adds a basic CLI

cmd/jsonpath/main.go

@@ -0,0 +1,87 @@
+// Package main implements a simple command-line utility that allows one to extract
+// data from an arbitrary JSON body that has been piped into it.
+package main
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io"
+	"os"
+	"runtime/debug"
+
+	"github.com/theory/jsonpath"
+	"github.com/urfave/cli/v2"
+)
+
+func main() {
+	app := &cli.App{
+		Name:      "jsonpath",
+		Usage:     "extracting data from JSON according to RFC-9535",
+		UsageText: "jsonpath QUERY",
+		Version:   gitrev(),
+		Action:    parseAndPrint,
+		Args:      true,
+	}
+
+	if err := app.Run(os.Args); err != nil {
+		fmt.Fprint(os.Stderr, err.Error()+"\n")
+		os.Exit(1)
+	}
+}
+
+func gitrev() string {
+	version := "(git revision unavailable)"
+
+	if bi, ok := debug.ReadBuildInfo(); ok {
+		for _, kv := range bi.Settings {
+			if kv.Key == "vcs.revision" {
+				version = kv.Value
+			}
+		}
+	}
+
+	return version
+}
+
+func parseAndPrint(ctx *cli.Context) error {
+	// grab the provided jsonpath query
+	q := ctx.Args().First()
+	if q == "" {
+		cli.ShowAppHelpAndExit(ctx, 1)
+	}
+	p := jsonpath.NewParser().MustParse(q)
+
+	m, err := jsonToMap(os.Stdin)
+	if err != nil {
+		return fmt.Errorf("could not read JSON body from stdin: %w", err)
+	}
+
+	// apply q to map
+	result := p.Select(m)
+
+	// dump to output
+	items, err := json.Marshal(result)
+	if err != nil {
+		return fmt.Errorf("could not marshal results to JSON: %w", err)
+	}
+	fmt.Printf("%s\n", items) //nolint:forbidigo
+
+	return nil
+}
+
+func jsonToMap(r io.Reader) (map[string]any, error) {
+	b, err := io.ReadAll(r)
+	if err != nil {
+		return nil, fmt.Errorf("could not read JSON contents: %w", err)
+	}
+
+	decoder := json.NewDecoder(bytes.NewReader(b))
+	var m map[string]any
+	err = decoder.Decode(&m)
+	if err != nil {
+		return nil, fmt.Errorf("could not decode JSON to map: %w", err)
+	}
+
+	return m, nil
+}

go.mod

@@ -2,13 +2,19 @@ module github.com/theory/jsonpath
 
 go 1.23
 
-require github.com/stretchr/testify v1.10.0
+require (
+	github.com/stretchr/testify v1.10.0
+	github.com/urfave/cli/v2 v2.27.5
+)
 
 require (
+	github.com/cpuguy83/go-md2man/v2 v2.0.5 // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/kr/pretty v0.3.0 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/rogpeppe/go-internal v1.12.0 // indirect
+	github.com/russross/blackfriday/v2 v2.1.0 // indirect
+	github.com/xrash/smetrics v0.0.0-20240521201337-686a1a2994c1 // indirect
 	gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

go.sum

@@ -1,3 +1,5 @@
+github.com/cpuguy83/go-md2man/v2 v2.0.5 h1:ZtcqGrnekaHpVLArFSe4HK5DoKx1T0rq2DwVB0alcyc=
+github.com/cpuguy83/go-md2man/v2 v2.0.5/go.mod h1:tgQtvFlXSQOSOSIRvRPT7W67SCa46tRHOmNcaadrF8o=
 github.com/creack/pty v1.1.9/go.mod h1:oKZEueFk5CKHvIhNR5MUki03XCEU+Q6VDXinZuGJ33E=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
@@ -14,8 +16,14 @@ github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZN
 github.com/rogpeppe/go-internal v1.6.1/go.mod h1:xXDCJY+GAPziupqXw64V24skbSoqbTEfhy4qGm1nDQc=
 github.com/rogpeppe/go-internal v1.12.0 h1:exVL4IDcn6na9z1rAb56Vxr+CgyK3nn3O+epU5NdKM8=
 github.com/rogpeppe/go-internal v1.12.0/go.mod h1:E+RYuTGaKKdloAfM02xzb0FW3Paa99yedzYV+kq4uf4=
+github.com/russross/blackfriday/v2 v2.1.0 h1:JIOH55/0cWyOuilr9/qlrm0BSXldqnqwMsf35Ld67mk=
+github.com/russross/blackfriday/v2 v2.1.0/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQDYRxCVz55jmeOWTM=
 github.com/stretchr/testify v1.10.0 h1:Xv5erBjTwe/5IxqUQTdXv5kgmIvbHo3QQyRwhJsOfJA=
 github.com/stretchr/testify v1.10.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
+github.com/urfave/cli/v2 v2.27.5 h1:WoHEJLdsXr6dDWoJgMq/CboDmyY/8HMMH1fTECbih+w=
+github.com/urfave/cli/v2 v2.27.5/go.mod h1:3Sevf16NykTbInEnD0yKkjDAeZDS0A6bzhBH5hrMvTQ=
+github.com/xrash/smetrics v0.0.0-20240521201337-686a1a2994c1 h1:gEOO8jv9F4OT7lGCjxCBTO/36wtF6j2nSip77qHd4x4=
+github.com/xrash/smetrics v0.0.0-20240521201337-686a1a2994c1/go.mod h1:Ohn+xnUBiLI6FVj/9LpzZWtj1/D6lUovWYBkxHVV3aM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c h1:Hei/4ADfdWqJk1ZMxUNpqntNwaWcugrBjAiHlqqRiVk=