#!/usr/bin/env python3
"""Build a training-oriented source mix from existing Polish DynaWord parquets.

The raw corpus is provenance-first. This script creates a training view with:
- temperature/sqrt sampling by source,
- a hard cap for legal/parliamentary sources,
- an optional high-quality final-phase manifest,
- optional sampled parquet materialization.
"""

from __future__ import annotations

import argparse
import json
import math
import random
from pathlib import Path

import pyarrow as pa
import pyarrow.compute as pc
import pyarrow.parquet as pq


def load_config(path: Path) -> dict:
    return json.loads(path.read_text(encoding="utf-8"))


def source_inventory(data_root: Path) -> dict[str, dict]:
    inventory = {}
    for parquet_path in sorted((data_root / "data").glob("*/*.parquet")):
        source = parquet_path.parent.name
        stats_path = parquet_path.with_name(f"{source}.stats.json")
        docs = None
        tokens = None
        if stats_path.exists():
            stats = json.loads(stats_path.read_text(encoding="utf-8"))
            docs = int(stats.get("kept", 0))
            tokens = int(stats.get("tokens", 0))

        if not docs or not tokens:
            pf = pq.ParquetFile(parquet_path)
            docs = pf.metadata.num_rows
            tokens = 0
            for rg in range(pf.num_row_groups):
                tbl = pf.read_row_group(rg, columns=["token_count"])
                tokens += int(pc.sum(tbl["token_count"]).as_py())

        inventory[source] = {
            "path": str(parquet_path),
            "docs": docs,
            "tokens": tokens,
        }
    return inventory


def normalize(weights: dict[str, float], total: float = 1.0) -> dict[str, float]:
    denom = sum(weights.values())
    if denom <= 0:
        return {k: 0.0 for k in weights}
    return {k: v / denom * total for k, v in weights.items()}


def compute_mix(inventory: dict[str, dict], config: dict) -> dict[str, dict]:
    alpha = float(config.get("temperature_alpha", 0.5))
    multipliers = config.get("source_multipliers", {})
    legal_sources = set(config.get("legal_sources", []))
    legal_cap = float(config.get("legal_cap_share", 0.15))

    base_weights = {}
    for source, meta in inventory.items():
        multiplier = float(multipliers.get(source, 1.0))
        base_weights[source] = math.pow(meta["tokens"], alpha) * multiplier

    legal_weights = {s: w for s, w in base_weights.items() if s in legal_sources}
    other_weights = {s: w for s, w in base_weights.items() if s not in legal_sources}
    raw_share = normalize(base_weights)
    raw_legal_share = sum(raw_share.get(s, 0.0) for s in legal_sources)

    if raw_legal_share > legal_cap and other_weights:
        legal_share = legal_cap
    else:
        legal_share = raw_legal_share
    other_share = max(0.0, 1.0 - legal_share)

    final_shares = {}
    final_shares.update(normalize(legal_weights, legal_share))
    final_shares.update(normalize(other_weights, other_share))

    mix = {}
    total_tokens = sum(meta["tokens"] for meta in inventory.values())
    for source, meta in inventory.items():
        raw_corpus_share = meta["tokens"] / total_tokens if total_tokens else 0.0
        target_share = final_shares.get(source, 0.0)
        mix[source] = {
            **meta,
            "raw_corpus_share": raw_corpus_share,
            "target_share": target_share,
            "sampling_multiplier": target_share / raw_corpus_share if raw_corpus_share else 0.0,
            "is_legal_capped": source in legal_sources,
        }
    return dict(sorted(mix.items()))


def add_token_targets(mix: dict[str, dict], token_budget: int | None) -> None:
    for meta in mix.values():
        target_tokens = int(round(meta["target_share"] * token_budget)) if token_budget else 0
        meta["target_tokens"] = target_tokens
        meta["sampling_probability"] = min(1.0, target_tokens / meta["tokens"]) if token_budget else 0.0


def write_report(mix: dict[str, dict], config: dict, out_path: Path, token_budget: int | None) -> None:
    legal_sources = set(config.get("legal_sources", []))
    raw_legal = sum(v["raw_corpus_share"] for k, v in mix.items() if k in legal_sources)
    target_legal = sum(v["target_share"] for k, v in mix.items() if k in legal_sources)
    lines = [
        "# Polish DynaWord training mix",
        "",
        f"- config: `{config.get('name', 'unnamed')}`",
        f"- temperature alpha: `{config.get('temperature_alpha', 0.5)}`",
        f"- legal/parliamentary raw share: `{raw_legal * 100:.2f}%`",
        f"- legal/parliamentary target share: `{target_legal * 100:.2f}%`",
    ]
    if token_budget:
        lines.append(f"- token budget: `{token_budget:,}`")
    lines.extend([
        "",
        "| source | raw tokens | raw share | target share | sampling multiplier | target tokens |",
        "|---|---:|---:|---:|---:|---:|",
    ])
    for source, meta in mix.items():
        lines.append(
            f"| `{source}` | {meta['tokens']:,} | {meta['raw_corpus_share'] * 100:.2f}% | "
            f"{meta['target_share'] * 100:.2f}% | {meta['sampling_multiplier']:.3f} | "
            f"{meta['target_tokens']:,} |"
        )

