/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.kylin.metadata.filter.function;

/**
 * From Calcite
 *
 * Utilities for converting SQL {@code LIKE} and {@code SIMILAR} operators
 * to regular expressions.
 */
public class Like {
    private static final String JAVA_REGEX_SPECIALS = "[]()|^-+*?{}$\\";
    private static final String SQL_SIMILAR_SPECIALS = "[]()|^-+*_%?{}";
    private static final String[] REG_CHAR_CLASSES = { "[:ALPHA:]", "\\p{Alpha}", "[:alpha:]", "\\p{Alpha}",
            "[:UPPER:]", "\\p{Upper}", "[:upper:]", "\\p{Upper}", "[:LOWER:]", "\\p{Lower}", "[:lower:]", "\\p{Lower}",
            "[:DIGIT:]", "\\d", "[:digit:]", "\\d", "[:SPACE:]", " ", "[:space:]", " ", "[:WHITESPACE:]", "\\s",
            "[:whitespace:]", "\\s", "[:ALNUM:]", "\\p{Alnum}", "[:alnum:]", "\\p{Alnum}" };

    private Like() {
    }

    /**
     * Translates a SQL LIKE pattern to Java regex pattern, with optional
     * escape string.
     */
    static String sqlToRegexLike(String sqlPattern, CharSequence escapeStr) {
        final char escapeChar;
        if (escapeStr != null) {
            if (escapeStr.length() != 1) {
                throw invalidEscapeCharacter(escapeStr.toString());
            }
            escapeChar = escapeStr.charAt(0);
        } else {
            escapeChar = 0;
        }
        return sqlToRegexLike(sqlPattern, escapeChar);
    }

    /**
     * Translates a SQL LIKE pattern to Java regex pattern.
     */
    static String sqlToRegexLike(String sqlPattern, char escapeChar) {
        int i;
        final int len = sqlPattern.length();
        final StringBuilder javaPattern = new StringBuilder(len + len);
        for (i = 0; i < len; i++) {
            char c = sqlPattern.charAt(i);
            if (JAVA_REGEX_SPECIALS.indexOf(c) >= 0) {
                javaPattern.append('\\');
            }
            if (c == escapeChar) {
                if (i == (sqlPattern.length() - 1)) {
                    throw invalidEscapeSequence(sqlPattern, i);
                }
                char nextChar = sqlPattern.charAt(i + 1);
                if ((nextChar == '_') || (nextChar == '%') || (nextChar == escapeChar)) {
                    javaPattern.append(nextChar);
                    i++;
                } else {
                    throw invalidEscapeSequence(sqlPattern, i);
                }
            } else if (c == '_') {
                javaPattern.append('.');
            } else if (c == '%') {
                javaPattern.append(".");
                javaPattern.append('*');
            } else {
                javaPattern.append(c);
            }
        }
        return javaPattern.toString();
    }

    private static RuntimeException invalidEscapeCharacter(String s) {
        return new RuntimeException("Invalid escape character '" + s + "'");
    }

    private static RuntimeException invalidEscapeSequence(String s, int i) {
        return new RuntimeException("Invalid escape sequence '" + s + "', " + i);
    }

    private static void similarEscapeRuleChecking(String sqlPattern, char escapeChar) {
        if (escapeChar == 0) {
            return;
        }
        if (SQL_SIMILAR_SPECIALS.indexOf(escapeChar) >= 0) {
            // The the escape character is a special character
            // SQL 2003 Part 2 Section 8.6 General Rule 3.b
            for (int i = 0; i < sqlPattern.length(); i++) {
                if (sqlPattern.charAt(i) == escapeChar) {
                    if (i == (sqlPattern.length() - 1)) {
                        throw invalidEscapeSequence(sqlPattern, i);
                    }
                    char c = sqlPattern.charAt(i + 1);
                    if ((SQL_SIMILAR_SPECIALS.indexOf(c) < 0) && (c != escapeChar)) {
                        throw invalidEscapeSequence(sqlPattern, i);
                    }
                }
            }
        }

