#!/usr/bin/env python3
"""
ANAF Page Monitor - Simple hash-based change detection
Checks configured pages and reports changes via stdout
"""

import json
import hashlib
import urllib.request
import ssl
import os
from datetime import datetime
from pathlib import Path

SCRIPT_DIR = Path(__file__).parent
CONFIG_FILE = SCRIPT_DIR / "config.json"
HASHES_FILE = SCRIPT_DIR / "hashes.json"
LOG_FILE = SCRIPT_DIR / "monitor.log"

# SSL context that doesn't verify (some ANAF pages have cert issues)
SSL_CTX = ssl.create_default_context()
SSL_CTX.check_hostname = False
SSL_CTX.verify_mode = ssl.CERT_NONE

def log(msg):
    timestamp = datetime.now().strftime("%Y-%m-%d %H:%M:%S")
    with open(LOG_FILE, "a") as f:
        f.write(f"[{timestamp}] {msg}\n")

def load_json(path, default=None):
    try:
        with open(path) as f:
            return json.load(f)
    except:
        return default if default is not None else {}

def save_json(path, data):
    with open(path, "w") as f:
        json.dump(data, f, indent=2)

def fetch_page(url, timeout=30):
    """Fetch page content"""
    try:
        req = urllib.request.Request(url, headers={
            'User-Agent': 'Mozilla/5.0 (compatible; ANAF-Monitor/1.0)'
        })
        with urllib.request.urlopen(req, timeout=timeout, context=SSL_CTX) as resp:
            return resp.read()
    except Exception as e:
        log(f"ERROR fetching {url}: {e}")
        return None

def compute_hash(content):
    """Compute SHA256 hash of content"""
    return hashlib.sha256(content).hexdigest()

def check_page(page, hashes):
    """Check a single page for changes. Returns change info or None."""
    page_id = page["id"]
    name = page["name"]
    url = page["url"]
    
    content = fetch_page(url)
    if content is None:
        return None
    
    new_hash = compute_hash(content)
    old_hash = hashes.get(page_id)
    
    if old_hash is None:
        log(f"INIT: {page_id} - storing initial hash")
        hashes[page_id] = new_hash
        return None
    
    if new_hash != old_hash:
        log(f"CHANGE DETECTED: {page_id} - {name}")
        log(f"  URL: {url}")
        log(f"  Old hash: {old_hash}")
        log(f"  New hash: {new_hash}")
        hashes[page_id] = new_hash
        return {"id": page_id, "name": name, "url": url}
    
    log(f"OK: {page_id} - no changes")
    return None

def main():
    log("=== Starting ANAF monitor check ===")
    
    config = load_json(CONFIG_FILE, {"pages": []})
    hashes = load_json(HASHES_FILE, {})
    
    changes = []
    for page in config["pages"]:
        change = check_page(page, hashes)
        if change:
            changes.append(change)
    
    save_json(HASHES_FILE, hashes)
    
    log("=== Monitor check complete ===")
    
    # Output changes as JSON for the caller
    if changes:
        print(json.dumps({"changes": changes}))
    else:
        print(json.dumps({"changes": []}))
    
    return len(changes)

if __name__ == "__main__":
    exit(main())