File: jsons.go
   1 /*
   2 The MIT License (MIT)
   3 
   4 Copyright © 2020-2025 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 Single-file source-code for jsons.
  27 
  28 To compile a smaller-sized command-line app, you can use the `go` command as
  29 follows:
  30 
  31 go build -ldflags "-s -w" -trimpath jsons.go
  32 */
  33 
  34 package main
  35 
  36 import (
  37     "bufio"
  38     "io"
  39     "os"
  40     "strings"
  41 )
  42 
  43 const info = `
  44 jsons [options...] [filenames...]
  45 
  46 JSON Strings turns TSV (tab-separated values) data into a JSON array of
  47 objects whose values are strings or nulls, the latter being used for
  48 missing trailing values.
  49 `
  50 
  51 // noMoreOutput is a custom error-type meant to be deliberately ignored
  52 type noMoreOutput struct{}
  53 
  54 func (nmo noMoreOutput) Error() string {
  55     return `no more output`
  56 }
  57 
  58 func main() {
  59     if len(os.Args) > 1 {
  60         switch os.Args[1] {
  61         case `-h`, `--h`, `-help`, `--help`:
  62             os.Stdout.WriteString(info[1:])
  63             return
  64         }
  65     }
  66 
  67     err := run(os.Args[1:])
  68     if _, ok := err.(noMoreOutput); ok {
  69         err = nil
  70     }
  71 
  72     if err != nil {
  73         os.Stderr.WriteString("\x1b[31m")
  74         os.Stderr.WriteString(err.Error())
  75         os.Stderr.WriteString("\x1b[0m\n")
  76         os.Exit(1)
  77     }
  78 }
  79 
  80 type runConfig struct {
  81     lines int
  82     keys  []string
  83 }
  84 
  85 func run(paths []string) error {
  86     bw := bufio.NewWriter(os.Stdout)
  87     defer bw.Flush()
  88 
  89     dashes := 0
  90     var cfg runConfig
  91 
  92     for _, path := range paths {
  93         if path == `-` {
  94             dashes++
  95             if dashes > 1 {
  96                 continue
  97             }
  98 
  99             if err := handleInput(bw, os.Stdin, &cfg); err != nil {
 100                 return err
 101             }
 102 
 103             continue
 104         }
 105 
 106         if err := handleFile(bw, path, &cfg); err != nil {
 107             return err
 108         }
 109     }
 110 
 111     if len(paths) == 0 {
 112         if err := handleInput(bw, os.Stdin, &cfg); err != nil {
 113             return err
 114         }
 115     }
 116 
 117     if cfg.lines > 1 {
 118         bw.WriteString("\n]\n")
 119     } else {
 120         bw.WriteString("[]\n")
 121     }
 122     return nil
 123 }
 124 
 125 func handleFile(w *bufio.Writer, path string, cfg *runConfig) error {
 126     f, err := os.Open(path)
 127     if err != nil {
 128         return err
 129     }
 130     defer f.Close()
 131     return handleInput(w, f, cfg)
 132 }
 133 
 134 func escapeKeys(line string) []string {
 135     var keys []string
 136     var sb strings.Builder
 137 
 138     loopTSV(line, func(i int, s string) {
 139         sb.WriteByte('"')
 140         for _, r := range s {
 141             if r == '\\' || r == '"' {
 142                 sb.WriteByte('\\')
 143             }
 144             sb.WriteRune(r)
 145         }
 146         sb.WriteByte('"')
 147 
 148         keys = append(keys, sb.String())
 149         sb.Reset()
 150     })
 151 
 152     return keys
 153 }
 154 
 155 func emitRow(w *bufio.Writer, line string, keys []string) {
 156     j := 0
 157     w.WriteByte('{')
 158 
 159     loopTSV(line, func(i int, s string) {
 160         j = i
 161         if i > 0 {
 162             w.WriteString(", ")
 163         }
 164 
 165         w.WriteString(keys[i])
 166         w.WriteString(": \"")
 167 
 168         for _, r := range s {
 169             if r == '\\' || r == '"' {
 170                 w.WriteByte('\\')
 171             }
 172             w.WriteRune(r)
 173         }
 174         w.WriteByte('"')
 175     })
 176 
 177     for i := j + 1; i < len(keys); i++ {
 178         if i > 0 {
 179             w.WriteString(", ")
 180         }
 181         w.WriteString(keys[i])
 182         w.WriteString(": null")
 183     }
 184     w.WriteByte('}')
 185 }
 186 
 187 func loopTSV(line string, f func(i int, s string)) {
 188     for i := 0; len(line) > 0; i++ {
 189         pos := strings.IndexByte(line, '\t')
 190         if pos < 0 {
 191             f(i, line)
 192             return
 193         }
 194 
 195         f(i, line[:pos])
 196         line = line[pos+1:]
 197     }
 198 }
 199 
 200 func handleInput(w *bufio.Writer, r io.Reader, cfg *runConfig) error {
 201     const gb = 1024 * 1024 * 1024
 202     sc := bufio.NewScanner(r)
 203     sc.Buffer(nil, 8*gb)
 204 
 205     for sc.Scan() {
 206         if cfg.lines == 0 {
 207             cfg.keys = escapeKeys(sc.Text())
 208             w.WriteByte('[')
 209             cfg.lines++
 210             continue
 211         }
 212 
 213         if cfg.lines == 1 {
 214             w.WriteString("\n  ")
 215         } else {
 216             if _, err := w.WriteString(",\n  "); err != nil {
 217                 return noMoreOutput{}
 218             }
 219         }
 220 
 221         emitRow(w, sc.Text(), cfg.keys)
 222         cfg.lines++
 223     }
 224 
 225     return sc.Err()
 226 }