use serde::{Deserialize, Serialize};
use serde_json;
use tokio::join;
use std::fmt::Debug;
use std::fs;
use std::path::Path;
use std::process::{Command, Output};
use tokio::time::{Duration, Instant};
use tokio::sync::mpsc;

/// # an Error enum (nextly will be deleted and replaced)
enum CustomError {
    Fatal,
}

/// # struct for the 1st level in json conf file
/// > (needed in serialization and deserialization)
#[derive(Debug, Serialize, Deserialize, Clone)]
struct Processes {
    #[serde(default)]
    processes : Vec<TrackingProcess>,
}

/// # struct for each process to contain info, such as name, path and dependencies
/// > (needed in serialization and deserialization)
#[derive(Debug, Serialize, Deserialize, Clone)]
struct TrackingProcess {
    name : String, 
    path : String,
    dependencies: Dependencies,
}

/// # struct for processes' dependecies including files and services
/// > (needed in serialization and deserialization)
#[derive(Debug, Serialize, Deserialize, Clone)]
struct Dependencies {
    #[serde(default)]
    files : Vec<Files>,
    #[serde(default)]
    services: Vec<Services>,
}

/// # struct for containing file object with its triggers to manipulate in daemons
/// > (needed in serialization and deserialization)
#[derive(Debug, Serialize, Deserialize, Clone)]
struct Files {
    filename : String,
    src : String, 
    triggers : FIleTriggers,
}

/// # struct for containing service object with its triggers to manipulate in daemons
/// > (needed in serialization and deserialization)
#[derive(Debug, Serialize, Deserialize, Clone)]
struct Services {
    hostname : String,
    port :  u32,
    triggers : ServiceTriggers,
} 

/// # struct for instancing each service's policies such as on lost or time to wait till reachable
/// > (needed in serialization and deserialization)
#[derive(Debug, Serialize, Deserialize, Clone)]
struct ServiceTriggers {
    wait : u32, 
    delay: u32,
    #[serde(rename="onLost")]
    on_lost : String,
}

/// # struct for instancing each file's policies such as ondelete or onupdate events
/// > (needed in serialization and deserialization)
#[derive(Debug, Serialize, Deserialize, Clone)]
struct FIleTriggers {
    #[serde(rename="onDelete")]
    on_delete : String,
    #[serde(rename="onChange")]
    on_change : String,
}

#[tokio::main(flavor = "multi_thread")]
async fn main() {
    let processes = load_processes("settings.json");
    // let mut error_counter = 0;
    
    if processes.processes.len() == 0 {
        eprintln!("Error: Processes list is null, runner-rs initialization is stopped");
        return;
    }
    let mut handler: Vec<tokio::task::JoinHandle<()>> = vec![];

    for proc in processes.processes.iter() {
        println!("Process '{}' on stage:\n{}\nDepends on {} file(s), {} service(s)\n",
            proc.name, 
            proc.path, 
            proc.dependencies.files.len(), 
            proc.dependencies.services.len());

        // creating msg channel 
        let (tx, mut rx) = mpsc::channel::<u8>(1);

        let proc_clone = proc.clone();
        let tx_clone = tx.clone();
        let event = tokio::spawn(async move {
            run_daemons(&proc_clone, tx_clone, &mut rx).await;
        });
        handler.push(event);
    }
    for i in handler {
        i.await.unwrap();
    }

    return;
}

/// # async func to run 3 main daemons (now its more like tree-form than classiacl 0.1.0 form )
/// > hint : give mpsc with capacity 1 to jump over potential errors during running process
/// ** in [developing](https://github.com/prplV/runner-rs "REPOSITORY") **
async fn run_daemons(
    proc: &TrackingProcess, 
    tx: mpsc::Sender<u8>,
    rx: &mut mpsc::Receiver<u8>
) 
{
    loop {
        let run_hand = running_handler(&proc, tx.clone());

