(* whenjobs
 * Copyright (C) 2012 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 Whenutils
open Whenexpr

open Big_int
open Unix
open Printf

(* See [exit.c]. *)
external _exit : int -> 'a = "whenjobs__exit"

(* $HOME/.whenjobs *)
let jobsdir = ref ""

(* The state.
 *
 * Note that whenever this is updated, you need to consider if you
 * should call 'save_variables ()' (which persists the variables to a
 * file).  XXX We should replace this ref with an accessor
 * function.
 *)
let state = ref Whenstate.empty

(* Format used to save variables.  Note we can't allow any internal
 * types to "escape" into this definition, else the file format will
 * change when parts of the program change.
 *)
type variables_file_v1 = (string * variable_v1) list
and variable_v1 =
  | Vv1_unit
  | Vv1_bool of bool
  | Vv1_string of string
  | Vv1_int of big_int
  | Vv1_float of float

let variable_of_variable_v1 = function
  | Vv1_unit -> T_unit
  | Vv1_bool b -> T_bool b
  | Vv1_string s -> T_string s
  | Vv1_int i -> T_int i
  | Vv1_float f -> T_float f

let variable_v1_of_variable = function
  | T_unit -> Vv1_unit
  | T_bool b -> Vv1_bool b
  | T_string s -> Vv1_string s
  | T_int i -> Vv1_int i
  | T_float f -> Vv1_float f

(* Jobs that are running: a map of PID -> (job, tmpdir, serial, start_time).
 * Note that the job may no longer exist *OR* it may have been renamed,
 * eg. if the jobs file was reloaded.
 *)
let runningmap = ref IntMap.empty

(* Serial numbers of running jobs.  Map of serial -> PID (in runningmap). *)
let serialmap = ref BigIntMap.empty

(* Was debugging requested on the command line? *)
let debug = ref false

(* The server. *)
let server = ref None

let esys = Unixqueue.standard_event_system ()

(* The timer.  It's convenient to have this as a global variable
 * because (a) there should only be one timer (which fires when the
 * soonest every-job becomes ready), and (b) it's complicated to track
 * that timer and avoid it getting double-scheduled (eg.  when we
 * reload the jobs file) without having a global variable.
 *)
let timer_group = ref None

let rec init j d =
  jobsdir := j;
  debug := d;

  Whenlock.create_lock !jobsdir;

  (* Remove old socket if it exists. *)
  let addr = sprintf "%s/socket" !jobsdir in
  (try unlink addr with Unix_error _ -> ());

  (* Create the Unix domain socket server. *)
  server := Some (
    Whenproto_srv.When.V1.create_server
      ~proc_reload_file
      ~proc_set_variable
      ~proc_get_variable
      ~proc_get_variable_names
      ~proc_exit_daemon
      ~proc_get_jobs
      ~proc_cancel_job
      ~proc_start_job
      ~proc_get_job
      ~proc_set_variables
      ~proc_get_job_names
      ~proc_test_variables
      ~proc_ping_daemon
      ~proc_whisper_variables
      (Rpc_server.Unix addr)
      Rpc.Tcp (* not TCP, this is the same as SOCK_STREAM *)
      Rpc.Socket
      esys
  );

  (* Handle SIGCHLD to clean up jobs. *)
  Sys.set_signal Sys.sigchld (Sys.Signal_handle handle_sigchld);

  (* Load or initialize the variables. *)
  let variables_file = sprintf "%s/variables" !jobsdir in
  state :=
    try
      let chan = open_in variables_file in
      let r = load_variables !state chan in
      close_in chan;
      r
    with
    | Sys_error _ ->
      Whenstate.set_variable !state "JOBSERIAL" (T_int zero_big_int)

(* Try to load the variables from the file.  If the file exists and
 * cannot be read, raise an exception.
 *)
and load_variables state chan =
  let signature = input_line chan in
  if signature = "WHENJOBS VARIABLES VERSION 1" then (
    let variables : variables_file_v1 = input_value chan in
    List.fold_left (
      fun state (n, v) ->
        Whenstate.set_variable state n (variable_of_variable_v1 v)
    ) state variables
  ) else (* in future, other signatures, but for now ... *)
    failwith (sprintf "cannot read variables file: invalid signature: %s"
                signature)

and save_variables () =
  let variables_file = sprintf "%s/variables" !jobsdir in
  let new_file = variables_file ^ ".new" in
  let chan = open_out new_file in
  fprintf chan "WHENJOBS VARIABLES VERSION 1\n";
  let variables = Whenstate.get_variables !state in
  let variables =
    List.map (fun (n, v) -> n, variable_v1_of_variable v) variables in
  output_value chan variables;

