WIP

index.js

@@ -60,7 +60,31 @@ module.exports = function(version, language) {
 
             return config.join('');
         },
-        compile: function(step) {
+        precompilePriorityTable: function(leg) {
+            priorityTable = {};
+
+            function safeIncrease(obj, key) {
+                if (obj[key]) {
+                    obj[key] = obj[key] + 1
+                } else {
+                    obj[key] = 1
+                }
+            }
+
+            leg.steps.forEach(function(step) {
+                if (step.name) {
+                    safeIncrease(priorityTable, step.name);
+                }
+                if (step.ref) {
+                    step.ref.split(';').forEach(function(ref) {
+                        safeIncrease(priorityTable, ref)
+                    })
+                }
+            });
+
+            return priorityTable;
+        },
+        compile: function(step, lookupTable) {
             if (!step.maneuver) throw new Error('No step maneuver provided');
 
             var type = step.maneuver.type;
@@ -129,6 +153,47 @@ module.exports = function(version, language) {
             }
             name = name.replace(' (' + step.ref + ')', '');
 
+            // alter by priority
+            if (priorityTable) {
+                // get all scores
+                collect = [];
+                if (name) {
+                    if (!priorityTable[name]) throw new Error('name ' + name + ' not in priorityTable');
+                    collect.push({
+                        type: 'name',
+                        value: name,
+                        score: priorityTable[name]
+                    });
+                }
+                if (step.ref) {
+                    step.ref.split(';').forEach(function(ref) {
+                        if(!priorityTable[ref]) throw new Error('ref ' + ref + ' not in priorityTable');
+                        collect.push({
+                            type: 'ref',
+                            value: ref,
+                            score: priorityTable[ref]
+                        });
+                    });
+                }
+
+                // find the highest score
+                res = collect.reduce(function(a, b) {
+                    if (a.score < b.score) return b;
+                }, { score: 0 });
+
+                // save for later
+                if (res.type === 'name') {
+                    name = res.value;
+                    ref = null;
+                } else if (res.type === 'ref') {
+                    name = null;
+                    ref = res.value;
+                } else {
+                    throw new Error('unknown type ' + res.type + 'in ' + JSON.stringify(res));
+                }
+            }
+
+            // select
             if (name && ref && name !== ref) {
                 wayName = name + ' (' + ref + ')';
             } else if (!name && ref) {

test/index_test.js

@@ -116,3 +116,68 @@ tape.test('v5 compile', function(t) {
         assert.end();
     });
 });
+
+tape.only('v5 precompileLookupTable and compile', function(t) {
+    var v5Instructions = instructions('v5', process.env.LANGUAGE || 'en');
+    var lookupTable;
+    var fixture = {
+        steps: [
+            {
+                maneuver: {
+                    type: 'depart',
+                    modifier: 'right',
+                    bearing_after: 270
+                },
+                name: "Chain Bridge Road",
+                ref: "VA 123"
+            },
+            {
+                maneuver: {
+                    type: 'turn',
+                    modifier: 'left',
+                    bearing_after: 270
+                },
+                name: "George Washington Memorial Parkway",
+                ref: "VA 123"
+            },
+            {
+                maneuver: {
+                    type: 'arrive',
+                    modifier: 'right',
+                    bearing_after: 270
+                },
+                name: "Chain Bridge Road",
+                ref: "VA 123"
+            }
+        ]
+    };
+
+    t.test('generates expected lookup table', function(assert) {
+        lookupTable = v5Instructions.precompilePriorityTable(fixture);
+
+        assert.deepEqual(lookupTable, {
+            "Chain Bridge Road": 2,
+            "VA 123": 3,
+            "George Washington Memorial Parkway": 1
+        });
+
+        assert.end();
+    });
+
+    t.test('has expected compile results', function(assert) {
+        assert.deepEqual(fixture.steps.map((step) => {
+            return v5Instructions.compile(step, lookupTable);
+        }), [
+            'Head west on VA 123',
+            'Turn left onto VA 123',
+            'You have arrived at your destination, on the right'
+        ]);
+
+        // Previously:
+        // 'Head west on Chain Bridge Road (VA 123)',
+        // 'Turn left onto George Washington Memorial Parkway (VA 123)',
+        // 'You have arrived at your destination, on the right'
+
+        assert.end();
+    });
+});