"""GitHub plumbing: opening PRs from agent worktree branches, requesting
Copilot reviews, and polling PR state for cards sitting in review/.

All of it is mechanical `git` + `gh` — no Claude involvement. The PR url is
written into the task file (`**PR:** <url>`), keeping the file the single
source of truth; only the volatile review/check state lives in memory.

With replicas watching one truth, *who* opens a PR matters: the trigger is
the actor's board (watch.py refuses to fire on a move a pull applied) and
the `**PR:**` line is the backstop behind it — carried by the file, so a
second attempt from anywhere finds the PR already there, and a `gh pr
create` that races anyway adopts the open PR instead of erroring. Polling
is read-only and every board does it.
"""

from __future__ import annotations

import json
import re
import shutil
import subprocess
import threading
import time
from pathlib import Path

import config
import drive as drive_mod
import reports
import state
from taskfiles import STATUS_RE, commit_edit, find_stage_of, move_task, read_task

PR_STATE: dict[str, dict] = {}   # filename -> {verdict, detail, url, ts}
_OPENING: set[str] = set()       # filenames with a PR-open in flight


def _run(cmd: list[str], cwd: Path | None = None, timeout: int = 60) -> subprocess.CompletedProcess:
    return subprocess.run(cmd, cwd=str(cwd or config.REPO),
                          capture_output=True, text=True, timeout=timeout)


def remote() -> str | None:
    if config.GIT_REMOTE:
        return config.GIT_REMOTE
    result = _run(["git", "remote"])
    names = result.stdout.split()
    return names[0] if names else None


def gh_available() -> bool:
    return shutil.which(config.GH_BIN) is not None


def _branch_exists(branch: str) -> bool:
    return _run(["git", "rev-parse", "--verify", "--quiet", branch]).returncode == 0


def _write_pr_line(filename: str, url: str) -> None:
    """The url joins the header — and in team mode commits itself, so the
    gate that stops a second board opening a second PR travels to the other
    boards rather than sitting in one working tree (where it would also
    stall sync, which never runs over uncommitted changes)."""
    stage = find_stage_of(filename)
    if not stage:
        return
    path = config.TASKS / stage / filename
    text = path.read_text(encoding="utf-8")
    if re.search(r"^\*\*PR:\*\*", text, re.MULTILINE):
        return
    if STATUS_RE.search(text):
        text = STATUS_RE.sub(lambda m: f"{m.group(0)}\n**PR:** {url}", text, count=1)
    else:
        text = f"**PR:** {url}\n\n" + text
    path.write_text(text, encoding="utf-8")
    commit_edit(filename, stage, "PR opened")


class _Quiet(ValueError):
    """A reason not worth the ticker: no branch, or a PR already open. The
    automatic path swallows these; the explicit action still shows them."""


def maybe_open_pr(filename: str) -> None:
    """Card entered review/ on *this* board — open a PR for its branch if
    one can be opened.

    Quiet when there is simply no branch (hand-written tasks) or a PR is
    already on the card; loud in the ticker when a PR *should* be possible
    but something stands in the way.
    """
    if filename in _OPENING:
        return
    _OPENING.add(filename)
    try:
        _open_pr(filename)
    except _Quiet:
        pass
    except ValueError as exc:
        state.record_board_event({
            "kind": "agent", "actor": "board", "file": filename,
            "summary": str(exc)})
    finally:
        _OPENING.discard(filename)


def open_pr_now(filename: str) -> str:
    """The explicit action behind ↑ open PR: no board ever completes a
    half-done side effect on its own (the actor's board may have died
    between moving the card and opening the PR), so a person asks for it —
    and hears the reason when it cannot happen."""
    if filename in _OPENING:
        raise ValueError(f"a PR for {filename} is already being opened")
    _OPENING.add(filename)
    try:
        return _open_pr(filename)
    finally:
        _OPENING.discard(filename)


def _open_pr(filename: str) -> str:
    branch = f"task/{filename[:-3]}"
    if not _branch_exists(branch):
        # nothing to publish — a hand-moved card without agent work
        raise _Quiet(f"{filename} has no {branch} branch — nothing to open a PR from")
    stage = find_stage_of(filename)
    if stage != "review":
        raise _Quiet(f"{filename} is not in review/ — PRs open from there")
    task = read_task(config.TASKS / stage / filename, stage)
    if task.get("pr"):
        raise _Quiet(f"{filename} already has a PR: {task['pr']}")

    rname = remote()
    if rname is None or not gh_available():
        raise ValueError(f"no PR for {filename}: " +
                         ("no git remote configured" if rname is None
                          else "gh is not installed"))

