/*

 * Copyright (c) 2015, 2016, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 */

package java.net.http;

import java.io.IOException;

import java.io.UnsupportedEncodingException;

import java.nio.ByteBuffer;

import java.nio.charset.Charset;

import java.nio.charset.StandardCharsets;

import java.util.Collection;

import java.util.Collections;

import java.util.HashMap;

import java.util.LinkedList;

import java.util.List;

import java.util.Locale;

import java.util.Map;

import java.util.Optional;

import java.util.Set;

/**

 * Reads response headers off channel, in blocking mode. Entire header

 * block is collected in a byte[]. The offset location of the start of

 * each header name is recorded in an array to facilitate later searching.

 *

 * The location of "Content-length" is recorded explicitly. Similar approach

 * could be taken for other common headers.

 *

 * This class is not thread-safe

 */

class ResponseHeaders implements HttpHeaders1 {

    static final int DATA_SIZE = 16 * 1024;  // initial space for headers

    static final int NUM_HEADERS = 50; // initial expected max number of headers

    final HttpConnection connection;

    byte[] data;

    int contentlen = -2; // means not initialized

    ByteBuffer buffer;

    /**

     * Following used for scanning the array looking for:

     *      - well known headers

     *      - end of header block

     */

    int[] headerOffsets; // index into data

    int numHeaders;

    int count;

    ByteBuffer residue; // after headers processed, data may be here

    ResponseHeaders(HttpConnection connection, ByteBuffer buffer) {

        this.connection = connection;

        initOffsets();

        this.buffer = buffer;

        data = new byte[DATA_SIZE];

    }

    int getContentLength() throws IOException {

        if (contentlen != -2) {

            return contentlen;

        }

        int[] search = findHeaderValue("Content-length");

        if (search[0] == -1) {

            contentlen = -1;

            return -1;

        }

        int i = search[0];

        while (data[i] == ' ' || data[i] == '\t') {

            i++;

            if (i == data.length || data[i] == CR || data[i] == LF) {

                throw new IOException("Bad header");

            }

        }

        contentlen = 0;

        int digit = data[i++] - 0x30;

        while (digit >= 0 && digit <= 9) {

            contentlen = contentlen * 10 + digit;

            digit = data[i++] - 0x30;

        }

        return contentlen;

    }

    void log() {

        populateMap(false);

    }

    void  populateMap(boolean clearOffsets) {

        StringBuilder sb;

        for (int i = 0; i < numHeaders; i++) {

            sb = new StringBuilder(32);

            int offset = headerOffsets[i];

            if (offset == -1) {

                continue;

            }

            int j;

            for (j=0; data[offset+j] != ':'; j++) {

                // byte to char promotion ok for US-ASCII

                sb.append((char)data[offset+j]);

            }

            String name = sb.toString();

            List<String> l = getOrCreate(name);

            addEntry(l, name, offset + j + 1);

            // clear the offset

            if (clearOffsets)

                headerOffsets[i] = -1;

        }

    }

    void addEntry(List<String> l, String name, int j) {

        while (data[j] == ' ' || data[j] == '\t') {

            j++;

        }

        int vstart = j;

            // TODO: back slash ??

        while (data[j] != CR) {

            j++;

        }

        try {

            String value = new String(data, vstart, j - vstart, "US-ASCII");

            l.add(value);

        } catch (UnsupportedEncodingException e) {

            // can't happen

            throw new InternalError(e);

        }

    }

    // returns an int[2]: [0] = offset of value in data[]

    // [1] = offset in headerOffsets. Both are -1 in error

    private int[] findHeaderValue(String name) {

        int[] result = new int[2];

        byte[] namebytes = getBytes(name);

 outer: for (int i = 0; i < numHeaders; i++) {

            int offset = headerOffsets[i];

            if (offset == -1) {

                continue;

            }

            for (int j=0; j<namebytes.length; j++) {

                if (namebytes[j] != lowerCase(data[offset+j])) {

                    continue outer;

                }

            }

            // next char must be ':'

            if (data[offset+namebytes.length] != ':') {

                continue;

            }

            result[0] = offset+namebytes.length + 1;

            result[1] = i;

            return result;

        }

        result[0] = -1;

        result[1] = -1;

        return result;

    }

    /**

     * Populates the map for header values with the given name.

     * The offsets are cleared for any that are found, so they don't

     * get repeatedly searched.

     */

    List<String> populateMapEntry(String name) {

        List<String> l = getOrCreate(name);

        int[] search = findHeaderValue(name);

        if (search[0] != -1) {

            addEntry(l, name, search[0]);

            // clear the offset

            headerOffsets[search[1]] = -1;

        }

        return l;

    }

    static final Locale usLocale = Locale.US;

    static final Charset ascii = StandardCharsets.US_ASCII;

    private byte[] getBytes(String name) {

        return name.toLowerCase(usLocale).getBytes(ascii);

    }

    /*

     * We read buffers in a loop until we detect end of headers

     * CRLFCRLF. Each byte received is copied into the byte[] data

     * The position of the first byte of each header (after a CRLF)

     * is recorded in a separate array showing the location of

     * each header name.