  (* Try to arrange that the new file is updated atomically. *)
  flush chan;
  Netsys_posix.fsync (descr_of_out_channel chan);
  close_out chan;
  rename new_file variables_file

and proc_reload_file () =
  if !debug then Syslog.notice "remote call: reload_file";

  try reload_files (); `ok
  with Failure err -> `error err

and proc_set_variable (name, value) =
  if !debug then Syslog.notice "remote call: set_variable %s" name;

  try
    check_valid_variable_name name;

    let value = variable_of_rpc value in
    state := Whenstate.set_variable !state name value;

    (* Which jobs need to be re-evaluated? *)
    let jobs = Whenstate.get_dependencies !state [name] in
    let jobnames, state' = reevaluate_whenjobs !state jobs in
    let state' = run_whenjobs state' jobnames in
    state := state';
    save_variables ();

    `ok
  with
    Failure msg -> `error msg

and proc_get_variable name =
  if !debug then Syslog.notice "remote call: get_variable %s" name;

  rpc_of_variable (Whenstate.get_variable !state name)

and proc_get_variable_names () =
  if !debug then Syslog.notice "remote call: get_variable_names";

  let vars = Whenstate.get_variable_names !state in

  (* Return variable names as a sorted array. *)
  let vars = Array.of_list vars in
  Array.sort compare vars;
  vars

and proc_exit_daemon () =
  if !debug then Syslog.notice "remote call: exit_daemon";

  match !server with
  | None ->
    `error "exit_daemon: no server handle"
  | Some s ->
    Rpc_server.stop_server ~graceful:true s;
    server := None;
    Gc.compact (); (* force the server handle to get cleaned up now *)
    `ok

and proc_get_jobs () =
  let running = Array.of_list (IntMap.values !runningmap) in
  Array.map (
    fun (job, dir, serial, start_time) ->
      { Whenproto_aux.job_name = job.job_name;
        job_serial = string_of_big_int serial;
        job_tmpdir = dir; job_start_time = Int64.of_float start_time }
  ) running

and proc_cancel_job serial =
  try
    let serial = big_int_of_string serial in
    let pid = BigIntMap.find serial !serialmap in
    kill pid 15;
    `ok
  with
  | Not_found -> `error "job not found"
  | exn -> `error (Printexc.to_string exn)

and proc_start_job jobname =
  try
    let job = Whenstate.get_job !state jobname in
    let state' = run_job !state job in
    state := state';
    save_variables ();
    `ok
  with
  | Not_found -> `error "job not found"
  | exn -> `error (Printexc.to_string exn)

and proc_get_job serial =
  try
    let serial = big_int_of_string serial in
    let pid = BigIntMap.find serial !serialmap in
    let job, dir, serial, start_time = IntMap.find pid !runningmap in
    { Whenproto_aux.job_name = job.job_name;
      job_serial = string_of_big_int serial;
      job_tmpdir = dir; job_start_time = Int64.of_float start_time }
  with
  | Not_found -> failwith "job not found"
  | exn -> failwith (Printexc.to_string exn)

and proc_set_variables vars =
  try
    let vars = Array.map (
      fun { Whenproto_aux.sv_name = name; sv_value = value } ->
        name, variable_of_rpc value
    ) vars in
    let vars = Array.to_list vars in

    if !debug then
      Syslog.notice "remote call: set_variables (%s)"
        (String.concat " "
           (List.map (
             fun (name, value) ->
               sprintf "%s=%s" name (string_of_variable value)
            ) vars));

    List.iter (fun (name, _) -> check_valid_variable_name name) vars;

    (* Update all the variables atomically. *)
    let s = List.fold_left (
      fun s (name, value) -> Whenstate.set_variable s name value
    ) !state vars in
    state := s;

    (* Which jobs need to be re-evaluated? *)
    let jobs = Whenstate.get_dependencies !state (List.map fst vars) in
    let jobnames, state' = reevaluate_whenjobs !state jobs in
    let state' = run_whenjobs state' jobnames in
    state := state';
    save_variables ();

    `ok
  with
    Failure msg -> `error msg

and proc_get_job_names () =
  Array.of_list (Whenstate.get_job_names !state)

and proc_test_variables vars =
  (* This is the same as proc_set_variables, except that it doesn't
   * update the state, it just returns the jobs that *would* run if
   * these variables were set to these values.
   *)
  let vars = Array.map (
    fun { Whenproto_aux.sv_name = name; sv_value = value } ->
      name, variable_of_rpc value
  ) vars in
  let vars = Array.to_list vars in

  if !debug then
    Syslog.notice "remote call: test_variables (%s)"
      (String.concat " "
         (List.map (
           fun (name, value) ->
             sprintf "%s=%s" name (string_of_variable value)
          ) vars));

