armature-core 0.7.0

//! Health check module for application monitoring and Kubernetes probes.
//!
//! This module provides health check endpoints compatible with Kubernetes
//! liveness, readiness, and startup probes, as well as general health monitoring.
//!
//! ## Quick Start
//!
//! ```rust
//! use armature_core::health::{HealthService, HealthIndicator, HealthCheckResult, HealthStatus};
//! use async_trait::async_trait;
//!
//! // Create a custom health indicator
//! struct DatabaseHealthIndicator;
//!
//! #[async_trait]
//! impl HealthIndicator for DatabaseHealthIndicator {
//!     fn name(&self) -> &str {
//!         "database"
//!     }
//!
//!     async fn check(&self) -> HealthCheckResult {
//!         // Check database connectivity
//!         HealthCheckResult::up("database")
//!             .with_detail("type", "postgresql")
//!             .with_detail("pool_size", "10")
//!     }
//! }
//! ```
//!
//! ## Kubernetes Probes
//!
//! The health module provides three endpoints for Kubernetes:
//!
//! - `/health/live` - Liveness probe: Is the application running?
//! - `/health/ready` - Readiness probe: Is the application ready to serve traffic?
//! - `/health` - Full health check with all indicators
//!
//! ## Built-in Indicators
//!
//! - `MemoryHealthIndicator` - Checks memory usage
//! - `DiskHealthIndicator` - Checks disk space
//! - `UptimeHealthIndicator` - Reports application uptime

use async_trait::async_trait;
use futures_util::future::join_all;
use serde::{Deserialize, Serialize};
use std::collections::HashMap;
use std::sync::Arc;
use std::time::{Duration, Instant, SystemTime, UNIX_EPOCH};
use tokio::sync::RwLock;

/// Health status of a component or the overall application.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Default, Serialize, Deserialize)]
#[serde(rename_all = "UPPERCASE")]
pub enum HealthStatus {
    /// Component is functioning normally
    Up,
    /// Component is not functioning
    Down,
    /// Component is functioning but with issues
    Degraded,
    /// Component status is unknown
    #[default]
    Unknown,
}

impl HealthStatus {
    /// Returns true if the status indicates the component is healthy
    pub fn is_healthy(&self) -> bool {
        matches!(self, HealthStatus::Up | HealthStatus::Degraded)
    }

    /// Returns the HTTP status code for this health status
    pub fn http_status_code(&self) -> u16 {
        match self {
            HealthStatus::Up => 200,
            HealthStatus::Degraded => 200,
            HealthStatus::Down => 503,
            HealthStatus::Unknown => 503,
        }
    }
}

impl std::fmt::Display for HealthStatus {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            HealthStatus::Up => write!(f, "UP"),
            HealthStatus::Down => write!(f, "DOWN"),
            HealthStatus::Degraded => write!(f, "DEGRADED"),
            HealthStatus::Unknown => write!(f, "UNKNOWN"),
        }
    }
}

/// Result of a health check for a single component.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct HealthCheckResult {
    /// Name of the component being checked
    pub name: String,
    /// Current health status
    pub status: HealthStatus,
    /// Additional details about the component
    #[serde(skip_serializing_if = "HashMap::is_empty")]
    pub details: HashMap<String, String>,
    /// Time taken to perform the health check (in milliseconds)
    #[serde(skip_serializing_if = "Option::is_none")]
    pub duration_ms: Option<u64>,
    /// Error message if the check failed
    #[serde(skip_serializing_if = "Option::is_none")]
    pub error: Option<String>,
    /// Timestamp of the check
    #[serde(skip_serializing_if = "Option::is_none")]
    pub timestamp: Option<u64>,
}

impl HealthCheckResult {
    /// Creates a new health check result with UP status
    pub fn up(name: impl Into<String>) -> Self {
        Self {
            name: name.into(),
            status: HealthStatus::Up,
            details: HashMap::new(),
            duration_ms: None,
            error: None,
            timestamp: Some(current_timestamp()),
        }
    }

    /// Creates a new health check result with DOWN status
    pub fn down(name: impl Into<String>) -> Self {
        Self {
            name: name.into(),
            status: HealthStatus::Down,
            details: HashMap::new(),
            duration_ms: None,
            error: None,
            timestamp: Some(current_timestamp()),
        }
    }