        tokio::select! {
            _ = run_hand => {},
            _val = rx.recv() => {
                match _val.unwrap() {
                    // 1 - File-dependency handling error -> terminating (after waiting)
                    1 => {
                        if is_active(&proc.name) {
                            println!("Dependency handling error: Terminating {} process ..." , &proc.name);
                            terminate_process(&proc.name).await;
                        }
                        // break;
                    },
                    // 2 - File-dependency handling error -> holding (after waiting)
                    2 => {
                        if !is_frozen(&proc.name) {
                            println!("Dependency handling error: Freezing {} process ..." , &proc.name);
                            freeze_process(&proc.name).await;
                        }
                    },
                    // 3 - Running process error
                    3 => {
                        println!("Error due to starting {} process", &proc.name);
                    },
                    // 4 - Timeout of waiting service-dependency -> staying (after waiting) 
                    4 => {
                        println!("Timeout of waiting service-dependency: Ignoring  for {} process ..." , &proc.name);
                    },
                    // 5 - Timeout of waiting service-dependency -> terminating (after waiting)
                    5 => {
                        if is_active(&proc.name) {
                            println!("Timeout of waiting service-dependency: Terminating {} process ..." , &proc.name);
                            terminate_process(&proc.name).await;
                        }
                        // break;
                    },
                    // 6 - Timeout of waiting service-dependency -> holding (after waiting)
                    6 => {
                        if !is_frozen(&proc.name) {
                            println!("Timeout of waiting service-dependency: Freezing {} process ..." , &proc.name);
                            freeze_process(&proc.name).await;
                        }
                    },
                    // // 7 - File-dependency change -> terminating (after check)
                    // 7 => {},
                    // // 8 - File-dependency change -> restarting (after check)
                    // 8 => {},
                    // // 9 - File-dependency change -> staying (after check)
                    // 9 => {},

                    // 10 - Process unfreaze call via file handler
                    10 => {
                        if is_frozen(&proc.name) {
                            println!("Unfreezing process {} call...", &proc.name);
                            unfreeze_process(&proc.name).await;
                        }
                    },
                    // 11 - Process unfreaze call via service handler
                    11 => {
                        if is_frozen(&proc.name) {
                            println!("Unfreezing process {} call...", &proc.name);
                            unfreeze_process(&proc.name).await;
                        }
                    },
                    // 101 - Impermissible trigger values in JSON
                    101 => {
                        println!("Impermissible trigger values in JSON");
                        break;
                    },
                    _ => {}, 
                }
            },
        }
        // tokio::task::yield_now().await;
    }    
    
}

fn load_processes(json_filename: &str) -> Processes{
    let read = fs::read_to_string(json_filename).expect(format!("Missing '{}' file. Cannot start runner", json_filename).as_str());
    serde_json::from_str::<Processes>(&read).expect(format!("Parsing error in '{}' file. Cannot start runner", json_filename).as_str())
}

fn get_pid(name: &str) -> Output {
    Command::new("pidof")
        .arg(name)
        .output()
        .expect("Failed to execute command 'pidof'")
}
fn is_active(name: &str)-> bool {
    let output = Command::new("pidof")
        .arg(name)
        .output()
        .expect("Failed to execute command 'pidof'");
    !String::from_utf8_lossy(&output.stdout).trim().is_empty()
}
fn is_frozen(name: &str) -> bool {
    let temp = get_pid(name);
    let pid = String::from_utf8_lossy(&temp.stdout);
    if pid.trim().is_empty(){
        return false;
    } else {
        let cmd = Command::new("ps")
        .args(["-o", "stat=", "-p", pid.trim()])
        .output()
        .expect("Failed to execute ps command");
        return !(String::from_utf8_lossy(&cmd.stdout) == "Sl+\n");
    }
}
async fn terminate_process (name: &str) {
    let _ = Command::new("pkill")
        .arg(name)
        .output()
        .expect("Failed to execute command 'pkill'");
}
async fn freeze_process(name: &str) {
    // let pid = get_pid(name);
    let _ =  Command::new("pkill")
    .args(["-STOP", name])
    .output()
    .expect("Failed to freeze process");
}
async fn unfreeze_process(name: &str) {
    // let pid = get_pid(name);
    let _ =  Command::new("pkill")
    .args(["-CONT", name])
    .output()
    .expect("Failed to unfreeze process");
}

async fn start_process(name: &str, path: &str) -> Result<(), CustomError> {
    let runsh = format!("{}{}", path, "/run.sh");
    let mut command = Command::new("bash");
    command.arg(runsh);

    match command.spawn() {
        Ok(_) => {
            println!("Process {} is running now!", name);
            Ok(())
        },
        Err(_) => {
            return Err(CustomError::Fatal)
        },
    }
}
// check process status daemon 
async fn running_handler(prc: &TrackingProcess, tx: mpsc::Sender<u8>){
        // println!("running daemon on {}", prc.name);
        // services and files check (once)  
        let files_check = file_handler(&prc.name, &prc.dependencies.files, tx.clone());
        let services_check = service_handler(&prc.name, &prc.dependencies.services, tx.clone());

