"""Dual-run flags and checkout-mutation meter (RMGR-WP-0002 / ArchitectureBlueprint Stage B).

Environment variables (shared with State Hub adapter):

  RM_WRITEBACK=1|true|yes   — file+git task writeback via repo-manager
  RM_RECONCILE=1|true|yes   — reconcile path prefers repo-manager for pilot repos
  RM_PILOT_REPOS=slug1,slug2 — if set, flags only apply to these slugs; empty = all
  RM_METER_PATH=~/.repo-manager/mutation-meter.jsonl — append-only meter log

Rollback: unset flags or set to 0 → State Hub native path only.
"""

from __future__ import annotations

import json
import os
from datetime import datetime, timezone
from pathlib import Path
from typing import Any, Literal

Source = Literal["state-hub", "repo-manager"]


def _truthy(name: str) -> bool:
    return os.environ.get(name, "").strip().lower() in {"1", "true", "yes", "on"}


def writeback_enabled() -> bool:
    return _truthy("RM_WRITEBACK")


def reconcile_enabled() -> bool:
    return _truthy("RM_RECONCILE")


def pilot_slugs() -> set[str] | None:
    """None means all repos; empty set after parse of blank list means none."""
    raw = os.environ.get("RM_PILOT_REPOS")
    if raw is None:
        return None
    raw = raw.strip()
    if not raw:
        return set()
    return {s.strip() for s in raw.split(",") if s.strip()}


def slug_allowed(slug: str | None) -> bool:
    if not slug:
        return False
    pilots = pilot_slugs()
    if pilots is None:
        return True
    return slug in pilots


def writeback_for_repo(slug: str | None) -> bool:
    return writeback_enabled() and slug_allowed(slug)


def reconcile_for_repo(slug: str | None) -> bool:
    return reconcile_enabled() and slug_allowed(slug)


def meter_path() -> Path:
    raw = os.environ.get("RM_METER_PATH", "~/.repo-manager/mutation-meter.jsonl")
    return Path(raw).expanduser()


def record_mutation(
    *,
    source: Source,
    kind: str,
    repo_slug: str | None,
    detail: dict[str, Any] | None = None,
) -> None:
    """Append one meter line. Best-effort; never raises to callers."""
    try:
        path = meter_path()
        path.parent.mkdir(parents=True, exist_ok=True)
        row = {
            "ts": datetime.now(timezone.utc).isoformat(),
            "source": source,
            "kind": kind,
            "repo_slug": repo_slug,
            "detail": detail or {},
        }
        with path.open("a", encoding="utf-8") as fh:
            fh.write(json.dumps(row, default=str) + "\n")
    except OSError:
        pass


def meter_summary(path: Path | None = None) -> dict[str, int]:
    path = path or meter_path()
    counts: dict[str, int] = {"state-hub": 0, "repo-manager": 0, "total": 0}
    if not path.is_file():
        return counts
    for line in path.read_text(encoding="utf-8").splitlines():
        line = line.strip()
        if not line:
            continue
        try:
            row = json.loads(line)
        except json.JSONDecodeError:
            continue
        src = row.get("source")
        if src in counts:
            counts[src] += 1
        counts["total"] += 1
    return counts


def flags_status() -> dict[str, Any]:
    return {
        "RM_WRITEBACK": writeback_enabled(),
        "RM_RECONCILE": reconcile_enabled(),
        "RM_PILOT_REPOS": sorted(pilot_slugs()) if pilot_slugs() is not None else None,
        "RM_METER_PATH": str(meter_path()),
        "meter": meter_summary(),
    }