    /// Creates a new health check result with DEGRADED status
    pub fn degraded(name: impl Into<String>) -> Self {
        Self {
            name: name.into(),
            status: HealthStatus::Degraded,
            details: HashMap::new(),
            duration_ms: None,
            error: None,
            timestamp: Some(current_timestamp()),
        }
    }

    /// Creates a new health check result with UNKNOWN status
    pub fn unknown(name: impl Into<String>) -> Self {
        Self {
            name: name.into(),
            status: HealthStatus::Unknown,
            details: HashMap::new(),
            duration_ms: None,
            error: None,
            timestamp: Some(current_timestamp()),
        }
    }

    /// Adds a detail to the health check result
    pub fn with_detail(mut self, key: impl Into<String>, value: impl Into<String>) -> Self {
        self.details.insert(key.into(), value.into());
        self
    }

    /// Sets the error message
    pub fn with_error(mut self, error: impl Into<String>) -> Self {
        self.error = Some(error.into());
        self.status = HealthStatus::Down;
        self
    }

    /// Sets the duration in milliseconds
    pub fn with_duration(mut self, duration: Duration) -> Self {
        self.duration_ms = Some(duration.as_millis() as u64);
        self
    }
}

/// Aggregated health response for the entire application.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct HealthResponse {
    /// Overall health status
    pub status: HealthStatus,
    /// Individual component health checks
    #[serde(skip_serializing_if = "HashMap::is_empty")]
    pub components: HashMap<String, HealthCheckResult>,
    /// Application information
    #[serde(skip_serializing_if = "Option::is_none")]
    pub info: Option<HealthInfo>,
    /// Timestamp of the health check
    pub timestamp: u64,
}

impl HealthResponse {
    /// Creates a new health response
    pub fn new(status: HealthStatus) -> Self {
        Self {
            status,
            components: HashMap::new(),
            info: None,
            timestamp: current_timestamp(),
        }
    }

    /// Adds a component health check result
    pub fn with_component(mut self, result: HealthCheckResult) -> Self {
        self.components.insert(result.name.clone(), result);
        self
    }

    /// Sets the application info
    pub fn with_info(mut self, info: HealthInfo) -> Self {
        self.info = Some(info);
        self
    }

    /// Calculates the overall status from component statuses
    pub fn calculate_status(&mut self) {
        if self.components.is_empty() {
            self.status = HealthStatus::Up;
            return;
        }

        let has_down = self
            .components
            .values()
            .any(|c| c.status == HealthStatus::Down);
        let has_degraded = self
            .components
            .values()
            .any(|c| c.status == HealthStatus::Degraded);
        let has_unknown = self
            .components
            .values()
            .any(|c| c.status == HealthStatus::Unknown);

        self.status = if has_down {
            HealthStatus::Down
        } else if has_degraded {
            HealthStatus::Degraded
        } else if has_unknown {
            HealthStatus::Unknown
        } else {
            HealthStatus::Up
        };
    }
}

/// Application information included in health responses.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct HealthInfo {
    /// Application name
    #[serde(skip_serializing_if = "Option::is_none")]
    pub name: Option<String>,
    /// Application version
    #[serde(skip_serializing_if = "Option::is_none")]
    pub version: Option<String>,
    /// Application description
    #[serde(skip_serializing_if = "Option::is_none")]
    pub description: Option<String>,
    /// Uptime in seconds
    #[serde(skip_serializing_if = "Option::is_none")]
    pub uptime_seconds: Option<u64>,
}

impl HealthInfo {
    /// Creates new health info with the given name
    pub fn new(name: impl Into<String>) -> Self {
        Self {
            name: Some(name.into()),
            version: None,
            description: None,
            uptime_seconds: None,
        }
    }

    /// Sets the version
    pub fn with_version(mut self, version: impl Into<String>) -> Self {
        self.version = Some(version.into());
        self
    }

    /// Sets the description
    pub fn with_description(mut self, description: impl Into<String>) -> Self {
        self.description = Some(description.into());
        self
    }

    /// Sets the uptime
    pub fn with_uptime(mut self, uptime: Duration) -> Self {
        self.uptime_seconds = Some(uptime.as_secs());
        self
    }
}

