'pptx',
									mime: 'application/vnd.openxmlformats-officedocument.presentationml.presentation',
								};
							case 'xl':
								return {
									ext: 'xlsx',
									mime: 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet',
								};
							default:
								break;
						}
					}

					if (zipHeader.filename.startsWith('xl/')) {
						return {
							ext: 'xlsx',
							mime: 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet',
						};
					}

					if (zipHeader.filename.startsWith('3D/') && zipHeader.filename.endsWith('.model')) {
						return {
							ext: '3mf',
							mime: 'model/3mf',
						};
					}

					// The docx, xlsx and pptx file types extend the Office Open XML file format:
					// https://en.wikipedia.org/wiki/Office_Open_XML_file_formats
					// We look for:
					// - one entry named '[Content_Types].xml' or '_rels/.rels',
					// - one entry indicating specific type of file.
					// MS Office, OpenOffice and LibreOffice may put the parts in different order, so the check should not rely on it.
					if (zipHeader.filename === 'mimetype' && zipHeader.compressedSize === zipHeader.uncompressedSize) {
						let mimeType = await tokenizer.readToken(new Token.StringType(zipHeader.compressedSize, 'utf-8'));
						mimeType = mimeType.trim();

						switch (mimeType) {
							case 'application/epub+zip':
								return {
									ext: 'epub',
									mime: 'application/epub+zip',
								};
							case 'application/vnd.oasis.opendocument.text':
								return {
									ext: 'odt',
									mime: 'application/vnd.oasis.opendocument.text',
								};
							case 'application/vnd.oasis.opendocument.spreadsheet':
								return {
									ext: 'ods',
									mime: 'application/vnd.oasis.opendocument.spreadsheet',
								};
							case 'application/vnd.oasis.opendocument.presentation':
								return {
									ext: 'odp',
									mime: 'application/vnd.oasis.opendocument.presentation',
								};
							default:
						}
					}

					// Try to find next header manually when current one is corrupted
					if (zipHeader.compressedSize === 0) {
						let nextHeaderIndex = -1;

						while (nextHeaderIndex < 0 && (tokenizer.position < tokenizer.fileInfo.size)) {
							await tokenizer.peekBuffer(this.buffer, {mayBeLess: true});

							nextHeaderIndex = this.buffer.indexOf('504B0304', 0, 'hex');
							// Move position to the next header if found, skip the whole buffer otherwise
							await tokenizer.ignore(nextHeaderIndex >= 0 ? nextHeaderIndex : this.buffer.length);
						}
					} else {
						await tokenizer.ignore(zipHeader.compressedSize);
					}
				}
			} catch (error) {
				if (!(error instanceof strtok3.EndOfStreamError)) {
					throw error;
				}
			}

			return {
				ext: 'zip',
				mime: 'application/zip',
			};
		}

		if (this.checkString('OggS')) {
			// This is an OGG container
			await tokenizer.ignore(28);
			const type = Buffer.alloc(8);
			await tokenizer.readBuffer(type);

			// Needs to be before `ogg` check
			if (_check(type, [0x4F, 0x70, 0x75, 0x73, 0x48, 0x65, 0x61, 0x64])) {
				return {
					ext: 'opus',
					mime: 'audio/opus',
				};
			}

			// If ' theora' in header.
			if (_check(type, [0x80, 0x74, 0x68, 0x65, 0x6F, 0x72, 0x61])) {
				return {
					ext: 'ogv',
					mime: 'video/ogg',
				};
			}

			// If '\x01video' in header.
			if (_check(type, [0x01, 0x76, 0x69, 0x64, 0x65, 0x6F, 0x00])) {
				return {
					ext: 'ogm',
					mime: 'video/ogg',
				};
			}

			// If ' FLAC' in header  https://xiph.org/flac/faq.html
			if (_check(type, [0x7F, 0x46, 0x4C, 0x41, 0x43])) {
				return {
					ext: 'oga',
					mime: 'audio/ogg',
				};
			}

			// 'Speex  ' in header https://en.wikipedia.org/wiki/Speex
			if (_check(type, [0x53, 0x70, 0x65, 0x65, 0x78, 0x20, 0x20])) {
				return {
					ext: 'spx',
					mime: 'audio/ogg',
				};
			}

			// If '\x01vorbis' in header
			if (_check(type, [0x01, 0x76, 0x6F, 0x72, 0x62, 0x69, 0x73])) {
				return {
					ext: 'ogg',
					mime: 'audio/ogg',
				};
			}

