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
pub struct NixOSCollector {
}

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


    /// Get agent hash from binary path
    fn get_agent_hash(&self) -> Result<String, Box<dyn std::error::Error>> {
        // Get the path of the current executable
        let exe_path = std::env::current_exe()?;
        let exe_str = exe_path.to_string_lossy();
        
        // Extract Nix store hash from path like /nix/store/fn804fh332mp8gz06qawminpj20xl25h-cm-dashboard-0.1.0/bin/cm-dashboard-agent
        if let Some(store_path) = exe_str.strip_prefix("/nix/store/") {
            if let Some(dash_pos) = store_path.find('-') {
                return Ok(store_path[..dash_pos].to_string());
            }
        }
        
        // Fallback to "unknown" if not in Nix store
        Ok("unknown".to_string())
    }

    /// Get configuration hash from deployed nix store system
    /// Get git commit hash from rebuild process
    fn get_git_commit(&self) -> Result<String, Box<dyn std::error::Error>> {
        let commit_file = "/var/lib/cm-dashboard/git-commit";
        match std::fs::read_to_string(commit_file) {
            Ok(content) => {
                let commit_hash = content.trim();
                if commit_hash.len() >= 7 {
                    Ok(commit_hash.to_string())
                } else {
                    Err("Git commit hash too short".into())
                }
            }
            Err(e) => Err(format!("Failed to read git commit file: {}", e).into())
        }
    }

    fn get_config_hash(&self) -> Result<String, Box<dyn std::error::Error>> {
        // Read the symlink target of /run/current-system to get nix store path
        let output = Command::new("readlink")
            .arg("/run/current-system")
            .output()?;
        
        if !output.status.success() {
            return Err("readlink command failed".into());
        }
        
        let binding = String::from_utf8_lossy(&output.stdout);
        let store_path = binding.trim();
        
        // Extract hash from nix store path
        // Format: /nix/store/HASH-nixos-system-HOSTNAME-VERSION
        if let Some(hash_part) = store_path.strip_prefix("/nix/store/") {
            if let Some(hash) = hash_part.split('-').next() {
                if hash.len() >= 8 {
                    // Return first 8 characters of nix store hash
                    return Ok(hash[..8].to_string());
                }
            }
        }
        
        Err("Could not extract hash from nix store path".into())
    }

}

#[async_trait]
impl Collector for NixOSCollector {

    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 git commit information (shows what's actually deployed)
        match self.get_git_commit() {
            Ok(git_commit) => {
                metrics.push(Metric {
                    name: "system_nixos_build".to_string(),
                    value: MetricValue::String(git_commit),
                    unit: None,
                    description: Some("Git commit hash of deployed configuration".to_string()),
                    status: Status::Ok,
                    timestamp,
                });
            }
            Err(e) => {
                debug!("Failed to get git commit: {}", e);
                metrics.push(Metric {
                    name: "system_nixos_build".to_string(),
                    value: MetricValue::String("unknown".to_string()),
                    unit: None,
                    description: Some("Git commit hash (failed to detect)".to_string()),
                    status: Status::Unknown,
                    timestamp,
                });
            }
        }


        // Collect config hash
        match self.get_config_hash() {
            Ok(hash) => {
                metrics.push(Metric {
                    name: "system_config_hash".to_string(),
                    value: MetricValue::String(hash),
                    unit: None,
                    description: Some("NixOS deployed configuration hash".to_string()),
                    status: Status::Ok,
                    timestamp,
                });
            }
            Err(e) => {
                debug!("Failed to get config hash: {}", e);
                metrics.push(Metric {
                    name: "system_config_hash".to_string(),
                    value: MetricValue::String("unknown".to_string()),
                    unit: None,
                    description: Some("Deployed config hash (failed to detect)".to_string()),
                    status: Status::Unknown,
                    timestamp,
                });
            }
        }

        // Collect agent hash
        match self.get_agent_hash() {
            Ok(hash) => {
                metrics.push(Metric {
                    name: "system_agent_hash".to_string(),
                    value: MetricValue::String(hash),
                    unit: None,
                    description: Some("Agent Nix store hash".to_string()),
                    status: Status::Ok,
                    timestamp,
                });
            }
            Err(e) => {
                debug!("Failed to get agent hash: {}", e);
                metrics.push(Metric {
                    name: "system_agent_hash".to_string(),
                    value: MetricValue::String("unknown".to_string()),
                    unit: None,
                    description: Some("Agent hash (failed to detect)".to_string()),
                    status: Status::Unknown,
                    timestamp,
                });
            }
        }

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