Add list operation

README.md

@@ -16,6 +16,11 @@ By default, it uses port `8080`, this can be changed by setting up `PORT` env. D
 See [websocket_test.go](websocket_test.go) for more examples.
 
 ### Queries
+#### List values
+```
+list user
+```
+
 #### Get value
 ```
 select username

database.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"fmt"
+	"strings"
 )
 
 type Database struct {
@@ -14,6 +15,26 @@ func NewDatabase() Database {
 	return Database{make(map[string]string), make(map[string]float64), make(map[string][]string)}
 }
 
+func (d Database) List(prefix string) []string {
+	keys := []string{}
+	for key := range d.Values {
+		if strings.HasPrefix(key, prefix) {
+			keys = append(keys, key)
+		}
+	}
+	for key := range d.Counters {
+		if strings.HasPrefix(key, prefix) {
+			keys = append(keys, key)
+		}
+	}
+	for key := range d.Lists {
+		if strings.HasPrefix(key, prefix) {
+			keys = append(keys, key)
+		}
+	}
+	return keys
+}
+
 func (d Database) Select(key string) []string {
 	if value, ok := d.Values[key]; ok {
 		return []string{value}

database_test.go

@@ -92,3 +92,18 @@ func TestDatabase_Clear(t *testing.T) {
 	values := database.Select(key)
 	assert.DeepEqual(t, values, []string{""})
 }
+
+func TestDatabase_List(t *testing.T) {
+	// Given database with user data
+	database := NewDatabase()
+	database.Update("user_name", "John")
+	database.Increment("user_money", 100.0)
+	database.Append("user_orders", "order 1")
+	database.Increment("account_money", 1000.0)
+
+	// When we get user keys
+	keys := database.List("user_")
+
+	// Then user keys are returned
+	assert.DeepEqual(t, keys, []string{"user_name", "user_money", "user_orders"})
+}

query.go

@@ -16,6 +16,14 @@ func (q EmptyQuery) Execute(_ Database) []string {
 	return []string{}
 }
 
+type ListQuery struct {
+	Key string
+}
+
+func (q ListQuery) Execute(database Database) []string {
+	return database.List(q.Key)
+}
+
 type SelectQuery struct {
 	Key string
 }
@@ -61,6 +69,9 @@ func ParseQuery(query string) Query {
 	}
 	operation := query[:i]
 	key := query[i+1:]
+	if operation == "list" {
+		return ListQuery{key}
+	}
 	if operation == "select" {
 		return SelectQuery{key}
 	}

query_test.go

@@ -10,7 +10,8 @@ func TestParseQuery(t *testing.T) {
 		Query    string
 		Expected Query
 	}{
-		"Empty":     {"select", EmptyQuery{}},
+		"Empty":     {"list", EmptyQuery{}},
+		"List":      {"list user", ListQuery{"user"}},
 		"Select":    {"select user_name", SelectQuery{"user_name"}},
 		"Update":    {"update user_name john", UpdateQuery{"user_name", "john"}},
 		"Increment": {"increment user_money 5.5", IncrementQuery{"user_money", 5.5}},

websocket_test.go

@@ -30,6 +30,13 @@ func TestWebsocket(t *testing.T) {
 	assert.NilError(t, err)
 	assert.Equal(t, string(message), "john")
 
+	// Then value is on the list
+	err = ws.WriteMessage(websocket.TextMessage, []byte("list user"))
+	assert.NilError(t, err)
+	_, message, err = ws.ReadMessage()
+	assert.NilError(t, err)
+	assert.Equal(t, string(message), "username")
+
 	// When we increment value
 	err = ws.WriteMessage(websocket.TextMessage, []byte("increment money 100"))
 	assert.NilError(t, err)