			// Default OGG container https://www.iana.org/assignments/media-types/application/ogg
			return {
				ext: 'ogx',
				mime: 'application/ogg',
			};
		}

		if (
			this.check([0x50, 0x4B])
			&& (this.buffer[2] === 0x3 || this.buffer[2] === 0x5 || this.buffer[2] === 0x7)
			&& (this.buffer[3] === 0x4 || this.buffer[3] === 0x6 || this.buffer[3] === 0x8)
		) {
			return {
				ext: 'zip',
				mime: 'application/zip',
			};
		}

		//

		// File Type Box (https://en.wikipedia.org/wiki/ISO_base_media_file_format)
		// It's not required to be first, but it's recommended to be. Almost all ISO base media files start with `ftyp` box.
		// `ftyp` box must contain a brand major identifier, which must consist of ISO 8859-1 printable characters.
		// Here we check for 8859-1 printable characters (for simplicity, it's a mask which also catches one non-printable character).
		if (
			this.checkString('ftyp', {offset: 4})
			&& (this.buffer[8] & 0x60) !== 0x00 // Brand major, first character ASCII?
		) {
			// They all can have MIME `video/mp4` except `application/mp4` special-case which is hard to detect.
			// For some cases, we're specific, everything else falls to `video/mp4` with `mp4` extension.
			const brandMajor = this.buffer.toString('binary', 8, 12).replace('\0', ' ').trim();
			switch (brandMajor) {
				case 'avif':
				case 'avis':
					return {ext: 'avif', mime: 'image/avif'};
				case 'mif1':
					return {ext: 'heic', mime: 'image/heif'};
				case 'msf1':
					return {ext: 'heic', mime: 'image/heif-sequence'};
				case 'heic':
				case 'heix':
					return {ext: 'heic', mime: 'image/heic'};
				case 'hevc':
				case 'hevx':
					return {ext: 'heic', mime: 'image/heic-sequence'};
				case 'qt':
					return {ext: 'mov', mime: 'video/quicktime'};
				case 'M4V':
				case 'M4VH':
				case 'M4VP':
					return {ext: 'm4v', mime: 'video/x-m4v'};
				case 'M4P':
					return {ext: 'm4p', mime: 'video/mp4'};
				case 'M4B':
					return {ext: 'm4b', mime: 'audio/mp4'};
				case 'M4A':
					return {ext: 'm4a', mime: 'audio/x-m4a'};
				case 'F4V':
					return {ext: 'f4v', mime: 'video/mp4'};
				case 'F4P':
					return {ext: 'f4p', mime: 'video/mp4'};
				case 'F4A':
					return {ext: 'f4a', mime: 'audio/mp4'};
				case 'F4B':
					return {ext: 'f4b', mime: 'audio/mp4'};
				case 'crx':
					return {ext: 'cr3', mime: 'image/x-canon-cr3'};
				default:
					if (brandMajor.startsWith('3g')) {
						if (brandMajor.startsWith('3g2')) {
							return {ext: '3g2', mime: 'video/3gpp2'};
						}

						return {ext: '3gp', mime: 'video/3gpp'};
					}

					return {ext: 'mp4', mime: 'video/mp4'};
			}
		}

		if (this.checkString('MThd')) {
			return {
				ext: 'mid',
				mime: 'audio/midi',
			};
		}

		if (
			this.checkString('wOFF')
			&& (
				this.check([0x00, 0x01, 0x00, 0x00], {offset: 4})
				|| this.checkString('OTTO', {offset: 4})
			)
		) {
			return {
				ext: 'woff',
				mime: 'font/woff',
			};
		}

		if (
			this.checkString('wOF2')
			&& (
				this.check([0x00, 0x01, 0x00, 0x00], {offset: 4})
				|| this.checkString('OTTO', {offset: 4})
			)
		) {
			return {
				ext: 'woff2',
				mime: 'font/woff2',
			};
		}

		if (this.check([0xD4, 0xC3, 0xB2, 0xA1]) || this.check([0xA1, 0xB2, 0xC3, 0xD4])) {
			return {
				ext: 'pcap',
				mime: 'application/vnd.tcpdump.pcap',
			};
		}

		// Sony DSD Stream File (DSF)
		if (this.checkString('DSD ')) {
			return {
				ext: 'dsf',
				mime: 'audio/x-dsf', // Non-standard
			};
		}

		if (this.checkString('LZIP')) {
			return {
				ext: 'lz',
				mime: 'application/x-lzip',
			};
		}

		if (this.checkString('fLaC')) {
			return {
				ext: 'flac',
				mime: 'audio/x-flac',
			};
		}

		if (this.check([0x42, 0x50, 0x47, 0xFB])) {
			return {
				ext: 'bpg',
				mime: 'image/bpg',
			};
		}

		if (this.checkString('wvpk')) {
			return {
				ext: 'wv',
				mime: 'audio/wavpack',
			};
		}

		if (this.checkString('%PDF')) {
			try {
				await tokenizer.ignore(1350);
				const maxBufferSize = 10 * 1024 * 1024;
				const buffer = Buffer.alloc(Math.min(maxBufferSize, tokenizer.fileInfo.size));
				await tokenizer.readBuffer(buffer, {mayBeLess: true});

