"""Bounded helpers for destructive Gitea pull-request lifecycle cleanup."""

from __future__ import annotations

import re
from typing import Any, Protocol

from packages.connector_kit import GiteaError, RegisteredRepository

_VIRTUAL_PULL_HEAD = re.compile(r"refs/pull/[1-9][0-9]*/head")


class PullRequestReader(Protocol):
    def pull_requests(
        self, repository: RegisteredRepository, page: int, limit: int
    ) -> list[dict[str, Any]]: ...


def cleanup_basis(
    client: PullRequestReader,
    repository: RegisteredRepository,
    branch: str,
    expected_head_sha: str,
) -> tuple[dict[str, Any] | None, dict[str, Any] | None]:
    """Return the merged/closed PR proving one exact branch is cleanup-eligible."""
    related: list[dict[str, Any]] = []
    for page_number in range(1, 11):
        pulls = client.pull_requests(repository, page_number, 100)
        for item in pulls:
            head = item.get("head") or {}
            head_ref = str(head.get("ref", ""))
            head_sha = str(head.get("sha", ""))
            if head_ref == branch or (
                head_sha == expected_head_sha and _VIRTUAL_PULL_HEAD.fullmatch(head_ref)
            ):
                related.append(item)
        if len(pulls) < 100:
            break

    if any(str(item.get("state", "")) == "open" for item in related):
        raise GiteaError(
            "GITEA_TARGET_INVALID",
            "branch is still referenced by an open pull request; close or merge it first",
        )
    merged = next((item for item in related if bool(item.get("merged", False))), None)
    closed = next(
        (
            item
            for item in related
            if str(item.get("state", "")) == "closed" and not bool(item.get("merged", False))
        ),
        None,
    )
    if merged is None and closed is None:
        raise GiteaError(
            "GITEA_TARGET_INVALID",
            "only a change branch from a merged or closed pull request can be deleted",
        )
    return merged, closed