"""
Flask routes for notification service configuration and management.
Blueprint pattern matching flask_health_routes.py / flask_security_routes.py.
"""

import hmac
import time
import hashlib
from collections import deque
from flask import Blueprint, jsonify, request
from notification_manager import notification_manager


# ─── Webhook Hardening Helpers ───────────────────────────────────

class WebhookRateLimiter:
    """Simple sliding-window rate limiter for the webhook endpoint."""
    
    def __init__(self, max_requests: int = 60, window_seconds: int = 60):
        self._max = max_requests
        self._window = window_seconds
        self._timestamps: deque = deque()
    
    def allow(self) -> bool:
        now = time.time()
        # Prune entries outside the window
        while self._timestamps and now - self._timestamps[0] > self._window:
            self._timestamps.popleft()
        if len(self._timestamps) >= self._max:
            return False
        self._timestamps.append(now)
        return True


class ReplayCache:
    """Bounded in-memory cache of recently seen request signatures (60s TTL)."""
    
    _MAX_SIZE = 2000  # Hard cap to prevent memory growth
    
    def __init__(self, ttl: int = 60):
        self._ttl = ttl
        self._seen: dict = {}  # signature -> timestamp
    
    def check_and_record(self, signature: str) -> bool:
        """Return True if this signature was already seen (replay). Records it otherwise."""
        now = time.time()
        # Periodic cleanup
        if len(self._seen) > self._MAX_SIZE // 2:
            cutoff = now - self._ttl
            self._seen = {k: v for k, v in self._seen.items() if v > cutoff}
        if signature in self._seen and now - self._seen[signature] < self._ttl:
            return True  # Replay detected
        self._seen[signature] = now
        return False


# Module-level singletons (one per process)
_webhook_limiter = WebhookRateLimiter(max_requests=60, window_seconds=60)
_replay_cache = ReplayCache(ttl=60)

# Timestamp validation window (seconds)
_TIMESTAMP_MAX_DRIFT = 60

notification_bp = Blueprint('notifications', __name__)


@notification_bp.route('/api/notifications/settings', methods=['GET'])
def get_notification_settings():
    """Get all notification settings for the UI."""
    try:
        settings = notification_manager.get_settings()
        return jsonify(settings)
    except Exception as e:
        return jsonify({'error': str(e)}), 500


@notification_bp.route('/api/notifications/settings', methods=['POST'])
def save_notification_settings():
    """Save notification settings from the UI."""
    try:
        payload = request.get_json()
        if not payload:
            return jsonify({'error': 'No data provided'}), 400
        
        result = notification_manager.save_settings(payload)
        return jsonify(result)
    except Exception as e:
        return jsonify({'error': str(e)}), 500


@notification_bp.route('/api/notifications/test', methods=['POST'])
def test_notification():
    """Send a test notification to one or all channels."""
    try:
        data = request.get_json() or {}
        channel = data.get('channel', 'all')
        
        result = notification_manager.test_channel(channel)
        return jsonify(result)
    except Exception as e:
        return jsonify({'error': str(e)}), 500


@notification_bp.route('/api/notifications/status', methods=['GET'])
def get_notification_status():
    """Get notification service status."""
    try:
        status = notification_manager.get_status()
        return jsonify(status)
    except Exception as e:
        return jsonify({'error': str(e)}), 500


@notification_bp.route('/api/notifications/history', methods=['GET'])
def get_notification_history():
    """Get notification history with optional filters."""
    try:
        limit = request.args.get('limit', 50, type=int)
        offset = request.args.get('offset', 0, type=int)
        severity = request.args.get('severity', '')
        channel = request.args.get('channel', '')
        
        result = notification_manager.get_history(limit, offset, severity, channel)
        return jsonify(result)
    except Exception as e:
        return jsonify({'error': str(e)}), 500


@notification_bp.route('/api/notifications/history', methods=['DELETE'])
def clear_notification_history():
    """Clear all notification history."""
    try:
        result = notification_manager.clear_history()
        return jsonify(result)
    except Exception as e:
        return jsonify({'error': str(e)}), 500


@notification_bp.route('/api/notifications/send', methods=['POST'])
def send_notification():
    """Send a notification via API (for testing or external triggers)."""
    try:
        data = request.get_json()
        if not data:
            return jsonify({'error': 'No data provided'}), 400
        
        result = notification_manager.send_notification(
            event_type=data.get('event_type', 'custom'),
            severity=data.get('severity', 'INFO'),
            title=data.get('title', ''),
            message=data.get('message', ''),
            data=data.get('data', {}),
            source='api'
        )
        return jsonify(result)
    except Exception as e:
        return jsonify({'error': str(e)}), 500


@notification_bp.route('/api/notifications/proxmox/setup-webhook', methods=['POST'])
def setup_proxmox_webhook():
    """Automatically configure PVE notifications to call our webhook.
    
