/*
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * This software may be used and distributed according to the terms of the
 * GNU General Public License version 2.
 */

#pragma once

#include <folly/Portability.h>
#include <folly/Range.h>
#include <sys/statvfs.h>
#include "eden/fs/fuse/BufVec.h"
#include "eden/fs/fuse/FuseTypes.h"
#include "eden/fs/fuse/InodeNumber.h"
#include "eden/fs/store/IObjectStore.h"
#include "eden/fs/utils/PathFuncs.h"

namespace folly {
template <class T>
class Future;
} // namespace folly

namespace facebook {
namespace eden {

#define FUSELL_NOT_IMPL()                                               \
  do {                                                                  \
    LOG_FIRST_N(ERROR, 1) << __PRETTY_FUNCTION__ << " not implemented"; \
    folly::throwSystemErrorExplicit(ENOSYS, __PRETTY_FUNCTION__);       \
  } while (0)

class DirList;
class Dispatcher;
class EdenStats;
class FileHandle;
class MountPoint;
class RequestData;

class Dispatcher {
  fuse_init_out connInfo_{};
  EdenStats* stats_{nullptr};

 public:
  virtual ~Dispatcher();

  explicit Dispatcher(EdenStats* stats);
  EdenStats* getStats() const;

  const fuse_init_out& getConnInfo() const;

  /**
   * Called during filesystem mounting.  It informs the filesystem
   * of kernel capabilities and provides an opportunity to poke some
   * flags and limits in the conn_info to report capabilities back
   * to the kernel
   */
  virtual void initConnection(const fuse_init_out& out);

  /**
   * Called when fuse is tearing down the session
   */
  virtual void destroy();

  /**
   * Lookup a directory entry by name and get its attributes
   */
  virtual folly::Future<fuse_entry_out> lookup(
      InodeNumber parent,
      PathComponentPiece name);

  /**
   * Forget about an inode
   *
   * The nlookup parameter indicates the number of lookups
   * previously performed on this inode.
   *
   * If the filesystem implements inode lifetimes, it is recommended
   * that inodes acquire a single reference on each lookup, and lose
   * nlookup references on each forget.
   *
   * The filesystem may ignore forget calls, if the inodes don't
   * need to have a limited lifetime.
   *
   * On unmount, it is not guaranteed that all referenced inodes
   * will receive a forget message.
   *
   * @param ino the inode number
   * @param nlookup the number of lookups to forget
   */
  virtual void forget(InodeNumber ino, unsigned long nlookup);

  /**
   * The stat information and the cache TTL for the kernel
   *
   * The timeout value is measured in seconds and indicates how long
   * the kernel side of the FUSE will cache the values in the
   * struct stat before calling getattr() again to refresh it.
   */
  struct Attr {
    struct stat st;
    uint64_t timeout_seconds;

    explicit Attr(
        const struct stat& st,
        // We want an ostensibly infinite TTL for the attributes
        // we send to the kernel, but need to take care as the
        // macOS fuse kext implementation casts this to a signed
        // value and adds it to another timespec to compute the
        // absolute deadline.  If we make the value the maximum
        // possible unsigned 64 bit value the deadline overflows
        // and we never achieve a cache hit.  Limiting ourselves
        // to the maximum possible signed 32 bit value gives us
        // ta large and effective timeout
        uint64_t timeout = std::numeric_limits<int32_t>::max());

    fuse_attr_out asFuseAttr() const;
  };

  /**
   * Get file attributes
   *
   * @param ino the inode number
   */
  virtual folly::Future<Attr> getattr(InodeNumber ino);

  /**
   * Set file attributes
   *
   * In the 'attr' argument only members indicated by the 'to_set'
   * bitmask contain valid values.  Other members contain undefined
   * values.
   *
   * @param ino the inode number
   * @param attr the attributes
   * @param to_set bit mask of attributes which should be set
   *
   * Changed in version 2.5:
   *     file information filled in for ftruncate
   */
  virtual folly::Future<Attr> setattr(
      InodeNumber ino,
      const fuse_setattr_in& attr);

  /**
   * Read symbolic link
   *
   * @param ino the inode number
   * @param kernelCachesReadlink whether the kernel supports caching readlink
   * calls.
   */
  virtual folly::Future<std::string> readlink(
      InodeNumber ino,
      bool kernelCachesReadlink);

