From bf7ffbfa8da46563dc7151ccb9e753d2b7195d7b Mon Sep 17 00:00:00 2001
From: dudaodong <lanliddd.2007@163.com>
Date: Thu, 31 Mar 2022 16:56:12 +0800
Subject: [PATCH] feat: add Intersect func

---
 maputil/map.go      | 35 +++++++++++++++++++++++++++++++++++
 maputil/map_test.go | 27 +++++++++++++++++++++++++++
 2 files changed, 62 insertions(+)

diff --git a/maputil/map.go b/maputil/map.go
index 951ba11..a22988f 100644
--- a/maputil/map.go
+++ b/maputil/map.go
@@ -4,6 +4,8 @@
 // Package maputil includes some functions to manipulate map.
 package maputil
 
+import "reflect"
+
 // Keys returns a slice of the map's keys
 func Keys[K comparable, V any](m map[K]V) []K {
 	keys := make([]K, 0, len(m))
@@ -57,3 +59,36 @@ func Filter[K comparable, V any](m map[K]V, predicate func(key K, value V) bool)
 	}
 	return res
 }
+
+// Intersect iterates over maps, return a new map of key and value pairs in all give maps
+func Intersect[K comparable, V any](maps ...map[K]V) map[K]V {
+	if len(maps) == 0 {
+		return map[K]V{}
+	}
+	if len(maps) == 1 {
+		return maps[0]
+	}
+
+	res := make(map[K]V)
+
+	reducer := func(m1, m2 map[K]V) map[K]V {
+		m := make(map[K]V)
+		for k, v1 := range m1 {
+			if v2, ok := m2[k]; ok && reflect.DeepEqual(v1, v2) {
+				m[k] = v1
+			}
+		}
+		return m
+	}
+
+	reduceMaps := make([]map[K]V, 2, 2)
+	res = reducer(maps[0], maps[1])
+
+	for i := 2; i < len(maps); i++ {
+		reduceMaps[0] = res
+		reduceMaps[1] = maps[i]
+		res = reducer(reduceMaps[0], reduceMaps[1])
+	}
+
+	return res
+}
diff --git a/maputil/map_test.go b/maputil/map_test.go
index 97a7233..7957c09 100644
--- a/maputil/map_test.go
+++ b/maputil/map_test.go
@@ -103,3 +103,30 @@ func TestFilter(t *testing.T) {
 		"d": 4,
 	}, acturl)
 }
+
+func TestIntersect(t *testing.T) {
+	assert := internal.NewAssert(t, "TestIntersect")
+
+	m1 := map[string]int{
+		"a": 1,
+		"b": 2,
+		"c": 3,
+	}
+
+	m2 := map[string]int{
+		"a": 1,
+		"b": 2,
+		"c": 6,
+		"d": 7,
+	}
+
+	m3 := map[string]int{
+		"a": 1,
+		"b": 9,
+		"e": 9,
+	}
+
+	assert.Equal(map[string]int{"a": 1, "b": 2, "c": 3}, Intersect(m1))
+	assert.Equal(map[string]int{"a": 1, "b": 2}, Intersect(m1, m2))
+	assert.Equal(map[string]int{"a": 1}, Intersect(m1, m2, m3))
+}