// Container Health Monitor
// Checks container health every 60s, auto-restarts unhealthy containers (max 3 times)
// with exponential backoff (10s, 30s, 90s), dependency-aware startup ordering,
// and sends WebSocket notifications to the UI on failure.

use crate::data_model::{Notification, NotificationLevel};
use crate::state::StateManager;
use crate::webhooks::{self, WebhookEvent};
use std::collections::HashMap;
use std::path::PathBuf;
use std::sync::Arc;
use std::time::Instant;
use tracing::{debug, info, warn};

const MAX_RESTART_ATTEMPTS: u32 = 3;
const CHECK_INTERVAL_SECS: u64 = 60;
/// Backoff delays per attempt: 10s, 30s, 90s
const BACKOFF_DELAYS_SECS: [u64; 3] = [10, 30, 90];
/// Reset restart counter after 1 hour of stability
const STABILITY_RESET_SECS: u64 = 3600;

/// Container startup tier for dependency ordering.
/// Lower tiers start first. Containers in the same tier start together.
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
enum StartupTier {
    /// Databases: postgres, redis, mariadb, mysql
    Database = 0,
    /// Core infrastructure: bitcoin-knots, bitcoin-core
    CoreInfra = 1,
    /// Services depending on core: lnd, electrs, nbxplorer
    DependentService = 2,
    /// Application layer: mempool-api, btcpay-server, fedimint, nextcloud, etc.
    Application = 3,
    /// UI/frontend containers: mempool-web, bitcoin-ui, lnd-ui
    Frontend = 4,
}

fn container_tier(name: &str) -> StartupTier {
    let id = name.strip_prefix("archy-").unwrap_or(name);
    match id {
        // Tier 0: Databases
        "btcpay-db" | "mempool-db" | "penpot-postgres" | "immich_postgres"
        | "immich_redis" | "penpot-valkey" | "endurain-db" | "nextcloud-db" => StartupTier::Database,

        // Tier 1: Core infrastructure
        "bitcoin-knots" | "bitcoin-core" | "bitcoin" => StartupTier::CoreInfra,

        // Tier 2: Dependent services
        "lnd" | "mempool-electrs" | "electrs" | "nbxplorer" => StartupTier::DependentService,

        // Tier 4: Frontend/UI
        "mempool-web" | "bitcoin-ui" | "lnd-ui" | "electrs-ui"
        | "penpot-frontend" | "penpot-exporter" => StartupTier::Frontend,

        // Tier 3: Everything else
        _ => StartupTier::Application,
    }
}

/// Track restart attempts per container with exponential backoff and stability reset.
struct RestartTracker {
    attempts: HashMap<String, u32>,
    last_failure: HashMap<String, Instant>,
    last_healthy: HashMap<String, Instant>,
}

impl RestartTracker {
    fn new() -> Self {
        Self {
            attempts: HashMap::new(),
            last_failure: HashMap::new(),
            last_healthy: HashMap::new(),
        }
    }

    /// Record a restart attempt. Returns false if max attempts exceeded.
    fn record_attempt(&mut self, name: &str) -> bool {
        let count = self.attempts.entry(name.to_string()).or_insert(0);
        *count += 1;
        self.last_failure.insert(name.to_string(), Instant::now());
        *count <= MAX_RESTART_ATTEMPTS
    }

    /// Clear restart count when a container is healthy again.
    fn clear(&mut self, name: &str) {
        self.attempts.remove(name);
        self.last_failure.remove(name);
        self.last_healthy.insert(name.to_string(), Instant::now());
    }

    fn attempt_count(&self, name: &str) -> u32 {
        *self.attempts.get(name).unwrap_or(&0)
    }

    /// Get the backoff delay in seconds for the current attempt number.
    fn backoff_delay_secs(&self, name: &str) -> u64 {
        let attempts = self.attempt_count(name);
        if attempts == 0 {
            return BACKOFF_DELAYS_SECS[0];
        }
        let idx = (attempts as usize).saturating_sub(1).min(BACKOFF_DELAYS_SECS.len() - 1);
        BACKOFF_DELAYS_SECS[idx]
    }

