// WIP mesh/transport protocol — suppress dead code warnings
#![allow(dead_code)]
//! Async serial driver for Meshcore devices.
//!
//! Handles opening the serial port, reading/writing frames,
//! and the initialization handshake sequence.

use super::protocol::{self, InboundFrame};
use super::types::DeviceInfo;
use anyhow::{Context, Result};
use std::path::Path;
use std::time::Duration;
use tracing::{debug, info, warn};

/// Serial port configuration for Meshcore Companion USB.
const BAUD_RATE: u32 = 115200;

/// Timeout for reading a response frame from the device.
const READ_TIMEOUT: Duration = Duration::from_secs(5);

/// Timeout for writing a frame to the device.
const WRITE_TIMEOUT: Duration = Duration::from_secs(2);

/// Buffer size for serial reads.
const READ_BUF_SIZE: usize = 512;

/// Application name sent during handshake.
const APP_NAME: &str = "Archipelago";

/// Async Meshcore device handle.
pub struct MeshcoreDevice {
    port: serial2_tokio::SerialPort,
    read_buf: Vec<u8>,
    pub node_id: Option<u32>,
    pub advert_name: Option<String>,
    pub device_info: Option<DeviceInfo>,
    device_path: String,
}

impl MeshcoreDevice {
    /// Open a serial port and verify it's a Meshcore device.
    pub async fn open(path: &str) -> Result<Self> {
        // Check device exists before trying to open (better error message)
        match tokio::fs::metadata(path).await {
            Ok(meta) => {
                debug!(path = %path, permissions = ?meta.permissions(), "Device node exists");
            }
            Err(e) => {
                anyhow::bail!(
                    "Serial device {} not accessible: {} (check PrivateDevices in systemd, or USB connection)",
                    path, e
                );
            }
        }

        let port = serial2_tokio::SerialPort::open(path, BAUD_RATE).context(format!(
            "Failed to open serial port {} (permission denied? device busy?)",
            path
        ))?;

        info!(path = %path, baud = BAUD_RATE, "Opened serial port");

        Ok(Self {
            port,
            read_buf: Vec::with_capacity(READ_BUF_SIZE),
            node_id: None,
            advert_name: None,
            device_info: None,
            device_path: path.to_string(),
        })
    }

    /// Run the Meshcore initialization handshake.
    /// Matches the official meshcore_py library sequence:
    /// 1. CMD_APP_START -> RESP_SELF_INFO (this is the first command, not device_query)
    /// 2. CMD_SET_DEVICE_TIME (sync clock)
    pub async fn initialize(&mut self) -> Result<DeviceInfo> {
        info!("Starting Meshcore handshake on {}", self.device_path);

        // Step 1: App start (the official library sends this first)
        self.send_raw(&protocol::build_app_start(APP_NAME)).await?;

        let frame = self
            .recv_frame_timeout(READ_TIMEOUT)
            .await
            .context("No response to APP_START — is this a Meshcore Companion USB device?")?;

        info!(
            code = frame.code,
            data_len = frame.data.len(),
            "Got response to APP_START"
        );

        if frame.code == protocol::RESP_ERR {
            anyhow::bail!("App start failed: {}", protocol::parse_error(&frame.data));
        }

        // The response could be SELF_INFO or something else depending on firmware version
        let (node_id, name) = if frame.code == protocol::RESP_SELF_INFO {
            protocol::parse_self_info(&frame.data).context("Failed to parse self info")?
        } else {
            // Try to parse whatever we got
            info!(
                code = frame.code,
                "Unexpected response code, trying to parse as self info"
            );
            protocol::parse_self_info(&frame.data).unwrap_or((0, String::new()))
        };

        info!(node_id, name = %name, "Meshcore identity");

        self.node_id = Some(node_id);
        self.advert_name = Some(name.clone());

        // Step 2: Sync device clock
        let now = std::time::SystemTime::now()
            .duration_since(std::time::UNIX_EPOCH)
            .unwrap_or_default()
            .as_secs();
        self.send_raw(&protocol::build_set_device_time(now)).await?;
        // Time set response is best-effort — don't fail if it times out
        match self.recv_frame_timeout(Duration::from_secs(2)).await {
            Ok(frame) if frame.code == protocol::RESP_OK => {
                debug!("Device clock synced");
            }
            Ok(frame) => {
                warn!(code = frame.code, "Unexpected response to SET_DEVICE_TIME");
            }
            Err(_) => {
                warn!("No response to SET_DEVICE_TIME (continuing anyway)");
            }
        }

        let info = DeviceInfo {
            firmware_version: name.clone(),
            node_id,
            max_contacts: 100,
            device_type: super::types::DeviceType::Meshcore,
        };
        self.device_info = Some(info.clone());

        info!("Meshcore initialization complete on {}", self.device_path);
        Ok(info)
    }

