#!/usr/bin/env python3

"""
This CGI script logs the visitor's IP address and timestamp to a CSV file each time it is accessed.
It then returns a 1x1 transparent GIF image.
In index.html, this script is included as an image to track visits.
<img src="/~edchen93/cgi-bin/log_visit.py" width="1" height="1" alt="">
"""

import datetime
import os
import sys

ip = os.environ.get("REMOTE_ADDR", "unknown")
ts = datetime.datetime.now(datetime.timezone.utc).isoformat()

#[1] Use absolute path based on user's home directory on Athena
script_dir = os.path.dirname(os.path.abspath(__file__))
log_file = os.path.join(script_dir, "visit_log.csv")

try:
    with open(log_file, "a") as f:
        f.write(f'{ts},{ip}\n')
except Exception:
    pass  # Silently fail if logging doesn't work, still return the image

#[2] Return HTTP header and 1x1 transparent GIF image (all binary output)
# 1x1 transparent GIF
gif_data = bytes([
    0x47, 0x49, 0x46, 0x38, 0x39, 0x61, 0x01, 0x00, 0x01, 0x00,
    0x80, 0x00, 0x00, 0xFF, 0xFF, 0xFF, 0x00, 0x00, 0x00, 0x21,
    0xF9, 0x04, 0x01, 0x00, 0x00, 0x00, 0x00, 0x2C, 0x00, 0x00,
    0x00, 0x00, 0x01, 0x00, 0x01, 0x00, 0x00, 0x02, 0x01, 0x44,
    0x00, 0x3B
])

# Write headers and body as binary to avoid encoding issues
sys.stdout.buffer.write(b"Content-Type: image/gif\r\n")
sys.stdout.buffer.write(b"Content-Length: 43\r\n")
sys.stdout.buffer.write(b"\r\n")
sys.stdout.buffer.write(gif_data)