"""
ADR 变更爆炸半径分类 — P1-21 / 3.2.17 Phase 1 组件。
将 ADR 内容变更按影响范围分为 IMPLEMENTATION / INTERFACE / GLOBAL_CONSTRAINT 三级。
"""

from __future__ import annotations

import enum
from dataclasses import dataclass, field
from pathlib import Path


class BlastRadius(enum.Enum):
    IMPLEMENTATION = "implementation"
    INTERFACE = "interface"
    GLOBAL_CONSTRAINT = "global_constraint"


@dataclass
class ChangeClassification:
    adr_id: str
    blast_radius: BlastRadius
    reason: str = ""
    changed_sections: list[str] = field(default_factory=list)


class ChangeClassifier:
    """基于关键词启发式的 ADR 变更爆炸半径分类。

    分类规则：
    - IMPLEMENTATION: 仅实现细节变更，不影响公开接口。关键词：implementation detail, can use, for example, internal, private
    - INTERFACE: 公开 API/合约变更。关键词：interface, api, contract, signature, must implement, public header, exported, caller
    - GLOBAL_CONSTRAINT: 跨模块约束变更。关键词：must, shall, all modules, coding standard, every module, entire system, global policy

    回退策略：内容不足无法确定时回退到 INTERFACE（保守：宁可多失效不少失效）。
    """

    _INTERFACE_KEYWORDS = [
        "interface", "api", "contract", "signature", "must implement",
        "public header", "exported", "caller",
    ]
    _GLOBAL_KEYWORDS = [
        "must", "shall", "all modules", "coding standard",
        "every module", "entire system", "global policy",
    ]
    _IMPLEMENTATION_KEYWORDS = [
        "implementation detail", "can use", "for example",
        "internally", "private", "optional",
    ]

    def classify(self, adr_id: str, old_content: str | None,
                 new_content: str | None) -> ChangeClassification:
        if new_content is None:
            return ChangeClassification(
                adr_id=adr_id, blast_radius=BlastRadius.GLOBAL_CONSTRAINT,
                reason="ADR deleted — all dependent tasks must be invalidated",
            )
        if old_content is None:
            return ChangeClassification(
                adr_id=adr_id, blast_radius=BlastRadius.IMPLEMENTATION,
                reason="new ADR — no existing tasks to invalidate",
            )

        text = new_content.lower()

        global_hits = sum(1 for kw in self._GLOBAL_KEYWORDS if kw in text)
        interface_hits = sum(1 for kw in self._INTERFACE_KEYWORDS if kw in text)
        impl_hits = sum(1 for kw in self._IMPLEMENTATION_KEYWORDS if kw in text)

        if global_hits >= 2:
            return ChangeClassification(
                adr_id=adr_id, blast_radius=BlastRadius.GLOBAL_CONSTRAINT,
                reason=f"global constraint keywords matched ({global_hits} hits)",
            )
        if interface_hits >= 2:
            return ChangeClassification(
                adr_id=adr_id, blast_radius=BlastRadius.INTERFACE,
                reason=f"interface keywords matched ({interface_hits} hits)",
            )
        if interface_hits >= 1:
            return ChangeClassification(
                adr_id=adr_id, blast_radius=BlastRadius.INTERFACE,
                reason="interface keyword matched — conservative classification",
            )
        if impl_hits >= interface_hits and impl_hits > 0:
            return ChangeClassification(
                adr_id=adr_id, blast_radius=BlastRadius.IMPLEMENTATION,
                reason=f"implementation keywords matched ({impl_hits} hits)",
            )

        # 无法确定 → 保守回退
        return ChangeClassification(
            adr_id=adr_id, blast_radius=BlastRadius.INTERFACE,
            reason="inconclusive — defaulting to INTERFACE (conservative)",
        )

    def classify_from_files(self, adr_id: str, old_path: Path | None,
                            new_path: Path | None) -> ChangeClassification:
        old_content = old_path.read_text(encoding="utf-8") if old_path and old_path.exists() else None
        new_content = new_path.read_text(encoding="utf-8") if new_path and new_path.exists() else None
        return self.classify(adr_id, old_content, new_content)