(* Guestfs Browser.
 * Copyright (C) 2010 Red Hat Inc.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 *)

open ExtList
open Printf
open Utils

module C = Libvirt.Connect
module Cond = Condition
module D = Libvirt.Domain
module M = Mutex
module Q = Queue

type 'a callback = 'a -> unit

(* The commands. *)
type command =
  | Exit_thread
  | Connect of string option * domain list callback
  | Open_domain of string * inspection_data callback
  | Open_images of (string * string option) list * inspection_data callback
  | Read_directory of source * string * direntry list callback

and domain = {
  dom_id : int;
  dom_name : string;
  dom_state : D.state;
}

and inspection_data = {
  insp_all_filesystems : (string * string) list;
  insp_oses : inspection_os list;
}

and inspection_os = {
  insp_root : string;
  insp_arch : string;
  insp_distro : string;
  insp_filesystems : string array;
  insp_hostname : string;
  insp_major_version : int;
  insp_minor_version : int;
  insp_mountpoints : (string * string) list;
  insp_package_format : string;
  insp_package_management : string;
  insp_product_name : string;
  insp_type : string;
  insp_windows_systemroot : string option;
}

and source = OS of inspection_os | Volume of string

and direntry = {
  dent_name : string;
  dent_stat : Guestfs.stat;
  dent_link : string;
}

let rec string_of_command = function
  | Exit_thread -> "Exit_thread"
  | Connect (Some name, _) -> sprintf "Connect %s" name
  | Connect (None, _) -> "Connect NULL"
  | Open_domain (name, _) -> sprintf "Open_domain %s" name
  | Open_images (images, _) ->
      sprintf "Open_images %s" (string_of_images images)
  | Read_directory (OS { insp_root = root }, dir, _) ->
      sprintf "Read_directory (OS %s, %s)" root dir
  | Read_directory (Volume dev, dir, _) ->
      sprintf "Read_directory (Volume %s, %s)" dev dir

and string_of_images images =
  "[" ^
    String.concat "; "
    (List.map (function
               | fn, None -> fn
               | fn, Some format -> sprintf "%s (%s)" fn format)
       images) ^ "]"

let no_callback _ = ()

let failure_hook = ref (fun _ -> ())
let busy_hook = ref (fun _ -> ())
let idle_hook = ref (fun _ -> ())
let progress_hook = ref (fun _ -> ())

let set_failure_hook cb = failure_hook := cb
let set_busy_hook cb = busy_hook := cb
let set_idle_hook cb = idle_hook := cb
let set_progress_hook cb = progress_hook := cb

(* Execute a function, while holding a mutex.  If the function
 * fails, ensure we release the mutex before rethrowing the
 * exception.
 *)
let with_lock m f =
  M.lock m;
  let r = try Left (f ()) with exn -> Right exn in
  M.unlock m;
  match r with
  | Left r -> r
  | Right exn -> raise exn

(* The queue of commands, and a lock and condition to protect it. *)
let q = Q.create ()
let q_discard = ref false
let q_lock = M.create ()
let q_cond = Cond.create ()

(* Send a command message to the slave thread. *)
let send_to_slave ?fail cmd =
  debug "sending message %s to slave thread ..." (string_of_command cmd);
  with_lock q_lock (
    fun () ->
      Q.push (fail, cmd) q;
      Cond.signal q_cond
  )

let discard_command_queue () =
  with_lock q_lock (
    fun () ->
      Q.clear q;
      (* Discard the currently running command. *)
      q_discard := true
  )

let connect ?fail uri cb = send_to_slave ?fail (Connect (uri, cb))
let open_domain ?fail name cb = send_to_slave ?fail (Open_domain (name, cb))
let open_images ?fail images cb = send_to_slave ?fail (Open_images (images, cb))
let read_directory ?fail src path cb =
  send_to_slave ?fail (Read_directory (src, path, cb))

(*----- Slave thread starts here -----*)

(* Set this to true to exit the thread. *)
let quit = ref false

(* Handles.  These are not protected by locks because only the slave
 * thread has access to them.
 *)
let conn = ref None
let g = ref None

(* Run the callback unless someone set the q_discard flag while
 * we were running the command.
 *)
let callback_if_not_discarded (cb : 'a callback) (arg : 'a) =
  let discard = with_lock q_lock (fun () -> !q_discard) in
  if not discard then
    GtkThread.async cb arg

