support for image pull logs

internal/docker/jsonmessage/jsonmessage.go

@@ -0,0 +1,61 @@
+// Copyright 2019 Drone.IO Inc. All rights reserved.
+// Use of this source code is governed by the Polyform License
+// that can be found in the LICENSE file.
+
+package jsonmessage
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+)
+
+type jsonError struct {
+	Code    int    `json:"code"`
+	Message string `json:"message"`
+}
+
+func (e *jsonError) Error() string {
+	return e.Message
+}
+
+type jsonMessage struct {
+	ID       string        `json:"id"`
+	Status   string        `json:"status"`
+	Error    *jsonError    `json:"errorDetail"`
+	Progress *jsonProgress `json:"progressDetail"`
+}
+
+type jsonProgress struct {
+}
+
+// Copy copies a json message string to the io.Writer.
+func Copy(in io.Reader, out io.Writer) error {
+	dec := json.NewDecoder(in)
+	for {
+		var jm jsonMessage
+		if err := dec.Decode(&jm); err != nil {
+			if err == io.EOF {
+				break
+			}
+			return err
+		}
+
+		if jm.Error != nil {
+			if jm.Error.Code == 401 {
+				return fmt.Errorf("authentication is required")
+			}
+			return jm.Error
+		}
+
+		if jm.Progress != nil {
+			continue
+		}
+		if jm.ID == "" {
+			fmt.Fprintf(out, "%s\n", jm.Status)
+		} else {
+			fmt.Fprintf(out, "%s: %s\n", jm.ID, jm.Status)
+		}
+	}
+	return nil
+}

internal/docker/jsonmessage/testdata/alpine.json

@@ -0,0 +1,12 @@
+{"status":"Pulling from library/alpine","id":"3.6"}
+{"status":"Pulling fs layer","progressDetail":{},"id":"5a3ea8efae5d"}
+{"status":"Downloading","progressDetail":{"current":21019,"total":2017774},"progress":"[\u003e                                                  ]  21.02kB/2.018MB","id":"5a3ea8efae5d"}
+{"status":"Downloading","progressDetail":{"current":1194721,"total":2017774},"progress":"[=============================\u003e                     ]  1.195MB/2.018MB","id":"5a3ea8efae5d"}
+{"status":"Verifying Checksum","progressDetail":{},"id":"5a3ea8efae5d"}
+{"status":"Download complete","progressDetail":{},"id":"5a3ea8efae5d"}
+{"status":"Extracting","progressDetail":{"current":32768,"total":2017774},"progress":"[\u003e                                                  ]  32.77kB/2.018MB","id":"5a3ea8efae5d"}
+{"status":"Extracting","progressDetail":{"current":786432,"total":2017774},"progress":"[===================\u003e                               ]  786.4kB/2.018MB","id":"5a3ea8efae5d"}
+{"status":"Extracting","progressDetail":{"current":2017774,"total":2017774},"progress":"[==================================================\u003e]  2.018MB/2.018MB","id":"5a3ea8efae5d"}
+{"status":"Pull complete","progressDetail":{},"id":"5a3ea8efae5d"}
+{"status":"Digest: sha256:66790a2b79e1ea3e1dabac43990c54aca5d1ddf268d9a5a0285e4167c8b24475"}
+{"status":"Status: Downloaded newer image for alpine:3.6"}