package org.eclipse.aether.util.version;

/*
 * 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.
 */

import java.math.BigInteger;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.TreeMap;

import org.eclipse.aether.version.Version;

/**
 * A generic version, that is a version that accepts any input string and tries to apply common sense sorting. See
 * {@link GenericVersionScheme} for details.
 */
final class GenericVersion
    implements Version
{

    private final String version;

    private final Item[] items;

    private final int hash;

    /**
     * Creates a generic version from the specified string.
     * 
     * @param version The version string, must not be {@code null}.
     */
    GenericVersion( String version )
    {
        this.version = version;
        items = parse( version );
        hash = Arrays.hashCode( items );
    }

    private static Item[] parse( String version )
    {
        List<Item> items = new ArrayList<>();

        for ( Tokenizer tokenizer = new Tokenizer( version ); tokenizer.next(); )
        {
            Item item = tokenizer.toItem();
            items.add( item );
        }

        trimPadding( items );

        return items.toArray( new Item[items.size()] );
    }

    private static void trimPadding( List<Item> items )
    {
        Boolean number = null;
        int end = items.size() - 1;
        for ( int i = end; i > 0; i-- )
        {
            Item item = items.get( i );
            if ( !Boolean.valueOf( item.isNumber() ).equals( number ) )
            {
                end = i;
                number = item.isNumber();
            }
            if ( end == i && ( i == items.size() - 1 || items.get( i - 1 ).isNumber() == item.isNumber() )
                && item.compareTo( null ) == 0 )
            {
                items.remove( i );
                end--;
            }
        }
    }

    public int compareTo( Version obj )
    {
        final Item[] these = items;
        final Item[] those = ( (GenericVersion) obj ).items;

        boolean number = true;

        for ( int index = 0;; index++ )
        {
            if ( index >= these.length && index >= those.length )
            {
                return 0;
            }
            else if ( index >= these.length )
            {
                return -comparePadding( those, index, null );
            }
            else if ( index >= those.length )
            {
                return comparePadding( these, index, null );
            }

            Item thisItem = these[index];
            Item thatItem = those[index];

            if ( thisItem.isNumber() != thatItem.isNumber() )
            {
                if ( number == thisItem.isNumber() )
                {
                    return comparePadding( these, index, number );
                }
                else
                {
                    return -comparePadding( those, index, number );
                }
            }
            else
            {
                int rel = thisItem.compareTo( thatItem );
                if ( rel != 0 )
                {
                    return rel;
                }
                number = thisItem.isNumber();
            }
        }
    }

    private static int comparePadding( Item[] items, int index, Boolean number )
    {
        int rel = 0;
        for ( int i = index; i < items.length; i++ )
        {
            Item item = items[i];
            if ( number != null && number != item.isNumber() )
            {
                break;
            }
            rel = item.compareTo( null );
            if ( rel != 0 )
            {
                break;
            }
        }
        return rel;
    }

    @Override
    public boolean equals( Object obj )
    {
        return ( obj instanceof GenericVersion ) && compareTo( (GenericVersion) obj ) == 0;
    }

    @Override
    public int hashCode()
    {
        return hash;
    }

    @Override
    public String toString()
    {
        return version;
    }

    static final class Tokenizer
    {

        private static final Integer QUALIFIER_ALPHA = -5;

        private static final Integer QUALIFIER_BETA = -4;

        private static final Integer QUALIFIER_MILESTONE = -3;

        private static final Map<String, Integer> QUALIFIERS;

        static
        {
            QUALIFIERS = new TreeMap<>( String.CASE_INSENSITIVE_ORDER );
            QUALIFIERS.put( "alpha", QUALIFIER_ALPHA );
            QUALIFIERS.put( "beta", QUALIFIER_BETA );
            QUALIFIERS.put( "milestone", QUALIFIER_MILESTONE );
            QUALIFIERS.put( "cr", -2 );
            QUALIFIERS.put( "rc", -2 );
            QUALIFIERS.put( "snapshot", -1 );
            QUALIFIERS.put( "ga", 0 );
            QUALIFIERS.put( "final", 0 );
            QUALIFIERS.put( "release", 0 );
            QUALIFIERS.put( "", 0 );
            QUALIFIERS.put( "sp", 1 );
        }

        private final String version;

        private int index;

        private String token;

        private boolean number;

        private boolean terminatedByNumber;

