// Copyright 2017, Pulumi Corporation.  All rights reserved.

package engine

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

	"github.com/pkg/errors"

	"github.com/pulumi/pulumi/pkg/workspace"
)

type Projinfo struct {
	Proj *workspace.Project
	Root string
}

// GetPwdMain returns the working directory and main entrypoint to use for this package.
func (projinfo *Projinfo) GetPwdMain() (string, string, error) {
	pwd := projinfo.Root
	main := projinfo.Proj.Main
	if main == "" {
		main = "."
	} else {
		// The path must be relative from the package root.
		if filepath.IsAbs(main) {
			return "", "", errors.New("project 'main' must be a relative path")
		}

		// Check that main is a subdirectory.
		cleanPwd := filepath.Clean(pwd)
		main = filepath.Clean(path.Join(cleanPwd, main))
		if !strings.HasPrefix(main, cleanPwd) {
			return "", "", errors.New("project 'main' must be a subfolder")
		}

		// So that any relative paths inside of the program are correct, we still need to pass the pwd
		// of the main program's parent directory.  How we do this depends on if the target is a dir or not.
		maininfo, err := os.Stat(main)
		if err != nil {
			return "", "", errors.Wrapf(err, "project 'main' could not be read")
		}
		if maininfo.IsDir() {
			pwd = main
			main = "."
		} else {
			pwd = filepath.Dir(main)
			main = filepath.Base(main)
		}
	}

	// Now turn both pwd and main into absolute directories.
	var err error
	pwd, err = filepath.Abs(pwd)
	if err != nil {
		return "", "", err
	}
	main, err = filepath.Abs(main)
	if err != nil {
		return "", "", err
	}

	return pwd, main, nil
}