separate out strudel.mjs, make index.mjs aggregate module

packages/core/hap.mjs

@@ -0,0 +1,90 @@
+
+export class Hap {
+  /*
+      Event class, representing a value active during the timespan
+      'part'. This might be a fragment of an event, in which case the
+      timespan will be smaller than the 'whole' timespan, otherwise the
+      two timespans will be the same. The 'part' must never extend outside of the
+      'whole'. If the event represents a continuously changing value
+      then the whole will be returned as None, in which case the given
+      value will have been sampled from the point halfway between the
+      start and end of the 'part' timespan.
+      The context is to store a list of source code locations causing the event
+      */
+
+  constructor(whole, part, value, context = {}, stateful = false) {
+    this.whole = whole;
+    this.part = part;
+    this.value = value;
+    this.context = context;
+    this.stateful = stateful;
+    if (stateful) {
+      console.assert(typeof this.value === 'function', 'Stateful values must be functions');
+    }
+  }
+
+  get duration() {
+    return this.whole.end.sub(this.whole.begin).valueOf();
+  }
+
+  wholeOrPart() {
+    return this.whole ? this.whole : this.part;
+  }
+
+  withSpan(func) {
+    // Returns a new event with the function f applies to the event timespan.
+    const whole = this.whole ? func(this.whole) : undefined;
+    return new Hap(whole, func(this.part), this.value, this.context);
+  }
+
+  withValue(func) {
+    // Returns a new event with the function f applies to the event value.
+    return new Hap(this.whole, this.part, func(this.value), this.context);
+  }
+
+  hasOnset() {
+    // Test whether the event contains the onset, i.e that
+    // the beginning of the part is the same as that of the whole timespan."""
+    return this.whole != undefined && this.whole.begin.equals(this.part.begin);
+  }
+
+  resolveState(state) {
+    if (this.stateful && this.hasOnset()) {
+      console.log('stateful');
+      const func = this.value;
+      const [newState, newValue] = func(state);
+      return [newState, new Hap(this.whole, this.part, newValue, this.context, false)];
+    }
+    return [state, this];
+  }
+
+  spanEquals(other) {
+    return (this.whole == undefined && other.whole == undefined) || this.whole.equals(other.whole);
+  }
+
+  equals(other) {
+    return (
+      this.spanEquals(other) &&
+      this.part.equals(other.part) &&
+      // TODO would == be better ??
+      this.value === other.value
+    );
+  }
+
+  show() {
+    return (
+      '(' + (this.whole == undefined ? '~' : this.whole.show()) + ', ' + this.part.show() + ', ' + this.value + ')'
+    );
+  }
+
+  combineContext(b) {
+    const a = this;
+    return { ...a.context, ...b.context, locations: (a.context.locations || []).concat(b.context.locations || []) };
+  }
+
+  setContext(context) {
+    return new Hap(this.whole, this.part, this.value, context);
+  }
+}
+
+export default Hap;