////////////////////////////////////////////////////////////////////////////////
// checkstyle: Checks Java source code for adherence to a set of rules.
// Copyright (C) 2001-2020 the original author or authors.
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library 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
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
////////////////////////////////////////////////////////////////////////////////

package com.puppycrawl.tools.checkstyle.checks.header;

import java.io.File;
import java.util.Arrays;

import com.puppycrawl.tools.checkstyle.StatelessCheck;
import com.puppycrawl.tools.checkstyle.api.FileText;

/**
 * <p>
 * Checks that a source file begins with a specified header.
 * Property {@code headerFile} specifies a file that contains the required header.
 * Alternatively, the header specification can be set directly in the
 * {@code header} property without the need for an external file.
 * </p>
 * <p>
 * Property {@code ignoreLines} specifies the line numbers to ignore when matching
 * lines in a header file. This property is very useful for supporting headers
 * that contain copyright dates. For example, consider the following header:
 * </p>
 * <pre>
 * line 1: ////////////////////////////////////////////////////////////////////
 * line 2: // checkstyle:
 * line 3: // Checks Java source code for adherence to a set of rules.
 * line 4: // Copyright (C) 2002  Oliver Burn
 * line 5: ////////////////////////////////////////////////////////////////////
 * </pre>
 * <p>
 * Since the year information will change over time, you can tell Checkstyle
 * to ignore line 4 by setting property {@code ignoreLines} to {@code 4}.
 * </p>
 * <p>
 * In default configuration, if header is not specified, the default value
 * of header is set to {@code null} and the check does not rise any violations.
 * </p>
 * <ul>
 * <li>
 * Property {@code headerFile} - Specify the name of the file containing the required header.
 * Default value is {@code null}.
 * </li>
 * <li>
 * Property {@code charset} - Specify the character encoding to use when reading the headerFile.
 * Default value is the charset property of the parent
 * <a href="https://checkstyle.org/config.html#Checker">Checker</a> module.
 * </li>
 * <li>
 * Property {@code header} - Specify the required header specified inline.
 * Individual header lines must be separated by the string {@code "\n"}
 * (even on platforms with a different line separator), see examples below.
 * Default value is {@code null}.
 * </li>
 * <li>
 * Property {@code ignoreLines} - Specify the line numbers to ignore.
 * Default value is {@code {}}.
 * </li>
 * <li>
 * Property {@code fileExtensions} - Specify the file type extension of files to process.
 * Default value is {@code all files}.
 * </li>
 * </ul>
 * <p>
 * In default configuration the check does not rise any violations.
 * Default values of properties are used.
 * </p>
 * <pre>
 * &lt;module name="Header"/&gt;
 * </pre>
 * <p>
 * To configure the check to use header file {@code "config/java.header"}
 * and ignore lines {@code 2}, {@code 3}, and {@code 4} and only process Java files:
 * </p>
 * <pre>
 * &lt;module name="Header"&gt;
 *   &lt;property name="headerFile" value="config/java.header"/&gt;
 *   &lt;property name="ignoreLines" value="2, 3, 4"/&gt;
 *   &lt;property name="fileExtensions" value="java"/&gt;
 * &lt;/module&gt;
 * </pre>
 * <p>
 * To configure the check to verify that each file starts with the header
 * </p>
 * <pre>
 * // Copyright (C) 2004 MyCompany
 * // All rights reserved
 * </pre>
 * <p>
 * without the need for an external header file:
 * </p>
 * <pre>
 * &lt;module name="Header"&gt;
 *   &lt;property name="header"
 *     value="// Copyright (C) 2004 MyCompany\n// All rights reserved"/&gt;
 * &lt;/module&gt;
 * </pre>
 *
 * @since 6.9
 */
@StatelessCheck
public class HeaderCheck extends AbstractHeaderCheck {

    /**
     * A key is pointing to the warning message text in "messages.properties"
     * file.
     */
    public static final String MSG_MISSING = "header.missing";

    /**
     * A key is pointing to the warning message text in "messages.properties"
     * file.
     */
    public static final String MSG_MISMATCH = "header.mismatch";

    /** Empty array to avoid instantiations. */
    private static final int[] EMPTY_INT_ARRAY = new int[0];

    /** Specify the line numbers to ignore. */
    private int[] ignoreLines = EMPTY_INT_ARRAY;

    /**
     * Returns true if lineNo is header lines or false.
     * @param lineNo a line number
     * @return if {@code lineNo} is one of the ignored header lines.
     */
    private boolean isIgnoreLine(int lineNo) {
        return Arrays.binarySearch(ignoreLines, lineNo) >= 0;
    }

    /**
     * Checks if a code line matches the required header line.
     * @param lineNumber the line number to check against the header
     * @param line the line contents
     * @return true if and only if the line matches the required header line
     */
    private boolean isMatch(int lineNumber, String line) {
        // skip lines we are meant to ignore
        return isIgnoreLine(lineNumber + 1)
            || getHeaderLines().get(lineNumber).equals(line);
    }

    /**
     * Setter to specify the line numbers to ignore.
     *
     * @param list comma separated list of line numbers to ignore in header.
     */
    public void setIgnoreLines(int... list) {
        if (list.length == 0) {
            ignoreLines = EMPTY_INT_ARRAY;
        }
        else {
            ignoreLines = new int[list.length];
            System.arraycopy(list, 0, ignoreLines, 0, list.length);
            Arrays.sort(ignoreLines);
        }
    }

    @Override
    protected void processFiltered(File file, FileText fileText) {
        if (getHeaderLines().size() > fileText.size()) {
            log(1, MSG_MISSING);
        }
        else {
            for (int i = 0; i < getHeaderLines().size(); i++) {
                if (!isMatch(i, fileText.get(i))) {
                    log(i + 1, MSG_MISMATCH, getHeaderLines().get(i));
                    break;
                }
            }
        }
    }

    @Override
    protected void postProcessHeaderLines() {
        // no code
    }

}
