Add functions

README.md

@@ -95,6 +95,25 @@ If no `<dest>` file is specified, the output is sent to stdout.  Mainly useful f
 
 ===
 
+### Templating
+
+The templates used by nginx-proxy are written the Go [text/template](http://golang.org/pkg/text/template/) language. In addition to the [built-in functions](http://golang.org/pkg/text/template/#hdr-Functions) supplied by Go, nginx-proxy provides a number of additional functions to make it simpler (or possible) to generate your desired output.
+
+#### Functions
+
+* *`contains $map $key`*: Returns `true` if `$map` contains `$key`. Takes maps from `string` to `string`.
+* *`exists $path`*: Returns `true` if `$path` refers to an existing file or directory. Takes a string.
+* *`groupBy $containers $fieldPath`*: Groups an array of `RuntimeContainer` instances based on the values of a field path expression `$fieldPath`. A field path expression is a dot-delimited list of map keys or struct member names specifying the path from container to a nested value, which must be a string. Returns a map from the value of the field path expression to an array of containers having that value. Containers that do not have a value for the field path in question are omitted.
+* *`groupByMulti $containers $fieldPath $sep`*: Like `groupBy`, but the string value specified by `$fieldPath` is first split by `$sep` into a list of strings. A container whose `$fieldPath` value contains a list of strings will show up in the map output under each of those strings.
+* *`split $string $sep`*: Splits `$string` into a slice of substrings delimited by `$sep`. Alias for [`strings.Split`](http://golang.org/pkg/strings/#Split)
+* *`replace $string $old $new $count`*: Replaces up to `$count` occurences of `$old` with `$new` in `$string`. Alias for [`strings.Replace`](http://golang.org/pkg/strings/#Replace)
+* *`dict $key $value ...`*: Creates a map from a list of pairs. Each `$key` value must be a `string`, but the `$value` can be any type (or `nil`). Useful for passing more than one value as a pipeline context to subtemplates.
+* *`sha1 $string`*: Returns the hexadecimal representation of the SHA1 hash of `$string`.
+* *`json $value`*: Returns the JSON representation of `$value` as a `string`.
+* *`last $array`*: Returns the last value of an array.
+
+===
+
 ### Examples
 
 * [Automated Nginx Reverse Proxy for Docker](http://jasonwilder.com/blog/2014/03/25/automated-nginx-reverse-proxy-for-docker/)

template.go

@@ -2,11 +2,16 @@ package main
 
 import (
 	"bytes"
+	"crypto/sha1"
+	"encoding/json"
+	"errors"
+	"fmt"
 	"io"
 	"io/ioutil"
 	"log"
 	"os"
 	"path/filepath"
+	"reflect"
 	"strings"
 	"syscall"
 	"text/template"
@@ -56,6 +61,41 @@ func contains(item map[string]string, key string) bool {
 	return false
 }
 
+func dict(values ...interface{}) (map[string]interface{}, error) {
+	if len(values)%2 != 0 {
+		return nil, errors.New("invalid dict call")
+	}
+	dict := make(map[string]interface{}, len(values)/2)
+	for i := 0; i < len(values); i += 2 {
+		key, ok := values[i].(string)
+		if !ok {
+			return nil, errors.New("dict keys must be strings")
+		}
+		dict[key] = values[i+1]
+	}
+	return dict, nil
+}
+
+func hashSha1(input string) string {
+	h := sha1.New()
+	io.WriteString(h, input)
+	return fmt.Sprintf("%x", h.Sum(nil))
+}
+
+func marshalJson(input interface{}) (string, error) {
+	var buf bytes.Buffer
+	enc := json.NewEncoder(&buf)
+	if err := enc.Encode(input); err != nil {
+		return "", err
+	}
+	return strings.TrimSuffix(buf.String(), "\n"), nil
+}
+
+func arrayLast(input interface{}) interface{} {
+	arr := reflect.ValueOf(input)
+	return arr.Index(arr.Len() - 1).Interface()
+}
+
 func generateFile(config Config, containers Context) bool {
 	templatePath := config.Template
 	tmpl, err := template.New(filepath.Base(templatePath)).Funcs(template.FuncMap{
@@ -65,6 +105,10 @@ func generateFile(config Config, containers Context) bool {
 		"groupByMulti": groupByMulti,
 		"split":        strings.Split,
 		"replace":      strings.Replace,
+		"dict":         dict,
+		"sha1":         hashSha1,
+		"json":         marshalJson,
+		"last":         arrayLast,
 	}).ParseFiles(templatePath)
 	if err != nil {
 		log.Fatalf("unable to parse template: %s", err)

template_test.go

@@ -1,6 +1,10 @@
 package main
 
-import "testing"
+import (
+	"bytes"
+	"encoding/json"
+	"testing"
+)
 
 func TestContains(t *testing.T) {
 	env := map[string]string{
@@ -99,3 +103,83 @@ func TestGroupByMulti(t *testing.T) {
 		t.Fatalf("expected 2 got %s", groups["demo3.localhost"][0].ID)
 	}
 }
+
+func TestDict(t *testing.T) {
+	containers := []*RuntimeContainer{
+		&RuntimeContainer{
+			Env: map[string]string{
+				"VIRTUAL_HOST": "demo1.localhost",
+			},
+			ID: "1",
+		},
+		&RuntimeContainer{
+			Env: map[string]string{
+				"VIRTUAL_HOST": "demo1.localhost,demo3.localhost",
+			},
+			ID: "2",
+		},
+		&RuntimeContainer{
+			Env: map[string]string{
+				"VIRTUAL_HOST": "demo2.localhost",
+			},
+			ID: "3",
+		},
+	}
+	d, err := dict("/", containers)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if d["/"] == nil {
+		t.Fatalf("did not find containers in dict: %s", d)
+	}
+	if d["MISSING"] != nil {
+		t.Fail()
+	}
+}
+
+func TestSha1(t *testing.T) {
+	sum := hashSha1("/path")
+	if sum != "4f26609ad3f5185faaa9edf1e93aa131e2131352" {
+		t.Fatal("Incorrect SHA1 sum")
+	}
+}
+
+func TestJson(t *testing.T) {
+	containers := []*RuntimeContainer{
+		&RuntimeContainer{
+			Env: map[string]string{
+				"VIRTUAL_HOST": "demo1.localhost",
+			},
+			ID: "1",
+		},
+		&RuntimeContainer{
+			Env: map[string]string{
+				"VIRTUAL_HOST": "demo1.localhost,demo3.localhost",
+			},
+			ID: "2",
+		},
+		&RuntimeContainer{
+			Env: map[string]string{
+				"VIRTUAL_HOST": "demo2.localhost",
+			},
+			ID: "3",
+		},
+	}
+	output, err := marshalJson(containers)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	buf := bytes.NewBufferString(output)
+	dec := json.NewDecoder(buf)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var decoded []*RuntimeContainer
+	if err := dec.Decode(&decoded); err != nil {
+		t.Fatal(err)
+	}
+	if len(decoded) != len(containers) {
+		t.Fatal("Incorrect unmarshaled container count. Expected %d, got %d.", len(containers), len(decoded))
+	}
+}