import { BSONError } from './error';

type TextDecoder = {

readonly encoding: string;

readonly fatal: boolean;

readonly ignoreBOM: boolean;

decode(input?: Uint8Array): string;

};

type TextDecoderConstructor = {

new (label: 'utf8', options: { fatal: boolean; ignoreBOM?: boolean }): TextDecoder;

};

// parse utf8 globals

declare const TextDecoder: TextDecoderConstructor;

let TextDecoderFatal: TextDecoder;

let TextDecoderNonFatal: TextDecoder;

/**

* Determines if the passed in bytes are valid utf8

* @param bytes - An array of 8-bit bytes. Must be indexable and have length property

* @param start - The index to start validating

* @param end - The index to end validating

*/

export function parseUtf8(buffer: Uint8Array, start: number, end: number, fatal: boolean): string {

if (fatal) {

TextDecoderFatal ??= new TextDecoder('utf8', { fatal: true });

try {

return TextDecoderFatal.decode(buffer.subarray(start, end));

} catch (cause) {

throw new BSONError('Invalid UTF-8 string in BSON document', { cause });

}

}

TextDecoderNonFatal ??= new TextDecoder('utf8', { fatal: false });

return TextDecoderNonFatal.decode(buffer.subarray(start, end));

}