1 files changed, 116 insertions, 0 deletions
diff --git a/deno/mail-relay/log.ts b/deno/mail-relay/log.ts
new file mode 100644
index 0000000..ce27eca
--- /dev/null
+++ b/deno/mail-relay/log.ts
@@ -0,0 +1,116 @@
+import { join } from "@std/path";
+import { toWritableStream, Writer } from "@std/io";
+
+import "./better-js.ts";
+
+export interface LogOptions {
+  time?: Date;
+  error?: boolean;
+}
+
+export type LogFile = Pick<Deno.FsFile, "writable"> & Disposable;
+
+export class Log {
+  #path: string | null = null;
+
+  #wrapWriter(writer: Writer): LogFile {
+    return {
+      writable: toWritableStream(writer, { autoClose: false }),
+      [Symbol.dispose]() {},
+    };
+  }
+
+  #stdoutWrapper: LogFile = this.#wrapWriter(Deno.stdout);
+  #stderrWrapper: LogFile = this.#wrapWriter(Deno.stderr);
+
+  constructor() {
+  }
+
+  get path() {
+    return this.#path;
+  }
+
+  set path(path) {
+    this.#path = path;
+    if (path != null) {
+      Deno.mkdirSync(path, { recursive: true });
+    }
+  }
+
+  infoOrError(isError: boolean, ...args: unknown[]) {
+    this[isError ? "error" : "info"].call(this, ...args);
+  }
+
+  info(...args: unknown[]) {
+    console.log(...args);
+  }
+
+  warn(...args: unknown[]) {
+    console.warn(...args);
+  }
+
+  error(...args: unknown[]) {
+    console.error(...args);
+  }
+
+  #extractOptions(options?: LogOptions): Required<LogOptions> {
+    return {
+      time: options?.time ?? new Date(),
+      error: options?.error ?? false,
+    };
+  }
+
+  async openLog(
+    prefix: string,
+    suffix: string,
+    options?: LogOptions,
+  ): Promise<LogFile> {
+    if (prefix.includes("/")) {
+      throw new Error(`Log file prefix ${prefix} contains '/'.`);
+    }
+    if (suffix.includes("/")) {
+      throw new Error(`Log file suffix ${suffix} contains '/'.`);
+    }
+
+    const { time, error } = this.#extractOptions(options);
+    if (this.#path == null) {
+      return error ? this.#stderrWrapper : this.#stdoutWrapper;
+    }
+
+    const logPath = join(
+      this.#path,
+      `${prefix}-${time.toFileNameString()}-${suffix}`,
+    );
+    return await Deno.open(logPath, {
+      read: false,
+      write: true,
+      append: true,
+      create: true,
+    });
+  }
+
+  async openLogForProgram(
+    program: string,
+    options?: Omit<LogOptions, "error">,
+  ): Promise<{ stdout: LogFile; stderr: LogFile } & Disposable> {
+    const stdout = await this.openLog(program, "stdout", {
+      ...options,
+      error: false,
+    });
+    const stderr = await this.openLog(program, "stderr", {
+      ...options,
+      error: true,
+    });
+    return {
+      stdout,
+      stderr,
+      [Symbol.dispose]: () => {
+        stdout[Symbol.dispose]();
+        stderr[Symbol.dispose]();
+      },
+    };
+  }
+}
+
+const log = new Log();
+export default log;