/*
 * DavMail POP/IMAP/SMTP/CalDav/LDAP Exchange Gateway
 * Copyright (C) 2009  Mickael Guessant
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 */
package davmail.util;

import org.apache.commons.codec.DecoderException;
import org.apache.commons.codec.binary.Base64;
import org.apache.commons.codec.binary.Hex;

import java.nio.charset.StandardCharsets;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.List;
import java.util.Set;
import java.util.regex.Pattern;

/**
 * Various string handling methods
 */
public final class StringUtil {
    private StringUtil() {
    }

    /**
     * Return the sub string between startDelimiter and endDelimiter or null.
     *
     * @param value          String value
     * @param startDelimiter start delimiter
     * @param endDelimiter   end delimiter
     * @return token value
     */
    public static String getToken(String value, String startDelimiter, String endDelimiter) {
        String token = null;
        if (value != null) {
            int startIndex = value.indexOf(startDelimiter);
            if (startIndex >= 0) {
                startIndex += startDelimiter.length();
                int endIndex = value.indexOf(endDelimiter, startIndex);
                if (endIndex >= 0) {
                    token = value.substring(startIndex, endIndex);
                }
            }
        }
        return token;
    }

    /**
     * Return the sub string between startDelimiter and endDelimiter or null,
     * look for last token in string.
     *
     * @param value          String value
     * @param startDelimiter start delimiter
     * @param endDelimiter   end delimiter
     * @return token value
     */
    public static String getLastToken(String value, String startDelimiter, String endDelimiter) {
        String token = null;
        if (value != null) {
            int startIndex = value.lastIndexOf(startDelimiter);
            if (startIndex >= 0) {
                startIndex += startDelimiter.length();
                int endIndex = value.indexOf(endDelimiter, startIndex);
                if (endIndex >= 0) {
                    token = value.substring(startIndex, endIndex);
                }
            }
        }
        return token;
    }

    /**
     * Return the sub string between startDelimiter and endDelimiter with newToken.
     *
     * @param value          String value
     * @param startDelimiter start delimiter
     * @param endDelimiter   end delimiter
     * @param newToken       new token value
     * @return token value
     */
    public static String replaceToken(String value, String startDelimiter, String endDelimiter, String newToken) {
        String result = null;
        if (value != null) {
            int startIndex = value.indexOf(startDelimiter);
            if (startIndex >= 0) {
                startIndex += startDelimiter.length();
                int endIndex = value.indexOf(endDelimiter, startIndex);
                if (endIndex >= 0) {
                    result = value.substring(0, startIndex) + newToken + value.substring(endIndex);
                }
            }
        }
        return result;
    }

    /**
     * Join values with given separator.
     *
     * @param values    value set
     * @param separator separator
     * @return joined values
     */
    public static String join(Set<String> values, String separator) {
        if (values != null && !values.isEmpty()) {
            StringBuilder result = new StringBuilder();
            for (String value : values) {
                if (result.length() > 0) {
                    result.append(separator);
                }
                result.append(value);
            }
            return result.toString();
        } else {
            return null;
        }
    }

    static class PatternMap {
        protected String match;
        protected String value;
        protected Pattern pattern;

        protected PatternMap(String match, String value) {
            this.match = match;
            this.value = value;
            pattern = Pattern.compile(match);
        }

        protected PatternMap(String match, String escapedMatch, String value) {
            this.match = match;
            this.value = value;
            pattern = Pattern.compile(escapedMatch);
        }

        protected PatternMap(String match, Pattern pattern, String value) {
            this.match = match;
            this.value = value;
            this.pattern = pattern;
        }

        protected String replaceAll(String string) {
            if (string != null && string.contains(match)) {
                return pattern.matcher(string).replaceAll(value);
            } else {
                return string;
            }
        }
    }

    private static final Pattern AMP_PATTERN = Pattern.compile("&");
    private static final Pattern PLUS_PATTERN = Pattern.compile("\\+");

    private static final Pattern QUOTE_PATTERN = Pattern.compile("\"");
    private static final Pattern CR_PATTERN = Pattern.compile("\r");
    private static final Pattern LF_PATTERN = Pattern.compile("\n");

    private static final List<PatternMap> URLENCODED_PATTERNS = new ArrayList<>();
    static {
        URLENCODED_PATTERNS.add(new PatternMap(String.valueOf((char) 0xF8FF), "_xF8FF_"));
        URLENCODED_PATTERNS.add(new PatternMap("%26", "&"));
        URLENCODED_PATTERNS.add(new PatternMap("%2B", "+"));
        URLENCODED_PATTERNS.add(new PatternMap("%3A", ":"));
        URLENCODED_PATTERNS.add(new PatternMap("%3B", ";"));
        URLENCODED_PATTERNS.add(new PatternMap("%3C", "<"));
        URLENCODED_PATTERNS.add(new PatternMap("%3E", ">"));
        URLENCODED_PATTERNS.add(new PatternMap("%22", "\""));
        URLENCODED_PATTERNS.add(new PatternMap("%23", "#"));
        URLENCODED_PATTERNS.add(new PatternMap("%2A", "*"));
        URLENCODED_PATTERNS.add(new PatternMap("%7C", "|"));
        URLENCODED_PATTERNS.add(new PatternMap("%3F", "?"));
        URLENCODED_PATTERNS.add(new PatternMap("%7E", "~"));