				// Check if this is an Adobe Illustrator file
				if (buffer.includes(Buffer.from('AIPrivateData'))) {
					return {
						ext: 'ai',
						mime: 'application/postscript',
					};
				}
			} catch (error) {
				// Swallow end of stream error if file is too small for the Adobe AI check
				if (!(error instanceof strtok3.EndOfStreamError)) {
					throw error;
				}
			}

			// Assume this is just a normal PDF
			return {
				ext: 'pdf',
				mime: 'application/pdf',
			};
		}

		if (this.check([0x00, 0x61, 0x73, 0x6D])) {
			return {
				ext: 'wasm',
				mime: 'application/wasm',
			};
		}

		// TIFF, little-endian type
		if (this.check([0x49, 0x49])) {
			const fileType = await this.readTiffHeader(false);
			if (fileType) {
				return fileType;
			}
		}

		// TIFF, big-endian type
		if (this.check([0x4D, 0x4D])) {
			const fileType = await this.readTiffHeader(true);
			if (fileType) {
				return fileType;
			}
		}

		if (this.checkString('MAC ')) {
			return {
				ext: 'ape',
				mime: 'audio/ape',
			};
		}

		// https://github.com/threatstack/libmagic/blob/master/magic/Magdir/matroska
		if (this.check([0x1A, 0x45, 0xDF, 0xA3])) { // Root element: EBML
			async function readField() {
				const msb = await tokenizer.peekNumber(Token.UINT8);
				let mask = 0x80;
				let ic = 0; // 0 = A, 1 = B, 2 = C, 3
				// = D

				while ((msb & mask) === 0 && mask !== 0) {
					++ic;
					mask >>= 1;
				}

				const id = Buffer.alloc(ic + 1);
				await tokenizer.readBuffer(id);
				return id;
			}

			async function readElement() {
				const id = await readField();
				const lengthField = await readField();
				lengthField[0] ^= 0x80 >> (lengthField.length - 1);
				const nrLength = Math.min(6, lengthField.length); // JavaScript can max read 6 bytes integer
				return {
					id: id.readUIntBE(0, id.length),
					len: lengthField.readUIntBE(lengthField.length - nrLength, nrLength),
				};
			}

			async function readChildren(children) {
				while (children > 0) {
					const element = await readElement();
					if (element.id === 0x42_82) {
						const rawValue = await tokenizer.readToken(new Token.StringType(element.len, 'utf-8'));
						return rawValue.replace(/\00.*$/g, ''); // Return DocType
					}

					await tokenizer.ignore(element.len); // ignore payload
					--children;
				}
			}

			const re = await readElement();
			const docType = await readChildren(re.len);

			switch (docType) {
				case 'webm':
					return {
						ext: 'webm',
						mime: 'video/webm',
					};

				case 'matroska':
					return {
						ext: 'mkv',
						mime: 'video/x-matroska',
					};

				default:
					return;
			}
		}

		// RIFF file format which might be AVI, WAV, QCP, etc
		if (this.check([0x52, 0x49, 0x46, 0x46])) {
			if (this.check([0x41, 0x56, 0x49], {offset: 8})) {
				return {
					ext: 'avi',
					mime: 'video/vnd.avi',
				};
			}

			if (this.check([0x57, 0x41, 0x56, 0x45], {offset: 8})) {
				return {
					ext: 'wav',
					mime: 'audio/vnd.wave',
				};
			}

			// QLCM, QCP file
			if (this.check([0x51, 0x4C, 0x43, 0x4D], {offset: 8})) {
				return {
					ext: 'qcp',
					mime: 'audio/qcelp',
				};
			}
		}

		if (this.checkString('SQLi')) {
			return {
				ext: 'sqlite',
				mime: 'application/x-sqlite3',
			};
		}

		if (this.check([0x4E, 0x45, 0x53, 0x1A])) {
			return {
				ext: 'nes',
				mime: 'application/x-nintendo-nes-rom',
			};
		}

		if (this.checkString('Cr24')) {
			return {
				ext: 'crx',
				mime: 'application/x-google-chrome-extension',
			};
		}

		if (
			this.checkString('MSCF')
			|| this.checkString('ISc(')
		) {
			return {
				ext: 'cab',
				mime: 'application/vnd.ms-cab-compressed',
			};
		}

		if (this.check([0xED, 0xAB, 0xEE, 0xDB])) {
			return {
				ext: 'rpm',
				mime: 'application/x-rpm',
			};
		}

