File size: 3,879 Bytes
5bbfb59
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
/*
 * Copyright (C) 2014-2021 Arpit Khurana <arpitkh96@gmail.com>, Vishal Nehra <vishalmeham2@gmail.com>,
 * Emmanuel Messulam<emmanuelbendavid@gmail.com>, Raymond Lai <airwave209gt at gmail.com> and Contributors.
 *
 * This file is part of Amaze File Manager.
 *
 * Amaze File Manager is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

package com.amaze.filemanager.filesystem

import kotlin.random.Random

object RandomPathGenerator {
    const val separator = '/'

    private val letters = ('A'..'Z').toSet() + ('a'..'z').toSet()
    private val numbers = ('0'..'9').toSet()
    private val other = setOf('.', '_', '-')
    private val reservedFileNames = setOf("", ".", "..")

    /**
     * Generates a valid random path
     */
    fun generateRandomPath(
        random: Random,
        length: Int,
    ): String {
        assert(length > 0)

        val slashesInPath = random.nextInt(length / 4)

        return generateRandomPath(random, length, slashesInPath)
    }

    /**
     * Generates a valid random path, with a specific amount of directories
     */
    fun generateRandomPath(
        random: Random,
        length: Int,
        slashesInPath: Int,
    ): String {
        assert(length > slashesInPath * 2)

        val namesInPath = slashesInPath + 1

        val filenameLengths =
            List(namesInPath) {
                (length - slashesInPath) / namesInPath
            }

        val pathBuilder = mutableListOf<String>()

        for (filenameLength in filenameLengths) {
            val filename = generateRandomFilename(random, filenameLength)
            pathBuilder.add(filename)
        }

        var path = pathBuilder.joinToString(separator = separator.toString())

        val randomNumber = random.nextDouble(0.0, 1.0)

        if (randomNumber < 0.2) {
            // 20% end slash
            path = path.dropLast(1)
            path += separator
            return path
        }

        if (randomNumber < 0.6) {
            // 40% end extension
            val extension = List(3) { letters.random(random) }.joinToString(separator = "")

            path = path.dropLast(4)
            path += ".$extension"
            return path
        }

        return path
    }

    private fun generateRandomFilename(
        random: Random,
        length: Int,
    ): String {
        assert(length > 0)

        var name = ""

        while (reservedFileNames.contains(name)) {
            name =
                List(length) { generateRandomCharacter(random) }
                    .joinToString("")
        }

        return name
    }

    /**
     * Characters from POSIX 3.282 Portable Filename Character Set.
     *
     * Not all characters should be tested equally,
     * this ensures that paths not only contain letters.
     */
    private fun generateRandomCharacter(random: Random): Char {
        val randomNumber = random.nextDouble(0.0, 1.0)

        if (randomNumber < 0.4) {
            // 40% characters
            return letters.random(random)
        }

        if (randomNumber < 0.8) {
            // 40% numbers
            return numbers.random(random)
        }

        if (randomNumber < 1.0) {
            // 20% other
            return other.random(random)
        }

        throw IllegalStateException()
    }
}