.defragmentHaps() (#299)

packages/core/pattern.mjs

@@ -534,6 +534,58 @@ export class Pattern {
     return this.filterHaps((hap) => hap.whole);
   }
 
+  /**
+   * Combines adjacent haps with the same value and whole.  Only
+   * intended for use in tests.
+   */
+  defragmentHaps() {
+    // remove continuous haps
+    const pat = this.discreteOnly();
+    
+    return pat.withHaps((haps) => {
+      const result = [];
+      for (var i=0; i < haps.length; ++i) {
+        var searching = true;
+        var a = haps[i];
+        while (searching) {
+          const a_value = JSON.stringify(haps[i].value);
+          var found = false;
+
+          for(var j=i+1; j<haps.length; j++) {
+            const b = haps[j];
+
+            if (a.whole.equals(b.whole)) {
+              if (a.part.begin.eq(b.part.end)) {
+                if (a_value === JSON.stringify(b.value)) {
+                  // eat the matching hap into 'a'
+                  a = new Hap(a.whole, new TimeSpan(b.part.begin, a.part.end), a.value)
+                  haps.splice(j,1);
+                  // restart the search
+                  found = true;
+                  break;
+                }
+              }
+              else if (b.part.begin.eq(a.part.end)) {
+                if (a_value == JSON.stringify(b.value)) {
+                  // eat the matching hap into 'a'
+                  a = new Hap(a.whole, new TimeSpan(a.part.begin, b.part.end), a.value)
+                  haps.splice(j,1);
+                  // restart the search
+                  found = true;
+                  break;
+                }
+              }
+            }
+          }
+          
+          searching = found;
+        }
+        result.push(a);
+      }
+      return result;
+    });
+  }
+
   /**
    * Queries the pattern for the first cycle, returning Haps. Mainly of use when
    * debugging a pattern.

packages/core/test/pattern.test.mjs

@@ -915,4 +915,22 @@ describe('Pattern', () => {
       expect(sequence(1, 2).add.squeeze(4, 5).firstCycle()).toStrictEqual(sequence(5, 6, 6, 7).firstCycle());
     });
   });
+  describe('defragmentHaps', () => {
+    it('Can merge two touching haps with same whole and value', () => {
+      expect(stack(pure('a').mask(1,0), pure('a').mask(0,1)).defragmentHaps().firstCycle().length)
+        .toStrictEqual(1);
+    });
+    it('Doesnt merge two overlapping haps', () => {
+      expect(stack(pure('a').mask(1,1,0), pure('a').mask(0,1)).defragmentHaps().firstCycle().length)
+        .toStrictEqual(2);
+    });
+    it('Doesnt merge two touching haps with different values', () => {
+      expect(stack(pure('a').mask(1,0), pure('b').mask(0,1)).defragmentHaps().firstCycle().length)
+        .toStrictEqual(2);
+    });
+    it('Doesnt merge two touching haps with different wholes', () => {
+      expect(stack(sequence('a', silence), pure('a').mask(0,1)).defragmentHaps().firstCycle().length)
+        .toStrictEqual(2);
+    });
+  });
 });