package virtfs

import (
	"fmt"
	"os"
	"strings"
)

// GenerateHelp produces documentation from a filesystem spec tree.
func GenerateHelp(root FsNodeDecl) string {
	return generateHelp(root, "")
}

func generateHelp(node FsNodeDecl, prefix string) string {
	var sb strings.Builder

	path := node.Name
	if prefix != "" {
		path = prefix + "/" + node.Name
	}
	if node.Name == "/" {
		path = ""
	}

	if node.Desc != "" {
		displayPath := path
		if displayPath == "" {
			displayPath = "/"
		}
		mode := node.Mode
		if len(node.Children) > 0 || node.Bindings != nil {
			mode = 0755 | os.ModeDir
		}
		fmt.Fprintf(&sb, "%-40s %s  %s\n", displayPath, fmtMode(mode), node.Desc)
	}

	for _, child := range node.Children {
		sb.WriteString(generateHelp(child, path))
	}

	return sb.String()
}

func fmtMode(m os.FileMode) string {
	if m == 0 {
		return "----"
	}
	var buf [4]byte
	buf[0] = '-'
	if m.IsDir() {
		buf[0] = 'd'
	}
	buf[1] = 'r'
	if m&0200 != 0 {
		buf[1] = 'w'
	}
	if m&0400 != 0 {
		buf[2] = 'r'
	} else {
		buf[2] = '-'
	}
	if m&0100 != 0 {
		buf[3] = 'x'
	} else {
		buf[3] = '-'
	}
	return string(buf[:])
}