    /// Check if enough time has passed since last failure for the backoff delay.
    fn backoff_elapsed(&self, name: &str) -> bool {
        let delay = self.backoff_delay_secs(name);
        match self.last_failure.get(name) {
            Some(last) => last.elapsed().as_secs() >= delay,
            None => true,
        }
    }

    /// Check if a failed container should have its counter reset (1h stability window).
    fn should_reset_failed(&self, name: &str) -> bool {
        if self.attempt_count(name) < MAX_RESTART_ATTEMPTS {
            return false;
        }
        match self.last_failure.get(name) {
            Some(last) => last.elapsed().as_secs() >= STABILITY_RESET_SECS,
            None => false,
        }
    }
}

#[derive(Debug, Clone)]
struct ContainerHealth {
    name: String,
    app_id: String,
    state: String,
    healthy: bool,
}

/// Track container memory usage over time for leak detection.
struct MemoryTracker {
    /// Per-container memory samples: (timestamp, rss_bytes)
    samples: HashMap<String, Vec<(Instant, u64)>>,
}

impl MemoryTracker {
    fn new() -> Self {
        Self {
            samples: HashMap::new(),
        }
    }

    /// Record a memory sample for a container.
    fn record(&mut self, name: &str, rss_bytes: u64) {
        let entry = self.samples.entry(name.to_string()).or_default();
        entry.push((Instant::now(), rss_bytes));
        // Keep only last 288 samples (24h at 5min intervals)
        if entry.len() > 288 {
            entry.remove(0);
        }
    }

    /// Check if a container's memory has grown by more than 50% over the tracking period.
    /// Returns Some(growth_percent) if a leak is detected, None otherwise.
    fn check_leak(&self, name: &str) -> Option<f64> {
        let samples = self.samples.get(name)?;
        if samples.len() < 12 {
            return None; // Need at least 1 hour of data
        }
        let (oldest_time, oldest_rss) = samples.first()?;
        let (_, latest_rss) = samples.last()?;
        let elapsed_hours = oldest_time.elapsed().as_secs() as f64 / 3600.0;
        if elapsed_hours < 1.0 || *oldest_rss == 0 {
            return None;
        }
        let growth = (*latest_rss as f64 - *oldest_rss as f64) / *oldest_rss as f64 * 100.0;
        if growth > 50.0 {
            Some(growth)
        } else {
            None
        }
    }

    fn remove(&mut self, name: &str) {
        self.samples.remove(name);
    }
}

/// Query container memory stats from podman.
async fn check_container_memory() -> HashMap<String, u64> {
    let output = match tokio::process::Command::new("sudo")
        .args(["podman", "stats", "--no-stream", "--format", "{{.Name}} {{.MemUsage}}"])
        .output()
        .await
    {
        Ok(o) if o.status.success() => o,
        _ => return HashMap::new(),
    };

    let stdout = String::from_utf8_lossy(&output.stdout);
    let mut result = HashMap::new();
    for line in stdout.lines() {
        let parts: Vec<&str> = line.split_whitespace().collect();
        if parts.len() >= 2 {
            let name = parts[0].to_string();
            // Parse memory like "123.4MiB", "1.2GiB", "45.6kB"
            let mem_str = parts[1];
            if let Some(bytes) = parse_memory_string(mem_str) {
                result.insert(name, bytes);
            }
        }
    }
    result
}