/// Trait for implementing custom health indicators.
///
/// Health indicators are used to check the health of individual components
/// such as databases, caches, external services, etc.
///
/// ## Example
///
/// ```rust
/// use armature_core::health::{HealthIndicator, HealthCheckResult};
/// use async_trait::async_trait;
///
/// struct RedisHealthIndicator {
///     // Redis connection would go here
/// }
///
/// #[async_trait]
/// impl HealthIndicator for RedisHealthIndicator {
///     fn name(&self) -> &str {
///         "redis"
///     }
///
///     async fn check(&self) -> HealthCheckResult {
///         // In a real implementation, you would ping Redis
///         HealthCheckResult::up("redis")
///             .with_detail("version", "7.0.0")
///     }
///
///     fn is_critical(&self) -> bool {
///         true // Application cannot function without Redis
///     }
/// }
/// ```
#[async_trait]
pub trait HealthIndicator: Send + Sync {
    /// Returns the name of this health indicator
    fn name(&self) -> &str;

    /// Performs the health check and returns the result
    async fn check(&self) -> HealthCheckResult;

    /// Returns whether this indicator is critical for application health.
    /// If a critical indicator fails, the overall status will be DOWN.
    fn is_critical(&self) -> bool {
        false
    }

    /// Returns whether this indicator should be included in readiness checks.
    fn include_in_readiness(&self) -> bool {
        true
    }

    /// Returns whether this indicator should be included in liveness checks.
    fn include_in_liveness(&self) -> bool {
        false
    }
}

/// Memory health indicator that checks system memory usage.
pub struct MemoryHealthIndicator {
    /// Threshold percentage above which status becomes DEGRADED
    pub degraded_threshold: f64,
    /// Threshold percentage above which status becomes DOWN
    pub critical_threshold: f64,
}

impl Default for MemoryHealthIndicator {
    fn default() -> Self {
        Self {
            degraded_threshold: 80.0,
            critical_threshold: 95.0,
        }
    }
}

impl MemoryHealthIndicator {
    /// Creates a new memory health indicator with default thresholds
    pub fn new() -> Self {
        Self::default()
    }

    /// Creates a new memory health indicator with custom thresholds
    pub fn with_thresholds(degraded: f64, critical: f64) -> Self {
        Self {
            degraded_threshold: degraded,
            critical_threshold: critical,
        }
    }
}

#[async_trait]
impl HealthIndicator for MemoryHealthIndicator {
    fn name(&self) -> &str {
        "memory"
    }

    async fn check(&self) -> HealthCheckResult {
        let start = Instant::now();

        // Get memory info (platform-specific implementation)
        #[cfg(target_os = "linux")]
        let (total, available) = get_linux_memory_info();

        #[cfg(not(target_os = "linux"))]
        let (total, available) = (0u64, 0u64);

        let duration = start.elapsed();

        if total == 0 {
            return HealthCheckResult::unknown("memory")
                .with_detail("reason", "Unable to read memory info")
                .with_duration(duration);
        }

        let used = total.saturating_sub(available);
        let usage_percent = (used as f64 / total as f64) * 100.0;

        let status = if usage_percent >= self.critical_threshold {
            HealthStatus::Down
        } else if usage_percent >= self.degraded_threshold {
            HealthStatus::Degraded
        } else {
            HealthStatus::Up
        };

        let mut result = HealthCheckResult {
            name: "memory".to_string(),
            status,
            details: HashMap::new(),
            duration_ms: Some(duration.as_millis() as u64),
            error: None,
            timestamp: Some(current_timestamp()),
        };

        result
            .details
            .insert("total_mb".to_string(), format!("{}", total / (1024 * 1024)));
        result.details.insert(
            "available_mb".to_string(),
            format!("{}", available / (1024 * 1024)),
        );
        result
            .details
            .insert("used_mb".to_string(), format!("{}", used / (1024 * 1024)));
        result
            .details
            .insert("usage_percent".to_string(), format!("{:.1}", usage_percent));

        result
    }
}

/// Disk health indicator that checks available disk space.
pub struct DiskHealthIndicator {
    /// Path to check disk space for
    pub path: String,
    /// Threshold percentage of used space above which status becomes DEGRADED
    pub degraded_threshold: f64,
    /// Threshold percentage of used space above which status becomes DOWN
    pub critical_threshold: f64,
}

impl Default for DiskHealthIndicator {
    fn default() -> Self {
        Self {
            path: "/".to_string(),
            degraded_threshold: 80.0,
            critical_threshold: 95.0,
        }
    }
}

impl DiskHealthIndicator {
    /// Creates a new disk health indicator for the given path
    pub fn new(path: impl Into<String>) -> Self {
        Self {
            path: path.into(),
            ..Default::default()
        }
    }

