package seed

import (
	"errors"
	"io"
	"os"
	"path/filepath"
)

// CopySeedDir recursively copies the contents of srcDir into dstDir.
// Files at the destination are overwritten. Subdirectories are preserved.
//
// The following entries at the top level of srcDir are intentionally skipped:
//   - task.yaml (ctask owns this file)
//   - .ctask    (directory; reserved for ctask metadata)
//
// If srcDir does not exist, this function returns nil (no-op). Other I/O errors
// are returned to the caller.
func CopySeedDir(srcDir, dstDir string) error {
	info, err := os.Stat(srcDir)
	if err != nil {
		if errors.Is(err, os.ErrNotExist) {
			return nil
		}
		return err
	}
	if !info.IsDir() {
		return nil
	}

	entries, err := os.ReadDir(srcDir)
	if err != nil {
		return err
	}

	for _, entry := range entries {
		name := entry.Name()
		if name == "task.yaml" || name == ".ctask" {
			continue
		}
		srcPath := filepath.Join(srcDir, name)
		dstPath := filepath.Join(dstDir, name)
		if err := copyEntry(srcPath, dstPath); err != nil {
			return err
		}
	}
	return nil
}

func copyEntry(src, dst string) error {
	info, err := os.Stat(src)
	if err != nil {
		return err
	}
	if info.IsDir() {
		if err := os.MkdirAll(dst, 0755); err != nil {
			return err
		}
		entries, err := os.ReadDir(src)
		if err != nil {
			return err
		}
		for _, e := range entries {
			if err := copyEntry(filepath.Join(src, e.Name()), filepath.Join(dst, e.Name())); err != nil {
				return err
			}
		}
		return nil
	}
	return copyFile(src, dst, info.Mode())
}

func copyFile(src, dst string, mode os.FileMode) error {
	in, err := os.Open(src)
	if err != nil {
		return err
	}
	defer in.Close()

	if err := os.MkdirAll(filepath.Dir(dst), 0755); err != nil {
		return err
	}
	out, err := os.OpenFile(dst, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, mode.Perm())
	if err != nil {
		return err
	}
	defer out.Close()

	if _, err := io.Copy(out, in); err != nil {
		return err
	}
	return nil
}