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Mock server library for testing HTTP clients.
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/*
 * Copyright (C) 2019 Christopher J. Stehno
 *
 * 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.stehno.ersatz.encdec;

import groovy.json.JsonSlurper;
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUpload;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.UploadContext;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;

import java.io.*;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.util.HashMap;
import java.util.List;
import java.util.function.BiFunction;

import static com.stehno.ersatz.cfg.ContentType.TEXT_PLAIN;
import static java.net.URLDecoder.decode;
import static java.nio.charset.StandardCharsets.UTF_8;

/**
 * Reusable request content decoder functions. Decoders are simply implementations of the BiFunction<byte[], DecodingContext, Object>
 * interface, which takes the request content as a byte array along with the DecodingContext to return an Object
 * representation of the request data.
 */
public class Decoders {

    /**
     * Decoder that simply passes the content bytes through as an array of bytes.
     */
    public static final BiFunction passthrough = (content, ctx) -> content;

    /**
     * Decoder that converts request content bytes into a UTF-8 string.
     */
    public static final BiFunction utf8String = (content, ctx) -> content != null ? new String(content, UTF_8) : "";

    /**
     * Decoder that converts request content bytes into a string of JSON and then parses it with JsonSlurper to return parsed JSON data.
     */
    public static final BiFunction parseJson = (content, ctx) -> new JsonSlurper().parse(content != null ? content : "{}".getBytes(UTF_8));

    /**
     * Decoder that converts request content bytes in a url-encoded format into a map of name/value pairs.
     */
    public static final BiFunction urlEncoded = (content, ctx) -> {
        final var map = new HashMap();
        if (content != null) {

            for (final String nvp : new String(content, UTF_8).split("&")) {
                final String[] parts = nvp.split("=");
                try {
                    map.put(decode(parts[0], UTF_8.name()), decode(parts[1], UTF_8.name()));
                } catch (UnsupportedEncodingException e) {
                    throw new IllegalArgumentException(e);
                }
            }
        }

        return map;
    };

    /**
     * Decoder that converts request content bytes into a MultipartRequestContent object populated with the multipart request content.
     */
    public static final BiFunction multipart = (content, ctx) -> {
        File tempDir;
        try {
            tempDir = Files.createTempDirectory("ersatz-").toFile();
        } catch (IOException e) {
            throw new IllegalArgumentException(e);
        }

        List parts;
        try {
            parts = new FileUpload(new DiskFileItemFactory(10_000, tempDir)).parseRequest(new UploadContext() {
                @Override
                public long contentLength() {
                    return ctx.getContentLength();
                }

                @Override
                public String getCharacterEncoding() {
                    return ctx.getCharacterEncoding();
                }

                @Override
                public String getContentType() {
                    return ctx.getContentType();
                }

                @Override
                public int getContentLength() {
                    return (int) ctx.getContentLength();
                }

                @Override
                public InputStream getInputStream() throws IOException {
                    return new ByteArrayInputStream(content);
                }
            });
        } catch (FileUploadException e) {
            throw new IllegalArgumentException(e);
        }

        final MultipartRequestContent multipartRequest = new MultipartRequestContent();

        parts.forEach(part -> {
            final DecodingContext partCtx = new DecodingContext(part.getSize(), part.getContentType(), null, ctx.getDecoderChain());

            if (part.isFormField()) {
                multipartRequest.part(part.getFieldName(), TEXT_PLAIN, ctx.getDecoderChain().resolve(TEXT_PLAIN).apply(part.get(), partCtx));
            } else {
                multipartRequest.part(
                    part.getFieldName(),
                    part.getName(),
                    part.getContentType(),
                    ctx.getDecoderChain().resolve(part.getContentType()).apply(part.get(), partCtx)
                );
            }
        });

        return multipartRequest;
    };
}