/*
 * ====================================================================
 * 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.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 */

package com.amazonaws.util;

import java.nio.ByteBuffer;
import java.nio.charset.Charset;
import java.util.BitSet;
import java.util.List;

import com.amazonaws.annotation.Immutable;

// Copied and extracted from httpcomponents-client-4.3.6.
/**
 * A collection of utilities for encoding URLs.
 *
 * @since 4.0
 */
@Immutable
class URLEncodedUtils {
    private static final char QP_SEP_A = '&';
    private static final String NAME_VALUE_SEPARATOR = "=";

    /**
     * Returns a String that is suitable for use as an {@code application/x-www-form-urlencoded}
     * list of parameters in an HTTP PUT or HTTP POST.
     *
     * @param parameters  The parameters to include.
     * @param charset The encoding to use.
     * @return An {@code application/x-www-form-urlencoded} string
     */
    public static String format(
            final List <? extends NameValuePair> parameters,
            final String charset) {
        return format(parameters, QP_SEP_A, charset);
    }

    /**
     * Returns a String that is suitable for use as an {@code application/x-www-form-urlencoded}
     * list of parameters in an HTTP PUT or HTTP POST.
     *
     * @param parameters  The parameters to include.
     * @param parameterSeparator The parameter separator, by convention, {@code '&'} or {@code ';'}.
     * @param charset The encoding to use.
     * @return An {@code application/x-www-form-urlencoded} string
     *
     * @since 4.3
     */
    public static String format(
            final List <? extends NameValuePair> parameters,
            final char parameterSeparator,
            final String charset) {
        final StringBuilder result = new StringBuilder();
        for (final NameValuePair parameter : parameters) {
            final String encodedName = encodeFormFields(parameter.getName(), charset);
            final String encodedValue = encodeFormFields(parameter.getValue(), charset);
            if (result.length() > 0) {
                result.append(parameterSeparator);
            }
            result.append(encodedName);
            if (encodedValue != null) {
                result.append(NAME_VALUE_SEPARATOR);
                result.append(encodedValue);
            }
        }
        return result.toString();
    }

    /**
     * Returns a String that is suitable for use as an {@code application/x-www-form-urlencoded}
     * list of parameters in an HTTP PUT or HTTP POST.
     *
     * @param parameters  The parameters to include.
     * @param charset The encoding to use.
     * @return An {@code application/x-www-form-urlencoded} string
     *
     * @since 4.2
     */
    public static String format(
            final Iterable<? extends NameValuePair> parameters,
            final Charset charset) {
        return format(parameters, QP_SEP_A, charset);
    }

    /**
     * Returns a String that is suitable for use as an {@code application/x-www-form-urlencoded}
     * list of parameters in an HTTP PUT or HTTP POST.
     *
     * @param parameters  The parameters to include.
     * @param parameterSeparator The parameter separator, by convention, {@code '&'} or {@code ';'}.
     * @param charset The encoding to use.
     * @return An {@code application/x-www-form-urlencoded} string
     *
     * @since 4.3
     */
    public static String format(
            final Iterable<? extends NameValuePair> parameters,
            final char parameterSeparator,
            final Charset charset) {
        final StringBuilder result = new StringBuilder();
        for (final NameValuePair parameter : parameters) {
            final String encodedName = encodeFormFields(parameter.getName(), charset);
            final String encodedValue = encodeFormFields(parameter.getValue(), charset);
            if (result.length() > 0) {
                result.append(parameterSeparator);
            }
            result.append(encodedName);
            if (encodedValue != null) {
                result.append(NAME_VALUE_SEPARATOR);
                result.append(encodedValue);
            }
        }
        return result.toString();
    }

    /**
     * Unreserved characters, i.e. alphanumeric, plus: {@code _ - ! . ~ ' ( ) *}
     * <p>
     *  This list is the same as the {@code unreserved} list in
     *  <a href="http://www.ietf.org/rfc/rfc2396.txt">RFC 2396</a>
     */
    private static final BitSet UNRESERVED   = new BitSet(256);
    /**
     * Punctuation characters: , ; : $ & + =
     * <p>
     * These are the additional characters allowed by userinfo.
     */
    private static final BitSet PUNCT        = new BitSet(256);
    /** Characters which are safe to use in userinfo,
     * i.e. {@link #UNRESERVED} plus {@link #PUNCT}uation */
    private static final BitSet USERINFO     = new BitSet(256);
    /** Characters which are safe to use in a path,
     * i.e. {@link #UNRESERVED} plus {@link #PUNCT}uation plus / @ */
    private static final BitSet PATHSAFE     = new BitSet(256);
    /** Characters which are safe to use in a query or a fragment,
     * i.e. {@link #RESERVED} plus {@link #UNRESERVED} */
    private static final BitSet URIC     = new BitSet(256);

    /**
     * Reserved characters, i.e. {@code ;/?:@&=+$,[]}
     * <p>
     *  This list is the same as the {@code reserved} list in
     *  <a href="http://www.ietf.org/rfc/rfc2396.txt">RFC 2396</a>
     *  as augmented by
     *  <a href="http://www.ietf.org/rfc/rfc2732.txt">RFC 2732</a>
     */
    private static final BitSet RESERVED     = new BitSet(256);