    # The PR's diff is computed against the remote main — refuse to open one
    # that would drag unpushed main commits along with it.
    _run(["git", "fetch", rname, "main"], timeout=120)
    ahead = _run(["git", "rev-list", "--count", f"{rname}/main..main"]).stdout.strip()
    if ahead.isdigit() and int(ahead) > 0:
        raise ValueError(f"won't open a PR for {filename}: main is {ahead} commits "
                         f"ahead of {rname} — push main first, then move the card again")

    push = _run(["git", "push", "-u", rname, branch], timeout=180)
    if push.returncode != 0:
        raise ValueError(f"push failed for {branch}: {push.stderr.strip()[:140]}")

    body = (f"Task: `{filename}` — tracked in `.task-manager/tasks/review/`.\n\n"
            f"Opened by the board when the card moved to review.")
    summary = _agent_report(filename)
    if summary:
        body += f"\n\n## Agent summary\n\n{summary}"
    result = _run([config.GH_BIN, "pr", "create", "--head", branch, "--base", "main",
                   "--title", task["title"], "--body", body], timeout=120)
    if result.returncode != 0:
        # The rare double-fire: two attempts crossed and GitHub already has
        # the PR. Adopt it — one PR still exists, and the card learns its
        # url. Anything else is a real failure.
        adopted = _existing_pr(branch) if _already_exists(result) else ""
        if not adopted:
            raise ValueError(f"PR creation failed for {branch}: "
                             f"{result.stderr.strip()[:140]}")
        _write_pr_line(filename, adopted)
        state.record_board_event({
            "kind": "agent", "actor": "board", "file": filename,
            "summary": f"{filename}'s PR was already open — adopted it: {adopted}"})
        state.broadcast({"type": "board"})
        _poll_pr(filename, adopted)
        return adopted
    url = next((l.strip() for l in result.stdout.splitlines() if "/pull/" in l), result.stdout.strip())
    _write_pr_line(filename, url)
    state.record_board_event({
        "kind": "agent", "actor": "board", "file": filename,
        "summary": f"PR opened for {filename}: {url}"})
    state.broadcast({"type": "board"})
    _poll_pr(filename, url)  # first CI/review snapshot without waiting a cycle
    return url


def _already_exists(result: subprocess.CompletedProcess) -> bool:
    return "already exists" in (result.stderr + result.stdout).lower()


def _existing_pr(branch: str) -> str:
    """The url of the PR already open for this branch, if gh can name it."""
    found = _run([config.GH_BIN, "pr", "view", branch, "--json", "url",
                  "--jq", ".url"], timeout=60)
    if found.returncode != 0:
        return ""
    return next((l.strip() for l in found.stdout.splitlines() if "/pull/" in l), "")


def _agent_report(filename: str) -> str:
    """The work agent's closing report, clipped exactly as the task file
    clips it (reports.report — head first, one cap for both). The PR and
    the record must never tell different stories about the same run."""
    with state.LOCK:
        records = [r for r in state.AGENTS.values()
                   if r["task"] == filename and r.get("mode") == "work"]
    if not records:
        return ""
    latest = max(records, key=lambda r: r["started"])
    try:
        text = Path(latest["log"]).read_text(encoding="utf-8", errors="replace")
    except OSError:
        return ""
    return reports.report(text, log_path=latest.get("log"))


def request_copilot(filename: str) -> str:
    """Ask GitHub Copilot to review the task's PR. Works iff Copilot code
    review is enabled for the repo — otherwise gh returns an error we relay."""
    stage = find_stage_of(filename)
    if stage is None:
        raise ValueError(f"{filename} is not on the board")
    task = read_task(config.TASKS / stage / filename, stage)
    url = task.get("pr")
    if not url:
        raise ValueError(f"{filename} has no PR yet")
    number = url.rstrip("/").rsplit("/", 1)[-1]
    result = _run([config.GH_BIN, "api", "-X", "POST",
                   f"repos/{{owner}}/{{repo}}/pulls/{number}/requested_reviewers",
                   "-f", "reviewers[]=copilot-pull-request-reviewer[bot]"], timeout=60)
    if result.returncode != 0:
        raise ValueError(f"Copilot said no: {result.stderr.strip()[:160]}")
    entry = PR_STATE.setdefault(filename, {"verdict": "pending", "ci": None,
                                           "url": url, "detail": "", "ts": 0})
    entry["copilot"] = "asked"
    state.record_board_event({
        "kind": "agent", "actor": "board", "file": filename,
        "summary": f"Copilot review requested on {filename}'s PR"})
    state.broadcast({"type": "board"})
    return url


