package scaffold

import (
	"bytes"
	"io/fs"
	"os"
	"path/filepath"
	"strings"

	"congo.gg"
)

// ExtractPackages copies framework packages from the embedded pkg/ source
// into targetDir/internal/<package>/, rewriting imports to the new module path.
func ExtractPackages(targetDir, newModule string, packages []string) error {
	const pkgRoot = "pkg/"
	oldImport := []byte("congo.gg/pkg/")
	newImport := []byte(newModule + "/internal/")

	for _, pkg := range packages {
		root := pkgRoot + pkg
		err := fs.WalkDir(congo.SourceFS, root, func(path string, d fs.DirEntry, err error) error {
			if err != nil {
				return err
			}

			outRel := "internal/" + strings.TrimPrefix(path, pkgRoot)
			outPath := filepath.Join(targetDir, outRel)

			if d.IsDir() {
				return os.MkdirAll(outPath, 0755)
			}

			if strings.HasSuffix(path, "_test.go") {
				return nil
			}

			content, err := fs.ReadFile(congo.SourceFS, path)
			if err != nil {
				return err
			}

			if strings.HasSuffix(path, ".go") {
				content = bytes.ReplaceAll(content, oldImport, newImport)
			}

			return os.WriteFile(outPath, content, 0644)
		})
		if err != nil {
			return err
		}
	}
	return nil
}