"""前向链推理机：知识库规则驱动的工作记忆演化（专家系统推理核心，零依赖）。

流程（经典前向链 forward chaining）：
1. 初始化黑板：写入领域/难度/置信度等事实
2. 循环：在领域内匹配规则（未触发过的）→ 按优先级执行
   - 命中即记录轨迹 rule:<id>@<priority>
   - 规则带 output 模板 → 渲染后写入黑板章节（部分解）
   - 规则带 actions → 执行动作（写事实/写章节）
3. 终止：无新规则可触发 / 达到步数上限（防死循环）

确定性保证：规则匹配基于子串包含，无随机性；同输入 → 同轨迹。
"""
from __future__ import annotations

from typing import Any, Dict, List, Optional

from .knowledge import KnowledgeBase, Rule
from .memory import WorkingMemory


def render_template(template: str, query: str, facts: Dict[str, Any]) -> str:
    """渲染输出模板：替换 {query} 与 {facts.<key>} 占位符；缺失以 [未提供] 占位，不抛异常。"""
    out = template.replace("{query}", query)
    for key, value in facts.items():
        out = out.replace(f"{{facts.{key}}}", str(value))
    # 剩余占位符兜底
    while "{" in out and "}" in out:
        start = out.find("{")
        end = out.find("}", start)
        if end == -1:
            break
        out = out[:start] + "[未提供]" + out[end + 1:]
    return out


class InferenceEngine:
    """前向链推理机。"""

    def __init__(self, kb: KnowledgeBase, max_steps: int = 20):
        self.kb = kb
        self.max_steps = max_steps

    # ---------------------------------------------------------------
    def initialize(self, query: str, domain: str, difficulty: str,
                   confidence: float, memory: WorkingMemory) -> None:
        """把分类结果写入黑板（事实初始化）。"""
        memory.write_fact("query", query)
        memory.write_fact("domain", domain)
        memory.write_fact("difficulty", difficulty)
        memory.write_fact("confidence", round(confidence, 4))
        memory.add_trace(f"init:domain={domain},difficulty={difficulty},conf={confidence:.2f}")

    # ---------------------------------------------------------------
    def run(self, query: str, domain: str, memory: WorkingMemory,
            max_steps: Optional[int] = None) -> List[str]:
        """前向链主循环。返回触发规则 id 列表（按触发顺序）。"""
        steps = max_steps or self.max_steps
        fired: List[str] = []
        for _ in range(steps):
            rules = self.kb.match(query, domain=domain)
            # 选第一个"未触发过"的规则
            target: Optional[Rule] = None
            for r in rules:
                if r.id not in fired:
                    target = r
                    break
            if target is None:
                break  # 无新规则可触发 → 终止
            fired.append(target.id)
            self._fire(target, query, memory)
        return fired

    # ---------------------------------------------------------------
    def _fire(self, rule: Rule, query: str, memory: WorkingMemory) -> None:
        """执行一条规则：记录轨迹 + 写事实 + 产出章节。"""
        memory.add_trace(f"rule:{rule.id}@{rule.priority}")
        # 规则动作
        for action in rule.actions:
            self._apply_action(action, rule, query, memory)
        # 规则输出模板 → 章节
        if rule.output:
            text = render_template(rule.output, query, memory.facts)
            memory.write_section(rule.id, text)

    def _apply_action(self, action: str, rule: Rule, query: str,
                      memory: WorkingMemory) -> None:
        """动作格式：write_fact:key=value（value 支持 {query} 占位）。"""
        if action.startswith("write_fact:"):
            kv = action[len("write_fact:"):]
            key, _, value = kv.partition("=")
            value = value.replace("{query}", query)
            memory.write_fact(key.strip(), value.strip(), rule_id=rule.id)
        # 其他动作类型暂不实现（保留扩展位）