    Strategy: parse existing config into discrete blocks, only add or
    replace blocks whose name matches our IDs, preserve everything else
    byte-for-byte.  Creates timestamped backups before any modification.
    
    Idempotent: safe to call multiple times.
    Only touches blocks named 'proxmenux-webhook' / 'proxmenux-default'.
    """
    import os
    import shutil
    import secrets as secrets_mod
    from datetime import datetime
    
    ENDPOINT_ID = 'proxmenux-webhook'
    MATCHER_ID = 'proxmenux-default'
    WEBHOOK_URL = 'http://127.0.0.1:8008/api/notifications/webhook'
    NOTIFICATIONS_CFG = '/etc/pve/notifications.cfg'
    PRIV_CFG = '/etc/pve/priv/notifications.cfg'
    
    result = {
        'configured': False,
        'endpoint_id': ENDPOINT_ID,
        'matcher_id': MATCHER_ID,
        'url': WEBHOOK_URL,
        'fallback_commands': [],
        'error': None,
    }
    
    def _build_fallback(secret_val):
        """Build manual instructions as fallback."""
        return [
            "# Add these blocks to /etc/pve/notifications.cfg",
            "# (append at the end, do NOT delete existing content):",
            "",
            f"webhook: {ENDPOINT_ID}",
            f"\turl {WEBHOOK_URL}",
            "\tmethod post",
            "\theader Content-Type:application/json",
            f"\theader X-Webhook-Secret:{{{{ secrets.proxmenux_secret }}}}",
            "",
            f"matcher: {MATCHER_ID}",
            f"\ttarget {ENDPOINT_ID}",
            "\tmatch-severity warning,error",
            "",
            "# Add this block to /etc/pve/priv/notifications.cfg",
            "# (append at the end, do NOT delete existing content):",
            "",
            f"webhook: {ENDPOINT_ID}",
            f"\tsecret proxmenux_secret {secret_val}",
        ]
    
    def _read_file(path):
        """Read file, return (content, error). Content is '' if missing."""
        try:
            with open(path, 'r') as f:
                return f.read(), None
        except FileNotFoundError:
            return '', None
        except PermissionError:
            return None, f'Permission denied reading {path}'
        except Exception as e:
            return None, str(e)
    
    def _backup_file(path):
        """Create timestamped backup if file exists. Never fails fatally."""
        try:
            if os.path.exists(path):
                ts = datetime.now().strftime('%Y%m%d_%H%M%S')
                backup = f"{path}.proxmenux_backup_{ts}"
                shutil.copy2(path, backup)
        except Exception:
            pass  # Best-effort backup
    
    def _parse_blocks(text):
        """Parse PVE config into list of (block_type, block_name, block_text).
        
        A block starts with a non-whitespace line like 'type: name'
        and includes all subsequent lines that start with whitespace.
        Lines between blocks (blank lines, comments) are preserved as
        anonymous blocks with type=None, name=None.
        """
        blocks = []
        current_header = None
        current_lines = []
        gap_lines = []  # blank/comment lines between blocks
        
        for line in text.splitlines(keepends=True):
            stripped = line.strip()
            
            # Check if this is a block header (non-whitespace, contains ':')
            if stripped and not line[0].isspace() and ':' in stripped:
                # Save previous block
                if current_header is not None:
                    blocks.append(current_header + (''.join(current_lines),))
                    current_lines = []
                elif current_lines:
                    blocks.append((None, None, ''.join(current_lines)))
                    current_lines = []
                
                # Save any gap lines as anonymous block
                if gap_lines:
                    blocks.append((None, None, ''.join(gap_lines)))
                    gap_lines = []
                
