Basic GitHub filesystem support

A gateway to proper filesystem builtins needed for #53.

go.mod

@@ -19,6 +19,7 @@ require (
 	github.com/go-test/deep v1.0.7
 	github.com/gogo/protobuf v1.3.1 // indirect
 	github.com/golang/protobuf v1.4.2
+	github.com/google/go-github/v32 v32.1.0
 	github.com/google/uuid v1.1.1
 	github.com/gorilla/mux v1.7.4 // indirect
 	github.com/grpc-ecosystem/go-grpc-middleware v1.2.0

go.sum

@@ -118,6 +118,10 @@ github.com/google/go-cmp v0.4.0 h1:xsAVV57WRhGj6kEIi8ReJzQlHHqcBYCElAvkovg3B/4=
 github.com/google/go-cmp v0.4.0/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/google/go-cmp v0.5.0 h1:/QaMHBdZ26BB3SSst0Iwl10Epc+xhTquomWX0oZEB6w=
 github.com/google/go-cmp v0.5.0/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
+github.com/google/go-github/v32 v32.1.0 h1:GWkQOdXqviCPx7Q7Fj+KyPoGm4SwHRh8rheoPhd27II=
+github.com/google/go-github/v32 v32.1.0/go.mod h1:rIEpZD9CTDQwDK9GDrtMTycQNA4JU3qBsCizh3q2WCI=
+github.com/google/go-querystring v1.0.0 h1:Xkwi/a1rcvNg1PPYe5vI8GbeBY/jrVuDX5ASuANWTrk=
+github.com/google/go-querystring v1.0.0/go.mod h1:odCYkC5MyYFN7vkCjXpyrEuKhc/BUO6wN/zVPAxq5ck=
 github.com/google/uuid v1.1.1 h1:Gkbcsh/GbpXz7lPftLA3P6TYMwjCLYm83jiFQZF/3gY=
 github.com/google/uuid v1.1.1/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
 github.com/gorilla/mux v1.7.4 h1:VuZ8uybHlWmqV03+zRzdwKL4tUnIp1MAQtp1mIFE1bc=

pkg/larker/fs/fs.go

@@ -1,6 +1,8 @@
 package fs
 
-import "context"
+import (
+	"context"
+)
 
 type FileSystem interface {
 	Get(ctx context.Context, path string) ([]byte, error)

pkg/larker/fs/github/github.go

@@ -0,0 +1,51 @@
+package github
+
+import (
+	"context"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"github.com/google/go-github/v32/github"
+	"syscall"
+)
+
+var ErrAPI = errors.New("failed to communicate with the GitHub API")
+
+type GitHub struct {
+	client    *github.Client
+	owner     string
+	repo      string
+	reference string
+}
+
+func New(owner, repo, reference, token string) *GitHub {
+	return &GitHub{
+		client:    github.NewClient(nil),
+		owner:     owner,
+		repo:      repo,
+		reference: reference,
+	}
+}
+
+func (gh *GitHub) Get(ctx context.Context, path string) ([]byte, error) {
+	fileContent, _, _, err := gh.client.Repositories.GetContents(ctx, gh.owner, gh.repo, path,
+		&github.RepositoryContentGetOptions{
+			Ref: gh.reference,
+		},
+	)
+	if err != nil {
+		return nil, fmt.Errorf("%w: %v", ErrAPI, err)
+	}
+
+	// Simulate os.Read() behavior in case the supplied path points to a directory
+	if fileContent == nil {
+		return nil, syscall.EISDIR
+	}
+
+	fileBytes, err := base64.StdEncoding.DecodeString(*fileContent.Content)
+	if err != nil {
+		return nil, fmt.Errorf("%w: %v", ErrAPI, err)
+	}
+
+	return fileBytes, nil
+}

pkg/larker/fs/github/github_test.go

@@ -0,0 +1,32 @@
+package github_test
+
+import (
+	"context"
+	"errors"
+	"github.com/cirruslabs/cirrus-cli/pkg/larker/fs"
+	"github.com/cirruslabs/cirrus-cli/pkg/larker/fs/github"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"syscall"
+	"testing"
+)
+
+func selfFS() fs.FileSystem {
+	return github.New("cirruslabs", "cirrus-cli", "master", "")
+}
+
+func TestGetFile(t *testing.T) {
+	fileBytes, err := selfFS().Get(context.Background(), "go.mod")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	assert.Contains(t, string(fileBytes), "module github.com/cirruslabs/cirrus-cli")
+}
+
+func TestGetDirectory(t *testing.T) {
+	_, err := selfFS().Get(context.Background(), ".")
+
+	require.Error(t, err)
+	assert.True(t, errors.Is(err, syscall.EISDIR))
+}

pkg/larker/fs/local/local_test.go

@@ -0,0 +1,39 @@
+package local_test
+
+import (
+	"context"
+	"errors"
+	"github.com/cirruslabs/cirrus-cli/internal/testutil"
+	"github.com/cirruslabs/cirrus-cli/pkg/larker/fs/local"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"io/ioutil"
+	"path/filepath"
+	"syscall"
+	"testing"
+)
+
+func TestGetFile(t *testing.T) {
+	// Prepare temporary directory
+	dir := testutil.TempDir(t)
+	if err := ioutil.WriteFile(filepath.Join(dir, "some-file.txt"), []byte("some-contents"), 0600); err != nil {
+		t.Fatal(err)
+	}
+
+	fileBytes, err := local.New(dir).Get(context.Background(), "some-file.txt")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	assert.Contains(t, string(fileBytes), "some-contents")
+}
+
+func TestGetDirectory(t *testing.T) {
+	// Prepare temporary directory
+	dir := testutil.TempDir(t)
+
+	_, err := local.New(dir).Get(context.Background(), ".")
+
+	require.Error(t, err)
+	assert.True(t, errors.Is(err, syscall.EISDIR))
+}