/// Parse memory string like "123.4MiB" or "1.2GiB" to bytes.
fn parse_memory_string(s: &str) -> Option<u64> {
    let s = s.trim();
    if s.ends_with("GiB") {
        let num: f64 = s.strip_suffix("GiB")?.parse().ok()?;
        Some((num * 1_073_741_824.0) as u64)
    } else if s.ends_with("MiB") {
        let num: f64 = s.strip_suffix("MiB")?.parse().ok()?;
        Some((num * 1_048_576.0) as u64)
    } else if s.ends_with("KiB") || s.ends_with("kB") {
        let suffix = if s.ends_with("KiB") { "KiB" } else { "kB" };
        let num: f64 = s.strip_suffix(suffix)?.parse().ok()?;
        Some((num * 1024.0) as u64)
    } else if s.ends_with("B") {
        let num: f64 = s.strip_suffix('B')?.parse().ok()?;
        Some(num as u64)
    } else {
        None
    }
}

/// Query all containers and their health status.
async fn check_containers() -> Vec<ContainerHealth> {
    let output = match tokio::process::Command::new("sudo")
        .args(["podman", "ps", "-a", "--format", "json"])
        .output()
        .await
    {
        Ok(o) if o.status.success() => o,
        _ => return Vec::new(),
    };

    let stdout = String::from_utf8_lossy(&output.stdout);
    let containers: Vec<serde_json::Value> =
        serde_json::from_str(&stdout).unwrap_or_default();

    // Backend services to skip
    let skip = [
        "btcpay-db", "nbxplorer", "mempool-db", "mempool-api",
        "penpot-postgres", "penpot-backend", "penpot-exporter", "penpot-valkey",
        "penpot-mailcatch", "immich_postgres", "immich_redis",
        "endurain-db", "nextcloud-db",
    ];

    containers
        .iter()
        .filter_map(|c| {
            let name = c.get("Names").and_then(|v| {
                if let Some(arr) = v.as_array() {
                    arr.first().and_then(|n| n.as_str()).map(|s| s.to_string())
                } else {
                    v.as_str().map(|s| s.to_string())
                }
            })?;

            let app_id = name
                .strip_prefix("archy-")
                .unwrap_or(&name)
                .to_string();

            if skip.contains(&app_id.as_str()) || app_id.ends_with("-ui") {
                return None;
            }

            let state = c.get("State")
                .and_then(|v| v.as_str())
                .unwrap_or("unknown")
                .to_lowercase();

            let healthy = state == "running";

            Some(ContainerHealth {
                name,
                app_id,
                state,
                healthy,
            })
        })
        .collect()
}

/// Try to restart a container.
async fn restart_container(name: &str) -> bool {
    info!("Auto-restarting unhealthy container: {}", name);
    let result = tokio::process::Command::new("sudo")
        .args(["podman", "start", name])
        .output()
        .await;

    match result {
        Ok(output) if output.status.success() => {
            info!("Successfully restarted container: {}", name);
            true
        }
        Ok(output) => {
            let stderr = String::from_utf8_lossy(&output.stderr);
            warn!("Failed to restart container {}: {}", name, stderr.trim());
            false
        }
        Err(e) => {
            warn!("Failed to execute podman start for {}: {}", name, e);
            false
        }
    }
}

/// Spawn the health monitor background task.
pub fn spawn_health_monitor(state: Arc<StateManager>, data_dir: PathBuf) {
    tokio::spawn(async move {
        // Wait 2 minutes for containers to start up
        tokio::time::sleep(std::time::Duration::from_secs(120)).await;

        let mut tracker = RestartTracker::new();
        let mut mem_tracker = MemoryTracker::new();
        let mut mem_check_counter: u32 = 0;
        let mut interval = tokio::time::interval(std::time::Duration::from_secs(CHECK_INTERVAL_SECS));

        loop {
            interval.tick().await;
            mem_check_counter += 1;

            // Check container memory every 5 minutes (every 5th health check)
            if mem_check_counter % 5 == 0 {
                let mem_stats = check_container_memory().await;
                for (name, rss) in &mem_stats {
                    mem_tracker.record(name, *rss);
                    if let Some(growth) = mem_tracker.check_leak(name) {
                        warn!("Potential memory leak in {}: {:.0}% growth over tracking period", name, growth);
                    }
                }
            }

            let containers = check_containers().await;
            if containers.is_empty() {
                continue;
            }

