"""PE_GEMM: matrix multiplication engine (ADR-0021 D6).

Handles both legacy PeInternalTxn (GemmCmd) and pipeline TileToken.
In pipeline mode, receives token after fetch stage, computes MAC, chains to next.

MAC latency model (from pe_accel):
  cycles = ceil(Tm/mac_m) * ceil(Tk/mac_k) * ceil(Tn/mac_n)
  latency_ns = cycles / clock_freq_ghz

Falls back to TFLOPS model when mac dimensions not configured.
"""
from __future__ import annotations

from collections.abc import Generator
from math import ceil
from typing import TYPE_CHECKING, Any

import simpy

from kernbench.components.base import PeEngineBase

if TYPE_CHECKING:
    from kernbench.common.pe_commands import PeInternalTxn
    from kernbench.components.context import ComponentContext
    from kernbench.topology.types import Node

_DTYPE_BITS: dict[str, int] = {
    "f16": 16, "fp16": 16, "float16": 16, "bf16": 16,
    "f32": 32, "fp32": 32, "float32": 32,
    "i8": 8, "int8": 8, "i16": 16, "int16": 16, "i32": 32, "int32": 32,
}


class PeGemmComponent(PeEngineBase):
    """PE_GEMM: MAC array (ADR-0021 D6).

    In pipeline mode: pure compute — register data already fetched.
    In legacy mode: handles PeInternalTxn(GemmCmd) with shared accel_slot.
    """

    def __init__(self, node: Node, ctx: ComponentContext | None = None) -> None:
        super().__init__(node, ctx)
        self._accel: simpy.Resource | None = None
        self._peak_tflops_f16: float = float(node.attrs.get("peak_tflops_f16", 0.0))
        # Cycle-accurate MAC dimensions (from pe_accel)
        self._mac_m: int = int(node.attrs.get("mac_m", 0))
        self._mac_k: int = int(node.attrs.get("mac_k", 0))
        self._mac_n: int = int(node.attrs.get("mac_n", 0))
        self._clock_freq: float = float(node.attrs.get("clock_freq_ghz", 1.0))

    def init_resources(self, env: simpy.Environment) -> None:
        resource_name = self.node.attrs.get("shared_resource")
        if resource_name and self.ctx:
            self._accel = self.ctx.get_shared_resource(
                env, f"{self._pe_prefix}.{resource_name}"
            )

    def _compute_ns_mac(self, m: int, k: int, n: int) -> float:
        """Cycle-accurate MAC latency (pe_accel model)."""
        if self._mac_m > 0 and self._mac_k > 0 and self._mac_n > 0:
            cycles = ceil(m / self._mac_m) * ceil(k / self._mac_k) * ceil(n / self._mac_n)
            return cycles / self._clock_freq
        return 0.0

    def _compute_ns_tflops(self, m: int, k: int, n: int, dtype: str = "f16") -> float:
        """TFLOPS-based latency (legacy model)."""
        if self._peak_tflops_f16 <= 0:
            return float(self.node.attrs.get("overhead_ns", 0.0))
        dtype_bits = _DTYPE_BITS.get(dtype, 16)
        effective_tflops = self._peak_tflops_f16 * (16.0 / dtype_bits)
        flops = 2.0 * m * k * n
        return flops / (effective_tflops * 1e3)

    def _compute_ns(self, m: int, k: int, n: int, dtype: str = "f16") -> float:
        """Choose best available latency model."""
        mac_ns = self._compute_ns_mac(m, k, n)
        if mac_ns > 0:
            return mac_ns
        return self._compute_ns_tflops(m, k, n, dtype)

    def run(self, env: simpy.Environment, nbytes: int) -> Generator:
        overhead_ns = float(self.node.attrs.get("overhead_ns", 0.0))
        yield env.timeout(overhead_ns)

    def _worker(self, env: simpy.Environment) -> Generator:
        from kernbench.common.pe_commands import PeInternalTxn
        from kernbench.components.builtin.pe_types import TileToken

        while True:
            msg: Any = yield self._inbox.get()
            if isinstance(msg, TileToken):
                env.process(self._pipeline_process(env, msg))
            elif isinstance(msg, PeInternalTxn):
                env.process(self._handle_with_hooks(env, msg))
            else:
                env.process(self._forward_txn(env, msg))

    def _pipeline_process(self, env: simpy.Environment, token: Any) -> Generator:
        """Pipeline mode: pure MAC compute, then self-route."""
        self._on_process_start(env, token)

        m = token.params.get("m", 0)
        k = token.params.get("k", 0)
        n = token.params.get("n", 0)

        if self._accel:
            with self._accel.request() as req:
                yield req
                ns = self._compute_ns(m, k, n)
                yield env.timeout(ns)
        else:
            ns = self._compute_ns(m, k, n)
            yield env.timeout(ns)

        self._on_process_end(env, token)

        # Self-routing
        next_stage = token.advance()
        if next_stage is not None:
            yield self.out_ports[next_stage.component].put(token)
        else:
            token.pipeline_ctx.complete_tile()

    def handle_command(self, env: simpy.Environment, pe_txn: PeInternalTxn) -> Generator:
        """Legacy PeInternalTxn handling."""
        from kernbench.common.pe_commands import GemmCmd

        cmd = pe_txn.command
        if self._accel:
            with self._accel.request() as req:
                yield req
                if isinstance(cmd, GemmCmd):
                    ns = self._compute_ns(cmd.m, cmd.k, cmd.n, cmd.a.dtype)
                    yield env.timeout(ns)
                else:
                    yield from self.run(env, 0)
        else:
            if isinstance(cmd, GemmCmd):
                ns = self._compute_ns(cmd.m, cmd.k, cmd.n, cmd.a.dtype)
                yield env.timeout(ns)
            else:
                yield from self.run(env, 0)
        pe_txn.done.succeed()

    def _forward_txn(self, env: simpy.Environment, txn: Any) -> Generator:
        if self._accel:
            with self._accel.request() as req:
                yield req
                yield from super()._forward_txn(env, txn)
        else:
            yield from super()._forward_txn(env, txn)