		if (this.check([0xC5, 0xD0, 0xD3, 0xC6])) {
			return {
				ext: 'eps',
				mime: 'application/eps',
			};
		}

		if (this.check([0x28, 0xB5, 0x2F, 0xFD])) {
			return {
				ext: 'zst',
				mime: 'application/zstd',
			};
		}

		if (this.check([0x7F, 0x45, 0x4C, 0x46])) {
			return {
				ext: 'elf',
				mime: 'application/x-elf',
			};
		}

		if (this.check([0x21, 0x42, 0x44, 0x4E])) {
			return {
				ext: 'pst',
				mime: 'application/vnd.ms-outlook',
			};
		}

		if (this.checkString('PAR1')) {
			return {
				ext: 'parquet',
				mime: 'application/x-parquet',
			};
		}

		// -- 5-byte signatures --

		if (this.check([0x4F, 0x54, 0x54, 0x4F, 0x00])) {
			return {
				ext: 'otf',
				mime: 'font/otf',
			};
		}

		if (this.checkString('#!AMR')) {
			return {
				ext: 'amr',
				mime: 'audio/amr',
			};
		}

		if (this.checkString('{\\rtf')) {
			return {
				ext: 'rtf',
				mime: 'application/rtf',
			};
		}

		if (this.check([0x46, 0x4C, 0x56, 0x01])) {
			return {
				ext: 'flv',
				mime: 'video/x-flv',
			};
		}

		if (this.checkString('IMPM')) {
			return {
				ext: 'it',
				mime: 'audio/x-it',
			};
		}

		if (
			this.checkString('-lh0-', {offset: 2})
			|| this.checkString('-lh1-', {offset: 2})
			|| this.checkString('-lh2-', {offset: 2})
			|| this.checkString('-lh3-', {offset: 2})
			|| this.checkString('-lh4-', {offset: 2})
			|| this.checkString('-lh5-', {offset: 2})
			|| this.checkString('-lh6-', {offset: 2})
			|| this.checkString('-lh7-', {offset: 2})
			|| this.checkString('-lzs-', {offset: 2})
			|| this.checkString('-lz4-', {offset: 2})
			|| this.checkString('-lz5-', {offset: 2})
			|| this.checkString('-lhd-', {offset: 2})
		) {
			return {
				ext: 'lzh',
				mime: 'application/x-lzh-compressed',
			};
		}

		// MPEG program stream (PS or MPEG-PS)
		if (this.check([0x00, 0x00, 0x01, 0xBA])) {
			//  MPEG-PS, MPEG-1 Part 1
			if (this.check([0x21], {offset: 4, mask: [0xF1]})) {
				return {
					ext: 'mpg', // May also be .ps, .mpeg
					mime: 'video/MP1S',
				};
			}

			// MPEG-PS, MPEG-2 Part 1
			if (this.check([0x44], {offset: 4, mask: [0xC4]})) {
				return {
					ext: 'mpg', // May also be .mpg, .m2p, .vob or .sub
					mime: 'video/MP2P',
				};
			}
		}

		if (this.checkString('ITSF')) {
			return {
				ext: 'chm',
				mime: 'application/vnd.ms-htmlhelp',
			};
		}

		// -- 6-byte signatures --

		if (this.check([0xFD, 0x37, 0x7A, 0x58, 0x5A, 0x00])) {
			return {
				ext: 'xz',
				mime: 'application/x-xz',
			};
		}

		if (this.checkString('<?xml ')) {
			return {
				ext: 'xml',
				mime: 'application/xml',
			};
		}

		if (this.check([0x37, 0x7A, 0xBC, 0xAF, 0x27, 0x1C])) {
			return {
				ext: '7z',
				mime: 'application/x-7z-compressed',
			};
		}

		if (
			this.check([0x52, 0x61, 0x72, 0x21, 0x1A, 0x7])
			&& (this.buffer[6] === 0x0 || this.buffer[6] === 0x1)
		) {
			return {
				ext: 'rar',
				mime: 'application/x-rar-compressed',
			};
		}

		if (this.checkString('solid ')) {
			return {
				ext: 'stl',
				mime: 'model/stl',
			};
		}

		if (this.checkString('AC')) {
			const version = this.buffer.toString('binary', 2, 6);
			if (version.match('^d*') && version >= 1000 && version <= 1050) {
				return {
					ext: 'dwg',
					mime: 'image/vnd.dwg',
				};
			}
		}