    /// Set the advertised name on the mesh network.
    pub async fn set_advert_name(&mut self, name: &str) -> Result<()> {
        self.send_raw(&protocol::build_set_advert_name(name))
            .await?;
        let frame = self.recv_frame_timeout(READ_TIMEOUT).await?;
        if frame.code == protocol::RESP_ERR {
            anyhow::bail!(
                "Set advert name failed: {}",
                protocol::parse_error(&frame.data)
            );
        }
        self.advert_name = Some(name.to_string());
        Ok(())
    }

    /// Broadcast our advertisement to the mesh.
    pub async fn send_self_advert(&mut self) -> Result<()> {
        self.send_raw(&protocol::build_send_self_advert()).await?;
        // Response is RESP_OK or RESP_SENT
        let frame = self.recv_frame_timeout(READ_TIMEOUT).await?;
        if frame.code == protocol::RESP_ERR {
            anyhow::bail!("Self advert failed: {}", protocol::parse_error(&frame.data));
        }
        Ok(())
    }

    /// Send a text message to a contact by their public key prefix (first 6 bytes).
    /// Returns whether the firmware routed it via flood (true) or direct (false).
    /// The response frame is `RESP_CODE_SENT | mode | tag[4] | est_timeout[4]`
    /// where mode == 1 means flood and mode == 0 means direct.
    pub async fn send_text(&mut self, dest_pubkey_prefix: &[u8; 6], msg: &[u8]) -> Result<bool> {
        let frame_data = protocol::build_send_text(dest_pubkey_prefix, msg)?;
        self.send_raw(&frame_data).await?;
        let frame = self.recv_frame_timeout(READ_TIMEOUT).await?;
        if frame.code == protocol::RESP_ERR {
            anyhow::bail!("Send text failed: {}", protocol::parse_error(&frame.data));
        }
        // RESP_CODE_SENT layout: [mode(1)][tag(4)][est_timeout(4)]
        let sent_via_flood = frame.data.first().copied().unwrap_or(0) == 1;
        tracing::info!(
            dest = %hex::encode(dest_pubkey_prefix),
            mode = if sent_via_flood { "flood" } else { "direct" },
            resp_code = frame.code,
            data_len = frame.data.len(),
            "[diag] send_text response"
        );
        Ok(sent_via_flood)
    }

    /// Broadcast a text message on a channel.
    pub async fn send_channel_text(&mut self, channel: u8, msg: &[u8]) -> Result<()> {
        let frame_data = protocol::build_send_channel_text(channel, msg)?;
        self.send_raw(&frame_data).await?;
        let frame = self.recv_frame_timeout(READ_TIMEOUT).await?;
        if frame.code == protocol::RESP_ERR {
            anyhow::bail!(
                "Channel broadcast failed: {}",
                protocol::parse_error(&frame.data)
            );
        }
        Ok(())
    }

    /// Send a NATIVE meshcore direct message (CMD_SEND_TXT_MSG) to a contact,
    /// addressed by the first 6 bytes of its public key. Unlike the
    /// `@DM2`-over-channel path, this is a real unicast — it does not appear on
    /// the public channel, and a stock meshcore client receives it as a normal
    /// DM. The contact must already exist in the firmware table (with a path).
    pub async fn send_text_msg(&mut self, dest_pubkey_prefix: &[u8; 6], msg: &[u8]) -> Result<()> {
        let frame_data = protocol::build_send_text(dest_pubkey_prefix, msg)?;
        self.send_raw(&frame_data).await?;
        let frame = self.recv_frame_timeout(READ_TIMEOUT).await?;
        if frame.code == protocol::RESP_ERR {
            anyhow::bail!(
                "Direct text send failed: {}",
                protocol::parse_error(&frame.data)
            );
        }
        Ok(())
    }

    /// Clear the stored routing path for a contact so the firmware flood-
    /// routes future messages instead of dropping them when path_len=0.
    pub async fn reset_contact_path(&mut self, pubkey: &[u8; 32]) -> Result<()> {
        self.send_raw(&protocol::build_reset_path(pubkey)).await?;
        let frame = self.recv_frame_timeout(READ_TIMEOUT).await?;
        if frame.code == protocol::RESP_ERR {
            anyhow::bail!("Reset path failed: {}", protocol::parse_error(&frame.data));
        }
        Ok(())
    }

    /// Delete a contact from the firmware's persistent contact table.
    pub async fn remove_contact(&mut self, pubkey: &[u8; 32]) -> Result<()> {
        self.send_raw(&protocol::build_remove_contact(pubkey))
            .await?;
        let frame = self.recv_frame_timeout(READ_TIMEOUT).await?;
        if frame.code == protocol::RESP_ERR {
            anyhow::bail!(
                "Remove contact failed: {}",
                protocol::parse_error(&frame.data)
            );
        }
        Ok(())
    }

