//! The Bluetooth link to the ELM327 (the OBD-II adapter on the K-line), as BlueZ sees
//! it. Only watched, never opened: the adapter takes one connection, and obd-poller
//! holds it while the ECU answers.

use std::process::Command;

use serde_json::{json, Value};

pub struct Elm {
    /// "00:0C:BF:50:AF:3F"; None when no adapter is configured.
    addr: Option<String>,
}

/// `bluetoothctl info` says "Connected: yes" while any link to the device is up,
/// the poller's serial link included. An unknown device is simply not connected.
fn connected(addr: &str) -> bool {
    Command::new("bluetoothctl")
        .args(["info", addr])
        .output()
        .map(|o| String::from_utf8_lossy(&o.stdout).lines().any(|l| l.trim() == "Connected: yes"))
        .unwrap_or(false)
}

impl Elm {
    pub fn new(addr: &str) -> Self {
        Elm { addr: Some(addr.trim().to_string()).filter(|a| !a.is_empty()) }
    }

    pub fn read(&mut self, out: &mut Vec<(&'static str, Value)>) {
        if let Some(a) = &self.addr {
            out.push(("elm_connected", json!(connected(a))));
        }
    }
}