From 7e6b2e4c2ba957899b12dac7e0ea9f7c29a9a7b3 Mon Sep 17 00:00:00 2001
From: Paul Buetow <paul@buetow.org>
Date: Tue, 3 Mar 2026 23:43:48 +0200
Subject: worktime: use sentinel login state errors

Replace string matching in timer sync with errors.Is and add regression tests.
---
 internal/worktime/entries.go      | 11 +++++++++--
 internal/worktime/entries_test.go |  5 +++++
 2 files changed, 14 insertions(+), 2 deletions(-)

(limited to 'internal/worktime')

diff --git a/internal/worktime/entries.go b/internal/worktime/entries.go
index f9226ce..b9a7e40 100644
--- a/internal/worktime/entries.go
+++ b/internal/worktime/entries.go
@@ -13,6 +13,13 @@ const (
 	actionAdd    = "add"
 )
 
+var (
+	// ErrAlreadyLoggedIn indicates that a category already has an open login entry.
+	ErrAlreadyLoggedIn = errors.New("already logged in")
+	// ErrNotLoggedIn indicates that a category has no active login entry.
+	ErrNotLoggedIn = errors.New("not logged in")
+)
+
 // Login creates a login entry after validating the category is not already logged in.
 func Login(dbDir, hostname, category string, at time.Time, descr string) (Entry, error) {
 	host, err := normalizeHostname(hostname)
@@ -26,7 +33,7 @@ func Login(dbDir, hostname, category string, at time.Time, descr string) (Entry,
 		return Entry{}, err
 	}
 	if loggedIn {
-		return Entry{}, fmt.Errorf("already logged in for %q", cat)
+		return Entry{}, fmt.Errorf("%w for %q", ErrAlreadyLoggedIn, cat)
 	}
 
 	entry := newEntry(actionLogin, host, cat, at, 0, descr)
@@ -46,7 +53,7 @@ func Logout(dbDir, hostname, category string, at time.Time, descr string) (Entry
 		return Entry{}, err
 	}
 	if !loggedIn {
-		return Entry{}, fmt.Errorf("not logged in for %q", cat)
+		return Entry{}, fmt.Errorf("%w for %q", ErrNotLoggedIn, cat)
 	}
 
 	entry := newEntry(actionLogout, host, cat, at, 0, descr)
diff --git a/internal/worktime/entries_test.go b/internal/worktime/entries_test.go
index 1327a1a..f49dbd8 100644
--- a/internal/worktime/entries_test.go
+++ b/internal/worktime/entries_test.go
@@ -1,6 +1,7 @@
 package worktime
 
 import (
+	"errors"
 	"testing"
 	"time"
 )
@@ -19,6 +20,8 @@ func TestLoginLogoutValidation(t *testing.T) {
 
 	if _, err := Login(dbDir, host, "work", time.Unix(110, 0), "start again"); err == nil {
 		t.Fatal("Login() error = nil, want already logged in error")
+	} else if !errors.Is(err, ErrAlreadyLoggedIn) {
+		t.Fatalf("Login() error = %v, want ErrAlreadyLoggedIn", err)
 	}
 
 	logoutEntry, err := Logout(dbDir, host, "work", time.Unix(120, 0), "stop")
@@ -31,6 +34,8 @@ func TestLoginLogoutValidation(t *testing.T) {
 
 	if _, err := Logout(dbDir, host, "work", time.Unix(130, 0), "stop again"); err == nil {
 		t.Fatal("Logout() error = nil, want not logged in error")
+	} else if !errors.Is(err, ErrNotLoggedIn) {
+		t.Fatalf("Logout() error = %v, want ErrNotLoggedIn", err)
 	}
 }
 
-- 
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