use std::sync::atomic::{AtomicBool, Ordering};
use std::sync::Arc;
use std::time::Duration;
use tokio::sync::RwLock;
use tauri::{AppHandle, Emitter};
use serde::{Serialize, Deserialize};

use crate::jellyfin::http_client::HttpClient;

// Adaptive polling intervals (matches TypeScript)
const AUTO_CHECK_INTERVAL_MS: u64 = 30000; // 30 seconds when online
const RETRY_CHECK_INTERVAL_MS: u64 = 5000;  // 5 seconds when offline

/// Connectivity status
#[derive(specta::Type, Debug, Clone, Serialize, Deserialize)]
#[serde(rename_all = "camelCase")]
pub struct ConnectivityStatus {
    /// Whether the Jellyfin server is reachable
    pub is_server_reachable: bool,
    /// Last time we checked server reachability (ISO 8601 string)
    pub last_checked: Option<String>,
    /// Error message from last connectivity check
    pub connection_error: Option<String>,
    /// Whether we're currently checking connectivity
    pub is_checking: bool,
}

impl Default for ConnectivityStatus {
    fn default() -> Self {
        Self {
            // Start optimistic - assume online until proven otherwise
            // This prevents the app from appearing offline on startup
            is_server_reachable: true,
            last_checked: None,
            connection_error: None,
            is_checking: false,
        }
    }
}

/// Connectivity change event emitted to frontend
#[derive(specta::Type, Debug, Clone, Serialize)]
#[serde(rename_all = "camelCase")]
struct ConnectivityChangeEvent {
    is_reachable: bool,
}

/// Connectivity monitor for tracking server reachability
pub struct ConnectivityMonitor {
    server_url: Arc<RwLock<Option<String>>>,
    http_client: Arc<HttpClient>,
    status: Arc<RwLock<ConnectivityStatus>>,
    is_monitoring: Arc<AtomicBool>,
    app_handle: Option<AppHandle>,
}

impl ConnectivityMonitor {
    /// Create a new connectivity monitor
    pub fn new(http_client: HttpClient) -> Self {
        Self {
            server_url: Arc::new(RwLock::new(None)),
            http_client: Arc::new(http_client),
            status: Arc::new(RwLock::new(ConnectivityStatus::default())),
            is_monitoring: Arc::new(AtomicBool::new(false)),
            app_handle: None,
        }
    }

    /// Set the Tauri app handle for event emission
    pub fn set_app_handle(&mut self, app_handle: AppHandle) {
        self.app_handle = Some(app_handle);
    }

    /// Update the server URL
    pub async fn set_server_url(&self, url: String) {
        log::info!("[ConnectivityMonitor] Setting server URL: {}", url);
        let mut server_url = self.server_url.write().await;
        *server_url = Some(url.clone());
        drop(server_url);

        // Check new server immediately
        log::info!("[ConnectivityMonitor] Checking reachability of new server...");
        let is_reachable = self.check_reachability().await;
        log::info!("[ConnectivityMonitor] New server is {}", if is_reachable { "REACHABLE" } else { "UNREACHABLE" });
    }

    /// Get current connectivity status
    pub async fn get_status(&self) -> ConnectivityStatus {
        self.status.read().await.clone()
    }

    /// Check if the Jellyfin server is reachable
    pub async fn check_reachability(&self) -> bool {
        // Mark as checking
        {
            let mut status = self.status.write().await;
            status.is_checking = true;
        }

        let server_url = self.server_url.read().await.clone();

        if server_url.is_none() {
            log::warn!("[ConnectivityMonitor] Cannot check reachability: No server URL configured");
            let mut status = self.status.write().await;
            status.is_server_reachable = false;
            status.connection_error = Some("No server URL configured".to_string());
            status.is_checking = false;
            return false;
        }

        let url = server_url.unwrap();
        let ping_url = format!("{}/System/Info/Public", url);

