feat(formatter): implement line-length constraints

and enhanced AI context

    - Add maxSubjectLength and maxBodyLength configuration options.
    - Update Formatter to support automatic line wrapping and subject-to-body
      overflow with blank line separation.
    - Enrich AI prompt with summarized git diff content for better commit
      body generation.
    - Refine wrapping logic to preserve multi-paragraph structures.
    - Add unit tests for the new formatting and wrapping behavior.

Author: andev0x

assets/prompts/system_prompt.txt

@@ -1,10 +1,13 @@
-You are an expert developer assistant. Analyze the provided structured git diff metadata and generate a single-line commit message following the Conventional Commits specification.
+You are an expert developer assistant. Analyze the provided structured git diff metadata and generate a commit message following the Conventional Commits specification.
 
 Guidelines:
 1. Format MUST be: <type>(<scope>): <short description in present tense>
 2. Allowed types: feat, fix, refactor, chore, test, docs, style, perf, ci, build, security
-3. Do NOT include any markdown, backticks, quotes, or introductory text like "Here is your commit message:".
-4. Output ONLY the raw string of the commit message.
+3. If the changes are complex, you MAY include a body separated by a blank line after the subject.
+4. Keep the subject line short (aim for ~50 characters).
+5. Wrap body lines at ~72 characters.
+6. Do NOT include any markdown, backticks, quotes, or introductory text like "Here is your commit message:".
+7. Output ONLY the raw string of the commit message.
 
 Metadata Context:
 - Project Type: {{.ProjectType}}
@@ -15,4 +18,7 @@ Metadata Context:
 - Dependency Changes: {{.DependencyAlert}}
 - Added/Deleted Line Ratio: {{printf "%.2f" .DiffSummary.Ratio}}
 
+Summarized Git Diff:
+{{.DiffContent}}
+
 Output:

cmd/propose.go

@@ -92,7 +92,7 @@ func runPropose(cmd *cobra.Command, args []string) error {
 		return err
 	}
 
-	f := formatter.NewFormatter()
+	f := formatter.NewFormatter(cfg.MaxSubjectLength, cfg.MaxBodyLength)
 
 	// Calculate Heuristic Suggestion (Always available)
 	heuristicMsg, err := templater.GetMessage(commitMessage)
@@ -112,7 +112,7 @@ func runPropose(cmd *cobra.Command, args []string) error {
 			client := ai.NewOllamaClient(cfg.Ollama)
 			aiResponse, err := client.Generate(prompt)
 			if err == nil && ai.IsValidCommitMessage(aiResponse) {
-				aiMsg = strings.TrimSpace(aiResponse)
+				aiMsg = f.FormatMessage(strings.TrimSpace(aiResponse), commitMessage.IsMajor)
 				usingAI = true
 				finalMessage = aiMsg
 			}
@@ -220,7 +220,7 @@ func runPropose(cmd *cobra.Command, args []string) error {
 				editedMessage = strings.TrimSpace(editedMessage)
 
 				if editedMessage != "" {
-					finalMessage = editedMessage
+					finalMessage = f.FormatMessage(editedMessage, commitMessage.IsMajor)
 					usedSuggestions[finalMessage] = true
 					color.Green("\n✓ Updated commit message:")
 				} else {
@@ -240,7 +240,7 @@ func runPropose(cmd *cobra.Command, args []string) error {
 						client := ai.NewOllamaClient(cfg.Ollama)
 						aiResponse, err := client.Generate(prompt)
 						if err == nil && ai.IsValidCommitMessage(aiResponse) {
-							finalMessage = strings.TrimSpace(aiResponse)
+							finalMessage = f.FormatMessage(strings.TrimSpace(aiResponse), commitMessage.IsMajor)
 							regenerationCount++
 						}
 					}
@@ -264,7 +264,7 @@ func runPropose(cmd *cobra.Command, args []string) error {
 					client := ai.NewOllamaClient(cfg.Ollama)
 					aiResponse, err := client.Generate(prompt)
 					if err == nil && ai.IsValidCommitMessage(aiResponse) {
-						aiMsg = strings.TrimSpace(aiResponse)
+						aiMsg = f.FormatMessage(strings.TrimSpace(aiResponse), commitMessage.IsMajor)
 						finalMessage = aiMsg
 						usingAI = true
 					} else {

