//! Mesh networking: local node discovery over LoRa (Meshtastic) and BLE.
//!
//! Broadcasts node identity over mesh radio networks for offline peer discovery.
//! Uses Meshtastic serial protocol when a compatible radio is connected via USB.

use anyhow::{Context, Result};
use serde::{Deserialize, Serialize};
use std::path::Path;
use tokio::fs;

const MESH_CONFIG_FILE: &str = "mesh-config.json";

/// A node discovered via mesh radio.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct MeshNode {
    pub node_id: String,
    pub did: Option<String>,
    pub pubkey: Option<String>,
    pub rssi: Option<i32>,
    pub snr: Option<f64>,
    pub last_heard: String,
    #[serde(default)]
    pub hops: u32,
    #[serde(default)]
    pub channel: Option<String>,
}

/// Mesh configuration.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct MeshConfig {
    pub enabled: bool,
    #[serde(default)]
    pub device_path: Option<String>,
    #[serde(default)]
    pub channel_name: Option<String>,
    #[serde(default)]
    pub broadcast_identity: bool,
}

impl Default for MeshConfig {
    fn default() -> Self {
        Self {
            enabled: false,
            device_path: None,
            channel_name: Some("archipelago".to_string()),
            broadcast_identity: true,
        }
    }
}

pub async fn load_config(data_dir: &Path) -> Result<MeshConfig> {
    let path = data_dir.join(MESH_CONFIG_FILE);
    if !path.exists() {
        return Ok(MeshConfig::default());
    }
    let content = fs::read_to_string(&path)
        .await
        .context("Failed to read mesh config")?;
    let config: MeshConfig = serde_json::from_str(&content).unwrap_or_default();
    Ok(config)
}

pub async fn save_config(data_dir: &Path, config: &MeshConfig) -> Result<()> {
    fs::create_dir_all(data_dir).await.context("Failed to create data dir")?;
    let content =
        serde_json::to_string_pretty(config).context("Failed to serialize mesh config")?;
    fs::write(data_dir.join(MESH_CONFIG_FILE), content)
        .await
        .context("Failed to write mesh config")?;
    Ok(())
}

/// Detect Meshtastic-compatible USB devices.
/// Meshtastic radios typically appear as USB serial devices (CP210x, CH340, FTDI).
pub async fn detect_meshtastic_devices() -> Vec<String> {
    let mut devices = Vec::new();

    // Check for common serial device paths
    let candidates = [
        "/dev/ttyUSB0",
        "/dev/ttyUSB1",
        "/dev/ttyACM0",
        "/dev/ttyACM1",
    ];

    for path in &candidates {
        if tokio::fs::metadata(path).await.is_ok() {
            devices.push(path.to_string());
        }
    }

    // Also scan sysfs for Meshtastic-specific USB VIDs
    if let Ok(mut entries) = tokio::fs::read_dir("/sys/bus/usb/devices").await {
        while let Ok(Some(entry)) = entries.next_entry().await {
            let vid_path = entry.path().join("idVendor");
            if let Ok(vid_str) = tokio::fs::read_to_string(&vid_path).await {
                let vid = vid_str.trim();
                // Silicon Labs CP210x (common Meshtastic radio)
                // CH340 USB-serial
                // FTDI FT232
                if vid == "10c4" || vid == "1a86" || vid == "0403" {
                    let product = tokio::fs::read_to_string(entry.path().join("product"))
                        .await
                        .map(|s| s.trim().to_string())
                        .unwrap_or_else(|_| "Serial Device".to_string());
                    devices.push(format!("{} ({})", entry.path().display(), product));
                }
            }
        }
    }

    devices
}

/// Discover nodes via Meshtastic CLI (meshtastic --nodes).
/// Returns nodes that have broadcast their Archipelago identity.
pub async fn discover_nodes(device_path: Option<&str>) -> Result<Vec<MeshNode>> {
    let mut cmd = tokio::process::Command::new("meshtastic");
    cmd.arg("--nodes");

    if let Some(dev) = device_path {
        cmd.arg("--port").arg(dev);
    }

    let output = cmd
        .output()
        .await
        .context("Failed to run meshtastic CLI — is it installed?")?;

    if !output.status.success() {
        let stderr = String::from_utf8_lossy(&output.stderr);
        if stderr.contains("No Meshtastic") || stderr.contains("not found") {
            return Ok(Vec::new());
        }
        anyhow::bail!("meshtastic --nodes failed: {}", stderr);
    }

    let stdout = String::from_utf8_lossy(&output.stdout);
    let mut nodes = Vec::new();

