Refactor error handling

The `ntfyerror` context manager replaces `screenshot_failure` for
handling online banking interaction failures.  It has several
advantages, notably:

* takes a screenshot of the browser page *before* logging out
* cleaner suppression of exceptions, with success tracking
* sends an `ntfy` message, with the screenshot attached

xactfetch.py

@@ -1,4 +1,3 @@
-import contextlib
 import copy
 import datetime
 import json
@@ -15,7 +14,6 @@ from typing import Any, Optional, Type
 
 import requests
 from playwright.sync_api import Page
-from playwright.sync_api import TimeoutError as PlaywrightTimeout
 from playwright.sync_api import sync_playwright
 
 
@@ -35,21 +33,34 @@ ACCOUNTS = {
 
 
 def ntfy(
-    message: str,
+    message: Optional[str] = None,
     topic: str = NTFY_TOPIC,
     title: Optional[str] = None,
     tags: Optional[str] = None,
+    attach: Optional[bytes] = None,
+    filename: Optional[str] = None,
 ) -> None:
+    assert message or attach
     headers = {
         'Title': title or 'xactfetch',
     }
     if tags:
         headers['Tags'] = tags
-    r = requests.post(
-        f'{NTFY_URL}/{topic}',
-        headers=headers,
-        data=message,
-    )
+    url = f'{NTFY_URL}/{topic}'
+    if message:
+        r = requests.post(
+            url,
+            headers=headers,
+            data=message,
+        )
+    else:
+        if filename:
+            headers['Filename'] = filename
+        r = requests.put(
+            url,
+            headers=headers,
+            data=attach,
+        )
     r.raise_for_status()
 
 
@@ -176,8 +187,8 @@ def get_last_transaction_date(key: int, token: str) -> datetime.date:
     return last_date.date() + datetime.timedelta(days=1)
 
 
-def download_chase(page: Page, end_date: datetime.date, token: str) -> None:
-    with Chase(page) as c:
+def download_chase(page: Page, end_date: datetime.date, token: str) -> bool:
+    with Chase(page) as c, ntfyerror('Chase', page) as r:
         c.login()
         key = ACCOUNTS['chase']
         try:
@@ -187,22 +198,23 @@ def download_chase(page: Page, end_date: datetime.date, token: str) -> None:
                 'Skipping Chase account: could not get last transaction: %s',
                 e,
             )
-            return
+            return False
         if start_date >= end_date:
             log.info(
                 'Skipping Chase account: last transaction was %s',
                 start_date,
             )
-            return
+            return True
         csv = c.download_transactions(start_date, end_date)
         log.info('Importing transactions from Chase into Firefly III')
         c.firefly_import(csv, key, token)
+    return r.success
 
 
-def download_commerce(page: Page, end_date: datetime.date, token: str) -> None:
+def download_commerce(page: Page, end_date: datetime.date, token: str) -> bool:
     log.info('Downloading transaction lists from Commerce Bank')
     csvs = []
-    with CommerceBank(page) as c:
+    with CommerceBank(page) as c, ntfyerror('Commerce Bank', page) as r:
         c.login()
         for name, key in ACCOUNTS['commerce'].items():
             try:
@@ -231,6 +243,51 @@ def download_commerce(page: Page, end_date: datetime.date, token: str) -> None:
         log.info('Importing transactions from Commerce Bank into Firefly III')
         for key, csv in csvs:
             c.firefly_import(csv, key, token)
+    return r.success
+
+
+class ntfyerror:
+    def __init__(self, bank: str, page: Page) -> None:
+        self.bank = bank
+        self.page = page
+        self.success = True
+
+    def __enter__(self) -> 'ntfyerror':
+        return self
+
+    def __exit__(
+        self,
+        exc_type: Optional[Type[Exception]],
+        exc_value: Optional[Exception],
+        tb: Optional[TracebackType],
+    ) -> bool:
+        if exc_type and exc_value and tb:
+            self.success = False
+            log.exception(
+                'Swallowed exception:', exc_info=(exc_type, exc_value, tb)
+            )
+            if ss := self.page.screenshot():
+                save_screenshot(ss)
+            ntfy(
+                title=f'xactfetch failed for {self.bank}',
+                tags='warning',
+                attach=ss,
+                filename='screenshot.png',
+            )
+        return True
+
+
+def save_screenshot(screenshot: bytes):
+    now = datetime.datetime.now()
+    filename = now.strftime('screenshot_%Y%m%d%H%M%S.png')
+    log.debug('Saving browser screenshot to %s', filename)
+    try:
+        with open(filename, 'wb') as f:
+            f.write(screenshot)
+    except Exception as e:
+        log.error('Failed to save browser screenshot: %s', e)
+    else:
+        log.info('Browser screenshot saved as %s', filename)
 
 
 class CommerceBank:
@@ -543,26 +600,6 @@ class Chase:
         firefly_import(csv, config, token)
 
 
-@contextlib.contextmanager
-def screenshot_failure(page: Page):
-    try:
-        yield
-    except Exception:
-        log.exception('Failed to download transactions:')
-        now = datetime.datetime.now()
-        filename = now.strftime('screenshot_%Y%m%d%H%M%S.png')
-        log.debug('Saving browser screenshot to %s', filename)
-        try:
-            screenshot = page.screenshot()
-            with open(filename, 'wb') as f:
-                f.write(screenshot)
-        except Exception as e:
-            log.error('Failed to save browser screenshot: %s', e)
-        else:
-            log.error('Browser screenshot saved as %s', filename)
-        raise
-
-
 def main() -> None:
     logging.basicConfig(level=logging.DEBUG)
     if not rbw_unlocked():
@@ -578,23 +615,9 @@ def main() -> None:
         browser = pw.firefox.launch(headless=headless)
         page = browser.new_page()
         failed = False
-        try:
-            with screenshot_failure(page):
-                download_commerce(page, end_date, token)
-        except Exception:
-            ntfy(
-                'Downloading transactions from Commerce Bank failed',
-                tags='warning',
-            )
-            failed = True
-        try:
-            with screenshot_failure(page):
-                download_chase(page, end_date, token)
-        except Exception:
-            ntfy(
-                'Downloading transactions from Chase failed',
-                tags='warning',
-            )
+        if not download_commerce(page, end_date, token):
+           failed = True
+        if not download_chase(page, end_date, token):
             failed = True
     raise SystemExit(1 if failed else 0)