use std::collections::HashMap;
use chrono::{DateTime, Utc};
use chrono_tz::Europe::Stockholm;
use lettre::{Message, SmtpTransport, Transport};
use serde::{Deserialize, Serialize};
use tracing::{info, error, warn};

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct NotificationConfig {
    pub enabled: bool,
    pub smtp_host: String,
    pub smtp_port: u16,
    pub from_email: String,
    pub to_email: String,
    pub rate_limit_minutes: u64,
}

impl Default for NotificationConfig {
    fn default() -> Self {
        Self {
            enabled: false,
            smtp_host: "localhost".to_string(),
            smtp_port: 25,
            from_email: "".to_string(),
            to_email: "".to_string(),
            rate_limit_minutes: 30, // Don't spam notifications
        }
    }
}

#[derive(Debug, Clone, PartialEq)]
pub struct StatusChange {
    pub component: String,
    pub metric: String,
    pub old_status: String,
    pub new_status: String,
    pub timestamp: DateTime<Utc>,
    pub details: Option<String>,
}

pub struct NotificationManager {
    config: NotificationConfig,
    last_status: HashMap<String, String>, // key: "component.metric", value: status
    last_notification: HashMap<String, DateTime<Utc>>, // Rate limiting
}

impl NotificationManager {
    pub fn new(config: NotificationConfig) -> Self {
        Self {
            config,
            last_status: HashMap::new(),
            last_notification: HashMap::new(),
        }
    }

    pub fn update_status(&mut self, component: &str, metric: &str, status: &str) -> Option<StatusChange> {
        self.update_status_with_details(component, metric, status, None)
    }

    pub fn update_status_with_details(&mut self, component: &str, metric: &str, status: &str, details: Option<String>) -> Option<StatusChange> {
        let key = format!("{}.{}", component, metric);
        let old_status = self.last_status.get(&key).cloned();
        
        if let Some(old) = &old_status {
            if old != status {
                let change = StatusChange {
                    component: component.to_string(),
                    metric: metric.to_string(),
                    old_status: old.clone(),
                    new_status: status.to_string(),
                    timestamp: Utc::now(),
                    details,
                };
                
                self.last_status.insert(key, status.to_string());
                
                if self.should_notify(&change) {
                    return Some(change);
                }
            }
        } else {
            // First time seeing this metric - store but don't notify
            self.last_status.insert(key, status.to_string());
        }
        
        None
    }
    
    fn should_notify(&mut self, change: &StatusChange) -> bool {
        if !self.config.enabled {
            info!("Notifications disabled, skipping {}.{}", change.component, change.metric);
            return false;
        }
        
        // Only notify on transitions to warning/critical, or recovery to ok
        let should_send = match (change.old_status.as_str(), change.new_status.as_str()) {
            (_, "warning") | (_, "critical") => true,
            ("warning" | "critical", "ok") => true,
            _ => false,
        };
        
        info!("Status change {}.{}: {} -> {} (notify: {})", 
              change.component, change.metric, change.old_status, change.new_status, should_send);
        
        should_send
    }
    
    fn is_rate_limited(&mut self, change: &StatusChange) -> bool {
        let key = format!("{}.{}", change.component, change.metric);
        
        if let Some(last_time) = self.last_notification.get(&key) {
            let minutes_since = Utc::now().signed_duration_since(*last_time).num_minutes();
            if minutes_since < self.config.rate_limit_minutes as i64 {
                info!("Rate limiting {}.{}: {} minutes since last notification (limit: {})", 
                      change.component, change.metric, minutes_since, self.config.rate_limit_minutes);
                return true;
            }
        }
        
        self.last_notification.insert(key.clone(), Utc::now());
        info!("Not rate limited {}.{}, sending notification", change.component, change.metric);
        false
    }
    
    pub async fn send_notification(&mut self, change: StatusChange) {
        if !self.config.enabled {
            return;
        }
        
        if self.is_rate_limited(&change) {
            warn!("Rate limiting notification for {}.{}", change.component, change.metric);
            return;
        }
        
        let subject = self.format_subject(&change);
        let body = self.format_body(&change);
        
        if let Err(e) = self.send_email(&subject, &body).await {
            error!("Failed to send notification email: {}", e);
        } else {
            info!("Sent notification: {} {}.{} {} → {}", 
                  change.component, change.component, change.metric, 
                  change.old_status, change.new_status);
        }
    }
    
    fn format_subject(&self, change: &StatusChange) -> String {
        let urgency = match change.new_status.as_str() {
            "critical" => "🔴 CRITICAL",
            "warning" => "🟡 WARNING", 
            "ok" => "✅ RESOLVED",
            _ => "ℹ️  STATUS",
        };
        
        format!("{}: {} {} on {}", 
                urgency, 
                change.component, 
                change.metric,
                gethostname::gethostname().to_string_lossy())
    }
    
    fn format_body(&self, change: &StatusChange) -> String {
        let mut body = format!(
            "Status Change Alert\n\
             \n\
             Host: {}\n\
             Component: {}\n\
             Metric: {}\n\
             Status Change: {} → {}\n\
             Time: {}",
            gethostname::gethostname().to_string_lossy(),
            change.component,
            change.metric,
            change.old_status,
            change.new_status,
            change.timestamp.with_timezone(&Stockholm).format("%Y-%m-%d %H:%M:%S CET/CEST")
        );

        if let Some(details) = &change.details {
            body.push_str(&format!("\n\nDetails:\n{}", details));
        }

        body.push_str(&format!(
            "\n\n--\n\
             CM Dashboard Agent\n\
             Generated at {}",
            Utc::now().with_timezone(&Stockholm).format("%Y-%m-%d %H:%M:%S CET/CEST")
        ));

        body
    }
    
    async fn send_email(&self, subject: &str, body: &str) -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
        let email = Message::builder()
            .from(self.config.from_email.parse()?)
            .to(self.config.to_email.parse()?)
            .subject(subject)
            .body(body.to_string())?;

        let mailer = SmtpTransport::builder_dangerous(&self.config.smtp_host)
            .port(self.config.smtp_port)
            .build();

        mailer.send(&email)?;
        Ok(())
    }
}