#!/usr/bin/env python3
# /// script
# requires-python = ">=3.11"
# dependencies = [
#   "datasets>=3.0,<4",
#   "transformers>=4.51,<5",
#   "pyarrow>=17.0,<19",
# ]
# ///
"""
Load the prefill dataset and generate example prompts for each task type.

Usage:
    uv run generate_examples.py                          # from local files
    uv run generate_examples.py --repo di2ox3/prefill-dataset  # from HuggingFace
"""
from __future__ import annotations

import argparse
import json
import textwrap
from pathlib import Path

import pyarrow.parquet as pq
from transformers import AutoTokenizer


def load_tables(repo: str | None):
    if repo:
        from datasets import load_dataset
        docs = load_dataset(repo, data_files="data/documents.parquet", split="train")
        tasks = load_dataset(repo, data_files="data/tasks.parquet", split="train")
        trans = load_dataset(repo, data_files="data/translations.parquet", split="train")
        return docs.to_pandas(), tasks.to_pandas(), trans.to_pandas()
    else:
        base = Path(__file__).parent / "output"
        docs = pq.read_table(base / "documents.parquet").to_pandas()
        tasks = pq.read_table(base / "tasks.parquet").to_pandas()
        trans = pq.read_table(base / "translations.parquet").to_pandas()
        return docs, tasks, trans


def show_summary(docs, tasks, trans):
    print("=" * 60)
    print("DATASET SUMMARY")
    print("=" * 60)
    total_tokens = docs["token_count"].sum()
    print(f"Documents: {len(docs)}")
    print(f"Total tokens: {total_tokens:,} ({total_tokens / 1e6:.1f}M)")
    print(f"Tasks: {len(tasks)}")
    print(f"Translations: {len(trans)}")
    print()
    print("Documents by source:")
    for src, group in docs.groupby("source"):
        print(f"  {src}: {len(group)} docs, {group['token_count'].sum():,} tokens")
    print()
    print("Tasks by type:")
    for tt, group in tasks.groupby("task_type"):
        print(f"  {tt}: {len(group)}")
    print()
    print("Translations by language:")
    for lang, group in trans.groupby("target_language"):
        print(f"  {lang}: {len(group)}")


def show_qa_example(docs, tasks):
    qa_tasks = tasks[tasks.task_type == "qa"]
    if qa_tasks.empty:
        print("No QA tasks found.")
        return
    task = qa_tasks.iloc[0]
    doc = docs[docs.doc_id == task.doc_id].iloc[0]
    answers = json.loads(task.answer)

    print()
    print("-" * 60)
    print("EXAMPLE: Question Answering")
    print("-" * 60)
    print(f"Document: {doc.title} ({doc.token_count:,} tokens)")
    print(f"Question: {task.question}")
    print(f"Answers: {answers}")
    print(f"Context (first 300 chars): {doc.text[:300]}...")


def show_translation_example(docs, tasks, trans):
    tr_tasks = tasks[tasks.task_type == "translation"]
    if tr_tasks.empty:
        print("No translation tasks found.")
        return
    task = tr_tasks.iloc[0]
    doc = docs[docs.doc_id == task.doc_id].iloc[0]
    meta = json.loads(task.metadata)
    tr_row = trans[trans.doc_id == task.doc_id]

    print()
    print("-" * 60)
    print("EXAMPLE: Translation")
    print("-" * 60)
    print(f"Document: {doc.title} ({doc.token_count:,} tokens)")
    print(f"Target language: {meta.get('target_language', '?')}")
    print(f"Passage tokens: {meta.get('passage_token_start')}-{meta.get('passage_token_end')}")
    print(f"Question (truncated):")
    print(textwrap.shorten(task.question, width=300, placeholder="..."))
    if not tr_row.empty:
        tr = tr_row.iloc[0]
        print(f"Translation text (first 300 chars): {tr.target_text[:300]}...")


def show_retrieval_example(docs, tasks):
    ret_tasks = tasks[tasks.task_type == "retrieval"]
    if ret_tasks.empty:
        print("No retrieval tasks found.")
        return
    task = ret_tasks.iloc[0]
    doc = docs[docs.doc_id == task.doc_id].iloc[0]
    meta = json.loads(task.metadata)
    answer_text = json.loads(task.answer)

    print()
    print("-" * 60)
    print("EXAMPLE: Retrieval")
    print("-" * 60)
    print(f"Document: {doc.title} ({doc.token_count:,} tokens)")
    print(f"Token range: {meta.get('passage_token_start')}-{meta.get('passage_token_end')}")
    print(f"Question: {textwrap.shorten(task.question, width=200, placeholder='...')}")
    print(f"Answer (first 200 chars): {answer_text[:200]}...")


def verify_offsets(docs):
    """Spot-check that char_offsets correctly map tokens back to text."""
    print()
    print("-" * 60)
    print("OFFSET VERIFICATION (first 3 docs, first 10 tokens each)")
    print("-" * 60)
    tokenizer = AutoTokenizer.from_pretrained("Qwen/Qwen3-8B")

    for i in range(min(3, len(docs))):
        doc = docs.iloc[i]
        text = doc.text
        offsets = doc.char_offsets
        token_ids = doc.token_ids
        print(f"\n  Doc: {doc.doc_id} ({doc.token_count:,} tokens)")
        for j in range(min(10, len(offsets))):
            start = offsets[j]
            end = offsets[j + 1] if j + 1 < len(offsets) else len(text)
            span = text[start:end]
            decoded = tokenizer.decode([token_ids[j]])
            match = "OK" if span.strip() == decoded.strip() else "~"
            print(f"    [{j:3d}] offset={start:6d} span={span!r:30s} decoded={decoded!r:30s} {match}")


def main():
    parser = argparse.ArgumentParser(description="Explore the prefill dataset")
    parser.add_argument("--repo", type=str, default=None,
                        help="HuggingFace repo ID (e.g. di2ox3/prefill-dataset)")
    parser.add_argument("--verify", action="store_true",
                        help="Run offset verification (loads tokenizer)")
    args = parser.parse_args()

    docs, tasks, trans = load_tables(args.repo)

    show_summary(docs, tasks, trans)
    show_qa_example(docs, tasks)
    show_translation_example(docs, tasks, trans)
    show_retrieval_example(docs, tasks)

    if args.verify:
        verify_offsets(docs)

    print()
    print("=" * 60)
    print("Done.")


if __name__ == "__main__":
    main()