use std::fmt::{Debug, Formatter};
use std::sync::Arc;

use crate::dynamic_data::DamageSource;
use crate::dynamic_data::ExecutingMove;
use crate::dynamic_data::Pokemon;
use crate::static_data::Species;
use crate::static_data::{Form, Statistic};

/// The event hook is used to store external functions that listen to events.
///
/// Events happen in many
/// different places in the battle, and can be used for GUI applications to show that these events
/// are happening.
#[derive(Default)]
pub struct EventHook {
    /// All the registered event listeners on the hook.
    evt_hook_function: Vec<fn(&Box<&Event>)>,
}

impl EventHook {
    /// Register a new listener. This will start receiving all events in the battle. Multiple event
    /// listeners can exist at the same time. Note that for these functions the event will be disposed
    /// of after the event is finished being sent.
    pub fn register_listener(&mut self, func: fn(&Box<&Event>)) {
        self.evt_hook_function.push(func);
    }

    /// Run a new event. This will send the event to all externally defined event listeners. It will
    /// dispose of the event afterwards.
    pub fn trigger(&self, evt: Event) {
        let b = Box::new(&evt);
        for f in &self.evt_hook_function {
            f(&b);
        }
    }
}

impl Debug for EventHook {
    fn fmt(&self, _f: &mut Formatter<'_>) -> std::fmt::Result {
        Ok(())
    }
}

/// The different events that can occur during the battle, for which a GUI should show something.
#[derive(Debug)]
pub enum Event<'own> {
    /// A switch event happens when a Pokemon gets switched out for something else.
    Switch {
        /// The side the Pokemon got switched from/on
        side_index: u8,
        /// The index of the Pokemon that got switched in/out on its side
        index: u8,
        /// The new Pokemon that will be on the spot. If none, the spot will now be empty.
        pokemon: Option<&'own Pokemon>,
    },
    /// A swap event happens when two Pokemon on a side swap positions. Note that this is rare.
    Swap {
        /// The side the Pokemon swapped on.
        side_index: u8,
        /// The index on the side of the first Pokemon that was swapped.
        index_a: u8,
        /// The index on the side of the second pokemon that was swapped.
        index_b: u8,
    },
    /// This event happens when a Pokemon changes species during battle. While not normally occuring
    /// this can be useful for things such as mid-battle evolutions, which some fanmade implementations
    /// enjoy.
    SpeciesChange {
        /// The pokemon that changed species.
        pokemon: &'own Pokemon,
        /// The new species of the Pokemon.
        species: Arc<Species>,
        /// The form of the species the Pokemon will have.
        form: Arc<Form>,
    },
    /// This event happens when a Pokemon changes form during battle. This is rather common.
    FormChange {
        /// The pokemon that changed forms.
        pokemon: &'own Pokemon,
        /// The new form of the Pokemon.
        form: &'own Form,
    },
    /// This event happens when a Pokemon takes damage.
    Damage {
        /// The Pokemon that takes damage.
        pokemon: &'own Pokemon,
        /// The source of damage.
        source: DamageSource,
        /// The health of the Pokemon before the damage.
        original_health: u32,
        /// The health of the Pokemon after the damage.
        new_health: u32,
    },
    /// This event happens when a Pokemon gets healed
    Heal {
        /// The Pokemon that gets healed.
        pokemon: &'own Pokemon,
        /// The health of the Pokemon before the heal.
        original_health: u32,
        /// The health of the Pokemon after the heal.
        new_health: u32,
    },
    /// This event happens when a Pokemon faints.
    Faint {
        /// The pokemon that has fainted.
        pokemon: &'own Pokemon,
    },
    /// This event happens when a Pokemon uses a move on a target, just before any hits.
    MoveUse {
        /// The data of the move used.
        executing_move: &'own ExecutingMove,
    },
    /// This event happens when a Pokemon missed.
    Miss {
        /// The pokemon that missed.
        user: &'own Pokemon,
    },
    /// The turn is finished running, waiting for new input.
    EndTurn,
    /// A pokemon had its stat boost changed
    StatBoostChange {
        /// The pokemon that had its stat boosts changed.
        user: &'own Pokemon,
        /// The statistic that changed.
        stat: Statistic,
        /// The value of the stat before the change.
        old_value: i8,
        /// The value of the stat after the change.
        new_value: i8,
    },
}