Aff.js

/* globals setImmediate, clearImmediate, setTimeout, clearTimeout */
/* jshint -W083, -W098, -W003 */
"use strict";

var Aff = function () {
  // A unique value for empty.
  var EMPTY = {};

  /*

  An awkward approximation. We elide evidence we would otherwise need in PS for
  efficiency sake.

  data Aff eff a
    = Pure a
    | Throw Error
    | Catch (Aff eff a) (Error -> Aff eff a)
    | Sync (Eff eff a)
    | Async ((Either Error a -> Eff eff Unit) -> Eff eff (Canceler eff))
    | forall b. Bind (Aff eff b) (b -> Aff eff a)
    | forall b. Bracket (Aff eff b) (BracketConditions eff b) (b -> Aff eff a)
    | forall b. Fork Boolean (Aff eff b) ?(Fiber eff b -> a)
    | Sequential (ParAff aff a)

  */
  var PURE    = "Pure";
  var THROW   = "Throw";
  var CATCH   = "Catch";
  var SYNC    = "Sync";
  var ASYNC   = "Async";
  var BIND    = "Bind";
  var BRACKET = "Bracket";
  var FORK    = "Fork";
  var SEQ     = "Sequential";

  /*

  data ParAff eff a
    = forall b. Map (b -> a) (ParAff eff b)
    | forall b. Apply (ParAff eff (b -> a)) (ParAff eff b)
    | Alt (ParAff eff a) (ParAff eff a)
    | ?Par (Aff eff a)

  */
  var MAP   = "Map";
  var APPLY = "Apply";
  var ALT   = "Alt";

  // Various constructors used in interpretation
  var CONS      = "Cons";      // Cons-list, for stacks
  var RESUME    = "Resume";    // Continue indiscriminately
  var RELEASE   = "Release";   // Continue with bracket finalizers
  var FINALIZER = "Finalizer"; // A non-interruptible effect
  var FINALIZED = "Finalized"; // Marker for finalization
  var FORKED    = "Forked";    // Reference to a forked fiber, with resumption stack
  var FIBER     = "Fiber";     // Actual fiber reference
  var THUNK     = "Thunk";     // Primed effect, ready to invoke

  function Aff(tag, _1, _2, _3) {
    this.tag = tag;
    this._1  = _1;
    this._2  = _2;
    this._3  = _3;
  }

  function AffCtr(tag) {
    var fn = function (_1, _2, _3) {
      return new Aff(tag, _1, _2, _3);
    };
    fn.tag = tag;
    return fn;
  }

  function nonCanceler(error) {
    return new Aff(PURE, void 0);
  }

  function runEff(eff) {
    try {
      eff();
    } catch (error) {
      setTimeout(function () {
        throw error;
      }, 0);
    }
  }

  function runSync(left, right, eff) {
    try {
      return right(eff());
    } catch (error) {
      return left(error);
    }
  }

  function runAsync(left, eff, k) {
    try {
      return eff(k)();
    } catch (error) {
      k(left(error))();
      return nonCanceler;
    }
  }

  var Scheduler = function () {
    var limit    = 1024;
    var size     = 0;
    var ix       = 0;
    var queue    = new Array(limit);
    var draining = false;

    function drain() {
      var thunk;
      draining = true;
      while (size !== 0) {
        size--;
        thunk     = queue[ix];
        queue[ix] = void 0;
        ix        = (ix + 1) % limit;
        thunk();
      }
      draining = false;
    }

    return {
      isDraining: function () {
        return draining;
      },
      enqueue: function (cb) {
        var i, tmp;
        if (size === limit) {
          tmp = draining;
          drain();
          draining = tmp;
        }

        queue[(ix + size) % limit] = cb;
        size++;

        if (!draining) {
          drain();
        }
      }
    };
  }();

  function Supervisor(util) {
    var fibers  = {};
    var fiberId = 0;
    var count   = 0;

