/*
 * This file is part of laurelin_client
 * Copyright (C) 2023 Jonni Liljamo <jonni@liljamo.com>
 *
 * Licensed under GPL-3.0-only.
 * See LICENSE for licensing information.
 */

use std::collections::HashMap;

use fastrand::Rng;

use crate::{
    api::game::{Action, Command, Game},
    game_status::SupplyPile,
};

use super::{GameStatus, PlayerState, PlayerStatus};

/// funny unsafe wrapper
fn get_invoker_target<'a, K, V>(
    players: &'a mut HashMap<K, V>,
    invoker: &K,
    target: &K,
) -> (&'a mut V, &'a mut V)
where
    K: Eq + std::hash::Hash,
{
    unsafe {
        // NOTE: soo... I don't really know the consequences of possibly
        // having two mutable references to the same value, but I guess
        // I'll find out!
        // in many instances where people wanted multiple mutable references
        // to Vec or HashMap values, they only gave one in wrappers like this,
        // if the wanted values were the same.
        // e.g. returning (V, None), if the keys were the same.

        let invoker_ref = players.get_mut(invoker).unwrap() as *mut _;
        let target_ref = players.get_mut(target).unwrap() as *mut _;
        (&mut *invoker_ref, &mut *target_ref)
    }
}

pub fn parse(game: &Game) -> Result<GameStatus, ()> {
    let mut game_status = GameStatus {
        actions: game.actions.as_ref().unwrap().to_vec(),
        supply_piles: vec![],
        players: HashMap::new(),
    };

    game_status.players.insert(
        game.host_id.clone(),
        PlayerStatus {
            turn_n: 0,
            display_name: game.host.as_ref().unwrap().username.clone(),
            state: PlayerState::Idle,
            plays: 0,
            buys: 0,
            currency: 0,
            vp: 2,
            hand: vec![],
            deck: vec![],
            discard: vec![],
        },
    );

    game_status.players.insert(
        game.guest_id.clone(),
        PlayerStatus {
            turn_n: 1,
            display_name: game.guest.as_ref().unwrap().username.clone(),
            state: PlayerState::Idle,
            plays: 0,
            buys: 0,
            currency: 0,
            vp: 2,
            hand: vec![],
            deck: vec![],
            discard: vec![],
        },
    );

    for action in game_status.actions.clone() {
        parse_action(&action, game, &mut game_status);
    }

    Ok(game_status)
}

macro_rules! current_seed {
    ($action:ident) => {
        $action.seed.parse::<u64>().unwrap()
    };
}

fn parse_action(action: &Action, game: &Game, game_status: &mut GameStatus) {
    // invoker: the one who invoked the action
    // target: the one who the action affects, may also be the invoker, e.g. draw
    let (invoker, target) =
        get_invoker_target(&mut game_status.players, &action.invoker, &action.target);

    let Some(action_pos) = game_status.actions.iter().position(|a| *a == action.clone()) else {
        panic!("Action was not found in game_status.actions!");
    };

    match &action.command {
        Command::InitSupplyPile { card, amount } => {
            let pile = SupplyPile {
                card: card.clone(),
                amount: *amount,
            };

            game_status.supply_piles.push(pile);
        }
        Command::TakeFromPile { index, for_cost } => {
            // index should be within range
            assert!(*index <= game_status.supply_piles.len());
            let pile = &mut game_status
                .supply_piles
                .get_mut(*index)
                .unwrap_or_else(|| unreachable!());

            // pile should not be empty
            assert!(pile.amount > 0);

            // player should have buys
            assert!(target.buys > 0);

            // player should have enough
            assert!(*for_cost <= target.currency);

            pile.amount -= 1;
            target.buys -= 1;
            target.currency -= for_cost;

            target.discard.push(pile.card.clone());
        }
        Command::PlayCard { index } => {
            // index should be within range
            assert!(*index <= target.hand.len());

            // player should have plays
            assert!(target.plays > 0);
            target.plays -= 1;

            let card = target.hand.remove(*index);
            target.discard.push(card.clone());

            for card_action in &card.actions {
                let action = &Action::new(
                    &game.id,
                    &action.invoker,
                    &action.target,
                    &card_action.command,
                    current_seed!(action),
                );
                game_status.actions.insert(action_pos + 1, action.clone());

                parse_action(action, game, game_status);
            }
        }
        Command::Draw { amount } => {
            for _ in 0..*amount {
                if target.deck.is_empty() {
                    shuffle_discard_to_deck(target, action.seed.parse::<u64>().unwrap());
                }

                // NOTE: deck *might* still be empty, if discard was empty too
                if !target.deck.is_empty() {
                    target
                        .hand
                        .push(target.deck.pop().unwrap_or_else(|| unreachable!()));
                }
            }
        }
        Command::Discard { index } => {
            // index should be within range
            assert!(*index <= target.hand.len());
            target.discard.push(target.hand.remove(*index));
        }
        Command::EndTurn {} => {
            // NOTE: target will be the next player

            // set player to idle
            invoker.state = PlayerState::Idle;

            // clear stats
            invoker.currency = 0;
            invoker.plays = 0;
            invoker.buys = 0;

            let start_turn_action = Action::new(
                &game.id,
                &action.invoker,
                &action.target,
                &Command::StartTurn {},
                current_seed!(action),
            );
            game_status
                .actions
                .insert(action_pos + 1, start_turn_action.clone());

            parse_action(&start_turn_action, game, game_status);
        }
        Command::StartTurn {} => {
            // set the target to the play phase
            target.state = PlayerState::PlayPhase;

            // give a play and a buy at the start
            target.plays = 1;
            target.buys = 1;

            let draw_action = Action::new(
                &game.id,
                &action.target,
                &action.target,
                &Command::Draw { amount: 4 },
                current_seed!(action),
            );
            game_status
                .actions
                .insert(action_pos + 1, draw_action.clone());

            parse_action(&draw_action, game, game_status);
        }
        Command::ChangePlayerState { state } => {
            target.state = *state;
        }
        Command::RollForCurrency { min, max } => {
            target.currency += Rng::with_seed(action.seed.parse::<u64>().unwrap()).usize(min..=max);
        }
        #[allow(unreachable_patterns)]
        _ => todo!(),
    }
}

fn shuffle_discard_to_deck(target: &mut PlayerStatus, seed: u64) {
    let cards = target.discard.to_vec();
    target.discard.clear();

    target.deck = cards;

    let rng = Rng::with_seed(seed);
    rng.shuffle(&mut target.deck);
}