Ship call logs to the user as text/plain instead of JSON (#615)

* Ship call logs to the user as text/plain instead of JSON

* Fixing swagger doc

* c.String instead of c.JSON

* Make Logs API backward compatible

* Loop over accepted MIME types

* Bump swagger API version

* Fix client build script

 previous version was producing the following "couldn't find a swagger spec"

* Logs API regression test

* Write response body without buffering

* Switch JSON and text/plain cases

* Handle Accepted content types properly

* More solid response content type handling

* Write HTTP 406 with corresponding error body

* Remove unused import

* Use handleErrorResponse

api/server/call_logs.go

@@ -2,13 +2,33 @@ package server
 
 import (
 	"bytes"
+	"io"
 	"net/http"
 
+	"errors"
 	"github.com/fnproject/fn/api"
 	"github.com/fnproject/fn/api/models"
 	"github.com/gin-gonic/gin"
+	"strings"
 )
 
+// note: for backward compatibility, will go away later
+type callLogResponse struct {
+	Message string          `json:"message"`
+	Log     *models.CallLog `json:"log"`
+}
+
+func writeJSON(c *gin.Context, callID, appName string, logReader io.Reader) {
+	var b bytes.Buffer
+	b.ReadFrom(logReader)
+	c.JSON(http.StatusOK, callLogResponse{"Successfully loaded log",
+		&models.CallLog{
+			CallID:  callID,
+			AppName: appName,
+			Log:     b.String(),
+		}})
+}
+
 func (s *Server) handleCallLogGet(c *gin.Context) {
 	ctx := c.Request.Context()
 
@@ -21,18 +41,30 @@ func (s *Server) handleCallLogGet(c *gin.Context) {
 		return
 	}
 
-	// TODO this API needs to change to text/plain / gzip anyway, punting
-	// optimization, but we can write this direct to the wire, too... seems like
-	// we should write some kind of writev json thing for go since we keep
-	// hitting this :(
-	var b bytes.Buffer
-	b.ReadFrom(logReader)
+	mimeTypes, _ := c.Request.Header["Accept"]
 
-	callObj := models.CallLog{
-		CallID:  callID,
-		AppName: appName,
-		Log:     b.String(),
+	if len(mimeTypes) == 0 {
+		writeJSON(c, callID, appName, logReader)
+		return
 	}
 
-	c.JSON(http.StatusOK, callLogResponse{"Successfully loaded log", &callObj})
+	for _, mimeType := range mimeTypes {
+		if strings.Contains(mimeType, "application/json") {
+			writeJSON(c, callID, appName, logReader)
+			return
+		}
+		if strings.Contains(mimeType, "text/plain") {
+			io.Copy(c.Writer, logReader)
+			return
+
+		}
+		if strings.Contains(mimeType, "*/*") {
+			writeJSON(c, callID, appName, logReader)
+			return
+		}
+	}
+
+	// if we've reached this point it means that Fn didn't recognize Accepted content type
+	handleErrorResponse(c, models.NewAPIError(http.StatusNotAcceptable,
+		errors.New("unable to respond within acceptable response content types")))
 }