Add GetLongestMatch API (#7)

* fix(radix): disable export of size and root

* chore(readme): update readme

* feat(GetLongestMatch): add GetLongestMatch, fix an unit test issue

README.md

@@ -9,7 +9,7 @@ _A fast and simple (200+ lines) radix tree implementation in Go/Golang._
 ### Features
 
 * good performance ([benchmark](https://github.com/ihexxa/radix-bench))
-* more ways to query: GetAllMatches
+* more ways to query (Get, GetAllMatches, GetLongestMatch, BFS)
 * simple interfaces
 * well tested (unit tests and random tests)
 
@@ -28,6 +28,7 @@ treeSize := rTree.Size() // get the size of the radix tree
 
 val, ok := rTree.Get("key") // get the value by key
 val, ok := rTree.GetAllMatches("key") // get all prefix matches of the key
+val, ok := rTree.GetLongestMatch("key") // get the longest prefix match of the key
 
 // override the value of the key if it exists in the radix tree
 // and the old value will be returned if it exists in the radix tree

radix.go

@@ -117,6 +117,16 @@ func (T *RTree) GetAllMatches(key string) []interface{} {
 	}
 }
 
+// GetLongestMatch returns the longest match in the tree according to the key
+// if no match is found, it returns nil and false
+func (T *RTree) GetLongestMatch(key string) (interface{}, bool) {
+	matches := T.GetAllMatches(key)
+	if len(matches) == 0 {
+		return nil, false
+	}
+	return matches[len(matches)-1], true
+}
+
 // split splits node into two nodes: parent and child.
 // node1's prefix is [0, offset)
 // node2's prefix is [offset, len-1]

radix_unit_test.go

@@ -1,11 +1,14 @@
 package qradix
 
-import "testing"
+import (
+	"testing"
+)
 
 func TestOperations(t *testing.T) {
 	t.Run("test Insert", testInsert)
 	t.Run("test Remove", testRemove)
 	t.Run("test GetAllMatches", testGetAllMatches)
+	t.Run("test GetLongestMatch", testGetLongestMatch)
 }
 
 func testInsert(t *testing.T) {
@@ -67,7 +70,6 @@ func testRemove(t *testing.T) {
 }
 
 func testGetAllMatches(t *testing.T) {
-	rTree := NewRTree()
 	type TestCase struct {
 		desc    string
 		inserts []string
@@ -88,9 +90,17 @@ func testGetAllMatches(t *testing.T) {
 			get:     "a",
 			expect:  []string{"a"},
 		},
+		&TestCase{
+			desc:    "found a match shorter than key",
+			inserts: []string{"a", "ab", "abd"},
+			get:     "abc",
+			expect:  []string{"a", "ab"},
+		},
 	}
 
 	for _, tc := range testCases {
+		rTree := NewRTree()
+
 		for _, insert := range tc.inserts {
 			rTree.Insert(insert, insert)
 		}
@@ -103,3 +113,56 @@ func testGetAllMatches(t *testing.T) {
 		}
 	}
 }
+
+func testGetLongestMatch(t *testing.T) {
+	type TestCase struct {
+		desc    string
+		inserts []string
+		get     string
+		expect  []string
+	}
+
+	testCases := []*TestCase{
+		&TestCase{
+			desc:    "found a match as long as key",
+			inserts: []string{"a", "ab", "ac", "abc", "abcd"},
+			get:     "abc",
+			expect:  []string{"abc"},
+		},
+		&TestCase{
+			desc:    "found a match shorter than key",
+			inserts: []string{"a", "ab", "abd"},
+			get:     "abc",
+			expect:  []string{"ab"},
+		},
+		&TestCase{
+			desc:    "no match found",
+			inserts: []string{"a", "ab", "abd"},
+			get:     "c",
+			expect:  []string{},
+		},
+	}
+
+	for _, tc := range testCases {
+		rTree := NewRTree()
+
+		for _, insert := range tc.inserts {
+			rTree.Insert(insert, insert)
+		}
+
+		match, found := rTree.GetLongestMatch(tc.get)
+		if len(tc.expect) == 0 {
+			if found {
+				t.Errorf("GetLongestMatch(%s): expect no match but found one %s", tc.desc, match)
+			} else {
+				continue
+			}
+		} else {
+			if tc.expect[0] != match {
+				t.Errorf("GetLongestMatch(%s): got %s expect %s", tc.desc, match, tc.expect[0])
+			} else {
+				continue
+			}
+		}
+	}
+}