/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  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.  For additional information regarding
 * copyright in this work, please see the NOTICE file in the top level
 * directory of this distribution.
 */
package org.apache.abdera2.ext.json;

import java.io.IOException;
import java.io.Writer;
import java.util.Stack;

import javax.activation.MimeType;

import org.apache.abdera2.common.iri.IRI;
import org.apache.abdera2.common.date.DateTimes;
import org.apache.abdera2.common.http.EntityTag;
import org.joda.time.DateTime;

public class JSONStream {

    private final Writer writer;
    private int depth = 0;
    private Stack<Boolean> sepstack = new Stack<Boolean>();

    private void pushStack() {
        sepstack.push(true);
    }

    private boolean isStart() {
        boolean b = sepstack.peek();
        if (b) {
            sepstack.set(sepstack.size() - 1, false);
        }
        return b;
    }

    private void popStack() {
        sepstack.pop();
    }

    public JSONStream(Writer writer) {
        this.writer = writer;
    }

    private void inc() {
        depth++;
    }

    private void dec() {
        depth--;
    }

    private void writeIndent() throws IOException {
        for (int n = 0; n < depth; n++) {
            writer.write(' ');
        }
    }

    private void writeNewLine() throws IOException {
        writer.write('\n');
    }

    public void startObject() throws IOException {
        writer.write('{');
        inc();
        pushStack();
    }

    public void endObject() throws IOException {
        popStack();
        dec();
        writeNewLine();
        writeIndent();
        writer.write('}');
    }

    public void startArray() throws IOException {
        writer.write('[');
        inc();
    }

    public void endArray() throws IOException {
        dec();
        writeNewLine();
        writeIndent();
        writer.write(']');
    }

    public void writeSeparator() throws IOException {
        writer.write(',');
    }

    private void writeColon() throws IOException {
        writer.write(':');
    }

    public void writeQuoted(String value) throws IOException {
        if (value != null) {
            writer.write('"');
            writer.write(escape(value));
            writer.write('"');
        }
    }

    public void writeField(String name) throws IOException {
        if (!isStart()) {
            writeSeparator();
        }
        writeNewLine();
        writeIndent();
        writeQuoted(name);
        writeColon();
    }

    public void writeField(String name, DateTime value) throws IOException {
        if (value != null) {
            writeField(name, DateTimes.format(value));
        }
    }

    public void writeField(String name, IRI value) throws IOException {
        if (value != null) {
            writeField(name, value.toASCIIString());
        }
    }

    public void writeField(String name, MimeType value) throws IOException {
        if (value != null) {
            writeField(name, value.toString());
        }
    }

    public void writeField(String name, EntityTag value) throws IOException {
        if (value != null) {
            writeField(name, value.toString());
        }
    }

    public void writeField(String name, String value) throws IOException {
        if (value != null) {
            writeField(name);
            writeQuoted(value);
        }
    }

    public void writeField(String name, Number value) throws IOException {
        if (value != null) {
            writeField(name);
            writer.write(value.toString());
        }
    }

    public void writeField(String name, Boolean value) throws IOException {
        if (value != null) {
            writeField(name);
            writer.write(value.toString());
        }
    }

    private static String escape(String value) {
        if (value == null)
            return null;
        StringBuffer buf = new StringBuffer();
        char[] chars = value.toCharArray();
        char b = 0;
        String t = null;
        for (char c : chars) {
            switch (c) {
                case '\\':
                case '"':
                    buf.append('\\');
                    buf.append(c);
                    break;
                case '/':
                    if (b == '<')
                        buf.append('\\');
                    buf.append(c);
                    break;
                case '\b':
                    buf.append("\\b");
                    break;
                case '\t':
                    buf.append("\\t");
                    break;
                case '\n':
                    buf.append("\\n");
                    break;
                case '\f':
                    buf.append("\\f");
                    break;
                case '\r':
                    buf.append("\\r");
                    break;
                default:
                    if (c < ' ' || c > 127) {
                        t = "000" + Integer.toHexString(c);
                        buf.append("\\u" + t.substring(t.length() - 4));
                    } else {
                        buf.append(c);
                    }
            }
            b = c;
        }
        return buf.toString();
    }
}