  /**
   * Create file node
   *
   * Create a regular file, character device, block device, fifo or
   * socket node.
   *
   * @param parent inode number of the parent directory
   * @param name to create
   * @param mode file type and mode with which to create the new file
   * @param rdev the device number (only valid if created file is a device)
   */
  virtual folly::Future<fuse_entry_out>
  mknod(InodeNumber parent, PathComponentPiece name, mode_t mode, dev_t rdev);

  /**
   * Create a directory
   *
   * @param parent inode number of the parent directory
   * @param name to create
   * @param mode with which to create the new file
   */
  virtual folly::Future<fuse_entry_out>
  mkdir(InodeNumber parent, PathComponentPiece name, mode_t mode);

  /**
   * Remove a file
   *
   * @param parent inode number of the parent directory
   * @param name to remove
   */
  FOLLY_NODISCARD virtual folly::Future<folly::Unit> unlink(
      InodeNumber parent,
      PathComponentPiece name);

  /**
   * Remove a directory
   *
   * @param parent inode number of the parent directory
   * @param name to remove
   */
  FOLLY_NODISCARD virtual folly::Future<folly::Unit> rmdir(
      InodeNumber parent,
      PathComponentPiece name);

  /**
   * Create a symbolic link
   *
   * @param parent inode number of the parent directory
   * @param name to create
   * @param link the contents of the symbolic link
   */
  virtual folly::Future<fuse_entry_out>
  symlink(InodeNumber parent, PathComponentPiece name, folly::StringPiece link);

  /**
   * Rename a file
   *
   * @param parent inode number of the old parent directory
   * @param name old name
   * @param newparent inode number of the new parent directory
   * @param newname new name
   */
  FOLLY_NODISCARD virtual folly::Future<folly::Unit> rename(
      InodeNumber parent,
      PathComponentPiece name,
      InodeNumber newparent,
      PathComponentPiece newname);

  /**
   * Create a hard link
   *
   * @param ino the old inode number
   * @param newparent inode number of the new parent directory
   * @param newname new name to create
   */
  virtual folly::Future<fuse_entry_out>
  link(InodeNumber ino, InodeNumber newparent, PathComponentPiece newname);

  /**
   * Open a file
   *
   * open(2) flags (with the exception of O_CREAT, O_EXCL, O_NOCTTY and
   * O_TRUNC) are available in the flags parameter.
   *
   * The returned fh value will be passed to release.
   */
  virtual folly::Future<uint64_t> open(InodeNumber ino, int flags);

  /**
   * Release an open file
   *
   * Release is called when there are no more references to an open file: all
   * file descriptors are closed and all memory mappings are unmapped.
   *
   * For every open call there will be exactly one release call.
   *
   * The filesystem may reply with an error, but error values are not returned
   * to close() or munmap() which triggered the release.
   *
   * fh will contain the value returned by the open method.
   */
  virtual folly::Future<folly::Unit> release(InodeNumber ino, uint64_t fh);

  /**
   * Open a directory
   *
   * open(2) flags are available in the flags parameter.
   *
   * The return value will be given to releasedir and readdir.
   */
  virtual folly::Future<uint64_t> opendir(InodeNumber ino, int flags);

  /**
   * Release an open directory
   *
   * For every opendir call there will be exactly one releasedir call. (Except
   * during unmount - further releasedir calls are not sent.) The fh parameter
   * contains the result of opendir.
   */
  virtual folly::Future<folly::Unit> releasedir(InodeNumber ino, uint64_t fh);

  /**
   * Read data
   *
   * Read should send exactly the number of bytes requested except
   * on EOF or error, otherwise the rest of the data will be
   * substituted with zeroes.  An exception to this is when the file
   * has been opened in 'direct_io' mode, in which case the return
   * value of the read system call will reflect the return value of
   * this operation.
   *
   * @param size number of bytes to read
   * @param off offset to read from
   */
  virtual folly::Future<BufVec>
  read(InodeNumber ino, size_t size, off_t off, ObjectFetchContext& context);

  /**
   * Write data
   *
   * Write should return exactly the number of bytes requested
   * except on error.  An exception to this is when the file has
   * been opened in 'direct_io' mode, in which case the return value
   * of the write system call will reflect the return value of this
   * operation.
   */
  FOLLY_NODISCARD virtual folly::Future<size_t>
  write(InodeNumber ino, folly::StringPiece data, off_t off);