(* Call 'f ()' with source mounted read-only.  Ensure that everything
 * is unmounted even if an exception is thrown.
 *)
let with_mount_ro g src (f : unit -> 'a) : 'a =
  Std.finally (fun () -> g#umount_all ()) (
    fun () ->
      (* Do the mount - could be OS or single volume. *)
      (match src with
      | Volume dev -> g#mount_ro dev "/";
      | OS { insp_mountpoints = mps } ->
          (* Sort the mountpoint keys by length, shortest first. *)
          let cmp (a,_) (b,_) = compare (String.length a) (String.length b) in
          let mps = List.sort ~cmp mps in
          (* Mount the filesystems. *)
          List.iter (
            fun (mp, dev) -> g#mount_ro dev mp
          ) mps
      );
      f ()
  ) ()

let rec loop () =
  debug "top of slave loop";

  (* Get the next command. *)
  let fail, cmd =
    with_lock q_lock (
      fun () ->
        while Q.is_empty q do Cond.wait q_cond q_lock done;
        q_discard := false;
        Q.pop q
    ) in

  debug "slave processing command %s ..." (string_of_command cmd);

  (try
     GtkThread.async !busy_hook ();
     execute_command cmd
   with exn ->
     (* If the user provided an override ?fail parameter to the
      * original call, call that, else call the global hook.
      *)
     match fail with
     | Some cb -> GtkThread.async cb exn
     | None -> GtkThread.async !failure_hook exn
  );

  (* If there are no more commands in the queue, run the idle hook. *)
  let empty = with_lock q_lock (fun () -> Q.is_empty q) in
  if empty then GtkThread.async !idle_hook ();

  if !quit then Thread.exit ();
  loop ()

and execute_command = function
  | Exit_thread ->
      quit := true;
      close_all ()

  | Connect (name, cb) ->
      close_all ();
      conn := Some (C.connect_readonly ?name ());

      let conn = get_conn () in
      let doms = D.get_domains conn [D.ListAll] in
      let doms = List.map (
        fun d ->
          { dom_id = D.get_id d;
            dom_name = D.get_name d;
            dom_state = (D.get_info d).D.state }
      ) doms in
      let cmp { dom_name = n1 } { dom_name = n2 } = compare n1 n2 in
      let doms = List.sort ~cmp doms in
      callback_if_not_discarded cb doms

  | Open_domain (name, cb) ->
      let conn = get_conn () in
      let dom = D.lookup_by_name conn name in
      let xml = D.get_xml_desc dom in
      let images = get_disk_images_from_xml xml in
      open_disk_images images cb

  | Open_images (images, cb) ->
      open_disk_images images cb

  | Read_directory (src, dir, cb) ->
      let g = get_g () in
      let names, stats, links =
        with_mount_ro g src (
          fun () ->
            let names = g#ls dir in (* sorted and without . and .. *)
            let names = Array.to_list names in
            let stats = lstatlist_wrapper g dir names in
            let links = readlinklist_wrapper g dir names in
            names, stats, links
        ) in
      assert (
        let n = List.length names in
        n = List.length stats && n = List.length links
      );
      let entries = List.combine (List.combine names stats) links in
      let entries = List.map (
        fun ((name, stat), link) ->
          { dent_name = name; dent_stat = stat; dent_link = link }
      ) entries in
      callback_if_not_discarded cb entries

(* Expect to be connected, and return the current libvirt connection. *)
and get_conn () =
  match !conn with
  | Some conn -> conn
  | None -> failwith "not connected to libvirt"

and get_g () =
  match !g with
  | Some g -> g
  | None -> failwith "no domain or disk image is open"

(* Close all libvirt and libguestfs handles. *)
and close_all () =
  (match !conn with Some conn -> C.close conn | None -> ());
  conn := None;
  close_g ()

and close_g () =
  (match !g with Some g -> g#close () | None -> ());
  g := None

and get_disk_images_from_xml xml =
  let xml = Xml.parse_string xml in

  (* Return the device nodes. *)
  let devices =
    match xml with
    | Xml.Element ("domain", _, children) ->
        let devices =
          List.filter_map (
            function
            | Xml.Element ("devices", _, devices) -> Some devices
            | _ -> None
          ) children in
        List.concat devices
    | _ ->
        failwith "get_xml_desc didn't return <domain/>" in

  (* Look for <source attr_name=attr_val/> and return attr_val. *)
  let rec source_of attr_name = function
    | [] -> None
    | Xml.Element ("source", attrs, _) :: rest ->
        (try Some (List.assoc attr_name attrs)
         with Not_found -> source_of attr_name rest)
    | _ :: rest -> source_of attr_name rest
  in

