import { OutputStream } from './OutputStream';

'use strict';
/**
 * Base64EncodeOutputStream
 * @author Kazuhiko Arase
 */
export class Base64EncodeOutputStream extends OutputStream {

    private buffer = 0;
    private buflen = 0;
    private length = 0;

    constructor(private ostream: OutputStream) {
        super();
    }

    public writeByte(n: number): void {

        this.buffer = (this.buffer << 8) | (n & 0xff);
        this.buflen += 8;
        this.length += 1;

        while (this.buflen >= 6) {
            this.writeEncoded(this.buffer >>> (this.buflen - 6));
            this.buflen -= 6;
        }
    }

    public flush(): void {
        if (this.buflen > 0) {
            this.writeEncoded(this.buffer << (6 - this.buflen));
            this.buffer = 0;
            this.buflen = 0;
        }

        if (this.length % 3 != 0) {
            // padding
            var padlen = 3 - this.length % 3;
            for (var i = 0; i < padlen; i += 1) {
                this.ostream.writeByte('='.charCodeAt(0));
            }
        }
    }

    private writeEncoded(b: number): void {
        this.ostream.writeByte(Base64EncodeOutputStream.encode(b & 0x3f));
    }

    private static encode(n: number): number {
        if (n < 0) {
            // error.
        } else if (n < 26) {
            return 'A'.charCodeAt(0) + n;
        } else if (n < 52) {
            return 'a'.charCodeAt(0) + (n - 26);
        } else if (n < 62) {
            return '0'.charCodeAt(0) + (n - 52);
        } else if (n == 62) {
            return '+'.charCodeAt(0);
        } else if (n == 63) {
            return '/'.charCodeAt(0);
        }
        throw 'n:' + n;
    }
}