"""Dead-session recovery for cross-session PR base-syncs (#872).

Validates that when a sanctioned server-side base-sync (``gitea_update_pr_branch_by_merge``)
advances a PR's remote head from A to B (a merge commit whose first parent is A),
a subsequent author session whose local worktree is at A can recover the dead-session
lock via HEAD_RELATION_REMOTE_MERGE_SYNCED and execute a second base-sync (B to C)
without deadlock or RuntimeError.
"""

from __future__ import annotations

import os
import subprocess
import sys
import tempfile
import unittest
from datetime import datetime, timedelta, timezone
from pathlib import Path

sys.path.insert(0, str(Path(__file__).resolve().parent.parent))

import issue_lock_recovery  # noqa: E402
import issue_lock_store  # noqa: E402
import issue_lock_worktree  # noqa: E402

ISSUE = 8720
PR_NUMBER = 8721
BRANCH = f"fix/issue-{ISSUE}-dead-session-two-base-syncs"
IDENTITY = "example-author"
PROFILE = "prgs-author"
REMOTE = "prgs"
ORG = "ExampleOrg"
REPO = "ExampleRepo"


def dead_pid() -> int:
    proc = subprocess.Popen([sys.executable, "-c", "pass"])
    proc.wait()
    return proc.pid


def future_ts(hours: int = 4) -> str:
    return (
        (datetime.now(timezone.utc) + timedelta(hours=hours))
        .isoformat()
        .replace("+00:00", "Z")
    )


def _git(cwd, *args):
    return subprocess.run(
        ["git", "-C", cwd, *args],
        capture_output=True,
        text=True,
        check=True,
    )


def _rev(cwd, ref="HEAD") -> str:
    return _git(cwd, "rev-parse", ref).stdout.strip()


def build_two_base_sync_repo(tmp: str) -> dict:
    """Build a repo simulating two sequential base-sync merges."""
    _git(tmp, "init", "-q", "-b", "master")
    _git(tmp, "config", "user.email", "author@example.com")
    _git(tmp, "config", "user.name", "Author")
    Path(tmp, "base.txt").write_text("base 1\n")
    _git(tmp, "add", "-A")
    _git(tmp, "commit", "-q", "-m", "initial master")

    # Feature branch cut from initial master -> Head A (prior/recorded head)
    _git(tmp, "checkout", "-q", "-b", BRANCH)
    Path(tmp, "feature.txt").write_text("feature work\n")
    _git(tmp, "add", "-A")
    _git(tmp, "commit", "-q", "-m", "feature commit A")
    head_a = _rev(tmp)

    # Master advances -> Master 1
    _git(tmp, "checkout", "-q", "master")
    Path(tmp, "base.txt").write_text("base 1\nbase 2\n")
    _git(tmp, "add", "-A")
    _git(tmp, "commit", "-q", "-m", "master advance 1")
    master_1 = _rev(tmp)

    # First sync: merge master into feature -> Head B (merge commit, first parent = A)
    _git(tmp, "checkout", "-q", BRANCH)
    _git(tmp, "merge", "-q", "--no-ff", "-m", "First base-sync (merge master)", "master")
    head_b = _rev(tmp)

    # Master advances again -> Master 2
    _git(tmp, "checkout", "-q", "master")
    Path(tmp, "base.txt").write_text("base 1\nbase 2\nbase 3\n")
    _git(tmp, "add", "-A")
    _git(tmp, "commit", "-q", "-m", "master advance 2")
    master_2 = _rev(tmp)

    # Second sync: merge master into feature -> Head C (merge commit, first parent = B)
    _git(tmp, "checkout", "-q", BRANCH)
    _git(tmp, "merge", "-q", "--no-ff", "-m", "Second base-sync (merge master)", "master")
    head_c = _rev(tmp)

    # Non-merge rebase/force-pushed branch shape
    _git(tmp, "checkout", "-q", "-b", "rebased-branch", head_a)
    Path(tmp, "rebase.txt").write_text("rebased\n")
    _git(tmp, "add", "-A")
    _git(tmp, "commit", "-q", "-m", "rebased commit")
    rebased_head = _rev(tmp)

