/* eslint no-control-regex:0 */

'use strict';

const base64 = require('../base64');
const qp = require('../qp');
const mimeTypes = require('./mime-types');

module.exports = {
    /**
     * Checks if a value is plaintext string (uses only printable 7bit chars)
     *
     * @param {String} value String to be tested
     * @returns {Boolean} true if it is a plaintext string
     */
    isPlainText(value) {
        if (typeof value !== 'string' || /[\x00-\x08\x0b\x0c\x0e-\x1f\u0080-\uFFFF]/.test(value)) {
            return false;
        } else {
            return true;
        }
    },

    /**
     * Checks if a multi line string containes lines longer than the selected value.
     *
     * Useful when detecting if a mail message needs any processing at all –
     * if only plaintext characters are used and lines are short, then there is
     * no need to encode the values in any way. If the value is plaintext but has
     * longer lines then allowed, then use format=flowed
     *
     * @param {Number} lineLength Max line length to check for
     * @returns {Boolean} Returns true if there is at least one line longer than lineLength chars
     */
    hasLongerLines(str, lineLength) {
        if (str.length > 128 * 1024) {
            // do not test strings longer than 128kB
            return true;
        }
        return new RegExp('^.{' + (lineLength + 1) + ',}', 'm').test(str);
    },

    /**
     * Encodes a string or an Buffer to an UTF-8 MIME Word (rfc2047)
     *
     * @param {String|Buffer} data String to be encoded
     * @param {String} mimeWordEncoding='Q' Encoding for the mime word, either Q or B
     * @param {Number} [maxLength=0] If set, split mime words into several chunks if needed
     * @return {String} Single or several mime words joined together
     */
    encodeWord(data, mimeWordEncoding, maxLength) {
        mimeWordEncoding = (mimeWordEncoding || 'Q')
            .toString()
            .toUpperCase()
            .trim()
            .charAt(0);
        maxLength = maxLength || 0;

        let encodedStr;
        let toCharset = 'UTF-8';

        if (maxLength && maxLength > 7 + toCharset.length) {
            maxLength -= 7 + toCharset.length;
        }

        if (mimeWordEncoding === 'Q') {
            // https://tools.ietf.org/html/rfc2047#section-5 rule (3)
            encodedStr = qp.encode(data).replace(/[^a-z0-9!*+\-/=]/gi, chr => {
                let ord = chr
                    .charCodeAt(0)
                    .toString(16)
                    .toUpperCase();
                if (chr === ' ') {
                    return '_';
                } else {
                    return '=' + (ord.length === 1 ? '0' + ord : ord);
                }
            });
        } else if (mimeWordEncoding === 'B') {
            encodedStr = typeof data === 'string' ? data : base64.encode(data);
            maxLength = maxLength ? Math.max(3, (maxLength - maxLength % 4) / 4 * 3) : 0;
        }

        if (maxLength && (mimeWordEncoding !== 'B' ? encodedStr : base64.encode(data)).length > maxLength) {
            if (mimeWordEncoding === 'Q') {
                encodedStr = this.splitMimeEncodedString(encodedStr, maxLength).join('?= =?' + toCharset + '?' + mimeWordEncoding + '?');
            } else {
                // RFC2047 6.3 (2) states that encoded-word must include an integral number of characters, so no chopping unicode sequences
                let parts = [];
                let lpart = '';
                for (let i = 0, len = encodedStr.length; i < len; i++) {
                    let chr = encodedStr.charAt(i);
                    // check if we can add this character to the existing string
                    // without breaking byte length limit
                    if (Buffer.byteLength(lpart + chr) <= maxLength || i === 0) {
                        lpart += chr;
                    } else {
                        // we hit the length limit, so push the existing string and start over
                        parts.push(base64.encode(lpart));
                        lpart = chr;
                    }
                }
                if (lpart) {
                    parts.push(base64.encode(lpart));
                }

                if (parts.length > 1) {
                    encodedStr = parts.join('?= =?' + toCharset + '?' + mimeWordEncoding + '?');
                } else {
                    encodedStr = parts.join('');
                }
            }
        } else if (mimeWordEncoding === 'B') {
            encodedStr = base64.encode(data);
        }

        return '=?' + toCharset + '?' + mimeWordEncoding + '?' + encodedStr + (encodedStr.substr(-2) === '?=' ? '' : '?=');
    },

    /**
     * Finds word sequences with non ascii text and converts these to mime words
     *
     * @param {String} value String to be encoded
     * @param {String} mimeWordEncoding='Q' Encoding for the mime word, either Q or B
     * @param {Number} [maxLength=0] If set, split mime words into several chunks if needed
     * @return {String} String with possible mime words
     */
    encodeWords(value, mimeWordEncoding, maxLength) {
        maxLength = maxLength || 0;

        let encodedValue;