    /// Creates a new disk health indicator with custom thresholds
    pub fn with_thresholds(mut self, degraded: f64, critical: f64) -> Self {
        self.degraded_threshold = degraded;
        self.critical_threshold = critical;
        self
    }
}

#[async_trait]
impl HealthIndicator for DiskHealthIndicator {
    fn name(&self) -> &str {
        "disk"
    }

    async fn check(&self) -> HealthCheckResult {
        let start = Instant::now();

        // Get disk info (platform-specific implementation)
        #[cfg(unix)]
        let disk_info = get_unix_disk_info(&self.path);

        #[cfg(not(unix))]
        let disk_info: Option<(u64, u64)> = None;

        let duration = start.elapsed();

        match disk_info {
            Some((total, available)) => {
                let used = total.saturating_sub(available);
                let usage_percent = if total > 0 {
                    (used as f64 / total as f64) * 100.0
                } else {
                    0.0
                };

                let status = if usage_percent >= self.critical_threshold {
                    HealthStatus::Down
                } else if usage_percent >= self.degraded_threshold {
                    HealthStatus::Degraded
                } else {
                    HealthStatus::Up
                };

                let mut result = HealthCheckResult {
                    name: "disk".to_string(),
                    status,
                    details: HashMap::new(),
                    duration_ms: Some(duration.as_millis() as u64),
                    error: None,
                    timestamp: Some(current_timestamp()),
                };

                result.details.insert("path".to_string(), self.path.clone());
                result.details.insert(
                    "total_gb".to_string(),
                    format!("{:.1}", total as f64 / 1_073_741_824.0),
                );
                result.details.insert(
                    "available_gb".to_string(),
                    format!("{:.1}", available as f64 / 1_073_741_824.0),
                );
                result.details.insert(
                    "used_gb".to_string(),
                    format!("{:.1}", used as f64 / 1_073_741_824.0),
                );
                result
                    .details
                    .insert("usage_percent".to_string(), format!("{:.1}", usage_percent));

                result
            }
            None => HealthCheckResult::unknown("disk")
                .with_detail("path", &self.path)
                .with_detail("reason", "Unable to read disk info")
                .with_duration(duration),
        }
    }
}

/// Uptime health indicator that reports application uptime.
pub struct UptimeHealthIndicator {
    start_time: Instant,
}

impl Default for UptimeHealthIndicator {
    fn default() -> Self {
        Self::new()
    }
}

impl UptimeHealthIndicator {
    /// Creates a new uptime indicator, recording the current time as start time
    pub fn new() -> Self {
        Self {
            start_time: Instant::now(),
        }
    }
}

#[async_trait]
impl HealthIndicator for UptimeHealthIndicator {
    fn name(&self) -> &str {
        "uptime"
    }

    async fn check(&self) -> HealthCheckResult {
        let uptime = self.start_time.elapsed();
        let uptime_secs = uptime.as_secs();

        let days = uptime_secs / 86400;
        let hours = (uptime_secs % 86400) / 3600;
        let minutes = (uptime_secs % 3600) / 60;
        let seconds = uptime_secs % 60;

        HealthCheckResult::up("uptime")
            .with_detail("uptime_seconds", uptime_secs.to_string())
            .with_detail(
                "uptime_human",
                format!("{}d {}h {}m {}s", days, hours, minutes, seconds),
            )
    }

    fn include_in_liveness(&self) -> bool {
        true
    }
}

/// Service for managing and executing health checks.
pub struct HealthService {
    indicators: RwLock<Vec<Arc<dyn HealthIndicator>>>,
    info: RwLock<Option<HealthInfo>>,
    start_time: Instant,
}

impl Default for HealthService {
    fn default() -> Self {
        Self::new()
    }
}

impl HealthService {
    /// Creates a new health service
    pub fn new() -> Self {
        Self {
            indicators: RwLock::new(Vec::new()),
            info: RwLock::new(None),
            start_time: Instant::now(),
        }
    }

