codifier/path.go

// Copyright 2020 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

package codifier

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

// Resolves the current name to a full path, given the current base, home, and
// current directories.
func resolve(baseDir, homeDir, currentDir, name string) string {
	if strings.HasPrefix(name, "//") {
		return filepath.Join(baseDir, name[2:])
	}

	if strings.HasPrefix(name, "/") {
		return name
	}

	if strings.HasPrefix(name, "~") {
		return filepath.Join(homeDir, name[1:])
	}

	return filepath.Join(currentDir, name)
}

// resolveGnPath makes the given path absolute by resolving the home directory,
// the given baseDir or the current directory depending on the path prefix. The
// home directory case handles paths that start with "~". The baseDir may be
// absolute or relative to the home directory. Paths that start with "//"" are
// made absolute relative to the baseDir.
func resolveGnPath(baseDir, filename string) (string, error) {
	home, err := os.UserHomeDir()
	if err != nil {
		return "", fmt.Errorf("can't find user home directory: %w", err)
	}

	if strings.HasPrefix(baseDir, "~") {
		baseDir = filepath.Join(home, baseDir[1:])
	} else {
		if !strings.HasPrefix(baseDir, "/") {
			baseDir = filepath.Join(home, baseDir)
		}
	}

	cwd, err := os.Getwd()
	if err != nil {
		return "", fmt.Errorf("can't obtain working directory: %w", err)
	}

	return resolve(baseDir, home, cwd, filename), nil
}

// SplitGNBuildTarget returns the BUILD absolute filepath and the target given a
// gn build target. For example, "//path/to/test:target" would return
// "/usr/home/foo/fuchsia/path/to/test/BUILD.gn" and "target".
func SplitGNBuildTarget(fuchsiaHome, targetPath string) (string, string, error) {
	parts := strings.Split(targetPath, ":")
	if len(parts) != 2 {
		return "", "", fmt.Errorf("can't find ':' separator in string %q", targetPath)
	}
	buildPath, target := parts[0], parts[1]
	dirPath, err := resolveGnPath(fuchsiaHome, buildPath)
	if err != nil {
		return "", "", err
	}
	buildFile := filepath.Join(dirPath, "BUILD.gn")
	return buildFile, target, nil
}