Refactor to remove helpers package

This commit removes the "helpers" package by moving functions from the
package into the other packages that use them.

CheckPayloadSignature() and ExtractParamater() are simply moved to the
"hook" package.  I'm not sure of the usefulness of having these
functions exported, but I left them allow for now.

ValuesToMap() is moved to the "main" webhook package and renamed to
valuesToMap().

Tests were moved into the "hook" package since we only test
ExtractParameter() right now.

This commit closes adnanh/webhook#12.

hook/hook.go

@@ -1,12 +1,17 @@
 package hook
 
 import (
+	"crypto/hmac"
+	"crypto/sha1"
+	"encoding/hex"
 	"encoding/json"
+	"fmt"
 	"io/ioutil"
 	"log"
+	"reflect"
 	"regexp"
-
-	"github.com/adnanh/webhook/helpers"
+	"strconv"
+	"strings"
 )
 
 // Constants used to specify the parameter source
@@ -16,6 +21,57 @@ const (
 	SourcePayload string = "payload"
 )
 
+// CheckPayloadSignature calculates and verifies SHA1 signature of the given payload
+func CheckPayloadSignature(payload []byte, secret string, signature string) (string, bool) {
+	if strings.HasPrefix(signature, "sha1=") {
+		signature = signature[5:]
+	}
+
+	mac := hmac.New(sha1.New, []byte(secret))
+	mac.Write(payload)
+	expectedMAC := hex.EncodeToString(mac.Sum(nil))
+
+	return expectedMAC, hmac.Equal([]byte(signature), []byte(expectedMAC))
+}
+
+// ExtractParameter extracts value from interface{} based on the passed string
+func ExtractParameter(s string, params interface{}) (string, bool) {
+	if params == nil {
+		return "", false
+	}
+
+	if paramsValue := reflect.ValueOf(params); paramsValue.Kind() == reflect.Slice {
+		if paramsValueSliceLength := paramsValue.Len(); paramsValueSliceLength > 0 {
+
+			if p := strings.SplitN(s, ".", 2); len(p) > 1 {
+				index, err := strconv.ParseInt(p[0], 10, 64)
+
+				if err != nil {
+					return "", false
+				} else if paramsValueSliceLength <= int(index) {
+					return "", false
+				}
+
+				return ExtractParameter(p[1], params.([]interface{})[index])
+			}
+		}
+
+		return "", false
+	}
+
+	if p := strings.SplitN(s, ".", 2); len(p) > 1 {
+		if pValue, ok := params.(map[string]interface{})[p[0]]; ok {
+			return ExtractParameter(p[1], pValue)
+		}
+	} else {
+		if pValue, ok := params.(map[string]interface{})[p[0]]; ok {
+			return fmt.Sprintf("%v", pValue), true
+		}
+	}
+
+	return "", false
+}
+
 // Argument type specifies the parameter key name and the source it should
 // be extracted from
 type Argument struct {
@@ -38,7 +94,7 @@ func (ha *Argument) Get(headers, query, payload *map[string]interface{}) (string
 	}
 
 	if source != nil {
-		return helpers.ExtractParameter(ha.Name, *source)
+		return ExtractParameter(ha.Name, *source)
 	}
 
 	return "", false
@@ -201,7 +257,7 @@ func (r MatchRule) Evaluate(headers, query, payload *map[string]interface{}, bod
 			}
 			return ok
 		case MatchHashSHA1:
-			expected, ok := helpers.CheckPayloadSignature(*body, r.Secret, arg)
+			expected, ok := CheckPayloadSignature(*body, r.Secret, arg)
 			if !ok {
 				log.Printf("payload signature mismatch, expected %s got %s", expected, arg)
 			}

hook/hook_test.go

@@ -0,0 +1,29 @@
+package hook
+
+import "testing"
+
+var extractParameterTests = []struct {
+	s      string
+	params map[string]interface{}
+	value  string
+	ok     bool
+}{
+	{"a", map[string]interface{}{"a": "z"}, "z", true},
+	{"a.b", map[string]interface{}{"a": map[string]interface{}{"b": "z"}}, "z", true},
+	{"a.b.c", map[string]interface{}{"a": map[string]interface{}{"b": map[string]interface{}{"c": "z"}}}, "z", true},
+	{"a.1.b", map[string]interface{}{"a": []interface{}{map[string]interface{}{"b": "y"}, map[string]interface{}{"b": "z"}}}, "z", true},
+	{"a.1.b.c", map[string]interface{}{"a": []interface{}{map[string]interface{}{"b": map[string]interface{}{"c": "y"}}, map[string]interface{}{"b": map[string]interface{}{"c": "z"}}}}, "z", true},
+	// failures
+	{"a.X", map[string]interface{}{"a": map[string]interface{}{"b": "z"}}, "", false},
+	{"a.500.b", map[string]interface{}{"a": map[string]interface{}{"b": "z"}}, "", false},
+	{"a.501.b", map[string]interface{}{"a": []interface{}{map[string]interface{}{"b": "y"}, map[string]interface{}{"b": "z"}}}, "", false},
+}
+
+func TestExtractParameter(t *testing.T) {
+	for _, tt := range extractParameterTests {
+		s, ok := ExtractParameter(tt.s, tt.params)
+		if ok != tt.ok || s != tt.value {
+			t.Errorf("failed to extract parameter %q:\nexpected {value:%#v, ok:%#v},\ngot {value:%#v, ok:%#v}", tt.s, tt.value, tt.ok, s, ok)
+		}
+	}
+}