/*
 ***** BEGIN LICENSE BLOCK *****
 * Version: EPL 2.0/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Eclipse Public
 * 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.eclipse.org/legal/epl-v20.html
 *
 * Software distributed under the License is distributed on an "AS
 * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * rights and limitations under the License.
 *
 * Copyright (C) 2001-2002 Jan Arne Petersen <jpetersen@uni-bonn.de>
 * Copyright (C) 2007 William N Dortch <bill.dortch@gmail.com>
 * 
 * Alternatively, the contents of this file may be used under the terms of
 * either of the GNU General Public License Version 2 or later (the "GPL"),
 * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the EPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the EPL, the GPL or the LGPL.
 ***** END LICENSE BLOCK *****/

package org.jruby.util;

import org.jcodings.Config;
import org.jcodings.Encoding;
import org.jcodings.IntHolder;
import org.jcodings.unicode.UnicodeCodeRange;
import org.jruby.Ruby;
import org.jruby.RubySymbol;
import org.jruby.runtime.builtin.IRubyObject;

public final class IdUtil {
    /**
     * rb_is_const_id and is_const_id
     */    
    public static boolean isConstant(String id) {
        return Character.isUpperCase(id.charAt(0));
    }

    /**
     * rb_is_class_id and is_class_id
     */    
    public static boolean isClassVariable(String id) {
        return id.length() > 1 && id.charAt(0) == '@' && id.charAt(1) == '@';
    }

    /**
     * rb_is_instance_id and is_instance_id
     */    
    public static boolean isInstanceVariable(String id) {
        return id.length() > 0 && id.charAt(0) == '@' && (id.length() < 2 || id.charAt(1) != '@');
    }
    
    /**
     * rb_is_global_id and is_global_id
     */    
    public static boolean isGlobal(String id) {
        return id.length()>0 && id.charAt(0) == '$';
    }

    public static boolean isPredicate(String id) {
        return id.endsWith("?");
    }
    
    /**
     * We store IR special variables (e.g. %block) in scope and we want reflective Ruby methods to
     * not see these since they are not real variables...they're special.
     */
    public static boolean isSpecial(String id) {
        return id.startsWith("%");
    }

    public static boolean isAttrSet(String id) {
        return id.endsWith("=");
    }

    public static boolean isValidConstantName(String id) {
        char c;
        int len;
        if ((len = id.length()) > 0 && (c = id.charAt(0)) <= 'Z' && c >= 'A') {
            return isNameString(id, 1, len);
        }
        return false;
    }

    public static boolean isValidConstantName(IRubyObject id) {
        if (id instanceof RubySymbol sym) {
            return sym.validConstantName();
        } else {
            return isValidConstantName(id.asJavaString());
        }
    }

    public static boolean isValidInstanceVariableName(String id) {
        int len;
        if ((len = id.length()) > 1 && '@' == id.charAt(0)) {
            if (isInitialCharacter(id.charAt(1))) {
                return isNameString(id, 2, len);
            }
        }
        return false;
    }
    
    public static boolean isValidClassVariableName(String id) {
        int len;
        if ((len = id.length()) > 2 && '@' == id.charAt(0) && '@' == id.charAt(1)) {
            if (isInitialCharacter(id.charAt(2))) {
                return isNameString(id, 3, len);
            }
        }
        return false;
    }

    public static boolean isInitialCharacter(int c) {
        return Character.isAlphabetic(c) || c == '_';
    }

    public static boolean isNameCharacter(char c) {
        return Character.isLetterOrDigit(c) || c == '_';
    }

    public static boolean isNameString(String id, int start, int limit) {
        for (int i = start; i < limit; i++) {
            if (!isNameCharacter(id.charAt(i))) {
                return false;
            }
        }
        return true;
    }

    /**
     * Check the syntax of a Ruby variable, including that it's longer
     * than zero characters, and starts with either an @ or a capital
     * letter.
     */
    public static final boolean isRubyVariable(String name) {
        char c;
        return name.length() > 0 && ((c = name.charAt(0)) == '@' || (c <= 'Z' && c >= 'A'));
    }

    // MRI: rb_sym_constant_char_p
    public static boolean isConstantInitial(ByteList byteList) {
        int c, len;
        int nlen = byteList.realSize();
        Encoding enc = byteList.getEncoding();

        if (nlen < 1) return false;
        int byte0 = byteList.get(0);
        if (byte0 < 128) return enc.isUpper(byte0);

        byte[] bytes = byteList.getUnsafeBytes();
        int begin = byteList.begin();
        int end = begin + nlen;
        c = StringSupport.preciseLength(enc, bytes, begin, end);
        if (!StringSupport.MBCLEN_CHARFOUND_P(c)) return false;
        len = StringSupport.MBCLEN_CHARFOUND_LEN(c);
        c = StringSupport.codePoint(enc, bytes, begin, end);
        if (enc.isUnicode()) {
            if (enc.isUpper(c)) return true;
            if (enc.isLower(c)) return false;
            if (enc.isCodeCType(c, UnicodeCodeRange.TITLECASELETTER.getCType())) return true;
        } else {
            /* fallback to case-folding */
            IntHolder holder = new IntHolder();
            holder.value = begin;
            byte[] fold = new byte[Config.ENC_GET_CASE_FOLD_CODES_MAX_NUM];
            int r = enc.mbcCaseFold(Config.CASE_FOLD, bytes, holder, end, fold);
            if (r > 0 && (r != len || ByteList.memcmp(fold, 0, bytes, begin, r) != 0))
                return true;
        }
        return false;
    }

