from __future__ import annotations
from typing import ClassVar
from .base import BaseAgent, AgentInput, AgentOutput


class OverdueTaskAgent(BaseAgent):
    """Reports the user's overdue tasks by count and age."""
    agent_id: ClassVar[str] = "overdue-task"
    ttl_seconds: ClassVar[int] = 3600  # 1h — overdue status changes infrequently
    version: ClassVar[str] = "1.0.0"

    def compute(self, inp: AgentInput) -> AgentOutput:
        overdue = [t for t in inp.tasks if t.get("is_overdue")]
        top = sorted(overdue, key=lambda t: -t.get("task_age_days", 0))[:3]

        if not overdue:
            prompt = "The user has no overdue tasks at this time."
        elif len(overdue) == 1:
            t = top[0]
            age = round(t.get("task_age_days", 0))
            prompt = (
                f'The user has 1 overdue task: "{t["content"]}" '
                f"({age} day{'s' if age != 1 else ''} overdue)."
            )
        else:
            items = ", ".join(
                f'"{t["content"]}" ({round(t.get("task_age_days", 0))}d)'
                for t in top
            )
            prompt = (
                f"The user has {len(overdue)} overdue tasks. "
                f"Top {len(top)}: {items}."
            )

        snapshot = {
            "overdue_count": len(overdue),
            "top_overdue": [
                {"content": t["content"], "task_age_days": t.get("task_age_days", 0)}
                for t in top
            ],
        }
        return self._make_output(inp, prompt, snapshot)