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

packages/core/timespan.mjs

@@ -0,0 +1,103 @@
+import Fraction from './fraction.mjs';
+
+export class TimeSpan {
+  constructor(begin, end) {
+    this.begin = Fraction(begin);
+    this.end = Fraction(end);
+  }
+
+  get spanCycles() {
+    const spans = [];
+    var begin = this.begin;
+    const end = this.end;
+    const end_sam = end.sam();
+
+    while (end.gt(begin)) {
+      // If begin and end are in the same cycle, we're done.
+      if (begin.sam().equals(end_sam)) {
+        spans.push(new TimeSpan(begin, this.end));
+        break;
+      }
+      // add a timespan up to the next sam
+      const next_begin = begin.nextSam();
+      spans.push(new TimeSpan(begin, next_begin));
+
+      // continue with the next cycle
+      begin = next_begin;
+    }
+    return spans;
+  }
+
+  cycleArc() {
+    // Shifts a timespan to one of equal duration that starts within cycle zero.
+    // (Note that the output timespan probably does not start *at* Time 0 --
+    // that only happens when the input Arc starts at an integral Time.)
+    const b = this.begin.cyclePos();
+    const e = b + (this.end - this.begin);
+    return new TimeSpan(b, e);
+  }
+
+  withTime(func_time) {
+    // Applies given function to both the begin and end time of the timespan"""
+    return new TimeSpan(func_time(this.begin), func_time(this.end));
+  }
+
+  withEnd(func_time) {
+    // Applies given function to the end time of the timespan"""
+    return new TimeSpan(this.begin, func_time(this.end));
+  }
+
+  withCycle(func_time) {
+    // Like withTime, but time is relative to relative to the cycle (i.e. the
+    // sam of the start of the timespan)
+    const sam = this.begin.sam();
+    const b = sam.add(func_time(this.begin.sub(sam)));
+    const e = sam.add(func_time(this.end.sub(sam)));
+    return new TimeSpan(b, e);
+  }
+
+  intersection(other) {
+    // Intersection of two timespans, returns None if they don't intersect.
+    const intersect_begin = this.begin.max(other.begin);
+    const intersect_end = this.end.min(other.end);
+
+    if (intersect_begin.gt(intersect_end)) {
+      return undefined;
+    }
+    if (intersect_begin.equals(intersect_end)) {
+      // Zero-width (point) intersection - doesn't intersect if it's at the end of a
+      // non-zero-width timespan.
+      if (intersect_begin.equals(this.end) && this.begin.lt(this.end)) {
+        return undefined;
+      }
+      if (intersect_begin.equals(other.end) && other.begin.lt(other.end)) {
+        return undefined;
+      }
+    }
+    return new TimeSpan(intersect_begin, intersect_end);
+  }
+
+  intersection_e(other) {
+    // Like 'sect', but raises an exception if the timespans don't intersect.
+    const result = this.intersection(other);
+    if (result == undefined) {
+      // TODO - raise exception
+      // raise ValueError(f'TimeSpan {self} and TimeSpan {other} do not intersect')
+    }
+    return result;
+  }
+
+  midpoint() {
+    return this.begin.add(this.end.sub(this.begin).div(Fraction(2)));
+  }
+
+  equals(other) {
+    return this.begin.equals(other.begin) && this.end.equals(other.end);
+  }
+
+  show() {
+    return this.begin.show() + ' -> ' + this.end.show();
+  }
+}
+
+export default TimeSpan;