  List.iter (fun (name, _) -> check_valid_variable_name name) vars;

  (* Update all the variables atomically. *)
  let state = List.fold_left (
    fun s (name, value) -> Whenstate.set_variable s name value
  ) !state vars in

  (* Which jobs WOULD be re-evaluated? *)
  let jobs = Whenstate.get_dependencies state (List.map fst vars) in
  let jobnames, _ = reevaluate_whenjobs state jobs in

  (* Return the names. *)
  Array.of_list jobnames

and proc_ping_daemon () = `ok

and proc_whisper_variables vars =
  try
    let vars = Array.map (
      fun { Whenproto_aux.sv_name = name; sv_value = value } ->
        name, variable_of_rpc value
    ) vars in
    let vars = Array.to_list vars in

    if !debug then
      Syslog.notice "remote call: whisper_variables (%s)"
        (String.concat " "
           (List.map (
             fun (name, value) ->
               sprintf "%s=%s" name (string_of_variable value)
            ) vars));

    List.iter (fun (name, _) -> check_valid_variable_name name) vars;

    (* Update all the variables atomically. *)
    let s = List.fold_left (
      fun s (name, value) -> Whenstate.set_variable s name value
    ) !state vars in
    state := s;
    save_variables ();

    (* .. but don't reevaluate or run jobs. *)

    `ok
  with
    Failure msg -> `error msg

(* Reload the jobs file(s). *)
and reload_files () =
  (* Get the highest numbered dir/jobs__*.cmo (bytecode) or
   * dir/jobs__*.cmxs (native code) file and load it.  Delete
   * lower-numbered (== older) files.
   *)
  let filename =
    let suffix, slen =
      if not Dynlink.is_native then ".cmo", 4 else ".cmxs", 5 in
    let dir = !jobsdir in
    let files = Array.to_list (Sys.readdir dir) in
    let times = filter_map (
      fun file ->
        if not (string_startswith file "jobs__") ||
          not (string_endswith file suffix) then
          None
        else (
          let len = String.length file in
          let t = String.sub file 6 (len-slen-6) in
          (* Use int64 because t won't necessarily fit into 31 bit int. *)
          try Some (Int64.of_string t)
          with Failure "int_of_string" -> assert false
        )
    ) files in
    let times = List.rev (List.sort compare times) in
    match times with
    | [] -> None
    | x::xs ->
      (* Unlink the older files. *)
      List.iter (
        fun t ->
          try unlink (dir // sprintf "jobs__%Ld%s" t suffix)
          with Unix_error _ -> ()
      ) xs;
      (* Return the newest (highest numbered) file. *)
      Some (dir // sprintf "jobs__%Ld%s" x suffix) in

  (* As we are reloading the file, we want to create a new state
   * that has no jobs, but has all the variables from the previous
   * state.
   *)
  let s = Whenstate.copy_variables !state Whenstate.empty in
  Whenfile.init s;

  let s =
    match filename with
    | None ->
      (* no jobs file, return the same state *)
      Syslog.notice "no jobs file found";
      s
    | Some filename ->
      try
        Dynlink.loadfile filename;
        let s = Whenfile.get_state () in
        Syslog.notice "loaded %d job(s)" (Whenstate.nr_jobs s);
        s
      with
      | Dynlink.Error err ->
        let err = Dynlink.error_message err in
        Syslog.error "error loading jobs: %s" err;
        failwith err
      | exn ->
        failwith (Printexc.to_string exn) in

  let s = Whenstate.copy_prev_state !state s in
  state := s;

  (* Re-evaluate all when jobs. *)
  let jobs = Whenstate.get_whenjobs !state in
  let jobnames, state' = reevaluate_whenjobs ~onload:true !state jobs in
  let state' = run_whenjobs state' jobnames in
  state := state';
  save_variables ();

  (* Schedule the next every job to run. *)
  schedule_next_everyjob ()

