Merge pull request #45 from yehonatanz/feature/autonumber

Support `autonumber` directive in sequence diagrams

Author: AlexanderGrooff

cmd/testdata/sequence-ascii/autonumber.txt

@@ -0,0 +1,25 @@
+sequenceDiagram
+    autonumber
+    Alice->>Bob: Hello
+    Bob->>Bob: Think
+    Bob-->>Alice: Hi
+    Alice->>Bob: Bye
+---
++-------+     +-----+
+| Alice |     | Bob |
++---+---+     +--+--+
+    |            |
+    | 1. Hello   |
+    +----------->|
+    |            |
+    |            | 2. Think
+    |            +--+
+    |            |  |
+    |            |<-+
+    |            |
+    | 3. Hi      |
+    |<...........+
+    |            |
+    | 4. Bye     |
+    +----------->|
+    |            |

cmd/testdata/sequence/autonumber.txt

@@ -0,0 +1,25 @@
+sequenceDiagram
+    autonumber
+    Alice->>Bob: Hello
+    Bob->>Bob: Think
+    Bob-->>Alice: Hi
+    Alice->>Bob: Bye
+---
+┌───────┐     ┌─────┐
+│ Alice │     │ Bob │
+└───┬───┘     └──┬──┘
+    │            │
+    │ 1. Hello   │
+    ├───────────►│
+    │            │
+    │            │ 2. Think
+    │            ├──┐
+    │            │  │
+    │            │◄─┘
+    │            │
+    │ 3. Hi      │
+    │◄┈┈┈┈┈┈┈┈┈┈┈┤
+    │            │
+    │ 4. Bye     │
+    ├───────────►│
+    │            │

internal/sequence/parser.go

@@ -20,12 +20,16 @@ var (
 
 	// messageRegex matches messages: [From]->>[To]: [Label]
 	messageRegex = regexp.MustCompile(`^\s*(?:"([^"]+)"|([^\s\->]+))\s*(-->>|->>)\s*(?:"([^"]+)"|([^\s\->]+))\s*:\s*(.*)$`)
+
+	// autonumberRegex matches the autonumber directive
+	autonumberRegex = regexp.MustCompile(`^\s*autonumber\s*$`)
 )
 
 // SequenceDiagram represents a parsed sequence diagram.
 type SequenceDiagram struct {
 	Participants []*Participant
 	Messages     []*Message
+	Autonumber   bool
 }
 
 type Participant struct {
@@ -39,6 +43,7 @@ type Message struct {
 	To        *Participant
 	Label     string
 	ArrowType ArrowType
+	Number    int // Message number when autonumber is enabled (0 means no number)
 }
 
 type ArrowType int
@@ -91,6 +96,7 @@ func Parse(input string) (*SequenceDiagram, error) {
 	sd := &SequenceDiagram{
 		Participants: []*Participant{},
 		Messages:     []*Message{},
+		Autonumber:   false,
 	}
 	participantMap := make(map[string]*Participant)
 
@@ -100,6 +106,12 @@ func Parse(input string) (*SequenceDiagram, error) {
 			continue
 		}
 
+		// Check for autonumber directive
+		if autonumberRegex.MatchString(trimmed) {
+			sd.Autonumber = true
+			continue
+		}
+
 		if matched, err := sd.parseParticipant(trimmed, participantMap); err != nil {
 			return nil, fmt.Errorf("line %d: %w", i+2, err)
 		} else if matched {
@@ -180,11 +192,17 @@ func (sd *SequenceDiagram) parseMessage(line string, participants map[string]*Pa
 		aType = SolidArrow
 	}
 
+	msgNumber := 0
+	if sd.Autonumber {
+		msgNumber = len(sd.Messages) + 1
+	}
+
 	msg := &Message{
 		From:      from,
 		To:        to,
 		Label:     label,
 		ArrowType: aType,
+		Number:    msgNumber,
 	}
 	sd.Messages = append(sd.Messages, msg)
 	return true, nil

internal/sequence/renderer.go

@@ -160,9 +160,14 @@ func renderMessage(msg *Message, layout *diagramLayout, chars BoxChars) []string
 	var lines []string
 	from, to := layout.participantCenters[msg.From.Index], layout.participantCenters[msg.To.Index]
 
-	if msg.Label != "" {
+	label := msg.Label
+	if msg.Number > 0 {
+		label = fmt.Sprintf("%d. %s", msg.Number, msg.Label)
+	}
+
+	if label != "" {
 		start := min(from, to) + labelLeftMargin
-		labelWidth := runewidth.StringWidth(msg.Label)
+		labelWidth := runewidth.StringWidth(label)
 		w := max(layout.totalWidth, start+labelWidth) + labelBufferSpace
 		line := []rune(buildLifeline(layout, chars))
 		if len(line) < w {
@@ -174,7 +179,7 @@ func renderMessage(msg *Message, layout *diagramLayout, chars BoxChars) []string
 		}
 
 		col := start
-		for _, r := range msg.Label {
+		for _, r := range label {
 			if col < len(line) {
 				line[col] = r
 				col++
@@ -226,10 +231,15 @@ func renderSelfMessage(msg *Message, layout *diagramLayout, chars BoxChars) []st
 		return r
 	}
 
-	if msg.Label != "" {
+	label := msg.Label
+	if msg.Number > 0 {
+		label = fmt.Sprintf("%d. %s", msg.Number, msg.Label)
+	}
+
+	if label != "" {
 		line := ensureWidth(buildLifeline(layout, chars))
 		start := center + labelLeftMargin
-		labelWidth := runewidth.StringWidth(msg.Label)
+		labelWidth := runewidth.StringWidth(label)
 		needed := start + labelWidth + labelBufferSpace
 		if len(line) < needed {
 			pad := make([]rune, needed-len(line))
@@ -239,7 +249,7 @@ func renderSelfMessage(msg *Message, layout *diagramLayout, chars BoxChars) []st
 			line = append(line, pad...)
 		}
 		col := start
-		for _, c := range msg.Label {
+		for _, c := range label {
 			if col < len(line) {
 				line[col] = c
 				col++

internal/sequence/renderer_test.go

@@ -25,6 +25,7 @@ func TestSequenceDiagramRendering(t *testing.T) {
 	// Test files - stored in sequence/ directory (Unicode expected output)
 	testFiles := []string{
 		"adjacent_participants_communication.txt",
+		"autonumber.txt",
 		"bidirectional_messages.txt",
 		"dotted_arrows_only.txt",
 		"four_participants.txt",
@@ -50,9 +51,10 @@ func TestSequenceDiagramRendering_ASCII(t *testing.T) {
 	testDataPath := filepath.Join(getTestDataPath(), "sequence-ascii")
 
 	goldenFiles := []string{
-		"simple_two_participants.txt",
+		"autonumber.txt",
 		"dotted_arrows_only.txt",
 		"self_message.txt",
+		"simple_two_participants.txt",
 		"three_participants.txt",
 	}
 
@@ -70,6 +72,7 @@ func TestSequenceDiagramRendering_ASCIISmokeTest(t *testing.T) {
 
 	testFiles := []string{
 		"adjacent_participants_communication.txt",
+		"autonumber.txt",
 		"bidirectional_messages.txt",
 		"dotted_arrows_only.txt",
 		"four_participants.txt",