#!/usr/bin/env python3
import argparse
import os
import sys
import time
from pathlib import Path

import torch
import yaml

PROJECT_ROOT = Path(__file__).resolve().parents[1]
if str(PROJECT_ROOT) not in sys.path:
    sys.path.insert(0, str(PROJECT_ROOT))

os.environ.setdefault("LEROBOT_VIDEO_BACKEND", "pyav")

from models.hrdt_runner import HRDTRunner
from models.encoder.dinosiglip_vit import DinoSigLIPViTBackbone
from hrdt_datasets.dataset import VLAConsumerDataset, DataCollatorForVLAConsumerDataset
from torch.utils.data import DataLoader


def main() -> None:
    parser = argparse.ArgumentParser(description="Overfit a single batch to sanity check loss.")
    parser.add_argument("--data_root", default="/hfm/data/pick_box")
    parser.add_argument("--config_path", default="configs/hrdt_finetune_lerobot.yaml")
    parser.add_argument("--pretrained_backbone_path", required=True)
    parser.add_argument("--vision_encoder", default="dino-siglip")
    parser.add_argument("--device", default="cuda:0")
    parser.add_argument("--steps", type=int, default=20)
    parser.add_argument("--lr", type=float, default=1e-4)
    parser.add_argument("--batch_size", type=int, default=2)
    parser.add_argument("--num_workers", type=int, default=1)
    parser.add_argument("--use_precomp_lang_embed", action="store_true")
    args = parser.parse_args()

    with open(args.config_path, "r") as f:
        config = yaml.safe_load(f)

    device = torch.device(args.device)

    vision_encoder = DinoSigLIPViTBackbone(
        vision_backbone_id=args.vision_encoder,
        image_resize_strategy="letterbox"
        if config["dataset"]["image_aspect_ratio"] == "pad"
        else "resize-naive",
        default_image_size=384,
    ).to(device)
    vision_encoder.eval()
    image_transform = vision_encoder.get_image_transform()

    dataset = VLAConsumerDataset(
        config=config,
        image_transform=image_transform,
        num_cameras=config["common"]["num_cameras"],
        image_aug=False,
        dataset_type="finetune",
        dataset_name="lerobot",
        dataset_root=args.data_root,
        use_precomp_lang_embed=args.use_precomp_lang_embed,
        upsample_rate=1,
    )
    collator = DataCollatorForVLAConsumerDataset(use_precomp_lang_embed=args.use_precomp_lang_embed)
    loader = DataLoader(dataset, batch_size=args.batch_size, shuffle=True, collate_fn=collator)
    loader = DataLoader(
        dataset,
        batch_size=args.batch_size,
        shuffle=True,
        collate_fn=collator,
        num_workers=args.num_workers,
        pin_memory=True,
        persistent_workers=args.num_workers > 0,
    )
    batch = next(iter(loader))

    if not Path(args.pretrained_backbone_path).exists():
        alt_path = Path("./checkpoints/pretrain-0618/checkpoint-500000/pytorch_model.bin")
        if alt_path.exists():
            print(f"[WARN] Using fallback pretrained backbone at {alt_path}")
            args.pretrained_backbone_path = str(alt_path)
        else:
            raise FileNotFoundError(
                f"Pretrained backbone not found: {args.pretrained_backbone_path}"
            )

    hrdt = HRDTRunner(
        state_dim=config["common"]["state_dim"],
        action_dim=config["common"]["action_dim"],
        pred_horizon=config["common"]["action_chunk_size"],
        config=config["model"],
        act_pos_emb_config=[("state", 1), ("action", config["common"]["action_chunk_size"])],
        img_pos_emb_config=[
            ("image", (config["common"]["img_history_size"], config["common"]["num_cameras"], -vision_encoder.num_patches)),
        ],
        lang_pos_emb_config=[
            ("language", -config["dataset"]["tokenizer_max_length"]),
        ],
        max_img_len=config["common"]["img_history_size"]
        * config["common"]["num_cameras"]
        * vision_encoder.num_patches,
        max_lang_len=config["dataset"]["tokenizer_max_length"],
        training_mode="lang",
        mode="finetune",
        pretrained_backbone_path=args.pretrained_backbone_path,
        dtype=torch.float32,
    ).to(device)

    optimizer = torch.optim.AdamW(hrdt.parameters(), lr=args.lr)

    images = batch["images"]
    with torch.no_grad():
        k = next(iter(images))
        batch_size, _, C, H, W = images[k].shape
        for key in images:
            images[key] = images[key].to(device).view(-1, C, H, W)
        image_features = vision_encoder(images).detach()
        image_features = image_features.view((batch_size, -1, vision_encoder.embed_dim))

    states = batch["states"].to(device)
    actions = batch["actions"].to(device)
    lang_embeds = batch.get("lang_embeds")
    lang_attn_mask = batch.get("lang_attn_mask")
    if lang_embeds is not None:
        lang_embeds = lang_embeds.to(device)
    if lang_attn_mask is not None:
        lang_attn_mask = lang_attn_mask.to(device)

    for step in range(args.steps):
        t0 = time.time()
        loss_dict = hrdt.compute_loss(
            state_tokens=states,
            action_gt=actions,
            image_tokens=image_features,
            lang_tokens=lang_embeds,
            lang_attn_mask=lang_attn_mask,
        )
        loss = loss_dict["loss"]
        optimizer.zero_grad(set_to_none=True)
        loss.backward()
        optimizer.step()
        dt = time.time() - t0
        print(f"step={step:03d} loss={loss.item():.6f} dt={dt:.3f}s")


if __name__ == "__main__":
    main()