    // Parse the meshtastic CLI node list output
    // Format varies but typically: NodeNum | User | AKA | ...
    for line in stdout.lines().skip(2) {
        // Skip header lines
        let parts: Vec<&str> = line.split('|').map(|s| s.trim()).collect();
        if parts.len() < 3 {
            continue;
        }

        let node_id = parts.first().unwrap_or(&"").to_string();
        if node_id.is_empty() || node_id.starts_with('-') {
            continue;
        }

        nodes.push(MeshNode {
            node_id: node_id.trim().to_string(),
            did: None,
            pubkey: None,
            rssi: None,
            snr: None,
            last_heard: chrono::Utc::now().to_rfc3339(),
            hops: 0,
            channel: None,
        });
    }

    Ok(nodes)
}

/// Broadcast our node identity over mesh.
pub async fn broadcast_identity(
    did: &str,
    pubkey: &str,
    device_path: Option<&str>,
) -> Result<()> {
    let message = format!("ARCHY:{}:{}", did, pubkey);

    let mut cmd = tokio::process::Command::new("meshtastic");
    cmd.arg("--sendtext").arg(&message);

    if let Some(dev) = device_path {
        cmd.arg("--port").arg(dev);
    }

    let output = cmd
        .output()
        .await
        .context("Failed to broadcast via meshtastic")?;

    if !output.status.success() {
        anyhow::bail!(
            "meshtastic broadcast failed: {}",
            String::from_utf8_lossy(&output.stderr)
        );
    }

    Ok(())
}

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

    #[test]
    fn test_mesh_config_default() {
        let config = MeshConfig::default();
        assert!(!config.enabled);
        assert_eq!(config.channel_name, Some("archipelago".to_string()));
        assert!(config.broadcast_identity);
    }

    #[test]
    fn test_mesh_config_serialization() {
        let config = MeshConfig {
            enabled: true,
            device_path: Some("/dev/ttyUSB0".to_string()),
            channel_name: Some("test".to_string()),
            broadcast_identity: false,
        };
        let json = serde_json::to_string(&config).unwrap();
        let parsed: MeshConfig = serde_json::from_str(&json).unwrap();
        assert!(parsed.enabled);
        assert_eq!(parsed.device_path, Some("/dev/ttyUSB0".to_string()));
    }

    #[test]
    fn test_mesh_node_serialization() {
        let node = MeshNode {
            node_id: "!aabbccdd".to_string(),
            did: Some("did:key:z123".to_string()),
            pubkey: Some("pubhex".to_string()),
            rssi: Some(-85),
            snr: Some(7.5),
            last_heard: "2026-03-10T00:00:00Z".to_string(),
            hops: 1,
            channel: Some("archipelago".to_string()),
        };
        let json = serde_json::to_string(&node).unwrap();
        let parsed: MeshNode = serde_json::from_str(&json).unwrap();
        assert_eq!(parsed.node_id, "!aabbccdd");
        assert_eq!(parsed.rssi, Some(-85));
    }

    #[tokio::test]
    async fn test_load_config_default_when_no_file() {
        let dir = tempfile::tempdir().unwrap();
        let config = load_config(dir.path()).await.unwrap();
        assert!(!config.enabled);
    }

    #[tokio::test]
    async fn test_save_and_load_config_roundtrip() {
        let dir = tempfile::tempdir().unwrap();
        let config = MeshConfig {
            enabled: true,
            device_path: Some("/dev/ttyUSB0".to_string()),
            channel_name: Some("archy".to_string()),
            broadcast_identity: true,
        };
        save_config(dir.path(), &config).await.unwrap();
        let loaded = load_config(dir.path()).await.unwrap();
        assert!(loaded.enabled);
        assert_eq!(loaded.device_path, Some("/dev/ttyUSB0".to_string()));
    }
}