feat: enable GetLongerMatches API with utest

Author: Jia He

radix.go

@@ -43,7 +43,10 @@ func (n *node) NextNode() (Node, bool) {
 
 // Value returns node's value, it returns nil if there is no
 func (n *node) Value() (interface{}, bool) {
-	return n.Leaf.Val, n.Leaf != nil
+	if n.Leaf != nil {
+		return n.Leaf.Val, true
+	}
+	return nil, false
 }
 
 // Extra returns node's Extra Info
@@ -73,7 +76,7 @@ type RTree struct {
 }
 
 // return common prefix's offset of s1 and s2, in byte
-// s1[:offset] == s2[:offset]
+// s1[:offset+1] == s2[:offset+1]
 func commonPrefixOffset(s1, s2 string) int {
 	i := 0
 	runes1, runes2 := []rune(s1), []rune(s2)
@@ -454,7 +457,96 @@ func (T *RTree) GetAllPrefixMatches(key string) map[string]interface{} {
 	return resultMap
 }
 
-// GetBestMatch returns the longest match in the tree according to the key
+type traverseLog struct {
+	n    *node
+	base string
+}
+
+// GetLongerMatches returns at most `limmit` matches which are longer than the key
+// if no match is found, it returns an empty map
+func (T *RTree) GetLongerMatches(key string, limit int) map[string]interface{} {
+	T.m.RLock()
+	defer T.m.RUnlock()
+
+	resultMap := map[string]interface{}{}
+	if T.root == nil {
+		return resultMap
+	} else if len(key) == 0 {
+		return resultMap
+	}
+
+	var ok bool
+	var rune1 rune
+	var matchedNode *node
+	node1 := T.root
+	pathSuffix := key
+	baseOffset := 0 // key[:baseOffset] is matched
+	for {
+		if node1 == nil {
+			return resultMap
+		}
+
+		rune1 = getRune1(pathSuffix)
+		matchedNode, ok = node1.Idx[rune1]
+		if !ok {
+			return resultMap
+		}
+
+		offset := commonPrefixOffset(matchedNode.Prefix, pathSuffix)
+		if offset == -1 {
+			// this is impossible
+			panic(errImpossible(matchedNode.Prefix, key))
+		} else if offset == len(matchedNode.Prefix)-1 && offset < len(pathSuffix)-1 {
+			pathSuffix = pathSuffix[offset+1:]
+			node1 = matchedNode.Children
+			baseOffset += offset + 1
+			continue
+		} else if offset == len(pathSuffix)-1 {
+			break
+		}
+		return resultMap
+	}
+
+	if matchedNode.Leaf != nil {
+		resultMap[key[:baseOffset]+matchedNode.Prefix] = matchedNode.Leaf.Val
+	}
+	// start from next level becasue matchedNode's siblings are not results
+	// traverse from the matchedNode and return values
+	queue := []*traverseLog{&traverseLog{
+		n:    matchedNode.Children,
+		base: key[:baseOffset] + matchedNode.Prefix,
+	}}
+	for len(queue) > 0 {
+		tlog := queue[0]
+		queue = queue[1:]
+		if tlog.n == nil {
+			continue
+		}
+
+		if tlog.n.Leaf != nil {
+			resultMap[tlog.base+tlog.n.Prefix] = tlog.n.Leaf.Val
+			if len(resultMap) > limit {
+				break
+			}
+		}
+		if tlog.n.Next != nil {
+			queue = append(queue, &traverseLog{
+				n:    tlog.n.Next,
+				base: tlog.base,
+			})
+		}
+		if tlog.n.Children != nil {
+			queue = append(queue, &traverseLog{
+				n:    tlog.n.Children,
+				base: tlog.base + tlog.n.Prefix,
+			})
+		}
+	}
+
+	return resultMap
+}
+
+// GetBestMatch returns the longest match from all existings values which key is short than the input key
 // if there is no match, it returns empty string, nil and false
 func (T *RTree) GetBestMatch(key string) (string, interface{}, bool) {
 	T.m.RLock()

radix_random_test.go

@@ -4,6 +4,7 @@ import (
 	"flag"
 	"fmt"
 	"math/rand"
+	"strings"
 	"testing"
 	"time"
 )
@@ -14,7 +15,7 @@ const (
 )
 
 var (
-	// use -args to input these options: "go test -args -d=true"
+	// use -args to input these options: "go test -args -h=10"
 	actionCount = flag.Int("c", 30, "how many actions will be applied on RTree and map")
 	insertRatio = flag.Int("i", 60, "control the the ratio between insert action and remove action")
 	maxLen      = flag.Int("l", 5, "how long will random string be generated")
@@ -29,6 +30,7 @@ func TestWithRandomKeys(t *testing.T) {
 	seedRand()
 	for i := 0; i < *testRound; i++ {
 		randomTest(t)
+		longerKeyTest(t)
 	}
 }
 
@@ -118,6 +120,31 @@ func randomTest(t *testing.T) {
 	}
 }
 
+func longerKeyTest(t *testing.T) {
+	var actions []string
+	tree := NewRTree()
+	dict := make(map[string]string)
+	randomStrings := GetTestStrings()
+
+	for i := 0; i < *actionCount; i++ {
+		key := randomStrings[rand.Intn(len(randomStrings))]
+		doRandomAction(&actions, key, tree, dict)
+	}
+
+	randomKey := randomStrings[rand.Intn(len(randomStrings))]
+	end := rand.Intn(len(randomKey)) + 1
+	start := rand.Intn(end)
+	randomKey = randomKey[start:end]
+	longerMatches := tree.GetLongerMatches(randomKey, 5)
+	if !checkLongerMatches(randomKey, longerMatches) {
+		fmt.Printf("longerMatches of (%s): %+v\n", randomKey, longerMatches)
+		printActions(actions)
+		printRTree(tree)
+		printMap(dict)
+		t.Fatalf("incorrect longer matches")
+	}
+}
+
 func checkPrefixMatches(
 	key string,
 	prefixes map[string]interface{},
@@ -138,6 +165,23 @@ func checkPrefixMatches(
 	return true
 }
 
+// checkLongerMatches only checks if key is the prefix of each longerMatches
+// Becasue currently, besides the first one,
+// it doesn't return results by the order of how much it is closed to the key
+func checkLongerMatches(
+	key string,
+	longerMatches map[string]interface{},
+) bool {
+	for longerMatch := range longerMatches {
+		if !strings.HasPrefix(longerMatch, key) {
+			fmt.Printf("%s is not a prefix of %s \n", key, longerMatch)
+			return false
+		}
+	}
+
+	return true
+}
+
 func GetTestStrings() []string {
 	var str []rune
 	var randomStrings []string