feat: auto-detect language in init

.gitignore

@@ -8,4 +8,5 @@ apps/openant-cli/bin/
 libs/openant-core/parsers/go/go_parser/go_parser
 libs/openant-core/parsers/javascript/.openant-npm-install.lock
 _docs/
-
+docs/
+.worktrees/

apps/openant-cli/cmd/init.go

@@ -1,7 +1,9 @@
 package cmd
 
 import (
+	"encoding/json"
 	"fmt"
+	"io/fs"
 	"os"
 	"os/exec"
 	"path/filepath"
@@ -26,6 +28,7 @@ After init, all commands (parse, scan, etc.) work without path arguments.
 Examples:
   openant init https://github.com/grafana/grafana -l go
   openant init https://github.com/grafana/grafana -l go --commit 591ceb2eec0
+  openant init https://github.com/grafana/grafana -l auto
   openant init ./repos/grafana -l go
   openant init ./repos/grafana -l go --name myorg/grafana`,
 	Args: cobra.ExactArgs(1),
@@ -44,7 +47,7 @@ var (
 )
 
 func init() {
-	initCmd.Flags().StringVarP(&initLanguage, "language", "l", "", "Language to analyze: python, javascript, go, c, ruby, php (required)")
+	initCmd.Flags().StringVarP(&initLanguage, "language", "l", "", "Language to analyze: python, javascript, go, c, ruby, php, zig, auto (auto = experimental dominance heuristic; see #61)")
 	initCmd.Flags().StringVar(&initCommit, "commit", "", "Specific commit SHA (default: HEAD)")
 	initCmd.Flags().StringVar(&initName, "name", "", "Override project name (default: derived from URL/path)")
 	initCmd.Flags().BoolVar(&initFull, "full", false, "Force full scan (rejects --incremental/--diff-base/--pr)")
@@ -118,7 +121,7 @@ func runInit(cmd *cobra.Command, args []string) {
 			}
 		}
 	} else {
-		// Local: verify it's a git repo and resolve absolute path
+		// Local: resolve absolute path
 		source = "local"
 
 		absPath, err := filepath.Abs(input)
@@ -127,29 +130,48 @@ func runInit(cmd *cobra.Command, args []string) {
 			os.Exit(1)
 		}
 
-		if _, err := os.Stat(filepath.Join(absPath, ".git")); err != nil {
-			output.PrintError(fmt.Sprintf("%s is not a git repository (no .git directory)", absPath))
+		repoPath = absPath
+	}
+
+	// Auto-detect language if not specified
+	if initLanguage == "" || initLanguage == "auto" {
+		fmt.Fprintf(os.Stderr, "Auto-detecting language...\n")
+		detected, err := detectLanguage(repoPath)
+		if err != nil {
+			output.PrintError(fmt.Sprintf("Language auto-detection failed: %s\nSpecify manually with -l/--language", err))
 			os.Exit(1)
 		}
+		initLanguage = detected
+		fmt.Fprintf(os.Stderr, "Detected language: %s\n", initLanguage)
+	}
 
-		repoPath = absPath
+	// Get commit SHA (best-effort — not all local paths are git repos)
+	isGit := false
+	if _, err := os.Stat(filepath.Join(repoPath, ".git")); err == nil {
+		isGit = true
 	}
 
-	// Get commit SHA
 	commitSHA := initCommit
-	if commitSHA == "" {
-		out, err := exec.Command("git", "-C", repoPath, "rev-parse", "HEAD").Output()
-		if err != nil {
-			output.PrintError(fmt.Sprintf("Failed to get HEAD commit: %s", err))
-			os.Exit(1)
+	if isGit {
+		if commitSHA == "" {
+			out, err := exec.Command("git", "-C", repoPath, "rev-parse", "HEAD").Output()
+			if err != nil {
+				output.PrintError(fmt.Sprintf("Failed to get HEAD commit: %s", err))
+				os.Exit(1)
+			}
+			commitSHA = strings.TrimSpace(string(out))
+		} else {
+			// Resolve short SHA to full SHA
+			out, err := exec.Command("git", "-C", repoPath, "rev-parse", commitSHA).Output()
+			if err == nil {
+				commitSHA = strings.TrimSpace(string(out))
+			}
 		}
-		commitSHA = strings.TrimSpace(string(out))
 	} else {
-		// Resolve short SHA to full SHA
-		out, err := exec.Command("git", "-C", repoPath, "rev-parse", commitSHA).Output()
-		if err == nil {
-			commitSHA = strings.TrimSpace(string(out))
+		if commitSHA != "" {
+			output.PrintWarning("--commit ignored: not a git repository")
 		}
+		commitSHA = "nogit"
 	}
 
