/*
 * Copyright (c) 2002-2012 Alibaba Group Holding Limited.
 * All rights reserved.
 *
 * Licensed 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.
 */

package com.alibaba.citrus.util.internal.webpagelite;

import static com.alibaba.citrus.util.Assert.*;
import static com.alibaba.citrus.util.ServletUtil.*;

import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintWriter;

/**
 * 代表一个request/response context。
 * <p>
 * 使用此抽象类，而不是使用标准的servlet api，目的是为了尽量减少对外界api的依赖。
 * </p>
 */
public abstract class RequestContext {
    private final String       baseURL;
    private final String       resourceName;
    private       PrintWriter  writer;
    private       OutputStream stream;

    public RequestContext(String baseURL, String resourceName) {
        if (!baseURL.endsWith("/")) {
            baseURL += "/";
        }

        if (resourceName.startsWith("/")) {
            resourceName = resourceName.substring(1);
        }

        this.baseURL = baseURL;
        this.resourceName = resourceName;
    }

    /** 取得URL中所请求的资源名称。 */
    public final String getResourceName() {
        return resourceName;
    }

    /** 取得基准URL。 */
    public final String getBaseURL() {
        return baseURL;
    }

    /** 取得指定资源名称所对应的URL。 */
    public final String getResourceURL(String resourceName) {
        return normalizeURI(baseURL + resourceName);
    }

    /**
     * 取得已经取得过的writer。
     *
     * @throws IllegalStateException 如果<code>getWriter(contentType)</code>
     *                               还没有被调用过。
     */
    public final PrintWriter getWriter() {
        return assertNotNull(writer, ExceptionType.ILLEGAL_STATE, "call getWriter(contentType) first");
    }

    /** 取得用来输出文本页面的<code>Writer</code>。 */
    public final PrintWriter getWriter(String contentType) throws IOException {
        if (writer == null) {
            writer = doGetWriter(contentType);
        }

        return writer;
    }

    protected abstract PrintWriter doGetWriter(String contentType) throws IOException;

    /**
     * 取得已经取得过的stream。
     *
     * @throws IllegalStateException 如果<code>getOutputStream(contentType)</code>
     *                               还没有被调用过。
     */
    public final OutputStream getOutputStream() {
        return assertNotNull(stream, ExceptionType.ILLEGAL_STATE, "call getOutputStream(contentType) first");
    }

    /** 取得用来输出二进制内容的<code>OutputStream</code>。 */
    public final OutputStream getOutputStream(String contentType) throws IOException {
        if (stream == null) {
            stream = doGetOutputStream(contentType);
        }

        return stream;
    }

    protected abstract OutputStream doGetOutputStream(String contentType) throws IOException;

    /** 资源未找到。 */
    public abstract void resourceNotFound(String resourceName) throws IOException;

    /** 重定向页面。 */
    public abstract void redirectTo(String location) throws IOException;

    @Override
    public String toString() {
        return String.format("%s[%s]", getClass().getSimpleName(), resourceName);
    }
}