'use strict';

import { HashZero } from '../constants';
import { checkNormalize } from '../errors';
import { arrayify, concat, hexlify } from './bytes';

///////////////////////////////
// Imported Types

import { Arrayish } from './bytes';

///////////////////////////////

export enum UnicodeNormalizationForm {
    current  = '',
    NFC      = 'NFC',
    NFD      = 'NFD',
    NFKC     = 'NFKC',
    NFKD     = 'NFKD'
};

// http://stackoverflow.com/questions/18729405/how-to-convert-utf8-string-to-byte-array
export function toUtf8Bytes(str: string, form: UnicodeNormalizationForm = UnicodeNormalizationForm.current): Uint8Array {

    if (form != UnicodeNormalizationForm.current) {
        checkNormalize();
        str = str.normalize(form);
    }

    var result = [];
    for (var i = 0; i < str.length; i++) {
        var c = str.charCodeAt(i);

        if (c < 0x80) {
            result.push(c);

        } else if (c < 0x800) {
            result.push((c >> 6) | 0xc0);
            result.push((c & 0x3f) | 0x80);

        } else if ((c & 0xfc00) == 0xd800) {
            i++;
            let c2 = str.charCodeAt(i);

            if (i >= str.length || (c2 & 0xfc00) !== 0xdc00) {
                throw new Error('invalid utf-8 string');
            }

            // Surrogate Pair
            c = 0x10000 + ((c & 0x03ff) << 10) + (c2 & 0x03ff);
            result.push((c >> 18) | 0xf0);
            result.push(((c >> 12) & 0x3f) | 0x80);
            result.push(((c >> 6) & 0x3f) | 0x80);
            result.push((c & 0x3f) | 0x80);

        } else {
            result.push((c >> 12) | 0xe0);
            result.push(((c >> 6) & 0x3f) | 0x80);
            result.push((c & 0x3f) | 0x80);
        }
    }

    return arrayify(result);
};


// http://stackoverflow.com/questions/13356493/decode-utf-8-with-javascript#13691499
export function toUtf8String(bytes: Arrayish, ignoreErrors?: boolean): string {
    bytes = arrayify(bytes);

    let result = '';
    let i = 0;

    // Invalid bytes are ignored
    while(i < bytes.length) {

        var c = bytes[i++];
        // 0xxx xxxx
        if (c >> 7 === 0) {
            result += String.fromCharCode(c);
            continue;
        }

        // Multibyte; how many bytes left for this character?
        let extraLength = null;
        let overlongMask = null;

        // 110x xxxx 10xx xxxx
        if ((c & 0xe0) === 0xc0) {
            extraLength = 1;
            overlongMask = 0x7f;

        // 1110 xxxx 10xx xxxx 10xx xxxx
        } else if ((c & 0xf0) === 0xe0) {
            extraLength = 2;
            overlongMask = 0x7ff;

        // 1111 0xxx 10xx xxxx 10xx xxxx 10xx xxxx
        } else if ((c & 0xf8) === 0xf0) {
            extraLength = 3;
            overlongMask = 0xffff;

        } else {
            if (!ignoreErrors) {
                if ((c & 0xc0) === 0x80) {
                    throw new Error('invalid utf8 byte sequence; unexpected continuation byte');
                }
                throw new Error('invalid utf8 byte sequence; invalid prefix');
            }
            continue;
        }

        // Do we have enough bytes in our data?
        if (i + extraLength > bytes.length) {
            if (!ignoreErrors) { throw new Error('invalid utf8 byte sequence; too short'); }

            // If there is an invalid unprocessed byte, skip continuation bytes
            for (; i < bytes.length; i++) {
                if (bytes[i] >> 6 !== 0x02) { break; }
            }

            continue;
        }

        // Remove the length prefix from the char
        let res = c & ((1 << (8 - extraLength - 1)) - 1);

        for (let j = 0; j < extraLength; j++) {
            var nextChar = bytes[i];

            // Invalid continuation byte
            if ((nextChar & 0xc0) != 0x80) {
                res = null;
                break;
            };

            res = (res << 6) | (nextChar & 0x3f);
            i++;
        }

        if (res === null) {
            if (!ignoreErrors) { throw new Error('invalid utf8 byte sequence; invalid continuation byte'); }
            continue;
        }

        // Check for overlong seuences (more bytes than needed)
        if (res <= overlongMask) {
            if (!ignoreErrors) { throw new Error('invalid utf8 byte sequence; overlong'); }
            continue;
        }

        // Maximum code point
        if (res > 0x10ffff) {
            if (!ignoreErrors) { throw new Error('invalid utf8 byte sequence; out-of-range'); }
            continue;
        }

        // Reserved for UTF-16 surrogate halves
        if (res >= 0xd800 && res <= 0xdfff) {
            if (!ignoreErrors) { throw new Error('invalid utf8 byte sequence; utf-16 surrogate'); }
            continue;
        }

        if (res <= 0xffff) {
            result += String.fromCharCode(res);
            continue;
        }

        res -= 0x10000;
        result += String.fromCharCode(((res >> 10) & 0x3ff) + 0xd800, (res & 0x3ff) + 0xdc00);
    }

    return result;
}

export function formatBytes32String(text: string): string {

    // Get the bytes
    let bytes = toUtf8Bytes(text);

    // Check we have room for null-termination
    if (bytes.length > 31) { throw new Error('bytes32 string must be less than 32 bytes'); }

    // Zero-pad (implicitly null-terminates)
    return hexlify(concat([ bytes, HashZero ]).slice(0, 32));
}

export function parseBytes32String(bytes: Arrayish): string {
    let data = arrayify(bytes);

    // Must be 32 bytes with a null-termination
    if (data.length !== 32) { throw new Error('invalid bytes32 - not 32 bytes long'); }
    if (data[31] !== 0) { throw new Error('invalid bytes32 string - no null terminator'); }

    // Find the null termination
    let length = 31;
    while (data[length - 1] === 0) { length--; }

    // Determine the string value
    return toUtf8String(data.slice(0, length));
}