feat: update changelog file

changelog.go

@@ -2,45 +2,95 @@ package rp
 
 import (
 	"bytes"
+	_ "embed"
+	"fmt"
 	"html/template"
+	"io"
 	"log"
+	"os"
+	"regexp"
 
 	"github.com/go-git/go-git/v5"
 )
 
+const (
+	ChangelogFile       = "CHANGELOG.md"
+	ChangelogFileBuffer = "CHANGELOG.md.tmp"
+	ChangelogHeader     = "# Changelog"
+)
+
 var (
 	changelogTemplate *template.Template
+
+	headerRegex = regexp.MustCompile(`^# Changelog\n`)
 )
 
+//go:embed changelog.md.tpl
+var rawChangelogTemplate string
+
 func init() {
 	var err error
-	changelogTemplate, err = template.New("changelog").Parse(`## [{{.Version}}]({{.VersionLink}})
+	changelogTemplate, err = template.New("changelog").Parse(rawChangelogTemplate)
-{{- if (gt (len .Features) 0) }}
-### Features
-
-{{ range .Features -}}
-- {{ if .Scope }}**{{.Scope}}**: {{end}}{{.Description}}
-{{ end -}}
-{{- end -}}
-{{- if (gt (len .Fixes) 0) }}
-### Bug Fixes
-
-{{ range .Fixes -}}
-- {{ if .Scope }}**{{.Scope}}**: {{end}}{{.Description}}
-{{ end -}}
-{{- end -}}
-`,
-	)
 	if err != nil {
 		log.Fatalf("failed to parse changelog template: %v", err)
 	}
 }
 
-func UpdateChangelog(wt *git.Worktree, commits []AnalyzedCommit) error {
+func UpdateChangelogFile(wt *git.Worktree, newEntry string) error {
+	file, err := wt.Filesystem.OpenFile(ChangelogFile, os.O_RDWR|os.O_CREATE, 0644)
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+
+	content, err := io.ReadAll(file)
+	if err != nil {
+		return err
+	}
+
+	headerIndex := headerRegex.FindIndex(content)
+	if headerIndex == nil && len(content) != 0 {
+		return fmt.Errorf("unexpected format of CHANGELOG.md, header does not match")
+	}
+	if headerIndex != nil {
+		// Remove the header from the content
+		content = content[headerIndex[1]:]
+	}
+
+	err = file.Truncate(0)
+	if err != nil {
+		return err
+	}
+	_, err = file.Seek(0, io.SeekStart)
+	if err != nil {
+		return err
+	}
+
+	_, err = file.Write([]byte(ChangelogHeader + "\n\n" + newEntry))
+	if err != nil {
+		return err
+	}
+
+	_, err = file.Write(content)
+	if err != nil {
+		return err
+	}
+
+	// Close file to make sure it is written to disk.
+	err = file.Close()
+	if err != nil {
+		return err
+	}
+
+	_, err = wt.Add(ChangelogFile)
+	if err != nil {
+		return err
+	}
+
 	return nil
 }
 
-func formatChangelog(commits []AnalyzedCommit, version, link string) (string, error) {
+func NewChangelogEntry(commits []AnalyzedCommit, version, link string) (string, error) {
 	features := make([]AnalyzedCommit, 0)
 	fixes := make([]AnalyzedCommit, 0)
 

changelog.md.tpl

@@ -0,0 +1,16 @@
+## [{{.Version}}]({{.VersionLink}})
+{{- if (gt (len .Features) 0) }}
+### Features
+
+{{ range .Features -}}
+- {{ if .Scope }}**{{.Scope}}**: {{end}}{{.Description}}
+{{ end -}}
+{{- end -}}
+{{- if (gt (len .Fixes) 0) }}
+### Bug Fixes
+
+{{ range .Fixes -}}
+- {{ if .Scope }}**{{.Scope}}**: {{end}}{{.Description}}
+{{ end -}}
+{{- end -}}
+`

changelog_test.go

@@ -1,16 +1,108 @@
 package rp
 
 import (
+	"io"
+	"log"
 	"testing"
 
+	"github.com/go-git/go-git/v5"
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/apricote/releaser-pleaser/internal/testutils"
 )
 
 func ptr[T any](input T) *T {
 	return &input
 }
 
-func Test_formatChangelog(t *testing.T) {
+func TestUpdateChangelogFile(t *testing.T) {
+	tests := []struct {
+		name            string
+		repoFn          testutils.Repo
+		entry           string
+		expectedContent string
+		newFile         bool
+		wantErr         assert.ErrorAssertionFunc
+	}{
+		{
+			name:            "empty repo",
+			repoFn:          testutils.WithTestRepo(),
+			entry:           "## v1.0.0\n",
+			expectedContent: "# Changelog\n\n## v1.0.0\n",
+			newFile:         true,
+			wantErr:         assert.NoError,
+		},
+		{
+			name: "repo with well-formatted changelog",
+			repoFn: testutils.WithTestRepo(testutils.WithCommit("feat: add changelog", testutils.WithFile(ChangelogFile, `# Changelog
+
+## v0.0.1
+
+- Bazzle
+
+## v0.1.0
+
+### Bazuuum
+`))),
+			entry: "## v1.0.0\n\n- Version 1, juhu.\n",
+			expectedContent: `# Changelog
+
+## v1.0.0
+
+- Version 1, juhu.
+
+## v0.0.1
+
+- Bazzle
+
+## v0.1.0
+
+### Bazuuum
+`,
+			wantErr: assert.NoError,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			repo := tt.repoFn(t)
+			wt, err := repo.Worktree()
+			require.NoError(t, err, "failed to get worktree")
+
+			err = UpdateChangelogFile(wt, tt.entry)
+			if !tt.wantErr(t, err) {
+				return
+			}
+
+			wtStatus, err := wt.Status()
+			require.NoError(t, err, "failed to get worktree status")
+
+			assert.Len(t, wtStatus, 1, "worktree status does not have the expected entry number")
+
+			changelogFileStatus := wtStatus.File(ChangelogFile)
+
+			if tt.newFile {
+				assert.Equal(t, git.Unmodified, changelogFileStatus.Worktree, "unexpected file status in worktree")
+				assert.Equal(t, git.Added, changelogFileStatus.Staging, "unexpected file status in staging")
+			} else {
+				assert.Equal(t, git.Modified, changelogFileStatus.Worktree, "unexpected file status in worktree")
+				assert.Equal(t, git.Modified, changelogFileStatus.Staging, "unexpected file status in staging")
+			}
+
+			changelogFile, err := wt.Filesystem.Open(ChangelogFile)
+			require.NoError(t, err)
+			defer changelogFile.Close()
+
+			changelogFileContent, err := io.ReadAll(changelogFile)
+			require.NoError(t, err)
+
+			assert.Equal(t, tt.expectedContent, string(changelogFileContent))
+		})
+	}
+}
+
+func Test_NewChangelogEntry(t *testing.T) {
 	type args struct {
 		commits []AnalyzedCommit
 		version string
@@ -111,7 +203,7 @@ func Test_formatChangelog(t *testing.T) {
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			got, err := formatChangelog(tt.args.commits, tt.args.version, tt.args.link)
+			got, err := NewChangelogEntry(tt.args.commits, tt.args.version, tt.args.link)
 			if !tt.wantErr(t, err) {
 				return
 			}