fixed Trie search for single-character queries

hit.podspec

@@ -1,7 +1,7 @@
 Pod::Spec.new do |s|
 
   s.name         = "hit"
-  s.version      = "0.2"
+  s.version      = "0.3"
   s.summary      = "Lightweight full-text search written in Swift"
 
   s.description  = <<-DESC

hit/Trie.swift

@@ -53,14 +53,15 @@ public struct Trie {
 
         let prefixHeadRange = TokenRange(start: prefix.startIndex, end: prefix.startIndex.advancedBy(1))
         let prefixHead = prefix.substringWithRange(prefixHeadRange)
-
-        if length == 1 {
+        let emptyTrie = trie.token.characters.count == 0
+
+        if length == 1 && !emptyTrie {
+
             //potentially might be found if trie matches
             let match = (trie.token == prefixHead)
             return match ? trie : nil
         }
 
-        let emptyTrie = trie.token.characters.count == 0
         let tokenMatches = trie.token == prefixHead
         if emptyTrie || tokenMatches {
 

hitTests/TrieTests.swift

@@ -11,10 +11,14 @@ import XCTest
 @testable import hit
 
 class TrieTests: HitTestCase {
-
+
+    func commonWords() -> [String] {
+        let strings = ["swiftkey", "swype", "hello", "london", "reality", "fantasy", "stuff"]
+        return strings
+    }
+
     func testTrieCreation_exactMatches() {
-
-        let strings = ["swiftkey", "swype", "hello", "london", "reality", "fantasy"]
+        let strings = self.commonWords()
         let trie = Trie(strings: strings)
 
         let foundStrings = trie.stringsMatchingPrefix("sw")
@@ -54,6 +58,17 @@ class TrieTests: HitTestCase {
             _ = trie.stringsMatchingPrefix("sw")
         }
     }
+
+    func testCorrectness_singleCharSearch() {
+        let strings = self.commonWords()
+        let trie = Trie(strings: strings)
+
+        let foundStrings = Set(trie.stringsMatchingPrefix("s"))
+        XCTAssertEqual(foundStrings.count, 3)
+        XCTAssert(foundStrings.contains("swiftkey"))
+        XCTAssert(foundStrings.contains("swype"))
+        XCTAssert(foundStrings.contains("stuff"))
+    }
 
 
 }