use anyhow::Result;
use tracing::{Instrument, debug, info, instrument, warn};

use crate::config::AgentConfig;
use crate::protocol::{
    AgentCommand, CommandResult, DevsRequest, InventoryRequest, LeasesRequest, WakeRequest,
};

#[instrument(skip_all)]
pub async fn dispatch_command(
    command: AgentCommand,
    config: &AgentConfig,
) -> Result<CommandResult> {
    let kind = command_kind(&command);
    info!(command = %kind, "dispatching command into local wakey services");
    match command {
        AgentCommand::Leases(req) => dispatch_leases(req, config).await,
        AgentCommand::Devs(req) => dispatch_devs(req).await,
        AgentCommand::Inventory(req) => dispatch_inventory(req, config).await,
        AgentCommand::Wake(req) => dispatch_wake(req).await,
    }
}

async fn dispatch_leases(req: LeasesRequest, config: &AgentConfig) -> Result<CommandResult> {
    let leases = wakey::wakey_linux::dhcp::read_dhcp_leases_with_names_from_paths(
        &config.dhcp_leases_path,
        &config.observation_store_path,
        &config.mac_name_cache_path,
    )
    .await?;
    let leases = if req.include_state {
        // only runs when requested explicitly to the endpoint
        #[allow(deprecated)]
        wakey::wakey_linux::dhcp::enrich_leases_with_nud_state(leases).await
    } else {
        wakey::leases_without_state(leases)
    };
    debug!(
        rows = leases.len(),
        include_state = req.include_state,
        "dispatched leases command"
    );
    Ok(CommandResult::Leases { rows: leases })
}

async fn dispatch_devs(req: DevsRequest) -> Result<CommandResult> {
    let mut devs = if let Some(name) = &req.dev {
        wakey::get_interface_summary(name)
            .await?
            .into_iter()
            .collect()
    } else {
        wakey::get_interface_summaries().await?
    };
    if req.up_only {
        devs.retain(|dev| dev.operstate == "up");
    }
    debug!(
        rows = devs.len(),
        up_only = req.up_only,
        "dispatched devs command"
    );
    Ok(CommandResult::Devs { rows: devs })
}

async fn dispatch_inventory(req: InventoryRequest, config: &AgentConfig) -> Result<CommandResult> {
    Ok(CommandResult::Inventory(
        inventory_for_config(req, config).await?,
    ))
}

#[instrument(name = "agent_inventory", skip_all, fields(neighbors = tracing::field::Empty, leases = tracing::field::Empty, observations = tracing::field::Empty, devices = tracing::field::Empty))]
pub async fn inventory_for_config(
    req: InventoryRequest,
    config: &AgentConfig,
) -> Result<wakey_core::DeviceInventory> {
    let query = req.into_inventory_query();
    // This configured path serves both commands and periodic snapshots; keep
    // phase spans here so neither caller bypasses source timing.
    let neighbors = wakey::wakey_linux::devices::query_neighbors(&query)
        .instrument(tracing::info_span!("inventory_neighbors"))
        .await?;
    tracing::Span::current().record("neighbors", neighbors.len());
    let leases = wakey::wakey_linux::dhcp::read_dhcp_leases_with_names_from_paths(
        &config.dhcp_leases_path,
        &config.observation_store_path,
        &config.mac_name_cache_path,
    )
    .instrument(tracing::info_span!("inventory_dhcp_leases"))
    .await?;
    tracing::Span::current().record("leases", leases.len());
    match wakey::wakey_linux::observations::prune_stale_observations_from_path(
        &config.observation_store_path,
        config.observation_retention_days,
    )
    .instrument(tracing::info_span!("inventory_observation_prune"))
    .await
    {
        Ok(removed) if removed > 0 => {
            debug!(removed, "pruned stale local hook observations");
        }
        Ok(_) => {}
        Err(err) => {
            warn!(error = %err, "failed pruning stale local hook observations");
        }
    }
    let observations = match wakey::wakey_linux::observations::list_local_observations_from_path(
        &config.observation_store_path,
    )
    .instrument(tracing::info_span!("inventory_hook_store"))
    .await
    {
        Ok(observations) => observations
            .into_iter()
            .filter_map(wakey::local_observation_to_fact)
            .collect::<Vec<_>>(),
        Err(err) => {
            warn!(error = %err, "failed reading local hook observations for inventory command");
            Vec::new()
        }
    };
    tracing::Span::current().record("observations", observations.len());
    debug!(
        neighbors = neighbors.len(),
        leases = leases.len(),
        observations = observations.len(),
        "dispatching inventory with merged sources"
    );
    let inventory = wakey_core::DeviceInventory {
        devices: wakey::merge_devices_with_observations(
            neighbors,
            wakey::leases_without_state(leases),
            observations,
            &query,
        ),
    };
    tracing::Span::current().record("devices", inventory.devices.len());
    debug!(
        rows = inventory.devices.len(),
        "dispatched inventory command"
    );
    Ok(inventory)
}

async fn dispatch_wake(req: WakeRequest) -> Result<CommandResult> {
    validate_wake_request(&req)?;
    let result = match (req.query, req.mac, req.ip) {
        (Some(query), None, None) => wakey::wake_from_query(query).await?,
        (None, Some(mac), ip) => wakey::wake_explicit(mac, ip).await?,
        _ => unreachable!("wake request validated before dispatch"),
    };
    debug!("dispatched wake command");
    Ok(CommandResult::Wake(result))
}

fn command_kind(command: &AgentCommand) -> &'static str {
    match command {
        AgentCommand::Leases(_) => "leases",
        AgentCommand::Devs(_) => "devs",
        AgentCommand::Inventory(_) => "inventory",
        AgentCommand::Wake(_) => "wake",
    }
}

pub fn validate_wake_request(req: &WakeRequest) -> Result<()> {
    let has_query = req.query.is_some();
    let has_mac = req.mac.is_some();
    let has_ip = req.ip.is_some();

    if has_ip && !has_mac {
        anyhow::bail!("wake request `ip` requires `mac`");
    }
    if has_query && (has_mac || has_ip) {
        anyhow::bail!("wake query mode and explicit mode are mutually exclusive");
    }
    if !has_query && !has_mac {
        anyhow::bail!("wake request requires either `query` or `mac`");
    }
    Ok(())
}

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

    #[test]
    fn wake_rejects_ip_without_mac() {
        let err = validate_wake_request(&WakeRequest {
            query: None,
            mac: None,
            ip: Some("192.168.1.1".parse().expect("ip")),
        })
        .expect_err("should reject");
        assert!(err.to_string().contains("requires `mac`"));
    }

    #[test]
    fn wake_rejects_mixed_mode() {
        let err = validate_wake_request(&WakeRequest {
            query: Some("pc".into()),
            mac: Some("aa:bb:cc:dd:ee:ff".parse().expect("mac")),
            ip: None,
        })
        .expect_err("should reject");
        assert!(err.to_string().contains("mutually exclusive"));
    }
}