feat(parser): add flags for latest and specific releases (#6)

Adds two new flags:

--latest
--release
To allow targeting individual versions in the changelog.

Fixes #3

changelog/changelog.go

@@ -2,6 +2,7 @@ package changelog
 
 import (
 	"bufio"
+	"fmt"
 	"regexp"
 	"strings"
 	"time"
@@ -32,6 +33,23 @@ func NewParser() *Parser {
 	}
 }
 
+func (p *Parser) GetLatest() (*ChangelogEntry, error) {
+	if len(p.entries) == 0 {
+		return nil, fmt.Errorf("no changelog entries found")
+	}
+	return &p.entries[0], nil
+}
+
+func (p *Parser) GetVersion(version string) (*ChangelogEntry, error) {
+	for _, entry := range p.entries {
+		if entry.Version == version {
+			return &entry, nil
+		}
+	}
+
+	return nil, fmt.Errorf("version %s not found", version)
+}
+
 // Parse the changelog content and return a slice of ChangelogEntry
 func (p *Parser) Parse(content string) ([]ChangelogEntry, error) {
 	scanner := bufio.NewScanner(strings.NewReader(content))

changelog/changelog_test.go

@@ -128,6 +128,111 @@ func TestParse(t *testing.T) {
 	}
 }
 
+func TestGetLatest(t *testing.T) {
+	input := `# Changelog
+
+## [v2.0.0](https://github.com/user/repo/compare/v1.0.0...v2.0.0) (2025-02-01)
+### Features
+* new feature
+
+## [v1.0.0](https://github.com/user/repo/compare/v0.1.0...v1.0.0) (2025-01-01)
+### Features
+* basic feature`
+
+	p := NewParser()
+	_, err := p.Parse(input)
+	if err != nil {
+		t.Fatalf("Parse failed: %v", err)
+	}
+
+	latest, err := p.GetLatest()
+	if err != nil {
+		t.Fatalf("GetLatest failed: %v", err)
+	}
+
+	if latest.Version != "2.0.0" {
+		t.Errorf("Expected version 2.0.0, got %s", latest.Version)
+	}
+}
+
+func TestGetVersion(t *testing.T) {
+	input := `# Changelog
+
+## [v2.0.0](https://github.com/user/repo/compare/v1.0.0...v2.0.0) (2025-02-01)
+### Features
+* new feature
+
+## [v1.0.0](https://github.com/user/repo/compare/v0.1.0...v1.0.0) (2025-01-01)
+### Features
+* basic feature`
+
+	tests := []struct {
+		name    string
+		version string
+		want    string
+		wantErr bool
+	}{
+		{
+			name:    "existing version",
+			version: "1.0.0",
+			want:    "1.0.0",
+			wantErr: false,
+		},
+		{
+			name:    "non-existent version",
+			version: "3.0.0",
+			want:    "",
+			wantErr: true,
+		},
+	}
+
+	p := NewParser()
+	_, err := p.Parse(input)
+	if err != nil {
+		t.Fatalf("Parse failed: %v", err)
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			entry, err := p.GetVersion(tt.version)
+			if tt.wantErr {
+				if err == nil {
+					t.Error("Expected error but got none")
+				}
+				return
+			}
+
+			if err != nil {
+				t.Errorf("Unexpected error: %v", err)
+				return
+			}
+
+			if entry.Version != tt.want {
+				t.Errorf("Expected version %s, got %s", tt.want, entry.Version)
+			}
+		})
+	}
+}
+
+func TestEmptyChangelog(t *testing.T) {
+	input := "# Changelog\n"
+	p := NewParser()
+	_, err := p.Parse(input)
+	if err != nil {
+		t.Fatalf("Parse failed: %v", err)
+	}
+
+	_, err = p.GetLatest()
+	if err == nil {
+		t.Error("Expected error for empty changelog but got none")
+	}
+
+	_, err = p.GetVersion("1.0.0")
+	if err == nil {
+		t.Error("Expected error for non-existent version but got none")
+	}
+}
+
 func mustParseTime(date string) time.Time {
 	t, err := time.Parse("2006-01-02", date)
 	if err != nil {

cmd/cmd.go

@@ -22,6 +22,8 @@ var cmd = &cobra.Command{
 		}
 
 		ver, _ := cmd.Flags().GetBool("version")
+		latest, _ := cmd.Flags().GetBool("latest")
+		release, _ := cmd.Flags().GetString("release")
 
 		if ver {
 			fmt.Printf("cl-parse v%s\n", VERSION)
@@ -41,12 +43,47 @@ var cmd = &cobra.Command{
 			os.Exit(1)
 		}
 
+		if latest {
+			if len(entries) == 0 {
+				fmt.Println("No changelog entries found")
+				os.Exit(1)
+			}
+			jsonData, err := json.MarshalIndent(entries[0], "", "  ")
+			if err != nil {
+				fmt.Println(err)
+				os.Exit(1)
+			}
+			fmt.Println(string(jsonData))
+			return
+		}
+
+		if release != "" {
+			found := false
+			for _, entry := range entries {
+				if entry.Version == release {
+					jsonData, err := json.MarshalIndent(entry, "", "  ")
+					if err != nil {
+						fmt.Println(err)
+						os.Exit(1)
+					}
+					fmt.Println(string(jsonData))
+					found = true
+					break
+				}
+			}
+			if !found {
+				fmt.Printf("Version %s not found in changelog\n", release)
+				os.Exit(1)
+			}
+			return
+		}
+
+		// default to printing all entries
 		jsonData, err := json.MarshalIndent(entries, "", "  ")
 		if err != nil {
 			fmt.Println(err)
 			os.Exit(1)
 		}
-
 		fmt.Println(string(jsonData))
 	},
 }
@@ -60,4 +97,6 @@ func Execute() {
 
 func init() {
 	cmd.Flags().BoolP("version", "v", false, "display the current version of cl-parse")
+	cmd.Flags().BoolP("latest", "l", false, "display the most recent version from the changelog")
+	cmd.Flags().StringP("release", "r", "", "display the changelog entry for a specific release")
 }