    // mri: rb_enc_symname_type (minus support for allowed_attrset).
    public static SymbolNameType determineSymbolNameType(Ruby runtime, ByteList data) {
        Encoding encoding = data.getEncoding();

        if (!encoding.isAsciiCompatible()) return SymbolNameType.OTHER;
        if (data.isEmpty()) return SymbolNameType.OTHER;
        int length = data.length();
        SymbolNameType type = SymbolNameType.OTHER;
        boolean idCheck = false;
        int m = 0;
        int e = length - 1; // last available index (MRI is \0)

        switch ((byte) data.get(m)) {
            case 0:
                return SymbolNameType.OTHER;
            case '$':
                type = SymbolNameType.GLOBAL;
                m++;

                if (m < e && isSpecialGlobalName((byte) data.get(m))) return type;

                idCheck = true;
                break;
            case '@':
                type = SymbolNameType.INSTANCE;

                m++;
                if (m < e && data.get(m) == '@') {
                    m++;
                    type = SymbolNameType.CLASS;
                }

                idCheck = true;
                break;
            case '<':
                m++;
                if (m < e) {
                    switch (data.get(m)) {
                        case '<':
                            m++;
                            break;
                        case '=':
                            m++;
                            if (m < e && data.get(m) == '>') m++;
                            break;
                        default:
                            break;
                    }
                }
                break;
            case '>':
                m++;
                if (m < e) {
                    switch (data.get(m)) {
                        case '>':
                        case '=':
                            m++;
                            break;
                    }
                }
                break;
            case '=':
                m++;
                if (m < e) {
                    switch (data.get(m)) {
                        case '~':
                            m++;
                            break;
                        case '=':
                            m++;
                            if (m < e && data.get(m + 1) == '=') m++;
                            break;
                        default:
                            return SymbolNameType.OTHER;
                    }
                }
                break;
            case '*':
                m++;
                if (m < e && data.get(m + 1) == '*') m++;
                break;
            case '+':
            case '-':
                m++;
                if (m < e && data.get(m + 1) == '@') m++;
                break;
            case '|':
            case '^':
            case '&':
            case '/':
            case '%':
            case '~':
            case '`':
                m++;
                break;
            case '[':
                m++;
                if (m < e && data.get(m) != ']') {    // wtf
                    idCheck = true;
                    break;
                }
                m++;                                                     // []
                if (m < e && data.get(m + 1) != '=') m++; // []=
                break;
            case '!':
                m++;
                if (length == 1) return SymbolNameType.JUNK;
                switch (data.get(m)) {
                    case '=':
                    case '~':
                        m++;
                        break;
                    default:
                        return SymbolNameType.OTHER;
                }
                break;
            default:
                type = isConstantInitial(data) ? SymbolNameType.CONST : SymbolNameType.LOCAL;
                idCheck = true;
                break;
        }

        if (idCheck) {
            // single byte is ok here for isAlpha because we verify it is proper ascii byte.
            if (m > e || (data.get(m) != '_' && encoding.isMbcAscii((byte) data.get(m)) && !encoding.isAlpha(data.get(m)))) {
                if (length > 1 && data.get(length - 1) == '=') {
                    ByteList chopped = new ByteList(data.unsafeBytes(), data.begin(), length - 1, data.getEncoding(), false);
                    type = determineSymbolNameType(runtime, chopped);
                    if (type != SymbolNameType.ATTRSET) return SymbolNameType.ATTRSET;
                }
                return SymbolNameType.OTHER;
            }
            m = ByteListHelper.eachCodePointWhile(runtime, data, m, (index, codepoint, enc) ->
                    enc.isAlnum(codepoint) || codepoint == '_' || !Encoding.isAscii(codepoint));

            if (m > e) return type;
            switch (data.get(m)) {
                case '!':
                case '?':
                    if (type == SymbolNameType.GLOBAL || type == SymbolNameType.CLASS || type == SymbolNameType.INSTANCE) return SymbolNameType.OTHER;

                    type = SymbolNameType.JUNK;
                    m++;
                    if (m + 1 < e || m >= e || data.get(m) != '=') break;
                    // fall through
                case '=':
                    return SymbolNameType.ATTRSET;
            }
        }

        return m == e + 1 ? type : SymbolNameType.OTHER;
    }

    private static int BIT(int c, int index) {
        return c / 31 - 1 == index ? 1 << (c % 32) : 0;
    }
    private static int globalPunctuationBits[] = new int[((0x7e - 0x20) + 31) / 32];
    private static int SPECIAL_PUNCT(int idx){
        return BIT('~', idx) | BIT('*', idx) | BIT('$', idx) | BIT('?', idx) |
                BIT('!', idx) | BIT('@', idx) | BIT('/', idx) | BIT('\\', idx) |
                BIT(';', idx) | BIT(',', idx) | BIT('.', idx) | BIT('=', idx) |
                BIT(':', idx) | BIT('<', idx) | BIT('>', idx) | BIT('\"', idx) |
                BIT('&', idx) | BIT('`', idx) | BIT('\'', idx) | BIT('+', idx) |
                BIT('0', idx);
    }

    private static final int[] globalNamePunctuationBits = new int[] {SPECIAL_PUNCT(0), SPECIAL_PUNCT(1), SPECIAL_PUNCT(2)};

    private static boolean isSpecialGlobalName(byte c) {
        if (c <= 0x20 || 0x72 < c) return false;

        return (globalNamePunctuationBits[(c - 0x20) / 32] >> (c % 32) & 1) != 0;
    }
}