docs/CONFIGURATION.md

@@ -133,6 +133,24 @@ Defines the confidence weights for different signal sources. Only used when `nor
 }
 ```
 
+### Message Length Constraints
+
+**`maxSubjectLength`** (int, default: 50)
+
+Specifies the maximum character length for the first line (subject) of the commit message. If the generated or edited subject exceeds this limit, it will be automatically wrapped to the next line.
+
+**`maxBodyLength`** (int, default: 72)
+
+Specifies the maximum character length for each line in the body of the commit message. If the body text exceeds this limit, it will be wrapped at word boundaries.
+
+**Example:**
+```json
+{
+  "maxSubjectLength": 50,
+  "maxBodyLength": 72
+}
+```
+
 ### Topic Mappings
 
 **`topicMappings`** (object)

internal/ai/ai_test.go

@@ -44,6 +44,7 @@ func TestIsValidCommitMessage(t *testing.T) {
 		expected bool
 	}{
 		{"feat(auth): add login functionality", true},
+		{"feat(auth): add login\n\nThis is a body.", true},
 		{"fix: resolve memory leak", true},
 		{"chore(deps): update dependencies", true},
 		{"Invalid message", false},

internal/ai/prompt.go

@@ -19,6 +19,7 @@ type PromptContext struct {
 	CodeSymbols     []string
 	DependencyAlert string
 	DiffSummary     DiffSummary
+	DiffContent     string
 }
 
 // DiffSummary contains ratio of changes
@@ -70,6 +71,7 @@ func RenderPrompt(msg *analyzer.CommitMessage, projectType, branchName string) (
 		DiffSummary: DiffSummary{
 			Ratio: ratio,
 		},
+		DiffContent: msg.FullDiff,
 	}
 
 	var buf bytes.Buffer

internal/analyzer/analyzer.go

@@ -2,6 +2,7 @@ package analyzer
 
 import (
 	"bufio"
+	"fmt"
 	"path/filepath"
 	"regexp"
 	"strings"
@@ -32,6 +33,7 @@ type CommitMessage struct {
 	DetectedStructs   []string
 	DetectedMethods   []string
 	ChangePatterns    []string
+	FullDiff          string
 }
 
 // Analyzer is responsible for analyzing git changes and generating commit message components
@@ -105,6 +107,15 @@ func (a *Analyzer) AnalyzeChanges(totalAdded, totalRemoved int, branchName strin
 	commitMessage.DetectedMethods = uniqueStrings(allMethods)
 	commitMessage.ChangePatterns = uniqueStrings(allPatterns)
 
+	// Collect summarized diff for AI
+	var diffSummary strings.Builder
+	for _, change := range a.changes {
+		diffSummary.WriteString(fmt.Sprintf("File: %s\n", change.File))
+		diffSummary.WriteString(a.summarizeDiff(change.Diff))
+		diffSummary.WriteString("\n")
+	}
+	commitMessage.FullDiff = diffSummary.String()
+
 	// Determine if changes are only documentation, config, or dependencies
 	commitMessage.IsDocsOnly = a.isDocsOnly()
 	commitMessage.IsConfigOnly = a.isConfigOnly()
@@ -1273,3 +1284,29 @@ func (a *Analyzer) calculateHistoryScope(commits []string) string {
 
 	return ""
 }
+
+// summarizeDiff extracts the most relevant lines from a diff to keep it concise for AI
+func (a *Analyzer) summarizeDiff(diff string) string {
+	var summary strings.Builder
+	scanner := bufio.NewScanner(strings.NewReader(diff))
+	lineCount := 0
+	maxLines := 20 // Limit lines per file to avoid context bloat
+
+	for scanner.Scan() {
+		line := scanner.Text()
+		// Only include added/removed lines and hunk headers
+		if strings.HasPrefix(line, "+") || strings.HasPrefix(line, "-") || strings.HasPrefix(line, "@@") {
+			if strings.HasPrefix(line, "+++") || strings.HasPrefix(line, "---") {
+				continue
+			}
+			summary.WriteString(line)
+			summary.WriteString("\n")
+			lineCount++
+		}
+		if lineCount >= maxLines {
+			summary.WriteString("... (truncated)\n")
+			break
+		}
+	}
+	return summary.String()
+}

internal/config/config.go

@@ -19,6 +19,8 @@ type Config struct {
 	DiffStatThreshold float64                      `json:"diffStatThreshold"` // Threshold for add/delete ratio
 	NormalizeScoring  bool                         `json:"normalizeScoring"`  // Whether to use normalized confidence weights
 	SignalWeights     map[string]float64           `json:"signalWeights"`     // Weights for different signal sources
+	MaxSubjectLength  int                          `json:"maxSubjectLength"`  // Max length for the first line
