//! # ZComponents - a stupid component storage
//!
//! I find "serious" ECS to be an overkill for turn-based game logic,
//! so I've created this simple library that does only one thing:
//! stores your components.
//!
//! ## Example:
//!
//! ```rust
//! use zcomponents::zcomponents_storage;
//!
//! #[derive(PartialEq, Eq, Clone, Copy, Debug, Hash, Default)]
//! pub struct Id(i32);
//!
//! #[derive(Clone, Debug)]
//! pub struct A {
//!     value: i32,
//! }
//!
//! #[derive(Clone, Debug)]
//! pub struct B {
//!     value: i32,
//! }
//!
//! #[derive(Clone, Debug)]
//! pub struct C;
//!
//! zcomponents_storage!(Storage<Id>: {
//!     a: A,
//!     b: B,
//!     c: C,
//! });
//!
//! // Create a new storage instance.
//! let mut storage = Storage::new();
//!
//! // It doesn't store anything yet.
//! assert_eq!(storage.ids().count(), 0);
//!
//! // Allocate a new id.
//! let id0 = storage.alloc_id();
//! assert_eq!(storage.ids().count(), 1);
//!
//! // This Entity doesn't have any components assigned.
//! assert!(!storage.is_exist(id0));
//!
//! storage.a.insert(id0, A { value: 0 });
//!
//! // Now it has a component.
//! assert!(storage.is_exist(id0));
//!
//! // Allocate another id.
//! let id1 = storage.alloc_id();
//! assert_eq!(storage.ids().count(), 2);
//!
//! storage.a.insert(id1, A { value: 1 });
//! storage.b.insert(id1, B { value: 1 });
//!
//! // Iterate over everything.
//! for id in storage.ids_collected() {
//!     // We are not sure that this entity has the component,
//!     // so we must use `get_opt`/`get_opt_mut` methods.
//!     if let Some(a) = storage.a.get_opt_mut(id) {
//!         a.value += 1;
//!     }
//!     if let Some(b) = storage.b.get_opt_mut(id) {
//!         b.value += 1;
//!         storage.c.insert(id, C);
//!     }
//! }
//!
//! // Iterate over `a` components.
//! for id in storage.a.ids_collected() {
//!     // Since we are sure that component exists,
//!     // we can just use `get`/`get_mut` version:
//!     storage.a.get_mut(id).value += 1;
//! }
//!
//! // Remove the component
//! storage.a.remove(id0);
//!
//! // Remove the whole entity
//! storage.remove(id0);
//!
//! assert!(!storage.is_exist(id0));
//! ```

use std::{
    collections::{hash_map, HashMap},
    default::Default,
    fmt::Debug,
    hash::Hash,
};

#[derive(Debug, Clone)]
pub struct ComponentContainer<Id: Hash + Eq, V> {
    data: HashMap<Id, V>,
}

impl<Id: Hash + Eq + Copy + Debug, V: Clone> Default for ComponentContainer<Id, V> {
    fn default() -> Self {
        Self::new()
    }
}

impl<Id: Hash + Eq + Copy + Debug, V: Clone> ComponentContainer<Id, V> {
    pub fn new() -> Self {
        let data = HashMap::new();
        Self { data }
    }

    pub fn get_opt(&self, id: Id) -> Option<&V> {
        self.data.get(&id)
    }

    /// Note: panics if there's no such entity.
    pub fn get(&self, id: Id) -> &V {
        self.get_opt(id)
            .unwrap_or_else(|| panic!("Can't find {:?} id", id))
    }

    pub fn get_opt_mut(&mut self, id: Id) -> Option<&mut V> {
        self.data.get_mut(&id)
    }

    /// Note: panics if there's no such entity.
    pub fn get_mut(&mut self, id: Id) -> &mut V {
        self.get_opt_mut(id)
            .unwrap_or_else(|| panic!("Can't find {:?} id", id))
    }

    /// Store a given data value under a given entity id of a stupid component
    /// if no value is already stored under that entity's id.
    pub fn insert(&mut self, id: Id, data: V) {
        assert!(self.get_opt(id).is_none());
        self.data.insert(id, data);
    }

    /// Note: panics if there's no such entity.
    pub fn remove(&mut self, id: Id) {
        assert!(self.get_opt(id).is_some());
        self.data.remove(&id);
    }

    pub fn ids(&self) -> IdIter<'_, Id, V> {
        IdIter::new(&self.data)
    }

    /// Note: Allocates Vec in heap.
    pub fn ids_collected(&self) -> Vec<Id> {
        self.ids().collect()
    }
}

#[derive(Clone, Debug)]
pub struct IdIter<'a, Id, V> {
    iter: hash_map::Iter<'a, Id, V>,
}

impl<'a, Id: Eq + Hash + Clone + 'a, V: 'a> IdIter<'a, Id, V> {
    pub fn new(map: &'a HashMap<Id, V>) -> Self {
        Self { iter: map.iter() }
    }
}

impl<'a, Id: Copy + 'a, V> Iterator for IdIter<'a, Id, V> {
    type Item = Id;

    fn next(&mut self) -> Option<Self::Item> {
        if let Some((&id, _)) = self.iter.next() {
            Some(id)
        } else {
            None
        }
    }
}

#[macro_export]
macro_rules! zcomponents_storage {
    ($struct_name:ident<$id_type:ty>: { $($component:ident: $t:ty,)* } ) => {
        use std::collections::HashMap;

        #[derive(Clone, Debug)]
        pub struct $struct_name {
            $(
                pub $component: $crate::ComponentContainer<$id_type, $t>,
            )*
            next_obj_id: $id_type,
            ids: HashMap<$id_type, ()>,
        }

        #[allow(dead_code)]
        impl $struct_name {
            pub fn new() -> Self {
                Self {
                    $(
                        $component: $crate::ComponentContainer::new(),
                    )*
                    next_obj_id: Default::default(),
                    ids: HashMap::new(),
                }
            }

            pub fn alloc_id(&mut self) -> $id_type {
                let id = self.next_obj_id;
                self.next_obj_id.0 += 1;
                self.ids.insert(id, ());
                id
            }

            pub fn ids(&self) -> $crate::IdIter<$id_type, ()> {
                $crate::IdIter::new(&self.ids)
            }

            pub fn ids_collected(&self) -> Vec<$id_type> {
                self.ids().collect()
            }

            pub fn is_exist(&self, id: $id_type) -> bool {
                $(
                    if self.$component.get_opt(id).is_some() {
                        return true;
                    }
                )*
                false
            }

            pub fn remove(&mut self, id: $id_type) {
                $(
                    if self.$component.get_opt(id).is_some() {
                        self.$component.remove(id);
                    }
                )*
            }

            pub fn debug_string(&self, id: $id_type) -> String {
                let mut s = String::new();
                $(
                    if let Some(component) = self.$component.get_opt(id) {
                        s.push_str(&format!("{:?} ", component));
                    }
                )*
                s
            }
        }
    }
}