package filer

import (
	"context"
	"fmt"
	"io"
	"io/fs"
)

// WriteMode captures intent when writing a file.
//
// The first 9 bits are reserved for the [fs.FileMode] permission bits.
// These are used only by the local filer implementation and have
// no effect for the other implementations.
type WriteMode int

// writeModePerm is a mask to extract permission bits from a WriteMode.
const writeModePerm = WriteMode(fs.ModePerm)

const (
	// Note: these constants are defined as powers of 2 to support combining them using a bit-wise OR.
	// They starts from the 10th bit (permission mask + 1) to avoid conflicts with the permission bits.
	OverwriteIfExists WriteMode = (writeModePerm + 1) << iota
	CreateParentDirectories
)

// DeleteMode captures intent when deleting a file.
type DeleteMode int

const (
	DeleteRecursively DeleteMode = 1 << iota
)

type FileAlreadyExistsError struct {
	path string
}

func (err FileAlreadyExistsError) Error() string {
	return fmt.Sprintf("file already exists: %s", err.path)
}

func (err FileAlreadyExistsError) Is(other error) bool {
	return other == fs.ErrExist
}

type FileDoesNotExistError struct {
	path string
}

func (err FileDoesNotExistError) Is(other error) bool {
	return other == fs.ErrNotExist
}

func (err FileDoesNotExistError) Error() string {
	return fmt.Sprintf("file does not exist: %s", err.path)
}

type NoSuchDirectoryError struct {
	path string
}

func (err NoSuchDirectoryError) Error() string {
	return fmt.Sprintf("no such directory: %s", err.path)
}

func (err NoSuchDirectoryError) Is(other error) bool {
	return other == fs.ErrNotExist
}

type NotADirectory struct {
	path string
}

func (err NotADirectory) Error() string {
	return fmt.Sprintf("not a directory: %s", err.path)
}

func (err NotADirectory) Is(other error) bool {
	return other == fs.ErrInvalid
}

type NotAFile struct {
	path string
}

func (err NotAFile) Error() string {
	return fmt.Sprintf("not a file: %s", err.path)
}

func (err NotAFile) Is(other error) bool {
	return other == fs.ErrInvalid
}

type DirectoryNotEmptyError struct {
	path string
}

func (err DirectoryNotEmptyError) Error() string {
	return fmt.Sprintf("directory not empty: %s", err.path)
}

func (err DirectoryNotEmptyError) Is(other error) bool {
	return other == fs.ErrInvalid
}

type CannotDeleteRootError struct {
}

func (err CannotDeleteRootError) Error() string {
	return "unable to delete filer root"
}

func (err CannotDeleteRootError) Is(other error) bool {
	return other == fs.ErrInvalid
}

type PermissionError struct {
	path string
}

func (err PermissionError) Error() string {
	return fmt.Sprintf("access denied: %s", err.path)
}

func (err PermissionError) Is(other error) bool {
	return other == fs.ErrPermission
}

// Filer is used to access files in a workspace.
// It has implementations for accessing files in WSFS and in DBFS.
type Filer interface {
	// Write file at `path`.
	// Use the mode to further specify behavior.
	Write(ctx context.Context, path string, reader io.Reader, mode ...WriteMode) error

	// Read file at `path`.
	Read(ctx context.Context, path string) (io.ReadCloser, error)

	// Delete file or directory at `path`.
	Delete(ctx context.Context, path string, mode ...DeleteMode) error

	// Return contents of directory at `path`.
	ReadDir(ctx context.Context, path string) ([]fs.DirEntry, error)

	// Creates directory at `path`, creating any intermediate directories as required.
	Mkdir(ctx context.Context, path string) error

	// Stat returns information about the file at `path`.
	Stat(ctx context.Context, name string) (fs.FileInfo, error)
}