    /**
     * Safe characters for x-www-form-urlencoded data, as per java.net.URLEncoder and browser behaviour,
     * i.e. alphanumeric plus {@code "-", "_", ".", "*"}
     */
    private static final BitSet URLENCODER   = new BitSet(256);

    static {
        // unreserved chars
        // alpha characters
        for (int i = 'a'; i <= 'z'; i++) {
            UNRESERVED.set(i);
        }
        for (int i = 'A'; i <= 'Z'; i++) {
            UNRESERVED.set(i);
        }
        // numeric characters
        for (int i = '0'; i <= '9'; i++) {
            UNRESERVED.set(i);
        }
        UNRESERVED.set('_'); // these are the charactes of the "mark" list
        UNRESERVED.set('-');
        UNRESERVED.set('.');
        UNRESERVED.set('*');
        URLENCODER.or(UNRESERVED); // skip remaining unreserved characters
        UNRESERVED.set('!');
        UNRESERVED.set('~');
        UNRESERVED.set('\'');
        UNRESERVED.set('(');
        UNRESERVED.set(')');
        // punct chars
        PUNCT.set(',');
        PUNCT.set(';');
        PUNCT.set(':');
        PUNCT.set('$');
        PUNCT.set('&');
        PUNCT.set('+');
        PUNCT.set('=');
        // Safe for userinfo
        USERINFO.or(UNRESERVED);
        USERINFO.or(PUNCT);

        // URL path safe
        PATHSAFE.or(UNRESERVED);
        PATHSAFE.set('/'); // segment separator
        PATHSAFE.set(';'); // param separator
        PATHSAFE.set(':'); // rest as per list in 2396, i.e. : @ & = + $ ,
        PATHSAFE.set('@');
        PATHSAFE.set('&');
        PATHSAFE.set('=');
        PATHSAFE.set('+');
        PATHSAFE.set('$');
        PATHSAFE.set(',');

        RESERVED.set(';');
        RESERVED.set('/');
        RESERVED.set('?');
        RESERVED.set(':');
        RESERVED.set('@');
        RESERVED.set('&');
        RESERVED.set('=');
        RESERVED.set('+');
        RESERVED.set('$');
        RESERVED.set(',');
        RESERVED.set('['); // added by RFC 2732
        RESERVED.set(']'); // added by RFC 2732

        URIC.or(RESERVED);
        URIC.or(UNRESERVED);
    }

    private static final int RADIX = 16;

    private static String urlEncode(
            final String content,
            final Charset charset,
            final BitSet safechars,
            final boolean blankAsPlus) {
        if (content == null) {
            return null;
        }
        final StringBuilder buf = new StringBuilder();
        final ByteBuffer bb = charset.encode(content);
        while (bb.hasRemaining()) {
            final int b = bb.get() & 0xff;
            if (safechars.get(b)) {
                buf.append((char) b);
            } else if (blankAsPlus && b == ' ') {
                buf.append('+');
            } else {
                buf.append("%");
                final char hex1 = Character.toUpperCase(Character.forDigit((b >> 4) & 0xF, RADIX));
                final char hex2 = Character.toUpperCase(Character.forDigit(b & 0xF, RADIX));
                buf.append(hex1);
                buf.append(hex2);
            }
        }
        return buf.toString();
    }

    /**
     * Encode/escape www-url-form-encoded content.
     * <p>
     * Uses the {@link #URLENCODER} set of characters, rather than
     * the {@link #UNRSERVED} set; this is for compatibilty with previous
     * releases, URLEncoder.encode() and most browsers.
     *
     * @param content the content to encode, will convert space to '+'
     * @param charset the charset to use
     * @return encoded string
     */
    private static String encodeFormFields(final String content, final String charset) {
        if (content == null) {
            return null;
        }
        return urlEncode(content, charset != null ? Charset.forName(charset) : StringUtils.UTF8, URLENCODER, true);
    }

    /**
     * Encode/escape www-url-form-encoded content.
     * <p>
     * Uses the {@link #URLENCODER} set of characters, rather than
     * the {@link #UNRSERVED} set; this is for compatibilty with previous
     * releases, URLEncoder.encode() and most browsers.
     *
     * @param content the content to encode, will convert space to '+'
     * @param charset the charset to use
     * @return encoded string
     */
    private static String encodeFormFields (final String content, final Charset charset) {
        if (content == null) {
            return null;
        }
        return urlEncode(content, charset != null ? charset : StringUtils.UTF8, URLENCODER, true);
    }

    /**
     * Encode a String using the {@link #USERINFO} set of characters.
     * <p>
     * Used by URIBuilder to encode the userinfo segment.
     *
     * @param content the string to encode, does not convert space to '+'
     * @param charset the charset to use
     * @return the encoded string
     */
    static String encUserInfo(final String content, final Charset charset) {
        return urlEncode(content, charset, USERINFO, false);
    }

    /**
     * Encode a String using the {@link #URIC} set of characters.
     * <p>
     * Used by URIBuilder to encode the query and fragment segments.
     *
     * @param content the string to encode, does not convert space to '+'
     * @param charset the charset to use
     * @return the encoded string
     */
    static String encUric(final String content, final Charset charset) {
        return urlEncode(content, charset, URIC, false);
    }

    /**
     * Encode a String using the {@link #PATHSAFE} set of characters.
     * <p>
     * Used by URIBuilder to encode path segments.
     *
     * @param content the string to encode, does not convert space to '+'
     * @param charset the charset to use
     * @return the encoded string
     */
    static String encPath(final String content, final Charset charset) {
        return urlEncode(content, charset, PATHSAFE, false);
    }
}