+	MaxBodyLength     int                          `json:"maxBodyLength"`     // Max length for body lines
 }
 
 // OllamaConfig represents the structure of the ollama configuration block
@@ -50,6 +52,8 @@ func LoadConfig() (*Config, error) {
 			"keywords": 0.25,
 			"patterns": 0.15,
 		},
+		MaxSubjectLength: 50,
+		MaxBodyLength:    72,
 	}
 
 	// 1. Try to load embedded default config (optional)
@@ -291,5 +295,13 @@ func mergeConfigFromFile(cfg *Config, path string) error {
 		}
 	}
 
+	// Message lengths
+	if fileCfg.MaxSubjectLength > 0 {
+		cfg.MaxSubjectLength = fileCfg.MaxSubjectLength
+	}
+	if fileCfg.MaxBodyLength > 0 {
+		cfg.MaxBodyLength = fileCfg.MaxBodyLength
+	}
+
 	return nil
 }

internal/formatter/formatter.go

@@ -6,44 +6,103 @@ import (
 )
 
 // Formatter is responsible for applying final formatting to commit messages
-type Formatter struct{}
+type Formatter struct {
+	MaxSubjectLength int
+	MaxBodyLength    int
+}
 
 // NewFormatter creates a new Formatter
-func NewFormatter() *Formatter {
-	return &Formatter{}
+func NewFormatter(maxSubject, maxBody int) *Formatter {
+	return &Formatter{
+		MaxSubjectLength: maxSubject,
+		MaxBodyLength:    maxBody,
+	}
 }
 
 // FormatMessage applies formatting rules to the commit message
 func (f *Formatter) FormatMessage(msg string, isMajor bool) string {
-	// Capitalize the first letter
-	/* if len(msg) > 0 {
-		r := []rune(msg)
-		r[0] = unicode.ToUpper(r[0])
-		msg = string(r)
-	} */
-
-	// Remove redundant phrases
-	msg = strings.ReplaceAll(msg, "add add new", "add new")
-	msg = strings.ReplaceAll(msg, "feat feat", "feat")
-	msg = strings.ReplaceAll(msg, "fix fix", "fix")
-
-	// Enforce summary length (soft limit for now, try to break at word boundaries)
-	if len(msg) > 72 {
-		truncatedMsg := msg
-		if len(truncatedMsg) > 72 {
-			truncatedMsg = truncatedMsg[:72]
-			lastSpace := strings.LastIndex(truncatedMsg, " ")
-			if lastSpace != -1 {
-				truncatedMsg = truncatedMsg[:lastSpace]
+	if msg == "" {
+		return ""
+	}
+
+	// Split into subject and body
+	parts := strings.SplitN(msg, "\n", 2)
+	subject := strings.TrimSpace(parts[0])
+	body := ""
+	if len(parts) > 1 {
+		body = strings.TrimSpace(parts[1])
+	}
+
+	// Remove redundant phrases from subject
+	subject = strings.ReplaceAll(subject, "add add new", "add new")
+	subject = strings.ReplaceAll(subject, "feat feat", "feat")
+	subject = strings.ReplaceAll(subject, "fix fix", "fix")
+
+	// Add optional suffixes to subject
+	if isMajor {
+		subject = fmt.Sprintf("%s (massive refactor)", subject)
+	}
+
+	// Wrap subject if too long
+	if f.MaxSubjectLength > 0 && len(subject) > f.MaxSubjectLength {
+		wrapped := f.wrapString(subject, f.MaxSubjectLength)
+		subjectParts := strings.SplitN(wrapped, "\n", 2)
+		subject = subjectParts[0]
+		if len(subjectParts) > 1 {
+			if body != "" {
+				body = subjectParts[1] + "\n\n" + body
+			} else {
+				body = subjectParts[1]
 			}
-			msg = fmt.Sprintf("%s...", truncatedMsg)
 		}
 	}
 
-	// Add optional suffixes
-	if isMajor {
-		msg = fmt.Sprintf("%s (massive refactor)", msg)
+	// Wrap body if exists
+	if body != "" && f.MaxBodyLength > 0 {
+		body = f.wrapString(body, f.MaxBodyLength)
+	}
+
+	if body != "" {
+		return subject + "\n\n" + body
+	}
+	return subject
+}
+
+// wrapString wraps a string at the specified limit, preserving paragraphs
+func (f *Formatter) wrapString(s string, limit int) string {
+	if limit <= 0 {
+		return s
+	}
+
+	paragraphs := strings.Split(s, "\n\n")
+	var result strings.Builder
+
+	for i, p := range paragraphs {
+		if i > 0 {
+			result.WriteString("\n\n")
+		}
+
+		words := strings.Fields(p)
+		if len(words) == 0 {
+			continue
+		}
+
+		currentLineLength := 0
+		for j, word := range words {
+			if j > 0 {
+				if currentLineLength+1+len(word) > limit {
+					result.WriteString("\n")
+					currentLineLength = 0
+				} else {
+					result.WriteString(" ")
+					currentLineLength++
+				}
+			}
+
+			result.WriteString(word)
+			currentLineLength += len(word)
+		}
 	}
 
-	return msg
+	return result.String()
 }