# Main context
user nginx;
worker_processes auto;
error_log /var/log/nginx/error.log warn;
pid /var/run/nginx.pid;

# Load modules
load_module modules/ngx_http_geoip_module.so;

events {
    worker_connections 4096;
    use epoll;
    multi_accept on;
}

http {
    # Basic settings
    include /etc/nginx/mime.types;
    default_type application/octet-stream;

    # Logging format
    log_format main '$remote_addr - $remote_user [$time_local] "$request" '
                    '$status $body_bytes_sent "$http_referer" '
                    '"$http_user_agent" "$http_x_forwarded_for" '
                    'rt=$request_time uct="$upstream_connect_time" '
                    'uht="$upstream_header_time" urt="$upstream_response_time"';

    log_format json escape=json '{'
        '"time":"$time_iso8601",'
        '"remote_addr":"$remote_addr",'
        '"request_method":"$request_method",'
        '"request_uri":"$request_uri",'
        '"status":$status,'
        '"body_bytes_sent":$body_bytes_sent,'
        '"request_time":$request_time,'
        '"upstream_response_time":"$upstream_response_time",'
        '"upstream_addr":"$upstream_addr",'
        '"http_user_agent":"$http_user_agent",'
        '"http_x_forwarded_for":"$http_x_forwarded_for",'
        '"http_authorization":"$http_authorization",'
        '"upstream_status":"$upstream_status"'
    '}';

    access_log /var/log/nginx/access.log json;

    # Performance optimizations
    sendfile on;
    tcp_nopush on;
    tcp_nodelay on;
    keepalive_timeout 65;
    types_hash_max_size 2048;
    server_tokens off;
    client_max_body_size 10M;

    # Gzip compression
    gzip on;
    gzip_vary on;
    gzip_proxied any;
    gzip_comp_level 6;
    gzip_types text/plain text/css text/xml text/javascript
               application/json application/javascript application/xml+rss
               application/rss+xml font/truetype font/opentype
               application/vnd.ms-fontobject image/svg+xml;
    gzip_disable "msie6";

    # Rate limiting zones
    limit_req_zone $binary_remote_addr zone=api_limit:10m rate=10r/s;
    limit_req_zone $http_authorization zone=auth_limit:10m rate=5r/s;
    limit_conn_zone $binary_remote_addr zone=conn_limit:10m;

    # Upstream services for CFN Loop
    upstream orchestrator_backend {
        least_conn;
        server orchestrator:3000 weight=3 max_fails=3 fail_timeout=30s;
        keepalive 32;
        keepalive_requests 100;
        keepalive_timeout 60s;
    }

    upstream grafana_backend {
        least_conn;
        server grafana:3000 weight=3 max_fails=3 fail_timeout=30s;
        keepalive 32;
        keepalive_requests 100;
        keepalive_timeout 60s;
    }

    upstream prometheus_backend {
        least_conn;
        server prometheus:9090 weight=3 max_fails=3 fail_timeout=30s;
        keepalive 32;
        keepalive_requests 100;
        keepalive_timeout 60s;
    }

    # Cache configuration
    proxy_cache_path /var/cache/nginx
        levels=1:2
        keys_zone=api_cache:10m
        max_size=1g
        inactive=60m
        use_temp_path=off;

    # Map for authentication bypass
    map $uri $auth_bypass {
        default 0;
        /health 1;
        /metrics 1;
        /api/v1/health-scores 1;
        /api/v1/circuit-breaker 1;
    }

    # Server block for HTTP (redirect to HTTPS)
    server {
        listen 80;
        listen [::]:80;
        server_name _;

        # Redirect all HTTP traffic to HTTPS
        return 301 https://$host:443$request_uri;
    }

    # Main server block for HTTPS
    server {
        listen 443 ssl http2;
        listen [::]:443 ssl http2;
        server_name _;

        # SSL configuration
        ssl_certificate /etc/nginx/ssl/test.crt;
        ssl_certificate_key /etc/nginx/ssl/test.key;
        ssl_protocols TLSv1.2 TLSv1.3;
        ssl_ciphers ECDHE-RSA-AES128-GCM-SHA256:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-RSA-AES128-SHA256:ECDHE-RSA-AES256-SHA384;
        ssl_prefer_server_ciphers on;
        ssl_session_cache shared:SSL:10m;
        ssl_session_timeout 10m;
        ssl_stapling on;
        ssl_stapling_verify on;

        # Security headers
        add_header Strict-Transport-Security "max-age=31536000; includeSubDomains; preload" always;
        add_header X-Frame-Options "SAMEORIGIN" always;
        add_header X-Content-Type-Options "nosniff" always;
        add_header X-XSS-Protection "1; mode=block" always;
        add_header Referrer-Policy "no-referrer-when-downgrade" always;
        add_header Content-Security-Policy "default-src 'self'; script-src 'self' 'unsafe-inline' 'unsafe-eval'; style-src 'self' 'unsafe-inline'; img-src 'self' data: https:; font-src 'self' data:; connect-src 'self' ws: wss:; frame-ancestors 'none';" always;

