"""Prometheus metrics collection for BanGUI backend.

This module provides metrics collection for:
- HTTP request count and latency per endpoint
- Active concurrent requests
- Custom application metrics (bans, jails, etc.)
"""

from __future__ import annotations

from prometheus_client import (
    CONTENT_TYPE_LATEST,
    CollectorRegistry,
    Counter,
    Gauge,
    Histogram,
    Summary,
    generate_latest,
)

__all__ = [
    "get_metrics_registry",
    "get_metrics",
    "http_request_count",
    "http_request_latency",
    "http_active_requests",
    "bans_total",
    "jails_total",
    "fail2ban_connection_errors",
    "external_logging_init_failures",
]

# Global registry
_registry: CollectorRegistry | None = None


def get_metrics_registry() -> CollectorRegistry:
    """Get or create the global metrics registry.
    
    Returns:
        The Prometheus CollectorRegistry instance.
    """
    global _registry
    if _registry is None:
        _registry = CollectorRegistry()
    return _registry


# HTTP Metrics

http_request_count = Counter(
    "bangui_http_requests_total",
    "Total HTTP requests by method, endpoint, and status code",
    ["method", "endpoint", "status_code"],
    registry=get_metrics_registry(),
)

http_request_latency = Histogram(
    "bangui_http_request_duration_seconds",
    "HTTP request latency in seconds by method and endpoint",
    ["method", "endpoint"],
    buckets=(0.005, 0.01, 0.025, 0.05, 0.075, 0.1, 0.25, 0.5, 0.75, 1.0, 2.5, 5.0, 7.5, 10.0),
    registry=get_metrics_registry(),
)

http_active_requests = Gauge(
    "bangui_http_active_requests",
    "Current number of active HTTP requests by method and endpoint",
    ["method", "endpoint"],
    registry=get_metrics_registry(),
)

# Application Metrics

bans_total = Gauge(
    "bangui_bans_total",
    "Total number of banned IPs across all jails",
    registry=get_metrics_registry(),
)

jails_total = Gauge(
    "bangui_jails_total",
    "Total number of fail2ban jails",
    registry=get_metrics_registry(),
)

fail2ban_connection_errors = Counter(
    "bangui_fail2ban_connection_errors_total",
    "Total number of fail2ban connection errors",
    registry=get_metrics_registry(),
)

external_logging_init_failures = Counter(
    "bangui_external_logging_init_failures_total",
    "Total number of external logging handler initialization failures",
    registry=get_metrics_registry(),
)

# Application startup and health

app_uptime = Summary(
    "bangui_uptime_seconds",
    "Application uptime in seconds",
    registry=get_metrics_registry(),
)


def get_metrics() -> bytes:
    """Get all collected metrics in Prometheus text format.
    
    Returns:
        Prometheus-formatted metrics as bytes.
    """
    return generate_latest(get_metrics_registry())


def get_metrics_content_type() -> str:
    """Get the correct Content-Type for Prometheus metrics.
    
    Returns:
        The MIME type for Prometheus metrics.
    """
    return CONTENT_TYPE_LATEST