use crate::utils::powmod;
use crate::window_state::WindowState;
use eframe::egui;

#[derive(PartialEq, Eq)]
enum State {
    Idle,
    Requested,
    Generated,
}

pub struct Window {
    state: State,
    p: u64,
    g: u64,
    a: u64,
    y: u64,
}

impl Default for Window {
    fn default() -> Self {
        Self {
            state: State::Idle,
            p: 0,
            g: 0,
            a: 0,
            y: 0,
        }
    }
}

fn min_order(x: u64, order: u64) -> u64 {
    let mut min = 0;
    let mut pow = x;
    for power in 1..order {
        if pow == 1 {
            min = power;
            break;
        }
        pow = (pow * x) % order;
    }
    return min;
}

impl Window {
    fn generate(&mut self) {
        let primes = erathosphene(10000);
        let i = fastrand::usize(4..primes.len());
        self.p = primes[i as usize];

        for i in 1..self.p {
            if min_order(i, self.p) == self.p - 1 {
                self.g = i;
                break;
            }
        }

        self.a = fastrand::u64(1..=self.p - 1);
        self.y = powmod(self.g, self.a, self.p);
    }
}

fn erathosphene(n: u64) -> Vec<u64> {
    let mut is_prime = vec![true; n as usize];
    let mut p = 2;
    while p * p < n {
        let mut cur = p * p;
        while cur < n {
            is_prime[cur as usize] = false;
            cur += p;
        }
        while !is_prime[(p + 1) as usize] {
            p += 1;
        }
        p += 1
    }
    let mut primes = Vec::new();
    is_prime.iter().enumerate().for_each(|(i, p)| {
        if *p {
            primes.push(i as u64);
        }
    });
    return primes;
}

impl WindowState for Window {
    fn get_name(&self) -> &str {
        "Генерация ключей"
    }

    fn update(&mut self, ui: &mut egui::Ui) {
        if ui.button("Сгенерировать").clicked() {
            self.state = State::Requested;
        }
        if self.state == State::Requested {
            self.generate();
            self.state = State::Generated;
        }
        if self.state == State::Generated {
            ui.horizontal(|ui| {
                ui.label("Модуль p:");
                let mut tmp = self.p.to_string();
                ui.add_enabled(false, egui::TextEdit::singleline(&mut tmp));
            });
            ui.horizontal(|ui| {
                ui.label("Порождающий элемент g группы Z_p:");
                let mut tmp = self.g.to_string();
                ui.add_enabled(false, egui::TextEdit::singleline(&mut tmp));
            });
            ui.horizontal(|ui| {
                ui.label("Секретный ключ a:");
                let mut tmp = self.a.to_string();
                ui.add_enabled(false, egui::TextEdit::singleline(&mut tmp));
            });
            ui.horizontal(|ui| {
                ui.label("Публичный ключ y:");
                let mut tmp = self.y.to_string();
                ui.add_enabled(false, egui::TextEdit::singleline(&mut tmp));
            });
            if ui.button("Скопировать публичный ключ").clicked() {
                ui.output().copied_text = format!("{},{}", self.y, self.p);
            }
            if ui.button("Скопировать секретный ключ").clicked() {
                ui.output().copied_text = format!("{},{},{}", self.g, self.a, self.p);
            }
        }
    }
}