    return {
      register: function (fiber) {
        var fid = fiberId++;
        fiber.onComplete({
          rethrow: true,
          handler: function (result) {
            return function () {
              count--;
              delete fibers[fid];
            };
          }
        });
        fibers[fid] = fiber;
        count++;
      },
      isEmpty: function () {
        return count === 0;
      },
      killAll: function (killError, cb) {
        return function () {
          var killCount = 0;
          var kills     = {};

          function kill(fid) {
            kills[fid] = fibers[fid].kill(killError, function (result) {
              return function () {
                delete kills[fid];
                killCount--;
                if (util.isLeft(result) && util.fromLeft(result)) {
                  setTimeout(function () {
                    throw util.fromLeft(result);
                  }, 0);
                }
                if (killCount === 0) {
                  cb();
                }
              };
            })();
          }

          for (var k in fibers) {
            if (fibers.hasOwnProperty(k)) {
              killCount++;
              kill(k);
            }
          }

          fibers  = {};
          fiberId = 0;
          count   = 0;

          return function (error) {
            return new Aff(SYNC, function () {
              for (var k in kills) {
                if (kills.hasOwnProperty(k)) {
                  kills[k]();
                }
              }
            });
          };
        };
      }
    };
  }

  // Fiber state machine
  var SUSPENDED   = 0; // Suspended, pending a join.
  var CONTINUE    = 1; // Interpret the next instruction.
  var STEP_BIND   = 2; // Apply the next bind.
  var STEP_RESULT = 3; // Handle potential failure from a result.
  var PENDING     = 4; // An async effect is running.
  var RETURN      = 5; // The current stack has returned.
  var COMPLETED   = 6; // The entire fiber has completed.

  function Fiber(util, supervisor, aff) {
    // Monotonically increasing tick, increased on each asynchronous turn.
    var runTick = 0;

    // The current branch of the state machine.
    var status = SUSPENDED;

    // The current point of interest for the state machine branch.
    var step      = aff;  // Successful step
    var fail      = null; // Failure step
    var interrupt = null; // Asynchronous interrupt

    // Stack of continuations for the current fiber.
    var bhead = null;
    var btail = null;

    // Stack of attempts and finalizers for error recovery. Every `Cons` is also
    // tagged with current `interrupt` state. We use this to track which items
    // should be ignored or evaluated as a result of a kill.
    var attempts = null;

    // A special state is needed for Bracket, because it cannot be killed. When
    // we enter a bracket acquisition or finalizer, we increment the counter,
    // and then decrement once complete.
    var bracketCount = 0;

    // Each join gets a new id so they can be revoked.
    var joinId  = 0;
    var joins   = null;
    var rethrow = true;

    // Each invocation of `run` requires a tick. When an asynchronous effect is
    // resolved, we must check that the local tick coincides with the fiber
    // tick before resuming. This prevents multiple async continuations from
    // accidentally resuming the same fiber. A common example may be invoking
    // the provided callback in `makeAff` more than once, but it may also be an
    // async effect resuming after the fiber was already cancelled.
    function run(localRunTick) {
      var tmp, result, attempt, canceler;
      while (true) {
        tmp       = null;
        result    = null;
        attempt   = null;
        canceler  = null;

        switch (status) {
        case STEP_BIND:
          status = CONTINUE;
          step   = bhead(step);
          if (btail === null) {
            bhead = null;
          } else {
            bhead = btail._1;
            btail = btail._2;
          }
          break;

        case STEP_RESULT:
          if (util.isLeft(step)) {
            status = RETURN;
            fail   = step;
            step   = null;
          } else if (bhead === null) {
            status = RETURN;
          } else {
            status = STEP_BIND;
            step   = util.fromRight(step);
          }
          break;

        case CONTINUE:
          switch (step.tag) {
          case BIND:
            if (bhead) {
              btail = new Aff(CONS, bhead, btail);
            }
            bhead  = step._2;
            status = CONTINUE;
            step   = step._1;
            break;

          case PURE:
            if (bhead === null) {
              status = RETURN;
              step   = util.right(step._1);
            } else {
              status = STEP_BIND;
              step   = step._1;
            }
            break;

          case SYNC:
            status = STEP_RESULT;
            step   = runSync(util.left, util.right, step._1);
            break;

          case ASYNC:
            status = PENDING;
            step   = runAsync(util.left, step._1, function (result) {
              return function () {
                if (runTick !== localRunTick) {
                  return;
                }
                runTick++;
                Scheduler.enqueue(function () {
                  status = STEP_RESULT;
                  step   = result;
                  run(runTick);
                });
              };
            });
            return;

          case THROW:
            status = RETURN;
            fail   = util.left(step._1);
            step   = null;
            break;

