package healthcheck

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

// fileExists checks if a file exists at the specified path.
func fileExists(filePath string) bool {
	_, err := os.Stat(filePath)
	return !os.IsNotExist(err)
}

// filesMatch checks if two files are identical.
func filesMatch(file1, file2 string) (bool, error) {
	f1, err := os.Open(file1)
	if err != nil {
		return false, err
	}
	defer f1.Close()

	f2, err := os.Open(file2)
	if err != nil {
		return false, err
	}
	defer f2.Close()

	scanner1 := bufio.NewScanner(f1)
	scanner2 := bufio.NewScanner(f2)

	for scanner1.Scan() && scanner2.Scan() {
		line1 := scanner1.Text()
		line2 := scanner2.Text()

		if line1 != line2 {
			return false, nil
		}
	}

	if scanner1.Scan() || scanner2.Scan() {
		// One file has more lines than the other
		return false, nil
	}

	return true, nil
}

// VerifyDirectory checks if the contents of two directories are identical.
func VerifyDirectory(rootDir, compareDir string) error {
	err := filepath.Walk(rootDir, func(path string, info os.FileInfo, err error) error {
		if err != nil {
			return fmt.Errorf("error walking directory: %w", err)
		}
		if !info.IsDir() {
			relPath, _ := filepath.Rel(rootDir, path)
			file2 := filepath.Join(compareDir, relPath)
			if !fileExists(file2) {
				return fmt.Errorf("File %s is missing. Please immediately revert your changes!\n",
					filepath.Join(rootDir, relPath))
			}
			match, err := filesMatch(path, file2)
			if err != nil {
				return fmt.Errorf("error matching files: %w", err)
			}
			if !match {
				return fmt.Errorf("File %s is altered. Please revert your changes or contact the teaching team if you have a valid reason for adjusting them.\n",
					filepath.Join(rootDir, relPath))
			}
		}
		return nil
	})
	return err
}