def _check_state(check: dict) -> str:
    """One check-run or status-context → pass | fail | running."""
    conclusion = (check.get("conclusion") or check.get("state") or "").upper()
    status = (check.get("status") or "").upper()
    if conclusion in ("FAILURE", "TIMED_OUT", "CANCELLED", "ERROR", "STARTUP_FAILURE"):
        return "fail"
    if conclusion in ("SUCCESS", "NEUTRAL", "SKIPPED"):
        return "pass"
    if status in ("IN_PROGRESS", "QUEUED", "PENDING", "WAITING", "REQUESTED"):
        return "running"
    return "running"


def _is_copilot(login) -> bool:
    return "copilot" in str(login or "").lower()


def _conflict_state(data: dict, prev: dict) -> bool | None:
    """GitHub computes mergeability lazily: UNKNOWN means "not computed
    yet", never "fine" — keep the previous reading so the chip does not
    flap while GitHub thinks."""
    mergeable = str(data.get("mergeable") or "").upper()
    if mergeable == "CONFLICTING":
        return True
    if mergeable == "MERGEABLE":
        return False
    return prev.get("conflicts")


def _fold(data: dict, prev: dict) -> dict:
    """One gh pr-view payload + the previous snapshot → the new snapshot.
    Pure fold: fetching, events and broadcasts stay in _poll_pr."""
    reviews = data.get("reviews") or []
    checks = data.get("statusCheckRollup") or []
    changes = any(r.get("state") == "CHANGES_REQUESTED" for r in reviews)
    approved = any(r.get("state") == "APPROVED" for r in reviews)

    # Copilot: asked is a pending entry in reviewRequests; done is a review
    # authored by the copilot bot — the request entry disappears once it lands.
    cop_reviews = [r for r in reviews
                   if _is_copilot((r.get("author") or {}).get("login"))]
    cop_requested = any(
        _is_copilot(rr.get("login") or rr.get("slug") or rr.get("name"))
        for rr in (data.get("reviewRequests") or []))
    if cop_reviews:
        copilot = {"APPROVED": "approved", "CHANGES_REQUESTED": "changes"}.get(
            cop_reviews[-1].get("state"), "commented")
    elif cop_requested:
        copilot = "asked"
    else:
        copilot = "asked" if prev.get("copilot") == "asked" else None

    states = [_check_state(c) for c in checks]
    ci = ("fail" if "fail" in states
          else "running" if "running" in states
          else "pass" if states else None)

    conflicts = _conflict_state(data, prev)

    # A conflict is changes-needed-by-you, not a CI failure: it beats any
    # approval but leaves the CI chip telling its own story.
    verdict = ("red" if (changes or ci == "fail" or conflicts)
               else "green" if approved else "pending")
    detail_bits = []
    if reviews:
        detail_bits.append(f"{len(reviews)} review{'s' if len(reviews) > 1 else ''}")
    if ci:
        detail_bits.append({"fail": "checks failing", "running": "checks running",
                            "pass": "checks ok"}[ci])
    if conflicts:
        detail_bits.append("conflicts with main")
    if copilot:
        detail_bits.append("copilot " + {"asked": "asked", "approved": "approved",
                                         "changes": "asked for changes",
                                         "commented": "commented"}[copilot])
    return {"verdict": verdict, "ci": ci, "copilot": copilot,
            "conflicts": conflicts, "detail": " · ".join(detail_bits)}


