internal pronto

internal/pronto.cm

@@ -0,0 +1,366 @@
+// pronto.cm
+// Extremism in the pursuit of parallelism is no vice.
+// Based on Douglas Crockford's parseq, adapted for Cell.
+// Time is in seconds.
+
+function make_reason(factory, excuse, evidence) {
+  var msg = 'pronto.' + factory
+  if (excuse) msg = msg + ': ' + excuse
+  return { message: msg, evidence: evidence }
+}
+
+function is_requestor(fn) {
+  return is_function(fn) && (length(fn) == 1 || length(fn) == 2)
+}
+
+function check_requestors(list, factory) {
+  if (!is_array(list) || some(list, r => !is_requestor(r))) {
+    log.error(make_reason(factory, 'Bad requestor array.', list).message)
+    disrupt
+  }
+}
+
+function check_callback(cb, factory) {
+  if (!is_function(cb) || length(cb) != 2) {
+    log.error(make_reason(factory, 'Not a callback.', cb).message)
+    disrupt
+  }
+}
+
+// fallback(requestor_array)
+// Tries each requestor in order until one succeeds.
+function fallback(requestor_array) {
+  def factory = 'fallback'
+  if (!is_array(requestor_array) || length(requestor_array) == 0) {
+    log.error(make_reason(factory, 'Empty requestor array.').message)
+    disrupt
+  }
+  check_requestors(requestor_array, factory)
+
+  return function fallback_requestor(callback, value) {
+    check_callback(callback, factory)
+    var index = 0
+    var current_cancel = null
+    var cancelled = false
+
+    function cancel(reason) {
+      var _c = null
+      cancelled = true
+      if (current_cancel) {
+        _c = function() { current_cancel(reason) } disruption {}
+        _c()
+        current_cancel = null
+      }
+    }
+
+    function try_next() {
+      if (cancelled) return
+      if (index >= length(requestor_array)) {
+        callback(null, make_reason(factory, 'All requestors failed.'))
+        return
+      }
+
+      def requestor = requestor_array[index]
+      index = index + 1
+
+      var _run = function() {
+        current_cancel = requestor(function(val, reason) {
+          if (cancelled) return
+          current_cancel = null
+          if (val != null) {
+            callback(val)
+          } else {
+            try_next()
+          }
+        }, value)
+      } disruption {
+        try_next()
+      }
+      _run()
+    }
+
+    try_next()
+    return cancel
+  }
+}
+
+// parallel(requestor_array, throttle, need)
+// Runs requestors in parallel, collecting all results.
+function parallel(requestor_array, throttle, need) {
+  def factory = 'parallel'
+  if (!is_array(requestor_array)) {
+    log.error(make_reason(factory, 'Not an array.', requestor_array).message)
+    disrupt
+  }
+  check_requestors(requestor_array, factory)
+
+  def len = length(requestor_array)
+  if (len == 0)
+    return function(callback, value) { callback([]) }
+
+  var _need = need
+  if (_need == null) _need = len
+  if (!is_number(_need) || _need < 0 || _need > len) {
+    log.error(make_reason(factory, 'Bad need.', _need).message)
+    disrupt
+  }
+
+  if (throttle != null && (!is_number(throttle) || throttle < 1)) {
+    log.error(make_reason(factory, 'Bad throttle.', throttle).message)
+    disrupt
+  }
+
+  return function parallel_requestor(callback, value) {
+    check_callback(callback, factory)
+    def results = array(len)
+    def cancel_list = array(len)
+    var next_index = 0
+    var successes = 0
+    var failures = 0
+    var finished = false
+
+    function cancel(reason) {
+      if (finished) return
+      finished = true
+      arrfor(cancel_list, c => {
+        var _c = function() { if (is_function(c)) c(reason) } disruption {}
+        _c()
+      })
+    }
+
+    function start_one() {
+      if (finished || next_index >= len) return
+      def idx = next_index
+      next_index = next_index + 1
+      def requestor = requestor_array[idx]
+
+      var _run = function() {
+        cancel_list[idx] = requestor(function(val, reason) {
+          if (finished) return
+          cancel_list[idx] = null
+
+          if (val != null) {
+            results[idx] = val
+            successes = successes + 1
+            if (successes >= _need) {
+              finished = true
+              cancel(make_reason(factory, 'Finished.'))
+              callback(results)
+              return
+            }
+          } else {
+            failures = failures + 1
+            if (failures > len - _need) {
+              cancel(reason)
+              callback(null, reason || make_reason(factory, 'Too many failures.'))
+              return
+            }
+          }
+
+          start_one()
+        }, value)
+      } disruption {
+        failures = failures + 1
+        if (failures > len - _need) {
+          cancel(make_reason(factory, 'Requestor threw.'))
+          callback(null, make_reason(factory, 'Requestor threw.'))
+          return
+        }
+        start_one()
+      }
+      _run()
+    }
+
+    def concurrent = throttle ? min(throttle, len) : len
+    var i = 0
+    while (i < concurrent) { start_one(); i = i + 1 }
+
+    return cancel
+  }
+}
+
+// race(requestor_array, throttle, need)
+// Runs requestors in parallel, returns first success(es).
