//! SSL/TLS certificate validation and checking
//!
//! This module provides utilities for performing SSL/TLS-related health checks,
//! including:
//!
//! - Validating the presence and readability of certificate files
//! - (Future) Performing live TLS handshakes against remote endpoints
//!
//! At present, certificate validation is intentionally minimal. The current
//! implementation focuses on filesystem-level checks and API shape stability,
//! while full X.509 parsing and validation will be introduced later.
//!
//! ## Design notes
//!
//! - All checks return [`SslCheckResult`], aligning with the rest of the network
//!   health-check subsystem.
//! - Functions are asynchronous for API consistency, even if the current
//!   implementation does not require async execution.
//! - Feature-gated behavior is used for network-dependent checks.

use super::types::{CheckSeverity, HealthStatus, SslCheckResult};
use crate::{Error, Result};
use std::path::Path;

/// Check an SSL/TLS certificate from a local certificate file.
///
/// This function verifies that the provided certificate file:
///
/// - Exists on disk
/// - Is readable by the current process
///
/// No cryptographic validation is performed yet. In particular:
///
/// - The certificate is **not parsed**
/// - Expiry dates, issuer, and subject are **not inspected**
///
/// These capabilities will be added once full X.509 parsing support
/// is integrated.
///
/// ## Parameters
///
/// - `cert_path`: Path to a PEM-encoded certificate file
///
/// ## Returns
///
/// A [`SslCheckResult`] describing the outcome of the check.
///
/// - [`HealthStatus::Healthy`] if the file exists and is readable
/// - [`HealthStatus::Error`] if the file does not exist
///
/// ## Errors
///
/// This function returns an error if:
///
/// - The certificate file exists but cannot be read due to an I/O error
///
/// Missing files are **not treated as hard errors**; instead, they produce
/// a successful result with [`HealthStatus::Error`] so callers can aggregate
/// health-check outcomes without early termination.
///
/// ## Examples
///
/// ```no_run
/// use std::path::Path;
/// use nginx_discovery::network::check_ssl_certificate;
///
/// # async fn example() -> nginx_discovery::Result<()> {
/// let result = check_ssl_certificate(Path::new("/etc/ssl/certs/example.pem")).await?;
/// println!("{}", result.message);
/// # Ok(())
/// # }
/// ```
pub async fn check_ssl_certificate(cert_path: &Path) -> Result<SslCheckResult> {
    // Check if file exists
    if !cert_path.exists() {
        return Ok(SslCheckResult {
            status: HealthStatus::Error,
            message: format!("Certificate file not found: {}", cert_path.display()),
            severity: CheckSeverity::Critical,
            details: None,
            expires_at: None,
            days_until_expiry: None,
            issuer: None,
            subject: None,
        });
    }

    // Attempt to read the certificate file
    let _cert_data = std::fs::read(cert_path).map_err(Error::Io)?;

    // NOTE:
    // This is intentionally minimal. Full certificate parsing and validation
    // will be added once x509-parser or equivalent is integrated.

    Ok(SslCheckResult {
        status: HealthStatus::Healthy,
        message: format!("Certificate file exists: {}", cert_path.display()),
        severity: CheckSeverity::Info,
        details: Some("Full certificate validation not yet implemented".to_string()),
        expires_at: None,
        days_until_expiry: None,
        issuer: None,
        subject: None,
    })
}

/// Check the SSL/TLS configuration of a remote URL via a TLS handshake.
///
/// This function is **feature-gated** behind the `network` feature.
///
/// - When the `network` feature is enabled, this function currently returns
///   a placeholder result indicating that the check is not yet implemented.
/// - When the `network` feature is disabled, calling this function results
///   in an error.
///
/// The function is asynchronous to preserve API stability once live TLS
/// checks are introduced.
///
/// ## Parameters
///
/// - `_url`: A URL (e.g. `https://example.com`) to validate
///
/// ## Returns
///
/// A [`SslCheckResult`] describing the outcome of the check.
///
/// ## Errors
///
/// This function returns an error if:
///
/// - The `network` feature is not enabled at compile time
///
/// ## Examples
///
/// ```no_run
/// use nginx_discovery::network::check_ssl_url;
///
/// # async fn example() -> nginx_discovery::Result<()> {
/// let result = check_ssl_url("https://example.com").await?;
/// println!("{}", result.message);
/// # Ok(())
/// # }
/// ```
#[allow(clippy::unused_async)]
pub async fn check_ssl_url(_url: &str) -> Result<SslCheckResult> {
    #[cfg(feature = "network")]
    {
        // Placeholder implementation
        Ok(SslCheckResult {
            status: HealthStatus::Healthy,
            message: "URL SSL check not yet implemented".to_string(),
            severity: CheckSeverity::Info,
            details: None,
            expires_at: None,
            days_until_expiry: None,
            issuer: None,
            subject: None,
        })
    }

    #[cfg(not(feature = "network"))]
    {
        Err(Error::FeatureNotEnabled("network".to_string()))
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[tokio::test]
    async fn test_check_nonexistent_cert() {
        let result = check_ssl_certificate(Path::new("/nonexistent/cert.pem")).await;
        assert!(result.is_ok());

        let check = result.unwrap();
        assert_eq!(check.status, HealthStatus::Error);
    }
}
