The queue: parking, the operator's order, blocked items (M2.2)

Several work items on the new loop (L1, D4):
- Switching parks the item on the workspace: its work is committed and its
  branch pushed; resuming checks the item's branch back out. Branches of
  open items are never set aside by a fresh workspace.
- Next item: the operator's "do #N next" first, otherwise the oldest.
- Issues with open Gitea dependencies are blocked until they close, checked
  at intake and on every round; status shows blocked items and the line.

Tests: queue unit tests, the property walk over several issues with
dependencies and a new parked_work_safe property (it catches parking
disabled), and an end-to-end test with two issues where B depends on A.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPQ14L3LikyefCMFBqEbKE

nisse-dev/src/nisse_dev/loop/agent.py

@@ -7,11 +7,15 @@ because by the time the worker reaches it a newer one may be up (L3).
 
 One work item at a time is active. An item runs until its driver calls a
 waiting tool; it then waits on the operator, the active pointer is cleared
-(a safe point, L1), and the next ready item runs. Conversation is not work:
+(a safe point, L1), and the next ready item runs: the operator's order when
+given ("do #14 next"), otherwise the oldest. Switching parks the item that was
+on the workspace: its work is committed and its branch pushed (D4). An issue
+with open Gitea dependencies is blocked until they close. Conversation is not work:
 a message is recorded and changes its item's state, but never interrupts a
 run (L1).
 """
 
+import re
 import threading
 import uuid
 from collections.abc import Callable, Iterable
@@ -24,6 +28,7 @@ from nisse_dev.gitea import GiteaClient, GiteaError, Issue
 from nisse_dev.loop.driver import Driver, RunOutcome
 from nisse_dev.loop.items import (
     ANSWER,
+    BLOCKED,
     CLOSED,
     GO_AHEAD,
     MERGE,
@@ -53,6 +58,7 @@ from nisse_dev.worker import Worker
 
 INTAKE_INTERVAL_S = 30.0
 _GO = frozenset({"go", "approve"})
+_NEXT = re.compile(r"(?:do|work on) #?(\d+) (?:next|first|now)")
 
 # Before the go-ahead the driver may look around (read, list, run a command
 # to reproduce a bug) but not change anything (D1); after it, everything.
@@ -235,8 +241,14 @@ class LoopAgent:
                     issue=issue.number,
                 )
                 continue
-            self._open(issue)
+            try:
+                blocked_by = self._gitea.open_dependencies(self._repo, issue.number)
+            except GiteaError as exc:
+                self._oplog.emit("loop.intake_unavailable", cause=str(exc))
+                continue  # taken on the next round
+            self._open(issue, tuple(blocked_by))
         self.watch()
+        self.check_blocked()
         self._schedule()
 
     # -- PR review and merge (D4, D5) -------------------------------------------
@@ -308,6 +320,40 @@ class LoopAgent:
                     loop = replace(loop, wait="", note="")
                 save(self._store, item.id, position, loop, cause="PR update")
 
+    def check_blocked(self) -> None:
+        """L1: an item that hasn't started running yet is blocked while its
+        Gitea dependencies are open, and ready once they have all closed.
+        Only ready and blocked items are checked: the others are mid-work or
+        waiting on the operator, and an agent that finds a blocker mid-work
+        asks before recording it."""
+        for item in self._store.work_items("open"):
+            if item.position not in (READY, BLOCKED):
+                continue
+            loop = loop_of(item)
+            issue = loop.issue
+            try:
+                blocked_by = tuple(self._gitea.open_dependencies(self._repo, issue))
+            except GiteaError as exc:
+                self._oplog.emit("loop.watch_unavailable", cause=str(exc))
+                continue  # as it was, until Gitea answers
+            position = BLOCKED if blocked_by else READY
+            if position == item.position and blocked_by == loop.blocked_by:
+                continue
+            if position == READY:
+                said = f"#{issue} is unblocked: its dependencies have closed."
+            else:
+                said = f"#{issue} is blocked by {', '.join(blocked_by)}."
+            self._fact(item, said)
+            if position != item.position:
+                self._transport.post(said, thread=loop.thread)
+            save(
+                self._store,
+                item.id,
+                position,
+                replace(loop, blocked_by=blocked_by),
+                cause=said,
+            )
+
     def _from_an_operator(self, issue: Issue) -> bool:
         """L11: only an operator's issue, or one an operator assigned, is
         an instruction."""
@@ -319,18 +365,22 @@ class LoopAgent:
             return False
         return who in self._gitea_operators
 
