Fix scoring to favor exact substring matches

spec/filter-spec.coffee

@@ -15,13 +15,13 @@ rootPath = (segments...) ->
 
 describe "filtering", ->
   it "returns an array of the most accurate results", ->
-    candidates = ['Gruntfile','filter', 'bile', null, '', undefined]
-    expect(filter(candidates, 'file')).toEqual ['filter', 'Gruntfile']
+    candidates = ['Gruntfile', 'filter', 'bile', null, '', undefined]
+    expect(filter(candidates, 'file')).toEqual ['Gruntfile', 'filter']
 
   describe "when the maxResults option is set", ->
     it "limits the results to the result size", ->
       candidates = ['Gruntfile', 'filter', 'bile']
-      expect(bestMatch(candidates, 'file')).toBe 'filter'
+      expect(bestMatch(candidates, 'file')).toBe 'Gruntfile'
 
   describe "when the entries contains slashes", ->
     it "weighs basename matches higher", ->
@@ -112,6 +112,9 @@ describe "filtering", ->
     expect(bestMatch(['z_a_b', 'a_b'], 'ab')).toBe 'a_b'
     expect(bestMatch(['a_b_c', 'c_a_b'], 'ab')).toBe 'a_b_c'
 
+  it "weights matches that are substring matches higher", ->
+    expect(bestMatch(['/a/b/c/install.txt', 'inst-all.txt'])).toBe '/a/b/c/install.txt'
+
   describe "when the entries are of differing directory depths", ->
     it "places exact matches first, even if they're deeper", ->
       candidates = [

src/filter.coffee

@@ -13,6 +13,7 @@ module.exports = (candidates, query, queryHasSlashes, {key, maxResults}={}) ->
       score = scorer.score(string, query, queryHasSlashes)
       unless queryHasSlashes
         score = scorer.basenameScore(string, query, score)
+      score = scorer.substringScore(string, query, score)
       scoredCandidates.push({candidate, score}) if score > 0
 
     # Sort scores in descending order

src/fuzzaldrin.coffee

@@ -21,6 +21,7 @@ module.exports =
     query = query.replace(SpaceRegex, '')
     score = scorer.score(string, query)
     score = scorer.basenameScore(string, query, score) unless queryHasSlashes
+    score = scorer.substringScore(string, query, score)
     score
 
   match: (string, query) ->

src/scorer.coffee

@@ -42,6 +42,22 @@ exports.basenameScore = (string, query, score) ->
   score *= depth * 0.01
   score
 
+exports.substringScore = (string, query, score) ->
+  # Return a near perfect score if the query is a substring match
+  substrIndex = string.indexOf(query)
+  substrIndexi = string.toLowerCase().indexOf(query.toLowerCase())
+
+  if substrIndex >= 0
+    return score + 1.155 if substrIndex == 0
+    return score + 1.145 if string[substrIndex - 1] == PathSeparator
+    return score + 1.135
+  else if substrIndexi >= 0
+    return score + 1.15 if substrIndexi == 0
+    return score + 1.14 if string[substrIndexi - 1] == PathSeparator
+    return score + 1.13
+
+  return score
+
 exports.score = (string, query) ->
   return 1 if string is query