 	// Create project
@@ -224,3 +246,125 @@ func runInit(cmd *cobra.Command, args []string) {
 	output.PrintSuccess("Set as active project")
 	fmt.Println()
 }
+
+// languagesConfig is the structure of config/languages.json.
+type languagesConfig struct {
+	SkipDirs   []string          `json:"skip_dirs"`
+	Extensions map[string]string `json:"extensions"`
+}
+
+// findLanguagesConfig locates config/languages.json by walking up from the
+// executable path and then the current working directory.
+func findLanguagesConfig() (string, error) {
+	rel := filepath.Join("config", "languages.json")
+
+	// Strategy 1: walk up from the executable.
+	if exePath, err := os.Executable(); err == nil {
+		exePath, _ = filepath.EvalSymlinks(exePath)
+		dir := filepath.Dir(exePath)
+		for range 6 {
+			candidate := filepath.Join(dir, rel)
+			if info, err := os.Stat(candidate); err == nil && !info.IsDir() {
+				return candidate, nil
+			}
+			parent := filepath.Dir(dir)
+			if parent == dir {
+				break
+			}
+			dir = parent
+		}
+	}
+
+	// Strategy 2: walk up from CWD.
+	if cwd, err := os.Getwd(); err == nil {
+		dir := cwd
+		for range 6 {
+			candidate := filepath.Join(dir, rel)
+			if info, err := os.Stat(candidate); err == nil && !info.IsDir() {
+				return candidate, nil
+			}
+			parent := filepath.Dir(dir)
+			if parent == dir {
+				break
+			}
+			dir = parent
+		}
+	}
+
+	return "", fmt.Errorf("could not find config/languages.json from executable or working directory")
+}
+
+// loadLanguagesConfig loads the shared language detection config.
+func loadLanguagesConfig() (*languagesConfig, error) {
+	path, err := findLanguagesConfig()
+	if err != nil {
+		return nil, err
+	}
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read %s: %w", path, err)
+	}
+	var cfg languagesConfig
+	if err := json.Unmarshal(data, &cfg); err != nil {
+		return nil, fmt.Errorf("failed to parse %s: %w", path, err)
+	}
+	return &cfg, nil
+}
+
+// detectLanguage walks a repository and returns the dominant language by file count.
+// Extension mappings and skip directories are loaded from config/languages.json
+// (shared with libs/openant-core/core/parser_adapter.py::detect_language()).
+func detectLanguage(repoPath string) (string, error) {
+	cfg, err := loadLanguagesConfig()
+	if err != nil {
+		return "", fmt.Errorf("failed to load language config: %w", err)
+	}
+
+	skipDirs := make(map[string]bool, len(cfg.SkipDirs))
+	for _, d := range cfg.SkipDirs {
+		skipDirs[d] = true
+	}
+
+	counts := make(map[string]int)
+
+	err = filepath.WalkDir(repoPath, func(path string, d fs.DirEntry, err error) error {
+		if err != nil {
+			return nil // skip inaccessible paths
+		}
+		if d.IsDir() {
+			if skipDirs[d.Name()] {
+				return filepath.SkipDir
+			}
+			return nil
+		}
+
+		ext := strings.ToLower(filepath.Ext(d.Name()))
+		if lang, ok := cfg.Extensions[ext]; ok {
+			counts[lang]++
+		}
+		return nil
+	})
+	if err != nil {
+		return "", fmt.Errorf("failed to walk repository: %w", err)
+	}
+
+	// Find the dominant language
+	bestLang := ""
+	bestCount := 0
+	for lang, count := range counts {
+		if count > bestCount {
+			bestCount = count
+			bestLang = lang
+		}
+	}
+
+	if bestLang == "" {
+		return "", fmt.Errorf(
+			"no supported source files found in %s. "+
+				"Supported languages: Python, JavaScript/TypeScript, Go, C/C++, Ruby, PHP, Zig",
+			repoPath,
+		)
+	}
+
+	return bestLang, nil
+}

