diff --git a/slack.go b/slack.go
index 782dc6e..3c9541e 100644
--- a/slack.go
+++ b/slack.go
@@ -12,6 +12,7 @@ import (
 
 	"github.com/slack-go/slack"
 	"github.com/slack-go/slack/slackevents"
+	"github.com/zaiminc/gocat/slackcmd"
 )
 
 // SlackListener is a http.Handler that can handle slack events.
@@ -179,6 +180,11 @@ func (s *SlackListener) handleMessageEvent(ev *slackevents.AppMentionEvent) erro
 		}
 		return nil
 	}
+	if cmd, _ := slackcmd.Parse(ev.Text); cmd != nil {
+		log.Printf("[INFO] %s command is Called", cmd.Name())
+		// TODO run the command and post the result to slack
+		return nil
+	}
 	return nil
 }
 
diff --git a/slackcmd/lock.go b/slackcmd/lock.go
new file mode 100644
index 0000000..1f736f5
--- /dev/null
+++ b/slackcmd/lock.go
@@ -0,0 +1,11 @@
+package slackcmd
+
+type Lock struct {
+	Project string
+	Env     string
+	Reason  string
+}
+
+func (l *Lock) Name() string {
+	return "Lock"
+}
diff --git a/slackcmd/parse.go b/slackcmd/parse.go
new file mode 100644
index 0000000..410ce47
--- /dev/null
+++ b/slackcmd/parse.go
@@ -0,0 +1,57 @@
+package slackcmd
+
+import (
+	"fmt"
+	"regexp"
+	"strings"
+)
+
+var lockUnlockPattern = regexp.MustCompile(`(unlock|lock) ([0-9a-zA-Z-]+) (staging|production|sandbox|stg|pro|prd)\s*(.*)`)
+
+func Parse(text string) (Command, error) {
+	match := findLockUnlock(text)
+	if match == nil {
+		return nil, fmt.Errorf("invalid command %q: valid pattern is 'lock|unlock <project> <env> [for <reason>]", text)
+	}
+
+	var (
+		command = match[0][1]
+		project = match[0][2]
+		env     = match[0][3]
+		reason  = match[0][4]
+	)
+
+	switch command {
+	case "unlock":
+		if reason != "" {
+			return nil, fmt.Errorf("invalid command %q: unlock command does not accept reason", text)
+		}
+
+		return &Unlock{
+			Project: project,
+			Env:     env,
+		}, nil
+	case "lock":
+		if reason == "" {
+			return nil, fmt.Errorf("invalid command %q: lock command requires reason", text)
+		}
+
+		if !strings.HasPrefix(reason, "for ") {
+			return nil, fmt.Errorf("invalid command %q: reason must start with 'for'", text)
+		}
+
+		reason = strings.TrimPrefix(reason, "for ")
+
+		return &Lock{
+			Project: project,
+			Env:     env,
+			Reason:  reason,
+		}, nil
+	default:
+		panic("unreachable")
+	}
+}
+
+func findLockUnlock(text string) [][]string {
+	return lockUnlockPattern.FindAllStringSubmatch(text, -1)
+}
diff --git a/slackcmd/parse_test.go b/slackcmd/parse_test.go
new file mode 100644
index 0000000..9b5f93d
--- /dev/null
+++ b/slackcmd/parse_test.go
@@ -0,0 +1,92 @@
+package slackcmd
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+var (
+	validProjects   = []string{"myproject1", "myproject-2"}
+	invalidProjects = []string{"myproject#3", "myproject_4"}
+	validEnvs       = []string{"staging", "production", "sandbox", "stg", "pro", "prd"}
+	invalidENvs     = []string{"stg1", "pro1", "prd1", "prod", "test"}
+)
+
+func TestParse(t *testing.T) {
+	type test struct {
+		name string
+		text string
+		want Command
+		err  error
+	}
+
+	var tests = []test{}
+
+	for i, p := range validProjects {
+		for j, e := range validEnvs {
+			tests = append(tests, test{
+				name: fmt.Sprintf("lock with valid project %d and env %d", i, j),
+				text: fmt.Sprintf("lock %s %s for deployment of revision a", p, e),
+				want: &Lock{Project: p, Env: e, Reason: "deployment of revision a"},
+			})
+		}
+	}
+
+	for i, p := range invalidProjects {
+		for j, e := range invalidENvs {
+			tests = append(tests, test{
+				name: fmt.Sprintf("lock with invalid project %d and env %d", i, j),
+				text: fmt.Sprintf("lock %s %s for deployment of revision a", p, e),
+				err:  fmt.Errorf("invalid command %q: valid pattern is 'lock|unlock <project> <env> [for <reason>]", fmt.Sprintf("lock %s %s for deployment of revision a", p, e)),
+			})
+		}
+	}
+
+	for i, p := range validProjects {
+		for j, e := range validEnvs {
+			tests = append(tests, test{
+				name: fmt.Sprintf("unlock with valid project %d and env %d", i, j),
+				text: fmt.Sprintf("unlock %s %s", p, e),
+				want: &Unlock{Project: p, Env: e},
+			})
+		}
+	}
+
+	for i, p := range invalidProjects {
+		for j, e := range invalidENvs {
+			tests = append(tests, test{
+				name: fmt.Sprintf("unlock with invalid project %d and env %d", i, j),
+				text: fmt.Sprintf("unlock %s %s", p, e),
+				err:  fmt.Errorf("invalid command %q: valid pattern is 'lock|unlock <project> <env> [for <reason>]", fmt.Sprintf("unlock %s %s", p, e)),
+			})
+		}
+	}
+
+	tests = append(tests, test{
+		name: "unlock has redundant reason",
+		text: "unlock myproject1 production for deployment of revision a",
+		err:  fmt.Errorf("invalid command %q: unlock command does not accept reason", "unlock myproject1 production for deployment of revision a"),
+	})
+
+	tests = append(tests, test{
+		name: "lock missing reason",
+		text: "lock myproject1 production",
+		err:  fmt.Errorf("invalid command %q: lock command requires reason", "lock myproject1 production"),
+	})
+
+	tests = append(tests, test{
+		name: "unknown command",
+		text: "unknown myproject1 production for deployment of revision a",
+		err:  fmt.Errorf("invalid command %q: valid pattern is 'lock|unlock <project> <env> [for <reason>]", "unknown myproject1 production for deployment of revision a"),
+	})
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := Parse(tt.text)
+			assert.Equal(t, tt.want, got, "result")
+			assert.Equal(t, tt.err, err, "error")
+		})
+	}
+}
diff --git a/slackcmd/slackcmd.go b/slackcmd/slackcmd.go
new file mode 100644
index 0000000..9843f17
--- /dev/null
+++ b/slackcmd/slackcmd.go
@@ -0,0 +1,5 @@
+package slackcmd
+
+type Command interface {
+	Name() string
+}
diff --git a/slackcmd/unlock.go b/slackcmd/unlock.go
new file mode 100644
index 0000000..cd62f7b
--- /dev/null
+++ b/slackcmd/unlock.go
@@ -0,0 +1,10 @@
+package slackcmd
+
+type Unlock struct {
+	Project string
+	Env     string
+}
+
+func (u *Unlock) Name() string {
+	return "Unlock"
+}