use std::collections::HashMap;
use std::fs;
use std::io::Write;

#[derive(Debug)]
pub struct ThermalDevice {
    pub name: String,
    pub celsius: i32,
}

pub fn read_thermal_devices() -> Vec<ThermalDevice> {
    let mut by_name: HashMap<String, i32> = HashMap::new();

    for i in 0.. {
        let temp_path = format!("/sys/class/thermal/thermal_zone{i}/temp");
        let type_path = format!("/sys/class/thermal/thermal_zone{i}/type");

        let temp_str = match fs::read_to_string(&temp_path) {
            Ok(s) => s,
            Err(_) => break,
        };

        let millic: i32 = match temp_str.trim().parse() {
            Ok(v) => v,
            Err(_) => continue,
        };
        let celsius = millic / 1000;

        let name = fs::read_to_string(&type_path)
            .map(|s| s.trim().to_string())
            .unwrap_or_else(|_| format!("zone{i}"));

        // Keep the highest temp seen for each device type
        let entry = by_name.entry(name).or_insert(celsius);
        if celsius > *entry {
            *entry = celsius;
        }
    }

    let mut devices: Vec<ThermalDevice> = by_name
        .into_iter()
        .map(|(name, celsius)| ThermalDevice { name, celsius })
        .collect();

    // Sort descending by temp so the hottest shows first
    devices.sort_by(|a, b| b.celsius.cmp(&a.celsius));
    devices
}

pub fn emit_temp(out: &mut impl Write) {
    let devices = read_thermal_devices();
    if devices.is_empty() {
        return;
    }

    let max = devices.iter().map(|d| d.celsius).max().unwrap_or(0);

    let devices_json: Vec<String> = devices
        .iter()
        .map(|d| {
            format!(
                "{{\"name\":{},\"celsius\":{}}}",
                json_str(&d.name),
                d.celsius
            )
        })
        .collect();

    let _ = writeln!(
        out,
        "{{\"type\":\"temp\",\"celsius\":{max},\"devices\":[{}]}}",
        devices_json.join(",")
    );
}

fn json_str(s: &str) -> String {
    let escaped = s.replace('\\', "\\\\").replace('"', "\\\"");
    format!("\"{escaped}\"")
}