File: jsons.go
   1 /*
   2 The MIT License (MIT)
   3 
   4 Copyright (c) 2026 pacman64
   5 
   6 Permission is hereby granted, free of charge, to any person obtaining a copy of
   7 this software and associated documentation files (the "Software"), to deal
   8 in the Software without restriction, including without limitation the rights to
   9 use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
  10 of the Software, and to permit persons to whom the Software is furnished to do
  11 so, subject to the following conditions:
  12 
  13 The above copyright notice and this permission notice shall be included in all
  14 copies or substantial portions of the Software.
  15 
  16 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  19 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  20 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  21 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  22 SOFTWARE.
  23 */
  24 
  25 /*
  26 To compile a smaller-sized command-line app, you can use the `go` command as
  27 follows:
  28 
  29 go build -ldflags "-s -w" -trimpath jsons.go
  30 */
  31 
  32 package main
  33 
  34 import (
  35     "bufio"
  36     "io"
  37     "os"
  38     "strings"
  39 )
  40 
  41 const info = `
  42 jsons [options...] [filenames...]
  43 
  44 JSON Strings turns TSV (tab-separated values) data into a JSON array of
  45 objects whose values are strings or nulls, the latter being used for
  46 missing trailing values.
  47 `
  48 
  49 func main() {
  50     if len(os.Args) > 1 {
  51         switch os.Args[1] {
  52         case `-h`, `--h`, `-help`, `--help`:
  53             os.Stdout.WriteString(info[1:])
  54             return
  55         }
  56     }
  57 
  58     err := run(os.Args[1:])
  59     if err == io.EOF {
  60         err = nil
  61     }
  62 
  63     if err != nil {
  64         os.Stderr.WriteString(err.Error())
  65         os.Stderr.WriteString("\n")
  66         os.Exit(1)
  67     }
  68 }
  69 
  70 type runConfig struct {
  71     lines int
  72     keys  []string
  73 }
  74 
  75 func run(paths []string) error {
  76     bw := bufio.NewWriter(os.Stdout)
  77     defer bw.Flush()
  78 
  79     dashes := 0
  80     var cfg runConfig
  81 
  82     for _, path := range paths {
  83         if path == `-` {
  84             dashes++
  85             if dashes > 1 {
  86                 continue
  87             }
  88 
  89             if err := handleInput(bw, os.Stdin, &cfg); err != nil {
  90                 return err
  91             }
  92 
  93             continue
  94         }
  95 
  96         if err := handleFile(bw, path, &cfg); err != nil {
  97             return err
  98         }
  99     }
 100 
 101     if len(paths) == 0 {
 102         if err := handleInput(bw, os.Stdin, &cfg); err != nil {
 103             return err
 104         }
 105     }
 106 
 107     if cfg.lines > 1 {
 108         bw.WriteString("\n]\n")
 109     } else {
 110         bw.WriteString("[]\n")
 111     }
 112     return nil
 113 }
 114 
 115 func handleFile(w *bufio.Writer, path string, cfg *runConfig) error {
 116     f, err := os.Open(path)
 117     if err != nil {
 118         return err
 119     }
 120     defer f.Close()
 121     return handleInput(w, f, cfg)
 122 }
 123 
 124 func escapeKeys(line string) []string {
 125     var keys []string
 126     var sb strings.Builder
 127 
 128     loopTSV(line, func(i int, s string) {
 129         sb.WriteByte('"')
 130         for _, r := range s {
 131             if r == '\\' || r == '"' {
 132                 sb.WriteByte('\\')
 133             }
 134             sb.WriteRune(r)
 135         }
 136         sb.WriteByte('"')
 137 
 138         keys = append(keys, sb.String())
 139         sb.Reset()
 140     })
 141 
 142     return keys
 143 }
 144 
 145 func emitRow(w *bufio.Writer, line string, keys []string) {
 146     j := 0
 147     w.WriteByte('{')
 148 
 149     loopTSV(line, func(i int, s string) {
 150         j = i
 151         if i > 0 {
 152             w.WriteString(", ")
 153         }
 154 
 155         w.WriteString(keys[i])
 156         w.WriteString(": \"")
 157 
 158         for _, r := range s {
 159             if r == '\\' || r == '"' {
 160                 w.WriteByte('\\')
 161             }
 162             w.WriteRune(r)
 163         }
 164         w.WriteByte('"')
 165     })
 166 
 167     for i := j + 1; i < len(keys); i++ {
 168         if i > 0 {
 169             w.WriteString(", ")
 170         }
 171         w.WriteString(keys[i])
 172         w.WriteString(": null")
 173     }
 174     w.WriteByte('}')
 175 }
 176 
 177 func loopTSV(line string, f func(i int, s string)) {
 178     for i := 0; len(line) > 0; i++ {
 179         pos := strings.IndexByte(line, '\t')
 180         if pos < 0 {
 181             f(i, line)
 182             return
 183         }
 184 
 185         f(i, line[:pos])
 186         line = line[pos+1:]
 187     }
 188 }
 189 
 190 func handleInput(w *bufio.Writer, r io.Reader, cfg *runConfig) error {
 191     const gb = 1024 * 1024 * 1024
 192     sc := bufio.NewScanner(r)
 193     sc.Buffer(nil, 8*gb)
 194 
 195     for i := 0; sc.Scan(); i++ {
 196         s := sc.Text()
 197         if i == 0 && strings.HasPrefix(s, "\xef\xbb\xbf") {
 198             s = s[3:]
 199         }
 200 
 201         if cfg.lines == 0 {
 202             cfg.keys = escapeKeys(s)
 203             w.WriteByte('[')
 204             cfg.lines++
 205             continue
 206         }
 207 
 208         if cfg.lines == 1 {
 209             w.WriteString("\n  ")
 210         } else {
 211             if _, err := w.WriteString(",\n  "); err != nil {
 212                 return io.EOF
 213             }
 214         }
 215 
 216         emitRow(w, s, cfg.keys)
 217         cfg.lines++
 218     }
 219 
 220     return sc.Err()
 221 }