#!/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 issue state and no briefs (notification policy v2:
pull beats push — issue state is fetched on demand via /os-backlog:list, never
pushed into a session).

Per ADR-0042 (2026-07-16), Planka is retired: git issues (Forgejo via tea,
GitHub via gh, or in-repo via repo:<path>) are the single tracker for both
task state and durable specs. State is modeled with labels, not columns —
there is no card-move, no board, no triage-dispatch hook to mention here.

  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-0042 contract (successor to
ADR-029's Planka-mechanics version): hitl never picked up autonomously; semi
stops at named decision gates and ships to the review label; afk-ready ships
and, once verified, closes directly.

Pure function of the project's filesystem state; no model, no network, no
Ruby, no tracker 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 — never carries board state; state is pull-only via /os-backlog:list when the user asks).
- CAPTURE: WHEN deferred work surfaces mid-session that will NOT be done this session -> capture it as an issue via /os-backlog:capture. Never a TODO comment in code, never only a mention in chat.
- ROUTING: read the tracker key from .cc-os/config (`tracker=forgejo:<owner>/<repo>` | `github:<owner>/<repo>` | `repo:<path>`; `planka:` is retired per ADR-0042 and rejected). WHEN no tracker key is configured in a git project -> suggest /os-backlog:route once; do not nag. A subdirectory's own .cc-os/config overrides the repo root's — umbrella repos route each subproject to its own tracker this way.
- NEXT IS HUMAN-ONLY: never apply or remove the `next` label on any issue, any project, absent an explicit direct user request naming that issue.
- WORKING AN ISSUE: comment when work starts. Blocked -> add `waiting` + a comment naming the blocker; remove `waiting` on resume. Shipping: `semi` -> add `review` label + a summary comment, stays open for sign-off; `afk-ready` -> close directly once verified, with a comment linking the evidence.
- AUTONOMY LABELS: `hitl` -> human-owned, never picked up autonomously. `semi` -> run the mechanical parts, stop at named decision gates. `afk-ready` -> run to completion and verify before closing.
- RECURRING ISSUES: never closed by the AI — comment each occurrence's outcome and leave it open.
- CROSS-PROJECT: WHEN a needed change belongs to a DIFFERENT project THEN do not edit it — query `os-backlog projects`, file an issue on that project's tracker using the Discoverer template (see os-backlog route references/cross-project-filing.md); no autonomy/priority labels applied by the filer.
"""


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())