        // CRLF is replaced with LF in response
        URLENCODED_PATTERNS.add(new PatternMap("\n", "_x000D__x000A_"));

        // last replace %
        URLENCODED_PATTERNS.add(new PatternMap("%25", "%"));
    }

    private static final List<PatternMap> URLENCODE_PATTERNS = new ArrayList<>();
    static {
        // first replace %
        URLENCODE_PATTERNS.add(new PatternMap("%", "%25"));

        URLENCODE_PATTERNS.add(new PatternMap("_xF8FF_", String.valueOf((char) 0xF8FF)));
        URLENCODE_PATTERNS.add(new PatternMap("&", AMP_PATTERN, "%26"));
        URLENCODE_PATTERNS.add(new PatternMap("+", PLUS_PATTERN, "%2B"));
        URLENCODE_PATTERNS.add(new PatternMap(":", "%3A"));
        URLENCODE_PATTERNS.add(new PatternMap(";", "%3B"));
        URLENCODE_PATTERNS.add(new PatternMap("<", "%3C"));
        URLENCODE_PATTERNS.add(new PatternMap(">", "%3E"));
        URLENCODE_PATTERNS.add(new PatternMap("\"", "%22"));
        URLENCODE_PATTERNS.add(new PatternMap("#", "%23"));
        URLENCODE_PATTERNS.add(new PatternMap("~", "%7E"));
        URLENCODE_PATTERNS.add(new PatternMap("*", "\\*", "%2A"));
        URLENCODE_PATTERNS.add(new PatternMap("|", "\\|", "%7C"));
        URLENCODE_PATTERNS.add(new PatternMap("?", "\\?", "%3F"));

        URLENCODE_PATTERNS.add(new PatternMap("_x000D__x000A_", "\r\n"));

    }

    private static final List<PatternMap> XML_DECODE_PATTERNS = new ArrayList<>();
    static {
        XML_DECODE_PATTERNS.add(new PatternMap("&amp;", "&"));
        XML_DECODE_PATTERNS.add(new PatternMap("&lt;", "<"));
        XML_DECODE_PATTERNS.add(new PatternMap("&gt;", ">"));
    }

    private static final List<PatternMap> XML_ENCODE_PATTERNS = new ArrayList<>();
    static {
        XML_ENCODE_PATTERNS.add(new PatternMap("&", AMP_PATTERN, "&amp;"));
        XML_ENCODE_PATTERNS.add(new PatternMap("<", "&lt;"));
        XML_ENCODE_PATTERNS.add(new PatternMap(">", "&gt;"));
    }

    private static final Pattern SLASH_PATTERN = Pattern.compile("/");
    private static final Pattern UNDERSCORE_PATTERN = Pattern.compile("_");
    private static final Pattern DASH_PATTERN = Pattern.compile("-");

    // WebDav search parameter encode
    private static final Pattern APOS_PATTERN = Pattern.compile("'");

    /**
     * Xml encode content.
     *
     * @param name decoded name
     * @return name encoded name
     */
    public static String xmlEncode(String name) {
        String result = name;
        if (result != null) {
            for (PatternMap patternMap : XML_ENCODE_PATTERNS) {
                result = patternMap.replaceAll(result);
            }
        }
        return result;
    }

    /**
     * Xml encode inside attribute.
     *
     * @param name decoded name
     * @return name encoded name
     */
    public static String xmlEncodeAttribute(String name) {
        String result = xmlEncode(name);
        if (result != null) {
            if (result.indexOf('"') >= 0) {
                result = QUOTE_PATTERN.matcher(result).replaceAll("&#x22;");
            }
            if (result.indexOf('\r') >= 0) {
                result = CR_PATTERN.matcher(result).replaceAll("&#x0D;");
            }
            if (result.indexOf('\n') >= 0) {
                result = LF_PATTERN.matcher(result).replaceAll("&#x0A;");
            }
        }
        return result;
    }