        let res = join!(files_check, services_check);
        // if inactive -> spawn checks -> active is true 
        if !is_active(&prc.name) && res.0.is_ok() && res.1.is_ok(){
            if start_process(&prc.name, &prc.path).await.is_err() {
                    tx.send(3).await.unwrap();
                    return;
            }
        } 
        // if frozen  -> spawn checks -> unfreeze is true
        else if is_frozen(&prc.name) && res.0.is_ok() && res.1.is_ok(){
            tx.send(10).await.unwrap();
            return;
        }
        tokio::time::sleep(Duration::from_millis(100)).await;
        tokio::task::yield_now().await;   
}

async fn file_handler(name: &str, files: &Vec<Files>, tx: mpsc::Sender<u8>) -> Result<(), CustomError>{
            // println!("file daemon on {}", name);
    for file in files {
        if check_file(&file.filename, &file.src).is_err() {
            if !is_active(name) || is_frozen(name) {
                return Err(CustomError::Fatal);
            }
            match file.triggers.on_delete.as_str() {
                "stay" => {
                    continue;
                },
                "stop" => {
                    if is_active(name) {
                        tx.send(1).await.unwrap();
                    }
                    return Err(CustomError::Fatal);
                },
                "hold" => {
                    if is_active(name) {
                        tx.send(2).await.unwrap();
                        return Err(CustomError::Fatal);
                    }
                },
                _ => {
                    tokio::time::sleep(Duration::from_millis(50)).await;
                    tx.send(101).await.unwrap();
                    return Err(CustomError::Fatal);
                },
            }
        }
    }
    tokio::time::sleep(Duration::from_millis(100)).await;
    tokio::task::yield_now().await;
    Ok(())
}
fn check_file(filename: &str, path: &str) -> Result<(), CustomError> {
    let fileconcat = format!("{}{}", path, filename);
    let path = Path::new(&fileconcat);
    if path.exists() {
        Ok(())
    } else {
        Err(CustomError::Fatal)
    }
}

async fn service_handler(name: &str, services: &Vec<Services>, tx: mpsc::Sender<u8>) -> Result<(), CustomError> {
            // println!("service daemon on {}", name);
    for serv in services {
        if check_service(&serv.hostname, &serv.port).await.is_err() {
            if !is_active(name) || is_frozen(name) {
                return Err(CustomError::Fatal);
            }
            println!("Service {}:{} is unreachable for process {}", &serv.hostname, &serv.port, &name);
            match serv.triggers.on_lost.as_str() {
                "stay" => {
                },
                "stop" => {
                    if looped_service_connecting(name, serv).await.is_err() {
                        tx.send(5).await.unwrap();
                        tokio::time::sleep(Duration::from_millis(100)).await;
                        return Err(CustomError::Fatal);
                    }
                },
                "hold" => {
                    if is_frozen(name) {
                        return Err(CustomError::Fatal);
                    }
                    if looped_service_connecting(name, serv).await.is_err() {
                        tx.send(6).await.unwrap(); 
                        tokio::time::sleep(Duration::from_millis(100)).await;
                        return Err(CustomError::Fatal);
                    }
                },
                _ => {
                    tx.send(101).await.unwrap();
                    return Err(CustomError::Fatal);
                },
            }
        }   
    }
    tokio::time::sleep(Duration::from_millis(100)).await;
    tokio::task::yield_now().await;
    Ok(())    
}

async fn looped_service_connecting(
    name: &str,
    serv: &Services
) -> Result<(), CustomError> 
{
    if serv.triggers.wait == 0 {
        loop { 
            tokio::time::sleep(Duration::from_secs(serv.triggers.delay.into())).await;
            println!("Attempting to connect from {} process to {}:{}",&name, &serv.hostname, &serv.port );
            match check_service(&serv.hostname, &serv.port).await {
                Ok(_) => {
                    println!("SUCCESS!");
                    break;
                },
                Err(_) => {
                    continue;
                },
            }
        }
        return Ok(());
    } else {
        let start = Instant::now();
        while start.elapsed().as_secs() < serv.triggers.wait.into() {
            tokio::time::sleep(Duration::from_secs(serv.triggers.delay.into())).await;
            println!("Attempting to connect from {} process to {}:{}",&name, &serv.hostname, &serv.port );
            match  check_service(&serv.hostname, &serv.port).await {
                Ok(_) => {
                    println!("SUCCESS!");
                    return Ok(());
                },
                Err(_) => {
                    continue;
                },
            }
        }
        return Err(CustomError::Fatal);
    }
}
async fn check_service(host: &str, port: &u32) -> Result<(), CustomError> {
    let mut command = Command::new("bash");
    command.args(["service-checker.sh", host, &port.to_string()]);

    match command.output() {
        Ok(output) => {
            if output.status.success() {
                return Ok(());
            } else {
                return Err(CustomError::Fatal);
            }
    },
        Err(_) => {
            return Err(CustomError::Fatal);
        },
    };
}