use async_trait::async_trait;
use cm_dashboard_shared::{Metric, MetricValue, Status, StatusTracker};
use std::process::Command;
use tracing::debug;

use super::{Collector, CollectorError};
use crate::config::NixOSConfig;

/// NixOS system information collector
/// 
/// Collects NixOS-specific system information including:
/// - NixOS version and build information
/// - Currently active/logged in users
pub struct NixOSCollector {
    config: NixOSConfig,
}

impl NixOSCollector {
    pub fn new(config: NixOSConfig) -> Self {
        Self { config }
    }

    /// Get NixOS build information (short hash and timestamp)
    fn get_nixos_build_info(&self) -> Result<(String, String), Box<dyn std::error::Error>> {
        // Try nixos-version command first
        if let Ok(output) = Command::new("nixos-version").output() {
            if output.status.success() {
                let version_line = String::from_utf8_lossy(&output.stdout);
                let version = version_line.trim();
                
                // Parse format: "24.05.20241023.abcdef (Vicuna)"
                if let Some(parts) = version.split('.').collect::<Vec<&str>>().get(2) {
                    if parts.len() >= 14 { // 8 digits + 6 hex chars minimum
                        let date_part = &parts[..8]; // YYYYMMDD
                        let hash_part = &parts[8..]; // remaining is hash
                        
                        // Extract short hash (first 6 characters)
                        let short_hash = if hash_part.len() >= 6 {
                            &hash_part[..6]
                        } else {
                            hash_part
                        };
                        
                        // Format date from YYYYMMDD to dd/mm/yy
                        if date_part.len() == 8 {
                            let year = &date_part[2..4]; // YY
                            let month = &date_part[4..6]; // MM  
                            let day = &date_part[6..8]; // DD
                            let formatted_date = format!("{}/{}/{}", day, month, year);
                            
                            return Ok((short_hash.to_string(), formatted_date));
                        }
                    }
                }
            }
        }

        Err("Could not parse NixOS build information".into())
    }

    /// Get currently active users
    fn get_active_users(&self) -> Result<Vec<String>, Box<dyn std::error::Error>> {
        let output = Command::new("who").output()?;
        
        if !output.status.success() {
            return Err("who command failed".into());
        }

        let who_output = String::from_utf8_lossy(&output.stdout);
        let mut users = std::collections::HashSet::new();

        for line in who_output.lines() {
            if let Some(username) = line.split_whitespace().next() {
                if !username.is_empty() {
                    users.insert(username.to_string());
                }
            }
        }

        Ok(users.into_iter().collect())
    }
}

#[async_trait]
impl Collector for NixOSCollector {
    fn name(&self) -> &str {
        "nixos"
    }

    async fn collect(&self, _status_tracker: &mut StatusTracker) -> Result<Vec<Metric>, CollectorError> {
        debug!("Collecting NixOS system information");
        let mut metrics = Vec::new();
        let timestamp = chrono::Utc::now().timestamp() as u64;

        // Collect NixOS build information
        match self.get_nixos_build_info() {
            Ok((short_hash, formatted_date)) => {
                // Create combined build string: "hash dd/mm/yy H:M:S"
                // For now, use current time for H:M:S (could be enhanced to get actual build time)
                let now = chrono::Local::now();
                let build_string = format!("{} {} {}",
                    short_hash,
                    formatted_date,
                    now.format("%H:%M:%S")
                );
                
                metrics.push(Metric {
                    name: "system_nixos_build".to_string(),
                    value: MetricValue::String(build_string),
                    unit: None,
                    description: Some("NixOS build information".to_string()),
                    status: Status::Ok,
                    timestamp,
                });
            }
            Err(e) => {
                debug!("Failed to get NixOS build info: {}", e);
                metrics.push(Metric {
                    name: "system_nixos_build".to_string(),
                    value: MetricValue::String("unknown".to_string()),
                    unit: None,
                    description: Some("NixOS build (failed to detect)".to_string()),
                    status: Status::Unknown,
                    timestamp,
                });
            }
        }

        // Collect active users
        match self.get_active_users() {
            Ok(users) => {
                let users_str = users.join(", ");
                metrics.push(Metric {
                    name: "system_active_users".to_string(),
                    value: MetricValue::String(users_str),
                    unit: None,
                    description: Some("Currently active users".to_string()),
                    status: Status::Ok,
                    timestamp,
                });
            }
            Err(e) => {
                debug!("Failed to get active users: {}", e);
                metrics.push(Metric {
                    name: "system_active_users".to_string(),
                    value: MetricValue::String("unknown".to_string()),
                    unit: None,
                    description: Some("Active users (failed to detect)".to_string()),
                    status: Status::Unknown,
                    timestamp,
                });
            }
        }

        debug!("Collected {} NixOS metrics", metrics.len());
        Ok(metrics)
    }
}