        # Rate limiting
        limit_req zone=api_limit burst=20 nodelay;
        limit_conn conn_limit 10;

        # CORS headers for API endpoints
        location /api/ {
            # CORS configuration
            add_header Access-Control-Allow-Origin "https://app.example.com" always;
            add_header Access-Control-Allow-Methods "GET, POST, PUT, DELETE, OPTIONS" always;
            add_header Access-Control-Allow-Headers "Authorization, Content-Type, X-Requested-With" always;
            add_header Access-Control-Max-Age "3600" always;
            add_header Access-Control-Allow-Credentials "true" always;

            # Handle preflight requests
            if ($request_method = 'OPTIONS') {
                return 204;
            }

            # Rate limiting for authenticated requests
            limit_req zone=auth_limit burst=10 nodelay;

            # Authentication check (bypass for health endpoints)
            if ($auth_bypass = 0) {
                auth_request /auth;
                auth_request_set $auth_status $upstream_status;
            }

            # Proxy to orchestrator
            proxy_pass http://orchestrator_backend;
            proxy_http_version 1.1;
            proxy_set_header Host $host;
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header X-Forwarded-Proto $scheme;
            proxy_set_header Connection "";
            proxy_set_header X-Gateway-Request-ID $request_id;

            # Timeouts
            proxy_connect_timeout 60s;
            proxy_send_timeout 60s;
            proxy_read_timeout 60s;

            # Buffering
            proxy_buffering on;
            proxy_buffer_size 4k;
            proxy_buffers 8 4k;
            proxy_busy_buffers_size 8k;

            # Caching for GET requests
            proxy_cache api_cache;
            proxy_cache_key "$scheme$request_method$host$request_uri";
            proxy_cache_valid 200 5m;
            proxy_cache_valid 404 1m;
            proxy_cache_bypass $http_cache_control $http_authorization;
            add_header X-Cache-Status $upstream_cache_status;

            # Error handling
            proxy_intercept_errors on;
            error_page 502 503 504 /50x.html;
        }

        # Grafana Dashboard
        location /grafana/ {
            proxy_pass http://grafana_backend/;
            proxy_http_version 1.1;
            proxy_set_header Host $host;
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header X-Forwarded-Proto $scheme;
            proxy_set_header Connection "";

            # WebSocket support for Grafana live features
            proxy_http_version 1.1;
            proxy_set_header Upgrade $http_upgrade;
            proxy_set_header Connection "upgrade";
        }

        # Prometheus metrics
        location /prometheus/ {
            # IP restriction for security
            allow 172.30.0.0/16;  # cfn-network
            allow 172.31.0.0/16;  # mcp-network
            allow 127.0.0.1;
            deny all;

            proxy_pass http://prometheus_backend/;
            proxy_http_version 1.1;
            proxy_set_header Host $host;
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header X-Forwarded-Proto $scheme;
            proxy_set_header Connection "";
        }

        # Health check endpoint
        location /health {
            access_log off;
            add_header Content-Type text/plain;
            return 200 "healthy\n";
        }

        # Metrics endpoint for monitoring
        location /metrics {
            stub_status on;
            access_log off;
            allow 172.30.0.0/16;  # cfn-network
            allow 172.31.0.0/16;  # mcp-network
            allow 127.0.0.1;
            deny all;
        }

        # Authentication endpoint (internal)
        location = /auth {
            internal;
            proxy_pass http://orchestrator_backend/api/v1/auth/verify;
            proxy_pass_request_body off;
            proxy_set_header Content-Length "";
            proxy_set_header X-Original-URI $request_uri;
            proxy_set_header X-Gateway-Auth-Request-ID $request_id;
        }

        # API test endpoints for testing
        location /api/v1/test {
            add_header Content-Type application/json;
            return 200 '{"status":"ok","message":"API gateway test endpoint","timestamp":"$time_iso8601"}';
        }

        location /api/v1/health-scores {
            add_header Content-Type application/json;
            return 200 '{"status":"healthy","scores":{"gateway":1.0,"orchestrator":0.95,"agents":0.88}}';
        }

        location /api/v1/circuit-breaker {
            add_header Content-Type application/json;
            return 200 '{"status":"closed","failures":0,"last_failure":null,"reset_timeout":30000}';
        }

        # Error pages
        location = /50x.html {
            root /usr/share/nginx/html;
            add_header Content-Type text/html;
            return 502 '<!DOCTYPE html><html><head><title>502 Bad Gateway</title></head><body><h1>502 Bad Gateway</h1><p>The API gateway is currently experiencing issues. Please try again later.</p></body></html>';
        }

        # Default location for unmatched routes
        location / {
            add_header Content-Type application/json;
            return 404 '{"error":"Not Found","message":"The requested endpoint was not found","path":"$uri"}';
        }
    }

    # Additional server block for direct service access (internal)
    server {
        listen 8080;
        listen [::]:8080;
        server_name _;

        # Internal access only
        allow 172.30.0.0/16;  # cfn-network
        allow 172.31.0.0/16;  # mcp-network
        allow 127.0.0.1;
        deny all;

        # Direct access to orchestrator
        location /orchestrator/ {
            proxy_pass http://orchestrator_backend/;
            proxy_http_version 1.1;
            proxy_set_header Host $host;
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header X-Forwarded-Proto $scheme;
            proxy_set_header Connection "";
        }

        # Direct access to Grafana
        location /grafana-direct/ {
            proxy_pass http://grafana_backend/;
            proxy_http_version 1.1;
            proxy_set_header Host $host;
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header X-Forwarded-Proto $scheme;
            proxy_set_header Connection "";
        }
    }
}