    /// Creates a health service with default indicators (memory, disk, uptime)
    pub fn with_defaults() -> Self {
        // Note: indicators are added asynchronously, so use builder pattern for sync construction
        Self::new()
    }

    /// Registers a health indicator
    pub async fn register(&self, indicator: impl HealthIndicator + 'static) {
        let mut indicators = self.indicators.write().await;
        indicators.push(Arc::new(indicator));
    }

    /// Sets the application info
    pub async fn set_info(&self, info: HealthInfo) {
        let mut app_info = self.info.write().await;
        *app_info = Some(info);
    }

    /// Performs a full health check on all registered indicators
    pub async fn check(&self) -> HealthResponse {
        let indicators = self.indicators.read().await;
        let mut response = HealthResponse::new(HealthStatus::Up);

        // Add info with uptime
        if let Some(mut info) = self.info.read().await.clone() {
            info.uptime_seconds = Some(self.start_time.elapsed().as_secs());
            response.info = Some(info);
        }

        // Run all health checks concurrently
        let futures: Vec<_> = indicators
            .iter()
            .map(|indicator| {
                let indicator = Arc::clone(indicator);
                async move {
                    let start = Instant::now();
                    let mut result = indicator.check().await;
                    if result.duration_ms.is_none() {
                        result.duration_ms = Some(start.elapsed().as_millis() as u64);
                    }
                    result
                }
            })
            .collect();

        let results = join_all(futures).await;

        for result in results {
            response.components.insert(result.name.clone(), result);
        }

        response.calculate_status();
        response
    }

    /// Performs a liveness check (minimal check to verify the app is running)
    pub async fn check_liveness(&self) -> HealthResponse {
        let indicators = self.indicators.read().await;
        let mut response = HealthResponse::new(HealthStatus::Up);

        // Only include liveness indicators
        let liveness_indicators: Vec<_> = indicators
            .iter()
            .filter(|i| i.include_in_liveness())
            .cloned()
            .collect();

        let futures: Vec<_> = liveness_indicators
            .iter()
            .map(|indicator| {
                let indicator = Arc::clone(indicator);
                async move {
                    let start = Instant::now();
                    let mut result = indicator.check().await;
                    if result.duration_ms.is_none() {
                        result.duration_ms = Some(start.elapsed().as_millis() as u64);
                    }
                    result
                }
            })
            .collect();

        let results = join_all(futures).await;

        for result in results {
            response.components.insert(result.name.clone(), result);
        }

        // Liveness is UP if the application is responding
        response.status = HealthStatus::Up;
        response
    }

    /// Performs a readiness check (checks if the app can serve traffic)
    pub async fn check_readiness(&self) -> HealthResponse {
        let indicators = self.indicators.read().await;
        let mut response = HealthResponse::new(HealthStatus::Up);

        // Only include readiness indicators
        let readiness_indicators: Vec<_> = indicators
            .iter()
            .filter(|i| i.include_in_readiness())
            .cloned()
            .collect();

        let futures: Vec<_> = readiness_indicators
            .iter()
            .map(|indicator| {
                let indicator = Arc::clone(indicator);
                async move {
                    let start = Instant::now();
                    let mut result = indicator.check().await;
                    if result.duration_ms.is_none() {
                        result.duration_ms = Some(start.elapsed().as_millis() as u64);
                    }
                    result
                }
            })
            .collect();

        let results = join_all(futures).await;

        for result in results {
            response.components.insert(result.name.clone(), result);
        }

        response.calculate_status();
        response
    }

    /// Returns the number of registered indicators
    pub async fn indicator_count(&self) -> usize {
        self.indicators.read().await.len()
    }
}

