feat(changelog): add first draft for changelog generation

internal/changelog/changelog.go

@@ -0,0 +1,82 @@
+package changelog
+
+import (
+	"bytes"
+	"text/template"
+	"time"
+
+	"github.com/Nightapes/go-semantic-release/internal/analyzer"
+	"github.com/Nightapes/go-semantic-release/pkg/config"
+)
+
+const defaultChangelogTitle string = `v{{.Version}} ({{.Now.Format "2006-01-02"}})`
+const defaultChangelog string = `{{ $version := .Version -}}
+{{ $backtick := .Backtick -}}
+# v{{.Version}} ({{.Now.Format "2006-01-02"}})
+{{ range $key, $commits := .Commits }}
+### {{ $key }}
+
+{{range $index,$commit := $commits}}* **{{$backtick}}{{$commit.Scope}}:{{$backtick}}** {{$commit.ParsedMessage}}
+{{ end -}}
+{{ end -}}
+`
+
+type changelogContent struct {
+	Commits  map[string][]analyzer.AnalyzedCommit
+	Version  string
+	Now      time.Time
+	Backtick string
+}
+
+//CommitFormat struct
+type Changelog struct {
+	config *config.ReleaseConfig
+}
+
+//New Changelog struct for generating changelog from commits
+func New(config *config.ReleaseConfig) *Changelog {
+	return &Changelog{
+		config: config,
+	}
+}
+
+// GenerateChanglog from given commits
+func (c *Changelog) GenerateChanglog(version string, analyzedCommits map[string][]analyzer.AnalyzedCommit) (string, string, error) {
+
+	commitsPerScope := map[string][]analyzer.AnalyzedCommit{}
+	for _, commits := range analyzedCommits {
+		for _, commit := range commits {
+			if commit.Print {
+				if _, ok := commitsPerScope[commit.TagString]; !ok {
+					commitsPerScope[commit.TagString] = make([]analyzer.AnalyzedCommit, 0)
+				}
+				commitsPerScope[commit.TagString] = append(commitsPerScope[commit.TagString], commit)
+			}
+		}
+	}
+
+	changelogContent := changelogContent{
+		Version:  version,
+		Commits:  commitsPerScope,
+		Now:      time.Now(),
+		Backtick: "`",
+	}
+
+	title, err := generateTemplate(defaultChangelogTitle, changelogContent)
+	content, err := generateTemplate(defaultChangelog, changelogContent)
+
+	return title, content, err
+}
+
+func generateTemplate(text string, values changelogContent) (string, error) {
+	var tpl bytes.Buffer
+	tmpl, err := template.New("template").Parse(text)
+	if err != nil {
+		return "", nil
+	}
+	err = tmpl.Execute(&tpl, values)
+	if err != nil {
+		return "", nil
+	}
+	return tpl.String(), nil
+}