package migrate

import (
	"errors"
	"fmt"
	"io"
	"io/fs"
	"path/filepath"

	"ariga.io/atlas/sql/migrate"
)

var _ migrate.Dir = (*readOnlyFSDir)(nil)

type readOnlyFSDir struct {
	fs.FS
}

func (m readOnlyFSDir) WriteFile(string, []byte) error {
	return errors.New("migration directory is read-only")
}

func (m readOnlyFSDir) Files() ([]migrate.File, error) {
	files, err := fs.ReadDir(m, ".")
	if err != nil {
		return nil, err
	}

	filesList := make([]migrate.File, 0, len(files))

	for idx := range files {
		f := files[idx]
		if f.IsDir() || filepath.Ext(f.Name()) != ".sql" {
			continue
		}

		scriptFile, err := m.Open(f.Name())
		if err != nil {
			return nil, fmt.Errorf("failed to open %s: %w", f.Name(), err)
		}

		defer func() {
			_ = scriptFile.Close()
		}()

		scriptData, err := io.ReadAll(scriptFile)
		if err != nil {
			return nil, fmt.Errorf("failed to read %s: %w", f.Name(), err)
		}

		filesList = append(filesList, migrate.NewLocalFile(f.Name(), scriptData))
	}

	return filesList, nil
}

func (m readOnlyFSDir) Checksum() (migrate.HashFile, error) {
	var hf migrate.HashFile

	f, err := m.Open(migrate.HashFileName)
	if err != nil {
		return nil, err
	}

	defer func() {
		_ = f.Close()
	}()

	sumData, err := io.ReadAll(f)
	if err != nil {
		return nil, fmt.Errorf("failed to %s: %w", migrate.HashFileName, err)
	}

	if err := hf.UnmarshalText(sumData); err != nil {
		return nil, fmt.Errorf("failed to unmarshal %s: %w", migrate.HashFileName, err)
	}

	return hf, nil
}