            // Sort containers by startup tier so databases restart before dependent services
            let mut unhealthy: Vec<&ContainerHealth> = Vec::new();
            let mut state_changed = false;
            let (mut data, _) = state.get_snapshot().await;

            for container in &containers {
                if container.healthy {
                    if tracker.attempt_count(&container.name) > 0 {
                        info!("Container {} is healthy again after restart", container.name);
                        tracker.clear(&container.name);
                    }
                    continue;
                }
                if container.state == "exited" || container.state == "stopped" {
                    unhealthy.push(container);
                }
            }

            // Sort by startup tier: databases first, then core, then dependent, then apps, then UIs
            unhealthy.sort_by_key(|c| container_tier(&c.name));

            let mut prev_tier: Option<StartupTier> = None;
            for container in &unhealthy {
                let tier = container_tier(&container.name);
                let attempts = tracker.attempt_count(&container.name);

                // Reset counter after 1 hour for permanently failed containers
                if tracker.should_reset_failed(&container.name) {
                    info!("Resetting restart counter for {} after {}s stability window", container.name, STABILITY_RESET_SECS);
                    tracker.clear(&container.name);
                }

                if tracker.attempt_count(&container.name) >= MAX_RESTART_ATTEMPTS {
                    debug!("Container {} exceeded max restart attempts ({})", container.name, MAX_RESTART_ATTEMPTS);
                    continue;
                }

                // Wait for backoff delay before retrying
                if !tracker.backoff_elapsed(&container.name) {
                    let delay = tracker.backoff_delay_secs(&container.name);
                    debug!("Container {} waiting for backoff ({}s)", container.name, delay);
                    continue;
                }

                // When transitioning to a higher tier, wait briefly for previous tier to stabilize
                if let Some(prev) = prev_tier {
                    if tier > prev {
                        tokio::time::sleep(std::time::Duration::from_secs(5)).await;
                    }
                }
                prev_tier = Some(tier);

                if tracker.record_attempt(&container.name) {
                    let attempt = tracker.attempt_count(&container.name);
                    info!("Restarting {} (tier {:?}, attempt {}/{}, backoff {}s)",
                        container.name, tier, attempt, MAX_RESTART_ATTEMPTS,
                        BACKOFF_DELAYS_SECS.get(attempt.saturating_sub(1) as usize).unwrap_or(&90));

                    let restarted = restart_container(&container.name).await;

                    if !restarted || attempt >= MAX_RESTART_ATTEMPTS {
                        let notification = Notification {
                            id: format!("health-{}-{}", container.app_id, chrono::Utc::now().timestamp()),
                            level: NotificationLevel::Error,
                            title: format!("{} is unhealthy", container.app_id),
                            message: if restarted {
                                format!(
                                    "Container restarted ({}/{} attempts). May need manual attention.",
                                    attempt, MAX_RESTART_ATTEMPTS
                                )
                            } else {
                                format!(
                                    "Auto-restart failed (attempt {}/{}). Container state: {}",
                                    attempt, MAX_RESTART_ATTEMPTS, container.state
                                )
                            },
                            timestamp: chrono::Utc::now().to_rfc3339(),
                            app_id: Some(container.app_id.clone()),
                        };

                        data.notifications.push(notification.clone());
                        if data.notifications.len() > 20 {
                            data.notifications = data.notifications.split_off(data.notifications.len() - 20);
                        }
                        state_changed = true;

                        let webhook_payload = webhooks::WebhookPayload {
                            event: WebhookEvent::ContainerCrash,
                            title: notification.title,
                            message: notification.message,
                            timestamp: notification.timestamp,
                            node_id: String::new(),
                            details: Some(serde_json::json!({
                                "container": container.name,
                                "app_id": container.app_id,
                                "state": container.state,
                                "attempt": attempt,
                                "tier": format!("{:?}", tier),
                            })),
                        };
                        webhooks::send_webhook(&data_dir, webhook_payload).await;
                    }
                }
            }

            if state_changed {
                state.update_data(data).await;
                debug!("Health monitor: state updated with notifications");
            }
        }
    });
}