    /// Add/update a contact in the firmware table (CMD_ADD_UPDATE_CONTACT).
    /// Used to import a heard advert so it shows up as a contact immediately.
    pub async fn add_contact(
        &mut self,
        pubkey: &[u8; 32],
        contact_type: u8,
        flags: u8,
        out_path_len: u8,
        name: &str,
        last_advert: u32,
    ) -> Result<()> {
        self.send_raw(&protocol::build_add_contact(
            pubkey,
            contact_type,
            flags,
            out_path_len,
            name,
            last_advert,
        ))
        .await?;
        let frame = self.recv_frame_timeout(READ_TIMEOUT).await?;
        if frame.code == protocol::RESP_ERR {
            anyhow::bail!("Add contact failed: {}", protocol::parse_error(&frame.data));
        }
        Ok(())
    }

    /// Get the list of known contacts from the device.
    /// Protocol: CMD_GET_CONTACTS -> CONTACT_START(count) -> N×CONTACT -> CONTACT_END
    pub async fn get_contacts(&mut self) -> Result<Vec<protocol::ParsedContact>> {
        self.send_raw(&protocol::build_get_contacts()).await?;

        let mut contacts = Vec::new();
        loop {
            let frame = self.recv_frame_timeout(READ_TIMEOUT).await?;
            match frame.code {
                protocol::RESP_CONTACT_START => {
                    // Contains the count of contacts to follow
                    let count = if frame.data.len() >= 4 {
                        u32::from_le_bytes([
                            frame.data[0],
                            frame.data[1],
                            frame.data[2],
                            frame.data[3],
                        ])
                    } else {
                        0
                    };
                    debug!(count, "Contact list start");
                }
                protocol::RESP_CONTACT => match protocol::parse_contact(&frame.data) {
                    Ok(contact) => contacts.push(contact),
                    Err(e) => warn!("Failed to parse contact: {}", e),
                },
                protocol::RESP_CONTACT_END => {
                    debug!(count = contacts.len(), "Contact list complete");
                    break;
                }
                protocol::RESP_OK => break,
                protocol::RESP_ERR => {
                    anyhow::bail!(
                        "Get contacts failed: {}",
                        protocol::parse_error(&frame.data)
                    );
                }
                _ => {
                    debug!(code = frame.code, "Unexpected response during contact list");
                    // Don't break — might be a push notification interspersed
                }
            }
        }

        Ok(contacts)
    }

    /// Retrieve queued messages from the device.
    /// Returns raw frames (code + data) for the listener to parse.
    pub async fn sync_messages(&mut self) -> Result<Vec<protocol::InboundFrame>> {
        self.send_raw(&protocol::build_sync_next_message()).await?;

        let mut frames = Vec::new();
        loop {
            let frame = self.recv_frame_timeout(READ_TIMEOUT).await?;
            match frame.code {
                // All message types (v1 and v3)
                protocol::RESP_CONTACT_MSG
                | protocol::RESP_CONTACT_MSG_V3
                | protocol::RESP_CHANNEL_MSG
                | protocol::RESP_CHANNEL_MSG_V3 => {
                    frames.push(frame);
                    // Request next message
                    self.send_raw(&protocol::build_sync_next_message()).await?;
                }
                protocol::RESP_NO_MORE_MESSAGES => break,
                protocol::RESP_OK => break,
                protocol::RESP_ERR => {
                    anyhow::bail!(
                        "Sync messages failed: {}",
                        protocol::parse_error(&frame.data)
                    );
                }
                _ => {
                    // Push notifications can arrive during sync — skip them
                    if protocol::is_push_notification(frame.code) {
                        continue;
                    }
                    debug!(code = frame.code, "Unexpected response during message sync");
                    break;
                }
            }
        }

        Ok(frames)
    }

    /// Write raw bytes to the serial port.
    pub async fn send_raw(&mut self, data: &[u8]) -> Result<()> {
        tokio::time::timeout(WRITE_TIMEOUT, self.port.write_all(data))
            .await
            .context("Serial write timed out")?
            .context("Serial write failed")?;
        Ok(())
    }

    /// Try to read and parse one complete inbound frame.
    /// Returns the frame if one is available, or reads more data from serial.
    pub async fn try_recv_frame(&mut self) -> Result<Option<InboundFrame>> {
        // First check if we already have a complete frame in the buffer
        if let Some(frame) = protocol::decode_frame(&self.read_buf) {
            let consumed = frame.bytes_consumed;
            let result = frame;
            self.read_buf.drain(..consumed);
            return Ok(Some(result));
        }

