#!/usr/bin/env python3
"""Validate the small task pointer loaded at the start of a work session."""

from __future__ import annotations

import argparse
import json
import re
from pathlib import Path


MAX_POINTER_BYTES = 8192
MAX_POINTER_LINES = 180
REQUIRED_HEADINGS = ("## Current", "## Read", "## Task", "## Next", "## Verify", "## Stop")
FORBIDDEN_HEADINGS = (
    "## 6. 已验证证据",
    "## Evidence",
    "## History",
    "## 历史",
    "## Chat",
)


class PointerError(ValueError):
    """Raised when the bootstrap pointer would expand the model context."""


def validate_pointer(
    path: Path,
    *,
    max_bytes: int = MAX_POINTER_BYTES,
    max_lines: int = MAX_POINTER_LINES,
    lock_path: Path | None = None,
) -> dict[str, int]:
    text = path.read_text(encoding="utf-8")
    size = len(text.encode("utf-8"))
    lines = len(text.splitlines())
    if size > max_bytes:
        raise PointerError(f"task pointer exceeds byte budget ({size}>{max_bytes})")
    if lines > max_lines:
        raise PointerError(f"task pointer exceeds line budget ({lines}>{max_lines})")
    missing = [heading for heading in REQUIRED_HEADINGS if heading not in text]
    if missing:
        raise PointerError(f"task pointer missing sections: {', '.join(missing)}")
    found = [heading for heading in FORBIDDEN_HEADINGS if re.search(rf"^\s*{re.escape(heading)}\s*$", text, re.MULTILINE)]
    if found:
        raise PointerError(f"task pointer contains history section: {found[0]}")
    if "coverage/" not in text:
        raise PointerError("task pointer must direct large evidence to paths")
    pointer_match = re.search(r"^context_id:\s*([^\s]+)\s*$", text, re.MULTILINE)
    if pointer_match is None:
        raise PointerError("task pointer is missing context_id")
    if lock_path is not None and lock_path.exists():
        try:
            lock = json.loads(lock_path.read_text(encoding="utf-8"))
        except (OSError, UnicodeError, json.JSONDecodeError) as exc:
            raise PointerError(f"cannot read context lock: {exc}") from exc
        lock_id = lock.get("context_id") if isinstance(lock, dict) else None
        if not lock_id:
            raise PointerError("context lock is missing context_id")
        if pointer_match.group(1) != str(lock_id):
            raise PointerError(
                f"task pointer context_id does not match lock ({pointer_match.group(1)}!={lock_id})"
            )
    return {"bytes": size, "lines": lines, "max_bytes": max_bytes, "max_lines": max_lines}


def main() -> int:
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument("path", nargs="?", type=Path, default=Path("nextTask.md"))
    parser.add_argument("--max-bytes", type=int, default=MAX_POINTER_BYTES)
    parser.add_argument("--max-lines", type=int, default=MAX_POINTER_LINES)
    parser.add_argument("--lock", type=Path, default=Path("context-lock.json"))
    args = parser.parse_args()
    try:
        result = validate_pointer(
            args.path,
            max_bytes=args.max_bytes,
            max_lines=args.max_lines,
            lock_path=args.lock,
        )
    except (OSError, UnicodeError, PointerError) as exc:
        parser.error(str(exc))
    print(f"task_pointer=valid bytes={result['bytes']} lines={result['lines']}")
    return 0


if __name__ == "__main__":
    raise SystemExit(main())