/*
 * Copyright (C) 2010 The Android Open Source Project
 *
 * 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.android.tradefed.util;

import com.android.tradefed.log.LogUtil.CLog;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;

/**
 * A helper class to send an email.  Note that this class is NOT PLATFORM INDEPENDENT.  It will
 * likely fail on Windows, and possibly on Mac OS X as well.  It will fail on any machine where
 * The binary pointed at by the {@code mailer} constant doesn't exist.
 */
public class Email implements IEmail {
    private static final String[] mailer = {"/usr/sbin/sendmail", "-t", "-i"};
    static final String CRLF = "\r\n";

    private static String join(Collection<String> list, String sep) {
        StringBuilder builder = new StringBuilder();
        Iterator<String> iter = list.iterator();
        while (iter.hasNext()) {
            String element = iter.next();
            builder.append(element);
            if(iter.hasNext()) {
                builder.append(sep);
            }
        }
        return builder.toString();
    }

    /**
     * A helper method to use ProcessBuilder to create a new process.  This can't use
     * {@link com.android.tradefed.util.IRunUtil} because that class doesn't provide a way to pass
     * data to the stdin of the spawned process, which is the usage paradigm for most commandline
     * mailers such as mailx and sendmail.
     * <p/>
     * Exposed for mocking
     *
     * @param cmd The {@code String[]} to pass to the {@link ProcessBuilder} constructor
     * @return The {@link Process} returned from from {@link ProcessBuilder#start()}
     * @throws IOException if sending email failed in a synchronously-detectable way
     */
    Process run(String[] cmd) throws IOException {
        ProcessBuilder pb = new ProcessBuilder(cmd);
        pb.redirectErrorStream(true);
        return pb.start();
    }

    /**
     * A small helper function that adds the specified header to the header list only if the value
     * is non-null
     */
    private void addHeader(List<String> headers, String name, String value) {
        if (name == null || value == null) {
            return;
        }
        headers.add(String.format("%s: %s", name, value));
    }

    /**
     * A small helper function that adds the specified header to the header list only if the value
     * is non-null
     */
    private void addHeaders(List<String> headers, String name, Collection<String> values) {
        if (name == null || values == null) {
            return;
        }
        if (values.isEmpty()) {
            return;
        }

        final String strValues = join(values, ",");
        headers.add(String.format("%s: %s", name, strValues));
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void send(Message msg) throws IllegalArgumentException, IOException {
        // Validity checks
        if (msg.getTo() == null) {
            throw new IllegalArgumentException("Message is missing a destination");
        } else if (msg.getSubject() == null) {
            throw new IllegalArgumentException("Message is missing a subject");
        } else if (msg.getBody() == null) {
            throw new IllegalArgumentException("Message is missing a body");
        }

        // Sender, Recipients, CC, BCC, Subject are all set with appropriate email headers
        final ArrayList<String> headers = new ArrayList<String>();
        final String[] mailCmd;
        if (msg.getSender() != null) {
            addHeader(headers, "From", msg.getSender());

            // Envelope Sender (will receive any errors related to the email)
            int cmdLen = mailer.length + 2;
            mailCmd = Arrays.copyOf(mailer, cmdLen);
            mailCmd[cmdLen - 2] = "-f";
            mailCmd[cmdLen - 1] = msg.getSender();
        } else {
            mailCmd = mailer;
        }
        addHeaders(headers, "To", msg.getTo());
        addHeaders(headers, "Cc", msg.getCc());
        addHeaders(headers, "Bcc", msg.getBcc());
        addHeader(headers, "Content-type", msg.getContentType());
        addHeader(headers, "Subject", msg.getSubject());

        final StringBuilder fullMsg = new StringBuilder();
        fullMsg.append(join(headers, CRLF));
        fullMsg.append(CRLF);
        fullMsg.append(CRLF);
        fullMsg.append(msg.getBody());

        CLog.d("About to send email with command: %s", Arrays.toString(mailCmd));
        Process mailerProc = run(mailCmd);
        BufferedOutputStream mailerStdin = new BufferedOutputStream(mailerProc.getOutputStream());
        /* There is no such thing as a "character" in the land of the shell; there are only bytes.
         * Here, we convert the body from a Java string (consisting of characters) to a byte array
         * encoding each character with UTF-8.  Each character will be represented as between one
         * and four bytes apiece.
         */
        mailerStdin.write(fullMsg.toString().getBytes("UTF-8"));
        mailerStdin.flush();
        mailerStdin.close();

        int retValue;
        try {
            retValue = mailerProc.waitFor();
        } catch (InterruptedException e) {
            // ignore, but set retValue to something bogus
            retValue = -12345;
        }
        if (retValue != 0) {
            CLog.e("Mailer finished with non-zero return value: %d", retValue);
            BufferedInputStream mailerStdout = new BufferedInputStream(mailerProc.getInputStream());
            StringBuilder stdout = new StringBuilder();
            int theByte;
            while((theByte = mailerStdout.read()) != -1) {
                stdout.append((char)theByte);
            }
            CLog.e("Mailer output was: " + stdout.toString());
        } else {
            CLog.v("Mailer returned successfully.");
        }
    }
}