                # Parse header
                parts = stripped.split(':', 1)
                btype = parts[0].strip()
                bname = parts[1].strip() if len(parts) > 1 else ''
                current_header = (btype, bname)
                current_lines = [line]
            
            elif current_header is not None and line[0:1].isspace():
                # Continuation line (starts with whitespace)
                current_lines.append(line)
            
            else:
                # Gap line (blank, comment, or anything between blocks)
                if current_header is not None:
                    blocks.append(current_header + (''.join(current_lines),))
                    current_header = None
                    current_lines = []
                gap_lines.append(line)
        
        # Flush remaining
        if current_header is not None:
            blocks.append(current_header + (''.join(current_lines),))
        elif current_lines:
            blocks.append((None, None, ''.join(current_lines)))
        if gap_lines:
            blocks.append((None, None, ''.join(gap_lines)))
        
        return blocks
    
    def _upsert_block(blocks, block_type, block_name, new_text):
        """Replace block if exists, otherwise append. Returns new list."""
        found = False
        result_blocks = []
        for btype, bname, btext in blocks:
            if btype == block_type and bname == block_name:
                result_blocks.append((block_type, block_name, new_text))
                found = True
            else:
                result_blocks.append((btype, bname, btext))
        if not found:
            # Append with blank line separator
            result_blocks.append((None, None, '\n'))
            result_blocks.append((block_type, block_name, new_text))
        return result_blocks
    
    def _blocks_to_text(blocks):
        """Reassemble blocks into config text."""
        return ''.join(btext for _, _, btext in blocks)
    
    def _write_safe(path, content, original_content):
        """Write content to path. On failure, try to restore original."""
        try:
            with open(path, 'w') as f:
                f.write(content)
            return None
        except PermissionError:
            return f'Permission denied writing {path}'
        except Exception as e:
            # Try to restore original
            try:
                if original_content is not None:
                    with open(path, 'w') as f:
                        f.write(original_content)
            except Exception:
                pass
            return str(e)
    
    try:
        # ── Step 1: Ensure webhook secret exists ──
        secret = notification_manager.get_webhook_secret()
        if not secret:
            secret = secrets_mod.token_urlsafe(32)
            notification_manager._save_setting('webhook_secret', secret)
        
        # ── Step 2: Read both config files ──
        cfg_text, err = _read_file(NOTIFICATIONS_CFG)
        if err:
            result['error'] = err
            result['fallback_commands'] = _build_fallback(secret)
            return jsonify(result), 200
        
        priv_text, err = _read_file(PRIV_CFG)
        if err:
            result['error'] = err
            result['fallback_commands'] = _build_fallback(secret)
            return jsonify(result), 200
        
        # ── Step 3: Create backups ──
        _backup_file(NOTIFICATIONS_CFG)
        _backup_file(PRIV_CFG)
        
        # ── Step 4: Parse existing blocks ──
        cfg_blocks = _parse_blocks(cfg_text)
        priv_blocks = _parse_blocks(priv_text)
        
        # ── Step 5: Build our new blocks ──
        endpoint_text = (
            f"webhook: {ENDPOINT_ID}\n"
            f"\turl {WEBHOOK_URL}\n"
            f"\tmethod post\n"
            f"\theader Content-Type:application/json\n"
            f"\theader X-Webhook-Secret:{{{{ secrets.proxmenux_secret }}}}\n"
        )
        
        matcher_text = (
            f"matcher: {MATCHER_ID}\n"
            f"\ttarget {ENDPOINT_ID}\n"
            f"\tmatch-severity warning,error\n"
        )
        
        priv_secret_text = (
            f"webhook: {ENDPOINT_ID}\n"
            f"\tsecret proxmenux_secret {secret}\n"
        )
        
        # ── Step 6: Upsert (replace or append) our blocks only ──
        cfg_blocks = _upsert_block(cfg_blocks, 'webhook', ENDPOINT_ID, endpoint_text)
        cfg_blocks = _upsert_block(cfg_blocks, 'matcher', MATCHER_ID, matcher_text)
        priv_blocks = _upsert_block(priv_blocks, 'webhook', ENDPOINT_ID, priv_secret_text)
        
        new_cfg = _blocks_to_text(cfg_blocks)
        new_priv = _blocks_to_text(priv_blocks)
        
