Add EXPIRETIME command (#356)

* Add EXPIRETIME command

Redis documentation: https://redis.io/commands/expiretime/

Closes: #294

Signed-off-by: Wojciech Szarański <wojciech.szaranski@gmail.com>

* two more testcases

---------

Signed-off-by: Wojciech Szarański <wojciech.szaranski@gmail.com>
Co-authored-by: Wojciech Szarański <wojciech.szaranski@gmail.com>
Co-authored-by: Harmen <alicebob@lijzij.de>

cmd_generic.go

@@ -12,6 +12,13 @@ import (
 	"github.com/alicebob/miniredis/v2/server"
 )
 
+const (
+	// expiretimeReplyNoExpiration is returned by [Miniredis.cmdExpireTime] if the key exists but has no associated expiration time
+	expiretimeReplyNoExpiration = -1
+	// expiretimeReplyMissingKey is returned by [Miniredis.cmdExpireTime] if the key does not exist
+	expiretimeReplyMissingKey = -2
+)
+
 // commandsGeneric handles EXPIRE, TTL, PERSIST, &c.
 func commandsGeneric(m *Miniredis) {
 	m.srv.Register("COPY", m.cmdCopy)
@@ -20,6 +27,7 @@ func commandsGeneric(m *Miniredis) {
 	m.srv.Register("EXISTS", m.cmdExists)
 	m.srv.Register("EXPIRE", makeCmdExpire(m, false, time.Second))
 	m.srv.Register("EXPIREAT", makeCmdExpire(m, true, time.Second))
+	m.srv.Register("EXPIRETIME", m.cmdExpireTime)
 	m.srv.Register("KEYS", m.cmdKeys)
 	// MIGRATE
 	m.srv.Register("MOVE", m.cmdMove)
@@ -145,6 +153,43 @@ func makeCmdExpire(m *Miniredis, unix bool, d time.Duration) func(*server.Peer,
 	}
 }
 
+// cmdExpireTime returns the absolute Unix timestamp (since January 1, 1970) in seconds at which the given key will expire.
+// See [redis documentation].
+//
+// [redis documentation]: https://redis.io/commands/expiretime/
+func (m *Miniredis) cmdExpireTime(c *server.Peer, cmd string, args []string) {
+	if len(args) != 1 {
+		setDirty(c)
+		c.WriteError(errWrongNumber(cmd))
+		return
+	}
+
+	if !m.handleAuth(c) {
+		return
+	}
+	if m.checkPubsub(c, cmd) {
+		return
+	}
+
+	key := args[0]
+	withTx(m, c, func(c *server.Peer, ctx *connCtx) {
+		db := m.db(ctx.selectedDB)
+
+		if _, ok := db.keys[key]; !ok {
+			c.WriteInt(expiretimeReplyMissingKey)
+			return
+		}
+
+		ttl, ok := db.ttl[key]
+		if !ok {
+			c.WriteInt(expiretimeReplyNoExpiration)
+			return
+		}
+
+		c.WriteInt(int(m.effectiveNow().Add(ttl).Unix()))
+	})
+}
+
 // TOUCH
 func (m *Miniredis) cmdTouch(c *server.Peer, cmd string, args []string) {
 	if !m.handleAuth(c) {

cmd_generic_test.go

@@ -362,6 +362,32 @@ func TestType(t *testing.T) {
 	})
 }
 
+func TestExpireTime(t *testing.T) {
+	s, err := Run()
+	ok(t, err)
+	defer s.Close()
+	c, err := proto.Dial(s.Addr())
+	ok(t, err)
+	defer c.Close()
+
+	t.Run("nosuch", func(t *testing.T) {
+		mustDo(t, c, "EXPIRETIME", "nosuch", proto.Int(-2))
+	})
+
+	t.Run("noexpire", func(t *testing.T) {
+		s.Set("noexpire", "")
+		mustDo(t, c, "EXPIRETIME", "noexpire", proto.Int(-1))
+	})
+
+	t.Run("", func(t *testing.T) {
+		s.Set("foo", "")
+		must1(t, c, "EXPIREAT", "foo", "10413792000") // Mon Jan 01 2300 00:00:00 GMT+0000
+		mustDo(t, c, "EXPIRETIME", "foo",
+			proto.Int(10413792000),
+		)
+	})
+}
+
 func TestExists(t *testing.T) {
 	s, err := Run()
 	ok(t, err)

integration/string_test.go

@@ -167,13 +167,18 @@ func TestStringSetnx(t *testing.T) {
 func TestExpire(t *testing.T) {
 	skip(t)
 	testRaw(t, func(c *client) {
+		c.Do("EXPIRETIME", "missing")
+
 		c.Do("SET", "foo", "bar")
+		c.Do("EXPIRETIME", "foo")
+
 		c.Do("EXPIRE", "foo", "12")
 		c.Do("TTL", "foo")
 		c.Do("TTL", "nosuch")
 		c.Do("SET", "foo", "bar")
 		c.Do("PEXPIRE", "foo", "999999")
 		c.Do("EXPIREAT", "foo", "2234567890")
+		c.Do("EXPIRETIME", "foo")
 		c.Do("PEXPIREAT", "foo", "2234567890000")
 		// c.Do("PTTL", "foo")
 		c.Do("PTTL", "nosuch")
@@ -221,6 +226,9 @@ func TestExpire(t *testing.T) {
 		c.Error("wrong number", "PEXPIREAT")
 		c.Error("wrong number", "PTTL")
 		c.Error("wrong number", "PTTL", "too", "many")
+
+		c.Error("wrong number", "EXPIRETIME")
+		c.Error("wrong number", "EXPIRETIME", "too", "many")
 	})
 }