package files

import (
	"context"
	"errors"
	"fmt"
	"os"
	"path/filepath"
)

var ErrInstanceDataDirectoryUnavailable = errors.New("instance data directory is unavailable")

// DirectoryPreparer verifies one explicitly supplied absolute directory.
// It is used for program-owned locations such as the configured log folder.
type DirectoryPreparer interface {
	PrepareDirectory(context.Context, string) error
}

// InstanceDataPreparer creates and verifies only the User Data Dir belonging
// to the explicitly requested instance. It never discovers or changes other
// browser data directories.
type InstanceDataPreparer interface {
	PrepareInstanceDataDir(context.Context, string) error
}

type instanceDataPreparer struct {
	mkdirAll   func(string, os.FileMode) error
	lstat      func(string) (os.FileInfo, error)
	createTemp func(string, string) (*os.File, error)
	remove     func(string) error
}

func NewInstanceDataPreparer() InstanceDataPreparer {
	return newInstanceDataPreparer(os.MkdirAll, os.Lstat, os.CreateTemp, os.Remove)
}

func NewDirectoryPreparer() DirectoryPreparer {
	return newInstanceDataPreparer(os.MkdirAll, os.Lstat, os.CreateTemp, os.Remove)
}

func newInstanceDataPreparer(
	mkdirAll func(string, os.FileMode) error,
	lstat func(string) (os.FileInfo, error),
	createTemp func(string, string) (*os.File, error),
	remove func(string) error,
) instanceDataPreparer {
	return instanceDataPreparer{mkdirAll: mkdirAll, lstat: lstat, createTemp: createTemp, remove: remove}
}

func (p instanceDataPreparer) PrepareInstanceDataDir(ctx context.Context, userDataDir string) error {
	return p.PrepareDirectory(ctx, userDataDir)
}

func (p instanceDataPreparer) PrepareDirectory(ctx context.Context, directory string) error {
	if err := ctx.Err(); err != nil {
		return err
	}
	path, err := normalizePreparatoryInstanceDataDir(directory)
	if err != nil {
		return err
	}
	if err := p.mkdirAll(path, 0o700); err != nil {
		return fmt.Errorf("%w: create", ErrInstanceDataDirectoryUnavailable)
	}
	if err := ctx.Err(); err != nil {
		return err
	}
	info, err := p.lstat(path)
	if err != nil {
		return fmt.Errorf("%w: inspect", ErrInstanceDataDirectoryUnavailable)
	}
	if info.Mode()&(os.ModeSymlink|os.ModeIrregular) != 0 || isReparsePoint(info) {
		return fmt.Errorf("%w: links and reparse points are not supported", ErrUnsafeInstanceDataDirectory)
	}
	if !info.IsDir() {
		return ErrInstanceDataNotDirectory
	}
	probe, err := p.createTemp(path, ".chub-write-*")
	if err != nil {
		return fmt.Errorf("%w: write", ErrInstanceDataDirectoryUnavailable)
	}
	probePath := probe.Name()
	if err := probe.Close(); err != nil {
		_ = p.remove(probePath)
		return fmt.Errorf("%w: close", ErrInstanceDataDirectoryUnavailable)
	}
	if err := p.remove(probePath); err != nil && !errors.Is(err, os.ErrNotExist) {
		return fmt.Errorf("%w: cleanup", ErrInstanceDataDirectoryUnavailable)
	}
	if err := ctx.Err(); err != nil {
		return err
	}
	return nil
}

// normalizePreparatoryInstanceDataDir is kept separate from deletion's
// helper so callers can use a stable, intention-revealing validation entry.
func normalizePreparatoryInstanceDataDir(value string) (string, error) {
	path, err := normalizeRemovableInstanceDataDir(value)
	if err != nil {
		return "", err
	}
	return filepath.Clean(path), nil
}