"""Main Agent routing between simple chat and internal Task mode."""

from __future__ import annotations

import re

from .models import MainAgentDecision, TaskRecord


class MainAgentRouter:
    """Small deterministic classifier used before the main AgentLoop.

    The first version intentionally avoids a mandatory model call so the router
    stays reliable during provider outages. The rule set is conservative:
    anything that implies execution, files, tools, iteration, or validation
    becomes Task mode.
    """

    _TASK_PATTERNS = [
        r"\b(implement|fix|debug|refactor|migrate|build|create|write|edit|update|test|validate|deploy)\b",
        r"\b(file|repo|code|project|backend|frontend|api|database|migration|pull request|ci|bug)\b",
        r"\b(step|multi-step|workflow|plan and|then)\b",
        r"(实现|修复|调试|重构|迁移|构建|创建|编写|修改|更新|测试|验证|部署|文件|代码|项目|前端|后端|接口|数据库|多步|任务)",
    ]
    _NEW_TASK_PATTERNS = [
        r"\b(new task|another task|different task|start over)\b",
        r"(新任务|另一个任务|换个任务|重新开始)",
    ]

    def classify(self, message: str, *, active_task: TaskRecord | None = None) -> MainAgentDecision:
        text = message.strip()
        lowered = text.lower()
        starts_new = any(re.search(pattern, lowered, re.IGNORECASE) for pattern in self._NEW_TASK_PATTERNS)
        if active_task is not None and active_task.status in {"awaiting_feedback", "needs_revision"} and not starts_new:
            return MainAgentDecision(mode="task", reason="continuing_open_task", starts_new_task=False)
        if any(re.search(pattern, lowered, re.IGNORECASE) for pattern in self._TASK_PATTERNS):
            return MainAgentDecision(mode="task", reason="task_pattern_matched", starts_new_task=starts_new)
        if len(text) > 240:
            return MainAgentDecision(mode="task", reason="long_request", starts_new_task=starts_new)
        return MainAgentDecision(mode="simple", reason="simple_question", starts_new_task=False)