"""Thin Ouro mapping for LoopQ artifacts and future runtime integration."""

from __future__ import annotations

import hashlib
import json
from dataclasses import dataclass
from pathlib import Path

import torch

from loopq.cta import CrossLoopTransitionAdapter
from loopq.las import LoopAwareActivationScales
from loopq.quantization import quantize_weight
from loopq.transforms import SharedKroneckerTransform


OURO_LOOP_COUNT = 4
OURO_TRANSITION_COUNT = 3

PAPER_GROUPS = {
    "attention_qkv": {
        "hf_weights": ("self_attn.q_proj", "self_attn.k_proj", "self_attn.v_proj"),
        "vllm_consumers": ("self_attn.qkv_proj",),
        "transform_site": "self_attn.ln_trans",
    },
    "attention_output": {
        "hf_weights": ("self_attn.o_proj",),
        "vllm_consumers": ("self_attn.o_proj",),
        "transform_site": "self_attn.o_trans",
    },
    "mlp_up_gate": {
        "hf_weights": ("mlp.gate_proj", "mlp.up_proj"),
        "vllm_consumers": ("mlp.gate_up_proj",),
        "transform_site": "mlp.up_gate_trans",
    },
    "mlp_down": {
        "hf_weights": ("mlp.down_proj",),
        "vllm_consumers": ("mlp.down_proj",),
        "transform_site": "mlp.down_trans",
    },
}


@dataclass(frozen=True)
class OuroMappingValidation:
    revision: str
    config_sha256: str
    modeling_sha256: str
    physical_layers: int
    loop_count: int
    hidden_size: int
    intermediate_size: int
    checked_weight_keys: int

    def to_dict(self) -> dict[str, str | int]:
        return self.__dict__.copy()


def _sha256(path: Path) -> str:
    digest = hashlib.sha256()
    with path.open("rb") as handle:
        for chunk in iter(lambda: handle.read(1024 * 1024), b""):
            digest.update(chunk)
    return digest.hexdigest()


def validate_local_ouro_checkpoint(snapshot: str | Path) -> OuroMappingValidation:
    """Validate config and safetensors keys without loading parameter tensors."""

    root = Path(snapshot).resolve()
    config_path = root / "config.json"
    modeling_path = root / "modeling_ouro.py"
    checkpoint_path = root / "model.safetensors"
    if not all(path.is_file() for path in (config_path, modeling_path, checkpoint_path)):
        raise FileNotFoundError("Ouro snapshot must contain config, modeling code, and model.safetensors")
    config = json.loads(config_path.read_text())
    required_config = {
        "model_type": "ouro",
        "num_hidden_layers": 24,
        "total_ut_steps": OURO_LOOP_COUNT,
        "hidden_size": 2048,
        "intermediate_size": 5632,
        "torch_dtype": "bfloat16",
    }
    mismatches = {
        key: (config.get(key), expected)
        for key, expected in required_config.items()
        if config.get(key) != expected
    }
    if mismatches:
        raise ValueError(f"pinned Ouro config mismatch: {mismatches}")

    from safetensors import safe_open

    with safe_open(checkpoint_path, framework="pt", device="cpu") as checkpoint:
        keys = set(checkpoint.keys())
    required_weights = {
        f"model.layers.{layer}.{projection}.weight"
        for layer in range(config["num_hidden_layers"])
        for group in PAPER_GROUPS.values()
        for projection in group["hf_weights"]
    }
    missing = sorted(required_weights.difference(keys))
    if missing:
        raise ValueError(f"Ouro checkpoint is missing mapped projection weights: {missing[:8]}")
    return OuroMappingValidation(
        revision=root.name,
        config_sha256=_sha256(config_path),
        modeling_sha256=_sha256(modeling_path),
        physical_layers=config["num_hidden_layers"],
        loop_count=config["total_ut_steps"],
        hidden_size=config["hidden_size"],
        intermediate_size=config["intermediate_size"],
        checked_weight_keys=len(required_weights),
    )


class OuroLoopQAdapter:
    """Backend-neutral hook contract; it does not patch vLLM by itself."""

    loop_count = OURO_LOOP_COUNT
    group_names = tuple(PAPER_GROUPS)

    @staticmethod
    def module_key(layer_index: int, group_name: str) -> str:
        if not 0 <= layer_index < 24:
            raise IndexError("Ouro physical layer index must be in [0, 24)")
        if group_name not in PAPER_GROUPS:
            raise KeyError(f"unknown Ouro LoopQ group {group_name!r}")
        return f"model.layers.{layer_index}.{group_name}"

    @staticmethod
    def validate_loop(loop_index: int) -> None:
        if not 0 <= loop_index < OURO_LOOP_COUNT:
            raise IndexError("Ouro LoopQ loop index must be in [0, 4)")

    def prepare_activation(
        self,
        activation: torch.Tensor,
        *,
        layer_index: int,
        loop_index: int,
        group_name: str,
        transform: SharedKroneckerTransform,
        las: LoopAwareActivationScales | None,
        activation_bits: int,
        quantization_enabled: bool,
    ) -> torch.Tensor:
        self.validate_loop(loop_index)
        module_key = self.module_key(layer_index, group_name)
        transformed = transform(activation)
        if not quantization_enabled:
            return transformed
        if las is None:
            raise ValueError("quantized LoopQ activation requires LAS")
        return las.quantize(module_key, loop_index, transformed, bits=activation_bits).dequantized

    @staticmethod
    def prepare_weight(
        weight: torch.Tensor,
        *,
        transform: SharedKroneckerTransform,
        quantization_enabled: bool,
    ) -> torch.Tensor:
        folded = transform.fold_weight(weight)
        if not quantization_enabled:
            return folded
        return quantize_weight(folded).dequantized

    @staticmethod
    def apply_transition(
        hidden_state: torch.Tensor,
        *,
        completed_loop_index: int,
        cta: CrossLoopTransitionAdapter,
    ) -> torch.Tensor:
        if not 0 <= completed_loop_index < OURO_TRANSITION_COUNT:
            raise IndexError("CTA is valid only after Ouro loops 0, 1, and 2")
        if cta.transition_count != OURO_TRANSITION_COUNT:
            raise ValueError("Ouro CTA artifact must contain exactly 3 transitions")
        return cta(hidden_state, completed_loop_index)