Utility to get the longest straight chunk of a linestring

test/spec/ol/geom/flat/straightchunk.test.js

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+goog.require('ol.geom.flat.straightchunk');
+
+
+describe('ol.geom.flat.straightchunk', function() {
+
+  describe('ol.geom.flat.straightchunk.lineString', function() {
+
+    describe('single segment with stride == 3', function() {
+      var flatCoords = [0, 0, 42, 1, 1, 42];
+      var stride = 3;
+
+      it('returns whole line with angle delta', function() {
+        var got = ol.geom.flat.straightchunk.lineString(Math.PI / 4, flatCoords, 0, 6, stride);
+        expect(got).to.eql([0, 6]);
+      });
+
+      it('returns whole line with zero angle delta', function() {
+        var got = ol.geom.flat.straightchunk.lineString(0, flatCoords, 0, 6, stride);
+        expect(got).to.eql([0, 6]);
+      });
+
+    });
+
+    describe('short line string', function() {
+      var flatCoords = [0, 0, 1, 0, 1, 1, 0, 1];
+      var stride = 2;
+
+      it('returns whole line if straight enough', function() {
+        var got = ol.geom.flat.straightchunk.lineString(Math.PI, flatCoords, 0, 8, stride);
+        expect(got).to.eql([0, 8]);
+      });
+
+      it('returns first matching chunk if all chunk lengths are the same', function() {
+        var got = ol.geom.flat.straightchunk.lineString(Math.PI / 4, flatCoords, 0, 8, stride);
+        expect(got).to.eql([0, 4]);
+      });
+
+    });
+
+    describe('longer line string', function() {
+      var flatCoords = [0, 0, 1, 0, 1, 1, 0, 1, 0, -1, -1, -1, -1, 0, -1, 2, -2, 4];
+      var stride = 2;
+
+      it('returns stright chunk from within the linestring', function() {
+        var got = ol.geom.flat.straightchunk.lineString(0, flatCoords, 0, 18, stride);
+        expect(got).to.eql([10, 16]);
+      });
+
+      it('returns long chunk at the end if angle and length within threshold', function() {
+        var got = ol.geom.flat.straightchunk.lineString(Math.PI / 4, flatCoords, 0, 18, stride);
+        expect(got).to.eql([10, 18]);
+      });
+
+    });
+
+  });
+
+});