Make more openrouter code re-useable

src/calibre/ai/open_router/backend.py

@@ -2,7 +2,6 @@
 # License: GPLv3 Copyright: 2025, Kovid Goyal <kovid at kovidgoyal.net>
 
 import datetime
-import http
 import json
 import os
 import re
@@ -11,13 +10,12 @@ from collections.abc import Iterable, Iterator
 from functools import lru_cache
 from pprint import pprint
 from typing import Any, NamedTuple
-from urllib.error import HTTPError, URLError
 from urllib.request import Request
 
 from calibre.ai import AICapabilities, ChatMessage, ChatMessageType, ChatResponse, NoFreeModels
 from calibre.ai.open_router import OpenRouterAI
 from calibre.ai.prefs import pref_for_provider
-from calibre.ai.utils import StreamedResponseAccumulator, get_cached_resource, opener
+from calibre.ai.utils import StreamedResponseAccumulator, chat_with_error_handler, get_cached_resource, read_streaming_response
 from calibre.constants import cache_dir
 from polyglot.binary import from_hex_unicode
 
@@ -246,13 +244,7 @@ def text_chat_implementation(messages: Iterable[ChatMessage], use_model: str = '
             data['reasoning']['enabled'] = False
     rq = chat_request(data)
 
-    def read_response(buffer: str) -> Iterator[ChatResponse]:
-        if not buffer.startswith('data: '):
-            return
-        buffer = buffer[6:].rstrip()
-        if buffer == '[DONE]':
-            return
-        data = json.loads(buffer)
+    for data in read_streaming_response(rq):
         for choice in data['choices']:
             d = choice['delta']
             c = d.get('content') or ''
@@ -267,40 +259,9 @@ def text_chat_implementation(messages: Iterable[ChatMessage], use_model: str = '
                 model=data.get('model') or '', has_metadata=True,
             )
 
-    with opener().open(rq) as response:
-        if response.status != http.HTTPStatus.OK:
-            raise Exception(f'OpenRouter API failed with status code: {response.status} and body: {response.read().decode("utf-8", "replace")}')
-        buffer = ''
-        for raw_line in response:
-            line = raw_line.decode('utf-8')
-            if line.strip() == '':
-                if buffer:
-                    yield from read_response(buffer)
-                    buffer = ''
-            else:
-                buffer += line
-        yield from read_response(buffer)
-
 
 def text_chat(messages: Iterable[ChatMessage], use_model: str = '') -> Iterator[ChatResponse]:
-    try:
-        yield from text_chat_implementation(messages, use_model)
-    except HTTPError as e:
-        try:
-            details = e.fp.read().decode()
-        except Exception:
-            details = ''
-        try:
-            error_json = json.loads(details)
-            details = error_json.get('error', {}).get('message', details)
-        except Exception:
-            pass
-        yield ChatResponse(exception=e, error_details=details)
-    except URLError as e:
-        yield ChatResponse(exception=e, error_details=f'Network error: {e.reason}')
-    except Exception as e:
-        import traceback
-        yield ChatResponse(exception=e, error_details=traceback.format_exc())
+    yield from chat_with_error_handler(text_chat_implementation(messages, use_model))
 
 
 def develop(use_model: str = ''):

src/calibre/ai/utils.py

@@ -2,13 +2,16 @@
 # License: GPLv3 Copyright: 2025, Kovid Goyal <kovid at kovidgoyal.net>
 
 import datetime
+import http
+import json
 import os
 import tempfile
-from collections.abc import Iterator
+from collections.abc import Iterable, Iterator
 from contextlib import suppress
 from threading import Thread
 from typing import Any
-from urllib.request import ProxyHandler, build_opener
+from urllib.error import HTTPError, URLError
+from urllib.request import ProxyHandler, Request, build_opener
 
 from calibre import get_proxies
 from calibre.ai import ChatMessage, ChatMessageType, ChatResponse
@@ -63,6 +66,55 @@ def get_cached_resource(path: str, url: str) -> bytes:
     return data
 
 
+def _read_response(buffer: str) -> Iterator[dict[str, Any]]:
+    if not buffer.startswith('data: '):
+        return
+    buffer = buffer[6:].rstrip()
+    if buffer == '[DONE]':
+        return
+    yield json.loads(buffer)
+
+
+def read_streaming_response(rq: Request) -> Iterator[dict[str, Any]]:
+    with opener().open(rq) as response:
+        if response.status != http.HTTPStatus.OK:
+            details = ''
+            with suppress(Exception):
+                details = response.read().decode('utf-8', 'replace')
+            raise Exception(f'Reading from AI provider failed with HTTP response status: {response.status} and body: {details}')
+        buffer = ''
+        for raw_line in response:
+            line = raw_line.decode('utf-8')
+            if line.strip() == '':
+                if buffer:
+                    yield from _read_response(buffer)
+                    buffer = ''
+            else:
+                buffer += line
+        yield from _read_response(buffer)
+
+
+def chat_with_error_handler(it: Iterable[ChatResponse]) -> Iterator[ChatResponse]:
+    try:
+        yield from it
+    except HTTPError as e:
+        try:
+            details = e.fp.read().decode('utf-8', 'replace')
+        except Exception:
+            details = ''
+        try:
+            error_json = json.loads(details)
+            details = error_json.get('error', {}).get('message', details)
+        except Exception:
+            pass
+        yield ChatResponse(exception=e, error_details=details)
+    except URLError as e:
+        yield ChatResponse(exception=e, error_details=f'Network error: {e.reason}')
+    except Exception as e:
+        import traceback
+        yield ChatResponse(exception=e, error_details=traceback.format_exc())
+
+
 class StreamedResponseAccumulator:
 
     def __init__(self):