use std::{
    collections::HashMap,
    fs::File,
    io::{self, BufRead, BufReader, Read, Write},
    path::Path,
    process::ExitCode,
    str::FromStr,
};

use petri_nets::{FireDirection, FireState, SimulatedNet, Simulation, SimulationStateMut};
use pns::{Net, Tid};

fn main() -> ExitCode {
    let mut save = false;
    let mut load = false;

    let mut args = std::env::args();
    args.next();
    for arg in args {
        match arg.as_ref() {
            "save" => save = true,
            "load" => load = true,
            _ => eprintln!("Ignore invalid argument '{arg}'"),
        }
    }

    let Ok(net) = Net::load("examples/example.pn".as_ref()) else {
        eprintln!("Failed to load example net");
        return ExitCode::FAILURE;
    };
    let mut net = SimulatedNet::new(net);

    let mut names = HashMap::new();
    let Ok(file) = File::open("examples/example.pnk") else {
        eprintln!("Failed to load example keys");
        return ExitCode::FAILURE;
    };
    for (tid, line) in net.transition_ids().zip(BufReader::new(file).lines()) {
        let Ok(line) = line else {
            eprintln!("Failed to read key");
            return ExitCode::FAILURE;
        };
        names.insert(tid, line);
    }

    if save && net.save("examples/example_copy.pns".as_ref()).is_err() {
        eprintln!("Failed to save example net");
    }

    if load {
        fn read_values(filename: &Path) -> std::io::Result<Vec<u32>> {
            let size = (std::fs::metadata(filename)?.len() + 3) / 4;

            let mut file = File::open(filename)?;

            (0..size)
                .map(|_| {
                    let mut value = [0; 4];
                    file.read_exact(&mut value)?;
                    Ok(u32::from_le_bytes(value))
                })
                .collect()
        }

        let Ok(data) = read_values("examples/example.pns".as_ref()) else {
            eprintln!("Reading state data failed");
            return ExitCode::FAILURE;
        };

        if net.add_simulation_from_data(data).is_err() {
            eprintln!("State initialization failed");
            return ExitCode::FAILURE;
        }
    } else {
        net.add_simulation();
    }

    enum StepAction {
        Continue,
        Reverse,
        Save,
        Quit,
    }

    let mut forward = true;
    for mut simulation in &mut net {
        fn step<D: FireDirection>(
            fire: FireState<SimulationStateMut, D>,
            names: &HashMap<Tid, String>,
        ) -> StepAction {
            if fire.callables.is_empty() {
                return StepAction::Reverse;
            }

            for (i, tid) in fire.callables.iter().enumerate() {
                println!("{}: {}", i + 1, names[tid]);
            }
            let stdin = io::stdin();
            let mut string = String::new();
            let Ok(size) = stdin.read_line(&mut string) else {
                eprintln!("Input error");
                return StepAction::Continue;
            };
            if size == 0 {
                return StepAction::Continue;
            }
            match unsafe { string.chars().next().unwrap_unchecked() } {
                'r' => return StepAction::Reverse,
                'q' => return StepAction::Quit,
                's' => return StepAction::Save,
                _ => (),
            }
            match usize::from_str(&string[..(string.len() - 1)]) {
                Ok(num) if num != 0 && num <= fire.callables.len() => {
                    fire.call(num - 1);
                }
                _ => {
                    println!(
                        "You have to input a valid number from 1 to {}",
                        fire.callables.len()
                    );
                    println!("You can also quit by writing \"q\", save the current state by writing \"s\" or reverse by writing \"r\"");
                    return StepAction::Continue;
                }
            }

            StepAction::Continue
        }

        loop {
            let step_action = if forward {
                step(simulation.prepare_call(), &names)
            } else {
                step(simulation.prepare_revert(), &names)
            };

            use StepAction::*;
            match step_action {
                Continue => (),
                Reverse => {
                    println!("Reverse play direction!");
                    forward = !forward;
                }
                Save => {
                    fn save(data: &[usize], filename: &Path) -> std::io::Result<()> {
                        let mut file = File::create(filename)?;
                        for &count in data {
                            file.write_all(&(count as u32).to_le_bytes())?;
                        }

                        Ok(())
                    }

                    let data = simulation.data();

                    println!(
                        "{}",
                        if save(data, "examples/example.pns".as_ref()).is_ok() {
                            "Saving successful"
                        } else {
                            "Saving failed"
                        }
                    );
                }
                Quit => break,
            }
        }
    }

    ExitCode::SUCCESS
}