"""Strict loading of the self-contained schema25 native MLX preview export."""

from __future__ import annotations

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

import mlx.core as mx
from mlx.utils import tree_flatten
from transformers import AutoTokenizer

from modilify_mk2.configuration_modilify_mk2 import (
    ModilifyMk2Config, require_current_checkpoint_protocol,
    configure_generation_config, load_generation_config,
)
from modilify_mk2.mlx_model import (
    MLXModilifyMk2, LoRAConfig, create_mlx_text_backbone, inject_mlx_lora,
)


@dataclass
class MLXRuntime:
    model: MLXModilifyMk2
    tokenizer: Any
    config: Any
    generation: Any
    checkpoint: Path
    step: int
    tensor_count: int


PRECISION_POLICY = "gdn2_small_fp32_v1"


def small_parameter_fp32(name: str) -> bool:
    return name.startswith("latent_deliberation.") and (
        name.endswith((".dt_bias", ".a_log"))
        or (name.endswith(".weight") and "norm" in name.rsplit(".", 2)[-2])
    )


def model_dtype(name: str, policy: str) -> str:
    if policy != PRECISION_POLICY:
        raise RuntimeError(f"Unsupported trainable precision policy: {policy}")
    return "float32" if small_parameter_fp32(name) else "bfloat16"


def _install_sliding_encoder_masks(encoder: Any) -> None:
    """Align mlx-vlm's full-length masks with trimmed sliding KV chunks."""

    if getattr(encoder, "_mlx_training_sliding_masks", False):
        return
    original = encoder._make_encoder_masks
    window = int(encoder.text_config.sliding_window)

    def make_masks(h, cache, attention_mask=None, mm_token_type_ids=None):
        masks = original(h, cache, attention_mask, mm_token_type_ids)
        if isinstance(masks, dict):
            return masks
        query_length = int(h.shape[1])
        maximum = window - 1 + query_length
        return [
            mask[..., -maximum:] if (
                layer.layer_type == "sliding_attention"
                and isinstance(mask, mx.array) and mask.shape[-1] > maximum
            ) else mask
            for layer, mask in zip(encoder.decoder.layers, masks)
        ]

    encoder._make_encoder_masks = make_masks
    encoder._mlx_training_sliding_masks = True


def load_runtime(
    model_path: str | Path, *,
    canvas_length: int | None, max_new_tokens: int,
    max_denoising_steps: int | None, repetition_penalty: float,
    commit_failure_budget: float | None = None, commit_top_k: int | None = None,
    commit_min_p: float | None = None, commit_target_confidence: float | None = None,
) -> MLXRuntime:
    root = resolve_model_path(model_path)
    manifest = json.loads((root / 'export_manifest.json').read_text(encoding='utf-8'))
    require_current_checkpoint_protocol(manifest)
    if manifest.get('format') != 'modilify_mk2_native_mlx_inference_v1':
        raise RuntimeError('Unsupported native MLX inference export format.')
    config = ModilifyMk2Config.from_pretrained(root, local_files_only=True)
    for name, value in (
        ('commit_failure_budget', commit_failure_budget),
        ('commit_top_k', commit_top_k), ('commit_min_p', commit_min_p),
        ('commit_target_confidence', commit_target_confidence),
    ):
        if value is not None:
            setattr(config, name, value)
    if canvas_length is not None and not 1 <= canvas_length <= int(config.canvas_length):
        raise ValueError('--canvas-length must be within the exported canvas.')
    backbone = create_mlx_text_backbone(config)
    lora = dict(manifest['lora_config'])
    lora['target_modules'] = tuple(lora['target_modules'])
    inject_mlx_lora(backbone, LoRAConfig(**lora))
    model = MLXModilifyMk2(backbone, config)
    model.latent_deliberation.set_dtype(mx.bfloat16)
    expected = dict(tree_flatten(model.parameters()))
    trainables = dict(tree_flatten(model.trainable_parameters()))
    if set(trainables) != set(manifest['trainable_names']):
        raise RuntimeError('Export trainable topology does not match this model.')
    specs = manifest['tensors']
    index = json.loads((root / 'model.safetensors.index.json').read_text(encoding='utf-8'))
    weight_map = index['weight_map']
    if set(expected) != set(specs) or set(expected) != set(weight_map):
        raise RuntimeError('Export must cover every model tensor exactly once.')
    shard_names = [item['file'] for item in manifest['shards']]
    if len(shard_names) != len(set(shard_names)) or set(shard_names) != set(weight_map.values()):
        raise RuntimeError('Export shard list and weight index disagree.')
    for name in trainables:
        if specs[name]['dtype'] != model_dtype(name, manifest['precision_policy']):
            raise RuntimeError(f'Export trainable precision mismatch: {name}')
    for shard in manifest['shards']:
        name = shard['file']
        if Path(name).name != name:
            raise RuntimeError('Export shards must be local filenames.')
        path = root / name
        if not path.is_file() or path.stat().st_size != shard['bytes']:
            raise RuntimeError(f'Export shard is missing or truncated: {name}')
        digest = hashlib.sha256()
        with path.open('rb') as handle:
            for block in iter(lambda: handle.read(8 * 1024 * 1024), b''):
                digest.update(block)
        if digest.hexdigest() != shard['sha256']:
            raise RuntimeError(f'Export shard checksum mismatch: {name}')
        raw = mx.load(str(path))
        declared = {key for key, value in weight_map.items() if value == name}
        if set(raw) != declared or set(shard['tensors']) != declared:
            raise RuntimeError(f'Export shard tensor index mismatch: {name}')
        for key, value in raw.items():
            dtype = str(value.dtype).removeprefix('mlx.core.')
            if (list(value.shape) != specs[key]['shape'] or
                    value.shape != expected[key].shape or dtype != specs[key]['dtype']):
                raise RuntimeError(f'Export tensor shape/dtype mismatch: {key}')
            if '.lora_' in key and '.experts.' not in key:
                # Schema25 restores dense adapters by transposing canonical
                # masters. Recreate that column-major layout: BF16 matmul
                # reductions can differ when Safetensors makes it row-major.
                raw[key] = mx.contiguous(value.T).T
        model.load_weights(list(raw.items()), strict=False)
        mx.eval(*raw.values())
        del raw
    if canvas_length is not None:
        config.canvas_length = canvas_length
    model.eval()
    _install_sliding_encoder_masks(model.model.encoder)
    tokenizer = AutoTokenizer.from_pretrained(root, trust_remote_code=True, local_files_only=True)
    generation = configure_generation_config(
        load_generation_config(root), tokenizer,
        max_new_tokens=max_new_tokens, max_denoising_steps=max_denoising_steps,
        repetition_penalty=repetition_penalty,
    )
    return MLXRuntime(model, tokenizer, config, generation, root,
                        int(manifest['global_step']), len(trainables))


def resolve_model_path(model: str | Path) -> Path:
    """Resolve a local release or download its snapshot from Hugging Face."""
    local = Path(model).expanduser()
    if local.is_dir():
        if not (local / 'export_manifest.json').is_file():
            raise ValueError(f'Missing export_manifest.json in model directory: {local}')
        return local.resolve()
    if local.is_absolute() or str(model).startswith(('.', '~')):
        raise FileNotFoundError(f'Model directory does not exist: {local}')
    from huggingface_hub import snapshot_download
    return Path(snapshot_download(repo_id=str(model), allow_patterns=[
        'export_manifest.json', 'config.json', 'generation_config.json',
        'model*.safetensors', 'model.safetensors.index.json',
        'tokenizer.json', 'tokenizer_config.json', 'chat_template.jinja',
    ]))