Add fuzzy match filter

filter.go

@@ -7,50 +7,49 @@ type Filter func([]Suggest, string, bool) []Suggest
 
 // FilterHasPrefix checks whether the string completions.Text begins with sub.
 func FilterHasPrefix(completions []Suggest, sub string, ignoreCase bool) []Suggest {
-	if sub == "" {
-		return completions
-	}
-	if ignoreCase {
-		sub = strings.ToUpper(sub)
-	}
-
-	ret := make([]Suggest, 0, len(completions))
-	for i := range completions {
-		c := completions[i].Text
-		if ignoreCase {
-			c = strings.ToUpper(c)
-		}
-		if strings.HasPrefix(c, sub) {
-			ret = append(ret, completions[i])
-		}
-	}
-	return ret
+	return filterCommon(completions, sub, ignoreCase, strings.HasPrefix)
 }
 
 // FilterHasSuffix checks whether the completion.Text ends with sub.
 func FilterHasSuffix(completions []Suggest, sub string, ignoreCase bool) []Suggest {
-	if sub == "" {
-		return completions
-	}
-	if ignoreCase {
-		sub = strings.ToUpper(sub)
-	}
-
-	ret := make([]Suggest, 0, len(completions))
-	for i := range completions {
-		c := completions[i].Text
-		if ignoreCase {
-			c = strings.ToUpper(c)
-		}
-		if strings.HasSuffix(c, sub) {
-			ret = append(ret, completions[i])
-		}
-	}
-	return ret
+	return filterCommon(completions, sub, ignoreCase, strings.HasSuffix)
 }
 
 // FilterContains checks whether the completion.Text contains sub.
 func FilterContains(completions []Suggest, sub string, ignoreCase bool) []Suggest {
+	return filterCommon(completions, sub, ignoreCase, strings.Contains)
+}
+
+// FilterFuzzy checks whether the completion.Text fuzzy matches sub.
+// Fuzzy searching for "dog" is equivalent to "*d*o*g*". This search term
+// would match, for example, "Good food is gone"
+//                               ^  ^      ^
+func FilterFuzzy(completions []Suggest, sub string, ignoreCase bool) []Suggest {
+	return filterCommon(completions, sub, ignoreCase, fuzzyMatch)
+}
+
+func fuzzyMatch(s, sub string) bool {
+	sChars := []rune(s)
+	subChars := []rune(sub)
+	sIdx := 0
+
+	for _, c := range subChars {
+		found := false
+		for ; sIdx < len(sChars); sIdx++ {
+			if sChars[sIdx] == c {
+				found = true
+				sIdx++
+				break
+			}
+		}
+		if !found {
+			return false
+		}
+	}
+	return true
+}
+
+func filterCommon(completions []Suggest, sub string, ignoreCase bool, test func(string, string) bool) []Suggest {
 	if sub == "" {
 		return completions
 	}
@@ -64,7 +63,7 @@ func FilterContains(completions []Suggest, sub string, ignoreCase bool) []Sugges
 		if ignoreCase {
 			c = strings.ToUpper(c)
 		}
-		if strings.Contains(c, sub) {
+		if test(c, sub) {
 			ret = append(ret, completions[i])
 		}
 	}

filter_test.go

@@ -101,6 +101,35 @@ func TestFilter(t *testing.T) {
 				{Text: "ABCDE"},
 			},
 		},
+		{
+			scenario: "Fuzzy don't ignore case",
+			filter:   FilterFuzzy,
+			list: []Suggest{
+				{Text: "abcde"},
+				{Text: "fcdej"},
+				{Text: "ABCDE"},
+			},
+			substr:     "ae",
+			ignoreCase: false,
+			expected: []Suggest{
+				{Text: "abcde"},
+			},
+		},
+		{
+			scenario: "Fuzzy ignore case",
+			filter:   FilterFuzzy,
+			list: []Suggest{
+				{Text: "abcde"},
+				{Text: "fcdej"},
+				{Text: "ABCDE"},
+			},
+			substr:     "ae",
+			ignoreCase: true,
+			expected: []Suggest{
+				{Text: "abcde"},
+				{Text: "ABCDE"},
+			},
+		},
 	}
 
 	for _, s := range scenarioTable {
@@ -109,3 +138,27 @@ func TestFilter(t *testing.T) {
 		}
 	}
 }
+
+func TestFuzzy(t *testing.T) {
+	tests := []struct {
+		s     string
+		sub   string
+		match bool
+	}{
+		{"dog house", "dog", true},
+		{"dog house", "", true},
+		{"", "", true},
+		{"this is much longer", "hhg", true},
+		{"this is much longer", "hhhg", false},
+		{"long", "longer", false},
+		{"can we do unicode 文字 with this 今日", "文字今日", true},
+		{"can we do unicode 文字 with this 今日", "d文字tt今日", true},
+		{"can we do unicode 文字 with this 今日", "d文字ttt今日", false},
+	}
+
+	for _, test := range tests {
+		if fuzzyMatch(test.s, test.sub) != test.match {
+			t.Errorf("fuzzymatch, %s in %s: expected %v, got %v", test.sub, test.s, test.match, !test.match)
+		}
+	}
+}