-    def _open(self, issue: Issue) -> None:
+    def _open(self, issue: Issue, blocked_by: tuple[str, ...]) -> None:
         item_id = f"{self._project}-{issue.number}-{uuid.uuid4().hex[:6]}"
         cause = f"assigned {self._repo}#{issue.number}"
+        ahead = len(self._store.work_items("open"))
+        where = f", {ahead} ahead" if ahead else ""
+        if blocked_by:
+            where += f"; blocked by {', '.join(blocked_by)}"
         root = self._transport.post(
-            f"Queued {self._repo}#{issue.number}: {issue.title}"
+            f"Queued {self._repo}#{issue.number}: {issue.title}{where}"
         )
-        loop = Loop(thread=root, issue=issue.number)
+        loop = Loop(thread=root, issue=issue.number, blocked_by=blocked_by)
         self._store.open_work_item(
             item_id,
             title=issue.title,
             scope=self._project,
-            position=READY,
+            position=BLOCKED if blocked_by else READY,
             data={"loop": loop.to_data(), "roles": self._roles},
             cause=cause,
         )
@@ -370,6 +420,16 @@ class LoopAgent:
         item = item_for_thread(self._store, msg.thread) if msg.thread else None
         text = (msg.original or msg.text).strip()
         command = command_form(msg.text)
+        order = _NEXT.fullmatch(command)
+        if order is not None:
+            self._store.transcript(item.id if item else None, "operator").append(
+                UserMessage(text=text, source=f"transport:{msg.sender}")
+            )
+            self._transport.post(
+                self._put_first(int(order.group(1))), thread=msg.thread
+            )
+            self._schedule()
+            return
         if item is None:
             self._store.transcript(None, "operator").append(
                 UserMessage(text=text, source=f"transport:{msg.sender}")
@@ -393,6 +453,12 @@ class LoopAgent:
             item = self._store.work_item(item.id) or item
         if command == "abandon":
             self._close(item, loop, "abandoned", f"abandoned by {msg.sender}")
+        elif item.position == BLOCKED:
+            self._transport.post(
+                f"#{loop.issue} is blocked by {', '.join(loop.blocked_by)}; "
+                "I'll start on it when they close, or when you remove them.",
+                thread=loop.thread,
+            )
         elif item.position == WAITING and loop.wait == GO_AHEAD and command in _GO:
             if about != loop.rev:
                 # L3: a go-ahead is about what was on screen when it arrived.
@@ -421,16 +487,48 @@ class LoopAgent:
             )
         self._schedule()
 
+    def _put_first(self, issue: int) -> str:
+        """The operator's "do #N next" (L1): it runs before every other
+        ready item, the latest such order first. It doesn't unblock."""
+        items = self._store.work_items("open")
+        item = next((i for i in items if loop_of(i).issue == issue), None)
+        if item is None:
+            return f"#{issue} isn't one of my open work items."
+        first = max(loop_of(i).first for i in items) + 1
+        loop = replace(loop_of(item), first=first)
+        save(self._store, item.id, item.position, loop, cause=f"#{issue} put first")
+        self._fact(item, "the operator put this item first in the queue")
+        if item.position == BLOCKED:
+            return (
+                f"#{issue} goes first once it's unblocked "
+                f"(blocked by {', '.join(loop.blocked_by)})."
+            )
+        if item.position == WAITING:
+            return f"#{issue} goes first, but it's waiting for {loop.wait}: {loop.note}"
+        return f"#{issue} is next."
+
+    def _queue(self) -> list[WorkItem]:
+        """Ready items in the order they run (L1): the operator's order
+        first, then the oldest."""
+        items = self._store.work_items("open")  # oldest first
+        ready = [i for i in items if i.position == READY]
+        return sorted(ready, key=lambda i: -loop_of(i).first)
+
     def status(self) -> str:
         items = self._store.work_items("open")
         if not items:
             return f"idle: no open work items. I take issues assigned to me in {self._repo}."
+        queue = [i.id for i in self._queue()]
         lines = []
         for item in items:
             loop = loop_of(item)
             what = item.position
             if item.position == WAITING:
                 what = f"waiting for {loop.wait} ({loop.note or f'rev-{loop.rev}'})"
+            elif item.position == BLOCKED:
+                what = f"blocked by {', '.join(loop.blocked_by)}"
+            elif item.position == READY:
+                what = f"ready, {queue.index(item.id) + 1} of {len(queue)} in line"
             lines.append(f"#{loop.issue} {item.title}: {what}")
         return "\n".join(lines)
 
@@ -441,25 +539,35 @@ class LoopAgent:
         if self._running:
             return
         while True:
-            ready = [i for i in self._store.work_items("open") if i.position == READY]
+            ready = self._queue()
             if not ready:
                 self._store.set_active(None, cause="nothing ready")
                 return
-            self._run(ready[0])  # oldest first (L1)
+            self._run(ready[0])
 
     def _run(self, item: WorkItem) -> None:
         loop = loop_of(item)
         self._store.set_active(item.id, cause="ready")
-        if not loop.prepared and self._milestones is not None:
-            # D3: a fresh workspace when a work item starts.
+        if self._milestones is not None:
+            # Branches of open items, parked or not, are never set aside.
+            keep = tuple(f"{i.id}-" for i in self._store.work_items("open"))
             try:
-                notes = self._milestones.prepare(f"{item.id}-work")
+                if not loop.prepared:
+                    # D3: a fresh workspace when a work item starts.
+                    notes = self._milestones.prepare(f"{item.id}-work", keep=keep)
+                else:
+                    # D4: back to its branch, parking whoever was there.
+                    notes = []
+                    self._milestones.resume(
+                        loop.branch or f"{item.id}-work", keep=keep, mine=f"{item.id}-"
+                    )
             except Exception as exc:  # noqa: BLE001 -- the item waits, not the loop
                 note = f"I couldn't prepare the workspace: {exc}. Reply to retry."
                 self._wait(item, replace(loop, wait=ANSWER, note=note), note)
                 self._store.set_active(None, cause="workspace failed")
                 return
-            self._fact(item, "workspace prepared from the latest default branch")
+            if not loop.prepared:
+                self._fact(item, "workspace prepared from the latest default branch")
             if notes:
                 said = "Set aside from the workspace: " + "; ".join(notes)
                 self._fact(item, said)