+function race(requestor_array, throttle, need) {
+  def factory = 'race'
+  if (!is_array(requestor_array) || length(requestor_array) == 0) {
+    log.error(make_reason(factory, 'Empty requestor array.').message)
+    disrupt
+  }
+  check_requestors(requestor_array, factory)
+
+  def len = length(requestor_array)
+  var _need = need
+  if (_need == null) _need = 1
+  if (!is_number(_need) || _need < 1 || _need > len) {
+    log.error(make_reason(factory, 'Bad need.', _need).message)
+    disrupt
+  }
+
+  if (throttle != null && (!is_number(throttle) || throttle < 1)) {
+    log.error(make_reason(factory, 'Bad throttle.', throttle).message)
+    disrupt
+  }
+
+  return function race_requestor(callback, value) {
+    check_callback(callback, factory)
+    def results = array(len)
+    def cancel_list = array(len)
+    var next_index = 0
+    var successes = 0
+    var failures = 0
+    var finished = false
+
+    function cancel(reason) {
+      if (finished) return
+      finished = true
+      arrfor(cancel_list, c => {
+        var _c = function() { if (is_function(c)) c(reason) } disruption {}
+        _c()
+      })
+    }
+
+    function start_one() {
+      if (finished || next_index >= len) return
+      def idx = next_index
+      next_index = next_index + 1
+      def requestor = requestor_array[idx]
+
+      var _run = function() {
+        cancel_list[idx] = requestor(function(val, reason) {
+          if (finished) return
+          cancel_list[idx] = null
+
+          if (val != null) {
+            results[idx] = val
+            successes = successes + 1
+            if (successes >= _need) {
+              cancel(make_reason(factory, 'Winner.'))
+              if (_need == 1) {
+                callback(val)
+              } else {
+                callback(results)
+              }
+              return
+            }
+          } else {
+            failures = failures + 1
+            if (failures > len - _need) {
+              cancel(reason)
+              callback(null, reason || make_reason(factory, 'All failed.'))
+              return
+            }
+          }
+
+          start_one()
+        }, value)
+      } disruption {
+        failures = failures + 1
+        if (failures > len - _need) {
+          cancel(make_reason(factory, 'Requestor threw.'))
+          callback(null, make_reason(factory, 'Requestor threw.'))
+          return
+        }
+        start_one()
+      }
+      _run()
+    }
+
+    def concurrent = throttle ? min(throttle, len) : len
+    var i = 0
+    while (i < concurrent) { start_one(); i = i + 1 }
+
+    return cancel
+  }
+}
+
+// sequence(requestor_array)
+// Runs requestors one at a time, passing result to next.
+function sequence(requestor_array) {
+  def factory = 'sequence'
+  if (!is_array(requestor_array)) {
+    log.error(make_reason(factory, 'Not an array.', requestor_array).message)
+    disrupt
+  }
+  check_requestors(requestor_array, factory)
+
+  if (length(requestor_array) == 0)
+    return function(callback, value) { callback(value) }
+
+  return function sequence_requestor(callback, value) {
+    check_callback(callback, factory)
+    var index = 0
+    var current_cancel = null
+    var cancelled = false
+
+    function cancel(reason) {
+      var _c = null
+      cancelled = true
+      if (current_cancel) {
+        _c = function() { current_cancel(reason) } disruption {}
+        _c()
+        current_cancel = null
+      }
+    }
+
+    function run_next(val) {
+      if (cancelled) return
+      if (index >= length(requestor_array)) {
+        callback(val)
+        return
+      }
+
+      def requestor = requestor_array[index]
+      index = index + 1
+
+      var _run = function() {
+        current_cancel = requestor(function(result, reason) {
+          if (cancelled) return
+          current_cancel = null
+          if (result == null) {
+            callback(null, reason)
+          } else {
+            run_next(result)
+          }
+        }, val)
+      } disruption {
+        callback(null, make_reason(factory, 'Requestor threw.'))
+      }
+      _run()
+    }
+
+    run_next(value)
+    return cancel
+  }
+}
+
+// requestorize(unary)
+// Converts a unary function into a requestor.
+function requestorize(unary) {
+  def factory = 'requestorize'
+  if (!is_function(unary)) {
+    log.error(make_reason(factory, 'Not a function.', unary).message)
+    disrupt
+  }
+
+  return function requestorized(callback, value) {
+    check_callback(callback, factory)
+    var _run = function() {
+      def result = unary(value)
+      callback(result == null ? true : result)
+    } disruption {
+      callback(null, make_reason(factory, 'Function threw.'))
+    }
+    _run()
+  }
+}
+
+return {
+  fallback: fallback,
+  parallel: parallel,
+  race: race,
+  sequence: sequence,
+  requestorize: requestorize,
+  is_requestor: is_requestor,
+  check_callback: check_callback
+}