  (* Look for <driver type=attr_val/> and return attr_val. *)
  let rec format_of = function
    | [] -> None
    | Xml.Element ("driver", attrs, _) :: rest ->
        (try Some (List.assoc "type" attrs)
         with Not_found -> format_of rest)
    | _ :: rest -> format_of rest
  in

  (* Look for <disk> nodes and return the sources (block devices) of those. *)
  let blkdevs =
    List.filter_map (
      function
      | Xml.Element ("disk", attrs, disks) ->
          let filename =
            try
              let typ = List.assoc "type" attrs in
              if typ = "file" then source_of "file" disks
              else if typ = "block" then source_of "dev" disks
              else None
            with
              Not_found -> None in
          (match filename with
           | None -> None
           | Some filename ->
               let format = format_of disks in
               Some (filename, format)
          );
      | _ -> None
    ) devices in
  blkdevs

(* The common code for Open_domain and Open_images which opens the
 * libguestfs handle, adds the disks, and launches the appliance.
 *)
and open_disk_images images cb =
  debug "opening disk image %s" (string_of_images images);

  close_g ();
  let g' = new Guestfs.guestfs () in
  g := Some g';
  let g = g' in

  (* Uncomment the next line to pass the verbose flag from the command
   * line through to libguestfs.  This is not generally necessary since
   * we are not so interested in debugging libguestfs problems at this
   * level, and the user can always set LIBGUESTFS_DEBUG=1 if they need
   * to.
   *)
  (* g#set_verbose (verbose ());*)

  (* Attach progress bar callback. *)
  g#set_progress_callback (
    fun proc_nr serial position total ->
      debug "progress callback proc_nr=%d serial=%d posn=%Ld total=%Ld"
        proc_nr serial position total;
      GtkThread.async !progress_hook (position, total)
  );

  List.iter (
    function
    | filename, None ->
        g#add_drive_opts ~readonly:true filename
    | filename, Some format ->
        g#add_drive_opts ~readonly:true ~format filename
  ) images;

  g#launch ();

  (* Get list of filesystems. *)
  let fses = g#list_filesystems () in

  (* Perform inspection.  This can fail, ignore errors. *)
  let roots =
    try Array.to_list (g#inspect_os ())
    with
      Guestfs.Error msg ->
        debug "inspection failed (error ignored): %s" msg;
        [] in

  let oses = List.map (
    fun root -> {
      insp_root = root;
      insp_arch = g#inspect_get_arch root;
      insp_distro = g#inspect_get_distro root;
      insp_filesystems = g#inspect_get_filesystems root;
      insp_hostname = g#inspect_get_hostname root;
      insp_major_version = g#inspect_get_major_version root;
      insp_minor_version = g#inspect_get_minor_version root;
      insp_mountpoints = g#inspect_get_mountpoints root;
      insp_package_format = g#inspect_get_package_format root;
      insp_package_management = g#inspect_get_package_management root;
      insp_product_name = g#inspect_get_product_name root;
      insp_type = g#inspect_get_type root;
      insp_windows_systemroot =
        try Some (g#inspect_get_windows_systemroot root)
        with Guestfs.Error _ -> None
    }
  ) roots in
  let data = {
    insp_all_filesystems = fses;
    insp_oses = oses;
  } in
  callback_if_not_discarded cb data

(* guestfs_lstatlist has a "hidden" limit of the protocol message size.
 * Call this function, but split the list of names into chunks.
 *)
and lstatlist_wrapper g dir = function
  | [] -> []
  | names ->
      let names', names = List.take 1000 names, List.drop 1000 names in
      let xs = g#lstatlist dir (Array.of_list names') in
      let xs = Array.to_list xs in
      xs @ lstatlist_wrapper g dir names

(* Same as above for guestfs_readlinklist. *)
and readlinklist_wrapper g dir = function
  | [] -> []
  | names ->
      let names', names = List.take 1000 names, List.drop 1000 names in
      let xs = g#readlinklist dir (Array.of_list names') in
      let xs = Array.to_list xs in
      xs @ readlinklist_wrapper g dir names

(* Start up one slave thread. *)
let slave_thread = Thread.create loop ()

(* Note the following function is called from the main thread. *)
let exit_thread () =
  discard_command_queue ();
  ignore (send_to_slave Exit_thread);
  Thread.join slave_thread