From dbc4c20bb5d5dd8f7c805a7ac8fcdc40e297edd0 Mon Sep 17 00:00:00 2001
From: David Geary <david@secondbounce.com>
Date: Fri, 11 Oct 2024 17:55:25 +0100
Subject: [PATCH] Fix `LocalStorageAppender` removing too many entries on
 initialization

---
 .../appenders/localstorage-appender.spec.ts   | 30 ++++++++++++++++++-
 .../lib/appenders/localstorage-appender.ts    | 11 +++----
 2 files changed, 35 insertions(+), 6 deletions(-)

diff --git a/projects/log4ngx/src/lib/appenders/localstorage-appender.spec.ts b/projects/log4ngx/src/lib/appenders/localstorage-appender.spec.ts
index 4421a51..9482d6d 100644
--- a/projects/log4ngx/src/lib/appenders/localstorage-appender.spec.ts
+++ b/projects/log4ngx/src/lib/appenders/localstorage-appender.spec.ts
@@ -133,7 +133,35 @@ describe('LocalStorageAppender', () => {
     expect(logEntries).toBe(message1 + appender.logEntryDelimiter + message2);
   });
 
-  it('should remove log entries when max days is exceeded', () => {
+  it('should only remove log entries when > max days exists at initialization', () => {
+    jasmine.clock().withMock(() => {
+      const yesterdayTimestamp: number = Date.now();
+      let appender: LocalStorageAppender = new LocalStorageAppender();
+      appender.initialize({ ...APPENDER_CONFIG,
+                            maxDays: MAX_DAYS + 1
+                          });
+
+      /* Add the max number of entries *prior* to today, so when we reinitialize the appender
+        for today with reduced `maxDays`, we're left with the correct number of entries.
+      */
+      for (let i: number = appender.maxDays - 1; i >= 0; i--) {
+        jasmine.clock().mockDate(new Date(yesterdayTimestamp - (i * MILLISECS_PER_DAY)));
+
+        const message: string = Random.getString(RANDOM_MESSAGE_LENGTH);
+        const loggingEvent: LoggingEvent = new LoggingEvent(Level.debug, '', message);
+        appender.append(loggingEvent);
+      }
+
+      expect(localStorage.length).toBe(appender.maxDays);
+
+      /* Now reduce the max days and reinitialize */
+      appender = new LocalStorageAppender();
+      appender.initialize(APPENDER_CONFIG);
+      expect(localStorage.length).toBe(appender.maxDays);
+    });
+  });
+
+  it('should remove log entries when max days is exceeded on appending new entries', () => {
     jasmine.clock().withMock(() => {
       const todayTimestamp: number = Date.now();
       const appender: LocalStorageAppender = new LocalStorageAppender();
diff --git a/projects/log4ngx/src/lib/appenders/localstorage-appender.ts b/projects/log4ngx/src/lib/appenders/localstorage-appender.ts
index db26bcc..900fd20 100644
--- a/projects/log4ngx/src/lib/appenders/localstorage-appender.ts
+++ b/projects/log4ngx/src/lib/appenders/localstorage-appender.ts
@@ -57,7 +57,7 @@ export class LocalStorageAppender extends Appender {
 
     this._localStorage = this.getLocalStorage();
     if (this._localStorage !== undefined) {
-      this.getCurrentLogEntries(this._localStorage);    /* Really just to initialize _currentKey and _currentLogEntries */
+      this.getCurrentLogEntries(this._localStorage, false);    /* Really just to initialize _currentKey and _currentLogEntries */
     } else {
       // eslint-disable-next-line no-console -- there's not much else we can do
       console.error('LOG4NGX: LocalStorage is not available; calls to log via LocalStorageAppender will be ignored');
@@ -68,7 +68,7 @@ export class LocalStorageAppender extends Appender {
     if (this._localStorage !== undefined) {
       const localStorage: Storage = this._localStorage;
       const message: string = this.renderLoggingEvent(loggingEvent);
-      let currentLogEntries: string = this.getCurrentLogEntries(localStorage);
+      let currentLogEntries: string = this.getCurrentLogEntries(localStorage, true);
 
       if (currentLogEntries.length === 0) {
         currentLogEntries = message;
@@ -120,13 +120,14 @@ export class LocalStorageAppender extends Appender {
   }
 
   /** Gets the current log entries for today, performing any necessary housekeeping on old entries */
-  private getCurrentLogEntries(localStorage: Storage): string {
+  private getCurrentLogEntries(localStorage: Storage, appending: boolean): string {
     const key: string = this._keyPrefix + new Date().setHours(0, 0, 0, 0)
                                                     .toString();
 
     if (key !== this._currentKey) {
-      /* We're about to add a new key, so need to make sure we have `maxDays`-1 entries at most */
-      this.removeOldLogKeys(this._maxDays - 1);
+      /* If we're about to add a new key, so need to make sure we have `maxDays`-1 entries at most */
+      this.removeOldLogKeys(appending ? this._maxDays - 1
+                                      : this._maxDays);
 
       /* We'll reset `_currentLogEntries` just in case there are already log entries for today
         from a previous session.