'use strict';

const iconv = require('iconv-lite');
const encodingJapanese = require('encoding-japanese');
const charsets = require('./charsets');

/**
 * Character set encoding and decoding functions
 */
const charset = (module.exports = {
    /**
     * Encodes an unicode string into an Buffer object as UTF-8
     *
     * We force UTF-8 here, no strange encodings allowed.
     *
     * @param {String} str String to be encoded
     * @return {Buffer} UTF-8 encoded typed array
     */
    encode(str) {
        return Buffer.from(str, 'utf-8');
    },

    /**
     * Decodes a string from Buffer to an unicode string using specified encoding
     * NB! Throws if unknown charset is used
     *
     * @param {Buffer} buf Binary data to be decoded
     * @param {String} [fromCharset='UTF-8'] Binary data is decoded into string using this charset
     * @param {Function} [Iconv] node-iconv function
     * @return {String} Decded string
     */
    decode(buf, fromCharset, Iconv) {
        fromCharset = charset.normalizeCharset(fromCharset || 'UTF-8');

        if (/^(us-)?ascii|utf-8|7bit$/i.test(fromCharset)) {
            return buf.toString('utf-8');
        }

        try {
            if (typeof Iconv === 'function') {
                let decoder = new Iconv(fromCharset, 'UTF-8');
                return decoder.convert(buf).toString();
            }

            if (/^jis|^iso-?2022-?jp|^EUCJP/i.test(fromCharset)) {
                if (typeof buf === 'string') {
                    buf = Buffer.from(buf);
                }
                try {
                    let output = encodingJapanese.convert(buf, {
                        to: 'UNICODE',
                        from: fromCharset,
                        type: 'string'
                    });
                    if (typeof output === 'string') {
                        output = Buffer.from(output);
                    }
                    return output;
                } catch (err) {
                    // ignore, defaults to iconv-lite on error
                }
            }

            return iconv.decode(buf, fromCharset);
        } catch (err) {
            // enforce utf-8, data loss might occur
            return buf.toString();
        }
    },

    /**
     * Convert a string from specific encoding to UTF-8 Buffer
     *
     * @param {String|Buffer} str String to be encoded
     * @param {String} [fromCharset='UTF-8'] Source encoding for the string
     * @return {Buffer} UTF-8 encoded typed array
     */
    convert(data, fromCharset, Iconv) {
        fromCharset = charset.normalizeCharset(fromCharset || 'UTF-8');

        let bufString;

        if (typeof data !== 'string') {
            if (/^(us-)?ascii|utf-8|7bit$/i.test(fromCharset)) {
                return data;
            }

            bufString = charset.decode(data, fromCharset, Iconv);
            return charset.encode(bufString);
        }
        return charset.encode(data);
    },

    /**
     * Converts well known invalid character set names to proper names.
     * eg. win-1257 will be converted to WINDOWS-1257
     *
     * @param {String} charset Charset name to convert
     * @return {String} Canoninicalized charset name
     */
    normalizeCharset(charset) {
        charset = charset.toLowerCase().trim();

        // first pass
        if (charsets.hasOwnProperty(charset) && charsets[charset]) {
            return charsets[charset];
        }

        charset = charset
            .replace(/^utf[-_]?(\d+)/, 'utf-$1')
            .replace(/^(?:us[-_]?)ascii/, 'windows-1252')
            .replace(/^win(?:dows)?[-_]?(\d+)/, 'windows-$1')
            .replace(/^(?:latin|iso[-_]?8859)?[-_]?(\d+)/, 'iso-8859-$1')
            .replace(/^l[-_]?(\d+)/, 'iso-8859-$1');

        // updated pass
        if (charsets.hasOwnProperty(charset) && charsets[charset]) {
            return charsets[charset];
        }

        return charset.toUpperCase();
    }
});