Add dot formatter

README.md

@@ -146,6 +146,7 @@ Please parses data structures in the above formats and can output them as:
 
 * bash `declare` syntax
 * YAML
+* dot (graphviz)
 
 If you're not familiar with associative arrays in bash or how `declare` works, it's worth reading the following:
 
@@ -195,3 +196,7 @@ Making use of the bash-declare output format
 
     $ echo '{"json": ["array", "values"]}' | please parse json | (declare -A data=$(cat -); echo ${data[1]})
     values
+
+Generating a graph from some json (you need graphviz installed)
+
+    $ echo '{"vars": ["foo", "bar", "baz"], "cake": {"is_lie": true}}' | please parse -o dot | dot -Tpng > graph.png

cmd/parse.go

@@ -49,6 +49,7 @@ func init() {
 	formatters = map[string]func(interface{}, string) string{
 		"bash": formatter.Bash,
 		"yaml": formatter.Yaml,
+		"dot":  formatter.Dot,
 	}
 }
 

formatter/dot.go

@@ -0,0 +1,155 @@
+package formatter
+
+import (
+	"bytes"
+	"fmt"
+	"os"
+	"reflect"
+	"strconv"
+	"strings"
+)
+
+type node struct {
+	name  string
+	label string
+}
+
+type link struct {
+	left  string
+	right string
+}
+
+func wrap(in string) string {
+	out := strings.Replace(in, "\\", "\\\\", -1)
+	out = strings.Replace(out, "\"", "\\\"", -1)
+	out = strings.Replace(out, "\n", "\\n", -1)
+	out = fmt.Sprintf("\"%s\"", out)
+
+	return out
+}
+
+func Dot(in interface{}, path string) (out string) {
+	nodes, links := flatten(in, path, "root")
+
+	nodes = append(nodes, node{
+		name:  "root",
+		label: "[Root]",
+	})
+
+	var buf bytes.Buffer
+
+	for _, node := range nodes {
+		buf.WriteString(fmt.Sprintf("%s [label=%s];\n", wrap(node.name), wrap(node.label)))
+	}
+
+	for _, link := range links {
+		buf.WriteString(fmt.Sprintf("%s -- %s;\n", wrap(link.left), wrap(link.right)))
+	}
+
+	return fmt.Sprintf("graph{\n%s}", buf.String())
+}
+
+func flatten(in interface{}, path string, current_path string) ([]node, []link) {
+	var nodes []node
+	var links []link
+
+	if in == nil {
+		return nodes, links
+	}
+
+	val := reflect.ValueOf(in)
+
+	split_path := strings.SplitN(path, ".", 2)
+
+	this_path := split_path[0]
+	var next_path string
+
+	if len(split_path) > 1 {
+		next_path = split_path[1]
+	}
+
+	switch val.Kind() {
+	case reflect.Map:
+		vv := in.(map[string]interface{})
+
+		if this_path != "" {
+			if _, ok := vv[this_path]; !ok {
+				fmt.Fprintf(os.Stderr, "Key does not exist: %s\n", this_path)
+				os.Exit(1)
+			}
+
+			return flatten(vv[this_path], next_path, this_path)
+		}
+
+		for key, value := range vv {
+			target := current_path + "-" + key
+
+			nodes = append(nodes, node{
+				name:  target,
+				label: key,
+			})
+
+			if current_path != "" {
+				links = append(links, link{
+					left:  current_path,
+					right: target,
+				})
+			}
+
+			new_nodes, new_links := flatten(value, path, target)
+
+			nodes = append(nodes, new_nodes...)
+			links = append(links, new_links...)
+		}
+
+		return nodes, links
+	case reflect.Array, reflect.Slice:
+		if this_path != "" {
+			index, err := strconv.Atoi(this_path)
+
+			if err != nil || index < 0 || index >= val.Len() {
+				fmt.Fprintf(os.Stderr, "Key does not exist: %s\n", this_path)
+				os.Exit(1)
+			}
+
+			return flatten(val.Index(index).Interface(), next_path, this_path)
+		}
+
+		for index := 0; index < val.Len(); index++ {
+			value := val.Index(index).Interface()
+
+			target := current_path + "-" + fmt.Sprint(index)
+
+			nodes = append(nodes, node{
+				name:  target,
+				label: fmt.Sprintf("[%d]", index),
+			})
+
+			if current_path != "" {
+				links = append(links, link{
+					left:  current_path,
+					right: target,
+				})
+			}
+
+			new_nodes, new_links := flatten(value, path, target)
+
+			nodes = append(nodes, new_nodes...)
+			links = append(links, new_links...)
+		}
+
+		return nodes, links
+	default:
+		if this_path != "" {
+			fmt.Fprintf(os.Stderr, "Key does not exist: %s\n", this_path)
+			os.Exit(1)
+		}
+
+		links = append(links, link{
+			left:  current_path,
+			right: fmt.Sprint(in),
+		})
+
+		return nodes, links
+	}
+}