//go:build mage

package main

import (
	"errors"
	"fmt"
	"io/fs"
	"os"
	"path/filepath"
	"slices"
	"strings"

	"github.com/magefile/mage/sh"
)

// Files ensure that the configuration files in the managed directory is up to date and
// ensures that they are symlinked correctly to the files in the user's home configuration
// directory.
func Files() error {
	homeConfigDirectory, err := os.UserConfigDir()
	if err != nil {
		return fmt.Errorf("unable to get the user's home configuration directory: %w", err)
	}

	if err = filepath.WalkDir(rootFilesDir, manageFilesFunc(homeConfigDirectory)); err != nil {
		return fmt.Errorf("received an error while processing the files: %w", err)
	}

	return nil
}

func manageFilesFunc(homeConfigDirectory string) fs.WalkDirFunc {
	return func(path string, d fs.DirEntry, err error) error {
		if err != nil {
			return err
		}

		if path == rootFilesDir {
			return nil
		}

		relativePath := strings.TrimPrefix(path, rootFilesDir+"/")

		managedPath := filepath.Join(rootManagedDir, relativePath)
		configPath := filepath.Join(homeConfigDirectory, relativePath)

		if d.IsDir() {
			dirs := []string{managedPath, configPath}

			for _, dir := range slices.All(dirs) {
				if err := ensureDirectory(dir); err != nil {
					return fmt.Errorf("unable to ensure the existence of the directory %q: %w", dir, err)
				}
			}

			return nil
		}

		if err := sh.Copy(managedPath, path); err != nil {
			return fmt.Errorf("unable to copy %s to %s: %w", path, managedPath, err)
		}

		if err := ensureSymlink(managedPath, configPath); err != nil {
			return err
		}

		return nil
	}
}

func ensureSymlink(source, dest string) error {
	absolutePathErrorMessageFormat := "unable to get the absolute path to %s: %w"

	absoluteSourcePath, err := filepath.Abs(source)
	if err != nil {
		return fmt.Errorf(absolutePathErrorMessageFormat, source, err)
	}

	absoluteDestPath, err := filepath.Abs(dest)
	if err != nil {
		return fmt.Errorf(absolutePathErrorMessageFormat, dest, err)
	}

	destInfo, err := os.Lstat(absoluteDestPath)
	if err != nil {
		if errors.Is(err, os.ErrNotExist) {
			fmt.Printf("Linking %s to %s\n", absoluteDestPath, absoluteSourcePath)

			if err := os.Symlink(absoluteSourcePath, absoluteDestPath); err != nil {
				return fmt.Errorf(
					"unable to symlink %s to %s: %w",
					absoluteDestPath,
					absoluteSourcePath,
					err,
				)
			}

			return nil
		}

		return fmt.Errorf("unable to get the file info for %s: %w", absoluteDestPath, err)
	}

	if destInfo.Mode().Type() != fs.ModeSymlink {
		return fmt.Errorf("the path %s exists but it is not a symlink", absoluteDestPath)
	}

	destLinksTo, err := filepath.EvalSymlinks(absoluteDestPath)
	if err != nil {
		return fmt.Errorf("unable to evaluate the symlink %s: %w", absoluteDestPath, err)
	}

	if destLinksTo == absoluteSourcePath {
		return nil
	}

	fmt.Printf(
		"%s should link back to %s but instead links back to %s\n",
		absoluteDestPath,
		absoluteSourcePath,
		destLinksTo,
	)

	fmt.Println("Recreating:", absoluteDestPath)

	if err := os.Remove(absoluteDestPath); err != nil {
		return fmt.Errorf("unable to remove %s: %w", absoluteDestPath, err)
	}

	if err := os.Symlink(absoluteSourcePath, absoluteDestPath); err != nil {
		return fmt.Errorf(
			"unable to symlink %s to %s: %w",
			absoluteDestPath,
			absoluteSourcePath,
			err,
		)
	}

	return nil
}