     */

    void initHeaders() throws IOException {

        inHeaderName = true;

        endOfHeader = true;

        for (int numBuffers = 0; true; numBuffers++) {

            if (numBuffers > 0) {

                buffer = connection.read();

            }

            if (buffer == null) {

                throw new IOException("Error reading headers");

            }

            if (!buffer.hasRemaining()) {

                continue;

            }

            // Position set to first byte

            int start = buffer.position();

            byte[] backing = buffer.array();

            int len = buffer.limit() - start;

            for (int i = 0; i < len; i++) {

                byte b = backing[i + start];

                if (inHeaderName) {

                    b = lowerCase(b);

                }

                if (b == ':') {

                    inHeaderName = false;

                }

                data[count++] = b;

                checkByte(b);

                if (firstChar) {

                    recordHeaderOffset(count-1);

                    firstChar = false;

                }

                if (endOfHeader && numHeaders == 0) {

                    // empty headers

                    endOfAllHeaders = true;

                }

                if (endOfAllHeaders) {

                    int newposition = i + 1 + start;

                    if (newposition <= buffer.limit()) {

                        buffer.position(newposition);

                        residue = buffer;

                    } else {

                        residue = null;

                    }

                    return;

                }

                if (count == data.length) {

                    resizeData();

                }

            }

        }

    }

    static final int CR = 13;

    static final int LF = 10;

    int crlfCount = 0;

    // results of checkByte()

    boolean endOfHeader; // just seen LF after CR before

    boolean endOfAllHeaders; // just seen LF after CRLFCR before

    boolean firstChar; //

    boolean inHeaderName; // examining header name

    void checkByte(byte b) throws IOException {

        if (endOfHeader &&  b != CR && b != LF)

            firstChar = true;

        endOfHeader = false;

        endOfAllHeaders = false;

        switch (crlfCount) {

            case 0:

                crlfCount = b == CR ? 1 : 0;

                break;

            case 1:

                crlfCount = b == LF ? 2 : 0;

                endOfHeader = true;

                inHeaderName = true;

                break;

            case 2:

                crlfCount = b == CR ? 3 : 0;

                break;

            case 3:

                if (b != LF) {

                    throw new IOException("Bad header block termination");

                }

                endOfAllHeaders = true;

                break;

        }

    }

    byte lowerCase(byte b) {

        if (b >= 0x41 && b <= 0x5A)

            b = (byte)(b + 32);

        return b;

    }

    void resizeData() {

        int oldlen = data.length;

        int newlen = oldlen * 2;

        byte[] newdata = new byte[newlen];

        System.arraycopy(data, 0, newdata, 0, oldlen);

        data = newdata;

    }

    final void initOffsets() {

        headerOffsets = new int[NUM_HEADERS];

        numHeaders = 0;

    }

    ByteBuffer getResidue() {

        return residue;

    }

    void recordHeaderOffset(int index) {

        if (numHeaders >= headerOffsets.length) {

            int oldlen = headerOffsets.length;

            int newlen = oldlen * 2;

            int[] new1 = new int[newlen];

            System.arraycopy(headerOffsets, 0, new1, 0, oldlen);

            headerOffsets = new1;

        }

        headerOffsets[numHeaders++] = index;

    }

    /**

     * As entries are read from the byte[] they are placed in here

     * So we always check this map first

     */

    Map<String,List<String>> headers = new HashMap<>();

    @Override

    public Optional<String> firstValue(String name) {

        List<String> l =  allValues(name);

        if (l == null || l.isEmpty()) {

            return Optional.ofNullable(null);

        } else {

            return Optional.of(l.get(0));

        }

    }

    @Override

    public List<String> allValues(String name) {

        name = name.toLowerCase(usLocale);

        List<String> l = headers.get(name);

        if (l == null) {

            l = populateMapEntry(name);

        }

        return Collections.unmodifiableList(l);

    }

    @Override

    public void makeUnmodifiable() {

    }

    // Delegates map to HashMap but converts keys to lower case

    static class HeaderMap implements Map<String,List<String>> {

        Map<String,List<String>> inner;

        HeaderMap(Map<String,List<String>> inner) {

            this.inner = inner;

        }

        @Override

        public int size() {

            return inner.size();

        }

        @Override

        public boolean isEmpty() {

            return inner.isEmpty();

        }

        @Override

        public boolean containsKey(Object key) {

            if (!(key instanceof String)) {

                return false;

            }

            String s = ((String)key).toLowerCase(usLocale);

            return inner.containsKey(s);

        }

        @Override

        public boolean containsValue(Object value) {

            return inner.containsValue(value);

        }

        @Override

        public List<String> get(Object key) {

            String s = ((String)key).toLowerCase(usLocale);

            return inner.get(s);

        }

        @Override

        public List<String> put(String key, List<String> value) {

            throw new UnsupportedOperationException("Not supported");

        }

        @Override

        public List<String> remove(Object key) {

            throw new UnsupportedOperationException("Not supported");

        }

        @Override

        public void putAll(Map<? extends String, ? extends List<String>> m) {

            throw new UnsupportedOperationException("Not supported");

        }

        @Override

        public void clear() {

            throw new UnsupportedOperationException("Not supported");

        }

        @Override

        public Set<String> keySet() {

            return inner.keySet();

        }

        @Override

        public Collection<List<String>> values() {

            return inner.values();

        }

        @Override

        public Set<Entry<String, List<String>>> entrySet() {

            return inner.entrySet();

        }

    }

    @Override

    public Map<String, List<String>> map() {

        populateMap(true);

        return new HeaderMap(headers);

    }

    Map<String, List<String>> mapInternal() {

        populateMap(false);

        return new HeaderMap(headers);

    }

    private List<String> getOrCreate(String name) {

        List<String> l = headers.get(name);

        if (l == null) {

            l = new LinkedList<>();

            headers.put(name, l);

        }

        return l;

    }

    @Override

    public Optional<Long> firstValueAsLong(String name) {

        List<String> l =  allValues(name);

        if (l == null) {

            return Optional.ofNullable(null);

        } else {

            String v = l.get(0);

            Long lv = Long.parseLong(v);

            return Optional.of(lv);

        }

    }

}