    /**
     * Need to decode XML for iCal
     *
     * @param name encoded name
     * @return name decoded name
     */
    public static String xmlDecode(String name) {
        String result = name;
        if (result != null) {
            for (PatternMap patternMap : XML_DECODE_PATTERNS) {
                result = patternMap.replaceAll(result);
            }
        }
        return result;
    }

    /**
     * Convert base64 value to hex.
     *
     * @param value base64 value
     * @return hex value
     */
    @SuppressWarnings("unused")
    public static String base64ToHex(String value) {
        String hexValue = null;
        if (value != null) {
            hexValue = new String(Hex.encodeHex(Base64.decodeBase64(value.getBytes(StandardCharsets.UTF_8))));
        }
        return hexValue;
    }

    /**
     * Convert hex value to base64.
     *
     * @param value hex value
     * @return base64 value
     * @throws DecoderException on error
     */
    @SuppressWarnings("unused")
    public static String hexToBase64(String value) throws DecoderException {
        String base64Value = null;
        if (value != null) {
            base64Value = new String(Base64.encodeBase64(Hex.decodeHex(value.toCharArray())), StandardCharsets.UTF_8);
        }
        return base64Value;
    }

    /**
     * Encode item name to get actual value stored in urlcompname MAPI property.
     *
     * @param value decoded value
     * @return urlcompname encoded value
     */
    public static String encodeUrlcompname(String value) {
        String result = value;
        if (result != null) {
            for (PatternMap patternMap : URLENCODE_PATTERNS) {
                result = patternMap.replaceAll(result);
            }
        }
        return result;
    }

    /**
     * Decode urlcompname to get item name.
     *
     * @param urlcompname encoded value
     * @return decoded value
     */
    public static String decodeUrlcompname(String urlcompname) {
        String result = urlcompname;
        if (result != null) {
            for (PatternMap patternMap : URLENCODED_PATTERNS) {
                result = patternMap.replaceAll(result);
            }
        }
        return result;
    }

    /**
     * Urlencode plus sign in encoded href.
     * '+' is decoded as ' ' by URIUtil.decode, the workaround is to force urlencoding to '%2B' first
     *
     * @param value encoded href
     * @return encoded href
     */
    public static String encodePlusSign(String value) {
        String result = value;
        if (result.indexOf('+') >= 0) {
            result = PLUS_PATTERN.matcher(result).replaceAll("%2B");
        }
        return result;
    }

    /**
     * Encode EWS base64 itemId to url compatible value.
     *
     * @param value base64 value
     * @return url compatible value
     */
    public static String base64ToUrl(String value) {
        String result = value;
        if (result != null) {
            if (result.indexOf('+') >= 0) {
                result = PLUS_PATTERN.matcher(result).replaceAll("-");
            }
            if (result.indexOf('/') >= 0) {
                result = SLASH_PATTERN.matcher(result).replaceAll("_");
            }
        }
        return result;
    }

    /**
     * Encode EWS url compatible itemId back to base64 value.
     *
     * @param value url compatible value
     * @return base64 value
     */
    public static String urlToBase64(String value) {
        String result = value;
        if (result.indexOf('-') >= 0) {
            result = DASH_PATTERN.matcher(result).replaceAll("+");
        }
        if (result.indexOf('_') >= 0) {
            result = UNDERSCORE_PATTERN.matcher(result).replaceAll("/");
        }
        return result;
    }

    /**
     * Encode quotes in Dav search parameter.
     *
     * @param value search parameter
     * @return escaped value
     */
    public static String davSearchEncode(String value) {
        return escapeQuotes(value);
    }

    /**
     * Escape quotes for DAV and graph filters.
     * @param value input value
     * @return quoted result
     */
    public static String escapeQuotes(String value) {
        String result = value;
        if (result != null && result.indexOf('\'') >= 0) {
            result = APOS_PATTERN.matcher(result).replaceAll("''");
        }
        return result;
    }

    /**
     * Backslash escape double guotes in provided string.
     *
     * @param value input string
     * @return escaped string
     */
    public static String escapeDoubleQuotes(String value) {
        String result = value;
        if (result != null && result.indexOf('"') >= 0) {
            result = QUOTE_PATTERN.matcher(result).replaceAll("\\\\\"");
        }
        return result;
    }

    /**
     * Get allDay date value from Zulu timestamp.
     *
     * @param value Zulu datetime
     * @return yyyyMMdd allDay date value
     */
    public static String convertZuluDateTimeToAllDay(String value) {
        String result = value;
        if (value != null && value.length() != 8) {
            // try to convert datetime value to date value
            try {
                Calendar calendar = Calendar.getInstance();
                SimpleDateFormat dateParser = new SimpleDateFormat("yyyyMMdd'T'HHmmss'Z'");
                calendar.setTime(dateParser.parse(value));
                calendar.add(Calendar.HOUR_OF_DAY, 12);
                SimpleDateFormat dateFormatter = new SimpleDateFormat("yyyyMMdd");
                result = dateFormatter.format(calendar.getTime());
            } catch (ParseException e) {
                // ignore
            }
        }
        return result;
    }

