feat: Support JSON configuration file

6 files changed, 118 insertions, 32 deletions

diff --git a/README.md b/README.md
index fbdfafd..881add4 100644
--- a/README.md
+++ b/README.md
@@ -1,11 +1,11 @@
 # 🚀 Iku
 
-> Grammar-Aware Go Formatter: Structure through separation
+> Grammar-Aware Code Formatter: Structure through separation
 
 
 Let your code breathe!
 
-Iku is a grammar-based Go formatter that enforces consistent blank-line placement by statement and declaration type.
+Iku is a grammar-based formatter that enforces consistent blank-line placement by statement and declaration type. It supports Go, JavaScript, TypeScript, JSX, and TSX.
 
 ## Philosophy
 
@@ -20,7 +20,9 @@ Code structure should be visually apparent from its formatting. Iku groups state
 
 ## How It Works
 
-Iku applies standard Go formatting (via [go/format](https://pkg.go.dev/go/format)) first ([formatter.go#29](https://github.com/Fuwn/iku/blob/main/formatter.go#L29)), then adds its grammar-based blank-line rules on top. Your code gets `go fmt` output plus structural separation.
+For Go files, Iku applies standard Go formatting (via [go/format](https://pkg.go.dev/go/format)) first, then adds its grammar-based blank-line rules on top. Your code gets `go fmt` output plus structural separation.
+
+For JavaScript and TypeScript files (`.js`, `.ts`, `.jsx`, `.tsx`), Iku uses a heuristic line-based analyser that classifies statements by keyword (`function`, `class`, `if`, `for`, `try`, etc.) and applies the same blank-line rules.
 
 ## Installation
 
@@ -42,11 +44,13 @@ echo 'package main ...' | iku
 
 # Format and print to stdout
 iku file.go
+iku component.tsx
 
 # Format in-place
 iku -w file.go
+iku -w src/
 
-# Format entire directory
+# Format entire directory (Go, JS, TS, JSX, TSX)
 iku -w .
 
 # List files that need formatting
@@ -63,9 +67,46 @@ iku -d file.go
 | `-w` | Write result to file instead of stdout |
 | `-l` | List files whose formatting differs |
 | `-d` | Display diffs instead of rewriting |
-| `--comments` | Comment attachment mode: `follow`, `precede`, `standalone` |
 | `--version` | Print version |
 
+## Configuration
+
+Iku looks for `.iku.json` or `iku.json` in the current working directory.
+
+```json
+{
+  "comment_mode": "follow",
+  "group_single_line_functions": false
+}
+```
+
+All fields are optional. Omitted fields use their defaults.
+
+### `comment_mode`
+
+Controls how comments interact with blank-line insertion. Default: `"follow"`.
+
+| Mode | Behaviour |
+|------|-----------|
+| `follow` | Comments attach to the **next** statement. The blank line goes **before** the comment. |
+| `precede` | Comments attach to the **previous** statement. The blank line goes **after** the comment. |
+| `standalone` | Comments are independent. Blank lines are placed strictly by statement rules. |
+
+### `group_single_line_functions`
+
+When `true`, consecutive single-line function declarations of the same type are kept together without blank lines. Default: `false`.
+
+```go
+// group_single_line_functions = true
+func Base() string   { return baseDirectory }
+func Config() string { return configFile }
+
+// group_single_line_functions = false (default)
+func Base() string { return baseDirectory }
+
+func Config() string { return configFile }
+```
+
 ## Examples
 
 ### Before
diff --git a/configuration.go b/configuration.go
new file mode 100644
index 0000000..b00d778
--- /dev/null
+++ b/configuration.go
@@ -0,0 +1,44 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"strings"
+)
+
+type Configuration struct {
+	GroupSingleLineFunctions bool   `json:"group_single_line_functions"`
+	CommentMode             string `json:"comment_mode"`
+}
+
+func (configuration Configuration) commentMode() (CommentMode, error) {
+	switch strings.ToLower(configuration.CommentMode) {
+	case "", "follow":
+		return CommentsFollow, nil
+	case "precede":
+		return CommentsPrecede, nil
+	case "standalone":
+		return CommentsStandalone, nil
+	default:
+		return 0, fmt.Errorf("invalid comment_mode: %q (use follow, precede, or standalone)", configuration.CommentMode)
+	}
+}
+
+func loadConfiguration() Configuration {
+	var configuration Configuration
+
+	for _, fileName := range []string{".iku.json", "iku.json"} {
+		fileData, readError := os.ReadFile(fileName)
+
+		if readError != nil {
+			continue
+		}
+
+		_ = json.Unmarshal(fileData, &configuration)
+
+		break
+	}
+
+	return configuration
+}
diff --git a/engine/engine.go b/engine/engine.go
index 0b37dd4..6f7b7a0 100644
--- a/engine/engine.go
+++ b/engine/engine.go
@@ -11,7 +11,8 @@ const (
 )
 
 type Engine struct {
-	CommentMode CommentMode
+	CommentMode           CommentMode
+	GroupSingleLineScopes bool
 }
 
 func (e *Engine) format(events []LineEvent, resultBuilder *strings.Builder) {
@@ -21,6 +22,7 @@ func (e *Engine) format(events []LineEvent, resultBuilder *strings.Builder) {
 	previousWasComment := false
 	previousWasTopLevel := false
 	previousWasScoped := false
+	previousWasSingleLineScope := false
 
 	for eventIndex, event := range events {
 		if event.InRawString {
@@ -48,6 +50,7 @@ func (e *Engine) format(events []LineEvent, resultBuilder *strings.Builder) {
 		needsBlankLine := false
 		currentIsTopLevel := event.HasASTInfo && event.IsTopLevel
 		currentIsScoped := event.HasASTInfo && event.IsScoped
+		currentIsSingleLineScope := currentIsScoped && !event.IsOpeningBrace && !event.IsClosingBrace
 
