"""分支决策路由: 按决策树推导分支, 重叠区由端到端时延模型仲裁.

决策树 (v0.98 §3.3):
  1. 前置归约: BatchA=1 或 BatchB=1 -> 转Matmul (本期仅标注, 详实现后续迭代)
                K=0 / K=1 -> 特殊分支 (本期仅标注)
  2. B >= C: 切B -> IterBatch 与 MergeBatch 仲裁
       仲裁规则 (v1.1 §4.5 统一分界):
         MergeBatch 最优 <=> K截断(k_L1=K) 且 b_core > b0*(T_comp+T_write)/T_cmd
         L1 绑定时 MergeBatch 恒劣于 IterBatch;
       两分支同时合法时用端到端时延模型 T_total 仲裁.
  3. B < C: 切 M/N -> ASW_Basic (后续迭代)
  4. B/M/N 都买不满: 切 K -> StreamK (后续迭代)
"""

from __future__ import annotations

from .hardware import NpuSpec, ASCEND950PR
from .models import BmmCase, ImplPlan, HardwareTiming
from .branches.base import BranchResult
from .branches.merge_batch import MergeBatchBranch
from .branches.iter_batch import IterBatchBranch

BRANCH_TO_MATMUL = "转Matmul"
BRANCH_SPECIAL = "特殊分支"
BRANCH_ASW = "ASW_Basic"
BRANCH_STREAMK = "StreamK"


class BranchRouter:
    """case -> 理论最优分支 + 方案 + 时延评估."""

    def __init__(self, spec: NpuSpec = ASCEND950PR):
        self.spec = spec
        self.merge_batch = MergeBatchBranch(spec)
        self.iter_batch = IterBatchBranch(spec)

    # ------------------------------------------------------------------
    def route(self, case: BmmCase) -> dict:
        """返回 {branch, plan, timing, arbitration, candidates}."""
        s = self.spec

        # 1) 前置归约
        if case.batch_a == 1 or case.batch_b == 1:
            return self._stub(case, BRANCH_TO_MATMUL,
                              "BatchA=1或BatchB=1, 折叠转普通Matmul (该分支详实现待后续迭代)")
        if case.k <= 1:
            return self._stub(case, BRANCH_SPECIAL,
                              f"K={case.k}, Cube 无用, 走 AIV 向量通路 (该分支详实现待后续迭代)")

        # 2) B >= C: IterBatch / MergeBatch
        if case.batch_c >= s.aic_num and case.batch_a == case.batch_b:
            return self._route_split_b(case)

        # 3/4) 兜底标注
        return self._stub(case, BRANCH_ASW,
                          "B<C 或切B分支条件不满足 -> ASW_Basic/StreamK (该分支详实现待后续迭代)")

    # ------------------------------------------------------------------
    def _route_split_b(self, case: BmmCase) -> dict:
        mb = self.merge_batch.analyze(case)
        ib = self.iter_batch.analyze(case)

        candidates = []
        if mb.capable:
            candidates.append((self.merge_batch.name, mb))
        if ib.capable:
            candidates.append((self.iter_batch.name, ib))

        arbitration = ""
        if mb.capable and ib.capable:
            # 统一分界条件 + 端到端时延仲裁双保险
            mb_win, detail = self.merge_batch.beats_iterbatch(case)
            t_mb = mb.timing.t_total
            t_ib = ib.timing.t_total
            lat_win = self.merge_batch.name if t_mb <= t_ib else self.iter_batch.name
            win = self.merge_batch.name if mb_win else self.iter_batch.name
            arbitration = (
                f"两分支均合法, 仲裁:\n"
                f"  [分界条件] MergeBatch最优={mb_win} ({detail})\n"
                f"  [时延模型] T_MergeBatch={t_mb*1e6:.2f}us vs T_IterBatch={t_ib*1e6:.2f}us "
                f"-> {lat_win}更优\n"
                f"  [裁决] {win}" + ("" if win == lat_win else f" (分界条件与时延模型不一致, 以时延模型为准: {lat_win})")
            )
            if win != lat_win:
                win = lat_win  # 时延模型为最终裁决
        elif candidates:
            win = candidates[0][0]
            arbitration = f"仅 {win} 条件满足"
        else:
            return self._stub(
                case, BRANCH_ASW,
                "IterBatch/MergeBatch 进入条件均不满足 (如负载均衡/搬移效率不达标), "
                "回落 ASW_Basic (该分支详实现待后续迭代); "
                f"IterBatch未过: {ib.failed_conditions()}; "
                f"MergeBatch未过: {mb.failed_conditions()}")

        chosen = mb if win == self.merge_batch.name else ib
        return {
            "branch": win,
            "plan": chosen.plan,
            "timing": chosen.timing,
            "arbitration": arbitration,
            "candidates": {n: r.capable for n, r in
                           [(self.merge_batch.name, mb), (self.iter_batch.name, ib)]},
        }

    # ------------------------------------------------------------------
    def _stub(self, case: BmmCase, branch: str, note: str) -> dict:
        plan = ImplPlan(case_id=case.case_id, branch=branch,
                        used_core_num=self.spec.aic_num, note=note)
        return {"branch": branch, "plan": plan, "timing": None,
                "arbitration": note, "candidates": {}}