use atomig::Atom;
use hashbrown::HashMap;

use crate::StringKey;

/// A unique key that can be used to store a reference to a type. Opaque reference to a byte
/// internally.
#[derive(Debug, Copy, Clone, Eq, PartialEq, Default, Hash, Atom)]
#[repr(C)]
pub struct TypeIdentifier {
    /// The unique internal value.
    val: u8,
}

impl From<u8> for TypeIdentifier {
    fn from(val: u8) -> Self {
        Self { val }
    }
}

impl From<TypeIdentifier> for u8 {
    fn from(id: TypeIdentifier) -> Self {
        id.val
    }
}

/// All data related to types and effectiveness.
#[derive(Debug)]
#[cfg_attr(feature = "wasm", derive(unique_type_id_derive::UniqueTypeId))]
pub struct TypeLibrary {
    /// A list of types
    types: HashMap<StringKey, TypeIdentifier>,
    /// The effectiveness of the different types against each other.
    effectiveness: Vec<Vec<f32>>,
}

impl TypeLibrary {
    /// Instantiates a new type library with a specific capacity.
    pub fn new(capacity: usize) -> TypeLibrary {
        TypeLibrary {
            types: HashMap::with_capacity(capacity),
            effectiveness: vec![],
        }
    }

    /// Gets the type identifier for a type with a name.
    pub fn get_type_id(&self, key: &StringKey) -> TypeIdentifier {
        self.types[key]
    }

    /// Gets the effectiveness for a single attacking type against a single defending type.
    pub fn get_single_effectiveness(&self, attacking: TypeIdentifier, defending: TypeIdentifier) -> f32 {
        self.effectiveness[attacking.val as usize][defending.val as usize]
    }

    /// Gets the effectiveness for a single attacking type against an amount of defending types.
    /// This is equivalent to running [`get_single_effectiveness`] on each defending type, and
    /// multiplying the results with each other.
    pub fn get_effectiveness(&self, attacking: TypeIdentifier, defending: &[TypeIdentifier]) -> f32 {
        let mut e = 1.0;
        for def in defending {
            e *= self.get_single_effectiveness(attacking, *def);
        }
        e
    }

    /// Registers a new type in the library.
    pub fn register_type(&mut self, name: &StringKey) -> TypeIdentifier {
        let id = TypeIdentifier {
            val: self.types.len() as u8,
        };
        self.types.insert(name.clone(), id);
        self.effectiveness.resize((id.val + 1) as usize, vec![]);
        for effectiveness in &mut self.effectiveness {
            effectiveness.resize((id.val + 1) as usize, 1.0)
        }
        id
    }

    /// Sets the effectiveness for an attacking type against a defending type.
    pub fn set_effectiveness(&mut self, attacking: TypeIdentifier, defending: TypeIdentifier, effectiveness: f32) {
        self.effectiveness[attacking.val as usize][defending.val as usize] = effectiveness;
    }
}

#[cfg(test)]
pub mod tests {
    use assert_approx_eq::assert_approx_eq;

    use crate::static_data::libraries::type_library::TypeLibrary;

    pub fn build() -> TypeLibrary {
        let mut lib = TypeLibrary::new(2);

        // Borrow as mut so we can insert
        let w = &mut lib;
        let t0 = w.register_type(&"foo".into());
        let t1 = w.register_type(&"bar".into());
        // Drops borrow as mut

        w.set_effectiveness(t0, t1, 0.5);
        w.set_effectiveness(t1, t0, 2.0);

        lib
    }

    #[test]
    fn add_two_types_retrieve_them() {
        let mut lib = TypeLibrary::new(2);

        // Borrow as mut so we can insert
        let w = &mut lib;
        let t0 = w.register_type(&"foo".into());
        let t1 = w.register_type(&"bar".into());
        // Drops borrow as mut

        // Borrow as read so we can read
        let r = &lib;
        assert_eq!(r.get_type_id(&"foo".into()), t0);
        assert_eq!(r.get_type_id(&"bar".into()), t1);
    }

    #[test]
    fn add_two_types_set_effectiveness_retrieve() {
        let mut lib = TypeLibrary::new(2);

        // Borrow as mut so we can insert
        let w = &mut lib;
        let t0 = w.register_type(&"foo".into());
        let t1 = w.register_type(&"bar".into());
        w.set_effectiveness(t0, t1, 0.5);
        w.set_effectiveness(t1, t0, 2.0);
        // Drops borrow as mut

        // Borrow as read so we can read
        let r = &lib;
        assert_approx_eq!(r.get_single_effectiveness(t0, t1), 0.5);
        assert_approx_eq!(r.get_single_effectiveness(t1, t0), 2.0);
    }

    #[test]
    fn add_two_types_get_aggregate_effectiveness() {
        let mut lib = TypeLibrary::new(2);

        // Borrow as mut so we can insert
        let w = &mut lib;
        let t0 = w.register_type(&"foo".into());
        let t1 = w.register_type(&"bar".into());
        w.set_effectiveness(t0, t1, 0.5);
        w.set_effectiveness(t1, t0, 2.0);
        // Drops borrow as mut

        // Borrow as read so we can read
        let r = &lib;
        assert_approx_eq!(r.get_effectiveness(t0, &[t1, t1]), 0.25);
        assert_approx_eq!(r.get_effectiveness(t1, &[t0, t0]), 4.0);
    }
}