package config

import (
	"fmt"
	"os"
	"path/filepath"
)

// RootDir walks from the working directory upward, looking for searchName as a
// regular file. depth limits how many parent directories are checked (0 = CWD only).
func RootDir(searchName string, depth ...int) (string, error) {
	cwd, err := os.Getwd()
	if err != nil {
		return "", err
	}

	depthVal := 0
	if len(depth) > 0 {
		depthVal = depth[0]
	}

	path, err := walkRootDir(searchName, cwd, depthVal)
	if err != nil {
		return "", err
	}
	if path == "" {
		return "", fmt.Errorf("RootDir checked %d directories, no '%s' file found", depthVal+1, searchName)
	}

	return filepath.Abs(path)
}

// MustRootDir is like [RootDir] but panics on error.
func MustRootDir(searchName string, depth ...int) string {
	dir, err := RootDir(searchName, depth...)
	if err != nil {
		panic(err)
	}
	return dir
}

func walkRootDir(searchName, path string, reverseDepth int) (string, error) {
	candidate := filepath.Join(path, searchName)
	info, err := os.Stat(candidate)
	if err == nil {
		if info.IsDir() {
			return "", fmt.Errorf("RootDir found directory %q, expected a regular file", candidate)
		}
		return path, nil
	}

	if reverseDepth > 0 {
		parent := filepath.Dir(path)
		if parent == path {
			return "", nil
		}
		return walkRootDir(searchName, parent, reverseDepth-1)
	}

	return "", nil
}