    /**
     * Takes a quoted string according to IMAP rfc 3501 and returns its intrinsic (unquoted) string value.
     *
     * <p>RFC 3501 defines a quoted string in its ABNF as follows:</p>
     * <pre>
     *     quoted          = DQUOTE *QUOTED-CHAR DQUOTE
     *     DQUOTE          = %x22
     *                       ; " (Double Quote)
     *     QUOTED-CHAR     = &lt;any TEXT-CHAR except quoted-specials&gt; /
     *                       "\" quoted-specials / UTF8-2 / UTF8-3 / UTF8-4
     *     TEXT-CHAR       = &lt;any CHAR except CR and LF&gt;
     *     quoted-specials = DQUOTE / "\"
     * </pre>
     *
     * @param quoted the quoted string or null
     * @return the unquoted string, or null if-and-only-if `quoted` was null
     * @throws IllegalArgumentException when the given quoted string is not valid
     */
    public static String parseQuotedImapString(String quoted) throws ParseException {
        if (null == quoted) {
            return null;
        }
        char[] quotedChars = quoted.toCharArray();
        if (quotedChars.length < 2) {
            // not a quoted string. even the empty string is, in it's quoted form, represented as: "\"\""
            // (two double quotes)
            throw new ParseException("Not a valid imap quoted string (too short): " + quoted, 0);
        }
        if ('"' != quotedChars[0]) {
            throw new ParseException("Not a valid imap quoted string (does not start with double quote): " + quoted, 0);
        }
        // the result length is at least by 2 chars shorter than the input length, as at least the two enclosing
        // double quotes are removed.
        char[] resultChars = new char[quotedChars.length - 2];

        // 0 is the index of the first char in resultChars that is the actual result.
        // resultPos is the index of the last byte in resultChars that is the actual result.
        // resultChars MAY have additional bytes (when resultPos + 1 < resultChars.length), that are not part of the result.
        int resultPos = 0;
        // a very mechanical approach, looking at one character at a time
        boolean backslashMode = false;
        // iterate ignoring starting and ending quotes
        for (int i = 1; i < quotedChars.length - 1; i++) {
            if (backslashMode) {
                if ('\\' == quotedChars[i] || '"' == quotedChars[i]) {
                    resultChars[resultPos++] = quotedChars[i];
                    backslashMode = false;
                } else {
                    throw new ParseException("Not a valid imap quoted string "
                            + "(only '\"' and '\\' allowed after '\\') at index " + i + ": " + quoted, i);
                }
            } else {
                if ('\\' == quotedChars[i]) {
                    backslashMode = true;
                } else {
                    resultChars[resultPos++] = quotedChars[i];
                }
            }
        }
        if (backslashMode) {
            throw new ParseException("Not a valid imap quoted string "
                    + "(outer ending quote is backslashed): " + quoted, quotedChars.length - 1);
        }
        if ('"' != quotedChars[quotedChars.length - 1]) {
            throw new ParseException("Not a valid imap quoted string "
                    + "(does not end with double quotes): " + quoted, quotedChars.length - 1);
        }
        return new String(resultChars, 0, resultPos);
    }

    /**
     * Remove quotes if present on value.
     *
     * @param value input value
     * @return unquoted string
     */
    public static String removeQuotes(String value) {
        String result = value;
        if (result != null) {
            if (result.startsWith("\"") || result.startsWith("{") || result.startsWith("(")) {
                result = result.substring(1);
            }
            if (result.endsWith("\"") || result.endsWith("}") || result.endsWith(")")) {
                result = result.substring(0, result.length() - 1);
            }
        }
        return result;
    }

    /**
     * Decode the folder name with _xF8FF_ or _x003E_ characters.
     * @param folderName encoded folder name
     * @return decoded folder name
     */
    public static String decodeFolderName(String folderName) {
        if (folderName.contains("_xF8FF_")) {
            return folderName.replace("_xF8FF_", "/");
        }
        if (folderName.contains("_x003E_")) {
            return folderName.replace("_x003E_", ">");
        }
        return folderName;
    }

    /**
     * folderName may contain / or > characters, encode them.
     * @param folderName folder name to encode
     * @return encoded folder name
     */
    public static String encodeFolderName(String folderName) {
        if (folderName.contains("/")) {
            folderName = folderName.replace("/", "_xF8FF_");
        }
        if (folderName.contains(">")) {
            folderName = folderName.replace(">", "_x003E_");
        }
        return folderName;
    }

}
