#!/usr/bin/env python3
"""Download assets to structured folder per AGENTS rules.

Usage:
  python download.py --page-id j4lexk --title "My Page" --urls urls.txt --sources source_urls.txt

- Creates `downloads/<date>-<title>-<page-id>/media/` and stores downloads there (date format `YYYYMMDD`, generated by the script).
- Saves source URLs provided by user into `downloads/<date>-<title>-<page-id>/urls.txt` (input file given by `--sources`).
- Cleans filenames (strip query strings and `@!` size tokens; keep/guess extensions).
- Batch downloads, then deletes 0-byte files, compares against planned URLs, retries missing up to 2 times, and reports any remaining failures. Deletes the `--urls` input file when finished.
"""

import argparse
import os
import pathlib
import sys
import time
from typing import Dict, List, Optional, Tuple

import mimetypes
import urllib.parse
import requests

DATE_FMT = "%Y%m%d"

# Default retry policy
MAX_RETRIES = 2
TIMEOUT = 30


def parse_args() -> argparse.Namespace:
    parser = argparse.ArgumentParser(
        description="Batch download assets per AGENTS rules"
    )
    parser.add_argument("--page-id", required=True, help="Page ID, e.g. j4lexk")
    parser.add_argument("--title", required=True, help="Page title for folder naming")
    parser.add_argument(
        "--urls", required=True, help="Path to text file with asset URLs (one per line)"
    )
    parser.add_argument(
        "--sources",
        required=True,
        help="Path to text file containing source page URLs to record (will be saved as urls.txt)",
    )
    parser.add_argument(
        "--retries", type=int, default=MAX_RETRIES, help="Retry count for missing files"
    )
    parser.add_argument(
        "--timeout", type=int, default=TIMEOUT, help="Request timeout seconds"
    )
    return parser.parse_args()


def load_lines(path: str) -> List[str]:
    with open(path, "r", encoding="utf-8") as f:
        return [ln.strip() for ln in f if ln.strip()]


def ensure_dir(path: pathlib.Path) -> None:
    path.mkdir(parents=True, exist_ok=True)


def sanitize_filename(url: str, content_type: Optional[str]) -> str:
    """Strip query/size tokens and ensure extension."""
    parsed = urllib.parse.urlparse(url)
    basename = os.path.basename(parsed.path)
    # remove query-derived size tokens like @!user_image_800x1
    if "@!" in basename:
        basename = basename.split("@!", 1)[0]
    # fallback name
    if not basename:
        basename = "file"
    root, ext = os.path.splitext(basename)
    if not ext:
        ext = guess_extension(content_type)
    return root + ext


def guess_extension(content_type: Optional[str]) -> str:
    if content_type:
        ext = mimetypes.guess_extension(content_type.split(";")[0].strip())
        if ext:
            return ext
    return ".bin"


def unique_name(base: pathlib.Path) -> pathlib.Path:
    if not base.exists():
        return base
    stem = base.stem
    suffix = base.suffix
    parent = base.parent
    idx = 1
    while True:
        candidate = parent / f"{stem}_{idx}{suffix}"
        if not candidate.exists():
            return candidate
        idx += 1


def download_one(
    url: str, dest_dir: pathlib.Path, timeout: int
) -> Tuple[bool, Optional[str]]:
    try:
        resp = requests.get(url, timeout=timeout, stream=True)
        if resp.status_code != 200:
            return False, f"HTTP {resp.status_code}"
        fname = sanitize_filename(url, resp.headers.get("Content-Type"))
        target = unique_name(dest_dir / fname)
        with open(target, "wb") as f:
            for chunk in resp.iter_content(chunk_size=8192):
                if chunk:
                    f.write(chunk)
        return True, None
    except Exception as exc:  # pylint: disable=broad-except
        return False, str(exc)


def delete_zero_byte_files(dest_dir: pathlib.Path) -> List[str]:
    removed = []
    for p in dest_dir.glob("*"):
        if p.is_file() and p.stat().st_size == 0:
            removed.append(p.name)
            p.unlink()
    return removed


def plan_downloads(urls: List[str]) -> Dict[str, str]:
    """Return mapping of url -> planned base filename (sanitized) for verification."""
    plan = {}
    for u in urls:
        plan[u] = sanitize_filename(u, None)
    return plan


def verify_missing(dest_dir: pathlib.Path, plan: Dict[str, str]) -> List[str]:
    existing = {p.name for p in dest_dir.glob("*") if p.is_file()}
    missing = []
    for url, fname in plan.items():
        # consider potential uniqueness suffix; check prefix match
        if fname not in existing and not any(
            name.startswith(fname.rsplit(".", 1)[0]) for name in existing
        ):
            missing.append(url)
    return missing


def save_source_urls(dest_root: pathlib.Path, sources_path: pathlib.Path) -> None:
    ensure_dir(dest_root)
    sources = load_lines(str(sources_path))
    with open(dest_root / "urls.txt", "w", encoding="utf-8") as f:
        for line in sources:
            f.write(line + "\n")


def main() -> None:
    args = parse_args()
    today = time.strftime(DATE_FMT)
    dest_root = pathlib.Path("downloads") / f"{today}-{args.title}-{args.page_id}"
    media_dir = dest_root / "media"
    ensure_dir(media_dir)

    urls_path = pathlib.Path(args.urls)
    urls = load_lines(args.urls)
    plan = plan_downloads(urls)

    # initial batch download
    for url in urls:
        ok, err = download_one(url, media_dir, args.timeout)
        if not ok:
            print(f"WARN: download failed for {url}: {err}", file=sys.stderr)
        time.sleep(0.05)  # mild pacing

    removed = delete_zero_byte_files(media_dir)
    if removed:
        print(f"Removed zero-byte files: {removed}")

    missing = verify_missing(media_dir, plan)
    attempts = 0
    while missing and attempts < args.retries:
        attempts += 1
        print(f"Retry round {attempts}: missing {len(missing)} files")
        still_missing = []
        for url in missing:
            ok, err = download_one(url, media_dir, args.timeout)
            if not ok:
                print(f"WARN: retry failed for {url}: {err}", file=sys.stderr)
                still_missing.append(url)
        removed_retry = delete_zero_byte_files(media_dir)
        if removed_retry:
            print(f"Removed zero-byte files after retry: {removed_retry}")
        missing = (
            verify_missing(media_dir, {u: plan[u] for u in still_missing})
            if still_missing
            else []
        )

    if missing:
        print("FAILED to fetch these URLs after retries:", file=sys.stderr)
        for url in missing:
            print(url, file=sys.stderr)
    else:
        print("All planned files downloaded.")

    save_source_urls(dest_root, pathlib.Path(args.sources))
    print(f"Saved source URLs to {dest_root / 'urls.txt'}")

    try:
        urls_path.unlink()
        print(f"Removed input file: {urls_path}")
    except Exception as exc:  # pylint: disable=broad-except
        print(f"WARN: failed to remove input file {urls_path}: {exc}", file=sys.stderr)


if __name__ == "__main__":
    main()