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1 // Package icf implements the Inherited Configuration Format parser.
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2 //
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3 // ICF is a rule-based configuration format with variables, abstract blocks
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4 // (mixins), pattern matching with named capture groups, and brace expansion.
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5 package icf
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6
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7 import (
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8 "bufio"
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9 "fmt"
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10 "io"
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11 "strings"
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12 )
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13
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14 type Directive struct {
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15 Key string
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16 Args []string
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17 }
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18
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19 type Config struct {
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20 vars map[string]string
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21 abstract map[string][]Directive
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22 Blocks []ParsedBlock
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23 }
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24
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25 type ParsedBlock struct {
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26 ID string
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27 Mixin string
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28 Directives []Directive
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29 }
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30
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2
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31 type rawBlock struct {
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32 id string
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33 mixin string
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34 directives []rawDirective
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35 }
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36
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37 type rawDirective struct {
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38 key string
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39 args []string // after brace expansion, before var substitution
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40 }
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41
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0
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42 func Parse(r io.Reader) (*Config, error) {
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2
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43 lines, err := readLines(r)
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44 if err != nil {
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45 return nil, err
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0
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46 }
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47
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2
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48 // --- Pass 1: collect variables ---
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49 vars := make(map[string]string)
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4
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50 subst := makeSubst(vars)
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51
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2
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52 for _, line := range lines {
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53 if i := strings.Index(line, "="); i > 0 && !strings.HasPrefix(line, "|>") {
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54 key := line[:i]
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55 if isVarName(key) {
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4
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56 vars[key] = subst(strings.TrimSpace(line[i+1:]), nil)
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2
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57 }
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58 }
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59 }
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60
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61 // --- Pass 2: parse blocks (raw, no capture substitution yet) ---
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62 var raws []rawBlock
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63 var cur *rawBlock
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0
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64
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65 flush := func() {
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66 if cur != nil {
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67 raws = append(raws, *cur)
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68 cur = nil
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69 }
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70 }
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71
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2
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72 for _, line := range lines {
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73 if i := strings.Index(line, "="); i > 0 && !strings.HasPrefix(line, "|>") {
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74 if isVarName(line[:i]) {
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75 continue
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76 }
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77 }
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78
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79 if strings.HasPrefix(line, "|>") {
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80 if cur == nil {
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81 return nil, fmt.Errorf("icf: directive outside block: %q", line)
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82 }
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83 parts := strings.Fields(strings.TrimSpace(line[2:]))
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84 if len(parts) == 0 {
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85 continue
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86 }
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2
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87 cur.directives = append(cur.directives, rawDirective{
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88 key: parts[0],
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89 args: braceExpand(parts[1:]),
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90 })
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91 continue
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92 }
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93
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94 flush()
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95 parts := strings.Fields(line)
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96 rb := rawBlock{id: subst(parts[0], nil)}
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97 if len(parts) >= 2 && strings.HasPrefix(parts[1], "@") {
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98 rb.mixin = subst(parts[1][1:], nil)
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99 }
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100 cur = &rb
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0
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101 }
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102 flush()
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103
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2
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104 // --- Pass 3: separate abstract from concrete, apply var substitution ---
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105 c := &Config{
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106 vars: vars,
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107 abstract: make(map[string][]Directive),
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108 }
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109
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110 for _, rb := range raws {
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111 dirs := make([]Directive, len(rb.directives))
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112 for i, rd := range rb.directives {
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113 args := make([]string, len(rd.args))
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114 for j, a := range rd.args {
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115 args[j] = subst(a, nil)
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116 }
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117 dirs[i] = Directive{Key: rd.key, Args: args}
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118 }
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119
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120 if strings.HasPrefix(rb.id, "@") {
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121 c.abstract[rb.id[1:]] = dirs
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122 } else {
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2
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123 c.Blocks = append(c.Blocks, ParsedBlock{
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124 ID: rb.id,
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125 Mixin: rb.mixin,
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126 Directives: dirs,
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127 })
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128 }
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129 }
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130
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131 return c, nil
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132 }
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133
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2
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134 // Abstract returns the directives of a named abstract block.
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135 // Returns nil if not found.
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136 func (c *Config) Abstract(name string) []Directive {
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137 return c.abstract[name]
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138 }
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139
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140 // Match finds the most specific block matching input (e.g. "host/path") and
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141 // returns resolved directives plus named captures.
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2
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142 // Domain is matched exactly; path uses prefix match.
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143 func (c *Config) Match(input string) ([]Directive, map[string]string) {
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144 inHost, inPath, _ := strings.Cut(input, "/")
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145
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146 type hit struct {
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147 block ParsedBlock
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148 captures map[string]string
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149 score int
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150 }
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151 var best *hit
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152
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153 for _, b := range c.Blocks {
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154 patHost, patPath, hasPath := strings.Cut(b.ID, "/")
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155 caps := make(map[string]string)
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156
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157 domScore, ok := matchExact(patHost, inHost, caps)
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158 if !ok {
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159 continue
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160 }
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161
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162 pathScore := 0
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163 if hasPath {
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164 pathScore, ok = matchPrefix(patPath, inPath, caps)
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165 if !ok {
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166 continue
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167 }
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168 }
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169
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170 score := domScore*1000 + pathScore
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171 if best == nil || score > best.score {
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172 best = &hit{block: b, captures: caps, score: score}
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173 }
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174 }
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175
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176 if best == nil {
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177 return nil, nil
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178 }
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179
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180 return c.ResolveBlock(best.block, best.captures), best.captures
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181 }
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182
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183 // ResolveBlock merges mixin directives (lower priority) with block directives,
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184 // then substitutes capture variables.