 		if hasWrittenContent && !previousWasOpenBrace && !event.IsClosingBrace && !event.IsCaseLabel && !event.IsContinuation {
 			if currentIsTopLevel && previousWasTopLevel && currentStatementType != previousStatementType {
@@ -55,7 +58,9 @@ func (e *Engine) format(events []LineEvent, resultBuilder *strings.Builder) {
 					needsBlankLine = true
 				}
 			} else if event.HasASTInfo && (currentIsScoped || previousWasScoped) {
-				if !(e.CommentMode == CommentsFollow && previousWasComment) {
+				if e.GroupSingleLineScopes && currentIsSingleLineScope && previousWasSingleLineScope && currentStatementType == previousStatementType {
+					needsBlankLine = false
+				} else if !(e.CommentMode == CommentsFollow && previousWasComment) {
 					needsBlankLine = true
 				}
 			} else if currentStatementType != "" && previousStatementType != "" && currentStatementType != previousStatementType {
@@ -104,10 +109,12 @@ func (e *Engine) format(events []LineEvent, resultBuilder *strings.Builder) {
 			previousStatementType = event.StatementType
 			previousWasTopLevel = event.IsTopLevel
 			previousWasScoped = event.IsScoped
+			previousWasSingleLineScope = currentIsSingleLineScope
 		} else if currentStatementType != "" {
 			previousStatementType = currentStatementType
 			previousWasTopLevel = false
 			previousWasScoped = false
+			previousWasSingleLineScope = false
 		}
 	}
 
diff --git a/formatter.go b/formatter.go
index 0256694..a82d619 100644
--- a/formatter.go
+++ b/formatter.go
@@ -14,7 +14,8 @@ const (
 )
 
 type Formatter struct {
-	CommentMode CommentMode
+	CommentMode   CommentMode
+	Configuration Configuration
 }
 
 type lineInformation struct {
@@ -31,7 +32,10 @@ func (f *Formatter) Format(source []byte, filename string) ([]byte, error) {
 		return nil, err
 	}
 
-	formattingEngine := &engine.Engine{CommentMode: MapCommentMode(f.CommentMode)}
+	formattingEngine := &engine.Engine{
+		CommentMode:           MapCommentMode(f.CommentMode),
+		GroupSingleLineScopes: f.Configuration.GroupSingleLineFunctions,
+	}
 
 	return formattingEngine.FormatToBytes(events), nil
 }
diff --git a/inspect.go b/inspect.go
index 0c05657..8452de5 100644
--- a/inspect.go
+++ b/inspect.go
@@ -45,7 +45,10 @@ func (f *Formatter) buildLineInfo(tokenFileSet *token.FileSet, parsedFile *ast.F
 		}
 
 		lineInformationMap[startLine] = &lineInformation{statementType: statementType, isTopLevel: true, isScoped: isScoped, isStartLine: true}
-		lineInformationMap[endLine] = &lineInformation{statementType: statementType, isTopLevel: true, isScoped: isScoped, isStartLine: false}
+
+		if endLine != startLine {
+			lineInformationMap[endLine] = &lineInformation{statementType: statementType, isTopLevel: true, isScoped: isScoped, isStartLine: false}
+		}
 	}
 
 	ast.Inspect(parsedFile, func(astNode ast.Node) bool {
diff --git a/main.go b/main.go
index c41bfe2..781d873 100644
--- a/main.go
+++ b/main.go
@@ -15,11 +15,10 @@ import (
 
 var version = "dev"
 var (
-	writeFlag    = flag.Bool("w", false, "write result to (source) file instead of stdout")
-	listFlag     = flag.Bool("l", false, "list files whose formatting differs from iku's")
-	diffFlag     = flag.Bool("d", false, "display diffs instead of rewriting files")
-	commentsFlag = flag.String("comments", "follow", "comment attachment mode: follow, precede, standalone")
-	versionFlag  = flag.Bool("version", false, "print version")
+	writeFlag   = flag.Bool("w", false, "write result to (source) file instead of stdout")
+	listFlag    = flag.Bool("l", false, "list files whose formatting differs from iku's")
+	diffFlag    = flag.Bool("d", false, "display diffs instead of rewriting files")
+	versionFlag = flag.Bool("version", false, "print version")
 )
 
 func main() {
@@ -35,14 +34,15 @@ func main() {
 		os.Exit(0)
 	}
 
-	commentMode, err := parseCommentMode(*commentsFlag)
+	configuration := loadConfiguration()
+	commentMode, validationError := configuration.commentMode()
 
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "iku: %v\n", err)
+	if validationError != nil {
+		fmt.Fprintf(os.Stderr, "iku: %v\n", validationError)
 		os.Exit(2)
 	}
 
-	formatter := &Formatter{CommentMode: commentMode}
+	formatter := &Formatter{CommentMode: commentMode, Configuration: configuration}
 
 	if flag.NArg() == 0 {
 		if *writeFlag {
@@ -84,19 +84,6 @@ func main() {
 	os.Exit(exitCode)
 }
 
-func parseCommentMode(commentModeString string) (CommentMode, error) {
-	switch strings.ToLower(commentModeString) {
-	case "follow":
-		return CommentsFollow, nil
-	case "precede":
-		return CommentsPrecede, nil
-	case "standalone":
-		return CommentsStandalone, nil
-	default:
-		return 0, fmt.Errorf("invalid comment mode: %q (use follow, precede, or standalone)", commentModeString)
-	}
-}
-
 var supportedFileExtensions = map[string]bool{
 	".go":  true,
 	".js":  true,