    # Reset worktree back to head A, as a dead session leaving local worktree at A
    _git(tmp, "checkout", "-q", BRANCH)
    _git(tmp, "reset", "-q", "--hard", head_a)

    return {
        "head_a": head_a,
        "master_1": master_1,
        "head_b": head_b,
        "master_2": master_2,
        "head_c": head_c,
        "rebased_head": rebased_head,
    }


def make_dead_lock(worktree, **over):
    pid = dead_pid()
    lock = {
        "issue_number": ISSUE,
        "branch_name": BRANCH,
        "worktree_path": worktree,
        "remote": REMOTE,
        "org": ORG,
        "repo": REPO,
        "session_pid": pid,
        "pid": pid,
        "claimant": {"username": IDENTITY, "profile": PROFILE},
        "work_lease": {
            "operation_type": issue_lock_store.AUTHOR_ISSUE_WORK_LEASE,
            "issue_number": ISSUE,
            "branch": BRANCH,
            "worktree_path": worktree,
            "claimant": {"username": IDENTITY, "profile": PROFILE},
            "expires_at": future_ts(),
        },
    }
    lock.update(over)
    return lock


class TestDeadSessionTwoBaseSyncs(unittest.TestCase):
    def setUp(self):
        self.tmp = tempfile.mkdtemp()
        self.shas = build_two_base_sync_repo(self.tmp)
        self.head_a = self.shas["head_a"]
        self.head_b = self.shas["head_b"]
        self.head_c = self.shas["head_c"]

    def test_first_base_sync_dead_session_recovery(self):
        """AC1: dead session after first base sync (remote=B, local=A) recovers via merge-sync."""
        lock = make_dead_lock(self.tmp, synced_pr_head=self.head_b)
        obs = issue_lock_worktree.read_merge_sync_provenance(
            self.tmp,
            prior_head_sha=self.head_a,
            synced_head_sha=self.head_b,
            remote=REMOTE,
        )
        self.assertTrue(obs["is_merge_sync"], obs["reasons"])
        self.assertTrue(obs["prior_is_ancestor"])
        self.assertTrue(obs["synced_is_merge"])
        self.assertTrue(obs["first_parent_reaches_prior"])

        res = issue_lock_recovery.assess_dead_session_lock_recovery(
            lock,
            issue_number=ISSUE,
            branch_name=BRANCH,
            worktree_path=self.tmp,
            remote=REMOTE,
            org=ORG,
            repo=REPO,
            identity=IDENTITY,
            profile=PROFILE,
            current_branch=BRANCH,
            porcelain_status="",
            head_sha=self.head_a,
            remote_head_sha=self.head_b,
            pr_head_sha=self.head_b,
            pr_number=PR_NUMBER,
            competing_live_locks=[],
            candidate_branches=[BRANCH],
            current_pid=os.getpid(),
            remote_branch_exists=True,
            sync_provenance=obs,
        )
        self.assertEqual(res["outcome"], issue_lock_recovery.RECOVERY_SANCTIONED, res["reasons"])
        self.assertEqual(
            res["evidence"]["head_relation"],
            issue_lock_recovery.HEAD_RELATION_REMOTE_MERGE_SYNCED,
        )
        self.assertEqual(res["evidence"]["accepted_head"], self.head_b)

    def test_second_base_sync_head_refresh_after_recovery(self):
        """AC2: after recovery, second base sync (remote B -> C) updates durable lock head."""
        lock_dir = tempfile.mkdtemp()
        lock_data = make_dead_lock(self.tmp, synced_pr_head=self.head_b)
        # Rebind to current PID as gitea_lock_issue does upon sanctioned recovery
        lock_data["session_pid"] = os.getpid()
        lock_data["pid"] = os.getpid()
        issue_lock_store.save_lock_file(
            issue_lock_store.lock_file_path(
                remote=REMOTE, org=ORG, repo=REPO, issue_number=ISSUE, lock_dir=lock_dir
            ),
            lock_data,
        )