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185 func (c *Config) ResolveBlock(b ParsedBlock, caps map[string]string) []Directive {
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186 var merged []Directive
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187 if b.Mixin != "" {
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188 merged = append(merged, c.abstract[b.Mixin]...)
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189 }
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190 merged = append(merged, b.Directives...)
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2
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191
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192 if len(caps) == 0 {
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193 return merged
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194 }
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195
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196 // Substitute capture variables into a copy
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197 subst := makeSubst(c.vars)
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198 out := make([]Directive, len(merged))
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199 for i, d := range merged {
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200 out[i].Key = d.Key
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201 out[i].Args = make([]string, len(d.Args))
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202 for j, a := range d.Args {
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203 out[i].Args[j] = subst(a, caps)
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204 }
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205 }
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206 return out
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207 }
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208
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209 // makeSubst returns a function that substitutes $VAR in s,
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210 // checking caps first, then vars.
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211 func makeSubst(vars map[string]string) func(s string, caps map[string]string) string {
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212 return func(s string, caps map[string]string) string {
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213 if !strings.Contains(s, "$") {
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214 return s
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0
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215 }
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216 var b strings.Builder
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217 i := 0
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218 for i < len(s) {
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219 if s[i] != '$' {
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220 b.WriteByte(s[i])
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221 i++
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222 continue
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223 }
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224 j := i + 1
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225 for j < len(s) && isVarChar(s[j]) {
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226 j++
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227 }
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228 name := s[i+1 : j]
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229 if caps != nil {
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230 if v, ok := caps[name]; ok {
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231 b.WriteString(v)
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232 i = j
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233 continue
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234 }
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235 }
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236 if v, ok := vars[name]; ok {
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237 b.WriteString(v)
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238 } else {
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239 b.WriteString(s[i:j])
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240 }
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241 i = j
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0
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242 }
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243 return b.String()
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244 }
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245 }
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246
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247 func readLines(r io.Reader) ([]string, error) {
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248 var out []string
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249 scanner := bufio.NewScanner(r)
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250 for scanner.Scan() {
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251 line := stripComment(strings.TrimSpace(scanner.Text()))
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252 if line != "" {
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253 out = append(out, line)
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254 }
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255 }
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2
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256 return out, scanner.Err()
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0
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257 }
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258
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259 func matchExact(pat, s string, caps map[string]string) (int, bool) {
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260 score, rem, ok := matchCaptures(pat, s, caps)
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261 if !ok || rem != "" {
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262 return 0, false
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263 }
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264 return score, true
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265 }
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266
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267 func matchPrefix(pat, s string, caps map[string]string) (int, bool) {
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268 score, _, ok := matchCaptures(pat, s, caps)
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269 return score, ok
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270 }
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271
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272 func matchCaptures(pat, inp string, caps map[string]string) (int, string, bool) {
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273 for {
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274 if pat == "" {
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275 return 0, inp, true
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276 }
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277
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278 if strings.HasPrefix(pat, "<") {
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279 end := strings.Index(pat, ">")
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280 if end == -1 {
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281 return 0, "", false
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282 }
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283 capName := pat[1:end]
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284 rest := pat[end+1:]
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285
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286 for split := 1; split <= len(inp); split++ {
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2
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287 score, finalRem, ok := matchCaptures(rest, inp[split:], caps)
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288 if ok {
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289 if capName != "_" {
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290 caps[capName] = inp[:split]
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0
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291 }
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292 return score, finalRem, true
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293 }
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294 }
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295 return 0, "", false
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296 }
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297
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298 if inp == "" || pat[0] != inp[0] {
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299 return 0, "", false
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300 }
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301 score, rem, ok := matchCaptures(pat[1:], inp[1:], caps)
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302 return score + 1, rem, ok
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303 }
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304 }
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305
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306 func braceExpand(args []string) []string {
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307 var out []string
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308 for _, a := range args {
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309 out = append(out, expandOne(a)...)
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310 }
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311 return out
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312 }
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313
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314 func expandOne(s string) []string {
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315 start := strings.Index(s, "{")
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316 end := strings.Index(s, "}")
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317 if start == -1 || end == -1 || end < start {
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318 return []string{s}
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319 }
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320 prefix := s[:start]
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321 suffix := s[end+1:]
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322 var out []string
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323 for _, v := range strings.Split(s[start+1:end], ",") {
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324 out = append(out, prefix+strings.TrimSpace(v)+suffix)
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325 }
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326 return out
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327 }
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328
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329 func stripComment(line string) string {
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330 if strings.HasPrefix(line, ";") {
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331 return ""
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332 }
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333 if i := strings.Index(line, " ;"); i != -1 {
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334 return strings.TrimSpace(line[:i])
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335 }
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336 return line
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337 }
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338
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339 func isVarName(s string) bool {
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340 if s == "" {
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341 return false
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342 }
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343 for i := 0; i < len(s); i++ {
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344 if !isVarChar(s[i]) {
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345 return false
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346 }
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347 }
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348 return true
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349 }
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350
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351 func isVarChar(c byte) bool {
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352 return (c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z') ||
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353 (c >= '0' && c <= '9') || c == '_'
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2
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354 } |