        // Store previous reachability state
        let was_reachable = {
            let status = self.status.read().await;
            status.is_server_reachable
        };

        log::debug!("[ConnectivityMonitor] Pinging server: {}", ping_url);

        // Attempt to ping the server
        let is_reachable = self.http_client.ping(&ping_url).await;

        log::debug!(
            "[ConnectivityMonitor] Ping result: {} (was: {})",
            if is_reachable { "SUCCESS" } else { "FAILED" },
            if was_reachable { "reachable" } else { "unreachable" }
        );

        // Update status
        {
            let mut status = self.status.write().await;
            status.is_server_reachable = is_reachable;
            status.last_checked = Some(chrono::Utc::now().to_rfc3339());
            status.connection_error = if is_reachable {
                None
            } else {
                Some("Server unreachable".to_string())
            };
            status.is_checking = false;
        }

        // Emit events if reachability changed
        if is_reachable != was_reachable {
            self.emit_connectivity_change(is_reachable).await;
        }

        // Emit reconnection event
        if is_reachable && !was_reachable {
            self.emit_server_reconnected().await;
        }

        is_reachable
    }

    /// Mark server as reachable (called after successful API call)
    pub async fn mark_reachable(&self) {
        let mut status = self.status.write().await;
        let was_reachable = status.is_server_reachable;

        status.is_server_reachable = true;
        status.last_checked = Some(chrono::Utc::now().to_rfc3339());
        status.connection_error = None;

        drop(status);

        if !was_reachable {
            log::info!("[ConnectivityMonitor] Server marked as reachable (was unreachable)");
            self.emit_connectivity_change(true).await;
            self.emit_server_reconnected().await;
        }
    }

    /// Mark server as unreachable (called after failed API call)
    pub async fn mark_unreachable(&self, error: Option<String>) {
        let mut status = self.status.write().await;
        let was_reachable = status.is_server_reachable;

        status.is_server_reachable = false;
        status.last_checked = Some(chrono::Utc::now().to_rfc3339());
        status.connection_error = error.or_else(|| Some("Server unreachable".to_string()));

        let error_msg = status.connection_error.clone().unwrap_or_default();
        drop(status);

        if was_reachable {
            log::warn!("[ConnectivityMonitor] Server marked as unreachable (was reachable): {}", error_msg);
            self.emit_connectivity_change(false).await;
        }
    }

    /// Start monitoring connectivity with adaptive polling
    pub async fn start_monitoring(&self) {
        if self.is_monitoring.swap(true, Ordering::SeqCst) {
            log::info!("[ConnectivityMonitor] Already monitoring");
            return;
        }

        log::info!("[ConnectivityMonitor] Starting connectivity monitoring");

        // Perform immediate check before starting background task
        // This ensures we get an accurate state right away instead of assuming offline
        let is_reachable = self.check_reachability().await;
        log::info!("[ConnectivityMonitor] Initial connectivity check: {}", if is_reachable { "ONLINE" } else { "OFFLINE" });

        // Clone Arc references for the background task
        let status = Arc::clone(&self.status);
        let is_monitoring = Arc::clone(&self.is_monitoring);
        let server_url = Arc::clone(&self.server_url);
        let http_client = Arc::clone(&self.http_client);
        let self_clone = Arc::new(ConnectivityMonitorHandle {
            server_url,
            http_client,
            status,
            app_handle: self.app_handle.clone(),
        });

        // Spawn background monitoring task
        tokio::spawn(async move {
            while is_monitoring.load(Ordering::SeqCst) {
                // Determine interval based on current reachability
                let interval_ms = {
                    let status = self_clone.status.read().await;
                    if status.is_server_reachable {
                        AUTO_CHECK_INTERVAL_MS
                    } else {
                        RETRY_CHECK_INTERVAL_MS
                    }
                };

                // Wait for the interval
                tokio::time::sleep(Duration::from_millis(interval_ms)).await;

                // Check if still monitoring
                if !is_monitoring.load(Ordering::SeqCst) {
                    break;
                }