		// -- 7-byte signatures --

		if (this.checkString('BLENDER')) {
			return {
				ext: 'blend',
				mime: 'application/x-blender',
			};
		}

		if (this.checkString('!<arch>')) {
			await tokenizer.ignore(8);
			const string = await tokenizer.readToken(new Token.StringType(13, 'ascii'));
			if (string === 'debian-binary') {
				return {
					ext: 'deb',
					mime: 'application/x-deb',
				};
			}

			return {
				ext: 'ar',
				mime: 'application/x-unix-archive',
			};
		}

		// -- 8-byte signatures --

		if (this.check([0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A])) {
			// APNG format (https://wiki.mozilla.org/APNG_Specification)
			// 1. Find the first IDAT (image data) chunk (49 44 41 54)
			// 2. Check if there is an "acTL" chunk before the IDAT one (61 63 54 4C)

			// Offset calculated as follows:
			// - 8 bytes: PNG signature
			// - 4 (length) + 4 (chunk type) + 13 (chunk data) + 4 (CRC): IHDR chunk

			await tokenizer.ignore(8); // ignore PNG signature

			async function readChunkHeader() {
				return {
					length: await tokenizer.readToken(Token.INT32_BE),
					type: await tokenizer.readToken(new Token.StringType(4, 'binary')),
				};
			}

			do {
				const chunk = await readChunkHeader();
				if (chunk.length < 0) {
					return; // Invalid chunk length
				}

				switch (chunk.type) {
					case 'IDAT':
						return {
							ext: 'png',
							mime: 'image/png',
						};
					case 'acTL':
						return {
							ext: 'apng',
							mime: 'image/apng',
						};
					default:
						await tokenizer.ignore(chunk.length + 4); // Ignore chunk-data + CRC
				}
			} while (tokenizer.position + 8 < tokenizer.fileInfo.size);

			return {
				ext: 'png',
				mime: 'image/png',
			};
		}

		if (this.check([0x41, 0x52, 0x52, 0x4F, 0x57, 0x31, 0x00, 0x00])) {
			return {
				ext: 'arrow',
				mime: 'application/x-apache-arrow',
			};
		}

		if (this.check([0x67, 0x6C, 0x54, 0x46, 0x02, 0x00, 0x00, 0x00])) {
			return {
				ext: 'glb',
				mime: 'model/gltf-binary',
			};
		}

		// `mov` format variants
		if (
			this.check([0x66, 0x72, 0x65, 0x65], {offset: 4}) // `free`
			|| this.check([0x6D, 0x64, 0x61, 0x74], {offset: 4}) // `mdat` MJPEG
			|| this.check([0x6D, 0x6F, 0x6F, 0x76], {offset: 4}) // `moov`
			|| this.check([0x77, 0x69, 0x64, 0x65], {offset: 4}) // `wide`
		) {
			return {
				ext: 'mov',
				mime: 'video/quicktime',
			};
		}

		// -- 9-byte signatures --

		if (this.check([0x49, 0x49, 0x52, 0x4F, 0x08, 0x00, 0x00, 0x00, 0x18])) {
			return {
				ext: 'orf',
				mime: 'image/x-olympus-orf',
			};
		}

		if (this.checkString('gimp xcf ')) {
			return {
				ext: 'xcf',
				mime: 'image/x-xcf',
			};
		}

		// -- 12-byte signatures --

		if (this.check([0x49, 0x49, 0x55, 0x00, 0x18, 0x00, 0x00, 0x00, 0x88, 0xE7, 0x74, 0xD8])) {
			return {
				ext: 'rw2',
				mime: 'image/x-panasonic-rw2',
			};
		}

		// ASF_Header_Object first 80 bytes
		if (this.check([0x30, 0x26, 0xB2, 0x75, 0x8E, 0x66, 0xCF, 0x11, 0xA6, 0xD9])) {
			async function readHeader() {
				const guid = Buffer.alloc(16);
				await tokenizer.readBuffer(guid);
				return {
					id: guid,
					size: Number(await tokenizer.readToken(Token.UINT64_LE)),
				};
			}

			await tokenizer.ignore(30);
			// Search for header should be in first 1KB of file.
			while (tokenizer.position + 24 < tokenizer.fileInfo.size) {
				const header = await readHeader();
				let payload = header.size - 24;
				if (_check(header.id, [0x91, 0x07, 0xDC, 0xB7, 0xB7, 0xA9, 0xCF, 0x11, 0x8E, 0xE6, 0x00, 0xC0, 0x0C, 0x20, 0x53, 0x65])) {
					// Sync on Stream-Properties-Object (B7DC0791-A9B7-11CF-8EE6-00C00C205365)
					const typeId = Buffer.alloc(16);
					payload -= await tokenizer.readBuffer(typeId);

					if (_check(typeId, [0x40, 0x9E, 0x69, 0xF8, 0x4D, 0x5B, 0xCF, 0x11, 0xA8, 0xFD, 0x00, 0x80, 0x5F, 0x5C, 0x44, 0x2B])) {
						// Found audio:
						return {
							ext: 'asf',
							mime: 'audio/x-ms-asf',
						};
					}