    final_phase_sources = config.get("final_phase_sources", [])
    final_phase_share = float(config.get("final_phase_share", 0.10))
    lines.extend([
        "",
        "## Final training phase",
        "",
        f"Reserve the last `{final_phase_share * 100:.0f}%` of training tokens for higher-quality sources:",
        "",
    ])
    for source in final_phase_sources:
        lines.append(f"- `{source}`")

    missing = config.get("target_missing_sources", [])
    if missing:
        lines.extend(["", "## Missing source classes for v0.3+", ""])
        for item in missing:
            lines.append(f"- {item}")

    out_path.parent.mkdir(parents=True, exist_ok=True)
    out_path.write_text("\n".join(lines) + "\n", encoding="utf-8")


def write_manifest(mix: dict[str, dict], out_path: Path) -> None:
    payload = {
        "sources": [
            {
                "source": source,
                "path": meta["path"],
                "tokens": meta["tokens"],
                "raw_corpus_share": meta["raw_corpus_share"],
                "target_share": meta["target_share"],
                "target_tokens": meta["target_tokens"],
                "sampling_probability": meta["sampling_probability"],
            }
            for source, meta in mix.items()
        ]
    }
    out_path.parent.mkdir(parents=True, exist_ok=True)
    out_path.write_text(json.dumps(payload, indent=2, ensure_ascii=False) + "\n", encoding="utf-8")


def sample_source(source: str, meta: dict, seed: int) -> pa.Table:
    rng = random.Random(f"{seed}:{source}")
    target = meta["target_tokens"]
    if target <= 0:
        return pa.table({})

    pf = pq.ParquetFile(meta["path"])
    batches = []
    sampled_tokens = 0
    probability = meta["sampling_probability"]
    for rg in range(pf.num_row_groups):
        tbl = pf.read_row_group(rg)
        keep = [rng.random() < probability for _ in range(tbl.num_rows)]
        if not any(keep):
            continue
        sampled = tbl.filter(pa.array(keep))
        batches.append(sampled)
        sampled_tokens += int(pc.sum(sampled["token_count"]).as_py())
        if sampled_tokens >= target:
            break

    return pa.concat_tables(batches, promote_options="default") if batches else pa.table({})


def write_sampled_parquet(mix: dict[str, dict], out_path: Path, seed: int) -> None:
    out_path.parent.mkdir(parents=True, exist_ok=True)
    writer = None
    try:
        for source, meta in mix.items():
            tbl = sample_source(source, meta, seed)
            if tbl.num_rows == 0:
                continue
            if writer is None:
                writer = pq.ParquetWriter(out_path, tbl.schema, compression="zstd")
            writer.write_table(tbl)
            print(f"{source}: wrote {tbl.num_rows:,} docs")
    finally:
        if writer is not None:
            writer.close()


def parse_args() -> argparse.Namespace:
    ap = argparse.ArgumentParser()
    ap.add_argument("--data-root", type=Path, default=Path("."))
    ap.add_argument("--config", type=Path, default=Path("configs/training_mix_v0_3.json"))
    ap.add_argument("--token-budget", type=int, default=None)
    ap.add_argument("--out-report", type=Path, default=Path("artifacts/training_mix_v0_3.md"))
    ap.add_argument("--out-manifest", type=Path, default=Path("artifacts/training_mix_v0_3.json"))
    ap.add_argument("--write-parquet", type=Path, default=None)
    ap.add_argument("--seed", type=int, default=13)
    return ap.parse_args()


def main() -> None:
    args = parse_args()
    config = load_config(args.config)
    inventory = source_inventory(args.data_root)
    mix = compute_mix(inventory, config)
    add_token_targets(mix, args.token_budget)
    write_report(mix, config, args.out_report, args.token_budget)
    write_manifest(mix, args.out_manifest)
    if args.write_parquet:
        if not args.token_budget:
            raise SystemExit("--write-parquet requires --token-budget")
        write_sampled_parquet(mix, args.write_parquet, args.seed)
    print(f"wrote: {args.out_report}")
    print(f"wrote: {args.out_manifest}")


if __name__ == "__main__":
    main()