        // find first word with a non-printable ascii in it
        let firstMatch = value.match(/(?:^|\s)([^\s]*[\u0080-\uFFFF])/);
        if (!firstMatch) {
            return value;
        }

        // find the last word with a non-printable ascii in it
        let lastMatch = value.match(/([\u0080-\uFFFF][^\s]*)[^\u0080-\uFFFF]*$/);
        if (!lastMatch) {
            // should not happen
            return value;
        }

        let startIndex =
            firstMatch.index +
            (firstMatch[0].match(/[^\s]/) || {
                index: 0
            }).index;
        let endIndex = lastMatch.index + (lastMatch[1] || '').length;

        encodedValue =
            (startIndex ? value.substr(0, startIndex) : '') +
            this.encodeWord(value.substring(startIndex, endIndex), mimeWordEncoding || 'Q', maxLength) +
            (endIndex < value.length ? value.substr(endIndex) : '');

        return encodedValue;
    },

    /**
     * Joins parsed header value together as 'value; param1=value1; param2=value2'
     * PS: We are following RFC 822 for the list of special characters that we need to keep in quotes.
     *      Refer: https://www.w3.org/Protocols/rfc1341/4_Content-Type.html
     * @param {Object} structured Parsed header value
     * @return {String} joined header value
     */
    buildHeaderValue(structured) {
        let paramsArray = [];

        Object.keys(structured.params || {}).forEach(param => {
            // filename might include unicode characters so it is a special case
            // other values probably do not
            let value = structured.params[param];
            if (!this.isPlainText(value) || value.length >= 75) {
                this.buildHeaderParam(param, value, 50).forEach(encodedParam => {
                    if (!/[\s"\\;:/=(),<>@[\]?]|^[-']|'$/.test(encodedParam.value) || encodedParam.key.substr(-1) === '*') {
                        paramsArray.push(encodedParam.key + '=' + encodedParam.value);
                    } else {
                        paramsArray.push(encodedParam.key + '=' + JSON.stringify(encodedParam.value));
                    }
                });
            } else if (/[\s'"\\;:/=(),<>@[\]?]|^-/.test(value)) {
                paramsArray.push(param + '=' + JSON.stringify(value));
            } else {
                paramsArray.push(param + '=' + value);
            }
        });

        return structured.value + (paramsArray.length ? '; ' + paramsArray.join('; ') : '');
    },

    /**
     * Encodes a string or an Buffer to an UTF-8 Parameter Value Continuation encoding (rfc2231)
     * Useful for splitting long parameter values.
     *
     * For example
     *      title="unicode string"
     * becomes
     *     title*0*=utf-8''unicode
     *     title*1*=%20string
     *
     * @param {String|Buffer} data String to be encoded
     * @param {Number} [maxLength=50] Max length for generated chunks
     * @param {String} [fromCharset='UTF-8'] Source sharacter set
     * @return {Array} A list of encoded keys and headers
     */
    buildHeaderParam(key, data, maxLength) {
        let list = [];
        let encodedStr = typeof data === 'string' ? data : (data || '').toString();
        let encodedStrArr;
        let chr, ord;
        let line;
        let startPos = 0;
        let i, len;

        maxLength = maxLength || 50;

        // process ascii only text
        if (this.isPlainText(data)) {
            // check if conversion is even needed
            if (encodedStr.length <= maxLength) {
                return [
                    {
                        key,
                        value: encodedStr
                    }
                ];
            }

            encodedStr = encodedStr.replace(new RegExp('.{' + maxLength + '}', 'g'), str => {
                list.push({
                    line: str
                });
                return '';
            });

            if (encodedStr) {
                list.push({
                    line: encodedStr
                });
            }
        } else {
            if (/[\uD800-\uDBFF]/.test(encodedStr)) {
                // string containts surrogate pairs, so normalize it to an array of bytes
                encodedStrArr = [];
                for (i = 0, len = encodedStr.length; i < len; i++) {
                    chr = encodedStr.charAt(i);
                    ord = chr.charCodeAt(0);
                    if (ord >= 0xd800 && ord <= 0xdbff && i < len - 1) {
                        chr += encodedStr.charAt(i + 1);
                        encodedStrArr.push(chr);
                        i++;
                    } else {
                        encodedStrArr.push(chr);
                    }
                }
                encodedStr = encodedStrArr;
            }

            // first line includes the charset and language info and needs to be encoded
            // even if it does not contain any unicode characters
            line = 'utf-8\'\'';
            let encoded = true;
            startPos = 0;