  /**
   * This is called on each close() of the opened file.
   *
   * Since file descriptors can be duplicated (dup, dup2, fork), for
   * one open call there may be many flush calls.
   *
   * Filesystems shouldn't assume that flush will always be called
   * after some writes, or that if will be called at all.
   *
   * NOTE: the name of the method is misleading, since (unlike
   * fsync) the filesystem is not forced to flush pending writes.
   * One reason to flush data, is if the filesystem wants to return
   * write errors.
   *
   * If the filesystem supports file locking operations (setlk,
   * getlk) it should remove all locks belonging to 'lock_owner'.
   */
  FOLLY_NODISCARD virtual folly::Future<folly::Unit> flush(
      InodeNumber ino,
      uint64_t lock_owner);

  /**
   * Ensure file content changes are flushed to disk.
   *
   * If the datasync parameter is true, then only the user data should be
   * flushed, not the meta data.
   */
  FOLLY_NODISCARD virtual folly::Future<folly::Unit> fsync(
      InodeNumber ino,
      bool datasync);

  /**
   * Ensure directory content changes are flushed to disk.
   *
   * If the datasync parameter is true, then only the directory contents should
   * be flushed, not the metadata.
   */
  FOLLY_NODISCARD virtual folly::Future<folly::Unit> fsyncdir(
      InodeNumber ino,
      bool datasync);

  /**
   * Read directory.
   *
   * Send a DirList filled using DirList::add().
   * Send an empty DirList on end of stream.
   *
   * The fh parameter contains opendir's result.
   */
  virtual folly::Future<DirList>
  readdir(InodeNumber ino, DirList&& dirList, off_t offset, uint64_t fh);

  /**
   * Get file system statistics
   *
   * @param ino the inode number, zero means "undefined"
   */
  virtual folly::Future<struct fuse_kstatfs> statfs(InodeNumber ino);

  /**
   * Set an extended attribute
   */
  FOLLY_NODISCARD virtual folly::Future<folly::Unit> setxattr(
      InodeNumber ino,
      folly::StringPiece name,
      folly::StringPiece value,
      int flags);
  /**
   * Get an extended attribute
   */
  virtual folly::Future<std::string> getxattr(
      InodeNumber ino,
      folly::StringPiece name);
  static const int kENOATTR;

  /**
   * List extended attribute names
   */
  virtual folly::Future<std::vector<std::string>> listxattr(InodeNumber ino);

  /**
   * Remove an extended attribute
   *
   * @param ino the inode number
   * @param name of the extended attribute
   */
  FOLLY_NODISCARD virtual folly::Future<folly::Unit> removexattr(
      InodeNumber ino,
      folly::StringPiece name);

  /**
   * Check file access permissions
   *
   * This will be called for the access() system call.  If the
   * 'default_permissions' mount option is given, this method is not
   * called.
   *
   * This method is not called under Linux kernel versions 2.4.x
   *
   * Introduced in version 2.5
   *
   * @param ino the inode number
   * @param mask requested access mode
   */
  FOLLY_NODISCARD virtual folly::Future<folly::Unit> access(
      InodeNumber ino,
      int mask);

  /**
   * Create and open a file
   *
   * If the file does not exist, first create it with the specified
   * mode, and then open it.
   *
   * Open flags (with the exception of O_NOCTTY) are available in
   * fi->flags.
   *
   * If this method is not implemented or under Linux kernel
   * versions earlier than 2.6.15, the mknod() and open() methods
   * will be called instead.
   *
   * Introduced in version 2.5
   *
   * @param parent inode number of the parent directory
   * @param name to create
   * @param mode file type and mode with which to create the new file
   */
  virtual folly::Future<fuse_entry_out>
  create(InodeNumber parent, PathComponentPiece name, mode_t mode, int flags);

  /**
   * Map block index within file to block index within device
   *
   * Note: This makes sense only for block device backed filesystems
   * mounted with the 'blkdev' option
   *
   * Introduced in version 2.6
   *
   * @param ino the inode number
   * @param blocksize unit of block index
   * @param idx block index within file
   */
  virtual folly::Future<uint64_t>
  bmap(InodeNumber ino, size_t blocksize, uint64_t idx);
};

} // namespace eden
} // namespace facebook