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

    #[test]
    fn test_restart_tracker_new_is_empty() {
        let tracker = RestartTracker::new();
        assert_eq!(tracker.attempt_count("any-container"), 0);
    }

    #[test]
    fn test_restart_tracker_record_attempt_increments() {
        let mut tracker = RestartTracker::new();
        assert!(tracker.record_attempt("test-container"));
        assert_eq!(tracker.attempt_count("test-container"), 1);

        assert!(tracker.record_attempt("test-container"));
        assert_eq!(tracker.attempt_count("test-container"), 2);

        assert!(tracker.record_attempt("test-container"));
        assert_eq!(tracker.attempt_count("test-container"), 3);
    }

    #[test]
    fn test_restart_tracker_max_attempts_exceeded() {
        let mut tracker = RestartTracker::new();
        for i in 1..=MAX_RESTART_ATTEMPTS {
            assert!(
                tracker.record_attempt("container-a"),
                "Attempt {} should be allowed",
                i
            );
        }
        assert!(!tracker.record_attempt("container-a"));
        assert_eq!(tracker.attempt_count("container-a"), MAX_RESTART_ATTEMPTS + 1);
    }

    #[test]
    fn test_restart_tracker_independent_containers() {
        let mut tracker = RestartTracker::new();
        tracker.record_attempt("container-a");
        tracker.record_attempt("container-a");
        tracker.record_attempt("container-b");

        assert_eq!(tracker.attempt_count("container-a"), 2);
        assert_eq!(tracker.attempt_count("container-b"), 1);
        assert_eq!(tracker.attempt_count("container-c"), 0);
    }

    #[test]
    fn test_restart_tracker_clear_resets_count() {
        let mut tracker = RestartTracker::new();
        tracker.record_attempt("container-x");
        tracker.record_attempt("container-x");
        assert_eq!(tracker.attempt_count("container-x"), 2);

        tracker.clear("container-x");
        assert_eq!(tracker.attempt_count("container-x"), 0);
    }

    #[test]
    fn test_restart_tracker_clear_allows_new_attempts() {
        let mut tracker = RestartTracker::new();
        for _ in 0..=MAX_RESTART_ATTEMPTS {
            tracker.record_attempt("container-y");
        }
        assert!(!tracker.record_attempt("container-y"));

        tracker.clear("container-y");
        assert!(tracker.record_attempt("container-y"));
        assert_eq!(tracker.attempt_count("container-y"), 1);
    }

    #[test]
    fn test_restart_tracker_clear_nonexistent_is_safe() {
        let mut tracker = RestartTracker::new();
        tracker.clear("nonexistent");
        assert_eq!(tracker.attempt_count("nonexistent"), 0);
    }

    #[test]
    fn test_container_health_struct() {
        let health = ContainerHealth {
            name: "archy-bitcoin-knots".to_string(),
            app_id: "bitcoin-knots".to_string(),
            state: "running".to_string(),
            healthy: true,
        };
        assert!(health.healthy);
        assert_eq!(health.name, "archy-bitcoin-knots");
        assert_eq!(health.app_id, "bitcoin-knots");
        assert_eq!(health.state, "running");
    }

    #[test]
    fn test_container_health_unhealthy() {
        let health = ContainerHealth {
            name: "archy-mempool-web".to_string(),
            app_id: "mempool-web".to_string(),
            state: "exited".to_string(),
            healthy: false,
        };
        assert!(!health.healthy);
        assert_eq!(health.state, "exited");
    }

    #[test]
    fn test_max_restart_attempts_constant() {
        assert!(MAX_RESTART_ATTEMPTS >= 1);
        assert!(MAX_RESTART_ATTEMPTS <= 10);
        assert_eq!(MAX_RESTART_ATTEMPTS, 3);
    }

