import os, json, random
HERE = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
os.environ["HF_HOME"] = os.path.join(HERE, "hf_cache")

from datasets import load_dataset

OUT = os.path.join(HERE, "data", "sft_chat.jsonl")
N = 500
random.seed(0)

def main():
    ds = load_dataset("databricks/databricks-dolly-15k", split="train")
    idx = list(range(len(ds)))
    random.shuffle(idx)

    rows = []
    for i in idx:
        r = ds[i]
        instr, ctx, resp = r["instruction"].strip(), r["context"].strip(), r["response"].strip()
        if not instr or not resp:
            continue
        if len(resp) > 1200:            # keep seq length sane
            continue
        user = f"{instr}\n\n{ctx}" if ctx else instr
        rows.append({"messages": [{"role": "user", "content": user},
                                  {"role": "assistant", "content": resp}]})
        if len(rows) >= N:
            break

    with open(OUT, "w") as f:
        for r in rows:
            f.write(json.dumps(r) + "\n")
    print(f"wrote {len(rows)} chat examples -> {OUT}")
    print("sample user:", rows[0]["messages"][0]["content"][:80])

if __name__ == "__main__":
    main()