feat: add buffer max to buffer appender

src/buffer-log-appender.ts

@@ -4,6 +4,7 @@ import { LogLevel, type LogMessage } from './log-message'
 export class BufferLogAppender implements LogAppender {
   public threshold: LogLevel
   public buffer: LogMessage[]
+  public bufferMax?: number
 
   constructor(buffer?: LogMessage[], threshold?: LogLevel) {
     this.buffer = buffer ?? []
@@ -12,7 +13,15 @@ export class BufferLogAppender implements LogAppender {
 
   public appendMessage(msg: LogMessage): void {
     if (this.threshold && msg.level < this.threshold) return
-    else this.buffer.push(msg)
+
+    this.buffer.push(msg)
+
+    if (this.bufferMax !== undefined) {
+      const max = Math.max(0, this.bufferMax)
+      while (this.buffer.length > max) {
+        this.buffer.shift()
+      }
+    }
   }
 
   public clearBuffer(): void {

test/buffer-log-appender.test.ts

@@ -39,6 +39,36 @@ describe("BufferLogAppender", () => {
     expect(appender.buffer[1].msg).toBe("second");
   });
 
+  test("defaults to an unbounded buffer", () => {
+    const appender = new BufferLogAppender();
+
+    appender.appendMessage(makeMsg({ msg: "first" }));
+    appender.appendMessage(makeMsg({ msg: "second" }));
+    appender.appendMessage(makeMsg({ msg: "third" }));
+
+    expect(appender.buffer.length).toBe(3);
+    expect(appender.buffer.map((message) => message.msg)).toEqual([
+      "first",
+      "second",
+      "third",
+    ]);
+  });
+
+  test("trims oldest messages when bufferMax is exceeded", () => {
+    const appender = new BufferLogAppender();
+    appender.bufferMax = 2;
+
+    appender.appendMessage(makeMsg({ msg: "first" }));
+    appender.appendMessage(makeMsg({ msg: "second" }));
+    appender.appendMessage(makeMsg({ msg: "third" }));
+
+    expect(appender.buffer.length).toBe(2);
+    expect(appender.buffer.map((message) => message.msg)).toEqual([
+      "second",
+      "third",
+    ]);
+  });
+
   test("respects threshold", () => {
     const appender = new BufferLogAppender(undefined, LogLevel.WARN);
 

tsconfig.json

@@ -3,6 +3,7 @@
     "module": "commonjs",
     "target": "es2016",
     "declaration": true,
+    "rootDir": "./src",
     "outDir": "./dist",
     "strict": true,
     "skipLibCheck": true