#!/usr/bin/env python3
"""Tokenize the corpus with the Polish BPE into modded-nanogpt/llm.c shards.
Single process: tokenizers' encode_batch parallelises across cores via Rust rayon
natively — NO mp.Pool (nesting mp.Pool x rayon oversubscribes and is ~4x slower).
Format: 256 int32 header [magic 20240520, version 1, ntok] + uint16 tokens.
Docs joined with <|endoftext|>; ~1/200 docs held out for validation."""
import glob, os, time
import numpy as np
import pyarrow.parquet as pq
from tokenizers import Tokenizer

TOKJSON = "/home/ubuntu/dynaword/polish_bpe_32k.json"
DATA = "/home/ubuntu/dynaword/data"
OUT = "/home/ubuntu/dynaword/shards"
SHARD = 100_000_000
VAL_EVERY = 200
CHUNK = 50_000           # docs per encode_batch call
os.makedirs(OUT, exist_ok=True)

def doc_stream():
    for f in sorted(glob.glob(f"{DATA}/*/*.parquet")):
        for b in pq.ParquetFile(f).iter_batches(columns=["text"], batch_size=2000):
            for x in b.column("text"):
                s = x.as_py()
                if s:
                    yield s

def write_shard(path, arr):
    h = np.zeros(256, dtype=np.int32); h[0] = 20240520; h[1] = 1; h[2] = len(arr)
    with open(path, "wb") as f:
        f.write(h.tobytes()); f.write(arr.tobytes())

def main():
    tok = Tokenizer.from_file(TOKJSON)
    EOT = tok.token_to_id("<|endoftext|>")
    print(f"EOT={EOT} | shard={SHARD:,} | val 1/{VAL_EVERY} | chunk={CHUNK}", flush=True)

    buf = np.empty(SHARD + 2_000_000, dtype=np.uint16); tn = 0; sidx = 0
    val = []
    di = 0; total = 0; t0 = time.time()
    chunk = []

    def flush_chunk():
        nonlocal tn, sidx, di, total
        if not chunk:
            return
        for e in tok.encode_batch(chunk):     # rayon -> all cores, single process
            ids = e.ids
            # EOT PREFIX (BOS before each doc) -> matches modded-nanogpt align_to_bos
            if di % VAL_EVERY == 0:
                val.append(EOT); val.extend(ids)
            else:
                buf[tn] = EOT; tn += 1
                m = len(ids)
                buf[tn:tn+m] = ids; tn += m
                if tn >= SHARD:
                    write_shard(f"{OUT}/polish_train_{sidx:06d}.bin", buf[:tn])
                    total += tn; sidx += 1; tn = 0
            di += 1
        chunk.clear()
        print(f"  {di:,} docs | {(total+tn)/1e9:.2f}B train tok | {len(val)/1e6:.1f}M val | {time.time()-t0:.0f}s", flush=True)

    for s in doc_stream():
        chunk.append(s)
        if len(chunk) >= CHUNK:
            flush_chunk()
    flush_chunk()
    if tn:
        write_shard(f"{OUT}/polish_train_{sidx:06d}.bin", buf[:tn]); total += tn; sidx += 1
    write_shard(f"{OUT}/polish_val_000000.bin", np.array(val, dtype=np.uint16))
    print(f"\nDONE: {sidx} train shards, {total:,} train tok, {len(val):,} val tok | "
          f"{di:,} docs | {time.time()-t0:.0f}s", flush=True)

if __name__ == "__main__":
    main()