(* Re-evaluate each when-statement job, in a loop until we reach
 * a fixpoint.  Return the list of job names that should run and
 * the updated state.
 *)
and reevaluate_whenjobs ?onload state jobs =
  let rec loop (set, state) jobs =
    let set', state' =
      List.fold_left (
        fun (set, state) job ->
          let r, state' =
            try Whenstate.evaluate_whenjob ?onload state job
            with Invalid_argument err | Failure err ->
              Syslog.error "error evaluating job %s (at %s): %s"
                job.job_name (Camlp4.PreCast.Ast.Loc.to_string job.job_loc) err;
              false, state in

          if !debug then
            Syslog.notice "evaluate %s -> %b\n" job.job_name r;

          (if r then StringSet.add job.job_name set else set), state'
      ) (set, state) jobs in
    (* reached a fixpoint? *)
    if StringSet.compare set set' <> 0 then
      loop (set', state') jobs
    else
      (set', state')
  in
  let set, state = loop (StringSet.empty, state) jobs in
  let jobnames = StringSet.elements set in

  (* Ensure the jobs always run in predictable (name) order. *)
  let jobnames = List.sort compare_jobnames jobnames in
  jobnames, state

and run_whenjobs state jobnames =
  (* Run the jobs. *)
  let jobs = List.map (Whenstate.get_job state) jobnames in
  List.fold_left run_job state jobs

(* Schedule the next every-statement job to run, if there is one.  We
 * look at the every jobs, work out the time that each must run at,
 * pick the job(s) which must run soonest, and schedule a timer to run
 * them.  When the timer fires, it runs those jobs, then calls this
 * function again.
 *)
and schedule_next_everyjob () =
  let t = time () in

  (* Get only everyjobs. *)
  let jobs = Whenstate.get_everyjobs !state in
  let jobs = List.map (
    function
    | { job_cond = Every_job period } as job -> (job, period)
    | { job_cond = When_job _ } -> assert false
  ) jobs in

  (* Map everyjob to next time it must run. *)
  let jobs = List.map (
    fun (job, period) ->
      let t' = next_periodexpr t period in
      assert (t' > t); (* serious bug in next_periodexpr if false *)
      job, t'
  ) jobs in

  (* Sort, soonest first. *)
  let jobs = List.sort (fun (_,a) (_,b) -> compare a b) jobs in

  if !debug then (
    List.iter (
      fun (job, t) ->
        Syslog.notice "%s: next scheduled run at %s"
          job.job_name (string_of_time_t t)
    ) jobs
  );

  (* Pick the job(s) which run soonest. *)
  let rec pick = function
    | [] -> 0., []
    | [j, t] -> t, [j]
    | (j1, t) :: (j2, t') :: _ when t < t' -> t, [j1]
    | (j1, t) :: (((j2, t') :: _) as rest) -> t, (j1 :: snd (pick rest))
  in
  let t, jobs = pick jobs in

  if t > 0. then (
    if jobs <> [] then (
      (* Ensure the jobs always run in predictable (name) order. *)
      let jobs =
        List.sort (fun {job_name = a} {job_name = b} -> compare_jobnames a b)
          jobs in

      if !debug then
        Syslog.notice "scheduling job(s) %s to run at %s"
          (String.concat ", " (List.map (fun { job_name = name } -> name) jobs))
          (string_of_time_t t);

      (* Schedule them to run at time t. *)
      let g = new_timer_group () in
      let t_diff = t -. Unix.time () in
      let t_diff = if t_diff < 0. then 0. else t_diff in
      let run_jobs () =
        delete_timer_group ();          (* Delete the timer. *)
        let state' = List.fold_left run_job !state jobs in
        state := state';
        save_variables ();
        schedule_next_everyjob ()
      in
      Unixqueue.weak_once esys g t_diff run_jobs;
    )
  )

and new_timer_group () =
  delete_timer_group ();
  let g = Unixqueue.new_group esys in
  timer_group := Some g;
  g

and delete_timer_group () =
  match !timer_group with
  | None -> ()
  | Some g ->
    Unixqueue.clear esys g;
    timer_group := None

and run_job state job =
  (* Increment JOBSERIAL. *)
  let serial, state =
    match Whenstate.get_variable state "JOBSERIAL" with
    | T_int serial ->
      let serial = succ_big_int serial in
      let state' = Whenstate.set_variable state "JOBSERIAL" (T_int serial) in
      serial, state'
    | _ -> assert false in

  (* Call the pre-condition script.  Note this may decide not to run
   * the job by returning false.
   *)
  let pre_condition () =
    match job.job_pre with
    | None -> true
    | Some pre ->
      let rs = ref [] in
      IntMap.iter (
        fun pid (job, _, serial, start_time) ->
          let r = { pirun_job_name = job.job_name;
                    pirun_serial = serial;
                    pirun_start_time = start_time;
                    pirun_pid = pid } in
          rs := r :: !rs
      ) !runningmap;
      let preinfo = {
        pi_job_name = job.job_name;
        pi_serial = serial;
        pi_variables = Whenstate.get_variables state;
        pi_running = !rs;
      } in
      pre preinfo
  in
  if pre_condition () then (
    Syslog.notice "running %s (JOBSERIAL=%s)"
      job.job_name (string_of_big_int serial);

