"""Parse a construction plan file's YAML frontmatter.

See docs/construction-plan-format.md. The frontmatter's status field is
the phase-4 hard gate: the build executor (executor.py) refuses to run
against anything but status: approved with both approved_by/approved_at
set.
"""

from __future__ import annotations

from dataclasses import dataclass
from pathlib import Path
from typing import Any

import yaml


class PlanError(RuntimeError):
    pass


@dataclass
class ConstructionPlan:
    id: str
    status: str
    approved_by: str | None
    approved_at: str | None
    demand_source: str
    consumer_repo: str
    credential_type: str
    path: Path

    @classmethod
    def load(cls, path: str | Path) -> ConstructionPlan:
        path = Path(path)
        text = path.read_text()
        parts = text.split("---", 2)
        if len(parts) < 3 or not text.startswith("---"):
            raise PlanError(f"{path}: missing YAML frontmatter")
        data: dict[str, Any] = yaml.safe_load(parts[1]) or {}
        missing = {"id", "status"} - set(data)
        if missing:
            raise PlanError(f"{path}: frontmatter missing field(s): {', '.join(sorted(missing))}")
        return cls(
            id=data["id"],
            status=data["status"],
            approved_by=data.get("approved_by"),
            approved_at=data.get("approved_at"),
            demand_source=data.get("demand_source", ""),
            consumer_repo=data.get("consumer_repo", ""),
            credential_type=data.get("credential_type", ""),
            path=path,
        )

    def is_approved(self) -> bool:
        return self.status == "approved" and bool(self.approved_by) and bool(self.approved_at)