// Platform-specific implementations

#[cfg(target_os = "linux")]
fn get_linux_memory_info() -> (u64, u64) {
    use std::fs;

    let meminfo = match fs::read_to_string("/proc/meminfo") {
        Ok(content) => content,
        Err(_) => return (0, 0),
    };

    let mut total: u64 = 0;
    let mut available: u64 = 0;

    for line in meminfo.lines() {
        let parts: Vec<&str> = line.split_whitespace().collect();
        if parts.len() >= 2 {
            let value: u64 = parts[1].parse().unwrap_or(0) * 1024; // Convert from kB to bytes
            match parts[0] {
                "MemTotal:" => total = value,
                "MemAvailable:" => available = value,
                _ => {}
            }
        }
    }

    (total, available)
}

#[cfg(unix)]
fn get_unix_disk_info(path: &str) -> Option<(u64, u64)> {
    use std::process::Command;

    // Use df command to get disk info (more portable than libc statvfs)
    let output = Command::new("df")
        .args(["-B1", path]) // Use 1-byte blocks for exact values
        .output()
        .ok()?;

    if !output.status.success() {
        return None;
    }

    let stdout = String::from_utf8_lossy(&output.stdout);
    let lines: Vec<&str> = stdout.lines().collect();

    // Skip header line, parse the data line
    if lines.len() < 2 {
        return None;
    }

    let parts: Vec<&str> = lines[1].split_whitespace().collect();
    if parts.len() < 4 {
        return None;
    }

    // df output: Filesystem 1B-blocks Used Available Use% Mounted
    let total: u64 = parts[1].parse().ok()?;
    let available: u64 = parts[3].parse().ok()?;

    Some((total, available))
}

/// Returns the current Unix timestamp in seconds
fn current_timestamp() -> u64 {
    SystemTime::now()
        .duration_since(UNIX_EPOCH)
        .map(|d| d.as_secs())
        .unwrap_or(0)
}

/// Builder for creating a HealthService with fluent API
pub struct HealthServiceBuilder {
    indicators: Vec<Arc<dyn HealthIndicator>>,
    info: Option<HealthInfo>,
}

impl Default for HealthServiceBuilder {
    fn default() -> Self {
        Self::new()
    }
}

impl HealthServiceBuilder {
    /// Creates a new builder
    pub fn new() -> Self {
        Self {
            indicators: Vec::new(),
            info: None,
        }
    }

    /// Adds a health indicator
    pub fn with_indicator(mut self, indicator: impl HealthIndicator + 'static) -> Self {
        self.indicators.push(Arc::new(indicator));
        self
    }

    /// Adds default indicators (memory, disk, uptime)
    pub fn with_defaults(self) -> Self {
        self.with_indicator(MemoryHealthIndicator::default())
            .with_indicator(DiskHealthIndicator::default())
            .with_indicator(UptimeHealthIndicator::default())
    }

    /// Sets the application info
    pub fn with_info(mut self, info: HealthInfo) -> Self {
        self.info = Some(info);
        self
    }

    /// Builds the health service
    pub fn build(self) -> HealthService {
        HealthService {
            indicators: RwLock::new(self.indicators),
            info: RwLock::new(self.info),
            start_time: Instant::now(),
        }
    }
}

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

    #[test]
    fn test_health_status_is_healthy() {
        assert!(HealthStatus::Up.is_healthy());
        assert!(HealthStatus::Degraded.is_healthy());
        assert!(!HealthStatus::Down.is_healthy());
        assert!(!HealthStatus::Unknown.is_healthy());
    }

    #[test]
    fn test_health_status_http_codes() {
        assert_eq!(HealthStatus::Up.http_status_code(), 200);
        assert_eq!(HealthStatus::Degraded.http_status_code(), 200);
        assert_eq!(HealthStatus::Down.http_status_code(), 503);
        assert_eq!(HealthStatus::Unknown.http_status_code(), 503);
    }

    #[test]
    fn test_health_check_result_builders() {
        let up = HealthCheckResult::up("test");
        assert_eq!(up.status, HealthStatus::Up);
        assert_eq!(up.name, "test");

        let down = HealthCheckResult::down("test");
        assert_eq!(down.status, HealthStatus::Down);

        let degraded = HealthCheckResult::degraded("test");
        assert_eq!(degraded.status, HealthStatus::Degraded);

        let unknown = HealthCheckResult::unknown("test");
        assert_eq!(unknown.status, HealthStatus::Unknown);
    }

