"""Download the ONNX models for Phase A (semantic embeddings + LM detectors).

  models/minilm/      all-MiniLM-L6-v2  (semantic paraphrase signal S2)
  models/gpt2/        GPT-2 124M quantized   (Binoculars observer + perplexity)
  models/distilgpt2/  distilGPT-2 quantized  (Binoculars performer)

All quantized int8 — total ~250MB, CPU-friendly, no torch.
"""
import os
import sys

import requests

ROOT = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
MODELS = os.path.join(ROOT, "models")
UA = {"User-Agent": "plagcheck-edu/0.1"}

HF = "https://huggingface.co"
DOWNLOADS = [
    # (repo, remote file, local dir, local name; first existing alt wins)
    ("sentence-transformers/all-MiniLM-L6-v2",
     ["onnx/model_quint8_avx2.onnx", "onnx/model.onnx"],
     "minilm", "model.onnx"),
    ("sentence-transformers/all-MiniLM-L6-v2",
     ["tokenizer.json"], "minilm", "tokenizer.json"),
    ("Xenova/gpt2",
     ["onnx/decoder_model_quantized.onnx", "onnx/decoder_model.onnx"],
     "gpt2", "model.onnx"),
    ("Xenova/gpt2", ["tokenizer.json"], "gpt2", "tokenizer.json"),
    ("Xenova/distilgpt2",
     ["onnx/decoder_model_quantized.onnx", "onnx/decoder_model.onnx"],
     "distilgpt2", "model.onnx"),
]


def fetch(repo, remote_alts, subdir, name):
    dest_dir = os.path.join(MODELS, subdir)
    os.makedirs(dest_dir, exist_ok=True)
    dest = os.path.join(dest_dir, name)
    if os.path.exists(dest) and os.path.getsize(dest) > 10_000:
        print(f"[skip] {subdir}/{name} already present "
              f"({os.path.getsize(dest)/1e6:.1f} MB)")
        return True
    for remote in remote_alts:
        url = f"{HF}/{repo}/resolve/main/{remote}"
        try:
            r = requests.get(url, headers=UA, stream=True, timeout=60)
            if r.status_code != 200:
                print(f"[miss] {url} -> HTTP {r.status_code}")
                continue
            total = int(r.headers.get("content-length") or 0)
            done = 0
            tmp = dest + ".part"
            with open(tmp, "wb") as f:
                for chunk in r.iter_content(1 << 20):
                    f.write(chunk)
                    done += len(chunk)
                    if total:
                        pct = 100 * done / total
                        print(f"\r[get ] {subdir}/{name} {pct:5.1f}% "
                              f"({done/1e6:.0f}/{total/1e6:.0f} MB)",
                              end="", flush=True)
            print()
            os.replace(tmp, dest)
            print(f"[done] {subdir}/{name} <- {remote} "
                  f"({os.path.getsize(dest)/1e6:.1f} MB)")
            return True
        except requests.RequestException as exc:
            print(f"[fail] {url}: {exc}")
    return False


if __name__ == "__main__":
    ok = True
    for repo, alts, subdir, name in DOWNLOADS:
        ok = fetch(repo, alts, subdir, name) and ok
    print("ALL MODELS READY" if ok else "SOME MODELS MISSING")
    sys.exit(0 if ok else 1)