            // process text with unicode or special chars
            for (i = 0, len = encodedStr.length; i < len; i++) {
                chr = encodedStr[i];

                if (encoded) {
                    chr = this.safeEncodeURIComponent(chr);
                } else {
                    // try to urlencode current char
                    chr = chr === ' ' ? chr : this.safeEncodeURIComponent(chr);
                    // By default it is not required to encode a line, the need
                    // only appears when the string contains unicode or special chars
                    // in this case we start processing the line over and encode all chars
                    if (chr !== encodedStr[i]) {
                        // Check if it is even possible to add the encoded char to the line
                        // If not, there is no reason to use this line, just push it to the list
                        // and start a new line with the char that needs encoding
                        if ((this.safeEncodeURIComponent(line) + chr).length >= maxLength) {
                            list.push({
                                line,
                                encoded
                            });
                            line = '';
                            startPos = i - 1;
                        } else {
                            encoded = true;
                            i = startPos;
                            line = '';
                            continue;
                        }
                    }
                }

                // if the line is already too long, push it to the list and start a new one
                if ((line + chr).length >= maxLength) {
                    list.push({
                        line,
                        encoded
                    });
                    line = chr = encodedStr[i] === ' ' ? ' ' : this.safeEncodeURIComponent(encodedStr[i]);
                    if (chr === encodedStr[i]) {
                        encoded = false;
                        startPos = i - 1;
                    } else {
                        encoded = true;
                    }
                } else {
                    line += chr;
                }
            }

            if (line) {
                list.push({
                    line,
                    encoded
                });
            }
        }

        return list.map((item, i) => ({
            // encoded lines: {name}*{part}*
            // unencoded lines: {name}*{part}
            // if any line needs to be encoded then the first line (part==0) is always encoded
            key: key + '*' + i + (item.encoded ? '*' : ''),
            value: item.line
        }));
    },

    /**
     * Parses a header value with key=value arguments into a structured
     * object.
     *
     *   parseHeaderValue('content-type: text/plain; CHARSET='UTF-8'') ->
     *   {
     *     'value': 'text/plain',
     *     'params': {
     *       'charset': 'UTF-8'
     *     }
     *   }
     *
     * @param {String} str Header value
     * @return {Object} Header value as a parsed structure
     */
    parseHeaderValue(str) {
        let response = {
            value: false,
            params: {}
        };
        let key = false;
        let value = '';
        let type = 'value';
        let quote = false;
        let escaped = false;
        let chr;

        for (let i = 0, len = str.length; i < len; i++) {
            chr = str.charAt(i);
            if (type === 'key') {
                if (chr === '=') {
                    key = value.trim().toLowerCase();
                    type = 'value';
                    value = '';
                    continue;
                }
                value += chr;
            } else {
                if (escaped) {
                    value += chr;
                } else if (chr === '\\') {
                    escaped = true;
                    continue;
                } else if (quote && chr === quote) {
                    quote = false;
                } else if (!quote && chr === '"') {
                    quote = chr;
                } else if (!quote && chr === ';') {
                    if (key === false) {
                        response.value = value.trim();
                    } else {
                        response.params[key] = value.trim();
                    }
                    type = 'key';
                    value = '';
                } else {
                    value += chr;
                }
                escaped = false;
            }
        }

        if (type === 'value') {
            if (key === false) {
                response.value = value.trim();
            } else {
                response.params[key] = value.trim();
            }
        } else if (value.trim()) {
            response.params[value.trim().toLowerCase()] = '';
        }

        // handle parameter value continuations
        // https://tools.ietf.org/html/rfc2231#section-3

        // preprocess values
        Object.keys(response.params).forEach(key => {
            let actualKey, nr, match, value;
            if ((match = key.match(/(\*(\d+)|\*(\d+)\*|\*)$/))) {
                actualKey = key.substr(0, match.index);
                nr = Number(match[2] || match[3]) || 0;

                if (!response.params[actualKey] || typeof response.params[actualKey] !== 'object') {
                    response.params[actualKey] = {
                        charset: false,
                        values: []
                    };
                }

                value = response.params[key];

                if (nr === 0 && match[0].substr(-1) === '*' && (match = value.match(/^([^']*)'[^']*'(.*)$/))) {
                    response.params[actualKey].charset = match[1] || 'iso-8859-1';
                    value = match[2];
                }

                response.params[actualKey].values[nr] = value;

                // remove the old reference
                delete response.params[key];
            }
        });