    #[test]
    fn test_health_check_result_with_details() {
        let result = HealthCheckResult::up("database")
            .with_detail("type", "postgresql")
            .with_detail("pool_size", "10");

        assert_eq!(result.details.get("type"), Some(&"postgresql".to_string()));
        assert_eq!(result.details.get("pool_size"), Some(&"10".to_string()));
    }

    #[test]
    fn test_health_check_result_with_error() {
        let result = HealthCheckResult::up("database").with_error("Connection failed");

        assert_eq!(result.status, HealthStatus::Down);
        assert_eq!(result.error, Some("Connection failed".to_string()));
    }

    #[test]
    fn test_health_response_calculate_status() {
        let mut response = HealthResponse::new(HealthStatus::Up)
            .with_component(HealthCheckResult::up("db"))
            .with_component(HealthCheckResult::up("cache"));

        response.calculate_status();
        assert_eq!(response.status, HealthStatus::Up);

        // Add a down component
        response
            .components
            .insert("external".to_string(), HealthCheckResult::down("external"));
        response.calculate_status();
        assert_eq!(response.status, HealthStatus::Down);
    }

    #[test]
    fn test_health_info_builder() {
        let info = HealthInfo::new("my-app")
            .with_version("1.0.0")
            .with_description("Test application");

        assert_eq!(info.name, Some("my-app".to_string()));
        assert_eq!(info.version, Some("1.0.0".to_string()));
        assert_eq!(info.description, Some("Test application".to_string()));
    }

    #[tokio::test]
    async fn test_health_service_register() {
        let service = HealthService::new();
        service.register(UptimeHealthIndicator::new()).await;

        assert_eq!(service.indicator_count().await, 1);
    }

    #[tokio::test]
    async fn test_health_service_check() {
        let service = HealthServiceBuilder::new()
            .with_indicator(UptimeHealthIndicator::new())
            .build();

        let response = service.check().await;
        assert_eq!(response.status, HealthStatus::Up);
        assert!(response.components.contains_key("uptime"));
    }

    #[tokio::test]
    async fn test_health_service_builder() {
        let service = HealthServiceBuilder::new()
            .with_info(HealthInfo::new("test-app").with_version("1.0.0"))
            .with_indicator(UptimeHealthIndicator::new())
            .build();

        let response = service.check().await;
        assert!(response.info.is_some());
        assert_eq!(response.info.unwrap().name, Some("test-app".to_string()));
    }

    #[test]
    fn test_health_status_display() {
        assert_eq!(format!("{}", HealthStatus::Up), "UP");
        assert_eq!(format!("{}", HealthStatus::Down), "DOWN");
        assert_eq!(format!("{}", HealthStatus::Degraded), "DEGRADED");
        assert_eq!(format!("{}", HealthStatus::Unknown), "UNKNOWN");
    }

    #[tokio::test]
    async fn test_uptime_indicator() {
        let indicator = UptimeHealthIndicator::new();

        // Wait a tiny bit to ensure uptime is measurable
        tokio::time::sleep(Duration::from_millis(10)).await;

        let result = indicator.check().await;
        assert_eq!(result.status, HealthStatus::Up);
        assert!(result.details.contains_key("uptime_seconds"));
        assert!(result.details.contains_key("uptime_human"));
    }

    #[tokio::test]
    async fn test_memory_indicator() {
        let indicator = MemoryHealthIndicator::default();
        let result = indicator.check().await;

        // On non-Linux systems, this will return Unknown
        #[cfg(target_os = "linux")]
        {
            assert!(result.details.contains_key("total_mb"));
            assert!(result.details.contains_key("available_mb"));
        }
    }

    #[tokio::test]
    async fn test_disk_indicator() {
        let indicator = DiskHealthIndicator::new("/");
        let result = indicator.check().await;

        #[cfg(unix)]
        {
            assert!(result.details.contains_key("path"));
        }
    }

    #[test]
    fn test_health_response_serialization() {
        let response =
            HealthResponse::new(HealthStatus::Up).with_component(HealthCheckResult::up("test"));

        let json = serde_json::to_string(&response).unwrap();
        assert!(json.contains("\"status\":\"UP\""));
    }
}