/**
 * i-net software provides programming examples for illustration only, without warranty
 * either expressed or implied, including, but not limited to, the implied warranties
 * of merchantability and/or fitness for a particular purpose. This programming example
 * assumes that you are familiar with the programming language being demonstrated and
 * the tools used to create and debug procedures. i-net software support professionals
 * can help explain the functionality of a particular procedure, but they will not modify
 * these examples to provide added functionality or construct procedures to meet your
 * specific needs.
 *
 * Copyright © 1999-2025 i-net software GmbH, Berlin, Germany.
**/
package com.inet.authentication.passwordfile;
/*
    either expressed or implied, including, but not limited to, the implied warranties
    of merchantability and/or fitness for a particular purpose. This programming example
    assumes that you are familiar with the programming language being demonstrated and
    the tools used to create and debug procedures. i-net software support professionals
    can help explain the functionality of a particular procedure, but they will not modify
    these examples to provide added functionality or construct procedures to meet your
    specific needs.
    © i-net software 1998-2017
*/

import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * It is responsible for reading data from password file defined in configuration for Password File Authentication.<br>
 * Content of the password file must be UTF-8-encoded. Each text line of the file must represent data of single
 * user:<br>
 * <br>
 * <b><code>userName:realm:ha1</code></b><br>
 * <br>
 * where <b>ha1</b> is MD5 hash value of A1 which is defined by RFC7616 as <br>
 * <b><code>A1 = unq(username) ":" unq(realm) ":" passwd</code></b><br>
 * <br>
 * <b>For example:</b><br>
 * <code>bob:i-net Clear Reports:253e2ac5a9c0c3d0fc0a5092ba886cec</code><br>
 */
public class PasswordFile {

    private String              passwordFile;

    private Map<String, String> map                  = new HashMap<>();

    private String              previousFilePath     = null;

    private long                previousLastModified = -1;

    /**
     * Set the current password file.
     * 
     * @param passwordFile current file;
     */
    void setPasswordFile( String passwordFile ) {
        this.passwordFile = passwordFile;
    }

    /**
     * Returns hash value of A1 for given user and realm or null.
     * 
     * @param userName name of the user from the request.
     * @param realm realm from the request.
     * @return hash value of A1 for given user and realm or null.
     * @throws IOException if an I/O error occurs reading from the file or a malformed or unmappable byte sequence is
     *             read.
     */
    public synchronized String getHashValueOfA1( String userName, String realm ) throws IOException {
        try {
            loadData();
        } catch( IOException ex ) {
            map.clear();
            previousFilePath = null;
            previousLastModified = -1;
            throw ex;
        }
        return map.get( userName + ":" + realm );
    }

    /**
     * Loads data from password file, if needed. It does nothing if path that denotes password file and its time of last
     * modification have not been changed since last call.
     * 
     * @throws IOException if an I/O error occurs reading from the file or a malformed or unmappable byte sequence is
     *             read.
     */
    private void loadData() throws IOException {
        String filePath = passwordFile;
        Path passwordFile = Paths.get( filePath );
        long lastModified = passwordFile.toFile().lastModified();

        if( previousFilePath != null && previousFilePath.equals( filePath ) && previousLastModified == lastModified ) {
            return;
        }
        map.clear();

        List<String> allLines = Files.readAllLines( passwordFile, StandardCharsets.UTF_8 );
        for( String line : allLines ) {
            int index = line.lastIndexOf( ":" );
            if( index <= 0 || index == line.length() - 1 ) {
                continue;
            }
            String key = line.substring( 0, index );
            String value = line.substring( index + 1 );
            map.put( key, value );
        }

        previousFilePath = filePath;
        previousLastModified = lastModified;
    }
}