def _poll_pr(filename: str, url: str) -> None:
    number = url.rstrip("/").rsplit("/", 1)[-1]
    result = _run([config.GH_BIN, "pr", "view", number,
                   "--json", "reviews,reviewRequests,statusCheckRollup,state,mergeable"],
                  timeout=60)
    if result.returncode != 0:
        return
    try:
        data = json.loads(result.stdout)
    except json.JSONDecodeError:
        return
    prev = PR_STATE.get(filename, {})
    entry = _fold(data, prev)
    entry.update({"url": url, "ts": time.time()})
    PR_STATE[filename] = entry
    verdict, ci, copilot = entry["verdict"], entry["ci"], entry["copilot"]
    if prev.get("copilot") in (None, "asked") and copilot in ("approved", "changes", "commented"):
        word = {"approved": "approved it", "changes": "asked for changes",
                "commented": "commented"}[copilot]
        state.record_board_event({
            "kind": "agent", "actor": "board", "file": filename,
            "summary": f"Copilot reviewed {filename}'s PR and {word}"})
        state.broadcast({"type": "board"})
    if bool(prev.get("conflicts")) != bool(entry["conflicts"]):
        state.record_board_event({
            "kind": "agent", "actor": "board", "file": filename,
            "summary": (f"{filename}'s PR conflicts with main — ↻ act on PR "
                        f"can attempt the resolution" if entry["conflicts"]
                        else f"{filename}'s PR no longer conflicts with main")})
        state.broadcast({"type": "board"})
    elif prev.get("verdict") != verdict and verdict != "pending":
        word = "approved" if verdict == "green" else "changes asked"
        state.record_board_event({
            "kind": "agent", "actor": "board", "file": filename,
            "summary": f"GitHub on {filename}'s PR: {word}"})
        state.broadcast({"type": "board"})
    elif prev.get("ci") != ci and ci in ("fail", "pass") and prev.get("ci") is not None:
        state.record_board_event({
            "kind": "agent", "actor": "board", "file": filename,
            "summary": f"CI on {filename}'s PR: "
                       + ("all checks pass" if ci == "pass" else "checks failing")})
        state.broadcast({"type": "board"})


def poller() -> None:
    """Watch PRs of cards sitting in review/. Silent when there are none."""
    while True:
        time.sleep(config.PR_POLL_INTERVAL)
        if not gh_available():
            continue
        directory = config.TASKS / "review"
        if not directory.is_dir():
            continue
        try:
            for path in directory.glob("*.md"):
                task = read_task(path, "review")
                if task.get("pr"):
                    _poll_pr(task["file"], task["pr"])
        except OSError:
            continue


def public_state() -> dict:
    return {f: {k: v.get(k) for k in ("verdict", "ci", "copilot", "conflicts", "detail", "url")}
            for f, v in PR_STATE.items()}


def open_pr_async(filename: str) -> None:
    threading.Thread(target=maybe_open_pr, args=(filename,), daemon=True).start()


def complete_task(filename: str, stage: str) -> dict:
    """The user chose "merge & clean up" on a move to done: park the drive
    if it is this task's, merge the branch, remove the worktree and
    branches, then move the card. Every step narrates; a conflict aborts
    cleanly and the card stays.

    Where the merge happens depends on team mode. Single-player merges into
    the local main and pushes it, exactly as it always did; with
    `BOARD_SYNC` on the merge is made on origin through `gh pr merge`, so
    local main only ever fast-forwards to it — the discipline the whole
    sync design rests on.

    None of it is quick, and all of it is destructive, so the card is
    claimed before the first step and given back in a `finally` after the
    last one. The claim is what the card wears while this runs and what
    refuses a second request; see `state.claim_completing`.
    """
    if stage not in config.STAGE_DIRS or stage == "done":
        raise ValueError("complete runs on a live-stage card")
    if not (config.TASKS / stage / filename).is_file():
        raise ValueError(f"{filename} is not in {stage}/ — refresh the board")

    if not state.claim_completing(filename, "merging and cleaning up…"):
        raise ValueError(f"{filename} is already being completed — the card "
                         f"is showing each step; nothing was started twice")
    try:
        return _complete(filename, stage)
    finally:
        # every exit: merged, conflicted, on the wrong branch, or crashed
        state.release_completing(filename)


def _complete(filename: str, stage: str) -> dict:
    """The steps themselves, run under the claim complete_task holds."""
    stem = filename[:-3]
    branch = f"task/{stem}"