                // Perform connectivity check
                let _ = self_clone.check_reachability().await;
            }

            log::info!("[ConnectivityMonitor] Stopped monitoring");
        });
    }

    /// Stop monitoring connectivity
    pub fn stop_monitoring(&self) {
        log::info!("[ConnectivityMonitor] Stopping connectivity monitoring");
        self.is_monitoring.store(false, Ordering::SeqCst);
    }

    /// Emit connectivity change event to frontend
    async fn emit_connectivity_change(&self, is_reachable: bool) {
        if let Some(app_handle) = &self.app_handle {
            let event = ConnectivityChangeEvent { is_reachable };
            if let Err(e) = app_handle.emit("connectivity:changed", event) {
                log::error!("[ConnectivityMonitor] Failed to emit connectivity change event: {}", e);
            } else {
                log::info!("[ConnectivityMonitor] Emitted connectivity change: {}", is_reachable);
            }
        }
    }

    /// Emit server reconnected event to frontend
    async fn emit_server_reconnected(&self) {
        if let Some(app_handle) = &self.app_handle {
            if let Err(e) = app_handle.emit("connectivity:reconnected", ()) {
                log::error!("[ConnectivityMonitor] Failed to emit reconnection event: {}", e);
            } else {
                log::info!("[ConnectivityMonitor] Emitted server reconnected event");
            }
        }
    }
}

/// Handle for the background monitoring task
struct ConnectivityMonitorHandle {
    server_url: Arc<RwLock<Option<String>>>,
    http_client: Arc<HttpClient>,
    status: Arc<RwLock<ConnectivityStatus>>,
    app_handle: Option<AppHandle>,
}

impl ConnectivityMonitorHandle {
    async fn check_reachability(&self) -> bool {
        let server_url = self.server_url.read().await.clone();

        if server_url.is_none() {
            return false;
        }

        let url = server_url.unwrap();
        let ping_url = format!("{}/System/Info/Public", url);

        // Store previous reachability state
        let was_reachable = {
            let status = self.status.read().await;
            status.is_server_reachable
        };

        // Attempt to ping the server
        let is_reachable = self.http_client.ping(&ping_url).await;

        // Update status
        {
            let mut status = self.status.write().await;
            status.is_server_reachable = is_reachable;
            status.last_checked = Some(chrono::Utc::now().to_rfc3339());
            status.connection_error = if is_reachable {
                None
            } else {
                Some("Server unreachable".to_string())
            };
        }

        // Emit events if reachability changed
        if is_reachable != was_reachable {
            self.emit_connectivity_change(is_reachable).await;
        }

        // Emit reconnection event
        if is_reachable && !was_reachable {
            self.emit_server_reconnected().await;
        }

        is_reachable
    }

    async fn emit_connectivity_change(&self, is_reachable: bool) {
        if let Some(app_handle) = &self.app_handle {
            let event = ConnectivityChangeEvent { is_reachable };
            if let Err(e) = app_handle.emit("connectivity:changed", event) {
                log::error!("[ConnectivityMonitor] Failed to emit connectivity change event: {}", e);
            }
        }
    }

    async fn emit_server_reconnected(&self) {
        if let Some(app_handle) = &self.app_handle {
            if let Err(e) = app_handle.emit("connectivity:reconnected", ()) {
                log::error!("[ConnectivityMonitor] Failed to emit reconnection event: {}", e);
            }
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::jellyfin::http_client::HttpConfig;

    #[test]
    fn test_intervals() {
        // Verify intervals match TypeScript
        assert_eq!(AUTO_CHECK_INTERVAL_MS, 30000);
        assert_eq!(RETRY_CHECK_INTERVAL_MS, 5000);
    }

    #[tokio::test]
    async fn test_default_status() {
        let status = ConnectivityStatus::default();
        // Default is now optimistic (assume online until proven otherwise)
        assert!(status.is_server_reachable);
        assert!(status.last_checked.is_none());
        assert!(status.connection_error.is_none());
        assert!(!status.is_checking);
    }
}