        // SQL 2003 Part 2 Section 8.6 General Rule 3.c
        if (escapeChar == ':') {
            int position;
            position = sqlPattern.indexOf("[:");
            if (position >= 0) {
                position = sqlPattern.indexOf(":]");
            }
            if (position < 0) {
                throw invalidEscapeSequence(sqlPattern, position);
            }
        }
    }

    private static RuntimeException invalidRegularExpression(String pattern, int i) {
        return new RuntimeException("Invalid regular expression '" + pattern + "'");
    }

    private static int sqlSimilarRewriteCharEnumeration(String sqlPattern, StringBuilder javaPattern, int pos,
            char escapeChar) {
        int i;
        for (i = pos + 1; i < sqlPattern.length(); i++) {
            char c = sqlPattern.charAt(i);
            if (c == ']') {
                return i - 1;
            } else if (c == escapeChar) {
                i++;
                char nextChar = sqlPattern.charAt(i);
                if (SQL_SIMILAR_SPECIALS.indexOf(nextChar) >= 0) {
                    if (JAVA_REGEX_SPECIALS.indexOf(nextChar) >= 0) {
                        javaPattern.append('\\');
                    }
                    javaPattern.append(nextChar);
                } else if (escapeChar == nextChar) {
                    javaPattern.append(nextChar);
                } else {
                    throw invalidRegularExpression(sqlPattern, i);
                }
            } else if (c == '-') {
                javaPattern.append('-');
            } else if (c == '^') {
                javaPattern.append('^');
            } else if (sqlPattern.startsWith("[:", i)) {
                int numOfRegCharSets = REG_CHAR_CLASSES.length / 2;
                boolean found = false;
                for (int j = 0; j < numOfRegCharSets; j++) {
                    if (sqlPattern.startsWith(REG_CHAR_CLASSES[j + j], i)) {
                        javaPattern.append(REG_CHAR_CLASSES[j + j + 1]);

                        i += REG_CHAR_CLASSES[j + j].length() - 1;
                        found = true;
                        break;
                    }
                }
                if (!found) {
                    throw invalidRegularExpression(sqlPattern, i);
                }
            } else if (SQL_SIMILAR_SPECIALS.indexOf(c) >= 0) {
                throw invalidRegularExpression(sqlPattern, i);
            } else {
                javaPattern.append(c);
            }
        }
        return i - 1;
    }

    /**
     * Translates a SQL SIMILAR pattern to Java regex pattern, with optional
     * escape string.
     */
    static String sqlToRegexSimilar(String sqlPattern, CharSequence escapeStr) {
        final char escapeChar;
        if (escapeStr != null) {
            if (escapeStr.length() != 1) {
                throw invalidEscapeCharacter(escapeStr.toString());
            }
            escapeChar = escapeStr.charAt(0);
        } else {
            escapeChar = 0;
        }
        return sqlToRegexSimilar(sqlPattern, escapeChar);
    }

    /**
     * Translates SQL SIMILAR pattern to Java regex pattern.
     */
    static String sqlToRegexSimilar(String sqlPattern, char escapeChar) {
        similarEscapeRuleChecking(sqlPattern, escapeChar);

        boolean insideCharacterEnumeration = false;
        final StringBuilder javaPattern = new StringBuilder(sqlPattern.length() * 2);
        final int len = sqlPattern.length();
        for (int i = 0; i < len; i++) {
            char c = sqlPattern.charAt(i);
            if (c == escapeChar) {
                if (i == (len - 1)) {
                    // It should never reach here after the escape rule
                    // checking.
                    throw invalidEscapeSequence(sqlPattern, i);
                }
                char nextChar = sqlPattern.charAt(i + 1);
                if (SQL_SIMILAR_SPECIALS.indexOf(nextChar) >= 0) {
                    // special character, use \ to replace the escape char.
                    if (JAVA_REGEX_SPECIALS.indexOf(nextChar) >= 0) {
                        javaPattern.append('\\');
                    }
                    javaPattern.append(nextChar);
                } else if (nextChar == escapeChar) {
                    javaPattern.append(nextChar);
                } else {
                    // It should never reach here after the escape rule
                    // checking.
                    throw invalidEscapeSequence(sqlPattern, i);
                }
                i++; // we already process the next char.
            } else {
                switch (c) {
                case '_':
                    javaPattern.append('.');
                    break;
                case '%':
                    javaPattern.append('.');
                    javaPattern.append('*');
                    break;
                case '[':
                    javaPattern.append('[');
                    insideCharacterEnumeration = true;
                    i = sqlSimilarRewriteCharEnumeration(sqlPattern, javaPattern, i, escapeChar);
                    break;
                case ']':
                    if (!insideCharacterEnumeration) {
                        throw invalidRegularExpression(sqlPattern, i);
                    }
                    insideCharacterEnumeration = false;
                    javaPattern.append(']');
                    break;
                case '\\':
                    javaPattern.append("\\\\");
                    break;
                case '$':

                    // $ is special character in java regex, but regular in
                    // SQL regex.
                    javaPattern.append("\\$");
                    break;
                default:
                    javaPattern.append(c);
                }
            }
        }
        if (insideCharacterEnumeration) {
            throw invalidRegularExpression(sqlPattern, len);
        }

        return javaPattern.toString();
    }
}

// End Like.java