    # 1. the app must not keep running code that is about to be merged away
    d = drive_mod.DRIVE
    if d and d.get("task") == filename and d.get("status") in ("starting", "up"):
        drive_mod.stop()
        for _ in range(40):
            if not drive_mod._alive(d):
                break
            time.sleep(0.5)

    merged = False
    if _branch_exists(branch):
        if config.SYNC:
            _merge_on_origin(filename, stage, branch)
        else:
            _merge_locally(filename, branch)
        merged = True

        worktree = config.WORKTREES / stem
        if worktree.exists():
            _run(["git", "worktree", "remove", "--force", str(worktree)])
        # -D under sync: main here has not merged the branch yet (origin
        # did), so the safe delete would refuse something already landed.
        _run(["git", "branch", "-D" if config.SYNC else "-d", branch])
        PR_STATE.pop(filename, None)
        state.record_board_event({
            "kind": "agent", "actor": "board", "file": filename,
            "summary": f"cleaned up: worktree and local branch for {stem} removed"})

    move_task(filename, stage, "done", actor="you")
    state.broadcast({"type": "board"})
    return {"merged": merged}


def _merge_locally(filename: str, branch: str) -> None:
    """Single-player: merge into the checkout's own main and push it."""
    current = _run(["git", "branch", "--show-current"]).stdout.strip()
    if current != "main":
        raise ValueError(f"the repo is on '{current}', not main — switch first")
    result = _run(["git", "merge", "--no-edit", branch], timeout=120)
    if result.returncode != 0:
        _run(["git", "merge", "--abort"])
        detail = (result.stdout.strip() or result.stderr.strip())[-160:]
        raise ValueError(f"merge conflict — resolve by hand ({detail})")
    state.record_board_event({
        "kind": "agent", "actor": "board", "file": filename,
        "summary": f"merged {branch} into main"})

    rname = remote()
    if rname:
        push = _run(["git", "push", rname, "main"], timeout=180)
        if push.returncode != 0:
            state.record_board_event({
                "kind": "agent", "actor": "board", "file": filename,
                "summary": f"merged locally but the push failed — push main "
                           f"yourself ({push.stderr.strip()[:100]})"})
        else:
            _run(["git", "push", rname, "--delete", branch], timeout=60)
            state.record_board_event({
                "kind": "agent", "actor": "board", "file": filename,
                "summary": f"pushed main (PR marked merged) and deleted {branch} on {rname}"})


def _merge_on_origin(filename: str, stage: str, branch: str) -> None:
    """Team mode: the merge commit is made by GitHub, on origin.

    Replicas keep converging only while local main advances by
    fast-forward, so the board never creates a merge commit of its own —
    it asks origin for one and lets the sync beat deliver it. Needs merge
    rights on the repo for whoever clicks, which the local path did not.
    """
    task = read_task(config.TASKS / stage / filename, stage)
    url = task.get("pr")
    if not url:
        raise ValueError(
            f"{filename} has no PR, and with BOARD_SYNC on the merge is made on "
            f"origin — open a PR for {branch} first (↑ open PR on the card)")
    if not gh_available():
        raise ValueError("gh is not installed — with BOARD_SYNC on the merge runs on origin")
    number = url.rstrip("/").rsplit("/", 1)[-1]
    result = _run([config.GH_BIN, "pr", "merge", number, "--merge"], timeout=180)
    if result.returncode != 0:
        detail = (result.stderr.strip() or result.stdout.strip())[-160:]
        raise ValueError(f"origin would not merge the PR — resolve it on GitHub ({detail})")
    state.record_board_event({
        "kind": "agent", "actor": "board", "file": filename,
        "summary": f"merged {filename}'s PR on origin — local main fast-forwards "
                   f"on the next sync beat"})
    rname = remote()
    if rname:
        _run(["git", "push", rname, "--delete", branch], timeout=60)


def task_branches() -> list[str]:
    """Stems of all task/* branches — the UI uses this to say honestly
    whether a review card has work attached."""
    result = _run(["git", "for-each-ref", "--format=%(refname:short)",
                   "refs/heads/task/"])
    return [ref[len("task/"):] for ref in result.stdout.split() if ref.startswith("task/")]


def reconcile() -> None:
    """Catch up on moves the watcher never saw (board was down): any card
    already sitting in review/ with a branch but no PR gets its PR opened
    now. Runs once at startup.

    Not in team mode. A replica cannot tell whose move it missed, so every
    board starting up would race to open the same PR — and the card that
    needs one wears the explicit ↑ open PR action instead, which is a
    person deciding rather than N boards guessing."""
    if config.SYNC:
        return
    time.sleep(3)  # let the server settle first
    directory = config.TASKS / "review"
    if not directory.is_dir():
        return
    branches = set(task_branches())
    for path in sorted(directory.glob("*.md")):
        try:
            task = read_task(path, "review")
        except OSError:
            continue
        if not task.get("pr") and path.stem in branches:
            maybe_open_pr(path.name)