          // Enqueue the Catch so that we can call the error handler later on
          // in case of an exception.
          case CATCH:
            if (bhead === null) {
              attempts = new Aff(CONS, step, attempts, interrupt);
            } else {
              attempts = new Aff(CONS, step, new Aff(CONS, new Aff(RESUME, bhead, btail), attempts, interrupt), interrupt);
            }
            bhead    = null;
            btail    = null;
            status   = CONTINUE;
            step     = step._1;
            break;

          // Enqueue the Bracket so that we can call the appropriate handlers
          // after resource acquisition.
          case BRACKET:
            bracketCount++;
            if (bhead === null) {
              attempts = new Aff(CONS, step, attempts, interrupt);
            } else {
              attempts = new Aff(CONS, step, new Aff(CONS, new Aff(RESUME, bhead, btail), attempts, interrupt), interrupt);
            }
            bhead  = null;
            btail  = null;
            status = CONTINUE;
            step   = step._1;
            break;

          case FORK:
            status = STEP_RESULT;
            tmp    = Fiber(util, supervisor, step._2);
            if (supervisor) {
              supervisor.register(tmp);
            }
            if (step._1) {
              tmp.run();
            }
            step = util.right(tmp);
            break;

          case SEQ:
            status = CONTINUE;
            step   = sequential(util, supervisor, step._1);
            break;
          }
          break;

        case RETURN:
          bhead = null;
          btail = null;
          // If the current stack has returned, and we have no other stacks to
          // resume or finalizers to run, the fiber has halted and we can
          // invoke all join callbacks. Otherwise we need to resume.
          if (attempts === null) {
            status = COMPLETED;
            step   = interrupt || fail || step;
          } else {
            // The interrupt status for the enqueued item.
            tmp      = attempts._3;
            attempt  = attempts._1;
            attempts = attempts._2;

            switch (attempt.tag) {
            // We cannot recover from an interrupt. Otherwise we should
            // continue stepping, or run the exception handler if an exception
            // was raised.
            case CATCH:
              // We should compare the interrupt status as well because we
              // only want it to apply if there has been an interrupt since
              // enqueuing the catch.
              if (interrupt && interrupt !== tmp) {
                status = RETURN;
              } else if (fail) {
                status = CONTINUE;
                step   = attempt._2(util.fromLeft(fail));
                fail   = null;
              }
              break;

            // We cannot resume from an interrupt or exception.
            case RESUME:
              // As with Catch, we only want to ignore in the case of an
              // interrupt since enqueing the item.
              if (interrupt && interrupt !== tmp || fail) {
                status = RETURN;
              } else {
                bhead  = attempt._1;
                btail  = attempt._2;
                status = STEP_BIND;
                step   = util.fromRight(step);
              }
              break;

            // If we have a bracket, we should enqueue the handlers,
            // and continue with the success branch only if the fiber has
            // not been interrupted. If the bracket acquisition failed, we
            // should not run either.
            case BRACKET:
              bracketCount--;
              if (fail === null) {
                result   = util.fromRight(step);
                // We need to enqueue the Release with the same interrupt
                // status as the Bracket that is initiating it.
                attempts = new Aff(CONS, new Aff(RELEASE, attempt._2, result), attempts, tmp);
                // We should only coninue as long as the interrupt status has not changed or
                // we are currently within a non-interruptable finalizer.
                if (interrupt === tmp || bracketCount > 0) {
                  status = CONTINUE;
                  step   = attempt._3(result);
                }
              }
              break;

