Add 'pep next' command to find the next available number

README.md

@@ -157,6 +157,20 @@ https://pep-previews--2440.org.readthedocs.build
 
 <!-- [[[end]]] -->
 
+### Find the next available PEP number
+
+Check published PEPs and [open PRs](https://github.com/python/peps/pulls) to find the
+next available PEP number.
+
+<!-- [[[cog run("pep next") ]]] -->
+
+```console
+$ pep next
+Next available PEP: 729
+```
+
+<!-- [[[end]]] -->
+
 ### Open a BPO issue in the browser
 
 Issues from [bugs.python.org](https://bugs.python.org/) have been migrated to

pyproject.toml

@@ -36,6 +36,7 @@ dynamic = [
   "version",
 ]
 dependencies = [
+  "ghapi",
   "platformdirs",
   "python-slugify",
   "thefuzz",

src/pepotron/__init__.py

@@ -6,9 +6,10 @@
 import importlib.metadata
 import logging
 import warnings
+from itertools import pairwise
 from pathlib import Path
 
-from pepotron import _cache
+from . import _cache
 
 __version__ = importlib.metadata.version(__name__)
 
@@ -70,22 +71,71 @@ def _download_peps_json(json_url: str = BASE_URL + JSON_PATH) -> Path:
     return cache_file
 
 
-def word_search(search: str | None) -> int:
+def _get_peps() -> _cache.PepData:
     import json
 
     peps_file = _download_peps_json()
 
+    with open(peps_file) as f:
+        peps: _cache.PepData = json.load(f)
+
+    return peps
+
+
+def _get_published_peps() -> set[int]:
+    peps = _get_peps()
+    numbers = {int(number) for number, details in peps.items()}
+    return numbers
+
+
+def _next_available_pep() -> int:
+    published = _get_published_peps()
+    proposed = _get_pr_peps()
+    combined = published | proposed
+    numbers = sorted(combined)
+
+    start = 400
+    next_pep = -1
+    for x, y in pairwise(numbers):
+        if x < start:
+            continue
+        if x + 1 != y:
+            next_pep = x + 1
+            break
+
+    return next_pep
+
+
+def _get_pr_peps() -> set[int]:
+    import re
+
+    from ghapi.all import GhApi  # type: ignore
+
+    api = GhApi(owner="python", repo="peps", authenticate=False)
+    prs = api.pulls.list()
+
+    pr_title_regex = re.compile(r"^PEP (\d+): .*")
+
+    numbers = set()
+    for pr in prs:
+        if match := re.search(pr_title_regex, pr.title):
+            number = match[1]
+            numbers.add(int(number))
+
+    return numbers
+
+
+def word_search(search: str | None) -> int:
     with warnings.catch_warnings():
         warnings.simplefilter("ignore", category=UserWarning)
         from thefuzz import process  # type: ignore
 
-    with open(peps_file) as f:
-        peps = json.load(f)
+    peps = _get_peps()
 
     # We only want to search titles
-    peps = ((number, details["title"]) for number, details in peps.items())
+    numbers_titles = ((number, details["title"]) for number, details in peps.items())
 
-    result: list[tuple[tuple[str, str], int]] = process.extract(search, peps)
+    result: list[tuple[tuple[str, str], int]] = process.extract(search, numbers_titles)
     print("Score\tResult")
     for match, score in result:
         print(f"{score}\tPEP {match[0]}: {match[1]}")
@@ -111,6 +161,9 @@ def pep_url(search: str | None, base_url: str = BASE_URL, pr: int | None = None)
     if search.lower() in TOPICS:
         return result + f"/topic/{search}/"
 
+    if search.lower() == "next":
+        return f"Next available PEP: {_next_available_pep()}"
+
     try:
         # pep 8
         number = int(search)

src/pepotron/cli.py

@@ -7,7 +7,7 @@
 import atexit
 import logging
 
-from pepotron import BASE_URL, __version__, _cache, open_bpo, open_pep
+from . import BASE_URL, __version__, _cache, open_bpo, open_pep
 
 atexit.register(_cache.clear)