config/languages.json

@@ -0,0 +1,34 @@
+{
+  "skip_dirs": [
+    "node_modules",
+    "__pycache__",
+    "venv",
+    ".venv",
+    "dist",
+    "build",
+    ".git",
+    "vendor"
+  ],
+  "extensions": {
+    ".py": "python",
+    ".js": "javascript",
+    ".ts": "javascript",
+    ".jsx": "javascript",
+    ".tsx": "javascript",
+    ".mjs": "javascript",
+    ".cjs": "javascript",
+    ".go": "go",
+    ".c": "c",
+    ".h": "c",
+    ".cpp": "c",
+    ".hpp": "c",
+    ".cc": "c",
+    ".cxx": "c",
+    ".hxx": "c",
+    ".hh": "c",
+    ".rb": "ruby",
+    ".rake": "ruby",
+    ".php": "php",
+    ".zig": "zig"
+  }
+}

libs/openant-core/core/parser_adapter.py

@@ -26,46 +26,43 @@
 # JS parser directory (holds its own package.json / node_modules)
 _JS_PARSER_DIR = _CORE_ROOT / "parsers" / "javascript"
 
+# Shared language detection config (single source of truth: config/languages.json)
+_LANGUAGES_CONFIG = Path(__file__).parent.parent.parent.parent / "config" / "languages.json"
+
+
+def _load_language_config() -> dict:
+    return read_json(_LANGUAGES_CONFIG)
+
 
 def detect_language(repo_path: str) -> str:
     """Auto-detect the primary language of a repository.
 
     Counts source files by extension and returns the dominant language.
+    Extension mappings and skip directories are loaded from config/languages.json.
 
     Returns:
-        "python", "javascript", or "go"
+        One of: "python", "javascript", "go", "c", "ruby", "php", "zig"
     """
+    config = _load_language_config()
+    skip_dirs = set(config["skip_dirs"])
+    extensions = config["extensions"]
+
     repo = Path(repo_path)
-    counts = {"python": 0, "javascript": 0, "go": 0, "c": 0, "ruby": 0, "php": 0, "zig": 0}
+    counts: dict[str, int] = {}
 
     for f in repo.rglob("*"):
         if not f.is_file():
             continue
-        # Skip common non-source dirs
-        parts = f.parts
-        if any(p in parts for p in (
-            "node_modules", "__pycache__", "venv", ".venv",
-            "dist", "build", ".git", "vendor",
-        )):
+        # Skip configured non-source dirs
+        if any(p in skip_dirs for p in f.parts):
             continue
 
         suffix = f.suffix.lower()
-        if suffix == ".py":
-            counts["python"] += 1
-        elif suffix in (".js", ".ts", ".jsx", ".tsx", ".mjs", ".cjs"):
-            counts["javascript"] += 1
-        elif suffix == ".go":
-            counts["go"] += 1
-        elif suffix in (".c", ".h", ".cpp", ".hpp", ".cc", ".cxx", ".hxx", ".hh"):
-            counts["c"] += 1
-        elif suffix in (".rb", ".rake"):
-            counts["ruby"] += 1
-        elif suffix == ".php":
-            counts["php"] += 1
-        elif suffix == ".zig":
-            counts["zig"] += 1
-
-    if not any(counts.values()):
+        if suffix in extensions:
+            lang = extensions[suffix]
+            counts[lang] = counts.get(lang, 0) + 1
+
+    if not counts:
         raise ValueError(
             f"No supported source files found in {repo_path}. "
             "Supported languages: Python, JavaScript/TypeScript, Go, C/C++, Ruby, PHP, Zig."