Jarian Cottingham
5c23a347ad
Reviewed-on: https://git.example.com/jarianc/NASAImageDownloader/pulls/14
305 lines
9.7 KiB
Python
305 lines
9.7 KiB
Python
#!/usr/bin/env python3
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"""
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NASA image downloader.
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The script queries NASA’s public “Image and Video Library” API for
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all images between a start and an end date, downloads each image
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to the *images* directory and writes a JSON file with the API
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metadata next to it. The JSON file is named
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`index‑<nasa_id>.json`, where `<nasa_id>` is the unique ID returned
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by the API.
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Now the images are fetched via the asset endpoint so the highest‑resolution
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image is downloaded. See the example at the top of this repository for
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the asset‑based approach.
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Designed to be run as a nightly daemon or cron job – it keeps a
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local record of the last successful run date, so a subsequent
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execution will automatically pick up new images and re‑write the
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metadata for any images that may have been updated.
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Features
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--------
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* idempotent – already‑downloaded images are skipped
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* optional time‑budget (max 2 h per run)
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* simple state file (`last_run.txt`) stores the end date of the last run
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* separate `images/` and `metadata/` directories
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* graceful error handling – failures are printed but do not stop the whole run
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Usage
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-----
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```text
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python downloader.py [--start YYYY-MM-DD] [--end YYYY-MM-DD]
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```
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If `--start` is omitted, the script reads the date from
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`last_run.txt`; if that file does not exist it defaults to three
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days ago. `--end` defaults to today.
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Dependencies
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-------------
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* requests
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"""
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import argparse
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import datetime
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import json
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import os
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import re
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import sys
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import time
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from pathlib import Path
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from typing import Dict, List
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import requests
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try:
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from tqdm import tqdm
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except ImportError:
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def tqdm(iterable, *args, **kwargs):
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return iterable
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# ------------------------------------------------------------------
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# Configuration
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# ------------------------------------------------------------------
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API_SEARCH_URL = "https://images-api.nasa.gov/search"
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API_ASSET_URL = "https://images-api.nasa.gov/asset"
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IMG_DIR = Path("images")
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META_DIR = Path("metadata")
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STATE_FILE = Path("last_run.txt")
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MAX_RUN_TIME = 4 * 60 * 60 # 4 hours in seconds
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# Ensure the output directories exist
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IMG_DIR.mkdir(parents=True, exist_ok=True)
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META_DIR.mkdir(parents=True, exist_ok=True)
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# ------------------------------------------------------------------
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# Helpers
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# ------------------------------------------------------------------
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def parse_args() -> argparse.Namespace:
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"""Parse CLI arguments."""
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parser = argparse.ArgumentParser(
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description="Download NASA images for a date range"
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)
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parser.add_argument(
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"--start",
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type=str,
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help="Start date (YYYY-MM-DD). If omitted, uses date stored in last_run.txt.",
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)
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parser.add_argument(
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"--end",
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type=str,
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help="End date (YYYY-MM-DD). Defaults to today.",
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)
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parser.add_argument(
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"--output",
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type=str,
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default=".",
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help="Base directory where images/ and metadata/ folders will be created. Default is the current working directory.",
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)
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return parser.parse_args()
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def load_state() -> datetime.datetime:
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"""Return the date stored in STATE_FILE or default to 3 days ago."""
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if STATE_FILE.exists():
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try:
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date_str = STATE_FILE.read_text().strip()
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return datetime.datetime.strptime(date_str, "%Y-%m-%d")
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except Exception:
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pass
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# default to 3 days ago UTC
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return datetime.datetime.utcnow() - datetime.timedelta(days=3)
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def save_state(end_date: datetime.datetime) -> None:
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"""Persist the last successful run date."""
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STATE_FILE.write_text(end_date.strftime("%Y-%m-%d"))
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def fetch_items(start: datetime.datetime, end: datetime.datetime) -> List[Dict]:
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"""
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Pull all image items from the NASA API in the given date range.
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The API paginates results; we loop until a page returns no items.
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Returns the raw ``items`` list from the API.
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"""
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items: List[Dict] = []
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page = 1
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while True:
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params = {
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"media_type": "image",
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"page": page,
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"year_start": start.year,
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"year_end": end.year,
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}
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try:
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r = requests.get(API_SEARCH_URL, params=params, timeout=20)
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r.raise_for_status()
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data = r.json()
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except Exception as e:
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print(f"API request failed: {e}", file=sys.stderr)
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break
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batch = data.get("collection", {}).get("items", [])
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if not batch or len(batch) == 0:
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break
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items.extend(batch)
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page += 1
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# Filter by the exact date range
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filtered = []
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for itm in items:
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d = itm.get("data", [{}])[0]
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iso = d.get("date_created") or d.get("date")
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if not iso:
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continue
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try:
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# Accept ISO format with or without timezone suffix
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dt = datetime.datetime.fromisoformat(iso.rstrip("Z"))
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except Exception:
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continue
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if start <= dt <= end:
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filtered.append(itm)
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return filtered
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def download_file(url: str, dest: Path) -> bool:
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"""Stream‑download the file at *url* to *dest* if it does not already exist."""