					if (_check(typeId, [0xC0, 0xEF, 0x19, 0xBC, 0x4D, 0x5B, 0xCF, 0x11, 0xA8, 0xFD, 0x00, 0x80, 0x5F, 0x5C, 0x44, 0x2B])) {
						// Found video:
						return {
							ext: 'asf',
							mime: 'video/x-ms-asf',
						};
					}

					break;
				}

				await tokenizer.ignore(payload);
			}

			// Default to ASF generic extension
			return {
				ext: 'asf',
				mime: 'application/vnd.ms-asf',
			};
		}

		if (this.check([0xAB, 0x4B, 0x54, 0x58, 0x20, 0x31, 0x31, 0xBB, 0x0D, 0x0A, 0x1A, 0x0A])) {
			return {
				ext: 'ktx',
				mime: 'image/ktx',
			};
		}

		if ((this.check([0x7E, 0x10, 0x04]) || this.check([0x7E, 0x18, 0x04])) && this.check([0x30, 0x4D, 0x49, 0x45], {offset: 4})) {
			return {
				ext: 'mie',
				mime: 'application/x-mie',
			};
		}

		if (this.check([0x27, 0x0A, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00], {offset: 2})) {
			return {
				ext: 'shp',
				mime: 'application/x-esri-shape',
			};
		}

		if (this.check([0x00, 0x00, 0x00, 0x0C, 0x6A, 0x50, 0x20, 0x20, 0x0D, 0x0A, 0x87, 0x0A])) {
			// JPEG-2000 family

			await tokenizer.ignore(20);
			const type = await tokenizer.readToken(new Token.StringType(4, 'ascii'));
			switch (type) {
				case 'jp2 ':
					return {
						ext: 'jp2',
						mime: 'image/jp2',
					};
				case 'jpx ':
					return {
						ext: 'jpx',
						mime: 'image/jpx',
					};
				case 'jpm ':
					return {
						ext: 'jpm',
						mime: 'image/jpm',
					};
				case 'mjp2':
					return {
						ext: 'mj2',
						mime: 'image/mj2',
					};
				default:
					return;
			}
		}

		if (
			this.check([0xFF, 0x0A])
			|| this.check([0x00, 0x00, 0x00, 0x0C, 0x4A, 0x58, 0x4C, 0x20, 0x0D, 0x0A, 0x87, 0x0A])
		) {
			return {
				ext: 'jxl',
				mime: 'image/jxl',
			};
		}

		if (this.check([0xFE, 0xFF])) { // UTF-16-BOM-LE
			if (this.check([0, 60, 0, 63, 0, 120, 0, 109, 0, 108], {offset: 2})) {
				return {
					ext: 'xml',
					mime: 'application/xml',
				};
			}

			return undefined; // Some unknown text based format
		}

		// -- Unsafe signatures --

		if (
			this.check([0x0, 0x0, 0x1, 0xBA])
			|| this.check([0x0, 0x0, 0x1, 0xB3])
		) {
			return {
				ext: 'mpg',
				mime: 'video/mpeg',
			};
		}

		if (this.check([0x00, 0x01, 0x00, 0x00, 0x00])) {
			return {
				ext: 'ttf',
				mime: 'font/ttf',
			};
		}

		if (this.check([0x00, 0x00, 0x01, 0x00])) {
			return {
				ext: 'ico',
				mime: 'image/x-icon',
			};
		}

		if (this.check([0x00, 0x00, 0x02, 0x00])) {
			return {
				ext: 'cur',
				mime: 'image/x-icon',
			};
		}

		if (this.check([0xD0, 0xCF, 0x11, 0xE0, 0xA1, 0xB1, 0x1A, 0xE1])) {
			// Detected Microsoft Compound File Binary File (MS-CFB) Format.
			return {
				ext: 'cfb',
				mime: 'application/x-cfb',
			};
		}

		// Increase sample size from 12 to 256.
		await tokenizer.peekBuffer(this.buffer, {length: Math.min(256, tokenizer.fileInfo.size), mayBeLess: true});

		// -- 15-byte signatures --

		if (this.checkString('BEGIN:')) {
			if (this.checkString('VCARD', {offset: 6})) {
				return {
					ext: 'vcf',
					mime: 'text/vcard',
				};
			}

			if (this.checkString('VCALENDAR', {offset: 6})) {
				return {
					ext: 'ics',
					mime: 'text/calendar',
				};
			}
		}