            // Enqueue the appropriate handler. We increase the bracket count
            // because it should not be cancelled.
            case RELEASE:
              bracketCount++;
              attempts = new Aff(CONS, new Aff(FINALIZED, step), attempts, interrupt);
              status   = CONTINUE;
              // It has only been killed if the interrupt status has changed
              // since we enqueued the item.
              if (interrupt && interrupt !== tmp) {
                step = attempt._1.killed(util.fromLeft(interrupt))(attempt._2);
              } else if (fail) {
                step = attempt._1.failed(util.fromLeft(fail))(attempt._2);
              } else {
                step = attempt._1.completed(util.fromRight(step))(attempt._2);
              }
              break;

            case FINALIZER:
              bracketCount++;
              attempts = new Aff(CONS, new Aff(FINALIZED, step), attempts, interrupt);
              status   = CONTINUE;
              step     = attempt._1;
              break;

            case FINALIZED:
              bracketCount--;
              status = RETURN;
              step   = attempt._1;
              break;
            }
          }
          break;

        case COMPLETED:
          for (var k in joins) {
            if (joins.hasOwnProperty(k)) {
              rethrow = rethrow && joins[k].rethrow;
              runEff(joins[k].handler(step));
            }
          }
          joins = null;
          // If we have an interrupt and a fail, then the thread threw while
          // running finalizers. This should always rethrow in a fresh stack.
          if (interrupt && fail) {
            setTimeout(function () {
              throw util.fromLeft(fail);
            }, 0);
          // If we have an unhandled exception, and no other fiber has joined
          // then we need to throw the exception in a fresh stack.
          } else if (util.isLeft(step) && rethrow) {
            setTimeout(function () {
              // Guard on reathrow because a completely synchronous fiber can
              // still have an observer which was added after-the-fact.
              if (rethrow) {
                throw util.fromLeft(step);
              }
            }, 0);
          }
          return;
        case SUSPENDED:
          status = CONTINUE;
          break;
        case PENDING: return;
        }
      }
    }

    function onComplete(join) {
      return function () {
        if (status === COMPLETED) {
          rethrow = rethrow && join.rethrow;
          join.handler(step)();
          return function () {};
        }

        var jid    = joinId++;
        joins      = joins || {};
        joins[jid] = join;

        return function() {
          if (joins !== null) {
            delete joins[jid];
          }
        };
      };
    }

    function kill(error, cb) {
      return function () {
        if (status === COMPLETED) {
          cb(util.right(void 0))();
          return function () {};
        }

        var canceler = onComplete({
          rethrow: false,
          handler: function (/* unused */) {
            return cb(util.right(void 0));
          }
        })();

        switch (status) {
        case SUSPENDED:
          interrupt = util.left(error);
          status    = COMPLETED;
          step      = interrupt;
          run(runTick);
          break;
        case PENDING:
          if (interrupt === null) {
            interrupt = util.left(error);
          }
          if (bracketCount === 0) {
            if (status === PENDING) {
              attempts = new Aff(CONS, new Aff(FINALIZER, step(error)), attempts, interrupt);
            }
            status   = RETURN;
            step     = null;
            fail     = null;
            run(++runTick);
          }
          break;
        default:
          if (interrupt === null) {
            interrupt = util.left(error);
          }
          if (bracketCount === 0) {
            status = RETURN;
            step   = null;
            fail   = null;
          }
        }

        return canceler;
      };
    }

    function join(cb) {
      return function () {
        var canceler = onComplete({
          rethrow: false,
          handler: cb
        })();
        if (status === SUSPENDED) {
          run(runTick);
        }
        return canceler;
      };
    }

    return {
      kill: kill,
      join: join,
      onComplete: onComplete,
      isSuspended: function () {
        return status === SUSPENDED;
      },
      run: function () {
        if (status === SUSPENDED) {
          if (!Scheduler.isDraining()) {
            Scheduler.enqueue(function () {
              run(runTick);
            });
          } else {
            run(runTick);
          }
        }
      }
    };
  }

  function runPar(util, supervisor, par, cb) {
    // Table of all forked fibers.
    var fiberId   = 0;
    var fibers    = {};

    // Table of currently running cancelers, as a product of `Alt` behavior.
    var killId    = 0;
    var kills     = {};

