use crate::dynamic_data::choices::TurnChoice;
use crate::dynamic_data::Pokemon;

/// The ChoiceQueue is used to run choices one by one.
///
/// It functions internally by holding a vector of choices, and passing ownership of the turn choice
/// to the turn executor one by one, replacing it with empty spots at the start. It holds several
/// helper functions to change the turn order while doing the execution. This is needed, as several
/// moves in Pokemon actively mess with this order.
#[derive(Debug)]
pub struct ChoiceQueue {
    /// Our storage of turn choices. Starts out completely filled, then slowly empties as turns get
    /// executed.
    queue: Vec<Option<TurnChoice>>,
    /// The current index of the turn we need to execute next.
    current: usize,
}

impl ChoiceQueue {
    /// Initializes a ChoiceQueue. We expect the given queue to already be sorted here.
    pub(crate) fn new(queue: Vec<Option<TurnChoice>>) -> Self {
        Self { queue, current: 0 }
    }

    /// Dequeues the next turn choice to be executed. This gives ownership to the callee, and replaces
    /// our own reference to the turn choice with an empty spot. It also increments the current position
    /// by one.
    pub fn dequeue(&mut self) -> TurnChoice {
        let c = self.queue[self.current].take();
        self.current += 1;
        c.unwrap()
    }

    /// This reads what the next choice to execute will be, without modifying state.
    pub fn peek(&self) -> &TurnChoice {
        self.queue[self.current].as_ref().unwrap()
    }

    /// Check if we have any choices remaining.
    pub fn has_next(&self) -> bool {
        self.current < self.queue.len()
    }

    /// This resorts the yet to be executed choices. This can be useful for dealing with situations
    /// such as Pokemon changing forms just after the very start of a turn, when turn order has
    /// technically already been decided.
    pub fn resort(&mut self) {
        let len = self.queue.len();
        self.queue[self.current..len].sort_unstable_by(|a, b| b.cmp(a));
    }

    /// This moves the choice of a specific Pokemon up to the next choice to be executed.
    pub fn move_pokemon_choice_next(&mut self, pokemon: &Pokemon) {
        let mut desired_index = None;
        // Find the index for the choice we want to move up.
        for index in self.current..self.queue.len() {
            if let Some(choice) = &self.queue[index] {
                if std::ptr::eq(choice.user().as_ref(), pokemon) {
                    desired_index = Some(index);
                    break;
                }
            }
        }
        // If we couldn't find a choice, we can't execute, return.
        if desired_index.is_none() {
            return;
        }
        let desired_index = desired_index.unwrap();
        // If the choice we want to move up is already the next choice, just return.
        if desired_index == self.current {
            return;
        }

        // Take the choice we want to move forward out of it's place.
        let choice = self.queue[desired_index].take().unwrap();
        // Iterate backwards from the spot before the choice we want to move up, push them all back
        // by 1 spot.
        for index in (desired_index - 1)..self.current {
            self.queue.swap(index, index + 1);
        }
        // Place the choice that needs to be next in the next to be executed position.
        let _ = self.queue[self.current].insert(choice);
    }

    /// Internal helper function to be easily able to iterate over the yet to be executed choices.
    pub(crate) fn get_queue(&self) -> &[Option<TurnChoice>] {
        &self.queue[self.current..self.queue.len()]
    }
}