#!/usr/bin/env python3
"""
Download large batches of PDF URLs into a local directory so they can be fed to
scripts/harvest_type3_fonts.py (or any other processing pipeline).

Usage examples:

    # Download every URL listed in pdf_urls.txt into tmp/type3-pdfs
    python scripts/download_pdf_samples.py \
        --urls-file pdf_urls.txt \
        --output-dir tmp/type3-pdfs

    # Mix inline URLs with a file and use 16 concurrent downloads
    python scripts/download_pdf_samples.py \
        --urls https://example.com/a.pdf https://example.com/b.pdf \
        --urls-file more_urls.txt \
        --output-dir tmp/type3-pdfs \
        --workers 16
"""

from __future__ import annotations

import argparse
import concurrent.futures
import hashlib
import os
import re
import sys
from pathlib import Path
from urllib.parse import unquote, urlparse

import requests


def parse_args() -> argparse.Namespace:
    parser = argparse.ArgumentParser(description="Bulk download PDF URLs.")
    parser.add_argument(
        "--urls",
        nargs="*",
        default=[],
        help="Inline list of PDF URLs (can be combined with --urls-file).",
    )
    parser.add_argument(
        "--urls-file",
        action="append",
        help="Text file containing one URL per line (can be repeated).",
    )
    parser.add_argument(
        "--output-dir",
        default="tmp/harvest-pdfs",
        help="Directory to store downloaded PDFs (default: %(default)s).",
    )
    parser.add_argument(
        "--workers",
        type=int,
        default=min(8, (os.cpu_count() or 4) * 2),
        help="Number of concurrent downloads (default: %(default)s).",
    )
    parser.add_argument(
        "--timeout",
        type=int,
        default=120,
        help="Per-request timeout in seconds (default: %(default)s).",
    )
    parser.add_argument(
        "--overwrite",
        action="store_true",
        help="Overwrite existing files (default: skip already downloaded PDFs).",
    )
    return parser.parse_args()


def load_urls(args: argparse.Namespace) -> list[str]:
    urls: list[str] = []
    seen: set[str] = set()

    def add(url: str) -> None:
        clean = url.strip()
        if not clean or clean.startswith("#"):
            return
        if clean not in seen:
            seen.add(clean)
            urls.append(clean)

    for url in args.urls:
        add(url)
    if args.urls_file:
        for file in args.urls_file:
            path = Path(file)
            if not path.exists():
                print(f"[WARN] URL file not found: {file}", file=sys.stderr)
                continue
            with path.open("r", encoding="utf-8") as handle:
                for line in handle:
                    add(line)
    if not urls:
        raise SystemExit("No URLs supplied. Use --urls and/or --urls-file.")
    return urls


def sanitize_filename(name: str) -> str:
    return re.sub(r"[^A-Za-z0-9._-]+", "_", name).strip("_") or "download"


def build_filename(url: str, output_dir: Path) -> Path:
    parsed = urlparse(url)
    candidate = Path(unquote(parsed.path)).name
    if not candidate:
        candidate = "download.pdf"
    candidate = sanitize_filename(candidate)
    if not candidate.lower().endswith(".pdf"):
        candidate += ".pdf"
    target = output_dir / candidate
    if not target.exists():
        return target
    stem = target.stem
    suffix = target.suffix
    digest = hashlib.sha1(url.encode("utf-8")).hexdigest()[:8]
    return output_dir / f"{stem}-{digest}{suffix}"


def download_pdf(
    url: str,
    output_dir: Path,
    timeout: int,
    overwrite: bool,
) -> tuple[str, Path | None, str | None]:
    try:
        dest = build_filename(url, output_dir)
        if dest.exists() and not overwrite:
            return url, dest, "exists"

        response = requests.get(url, stream=True, timeout=timeout)
        response.raise_for_status()

        content_type = response.headers.get("Content-Type", "").lower()
        if "pdf" not in content_type and not url.lower().endswith(".pdf"):
            # Peek into the first bytes to be safe
            peek = response.raw.read(5, decode_content=True)
            if not peek.startswith(b"%PDF"):
                return (
                    url,
                    None,
                    f"Skipping non-PDF content-type ({content_type or 'unknown'})",
                )
            content = peek + response.content[len(peek) :]
        else:
            content = response.content

        output_dir.mkdir(parents=True, exist_ok=True)
        dest.write_bytes(content)
        return url, dest, None
    except Exception as exc:  # pylint: disable=broad-except
        return url, None, str(exc)


def main() -> None:
    args = parse_args()
    urls = load_urls(args)
    output_dir = Path(args.output_dir).resolve()
    output_dir.mkdir(parents=True, exist_ok=True)

    print(f"Downloading {len(urls)} PDFs to {output_dir} using {args.workers} workers...")

    successes = 0
    skipped = 0
    failures: list[tuple[str, str]] = []

    with concurrent.futures.ThreadPoolExecutor(max_workers=args.workers) as executor:
        future_to_url = {
            executor.submit(download_pdf, url, output_dir, args.timeout, args.overwrite): url for url in urls
        }
        for future in concurrent.futures.as_completed(future_to_url):
            url = future_to_url[future]
            result_url, path, error = future.result()
            if error == "exists":
                skipped += 1
                print(f"[SKIP] {url} (already downloaded)")
            elif error:
                failures.append((result_url, error))
                print(f"[FAIL] {url} -> {error}", file=sys.stderr)
            else:
                successes += 1
                print(f"[OK] {url} -> {path}")

    print()
    print(f"Completed. Success: {successes}, Skipped: {skipped}, Failures: {len(failures)}")
    if failures:
        print("Failures:")
        for url, error in failures:
            print(f"  {url} -> {error}")


if __name__ == "__main__":
    main()