    // Error used for early cancelation on Alt branches.
    var early     = new Error("[ParAff] Early exit");

    // Error used to kill the entire tree.
    var interrupt = null;

    // The root pointer of the tree.
    var root      = EMPTY;

    // Walks a tree, invoking all the cancelers. Returns the table of pending
    // cancellation fibers.
    function kill(error, par, cb) {
      var step  = par;
      var head  = null;
      var tail  = null;
      var count = 0;
      var kills = {};
      var tmp, kid;

      loop: while (true) {
        tmp = null;

        switch (step.tag) {
        case FORKED:
          if (step._3 === EMPTY) {
            tmp = fibers[step._1];
            kills[count++] = tmp.kill(error, function (result) {
              return function () {
                count--;
                if (count === 0) {
                  cb(result)();
                }
              };
            });
          }
          // Terminal case.
          if (head === null) {
            break loop;
          }
          // Go down the right side of the tree.
          step = head._2;
          if (tail === null) {
            head = null;
          } else {
            head = tail._1;
            tail = tail._2;
          }
          break;
        case MAP:
          step = step._2;
          break;
        case APPLY:
        case ALT:
          if (head) {
            tail = new Aff(CONS, head, tail);
          }
          head = step;
          step = step._1;
          break;
        }
      }

      if (count === 0) {
        cb(util.right(void 0))();
      } else {
        // Run the cancelation effects. We alias `count` because it's mutable.
        kid = 0;
        tmp = count;
        for (; kid < tmp; kid++) {
          kills[kid] = kills[kid]();
        }
      }

      return kills;
    }

    // When a fiber resolves, we need to bubble back up the tree with the
    // result, computing the applicative nodes.
    function join(result, head, tail) {
      var fail, step, lhs, rhs, tmp, kid;

      if (util.isLeft(result)) {
        fail = result;
        step = null;
      } else {
        step = result;
        fail = null;
      }

      loop: while (true) {
        lhs = null;
        rhs = null;
        tmp = null;
        kid = null;

        // We should never continue if the entire tree has been interrupted.
        if (interrupt !== null) {
          return;
        }

        // We've made it all the way to the root of the tree, which means
        // the tree has fully evaluated.
        if (head === null) {
          cb(fail || step)();
          return;
        }

        // The tree has already been computed, so we shouldn't try to do it
        // again. This should never happen.
        // TODO: Remove this?
        if (head._3 !== EMPTY) {
          return;
        }

        switch (head.tag) {
        case MAP:
          if (fail === null) {
            head._3 = util.right(head._1(util.fromRight(step)));
            step    = head._3;
          } else {
            head._3 = fail;
          }
          break;
        case APPLY:
          lhs = head._1._3;
          rhs = head._2._3;
          // If we have a failure we should kill the other side because we
          // can't possible yield a result anymore.
          if (fail) {
            head._3 = fail;
            tmp     = true;
            kid     = killId++;

            kills[kid] = kill(early, fail === lhs ? head._2 : head._1, function (/* unused */) {
              return function () {
                delete kills[kid];
                if (tmp) {
                  tmp = false;
                } else if (tail === null) {
                  join(step, null, null);
                } else {
                  join(step, tail._1, tail._2);
                }
              };
            });

            if (tmp) {
              tmp = false;
              return;
            }
          } else if (lhs === EMPTY || rhs === EMPTY) {
            // We can only proceed if both sides have resolved.
            return;
          } else {
            step    = util.right(util.fromRight(lhs)(util.fromRight(rhs)));
            head._3 = step;
          }
          break;
        case ALT:
          lhs = head._1._3;
          rhs = head._2._3;
          // We can only proceed if both have resolved or we have a success
          if (lhs === EMPTY && util.isLeft(rhs) || rhs === EMPTY && util.isLeft(lhs)) {
            return;
          }
          // If both sides resolve with an error, we should continue with the
          // first error
          if (lhs !== EMPTY && util.isLeft(lhs) && rhs !== EMPTY && util.isLeft(rhs)) {
            fail    = step === lhs ? rhs : lhs;
            step    = null;
            head._3 = fail;
          } else {
            head._3 = step;
            tmp     = true;
            kid     = killId++;
            // Once a side has resolved, we need to cancel the side that is still
            // pending before we can continue.
            kills[kid] = kill(early, step === lhs ? head._2 : head._1, function (/* unused */) {
              return function () {
                delete kills[kid];
                if (tmp) {
                  tmp = false;
                } else if (tail === null) {
                  join(step, null, null);
                } else {
                  join(step, tail._1, tail._2);
                }
              };
            });