        # ── Step 7: Write back (with rollback on error) ──
        err = _write_safe(NOTIFICATIONS_CFG, new_cfg, cfg_text)
        if err:
            result['error'] = err
            result['fallback_commands'] = _build_fallback(secret)
            return jsonify(result), 200
        
        err = _write_safe(PRIV_CFG, new_priv, priv_text)
        if err:
            # Rollback main config
            _write_safe(NOTIFICATIONS_CFG, cfg_text, None)
            result['error'] = f'Secret file failed: {err}. Main config rolled back.'
            result['fallback_commands'] = [
                f"# Add to {PRIV_CFG} (append, don't overwrite):",
                f"webhook: {ENDPOINT_ID}",
                f"\tsecret proxmenux_secret {secret}",
            ]
            return jsonify(result), 200
        
        result['configured'] = True
        result['secret'] = secret
        return jsonify(result), 200
    
    except Exception as e:
        result['error'] = str(e)
        try:
            result['fallback_commands'] = _build_fallback(
                notification_manager.get_webhook_secret() or 'YOUR_SECRET'
            )
        except Exception:
            result['fallback_commands'] = _build_fallback('YOUR_SECRET')
        return jsonify(result), 200


@notification_bp.route('/api/notifications/webhook', methods=['POST'])
def proxmox_webhook():
    """Receive native Proxmox VE notification webhooks (hardened).
    
    Security layers:
      1. Rate limiting (60 req/min) -- always
      2. Shared secret (X-Webhook-Secret) -- always required
      3. Anti-replay timestamp (60s window) -- remote only
      4. Replay cache (signature dedup) -- remote only
      5. IP allowlist (optional) -- remote only
    
    Localhost callers (127.0.0.1 / ::1) bypass layers 3-5 because Proxmox
    cannot inject dynamic timestamp headers. The shared secret is still
    required for localhost to prevent any local process from injecting events.
    """
    _reject = lambda code, error, status: (jsonify({'accepted': False, 'error': error}), status)
    
    client_ip = request.remote_addr or ''
    is_localhost = client_ip in ('127.0.0.1', '::1')
    
    # ── Layer 1: Rate limiting (always) ──
    if not _webhook_limiter.allow():
        resp = jsonify({'accepted': False, 'error': 'rate_limited'})
        resp.headers['Retry-After'] = '60'
        return resp, 429
    
    # ── Layer 2: Shared secret (always required) ──
    try:
        configured_secret = notification_manager.get_webhook_secret()
    except Exception:
        configured_secret = ''
    
    if not configured_secret:
        return _reject(500, 'webhook_not_configured', 500)
    
    request_secret = request.headers.get('X-Webhook-Secret', '')
    if not request_secret:
        return _reject(401, 'missing_secret', 401)
    if not hmac.compare_digest(configured_secret, request_secret):
        return _reject(401, 'invalid_secret', 401)
    
    # ── Layers 3-5: Remote-only checks ──
    if not is_localhost:
        # Layer 3: Anti-replay timestamp
        ts_header = request.headers.get('X-ProxMenux-Timestamp', '')
        if not ts_header:
            return _reject(401, 'missing_timestamp', 401)
        try:
            ts_value = int(ts_header)
        except (ValueError, TypeError):
            return _reject(401, 'invalid_timestamp', 401)
        if abs(time.time() - ts_value) > _TIMESTAMP_MAX_DRIFT:
            return _reject(401, 'timestamp_expired', 401)
        
        # Layer 4: Replay cache
        raw_body = request.get_data(as_text=True) or ''
        signature = hashlib.sha256(f"{ts_value}:{raw_body}".encode(errors='replace')).hexdigest()
        if _replay_cache.check_and_record(signature):
            return _reject(409, 'replay_detected', 409)
        
        # Layer 5: IP allowlist
        try:
            allowed_ips = notification_manager.get_webhook_allowed_ips()
            if allowed_ips and client_ip not in allowed_ips:
                return _reject(403, 'forbidden_ip', 403)
        except Exception:
            pass
    
    # ── Parse and process payload ──
    try:
        payload = request.get_json(silent=True) or {}
        if not payload:
            payload = dict(request.form)
        if not payload:
            return _reject(400, 'invalid_payload', 400)
        
        result = notification_manager.process_webhook(payload)
        status_code = 200 if result.get('accepted') else 400
        return jsonify(result), status_code
    except Exception:
        return jsonify({'accepted': False, 'error': 'internal_error'}), 500