        Tokenizer( String version )
        {
            this.version = ( version.length() > 0 ) ? version : "0";
        }

        public boolean next()
        {
            final int n = version.length();
            if ( index >= n )
            {
                return false;
            }

            int state = -2;

            int start = index;
            int end = n;
            terminatedByNumber = false;

            for ( ; index < n; index++ )
            {
                char c = version.charAt( index );

                if ( c == '.' || c == '-' || c == '_' )
                {
                    end = index;
                    index++;
                    break;
                }
                else
                {
                    int digit = Character.digit( c, 10 );
                    if ( digit >= 0 )
                    {
                        if ( state == -1 )
                        {
                            end = index;
                            terminatedByNumber = true;
                            break;
                        }
                        if ( state == 0 )
                        {
                            // normalize numbers and strip leading zeros (prereq for Integer/BigInteger handling)
                            start++;
                        }
                        state = ( state > 0 || digit > 0 ) ? 1 : 0;
                    }
                    else
                    {
                        if ( state >= 0 )
                        {
                            end = index;
                            break;
                        }
                        state = -1;
                    }
                }

            }

            if ( end - start > 0 )
            {
                token = version.substring( start, end );
                number = state >= 0;
            }
            else
            {
                token = "0";
                number = true;
            }

            return true;
        }

        @Override
        public String toString()
        {
            return String.valueOf( token );
        }

        public Item toItem()
        {
            if ( number )
            {
                try
                {
                    if ( token.length() < 10 )
                    {
                        return new Item( Item.KIND_INT, Integer.parseInt( token ) );
                    }
                    else
                    {
                        return new Item( Item.KIND_BIGINT, new BigInteger( token ) );
                    }
                }
                catch ( NumberFormatException e )
                {
                    throw new IllegalStateException( e );
                }
            }
            else
            {
                if ( index >= version.length() )
                {
                    if ( "min".equalsIgnoreCase( token ) )
                    {
                        return Item.MIN;
                    }
                    else if ( "max".equalsIgnoreCase( token ) )
                    {
                        return Item.MAX;
                    }
                }
                if ( terminatedByNumber && token.length() == 1 )
                {
                    switch ( token.charAt( 0 ) )
                    {
                        case 'a':
                        case 'A':
                            return new Item( Item.KIND_QUALIFIER, QUALIFIER_ALPHA );
                        case 'b':
                        case 'B':
                            return new Item( Item.KIND_QUALIFIER, QUALIFIER_BETA );
                        case 'm':
                        case 'M':
                            return new Item( Item.KIND_QUALIFIER, QUALIFIER_MILESTONE );
                        default:
                    }
                }
                Integer qualifier = QUALIFIERS.get( token );
                if ( qualifier != null )
                {
                    return new Item( Item.KIND_QUALIFIER, qualifier );
                }
                else
                {
                    return new Item( Item.KIND_STRING, token.toLowerCase( Locale.ENGLISH ) );
                }
            }
        }

    }

    static final class Item
    {

        static final int KIND_MAX = 8;

        static final int KIND_BIGINT = 5;

        static final int KIND_INT = 4;

        static final int KIND_STRING = 3;

        static final int KIND_QUALIFIER = 2;

        static final int KIND_MIN = 0;

        static final Item MAX = new Item( KIND_MAX, "max" );

        static final Item MIN = new Item( KIND_MIN, "min" );

        private final int kind;

        private final Object value;

        Item( int kind, Object value )
        {
            this.kind = kind;
            this.value = value;
        }

        public boolean isNumber()
        {
            return ( kind & KIND_QUALIFIER ) == 0; // i.e. kind != string/qualifier
        }

        public int compareTo( Item that )
        {
            int rel;
            if ( that == null )
            {
                // null in this context denotes the pad item (0 or "ga")
                switch ( kind )
                {
                    case KIND_MIN:
                        rel = -1;
                        break;
                    case KIND_MAX:
                    case KIND_BIGINT:
                    case KIND_STRING:
                        rel = 1;
                        break;
                    case KIND_INT:
                    case KIND_QUALIFIER:
                        rel = (Integer) value;
                        break;
                    default:
                        throw new IllegalStateException( "unknown version item kind " + kind );
                }
            }
            else
            {
                rel = kind - that.kind;
                if ( rel == 0 )
                {
                    switch ( kind )
                    {
                        case KIND_MAX:
                        case KIND_MIN:
                            break;
                        case KIND_BIGINT:
                            rel = ( (BigInteger) value ).compareTo( (BigInteger) that.value );
                            break;
                        case KIND_INT:
                        case KIND_QUALIFIER:
                            rel = ( (Integer) value ).compareTo( (Integer) that.value );
                            break;
                        case KIND_STRING:
                            rel = ( (String) value ).compareToIgnoreCase( (String) that.value );
                            break;
                        default:
                            throw new IllegalStateException( "unknown version item kind " + kind );
                    }
                }
            }
            return rel;
        }

        @Override
        public boolean equals( Object obj )
        {
            return ( obj instanceof Item ) && compareTo( (Item) obj ) == 0;
        }

        @Override
        public int hashCode()
        {
            return value.hashCode() + kind * 31;
        }

        @Override
        public String toString()
        {
            return String.valueOf( value );
        }

    }

}
