(* 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

type t = {
  (* Variables. *)
  variables : variables;

  (* Loaded jobs. *)
  jobs : job list;

  (*--- below here is "internal" state ---*)

  jobmap : job StringMap.t;            (* job name -> job structure *)

  (* Map variable names to jobs which depend on that variable.  This
   * gives us a quick way to tell which jobs might need to be reevaluated
   * when a variable is set.
   *)
  dependencies : string list StringMap.t; (* variable -> list of job names *)

  (* For each job, if it has run, we store the previous variables
   * at that time.  This is used to implement {i previous}, {i changes} etc.
   *)
  prev_variables : variables StringMap.t; (* job name -> variables *)

  (* For each job, if it has been evaluated before (see {!job_evaluate})
   * then we store the previous result of evaluation here.  This is
   * used to implement edge-triggering.
   *)
  prev_eval_result : bool StringMap.t;   (* job name -> bool *)
}

let empty = {
  variables = StringMap.empty;
  jobs = [];
  jobmap = StringMap.empty;
  dependencies = StringMap.empty;
  prev_variables = StringMap.empty;
  prev_eval_result = StringMap.empty;
}

let add_job t job =
  let deps = dependencies_of_job job in
  let dependencies' = List.fold_left (
    fun map d ->
      let names = try StringMap.find d map with Not_found -> [] in
      StringMap.add d (job.job_name :: names) map
  ) t.dependencies deps in

  { t with
      jobs = job :: t.jobs;
      jobmap = StringMap.add job.job_name job t.jobmap;
      dependencies = dependencies'
  }

let set_variable t name value =
  { t with variables = StringMap.add name value t.variables }

let copy_variables old t =
  { t with variables = StringMap.fold StringMap.add old.variables t.variables }

let get_variable t name =
  try StringMap.find name t.variables with Not_found -> T_string ""

let get_variables t =
  StringMap.fold (
    fun name value xs ->
      if value <> T_string "" then (name, value) :: xs else xs
  ) t.variables []

let get_variable_names t =
  StringMap.fold (
    fun name value xs -> if value <> T_string "" then name :: xs else xs
  ) t.variables []

let nr_jobs t = List.length t.jobs

let get_dependencies t name =
  let jobnames = try StringMap.find name t.dependencies with Not_found -> [] in
  List.map (fun jn ->
    try
      let j = StringMap.find jn t.jobmap in
      (* If this asserts false, then there is a bug in {!add_job}. *)
      assert (match j.job_cond with When_job _ -> true | _ -> false);
      j
    with Not_found ->
      (* This should never happen.  It would indicate some bug in the
       * {!add_job} function.
       *)
      assert false
  ) jobnames

let get_whenjobs t =
  List.filter (function { job_cond = When_job _ } -> true | _ -> false) t.jobs

let get_everyjobs t =
  List.filter (function { job_cond = Every_job _ } -> true | _ -> false) t.jobs

let get_job t jobname =
  try StringMap.find jobname t.jobmap with Not_found -> assert false

let evaluate_whenjob ?(onload = false) t job =
  match job with
  | { job_cond = Every_job _ } -> assert false
  | { job_cond = When_job whenexpr; job_name = jobname } ->
    let prev_variables =
      try Some (StringMap.find jobname t.prev_variables)
      with Not_found -> None in

    let result =
      eval_whenexpr_as_bool t.variables prev_variables onload whenexpr in

    let prev_eval_result =
      try Some (StringMap.find jobname t.prev_eval_result)
      with Not_found -> None in

    let t = { t with prev_eval_result =
                       StringMap.add jobname result t.prev_eval_result } in

    (* Because jobs are edge-triggered, we're only interested in the
     * case where the evaluation state changes from false -> true.
     *)
    match prev_eval_result, result with
    | None, false
    | Some false, false
    | Some true, true
    | Some true, false ->
      false, t

    | None, true
    | Some false, true ->
      let t = { t with prev_variables =
                         StringMap.add jobname t.variables t.prev_variables } in
      true, t