/* Varanus: client/server system monitor for PCs.
 *
 * Copyright (c) 2024  Scott Lawrence.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
 * and associated documentation files (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all copies or
 * substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING
 * BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

/* TODO
 *
 * Accept command-line arguments to query only part of JSON. (Maybe also a formatting string?)
 *
 * Forecast
 *
 * Handle "no socket file" more gracefully
 *
 */

use std::error;
use std::fs::{read_dir,read_to_string,remove_file};
use std::io::{Read,Write};
use std::path::{Path,PathBuf};
use std::os::unix::net::{UnixStream,UnixListener};
use std::str;
use std::sync::{Arc,Mutex};
use std::thread::{sleep,spawn};
use std::time::{Duration,Instant,SystemTime};

use clap::Parser;
use serde::{Serialize,Deserialize};
use signal_hook::{consts::SIGINT,iterator::Signals};

mod forecast;

fn read_line<P: AsRef<Path>>(p: P) -> Result<String> {
    let s = read_to_string(p)?;
    Ok(s.lines().next().ok_or("")?.to_string())
}

#[derive(Default)]
#[repr(C)]
struct Sysinfo {
    uptime: cty::c_long,
    loads: [cty::c_ulong; 3],
    totalram: cty::c_ulong,
    freeram: cty::c_ulong,
    sharedram: cty::c_ulong,
    bufferram: cty::c_ulong,
    totalswap: cty::c_ulong,
    freeswap: cty::c_ulong,
    procs: cty::c_ushort,
    totalhigh: cty::c_ulong,
    freehigh: cty::c_ulong,
    mem_unit: cty::c_uint,
    /*char _f[20-2*sizeof(long)-sizeof(int)];*/
}

extern "C" {
    fn sysinfo(si: *mut Sysinfo) -> cty::c_int;
}

impl Sysinfo {
    fn new() -> Self {
        let mut si = Sysinfo::default();
        unsafe { sysinfo(&mut si) };
        return si;
    }
}

#[derive(Parser)]
struct Cli {
    #[arg(short='d', long)]
    daemon: bool,
    #[arg(short='v', long)]
    verbose: bool,
    #[arg(short='D', long, default_value="2.0")]
    delay: f64,
    #[arg(short='s', long, default_value="varanus.sock")]
    socket: String,
}

#[derive(Debug, Serialize, Deserialize, Default)]
struct Battery {
    path: PathBuf,
}

impl Battery {
    fn new(p: &Path) -> Self {
        Battery {
            path: p.to_path_buf(),
        }
    }
}

#[derive(Debug, Serialize, Deserialize, Default)]
struct Mains {
    online: bool,
}

#[derive(Debug, Serialize, Deserialize, Default)]
struct Power {
    batteries: Vec<Battery>,
    mains: Vec<Mains>,
}

impl Power {
    fn new() -> Self {
        let mut p = Power::default();
        for path in read_dir("/sys/class/power_supply").unwrap() {
            match path {
                Ok(de) => {
                    let typefile = de.path().join("type");
                    let line = read_line(typefile).unwrap();
                    if line == "Battery" {
                        let bat = Battery::new(&de.path());
                        p.batteries.push(bat);
                    }
                },
                Err(_) => (),
            }
        }
        return p
    }

    fn update(&mut self) {
    }
}

#[derive(Debug, Serialize, Deserialize)]
struct Process {
}

#[derive(Debug, Serialize, Deserialize)]
struct ProcFS {
}

impl ProcFS {
}

#[derive(Debug, Serialize, Deserialize, Default)]
struct Memory {
    total: u64,
    free: u64,
}

impl Memory {
    fn new(si: Sysinfo) -> Self {
        let mut mem = Memory::default();
        mem.update(si);
        return mem;
    }

    fn update(&mut self, si: Sysinfo) {
        self.total = si.totalram;
        self.free = si.freeram;
    }
}

#[derive(Debug, Serialize, Deserialize)]
struct State {
    asof: SystemTime,
    uptime: i64,
    power: Power,
    memory: Memory,
}

impl State {
    fn new() -> Self {
        let asof = SystemTime::now();
        let si = Sysinfo::new();
        return State {
            asof: asof,
            uptime: si.uptime,
            power: Power::new(),
            memory: Memory::new(si)
        }
    }

    fn update(&mut self) {
        let si = Sysinfo::new();
        self.asof = SystemTime::now();
        self.uptime = si.uptime;
        self.memory.update(si);
    }
}

type Result<T> = std::result::Result<T, Box<dyn error::Error>>;

fn update_state(state: &mut State) {
    state.update();
}

fn get_state(sockfile: String) -> Result<State> {
    let mut socket = UnixStream::connect(sockfile)?;
    let mut buf = vec![];
    socket.read_to_end(&mut buf)?;
    Ok(serde_json::from_str::<State>(str::from_utf8(&buf)?)?)
}

struct Listener {
    file: String,
    state: Arc<Mutex<State>>,
}

impl Listener {
    fn new(socket: String, state_mutex: &Arc<Mutex<State>>) -> Self {
        return Listener {
            file: socket,
            state: Arc::clone(state_mutex),
        }
    }

    fn listen(&self) {
        let state_mutex = Arc::clone(&self.state);
        let sfn1 = self.file.clone();
        let sfn2 = self.file.clone();
        spawn(move || {
            match Signals::new([SIGINT]) {
                Ok(mut signals) => for _sig in signals.forever() {
                    let _ = remove_file(&sfn1);
                    std::process::exit(0)
                },
                Err(_) => ()
            }
        });
        spawn(move || {
            let _ = remove_file(&sfn2);
            let listener = UnixListener::bind(sfn2).unwrap();
            loop {
                match listener.accept() {
                    Ok((mut socket,_addr)) => {
                        let json = {
                            let state = state_mutex.lock().unwrap();
                            serde_json::to_string(&*state).unwrap()
                        };
                        socket.write_all(json.as_bytes()).unwrap();
                    },
                    Err(e) => println!("error: {:?}", e)
                }
            }
        });
    }
}

impl Drop for Listener {
    fn drop(&mut self) {
        let _ = remove_file(&self.file);
    }
}

fn main() {
    let args = Cli::parse();
    if args.daemon {
        let start = Instant::now();
        let delay_ms: u64 = (args.delay * 1000.0) as u64;
        let mut cycle: u64 = 0;
        let state_mutex = Arc::new(Mutex::new(State::new()));
        let listener = Listener::new(args.socket, &state_mutex);
        listener.listen();
        loop {
            if args.verbose {
                println!("{:?} elapsed; updating state...", start.elapsed());
            }
            {
                let mut state = state_mutex.lock().unwrap();
                update_state(&mut state);
            }
            cycle += 1;
            sleep(Duration::from_millis(cycle*delay_ms) - start.elapsed());
        }
    } else {
        let state = get_state(args.socket).unwrap();
        println!("{:#?}", state)
    }
}