use thiserror::Error;
use std::collections::HashMap;
use tracing::{debug, info, warn};

#[derive(Debug, Error)]
pub enum NftError {
    #[error("nft command failed: {0}")]
    CommandFailed(String),
    #[error("IO error: {0}")]
    Io(#[from] std::io::Error),
    #[error("Not running as root")]
    NotRoot,
}

/// Manager for nftables rules.
///
/// Executes `nft` CLI commands to manage kernel-level packet forwarding.
/// Requires root privileges; operations are skipped gracefully if not root.
pub struct NftManager {
    table_name: String,
    /// Active rules indexed by route ID
    active_rules: HashMap<String, Vec<String>>,
    /// Whether the table has been initialized
    table_initialized: bool,
}

impl NftManager {
    pub fn new(table_name: Option<String>) -> Self {
        Self {
            table_name: table_name.unwrap_or_else(|| "rustproxy".to_string()),
            active_rules: HashMap::new(),
            table_initialized: false,
        }
    }

    /// Check if we are running as root.
    fn is_root() -> bool {
        unsafe { libc::geteuid() == 0 }
    }

    /// Execute a single nft command via the CLI.
    async fn exec_nft(command: &str) -> Result<String, NftError> {
        // The command starts with "nft ", strip it to get the args
        let args = if command.starts_with("nft ") {
            &command[4..]
        } else {
            command
        };

        let output = tokio::process::Command::new("nft")
            .args(args.split_whitespace())
            .output()
            .await
            .map_err(NftError::Io)?;

        if output.status.success() {
            Ok(String::from_utf8_lossy(&output.stdout).to_string())
        } else {
            let stderr = String::from_utf8_lossy(&output.stderr);
            Err(NftError::CommandFailed(format!(
                "Command '{}' failed: {}",
                command, stderr
            )))
        }
    }

    /// Ensure the nftables table and chains are set up.
    async fn ensure_table(&mut self) -> Result<(), NftError> {
        if self.table_initialized {
            return Ok(());
        }

        let setup_commands = crate::rule_builder::build_table_setup(&self.table_name);
        for cmd in &setup_commands {
            Self::exec_nft(cmd).await?;
        }

        self.table_initialized = true;
        info!("NFTables table '{}' initialized", self.table_name);
        Ok(())
    }

    /// Apply rules for a route.
    ///
    /// Executes the nft commands via the CLI. If not running as root,
    /// the rules are stored locally but not applied to the kernel.
    pub async fn apply_rules(&mut self, route_id: &str, rules: Vec<String>) -> Result<(), NftError> {
        if !Self::is_root() {
            warn!("Not running as root, nftables rules will not be applied to kernel");
            self.active_rules.insert(route_id.to_string(), rules);
            return Ok(());
        }

        self.ensure_table().await?;

        for cmd in &rules {
            Self::exec_nft(cmd).await?;
            debug!("Applied nft rule: {}", cmd);
        }

        info!("Applied {} nftables rules for route '{}'", rules.len(), route_id);
        self.active_rules.insert(route_id.to_string(), rules);
        Ok(())
    }

    /// Remove rules for a route.
    ///
    /// Currently removes the route from tracking. To fully remove specific
    /// rules would require handle-based tracking; for now, cleanup() removes
    /// the entire table.
    pub async fn remove_rules(&mut self, route_id: &str) -> Result<(), NftError> {
        if let Some(rules) = self.active_rules.remove(route_id) {
            info!("Removed {} tracked nft rules for route '{}'", rules.len(), route_id);
        }
        Ok(())
    }

    /// Clean up all managed rules by deleting the entire nftables table.
    pub async fn cleanup(&mut self) -> Result<(), NftError> {
        if !Self::is_root() {
            warn!("Not running as root, skipping nftables cleanup");
            self.active_rules.clear();
            self.table_initialized = false;
            return Ok(());
        }

        if self.table_initialized {
            let cleanup_commands = crate::rule_builder::build_table_cleanup(&self.table_name);
            for cmd in &cleanup_commands {
                match Self::exec_nft(cmd).await {
                    Ok(_) => debug!("Cleanup: {}", cmd),
                    Err(e) => warn!("Cleanup command failed (may be ok): {}", e),
                }
            }
            info!("NFTables table '{}' cleaned up", self.table_name);
        }

        self.active_rules.clear();
        self.table_initialized = false;
        Ok(())
    }

    /// Get the table name.
    pub fn table_name(&self) -> &str {
        &self.table_name
    }

    /// Whether the table has been initialized in the kernel.
    pub fn is_initialized(&self) -> bool {
        self.table_initialized
    }

    /// Get the number of active route rule sets.
    pub fn active_route_count(&self) -> usize {
        self.active_rules.len()
    }

    /// Get the status of all active rules.
    pub fn status(&self) -> HashMap<String, serde_json::Value> {
        let mut status = HashMap::new();
        for (route_id, rules) in &self.active_rules {
            status.insert(
                route_id.clone(),
                serde_json::json!({
                    "ruleCount": rules.len(),
                    "rules": rules,
                }),
            );
        }
        status
    }
}

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

    #[test]
    fn test_new_default_table_name() {
        let mgr = NftManager::new(None);
        assert_eq!(mgr.table_name(), "rustproxy");
        assert!(!mgr.is_initialized());
    }

    #[test]
    fn test_new_custom_table_name() {
        let mgr = NftManager::new(Some("custom".to_string()));
        assert_eq!(mgr.table_name(), "custom");
    }

    #[tokio::test]
    async fn test_apply_rules_non_root() {
        let mut mgr = NftManager::new(None);
        // When not root, rules are stored but not applied to kernel
        let rules = vec!["nft add rule ip rustproxy prerouting tcp dport 443 dnat to 10.0.0.1:8443".to_string()];
        mgr.apply_rules("route-1", rules).await.unwrap();
        assert_eq!(mgr.active_route_count(), 1);

        let status = mgr.status();
        assert!(status.contains_key("route-1"));
        assert_eq!(status["route-1"]["ruleCount"], 1);
    }

    #[tokio::test]
    async fn test_remove_rules() {
        let mut mgr = NftManager::new(None);
        let rules = vec!["nft add rule test".to_string()];
        mgr.apply_rules("route-1", rules).await.unwrap();
        assert_eq!(mgr.active_route_count(), 1);

        mgr.remove_rules("route-1").await.unwrap();
        assert_eq!(mgr.active_route_count(), 0);
    }

    #[tokio::test]
    async fn test_cleanup_non_root() {
        let mut mgr = NftManager::new(None);
        let rules = vec!["nft add rule test".to_string()];
        mgr.apply_rules("route-1", rules).await.unwrap();
        mgr.apply_rules("route-2", vec!["nft add rule test2".to_string()]).await.unwrap();

        mgr.cleanup().await.unwrap();
        assert_eq!(mgr.active_route_count(), 0);
        assert!(!mgr.is_initialized());
    }

    #[tokio::test]
    async fn test_status_multiple_routes() {
        let mut mgr = NftManager::new(None);
        mgr.apply_rules("web", vec!["rule1".to_string(), "rule2".to_string()]).await.unwrap();
        mgr.apply_rules("api", vec!["rule3".to_string()]).await.unwrap();

        let status = mgr.status();
        assert_eq!(status.len(), 2);
        assert_eq!(status["web"]["ruleCount"], 2);
        assert_eq!(status["api"]["ruleCount"], 1);
    }
}