"""Decide whether an assigned issue is agent-targeted, and for whom.

An issue is forge-targeted when BOTH hold:
- it carries a `bot-bottle:<agent>` label naming the agent, and
- at least one assignee is a member of the configured org.

An optional `bot-bottle-bottle:<name>` label overrides bottle selection.
The forge is duck-typed: any object with `is_org_member(org, user)`.
"""

from __future__ import annotations

from dataclasses import dataclass
from typing import Protocol

from .config import BOTTLE_LABEL_PREFIX, LABEL_PREFIX
from .model import IssueAssigned


class Membership(Protocol):
    def is_org_member(self, org: str, username: str) -> bool: ...


@dataclass(frozen=True)
class Target:
    agent_name: str
    bottle_override: str | None


def parse_labels(labels: tuple[str, ...]) -> tuple[str | None, str | None]:
    """Return (agent_name, bottle_override) parsed from labels."""
    agent: str | None = None
    bottle: str | None = None
    for label in labels:
        if label.startswith(BOTTLE_LABEL_PREFIX):
            bottle = label[len(BOTTLE_LABEL_PREFIX):] or None
        elif label.startswith(LABEL_PREFIX):
            agent = label[len(LABEL_PREFIX):] or None
    return agent, bottle


def resolve_target(
    event: IssueAssigned, forge: Membership, org: str
) -> Target | None:
    """Return the `Target` for a forge-targeted issue, or None to ignore."""
    agent, bottle = parse_labels(event.labels)
    if not agent:
        return None
    if not any(forge.is_org_member(org, a) for a in event.assignees):
        return None
    return Target(agent_name=agent, bottle_override=bottle)