"""
DrivAerML Preprocessing Script
================================
Downloads boundary_i.vtp files from neashton/drivaerml, samples 100k cell
centres with CFD fields, applies local coordinate normalisation, and saves
as boundary_i.pt in a staging directory for upload to HuggingFace.

Usage:
    pip install pyvista huggingface_hub torch numpy requests
    export HF_TOKEN=your_token_here
    python preprocess_drivaerml.py [--start 1] [--end 500]
"""

import os, sys, argparse, tempfile, shutil, requests
import numpy as np
import torch

SOURCE_REPO  = "neashton/drivaerml"
TARGET_REPO  = "JrHoss/DrivaerML-PCTR"
N_POINTS     = 100_000
SEED         = 42
STAGING_DIR  = "./staging"

MISSING_RUNS = {
    167, 211, 218, 221, 248, 282, 291, 295,
    316, 325, 329, 364, 370, 376, 403, 473
}

TARGET_FIELDS = [
    "CpMeanTrim",
    "pMeanTrim",
    "pPrime2MeanTrim",
    "wallShearStressMeanTrim",
]


# ── Core processing ────────────────────────────────────────────────────────────

def download_vtp(run_id, dest, token):
    url = f"https://huggingface.co/datasets/{SOURCE_REPO}/resolve/main/run_{run_id}/boundary_{run_id}.vtp"
    with requests.get(url, headers={"Authorization": f"Bearer {token}"}, stream=True, timeout=300) as r:
        if r.status_code == 404:
            return False
        r.raise_for_status()
        with open(dest, "wb") as f:
            for chunk in r.iter_content(chunk_size=8192 * 1024):
                f.write(chunk)
    return True


def process_vtp(vtp_path, run_id):
    """Extract cell centres and target fields from a VTP file."""
    import pyvista as pv
    mesh    = pv.read(vtp_path)
    coords  = np.array(mesh.cell_centers().points, dtype=np.float32)  # [M, 3]
    targets = np.zeros((len(coords), 4), dtype=np.float32)
    for i, field in enumerate(TARGET_FIELDS):
        data = np.array(mesh.cell_data[field], dtype=np.float32)
        if data.ndim == 2:                          # wallShearStress is a vector
            data = np.linalg.norm(data, axis=1)
        targets[:, i] = data
    return coords, targets


def sample_and_normalise(coords, targets, run_id):
    """Random sample 100k points and apply per-axis z-score normalisation."""
    rng = np.random.default_rng(run_id + SEED)
    idx = rng.choice(len(coords), size=N_POINTS, replace=len(coords) < N_POINTS)

    coords  = coords[idx]
    targets = targets[idx]

    mean = coords.mean(axis=0)
    std  = np.where((s := coords.std(axis=0)) < 1e-8, 1.0, s)

    return (coords - mean) / std, targets, idx, mean, std


def make_pt(coords_norm, targets, idx, mean, std, run_id):
    return {
        "coords":      torch.tensor(coords_norm, dtype=torch.float32),  # [100000, 3]
        "targets":     torch.tensor(targets,     dtype=torch.float32),  # [100000, 4]
        "sample_idx":  torch.tensor(idx,         dtype=torch.int64),
        "coords_mean": torch.tensor(mean,        dtype=torch.float32),  # [3]
        "coords_std":  torch.tensor(std,         dtype=torch.float32),  # [3]
        "run_id":      run_id,
    }


# ── Per-run pipeline ───────────────────────────────────────────────────────────

def process_run(run_id, token, tmp_dir):
    pt_path = os.path.join(STAGING_DIR, f"run_{run_id}", f"boundary_{run_id}.pt")
    if os.path.exists(pt_path):
        print(f"[{run_id:03d}] already staged — skip")
        return True

    vtp_path = os.path.join(tmp_dir, f"boundary_{run_id}.vtp")
    try:
        print(f"[{run_id:03d}] downloading ...", end=" ", flush=True)
        if not download_vtp(run_id, vtp_path, token):
            print("NOT FOUND")
            return False
        print(f"done ({os.path.getsize(vtp_path)/1024**2:.0f} MB)")

        coords, targets             = process_vtp(vtp_path, run_id)
        coords_n, targets, idx, mu, sigma = sample_and_normalise(coords, targets, run_id)

        os.makedirs(os.path.dirname(pt_path), exist_ok=True)
        torch.save(make_pt(coords_n, targets, idx, mu, sigma, run_id), pt_path)
        print(f"[{run_id:03d}] saved ({os.path.getsize(pt_path)/1024**2:.1f} MB)")
        return True

    except Exception as e:
        print(f"[{run_id:03d}] ERROR: {e}")
        return False

    finally:
        if os.path.exists(vtp_path):
            os.remove(vtp_path)


# ── Main ───────────────────────────────────────────────────────────────────────

def main():
    parser = argparse.ArgumentParser()
    parser.add_argument("--start", type=int, default=1)
    parser.add_argument("--end",   type=int, default=500)
    args = parser.parse_args()

    token = os.environ.get("HF_TOKEN")
    if not token:
        sys.exit("Set HF_TOKEN environment variable first.")

    os.makedirs(STAGING_DIR, exist_ok=True)
    tmp_dir = tempfile.mkdtemp(prefix="drivaerml_")

    processed, skipped, failed = [], [], []

    try:
        for run_id in range(args.start, args.end + 1):
            if run_id in MISSING_RUNS:
                skipped.append(run_id)
                continue
            (processed if process_run(run_id, token, tmp_dir) else failed).append(run_id)
    except KeyboardInterrupt:
        print("\nInterrupted.")
    finally:
        shutil.rmtree(tmp_dir, ignore_errors=True)
        print(f"\nDone — processed: {len(processed)}  skipped: {len(skipped)}  failed: {len(failed)}")
        if failed:
            print(f"Failed IDs: {failed}")


if __name__ == "__main__":
    main()