		// `raf` is here just to keep all the raw image detectors together.
		if (this.checkString('FUJIFILMCCD-RAW')) {
			return {
				ext: 'raf',
				mime: 'image/x-fujifilm-raf',
			};
		}

		if (this.checkString('Extended Module:')) {
			return {
				ext: 'xm',
				mime: 'audio/x-xm',
			};
		}

		if (this.checkString('Creative Voice File')) {
			return {
				ext: 'voc',
				mime: 'audio/x-voc',
			};
		}

		if (this.check([0x04, 0x00, 0x00, 0x00]) && this.buffer.length >= 16) { // Rough & quick check Pickle/ASAR
			const jsonSize = this.buffer.readUInt32LE(12);
			if (jsonSize > 12 && this.buffer.length >= jsonSize + 16) {
				try {
					const header = this.buffer.slice(16, jsonSize + 16).toString();
					const json = JSON.parse(header);
					// Check if Pickle is ASAR
					if (json.files) { // Final check, assuring Pickle/ASAR format
						return {
							ext: 'asar',
							mime: 'application/x-asar',
						};
					}
				} catch {}
			}
		}

		if (this.check([0x06, 0x0E, 0x2B, 0x34, 0x02, 0x05, 0x01, 0x01, 0x0D, 0x01, 0x02, 0x01, 0x01, 0x02])) {
			return {
				ext: 'mxf',
				mime: 'application/mxf',
			};
		}

		if (this.checkString('SCRM', {offset: 44})) {
			return {
				ext: 's3m',
				mime: 'audio/x-s3m',
			};
		}

		// Raw MPEG-2 transport stream (188-byte packets)
		if (this.check([0x47]) && this.check([0x47], {offset: 188})) {
			return {
				ext: 'mts',
				mime: 'video/mp2t',
			};
		}

		// Blu-ray Disc Audio-Video (BDAV) MPEG-2 transport stream has 4-byte TP_extra_header before each 188-byte packet
		if (this.check([0x47], {offset: 4}) && this.check([0x47], {offset: 196})) {
			return {
				ext: 'mts',
				mime: 'video/mp2t',
			};
		}

		if (this.check([0x42, 0x4F, 0x4F, 0x4B, 0x4D, 0x4F, 0x42, 0x49], {offset: 60})) {
			return {
				ext: 'mobi',
				mime: 'application/x-mobipocket-ebook',
			};
		}

		if (this.check([0x44, 0x49, 0x43, 0x4D], {offset: 128})) {
			return {
				ext: 'dcm',
				mime: 'application/dicom',
			};
		}

		if (this.check([0x4C, 0x00, 0x00, 0x00, 0x01, 0x14, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0xC0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x46])) {
			return {
				ext: 'lnk',
				mime: 'application/x.ms.shortcut', // Invented by us
			};
		}

		if (this.check([0x62, 0x6F, 0x6F, 0x6B, 0x00, 0x00, 0x00, 0x00, 0x6D, 0x61, 0x72, 0x6B, 0x00, 0x00, 0x00, 0x00])) {
			return {
				ext: 'alias',
				mime: 'application/x.apple.alias', // Invented by us
			};
		}

		if (
			this.check([0x4C, 0x50], {offset: 34})
			&& (
				this.check([0x00, 0x00, 0x01], {offset: 8})
				|| this.check([0x01, 0x00, 0x02], {offset: 8})
				|| this.check([0x02, 0x00, 0x02], {offset: 8})
			)
		) {
			return {
				ext: 'eot',
				mime: 'application/vnd.ms-fontobject',
			};
		}

		if (this.check([0x06, 0x06, 0xED, 0xF5, 0xD8, 0x1D, 0x46, 0xE5, 0xBD, 0x31, 0xEF, 0xE7, 0xFE, 0x74, 0xB7, 0x1D])) {
			return {
				ext: 'indd',
				mime: 'application/x-indesign',
			};
		}

		// Increase sample size from 256 to 512
		await tokenizer.peekBuffer(this.buffer, {length: Math.min(512, tokenizer.fileInfo.size), mayBeLess: true});

		// Requires a buffer size of 512 bytes
		if (tarHeaderChecksumMatches(this.buffer)) {
			return {
				ext: 'tar',
				mime: 'application/x-tar',
			};
		}

		if (this.check([0xFF, 0xFE])) { // UTF-16-BOM-BE
			if (this.check([60, 0, 63, 0, 120, 0, 109, 0, 108, 0], {offset: 2})) {
				return {
					ext: 'xml',
					mime: 'application/xml',
				};
			}

			if (this.check([0xFF, 0x0E, 0x53, 0x00, 0x6B, 0x00, 0x65, 0x00, 0x74, 0x00, 0x63, 0x00, 0x68, 0x00, 0x55, 0x00, 0x70, 0x00, 0x20, 0x00, 0x4D, 0x00, 0x6F, 0x00, 0x64, 0x00, 0x65, 0x00, 0x6C, 0x00], {offset: 2})) {
				return {
					ext: 'skp',
					mime: 'application/vnd.sketchup.skp',
				};
			}

			return undefined; // Some text based format
		}

		if (this.checkString('-----BEGIN PGP MESSAGE-----')) {
			return {
				ext: 'pgp',
				mime: 'application/pgp-encrypted',
			};
		}

