feat: preview mobile review diffs (#123)

src/gitea_proxy.py

@@ -1,10 +1,13 @@
 import os
+import shlex
 from typing import Any
 
 import httpx
 
 GITEA_URL = os.getenv("GITEA_URL", "http://127.0.0.1:3000").rstrip("/")
 GITEA_TOKEN = os.getenv("GITEA_TOKEN", "")
+REVIEW_DIFF_MAX_BYTES = 64 * 1024
+REVIEW_DIFF_MAX_LINES = 400
 
 
 def _auth() -> dict[str, str]:
@@ -21,6 +24,66 @@ async def fetch(path: str) -> Any:
         return r.json()
 
 
+async def fetch_text(path: str, max_bytes: int) -> tuple[str, bool]:
+    chunks: list[bytes] = []
+    size = 0
+    truncated = False
+    async with httpx.AsyncClient(base_url=GITEA_URL, timeout=10) as client:
+        async with client.stream(
+            "GET", f"/api/v1/{path}", headers={**_auth(), "Accept": "text/plain"}
+        ) as response:
+            response.raise_for_status()
+            async for chunk in response.aiter_bytes():
+                remaining = max_bytes - size
+                if len(chunk) > remaining:
+                    chunks.append(chunk[:remaining])
+                    truncated = True
+                    break
+                chunks.append(chunk)
+                size += len(chunk)
+    return b"".join(chunks).decode("utf-8", errors="replace"), truncated
+
+
+def _diff_previews(diff: str, stream_truncated: bool) -> dict[str, dict]:
+    previews: dict[str, dict] = {}
+    current: dict | None = None
+    in_hunk = False
+    remaining = REVIEW_DIFF_MAX_LINES
+    for line in diff.splitlines():
+        if line.startswith("diff --git "):
+            try:
+                target = shlex.split(line)[3]
+                filename = target[2:] if target.startswith("b/") else target
+            except (IndexError, ValueError):
+                current = None
+                continue
+            current = {
+                "diff_lines": [],
+                "diff_available": False,
+                "diff_binary": False,
+                "diff_truncated": stream_truncated,
+            }
+            previews[filename] = current
+            in_hunk = False
+            continue
+        if current is None:
+            continue
+        if line.startswith("Binary files ") or line == "GIT binary patch":
+            current["diff_binary"] = True
+            in_hunk = False
+            continue
+        if line.startswith("@@"):
+            in_hunk = True
+        if in_hunk and not line.startswith("\\ No newline at end of file"):
+            if remaining:
+                current["diff_lines"].append(line)
+                current["diff_available"] = True
+                remaining -= 1
+            else:
+                current["diff_truncated"] = True
+    return previews
+
+
 async def current_user() -> dict:
     return await fetch("user")
 
@@ -79,6 +142,10 @@ async def pull_review_detail(repository: str, number: int) -> dict:
     sha = sha_value if isinstance(sha_value, str) else ""
     status = await fetch(f"repos/{repository}/commits/{sha}/status")
     reviews = await fetch(f"{base}/reviews")
+    diff, diff_truncated = await fetch_text(
+        f"repos/{repository}/pulls/{number}.diff", REVIEW_DIFF_MAX_BYTES
+    )
+    previews = _diff_previews(diff, diff_truncated)
     user_value = pull.get("user")
     user: dict = user_value if isinstance(user_value, dict) else {}
     normalized_files = [
@@ -87,6 +154,15 @@ async def pull_review_detail(repository: str, number: int) -> dict:
             "status": file.get("status") or "changed",
             "additions": file.get("additions") or 0,
             "deletions": file.get("deletions") or 0,
+            **previews.get(
+                file["filename"],
+                {
+                    "diff_lines": [],
+                    "diff_available": False,
+                    "diff_binary": False,
+                    "diff_truncated": diff_truncated,
+                },
+            ),
         }
         for file in (files if isinstance(files, list) else [])[:100]
         if isinstance(file, dict) and isinstance(file.get("filename"), str)