    (* Create a temporary directory.  The current directory of the job
     * will be in this directory.  The directory is removed when the
     * child process exits.
     *)
    let dir = tmpdir () in

    let pid = fork () in
    if pid = 0 then ( (* child process running the job *)
      chdir dir;

      (* Set environment variables corresponding to each variable. *)
      List.iter
        (fun (name, value) -> putenv name (string_of_variable value))
        (Whenstate.get_variables state);

      (* Set the $JOBNAME environment variable. *)
      putenv "JOBNAME" job.job_name;

      (* Create a temporary file containing the shell script fragment. *)
      let script = dir // "script.sh" in
      let chan = open_out script in
      fprintf chan "set -e\n"; (* So that jobs exit on error. *)
      output_string chan job.job_script.sh_script;
      close_out chan;
      chmod script 0o700;

      let shell = try getenv "SHELL" with Not_found -> "/bin/sh" in

      (* Set output to file. *)
      let output = dir // "output.txt" in
      let fd = openfile output [O_WRONLY; O_CREAT; O_TRUNC; O_NOCTTY] 0o600 in
      dup2 fd stdout;
      dup2 fd stderr;
      close fd;

      (* Execute the shell script. *)
      (try execvp shell [| shell; "-c"; script |];
       with Unix_error (err, fn, _) ->
         Syslog.error "%s failed: %s: %s" fn script (error_message err)
      );
      _exit 1
    );

    (* Remember this PID, the job and the temporary directory, so we
     * can clean up when the child exits.
     *)
    runningmap := IntMap.add pid (job, dir, serial, time ()) !runningmap;
    serialmap := BigIntMap.add serial pid !serialmap;

    state
  )
  else (
    Syslog.notice "not running %s (JOBSERIAL=%s) because pre() condition returned false"
      job.job_name (string_of_big_int serial);

    state
  )

and tmpdir () =
  let chan = open_in "/dev/urandom" in
  let data = String.create 16 in
  really_input chan data 0 (String.length data);
  close_in chan;
  let data = Digest.to_hex (Digest.string data) in
  let dir = Filename.temp_dir_name // sprintf "whenjobs%s" data in
  mkdir dir 0o700;
  dir

(* This is called when a job (child process) exits. *)
and handle_sigchld _ =
  try
    let pid, status = waitpid [WNOHANG] 0 in
    if pid > 0 then (
      (* Look up the PID in the running jobs map. *)
      let job, dir, serial, time = IntMap.find pid !runningmap in
      runningmap := IntMap.remove pid !runningmap;
      serialmap := BigIntMap.remove serial !serialmap;
      post_job job dir serial time status
    )
  with Unix_error _ | Not_found -> ()

and post_job job dir serial time status =
  (* If there is a post function, run it. *)
  (match job.job_post with
  | None -> ()
  | Some post ->
    let code =
      match status with
      | WEXITED c -> c
      | WSIGNALED s | WSTOPPED s -> 1 in
    let result = {
      res_job_name = job.job_name;
      res_serial = serial;
      res_code = code;
      res_tmpdir = dir;
      res_output = dir // "output.txt";
      res_start_time = time
    } in
    try post result
    with
    | Failure msg ->
      Syslog.error "job %s post function failed: %s" job.job_name msg
    | exn ->
      Syslog.error "job %s post function exception: %s"
        job.job_name (Printexc.to_string exn)
  );

  (* This should be safe because the path cannot contain shell metachars. *)
  let cmd = sprintf "rm -rf '%s'" dir in
  ignore (Sys.command cmd)

(* Intelligent comparison of job names. *)
and compare_jobnames name1 name2 =
  try
    let len1 = String.length name1
    and len2 = String.length name2 in
    if len1 > 4 && len2 > 4 &&
      String.sub name1 0 4 = "job$" && String.sub name2 0 4 = "job$"
    then (
      let i1 = int_of_string (String.sub name1 4 (len1-4)) in
      let i2 = int_of_string (String.sub name2 4 (len2-4)) in
      compare i1 i2
    )
    else raise Not_found
  with _ ->
    compare name1 name2

let main_loop () =
  Unixqueue.run esys