        // Try to read more data (non-blocking via small timeout)
        let mut tmp = [0u8; READ_BUF_SIZE];
        match tokio::time::timeout(Duration::from_millis(50), self.port.read(&mut tmp)).await {
            Ok(Ok(n)) if n > 0 => {
                self.read_buf.extend_from_slice(&tmp[..n]);
            }
            _ => return Ok(None),
        }

        // Try parsing again with new data
        if let Some(frame) = protocol::decode_frame(&self.read_buf) {
            let consumed = frame.bytes_consumed;
            let result = frame;
            self.read_buf.drain(..consumed);
            return Ok(Some(result));
        }

        Ok(None)
    }

    /// Read one complete inbound frame with timeout.
    pub async fn recv_frame_timeout(&mut self, timeout: Duration) -> Result<InboundFrame> {
        let deadline = tokio::time::Instant::now() + timeout;

        loop {
            // Check buffer for a complete frame
            if let Some(frame) = protocol::decode_frame(&self.read_buf) {
                let consumed = frame.bytes_consumed;
                let result = frame;
                self.read_buf.drain(..consumed);
                return Ok(result);
            }

            // Read more data from serial
            let remaining = deadline.saturating_duration_since(tokio::time::Instant::now());
            if remaining.is_zero() {
                anyhow::bail!("Timeout waiting for serial frame");
            }

            let mut tmp = [0u8; READ_BUF_SIZE];
            match tokio::time::timeout(
                remaining.min(Duration::from_millis(100)),
                self.port.read(&mut tmp),
            )
            .await
            {
                Ok(Ok(0)) => anyhow::bail!("Serial port closed"),
                Ok(Ok(n)) => {
                    self.read_buf.extend_from_slice(&tmp[..n]);
                }
                Ok(Err(e)) => return Err(e).context("Serial read error"),
                Err(_) => continue, // timeout on this read, try again if deadline not reached
            }
        }
    }

    /// Get the device path this handle is connected to.
    pub fn path(&self) -> &str {
        &self.device_path
    }
}

// ─── Device detection ───────────────────────────────────────────────────

/// Candidate serial device paths to check on Linux.
/// /dev/mesh-radio is a stable udev symlink (see 99-mesh-radio.rules).
const SERIAL_CANDIDATES: &[&str] = &[
    "/dev/mesh-radio",
    "/dev/ttyUSB0",
    "/dev/ttyUSB1",
    "/dev/ttyUSB2",
    "/dev/ttyACM0",
    "/dev/ttyACM1",
    "/dev/ttyACM2",
];

const SKIP_SERIAL_MODEL_SUBSTRINGS: &[&str] = &["Sierra_Wireless", "Z-Wave", "Zooz"];

fn likely_non_mesh_serial_device(path: &str) -> bool {
    let Some(name) = Path::new(path).file_name().and_then(|s| s.to_str()) else {
        return false;
    };
    let by_id = Path::new("/dev/serial/by-id");
    let Ok(entries) = std::fs::read_dir(by_id) else {
        return false;
    };
    for entry in entries.flatten() {
        let file_name = entry.file_name().to_string_lossy().to_string();
        if !SKIP_SERIAL_MODEL_SUBSTRINGS
            .iter()
            .any(|needle| file_name.contains(needle))
        {
            continue;
        }
        if let Ok(target) = std::fs::read_link(entry.path()) {
            if target.file_name().and_then(|s| s.to_str()) == Some(name) {
                return true;
            }
        }
    }
    false
}

/// Scan for serial devices that could be Meshcore radios.
/// Returns paths to existing serial device files.
pub async fn detect_serial_devices() -> Vec<String> {
    let mut devices = Vec::new();
    for path in SERIAL_CANDIDATES {
        if tokio::fs::metadata(path).await.is_ok() {
            if likely_non_mesh_serial_device(path) {
                debug!(path = %path, "Skipping known non-mesh serial device");
                continue;
            }
            devices.push(path.to_string());
        }
    }
    devices
}

/// Try to open and handshake with each detected serial device.
/// Returns the first device that responds as Meshcore.
pub async fn probe_for_meshcore(paths: &[String]) -> Option<(String, DeviceInfo)> {
    for path in paths {
        debug!(path = %path, "Probing for Meshcore device");
        match MeshcoreDevice::open(path).await {
            Ok(mut device) => {
                match device.initialize().await {
                    Ok(info) => {
                        info!(path = %path, firmware = %info.firmware_version, "Found Meshcore device");
                        // Drop the device so the listener can open it
                        drop(device);
                        return Some((path.clone(), info));
                    }
                    Err(e) => {
                        debug!(path = %path, error = %e, "Not a Meshcore device");
                    }
                }
            }
            Err(e) => {
                debug!(path = %path, error = %e, "Could not open serial port");
            }
        }
    }
    None
}