// Copyright (c) 2009 The Go Authors. All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
// ----------
// The following has been slightly modified from golang.org/x/net/webdav
// to allow context/request specific subdirectories, which could be
// derived from the authentication information.

package main

import (
	"context"
	"fmt"
	"os"
	"path"
	"path/filepath"
	"strings"

	"golang.org/x/net/webdav"
)

type DirectoryMapping struct {
	DataDirName string
	ReadOnly    bool
}

// slashClean is equivalent to but slightly more efficient than
// path.Clean("/" + name).
func slashClean(name string) string {
	if name == "" || name[0] != '/' {
		name = "/" + name
	}
	return path.Clean(name)
}

type BaseDir string

func (d BaseDir) resolve(ctx context.Context, name string) string {
	directoryMapping := ctx.Value("mapping").(*DirectoryMapping)

	// This implementation is based on Dir.Open's code in the standard net/http package.
	if filepath.Separator != '/' && strings.IndexRune(name, filepath.Separator) >= 0 ||
		strings.Contains(name, "\x00") {
		return ""
	}
	dir := string(d)
	if dir == "" {
		dir = "."
	}
	return filepath.Join(dir, directoryMapping.DataDirName, filepath.FromSlash(slashClean(name)))
}

func (d BaseDir) Mkdir(ctx context.Context, name string, perm os.FileMode) error {
	directoryMapping := ctx.Value("mapping").(*DirectoryMapping)
	if directoryMapping.ReadOnly {
		return fmt.Errorf("forbidden")
	}

	if name = d.resolve(ctx, name); name == "" {
		return os.ErrNotExist
	}
	return os.Mkdir(name, perm)
}

func (d BaseDir) OpenFile(ctx context.Context, name string, flag int, perm os.FileMode) (webdav.File, error) {
	directoryMapping := ctx.Value("mapping").(*DirectoryMapping)

	const writeFlags = os.O_APPEND | os.O_CREATE | os.O_RDWR | os.O_WRONLY | os.O_TRUNC
	if flag&writeFlags != 0 && directoryMapping.ReadOnly {
		return nil, fmt.Errorf("forbidden")
	}

	if name = d.resolve(ctx, name); name == "" {
		return nil, os.ErrNotExist
	}
	f, err := os.OpenFile(name, flag, perm)
	if err != nil {
		return nil, err
	}
	return f, nil
}

func (d BaseDir) RemoveAll(ctx context.Context, name string) error {
	directoryMapping := ctx.Value("mapping").(*DirectoryMapping)
	if directoryMapping.ReadOnly {
		return fmt.Errorf("forbidden")
	}

	if name = d.resolve(ctx, name); name == "" {
		return os.ErrNotExist
	}
	if name == filepath.Clean(string(d)) {
		// Prohibit removing the virtual root directory.
		return os.ErrInvalid
	}
	return os.RemoveAll(name)
}

func (d BaseDir) Rename(ctx context.Context, oldName, newName string) error {
	directoryMapping := ctx.Value("mapping").(*DirectoryMapping)
	if directoryMapping.ReadOnly {
		return fmt.Errorf("forbidden")
	}

	if oldName = d.resolve(ctx, oldName); oldName == "" {
		return os.ErrNotExist
	}
	if newName = d.resolve(ctx, newName); newName == "" {
		return os.ErrNotExist
	}
	if root := filepath.Clean(string(d)); root == oldName || root == newName {
		// Prohibit renaming from or to the virtual root directory.
		return os.ErrInvalid
	}
	return os.Rename(oldName, newName)
}

func (d BaseDir) Stat(ctx context.Context, name string) (os.FileInfo, error) {
	if name = d.resolve(ctx, name); name == "" {
		return nil, os.ErrNotExist
	}
	return os.Stat(name)
}