        // concatenate split rfc2231 strings and convert encoded strings to mime encoded words
        Object.keys(response.params).forEach(key => {
            let value;
            if (response.params[key] && Array.isArray(response.params[key].values)) {
                value = response.params[key].values.map(val => val || '').join('');

                if (response.params[key].charset) {
                    // convert "%AB" to "=?charset?Q?=AB?="
                    response.params[key] =
                        '=?' +
                        response.params[key].charset +
                        '?Q?' +
                        value
                            // fix invalidly encoded chars
                            .replace(/[=?_\s]/g, s => {
                                let c = s.charCodeAt(0).toString(16);
                                if (s === ' ') {
                                    return '_';
                                } else {
                                    return '%' + (c.length < 2 ? '0' : '') + c;
                                }
                            })
                            // change from urlencoding to percent encoding
                            .replace(/%/g, '=') +
                        '?=';
                } else {
                    response.params[key] = value;
                }
            }
        });

        return response;
    },

    /**
     * Returns file extension for a content type string. If no suitable extensions
     * are found, 'bin' is used as the default extension
     *
     * @param {String} mimeType Content type to be checked for
     * @return {String} File extension
     */
    detectExtension: mimeType => mimeTypes.detectExtension(mimeType),

    /**
     * Returns content type for a file extension. If no suitable content types
     * are found, 'application/octet-stream' is used as the default content type
     *
     * @param {String} extension Extension to be checked for
     * @return {String} File extension
     */
    detectMimeType: extension => mimeTypes.detectMimeType(extension),

    /**
     * Folds long lines, useful for folding header lines (afterSpace=false) and
     * flowed text (afterSpace=true)
     *
     * @param {String} str String to be folded
     * @param {Number} [lineLength=76] Maximum length of a line
     * @param {Boolean} afterSpace If true, leave a space in th end of a line
     * @return {String} String with folded lines
     */
    foldLines(str, lineLength, afterSpace) {
        str = (str || '').toString();
        lineLength = lineLength || 76;

        let pos = 0,
            len = str.length,
            result = '',
            line,
            match;

        while (pos < len) {
            line = str.substr(pos, lineLength);
            if (line.length < lineLength) {
                result += line;
                break;
            }
            if ((match = line.match(/^[^\n\r]*(\r?\n|\r)/))) {
                line = match[0];
                result += line;
                pos += line.length;
                continue;
            } else if ((match = line.match(/(\s+)[^\s]*$/)) && match[0].length - (afterSpace ? (match[1] || '').length : 0) < line.length) {
                line = line.substr(0, line.length - (match[0].length - (afterSpace ? (match[1] || '').length : 0)));
            } else if ((match = str.substr(pos + line.length).match(/^[^\s]+(\s*)/))) {
                line = line + match[0].substr(0, match[0].length - (!afterSpace ? (match[1] || '').length : 0));
            }

            result += line;
            pos += line.length;
            if (pos < len) {
                result += '\r\n';
            }
        }

        return result;
    },

    /**
     * Splits a mime encoded string. Needed for dividing mime words into smaller chunks
     *
     * @param {String} str Mime encoded string to be split up
     * @param {Number} maxlen Maximum length of characters for one part (minimum 12)
     * @return {Array} Split string
     */
    splitMimeEncodedString: (str, maxlen) => {
        let curLine,
            match,
            chr,
            done,
            lines = [];

        // require at least 12 symbols to fit possible 4 octet UTF-8 sequences
        maxlen = Math.max(maxlen || 0, 12);

        while (str.length) {
            curLine = str.substr(0, maxlen);

            // move incomplete escaped char back to main
            if ((match = curLine.match(/[=][0-9A-F]?$/i))) {
                curLine = curLine.substr(0, match.index);
            }

            done = false;
            while (!done) {
                done = true;
                // check if not middle of a unicode char sequence
                if ((match = str.substr(curLine.length).match(/^[=]([0-9A-F]{2})/i))) {
                    chr = parseInt(match[1], 16);
                    // invalid sequence, move one char back anc recheck
                    if (chr < 0xc2 && chr > 0x7f) {
                        curLine = curLine.substr(0, curLine.length - 3);
                        done = false;
                    }
                }
            }

            if (curLine.length) {
                lines.push(curLine);
            }
            str = str.substr(curLine.length);
        }

        return lines;
    },

    encodeURICharComponent: chr => {
        let res = '';
        let ord = chr
            .charCodeAt(0)
            .toString(16)
            .toUpperCase();

        if (ord.length % 2) {
            ord = '0' + ord;
        }

        if (ord.length > 2) {
            for (let i = 0, len = ord.length / 2; i < len; i++) {
                res += '%' + ord.substr(i, 2);
            }
        } else {
            res += '%' + ord;
        }

        return res;
    },

    safeEncodeURIComponent(str) {
        str = (str || '').toString();

        try {
            // might throw if we try to encode invalid sequences, eg. partial emoji
            str = encodeURIComponent(str);
        } catch (E) {
            // should never run
            return str.replace(/[^\x00-\x1F *'()<>@,;:\\"[\]?=\u007F-\uFFFF]+/g, '');
        }

        // ensure chars that are not handled by encodeURICompent are converted as well
        return str.replace(/[\x00-\x1F *'()<>@,;:\\"[\]?=\u007F-\uFFFF]/g, chr => this.encodeURICharComponent(chr));
    }
};