#!/usr/bin/env python3
import argparse
import json

from pathlib import Path
import re

from safetensors import safe_open

from gr00t.configs.model.gr00t_n1d6 import Gr00tN1d6Config


LAYER_RE = re.compile(r"\.language_model\.model\.layers\.(\d+)\.")


def _tensor_numel(shape):
    numel = 1
    for dim in shape:
        numel *= dim
    return numel


def _layer_index(param_name):
    match = LAYER_RE.search(param_name)
    if not match:
        return None
    return int(match.group(1))


def _is_trainable(name, cfg, total_layers):
    # Action head rules
    if name.startswith("action_head."):
        if name.startswith("action_head.model."):
            return cfg.tune_diffusion_model
        if name.startswith("action_head.vlln."):
            return cfg.tune_vlln
        if name.startswith("action_head.state_encoder."):
            return cfg.tune_projector
        if name.startswith("action_head.action_encoder."):
            return cfg.tune_projector
        if name.startswith("action_head.action_decoder."):
            return cfg.tune_projector
        if name.startswith("action_head.position_embedding."):
            return cfg.tune_projector
        if name.startswith("action_head.mask_token"):
            return cfg.tune_projector
        # Default to trainable for other action head params
        return True

    # Backbone rules
    if name.startswith("backbone."):
        if name.startswith("backbone.model.vision_model.") or name.startswith(
            "backbone.model.mlp1."
        ):
            return cfg.tune_visual
        if name.startswith("backbone.model.language_model."):
            if cfg.tune_llm:
                return True
            layer_idx = _layer_index(name)
            if layer_idx is None:
                return False
            if cfg.tune_top_llm_layers <= 0:
                return False
            return layer_idx >= max(total_layers - cfg.tune_top_llm_layers, 0)
        # Default: frozen if not clearly part of tunable submodules
        return False

    # Non-backbone/non-action_head params (if any)
    return True


def _load_shapes_from_safetensors(file_path, wanted_keys=None):
    shapes = {}
    with safe_open(str(file_path), framework="pt", device="cpu") as f:
        keys = wanted_keys if wanted_keys is not None else f.keys()
        for key in keys:
            if key not in f.keys():
                continue
            # Avoid loading full tensor; just get shape.
            shapes[key] = tuple(f.get_slice(key).get_shape())
    return shapes


def main():
    parser = argparse.ArgumentParser()
    parser.add_argument("--config", required=True, help="Path to Gr00tN1d6 config.json")
    args = parser.parse_args()

    config_path = Path(args.config)
    with open(config_path, "r") as f:
        cfg_dict = json.load(f)

    cfg = Gr00tN1d6Config(**cfg_dict)

    model_dir = config_path.parent
    index_path = model_dir / "model.safetensors.index.json"
    safetensors_path = model_dir / "model.safetensors"

    shapes = {}
    if index_path.exists():
        with open(index_path, "r") as f:
            index = json.load(f)
        weight_map = index.get("weight_map", {})
        keys_by_file = {}
        for key, fname in weight_map.items():
            keys_by_file.setdefault(fname, []).append(key)
        for fname, keys in keys_by_file.items():
            shapes.update(_load_shapes_from_safetensors(model_dir / fname, keys))
    elif safetensors_path.exists():
        shapes.update(_load_shapes_from_safetensors(safetensors_path))
    else:
        raise FileNotFoundError(
            "No safetensors found. Expected model.safetensors.index.json or model.safetensors "
            f"in {model_dir}"
        )

    # If select_layer truncates the LLM, ignore layers beyond it.
    if cfg.select_layer is not None and cfg.select_layer > 0:
        pruned = {}
        for name, shape in shapes.items():
            layer_idx = _layer_index(name)
            if layer_idx is not None and layer_idx >= cfg.select_layer:
                continue
            pruned[name] = shape
        shapes = pruned

    # Determine total layers from remaining keys
    layer_indices = sorted(
        {idx for name in shapes.keys() if (idx := _layer_index(name)) is not None}
    )
    total_layers = (max(layer_indices) + 1) if layer_indices else 0

    total = 0
    trainable = 0
    for name, shape in shapes.items():
        count = _tensor_numel(shape)
        total += count
        if _is_trainable(name, cfg, total_layers):
            trainable += count

    print(f"Total params:     {total:,}")
    print(f"Trainable params: {trainable:,}")


if __name__ == "__main__":
  main()