Javascript parse CSV

csv_iterate.mjs

const END_OF_FIELD = Symbol('\u001f');
const END_OF_RECORD = Symbol('\u001e');


export async function* csv_iterate(text_stream) {
	// public iterator.

	if (typeof text_stream === 'string')
		text_stream = [text_stream];

	else if (text_stream instanceof Blob)
		text_stream = text_stream.stream().pipeThrough(new TextDecoderStream(
			text_stream.type?.match(/;\s*charset=("?)(?<value>\S+)(?=\1)/).groups.value ?? 'utf-8',
			{ fatal: true, ignoreBOM: true }
		));

	else if (text_stream instanceof Response)
		text_stream = text_stream.body.pipeThrough(new TextDecoderStream((
			text_stream.headers.get('content-type')?.match(/;\s*charset=("?)(?<value>\S+)(?=\1)/).groups.value ?? 'utf-8',
			{ fatal: true, ignoreBOM: true }
		));

	const rows = csv_iterate_1(text_stream);
	const keys = (await rows.next()).value;
	for await (const row of rows) {
		if (row.length === keys.length)
			yield Object.fromEntries(keys.map((k, i) => [k, row[i]]));
		else
			yield Object.fromEntries(row.map((v, i) => [keys[i] ?? `_${i+1}`,v]));
	}
}


async function* csv_iterate_1(text_stream) {
	// core iterator.

	let field = "";
	let row = [];

	for await (const token of csv_iterate_2(text_stream)) {
		switch (token) {
			case END_OF_FIELD:
				row.push(field);
				field = "";
				break;

			case END_OF_RECORD:
				row.push(field);
				field = "";
				yield row;
				row = [];
				break;

			default:
				field += token;
		}
	}

	// END_OF_FILE
	row.push(field);
	yield row;
}

async function* csv_iterate_2(text_stream) {
	// meta tokenizer.

	let state = 0;

	for await (const s of csv_iterate_3(text_stream)) {
		switch (state) {
			case 1:
				// Inside quotes
				if (s !== '"') {
					yield s;
				} else {
					state = 2;
				}
				break;

			case 2:
				// Maybe exiting quotes
				if (s !== '"') {
					state = 0;
					'goto case 0';
				} else {
					// Nope, just an escaped quote
					yield s;
					state = 1;
					break;
				}

			case 0:
				// Not in quotes
				switch (s) {
					case ',':
						yield END_OF_FIELD;
						break;

					case '\n':
					case '\r\n':
						yield END_OF_RECORD;
						break;

					case '"':
						// Entering quotes
						state = 1;
						break;

					default:
						yield s;
				}
			break;
		}
	}
}


async function* csv_iterate_3(text_stream) {
	// raw tokenizer.

	let maybeSplitCrlf = false;

	for await (const chunk of text_stream) {
		for (const [s] of chunk.matchAll(/(?:,|\r?\n|"|.+?(?=,|\r?\n|"|$))/gs)) {
			if (maybeSplitCrlf) {
				// codepath to handle data that would have matched as CRLF were it not for a chunk boundary in the underlying stream
				if (s === '\n') {
					yield '\r\n';
					maybeSplitCrlf = false;
					continue;
				}
				maybeSplitCrlf = false;
			}

			if (s === '\r') {
				maybeSplitCrlf = true;
				continue;
			}

			yield s;
		}
	}

	if (maybeSplitCrlf)
		// was not actually a split CRLF, we still owe caller this token
		yield '\r';
}

temp0 = await (
	fetch('https://ccadb.my.salesforce-sites.com/mozilla/IncludedCACertificateReportCSVFormat')
	.then(r => Array.fromAsync(csv_iterate(r)))
);

db = await new Promise((resolve, reject) => {
	const req = indexedDB.open("test", 2460825);
	req.addEventListener('error', (event) => void reject(event.error || event.target.error));
	req.addEventListener('success', (event) => void resolve(event.target.result));
	req.addEventListener('upgradeneeded', (event) => {
		const db = event.target.result;
		db.createObjectStore("IncludedCACertificateReport");
	});
});

try {
	await new Promise((resolve, reject) => {
		const txn = db.transaction("IncludedCACertificateReport", 'readwrite');
		txn.addEventListener('abort', (event) => void reject(new Error(`${Object.getPrototypeOf(event.target).constructor.name}: ${event.type} event`, { cause: event })));
		txn.addEventListener('complete', (event) => void resolve(event.target.transaction));
		txn.addEventListener('error', (event) => void reject(event.error || event.target.error));

		const os = txn.objectStore("IncludedCACertificateReport");
		
		temp0.forEach((record) => {
			os.put(record, record["SHA-256 Fingerprint"].replaceAll(/(\w{2})(?=\w)/g, "$1:").toLowerCase());
		});
	});
} finally {
	await db.close();
}