#!/usr/bin/env python3
"""session_start.py — deterministic SessionStart injection note for os-backlog.

Modeled on os-adr's session_start.py (the wording-source-of-record pattern).
Injects the backlog process rules — WHEN->THEN mechanical triggers only.
Deliberately contains ZERO board state and no briefs (notification policy v2:
pull beats push — board state is fetched on demand via /os-backlog:list, never
pushed into a session).

Sibling hook triage_check.rb (card 1818330518584820864) is a narrow, sanctioned
exception to that policy: it makes one bounded Planka read to decide whether to
push a single mechanical dispatch directive — not a brief, not board contents —
when the current project's own Backlog has unlabeled cards. The only board-
derived fact it ever surfaces is the unlabeled count that justifies dispatching
card-triage; it never lists card titles or otherwise renders board state. Kept
as a separate script precisely so this file can stay a pure, network-free
function of filesystem state.

  git project      -> additionalContext note (rules only, near-zero tokens)
  not a git repo   -> silent (process rules only apply inside real projects)

Autonomy-label semantics in NOTE are the ADR-029 contract (which supersedes
the wording in issue #16's body): hitl never picked up autonomously; semi
stops at Review for human sign-off; afk-ready goes straight to Done after
verification, skipping Review.

Pure function of the project's filesystem state; no model, no network, no
Ruby, no Planka call. Always exits 0 — the hook must never block a session.
"""

from __future__ import annotations

import json
import sys
from pathlib import Path
from typing import Optional

NOTE = """\
[os-backlog] Backlog process rules (rules only — this note never carries board state; board state is pull-only via /os-backlog:list when the user asks).
- CAPTURE: WHEN a concrete follow-up task, bug, or piece of deferred work surfaces mid-session that will NOT be done this session -> capture it as a Backlog card via /os-backlog:capture. Never a TODO comment in code, never only a mention in chat.
- ROUTING: WHEN process/backlog/spec-tracking work surfaces -> read the tracker key from .cc-os/config (`tracker=planka:<board>` | `forgejo:<owner>/<repo>` | `github:<owner>/<repo>` | `repo:<path>`) and send work where it says. WHEN this is a git project and no tracker key is configured -> suggest /os-backlog:route once; do not nag. A subdirectory's own .cc-os/config overrides the repo root's for any session started there — umbrella repos route each subproject to its own board/tracker this way; do not assume one repo means one board.
- PROMOTION: WHEN a Planka-tracked effort accretes significant code or design decisions in card comments -> flag promotion to the user (never silently): carve out a repo, move the durable spec into git issues via /to-issues, and keep the Planka card as a pointer (title + link). Never duplicate spec text into a card description.
- COLUMN OWNERSHIP (CLI-enforced per ADR-029; a violating card-move fails with the rule named): create cards at Backlog only. Never move a card into or out of Next — Next is human-curated in both directions. Never move a card labeled hitl; never move a card out of Done. Working a card MEANS moving it via card-move: Doing when work starts, Waiting + a blocker comment when blocked, and on shipping: Review (semi) or Done (afk-ready, only after verification).
- LABELING/TRIAGE: priority (P0-P3) and autonomy (hitl/semi/afk-ready) labeling is the RESPONSIBLE project's job (it knows its own priorities) — a parent umbrella may label its own and its child boards, but never label cards on a board that belongs to a different project you're just filing onto. Triage is initiated by this project's own SessionStart check (a separate hook), not by capture — if it reports unlabeled Backlog cards, dispatch the card-triage agent (haiku, background) to clear them.
- CROSS-PROJECT: WHEN a needed change belongs to a DIFFERENT project THEN do not edit it — query `os-backlog projects`, file an issue/card with that project's tracker using the Discoverer template (see os-backlog route references/cross-project-filing.md).
- AUTONOMY LABELS (ADR-029): hitl -> human-owned; never picked up autonomously. semi -> run the mechanical parts, stop at named decision gates; shipped work goes to Review for human sign-off. afk-ready -> shipped + verified goes straight to Done, skipping Review.
"""


def find_project_root(cwd: Path) -> Optional[Path]:
    """Nearest ancestor (including cwd) containing .git, else None."""
    for candidate in [cwd, *cwd.parents]:
        if (candidate / ".git").exists():
            return candidate
    return None


def run(root: Optional[Path], out) -> str:
    """Pure decision: ('context'|'silent'). Emits hook JSON when in a project."""
    if root is None:
        return "silent"
    out.write(json.dumps({
        "hookSpecificOutput": {
            "hookEventName": "SessionStart",
            "additionalContext": NOTE,
        }
    }))
    return "context"


def main() -> int:
    try:
        run(find_project_root(Path.cwd()), sys.stdout)
    except Exception:
        pass  # never block a session
    return 0


if __name__ == "__main__":
    sys.exit(main())