        refresh_res = issue_lock_store.apply_durable_lock_head_refresh(
            remote=REMOTE,
            org=ORG,
            repo=REPO,
            issue_number=ISSUE,
            branch_name=BRANCH,
            worktree_path=self.tmp,
            pr_number=PR_NUMBER,
            identity=IDENTITY,
            profile=PROFILE,
            current_pid=os.getpid(),
            expected_old_head=self.head_b,
            new_head=self.head_c,
            synced_at=future_ts(0),
            base_head=self.shas["master_2"],
            lock_dir=lock_dir,
        )
        self.assertTrue(refresh_res["refreshed"], refresh_res["reasons"])
        self.assertTrue(refresh_res["read_after_write_ok"])
        loaded = issue_lock_store.load_issue_lock(
            remote=REMOTE, org=ORG, repo=REPO, issue_number=ISSUE, lock_dir=lock_dir
        )
        self.assertEqual(loaded.get("synced_pr_head"), self.head_c)

    def test_dirty_worktree_blocks_recovery(self):
        """AC3: tracked dirty edits block dead-session recovery."""
        lock = make_dead_lock(self.tmp)
        obs = issue_lock_worktree.read_merge_sync_provenance(
            self.tmp, prior_head_sha=self.head_a, synced_head_sha=self.head_b
        )
        res = issue_lock_recovery.assess_dead_session_lock_recovery(
            lock,
            issue_number=ISSUE,
            branch_name=BRANCH,
            worktree_path=self.tmp,
            remote=REMOTE,
            org=ORG,
            repo=REPO,
            identity=IDENTITY,
            profile=PROFILE,
            current_branch=BRANCH,
            porcelain_status=" M feature.txt\n",
            head_sha=self.head_a,
            remote_head_sha=self.head_b,
            pr_head_sha=self.head_b,
            pr_number=PR_NUMBER,
            competing_live_locks=[],
            candidate_branches=[BRANCH],
            current_pid=os.getpid(),
            remote_branch_exists=True,
            sync_provenance=obs,
        )
        self.assertEqual(res["outcome"], issue_lock_recovery.REFUSED)
        self.assertTrue(any("dirty" in r or "tracked" in r for r in res["reasons"]))

    def test_foreign_reclaimer_blocks_recovery(self):
        """AC4: a foreign claimant cannot recover a dead-session lock."""
        lock = make_dead_lock(self.tmp)
        obs = issue_lock_worktree.read_merge_sync_provenance(
            self.tmp, prior_head_sha=self.head_a, synced_head_sha=self.head_b
        )
        res = issue_lock_recovery.assess_dead_session_lock_recovery(
            lock,
            issue_number=ISSUE,
            branch_name=BRANCH,
            worktree_path=self.tmp,
            remote=REMOTE,
            org=ORG,
            repo=REPO,
            identity="intruder-user",
            profile=PROFILE,
            current_branch=BRANCH,
            porcelain_status="",
            head_sha=self.head_a,
            remote_head_sha=self.head_b,
            pr_head_sha=self.head_b,
            pr_number=PR_NUMBER,
            competing_live_locks=[],
            candidate_branches=[BRANCH],
            current_pid=os.getpid(),
            remote_branch_exists=True,
            sync_provenance=obs,
        )
        self.assertEqual(res["outcome"], issue_lock_recovery.REFUSED)

    def test_non_merge_rebased_remote_head_blocks_recovery(self):
        """AC5: a rebased/force-pushed remote head (not a merge commit) is refused."""
        lock = make_dead_lock(self.tmp)
        obs = issue_lock_worktree.read_merge_sync_provenance(
            self.tmp, prior_head_sha=self.head_a, synced_head_sha=self.shas["rebased_head"]
        )
        self.assertFalse(obs["is_merge_sync"])
        res = issue_lock_recovery.assess_dead_session_lock_recovery(
            lock,
            issue_number=ISSUE,
            branch_name=BRANCH,
            worktree_path=self.tmp,
            remote=REMOTE,
            org=ORG,
            repo=REPO,
            identity=IDENTITY,
            profile=PROFILE,
            current_branch=BRANCH,
            porcelain_status="",
            head_sha=self.head_a,
            remote_head_sha=self.shas["rebased_head"],
            pr_head_sha=self.shas["rebased_head"],
            pr_number=PR_NUMBER,
            competing_live_locks=[],
            candidate_branches=[BRANCH],
            current_pid=os.getpid(),
            remote_branch_exists=True,
            sync_provenance=obs,
        )
        self.assertEqual(res["outcome"], issue_lock_recovery.REFUSED)


if __name__ == "__main__":
    unittest.main()