    #[test]
    fn test_check_interval_constant() {
        assert_eq!(CHECK_INTERVAL_SECS, 60);
    }

    #[test]
    fn test_backoff_delays() {
        let tracker = RestartTracker::new();
        // Before any attempts, delay is first backoff
        assert_eq!(tracker.backoff_delay_secs("test"), BACKOFF_DELAYS_SECS[0]);
    }

    #[test]
    fn test_backoff_delays_escalate() {
        let mut tracker = RestartTracker::new();
        tracker.record_attempt("test");
        assert_eq!(tracker.backoff_delay_secs("test"), BACKOFF_DELAYS_SECS[0]); // 10s
        tracker.record_attempt("test");
        assert_eq!(tracker.backoff_delay_secs("test"), BACKOFF_DELAYS_SECS[1]); // 30s
        tracker.record_attempt("test");
        assert_eq!(tracker.backoff_delay_secs("test"), BACKOFF_DELAYS_SECS[2]); // 90s
    }

    #[test]
    fn test_backoff_elapsed_true_for_new() {
        let tracker = RestartTracker::new();
        assert!(tracker.backoff_elapsed("test"));
    }

    #[test]
    fn test_stability_reset_not_triggered_early() {
        let mut tracker = RestartTracker::new();
        tracker.record_attempt("test");
        assert!(!tracker.should_reset_failed("test"));
    }

    #[test]
    fn test_container_tier_database() {
        assert_eq!(container_tier("archy-btcpay-db"), StartupTier::Database);
        assert_eq!(container_tier("immich_postgres"), StartupTier::Database);
        assert_eq!(container_tier("penpot-valkey"), StartupTier::Database);
    }

    #[test]
    fn test_container_tier_core() {
        assert_eq!(container_tier("bitcoin-knots"), StartupTier::CoreInfra);
    }

    #[test]
    fn test_container_tier_dependent() {
        assert_eq!(container_tier("lnd"), StartupTier::DependentService);
        assert_eq!(container_tier("mempool-electrs"), StartupTier::DependentService);
        assert_eq!(container_tier("archy-nbxplorer"), StartupTier::DependentService);
    }

    #[test]
    fn test_container_tier_frontend() {
        assert_eq!(container_tier("archy-mempool-web"), StartupTier::Frontend);
        assert_eq!(container_tier("archy-bitcoin-ui"), StartupTier::Frontend);
    }

    #[test]
    fn test_container_tier_application_default() {
        assert_eq!(container_tier("nextcloud"), StartupTier::Application);
        assert_eq!(container_tier("grafana"), StartupTier::Application);
        assert_eq!(container_tier("btcpay-server"), StartupTier::Application);
    }

    #[test]
    fn test_tier_ordering() {
        assert!(StartupTier::Database < StartupTier::CoreInfra);
        assert!(StartupTier::CoreInfra < StartupTier::DependentService);
        assert!(StartupTier::DependentService < StartupTier::Application);
        assert!(StartupTier::Application < StartupTier::Frontend);
    }

    #[test]
    fn test_parse_memory_gib() {
        assert_eq!(parse_memory_string("1.5GiB"), Some(1_610_612_736));
    }

    #[test]
    fn test_parse_memory_mib() {
        assert_eq!(parse_memory_string("256MiB"), Some(268_435_456));
    }

    #[test]
    fn test_parse_memory_kib() {
        assert_eq!(parse_memory_string("512KiB"), Some(524_288));
    }

    #[test]
    fn test_parse_memory_invalid() {
        assert_eq!(parse_memory_string("abc"), None);
    }

    #[test]
    fn test_memory_tracker_no_leak_few_samples() {
        let mut tracker = MemoryTracker::new();
        tracker.record("test", 100_000_000);
        assert!(tracker.check_leak("test").is_none());
    }
}