Move some request parsing into hook package

Trying to simplify hookHandler.  No functional changes introduced.

internal/hook/request.go

@@ -0,0 +1,116 @@
+package hook
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"net/url"
+	"unicode"
+
+	"github.com/clbanning/mxj"
+)
+
+// Request represents a webhook request.
+type Request struct {
+	// The request ID set by the RequestID middleware.
+	ID string
+
+	// The Content-Type of the request.
+	ContentType string
+
+	// The raw request body.
+	Body []byte
+
+	// Headers is a map of the parsed headers.
+	Headers map[string]interface{}
+
+	// Query is a map of the parsed URL query values.
+	Query map[string]interface{}
+
+	// Payload is a map of the parsed payload.
+	Payload map[string]interface{}
+
+	// The underlying HTTP request.
+	RawRequest *http.Request
+}
+
+func (r *Request) ParseJSONPayload() error {
+	decoder := json.NewDecoder(bytes.NewReader(r.Body))
+	decoder.UseNumber()
+
+	var firstChar byte
+	for i := 0; i < len(r.Body); i++ {
+		if unicode.IsSpace(rune(r.Body[i])) {
+			continue
+		}
+		firstChar = r.Body[i]
+		break
+	}
+
+	if firstChar == byte('[') {
+		var arrayPayload interface{}
+		err := decoder.Decode(&arrayPayload)
+		if err != nil {
+			return fmt.Errorf("error parsing JSON array payload %+v", err)
+		}
+
+		r.Payload = make(map[string]interface{}, 1)
+		r.Payload["root"] = arrayPayload
+	} else {
+		err := decoder.Decode(&r.Payload)
+		if err != nil {
+			return fmt.Errorf("error parsing JSON payload %+v", err)
+		}
+	}
+
+	return nil
+}
+
+func (r *Request) ParseHeaders(headers map[string][]string) {
+	r.Headers = make(map[string]interface{}, len(headers))
+
+	for k, v := range headers {
+		if len(v) > 0 {
+			r.Headers[k] = v[0]
+		}
+	}
+}
+
+func (r *Request) ParseQuery(query map[string][]string) {
+	r.Query = make(map[string]interface{}, len(query))
+
+	for k, v := range query {
+		if len(v) > 0 {
+			r.Query[k] = v[0]
+		}
+	}
+}
+
+func (r *Request) ParseFormPayload() error {
+	fd, err := url.ParseQuery(string(r.Body))
+	if err != nil {
+		return fmt.Errorf("error parsing form payload %+v", err)
+	}
+
+	r.Payload = make(map[string]interface{}, len(fd))
+
+	for k, v := range fd {
+		if len(v) > 0 {
+			r.Payload[k] = v[0]
+		}
+	}
+
+	return nil
+}
+
+func (r *Request) ParseXMLPayload() error {
+	var err error
+
+	r.Payload, err = mxj.NewMapXmlReader(bytes.NewReader(r.Body))
+	if err != nil {
+		return fmt.Errorf("error parsing XML payload: %+v", err)
+	}
+
+	return nil
+}