import "../";

export { STDIO } from "../";

export function readFileSync(fd: number): Uint8Array {
	let buffer = new Uint8Array(1024);
	let bytesUsed = 0;
	while (true) {
		const bytesRead = Javy.IO.readSync(fd, buffer.subarray(bytesUsed));
		// A negative number of bytes read indicates an error.
		if (bytesRead < 0) {
			// FIXME: Figure out the specific error that occured.
			throw Error("Error while reading from file descriptor");
		}
		// 0 bytes read means we have reached EOF.
		if (bytesRead === 0) {
			return buffer.subarray(0, bytesUsed + bytesRead);
		}

		bytesUsed += bytesRead;
		// If we have filled the buffer, but have not reached EOF yet,
		// double the buffers capacity and continue.
		if (bytesUsed === buffer.length) {
			const nextBuffer = new Uint8Array(buffer.length * 2);
			nextBuffer.set(buffer);
			buffer = nextBuffer;
		}
	}
}

export function writeFileSync(fd: number, buffer: Uint8Array) {
	while (buffer.length > 0) {
		// Try to write the entire buffer.
		const bytesWritten = Javy.IO.writeSync(fd, buffer);
		// A negative number of bytes written indicates an error.
		if (bytesWritten < 0) {
			throw Error("Error while writing to file descriptor");
		}
		// 0 bytes means that the destination cannot accept additional bytes.
		if (bytesWritten === 0) {
			throw Error("Could not write all contents in buffer to file descriptor");
		}
		// Otherwise cut off the bytes from the buffer that
		// were successfully written.
		buffer = buffer.subarray(bytesWritten);
	}
}