		// Check MPEG 1 or 2 Layer 3 header, or 'layer 0' for ADTS (MPEG sync-word 0xFFE)
		if (this.buffer.length >= 2 && this.check([0xFF, 0xE0], {offset: 0, mask: [0xFF, 0xE0]})) {
			if (this.check([0x10], {offset: 1, mask: [0x16]})) {
				// Check for (ADTS) MPEG-2
				if (this.check([0x08], {offset: 1, mask: [0x08]})) {
					return {
						ext: 'aac',
						mime: 'audio/aac',
					};
				}

				// Must be (ADTS) MPEG-4
				return {
					ext: 'aac',
					mime: 'audio/aac',
				};
			}

			// MPEG 1 or 2 Layer 3 header
			// Check for MPEG layer 3
			if (this.check([0x02], {offset: 1, mask: [0x06]})) {
				return {
					ext: 'mp3',
					mime: 'audio/mpeg',
				};
			}

			// Check for MPEG layer 2
			if (this.check([0x04], {offset: 1, mask: [0x06]})) {
				return {
					ext: 'mp2',
					mime: 'audio/mpeg',
				};
			}

			// Check for MPEG layer 1
			if (this.check([0x06], {offset: 1, mask: [0x06]})) {
				return {
					ext: 'mp1',
					mime: 'audio/mpeg',
				};
			}
		}
	}

	async readTiffTag(bigEndian) {
		const tagId = await this.tokenizer.readToken(bigEndian ? Token.UINT16_BE : Token.UINT16_LE);
		this.tokenizer.ignore(10);
		switch (tagId) {
			case 50_341:
				return {
					ext: 'arw',
					mime: 'image/x-sony-arw',
				};
			case 50_706:
				return {
					ext: 'dng',
					mime: 'image/x-adobe-dng',
				};
			default:
		}
	}

	async readTiffIFD(bigEndian) {
		const numberOfTags = await this.tokenizer.readToken(bigEndian ? Token.UINT16_BE : Token.UINT16_LE);
		for (let n = 0; n < numberOfTags; ++n) {
			const fileType = await this.readTiffTag(bigEndian);
			if (fileType) {
				return fileType;
			}
		}
	}

	async readTiffHeader(bigEndian) {
		const version = (bigEndian ? Token.UINT16_BE : Token.UINT16_LE).get(this.buffer, 2);
		const ifdOffset = (bigEndian ? Token.UINT32_BE : Token.UINT32_LE).get(this.buffer, 4);

		if (version === 42) {
			// TIFF file header
			if (ifdOffset >= 6) {
				if (this.checkString('CR', {offset: 8})) {
					return {
						ext: 'cr2',
						mime: 'image/x-canon-cr2',
					};
				}

				if (ifdOffset >= 8 && (this.check([0x1C, 0x00, 0xFE, 0x00], {offset: 8}) || this.check([0x1F, 0x00, 0x0B, 0x00], {offset: 8}))) {
					return {
						ext: 'nef',
						mime: 'image/x-nikon-nef',
					};
				}
			}

			await this.tokenizer.ignore(ifdOffset);
			const fileType = await this.readTiffIFD(bigEndian);
			return fileType ?? {
				ext: 'tif',
				mime: 'image/tiff',
			};
		}

		if (version === 43) {	// Big TIFF file header
			return {
				ext: 'tif',
				mime: 'image/tiff',
			};
		}
	}
}

export async function fileTypeStream(readableStream, {sampleSize = minimumBytes} = {}) {
	const {default: stream} = await import('node:stream');

	return new Promise((resolve, reject) => {
		readableStream.on('error', reject);

		readableStream.once('readable', () => {
			(async () => {
				try {
					// Set up output stream
					const pass = new stream.PassThrough();
					const outputStream = stream.pipeline ? stream.pipeline(readableStream, pass, () => {}) : readableStream.pipe(pass);

					// Read the input stream and detect the filetype
					const chunk = readableStream.read(sampleSize) ?? readableStream.read() ?? Buffer.alloc(0);
					try {
						const fileType = await fileTypeFromBuffer(chunk);
						pass.fileType = fileType;
					} catch (error) {
						if (error instanceof strtok3.EndOfStreamError) {
							pass.fileType = undefined;
						} else {
							reject(error);
						}
					}

					resolve(outputStream);
				} catch (error) {
					reject(error);
				}
			})();
		});
	});
}

export const supportedExtensions = new Set(extensions);
export const supportedMimeTypes = new Set(mimeTypes);