Change the interface of the PullRequest resource to be more granular.

Currently the PullRequest resource produces one large json object representing the
entire PR. This works, but makes it harder to write simple programs to manipulate this
object.

This commit changes this interface to produce a set of files, each representing a part
of the initial pull request. This makes it easier for programs to do simple tasks like add
labels or comments.

Author: dlorenc

cmd/pullrequest-init/disk.go

@@ -0,0 +1,178 @@
+/*
+Copyright 2019 The Tekton Authors
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package main
+
+import (
+	"encoding/json"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"strconv"
+)
+
+// This file contains functions used to write a PR to disk. The representation is as follows:
+
+// /workspace/
+// /workspace/<resource>/
+// /workspace/<resource>/labels/
+// /workspace/<resource>/labels/<label>
+// /workspace/<resource>/status/
+// /workspace/<resource>/status/<status>
+// /workspace/<resource>/comments/
+// /workspace/<resource>/comments/<comment>
+// /workspace/<resource>/head
+// /workspace/<resource>/base
+
+// ToDisk converts a PullRequest object to an on-disk representation at the specified path.
+func ToDisk(pr *PullRequest, path string) error {
+	labelsPath := filepath.Join(path, "labels")
+	commentsPath := filepath.Join(path, "comments")
+	statusesPath := filepath.Join(path, "status")
+
+	// Setup subdirs
+	for _, p := range []string{labelsPath, commentsPath, statusesPath} {
+		if err := os.MkdirAll(p, 0755); err != nil {
+			return err
+		}
+	}
+
+	// Start with comments
+	for _, c := range pr.Comments {
+		commentPath := filepath.Join(commentsPath, strconv.FormatInt(c.ID, 10))
+		b, err := json.Marshal(c)
+		if err != nil {
+			return err
+		}
+		if err := ioutil.WriteFile(commentPath, b, 0700); err != nil {
+			return err
+		}
+	}
+
+	// Now labels
+	for _, l := range pr.Labels {
+		labelPath := filepath.Join(labelsPath, l.Text)
+		if err := ioutil.WriteFile(labelPath, []byte{}, 0700); err != nil {
+			return err
+		}
+	}
+
+	// Now status
+	for _, s := range pr.Statuses {
+		statusPath := filepath.Join(statusesPath, s.ID)
+		b, err := json.Marshal(s)
+		if err != nil {
+			return err
+		}
+		if err := ioutil.WriteFile(statusPath, b, 0700); err != nil {
+			return err
+		}
+	}
+
+	// Now refs
+	writeRef := func(name string, r *GitReference) error {
+		b, err := json.Marshal(r)
+		if err != nil {
+			return err
+		}
+		return ioutil.WriteFile(filepath.Join(path, name), b, 0700)
+	}
+
+	if err := writeRef("head", pr.Head); err != nil {
+		return err
+	}
+	if err := writeRef("base", pr.Base); err != nil {
+		return err
+	}
+	return nil
+}
+
+// FromDisk outputs a PullRequest object from an on-disk representation at the specified path.
+func FromDisk(path string) (*PullRequest, error) {
+	labelsPath := filepath.Join(path, "labels")
+	commentsPath := filepath.Join(path, "comments")
+	statusesPath := filepath.Join(path, "status")
+
+	pr := PullRequest{}
+
+	// Start with comments
+	fis, err := ioutil.ReadDir(commentsPath)
+	if err != nil {
+		return nil, err
+	}
+	for _, fi := range fis {
+		b, err := ioutil.ReadFile(filepath.Join(commentsPath, fi.Name()))
+		if err != nil {
+			return nil, err
+		}
+		comment := Comment{}
+		if err := json.Unmarshal(b, &comment); err != nil {
+			return nil, err
+		}
+		pr.Comments = append(pr.Comments, &comment)
+	}
+
+	// Now Labels
+	fis, err = ioutil.ReadDir(labelsPath)
+	if err != nil {
+		return nil, err
+	}
+	for _, fi := range fis {
+		label := Label{fi.Name()}
+		pr.Labels = append(pr.Labels, &label)
+	}
+
+	// Now statuses
+	fis, err = ioutil.ReadDir(statusesPath)
+	if err != nil {
+		return nil, err
+	}
+
+	for _, fi := range fis {
+		b, err := ioutil.ReadFile(filepath.Join(statusesPath, fi.Name()))
+		if err != nil {
+			return nil, err
+		}
+		status := Status{}
+		if err := json.Unmarshal(b, &status); err != nil {
+			return nil, err
+		}
+		pr.Statuses = append(pr.Statuses, &status)
+	}
+
+	// Finally refs
+	readRef := func(name string) (*GitReference, error) {
+		b, err := ioutil.ReadFile(filepath.Join(path, name))
+		if err != nil {
+			return nil, err
+		}
+		ref := GitReference{}
+		if err := json.Unmarshal(b, &ref); err != nil {
+			return nil, err
+		}
+		return &ref, nil
+	}
+
+	pr.Base, err = readRef("base")
+	if err != nil {
+		return nil, err
+	}
+	pr.Head, err = readRef("head")
+	if err != nil {
+		return nil, err
+	}
+	return &pr, nil
+}