sm-json.go

/*

  NAME

  sm-json - find variable in json file

  SYNOPSIS

  sm-json [options]

  OPTIONS
    -path="{path}"        path to retrieve value from
    -path|--path "{path}" path to retrieve value from
    -uri="{uri}"          json uri (url or path to file)
    -uri|--uri "{uri}"    json uri (url or path to file)

  DESCRIPTION

  Opens a json file from --uri and returns the value found at the given --path

*/

package main

import (
	"bufio"
	"encoding/json"
	"flag"
	"fmt"
	"io/ioutil"
	"log"
	"os"
	"strings"
)

var path = flag.String("path", "{path}", "path of variable")
var uri = flag.String("uri", "{uri}", "json uri or path to file")
var f map[string]interface{}
var value string

func find_value(key []string, data map[string]interface{}, index int) string {
	switch v := data[key[index]].(type) {
	case string:
		return v
	case map[string]interface{}:
		return find_value(key, v, index+1)
	default:
		log.Fatal("ERROR: Error with value ", v)
	}
	return ""
}

func find_map_value(data map[string]interface{}) string {
	var my_val string
	for key, val := range data {
		my_val += key + " " + val.(string) + " "
	}
	return my_val
}

func main() {

	flag.Parse()

	if *uri == "{uri}" {
		log.Fatal("ERROR: A json file location must be specified for reading using --uri={{uri}}")
	} else {
		file, err := os.Open(*uri)
		if err != nil {
			log.Fatalf("ERROR: The json file at '%s' cannot be opened", *uri)
		}

		bfile := bufio.NewReader(file)
		buf, err := ioutil.ReadAll(bfile)
		if file == nil && err != nil {
			log.Fatalf("ERROR: A json does not exist at '%s'", *uri)
		}

		json_err := json.Unmarshal(buf, &f)

		if json_err != nil {
			log.Fatalf("ERROR: Unable to parse json file located at '%s'", *uri)
		}

		// Parse path
		path_array := strings.Split(*path, "/")
		for i := range path_array {
			switch v := f[path_array[i]].(type) {
			case string:
				if len(path_array) == i+1 {
					value = v
				} else {
					log.Fatalf("ERROR: Unable to traverse the full path before encoutering a value at '%s'.", v)
				}
			case map[string]interface{}:
				if len(path_array) == i+1 {
					value = find_map_value(v)
				} else {
					value = find_value(path_array, v, i+1)
				}
				break
			case []interface{}:
				// @TODO make implementation better
				for index, data := range v {
					switch mapped_data := data.(type) {
					case map[string]interface{}:
						value += find_map_value(mapped_data)
					default:
						// @TODO: A more informative error message here.
						log.Fatal("ERROR: Data is not correct on index ", index)
					}
				}
			default:
			}
			if len(value) > 0 {
				break
			}
		}

		fmt.Println(value)
	}
}