1. 1
2. 2
3. 3
4. 4
5. 5
6. 6
7. 7
8. 8
9. 9
10. 10
11. 11
12. 12
13. 13
14. 14
15. 15
16. 16
17. 17
18. 18
19. 19
20. 20
21. 21
22. 22
23. 23
24. 24
25. 25
26. 26
27. 27
28. 28
29. 29
30. 30
31. 31
32. 32
33. 33
34. 34
35. 35
36. 36
37. 37
38. 38
39. 39
40. 40
41. 41
42. 42
43. 43
44. 44
45. 45
46. 46
47. 47
48. 48
49. 49
50. 50
51. 51
52. 52
53. 53
54. 54
55. 55
56. 56
57. 57
58. 58
59. 59
60. 60
61. 61
62. 62
63. 63
64. 64
65. 65
66. 66
67. 67
68. 68
69. 69
70. 70
71. 71
72. 72
73. 73
74. 74
75. 75
76. 76
77. 77
78. 78
79. 79
80. 80
81. 81
82. 82
83. 83
84. 84
85. 85
86. 86
87. 87
88. 88
89. 89
90. 90
91. 91
92. 92
93. 93
94. 94
95. 95
96. 96
97. 97
98. 98
99. 99
100. 100
101. 101
102. 102
103. 103
104. 104
105. 105
106. 106
107. 107
108. 108
109. 109
110. 110
111. 111
112. 112
113. 113
114. 114
115. 115
116. 116
117. 117
118. 118
119. 119
120. 120
121. 121
122. 122
123. 123
124. 124
125. 125
126. 126
127. 127
128. 128
129. 129
130. 130
131. 131
132. 132
133. 133
134. 134
135. 135
136. 136
137. 137
138. 138
139. 139
140. 140
141. 141
142. 142
143. 143
144. 144
145. 145
146. 146
147. 147
148. 148
149. 149
150. 150
151. 151
152. 152
153. 153
154. 154
155. 155
156. 156
157. 157
158. 158
159. 159
160. 160
161. 161
162. 162
163. 163
164. 164
165. 165
166. 166
167. 167
168. 168
169. 169
170. 170
171. 171
172. 172
173. 173
174. 174
175. 175
176. 176
177. 177
178. 178
179. 179
180. 180

// Copyright 2025 Shota FUJI <pockawoooh@gmail.com>
//
// 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.
//
// SPDX-License-Identifier: Apache-2.0

package main

import (
	"errors"
	"flag"
	"fmt"
	"log"
	"os"
	"os/exec"
	"strings"
)

// Path to the home-manager bin.
// Normally this will be overridden at compile time via "ldflags -X main.homeManagerPath=<path>".
var homeManagerPath = "home-manager"

func main() {
	help := flag.Bool("help", false, "Print usage text to stdout.")
	verbose := flag.Bool("verbose", false, "Enable verbose logging.")

	flag.Parse()

	logger := log.New(os.Stderr, "", 0)

	if *help {
		fmt.Print(helpText())
		os.Exit(0)
	}

	clean(logger, *verbose)
}

func helpText() string {
	binName := os.Args[0]

	return fmt.Sprintf(`%s - Clean obsolete Home-Manager generations.

[Usage]
	%s

[OPTIONS]
  --help
    Print this message to stdout.

  --verbose
    Enable verbose logging.
`, binName, binName)
}

func clean(logger *log.Logger, verbose bool) {
	generations, err := Generations(logger)
	if err != nil {
		logger.Fatalf("Failed to get generations: %s", err)
	}

	args := []string{"remove-generations"}

	for i, generation := range generations {
		if verbose {
			logger.Printf("Found generation ID=%s", generation.ID)
		}

		if i == 0 {
			if verbose {
				logger.Printf("Skipping initial generation ID=%s", generation.ID)
			}
			continue
		}

		logger.Printf("Removing generation ID=%s", generation.ID)

		args = append(args, generation.ID)
	}

	if len(args) == 1 {
		logger.Print("No generations to remove.")
		os.Exit(0)
	}

	cmd := exec.Command(homeManagerPath, args...)

	var out strings.Builder
	cmd.Stdout = &out

	if err := cmd.Run(); err != nil {
		logger.Fatalf("Failed to remove generations: %s", err)
	}
}

type Generation struct {
	ID string
}

func ParseGeneration(line string) (*Generation, error) {
	tokens := strings.Split(line, " ")

	colonPosition := -1

	for i, token := range tokens {
		if token == ":" {
			colonPosition = i
			break
		}
	}

	if colonPosition < 0 {
		return nil, errors.New("Unexpected generation output line: No colon found")
	}

	if len(tokens) < colonPosition+4 {
		return nil, errors.New("Unexpected generation output line: Missing tokens")
	}

	if tokens[colonPosition+1] != "id" {
		return nil, fmt.Errorf("Unexpected generation output line: Expected `id`, found `%s`", tokens[colonPosition+1])
	}

	id := tokens[colonPosition+2]

	if tokens[colonPosition+3] != "->" {
		return nil, fmt.Errorf("Unexpected generation output line: Expected `->`, found `%s`", tokens[colonPosition+3])
	}

	return &Generation{
		ID: id,
	}, nil
}

func Generations(logger *log.Logger) ([]Generation, error) {
	cmd := exec.Command(homeManagerPath, "generations")

	var out strings.Builder
	cmd.Stdout = &out

	if err := cmd.Run(); err != nil {
		return nil, err
	}

	stdout := out.String()
	lines := strings.Split(stdout, "\n")

	generations := make([]Generation, 0, len(lines))

	for _, line := range strings.Split(stdout, "\n") {
		if len(strings.TrimSpace(line)) == 0 {
			continue
		}

		tokens := strings.Split(line, " ")
		if len(tokens) == 0 {
			continue
		}

		generation, err := ParseGeneration(line)
		if err != nil {
			logger.Printf("Failed to parse generation output: %s", err.Error())
			continue
		}

		generations = append(generations, *generation)
	}

	return generations, nil
}