refactor: extract Watchable<T> base class for SDK effect wrappers

Eliminates boilerplate across 7 wrapper classes (GetContainerIp,
GetHostInfo, GetOutboundGateway, GetServiceManifest, GetSslCertificate,
GetStatus, GetSystemSmtp) by moving shared const/once/watch/onChange/
waitFor logic into an abstract Watchable<T> base class.

sdk/base/lib/util/GetSystemSmtp.ts

@@ -1,111 +1,15 @@
 import { Effects } from '../Effects'
 import * as T from '../types'
-import { AbortedError } from './AbortedError'
-import { DropGenerator, DropPromise } from './Drop'
+import { Watchable } from './Watchable'
 
-export class GetSystemSmtp {
-  constructor(readonly effects: Effects) {}
+export class GetSystemSmtp extends Watchable<T.SmtpValue | null> {
+  protected readonly label = 'GetSystemSmtp'
 
-  /**
-   * Returns the system SMTP credentials. Reruns the context from which it has been called if the underlying value changes
-   */
-  const() {
-    return this.effects.getSystemSmtp({
-      callback:
-        this.effects.constRetry &&
-        (() => this.effects.constRetry && this.effects.constRetry()),
-    })
-  }
-  /**
-   * Returns the system SMTP credentials. Does nothing if the credentials change
-   */
-  once() {
-    return this.effects.getSystemSmtp({})
+  constructor(effects: Effects) {
+    super(effects)
   }
 
-  private async *watchGen(abort?: AbortSignal) {
-    const resolveCell = { resolve: () => {} }
-    this.effects.onLeaveContext(() => {
-      resolveCell.resolve()
-    })
-    abort?.addEventListener('abort', () => resolveCell.resolve())
-    while (this.effects.isInContext && !abort?.aborted) {
-      let callback: () => void = () => {}
-      const waitForNext = new Promise<void>((resolve) => {
-        callback = resolve
-        resolveCell.resolve = resolve
-      })
-      yield await this.effects.getSystemSmtp({
-        callback: () => callback(),
-      })
-      await waitForNext
-    }
-    return new Promise<never>((_, rej) => rej(new AbortedError()))
-  }
-
-  /**
-   * Watches the system SMTP credentials. Returns an async iterator that yields whenever the value changes
-   */
-  watch(
-    abort?: AbortSignal,
-  ): AsyncGenerator<T.SmtpValue | null, never, unknown> {
-    const ctrl = new AbortController()
-    abort?.addEventListener('abort', () => ctrl.abort())
-    return DropGenerator.of(this.watchGen(ctrl.signal), () => ctrl.abort())
-  }
-
-  /**
-   * Watches the system SMTP credentials. Takes a custom callback function to run whenever the credentials change
-   */
-  onChange(
-    callback: (
-      value: T.SmtpValue | null,
-      error?: Error,
-    ) => { cancel: boolean } | Promise<{ cancel: boolean }>,
-  ) {
-    ;(async () => {
-      const ctrl = new AbortController()
-      for await (const value of this.watch(ctrl.signal)) {
-        try {
-          const res = await callback(value)
-          if (res.cancel) {
-            ctrl.abort()
-            break
-          }
-        } catch (e) {
-          console.error(
-            'callback function threw an error @ GetSystemSmtp.onChange',
-            e,
-          )
-        }
-      }
-    })()
-      .catch((e) => callback(null, e))
-      .catch((e) =>
-        console.error(
-          'callback function threw an error @ GetSystemSmtp.onChange',
-          e,
-        ),
-      )
-  }
-
-  /**
-   * Watches the system SMTP credentials. Returns when the predicate is true
-   */
-  waitFor(
-    pred: (value: T.SmtpValue | null) => boolean,
-  ): Promise<T.SmtpValue | null> {
-    const ctrl = new AbortController()
-    return DropPromise.of(
-      Promise.resolve().then(async () => {
-        for await (const next of this.watchGen(ctrl.signal)) {
-          if (pred(next)) {
-            return next
-          }
-        }
-        return null
-      }),
-      () => ctrl.abort(),
-    )
+  protected call(callback?: () => void) {
+    return this.effects.getSystemSmtp({ callback })
   }
 }