            if (tmp) {
              tmp = false;
              return;
            }
          }
          break;
        }

        if (tail === null) {
          head = null;
        } else {
          head = tail._1;
          tail = tail._2;
        }
      }
    }

    function resolve(fiber) {
      return function (result) {
        return function () {
          delete fibers[fiber._1];
          fiber._3 = result;
          join(result, fiber._2._1, fiber._2._2);
        };
      };
    }

    // Walks the applicative tree, substituting non-applicative nodes with
    // `FORKED` nodes. In this tree, all applicative nodes use the `_3` slot
    // as a mutable slot for memoization. In an unresolved state, the `_3`
    // slot is `EMPTY`. In the cases of `ALT` and `APPLY`, we always walk
    // the left side first, because both operations are left-associative. As
    // we `RETURN` from those branches, we then walk the right side.
    function run() {
      var status = CONTINUE;
      var step   = par;
      var head   = null;
      var tail   = null;
      var tmp, fid;

      loop: while (true) {
        tmp = null;
        fid = null;

        switch (status) {
        case CONTINUE:
          switch (step.tag) {
          case MAP:
            if (head) {
              tail = new Aff(CONS, head, tail);
            }
            head = new Aff(MAP, step._1, EMPTY, EMPTY);
            step = step._2;
            break;
          case APPLY:
            if (head) {
              tail = new Aff(CONS, head, tail);
            }
            head = new Aff(APPLY, EMPTY, step._2, EMPTY);
            step = step._1;
            break;
          case ALT:
            if (head) {
              tail = new Aff(CONS, head, tail);
            }
            head = new Aff(ALT, EMPTY, step._2, EMPTY);
            step = step._1;
            break;
          default:
            // When we hit a leaf value, we suspend the stack in the `FORKED`.
            // When the fiber resolves, it can bubble back up the tree.
            fid    = fiberId++;
            status = RETURN;
            tmp    = step;
            step   = new Aff(FORKED, fid, new Aff(CONS, head, tail), EMPTY);
            tmp    = Fiber(util, supervisor, tmp);
            tmp.onComplete({
              rethrow: false,
              handler: resolve(step)
            })();
            fibers[fid] = tmp;
            if (supervisor) {
              supervisor.register(tmp);
            }
          }
          break;
        case RETURN:
          // Terminal case, we are back at the root.
          if (head === null) {
            break loop;
          }
          // If we are done with the right side, we need to continue down the
          // left. Otherwise we should continue up the stack.
          if (head._1 === EMPTY) {
            head._1 = step;
            status  = CONTINUE;
            step    = head._2;
            head._2 = EMPTY;
          } else {
            head._2 = step;
            step    = head;
            if (tail === null) {
              head  = null;
            } else {
              head  = tail._1;
              tail  = tail._2;
            }
          }
        }
      }

      // Keep a reference to the tree root so it can be cancelled.
      root = step;

      for (fid = 0; fid < fiberId; fid++) {
        fibers[fid].run();
      }
    }

    // Cancels the entire tree. If there are already subtrees being canceled,
    // we need to first cancel those joins. We will then add fresh joins for
    // all pending branches including those that were in the process of being
    // canceled.
    function cancel(error, cb) {
      interrupt = util.left(error);
      var innerKills;
      for (var kid in kills) {
        if (kills.hasOwnProperty(kid)) {
          innerKills = kills[kid];
          for (kid in innerKills) {
            if (innerKills.hasOwnProperty(kid)) {
              innerKills[kid]();
            }
          }
        }
      }