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if dest.exists():
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return False
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try:
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with requests.get(url, stream=True, timeout=30) as r:
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r.raise_for_status()
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with dest.open("wb") as f:
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for chunk in r.iter_content(chunk_size=8192):
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f.write(chunk)
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return True
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except Exception as e:
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raise RuntimeError(f"Download error for {url}: {e}") from e
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def sanitize_filename(name: str) -> str:
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"""Sanitize a string for use as a filename, preventing path traversal."""
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# Strip path separators and parent directory references
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sanitized = re.sub(r'[\/\\:\*\?"<>|]', "_", name)
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sanitized = re.sub(r"^\.{1,2}($|_)", "item_", sanitized)
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# Collapse multiple underscores
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sanitized = re.sub(r"_+", "_", sanitized)
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return sanitized.strip(".") or "item"
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def save_metadata(item: Dict, dest: Path) -> None:
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"""Persist the full API item as formatted JSON."""
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with dest.open("w", encoding="utf-8") as f:
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json.dump(item, f, ensure_ascii=False, indent=2)
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# ------------------------------------------------------------------
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# Main logic
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# ------------------------------------------------------------------
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def main() -> None:
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args = parse_args()
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# Resolve output base directory and validate it is safe
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base_dir = Path(args.output).resolve()
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# Prevent writing to system-critical paths
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_BLOCKED_PREFIXES = {
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str(Path(p).resolve())
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for p in ("/etc", "/usr", "/bin", "/sbin", "/boot", "/dev", "/proc", "/sys")
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}
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base_str = str(base_dir)
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if base_str == "/" or any(
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base_str == blocked or base_str.startswith(blocked + "/")
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for blocked in _BLOCKED_PREFIXES
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):
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print(
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f"Error: --output cannot point to system directory: {base_dir}",
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file=sys.stderr,
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)
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sys.exit(1)
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global IMG_DIR, META_DIR, STATE_FILE
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IMG_DIR = base_dir / "images"
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META_DIR = base_dir / "metadata"
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STATE_FILE = base_dir / "last_run.txt"
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IMG_DIR.mkdir(parents=True, exist_ok=True)
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META_DIR.mkdir(parents=True, exist_ok=True)
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start_date = (
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datetime.datetime.strptime(args.start, "%Y-%m-%d")
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if args.start
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else load_state()
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)
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end_date = (
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datetime.datetime.strptime(args.end, "%Y-%m-%d")
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if args.end
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else datetime.datetime.utcnow()
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)
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if start_date > end_date:
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print("Error: start date must be <= end date", file=sys.stderr)
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sys.exit(1)
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print(f"Fetching NASA image metadata from {start_date.date()} to {end_date.date()}")
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items = fetch_items(start_date, end_date)
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print(f"Found {len(items)} items")
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start_time = time.time()
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for idx, item in enumerate(tqdm(items, desc="Downloading"), start=1):
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data = item.get("data", [{}])[0]
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raw_nasa_id = data.get("nasa_id") or data.get("title", f"item_{idx}")
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nasa_id = sanitize_filename(str(raw_nasa_id))
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# ------------------------------------------------------------------
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# Asset lookup: fetch high‑resolution image URL
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# ------------------------------------------------------------------
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asset_url = f"{API_ASSET_URL}/{raw_nasa_id}"
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try:
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asset_resp = requests.get(asset_url, timeout=20)
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asset_resp.raise_for_status()
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assets = asset_resp.json()
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# Choose the first asset – usually the highest quality
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asset_href = assets.get("collection", {}).get("items", [{}])[0].get("href")
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if not asset_href:
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print(f"[{idx}] No asset link for item {nasa_id}", file=sys.stderr)
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continue
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except Exception as e:
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print(f"[{idx}] Failed asset lookup for {nasa_id}: {e}", file=sys.stderr)
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continue
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filename = sanitize_filename(Path(asset_href).name)
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image_path = IMG_DIR / filename
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meta_path = META_DIR / f"index-{nasa_id}.json"
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try:
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downloaded = download_file(asset_href, image_path)
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except Exception as e:
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print(f"[{idx}] Failed download {asset_href}: {e}", file=sys.stderr)
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continue
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# Persist metadata
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try:
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save_metadata(item, meta_path)
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except Exception as e:
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print(
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f"[{idx}] Failed to write metadata for {nasa_id}: {e}", file=sys.stderr
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)
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elapsed = time.time() - start_time
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if downloaded:
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time.sleep(3)
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if elapsed > MAX_RUN_TIME:
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print("Maximum runtime exceeded, stopping early")
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break
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# Persist the last successful end date
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save_state(end_date)
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print("Download complete")
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if __name__ == "__main__":
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main()
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