      kills = null;
      var newKills = kill(error, root, cb);

      return function (killError) {
        return new Aff(ASYNC, function (killCb) {
          return function () {
            for (var kid in newKills) {
              if (newKills.hasOwnProperty(kid)) {
                newKills[kid]();
              }
            }
            return nonCanceler;
          };
        });
      };
    }

    run();

    return function (killError) {
      return new Aff(ASYNC, function (killCb) {
        return function () {
          return cancel(killError, killCb);
        };
      });
    };
  }

  function sequential(util, supervisor, par) {
    return new Aff(ASYNC, function (cb) {
      return function () {
        return runPar(util, supervisor, par, cb);
      };
    });
  }

  Aff.EMPTY       = EMPTY;
  Aff.Pure        = AffCtr(PURE);
  Aff.Throw       = AffCtr(THROW);
  Aff.Catch       = AffCtr(CATCH);
  Aff.Sync        = AffCtr(SYNC);
  Aff.Async       = AffCtr(ASYNC);
  Aff.Bind        = AffCtr(BIND);
  Aff.Bracket     = AffCtr(BRACKET);
  Aff.Fork        = AffCtr(FORK);
  Aff.Seq         = AffCtr(SEQ);
  Aff.ParMap      = AffCtr(MAP);
  Aff.ParApply    = AffCtr(APPLY);
  Aff.ParAlt      = AffCtr(ALT);
  Aff.Fiber       = Fiber;
  Aff.Supervisor  = Supervisor;
  Aff.Scheduler   = Scheduler;
  Aff.nonCanceler = nonCanceler;

  return Aff;
}();

exports._pure = Aff.Pure;

exports._throwError = Aff.Throw;

exports._catchError = function (aff) {
  return function (k) {
    return Aff.Catch(aff, k);
  };
};

exports._map = function (f) {
  return function (aff) {
    if (aff.tag === Aff.Pure.tag) {
      return Aff.Pure(f(aff._1));
    } else {
      return Aff.Bind(aff, function (value) {
        return Aff.Pure(f(value));
      });
    }
  };
};

exports._bind = function (aff) {
  return function (k) {
    return Aff.Bind(aff, k);
  };
};

exports._fork = function (immediate) {
  return function (aff) {
    return Aff.Fork(immediate, aff);
  };
};

exports._liftEff = Aff.Sync;

exports._parAffMap = function (f) {
  return function (aff) {
    return Aff.ParMap(f, aff);
  };
};

exports._parAffApply = function (aff1) {
  return function (aff2) {
    return Aff.ParApply(aff1, aff2);
  };
};

exports._parAffAlt = function (aff1) {
  return function (aff2) {
    return Aff.ParAlt(aff1, aff2);
  };
};

exports.makeAff = Aff.Async;

exports.generalBracket = function (acquire) {
  return function (options) {
    return function (k) {
      return Aff.Bracket(acquire, options, k);
    };
  };
};

exports._makeFiber = function (util, aff) {
  return function () {
    return Aff.Fiber(util, null, aff);
  };
};

exports._makeSupervisedFiber = function (util, aff) {
  return function () {
    var supervisor = Aff.Supervisor(util);
    return {
      fiber: Aff.Fiber(util, supervisor, aff),
      supervisor: supervisor
    };
  };
};

exports._killAll = function (error, supervisor, cb) {
  return supervisor.killAll(error, cb);
};

exports._delay = function () {
  function setDelay(n, k) {
    if (n === 0 && typeof setImmediate !== "undefined") {
      return setImmediate(k);
    } else {
      return setTimeout(k, n);
    }
  }

  function clearDelay(n, t) {
    if (n === 0 && typeof clearImmediate !== "undefined") {
      return clearImmediate(t);
    } else {
      return clearTimeout(t);
    }
  }

  return function (right, ms) {
    return Aff.Async(function (cb) {
      return function () {
        var timer = setDelay(ms, cb(right()));
        return function () {
          return Aff.Sync(function () {
            return right(clearDelay(ms, timer));
          });
        };
      };
    });
  };
}();

exports._sequential = Aff.Seq;