/// Who decides an entity's actions. The sim only schedules intents for `Npc`s; a
/// `Player`'s intents come from outside (input) through `Sim::set_action`.
#[derive(Clone, Copy, PartialEq, Eq, Debug)]
pub enum EntityKind {
    Player,
    Npc,
}

/// What a hunter goes after.
#[derive(Clone, Copy, PartialEq, Eq, Debug)]
pub enum Prey {
    Player,
    Kind(u16),
}

/// The decision strategy `Sim::think` runs for an NPC. Data, not code: it can be
/// swapped at runtime (a hit hen may start fleeing) and serializes with the entity.
#[derive(Clone, Copy, PartialEq, Eq, Debug)]
pub enum Brain {
    /// Never schedules anything — the player, furniture.
    Idle,
    /// Occasionally a random king move.
    Wander,
    /// Step toward the nearest prey in sight, bumping into it on contact. Wanders
    /// when nothing is in sight.
    Hunt(Prey),
}

pub struct Entity {
    pub id:      u32,
    pub kind:    EntityKind,
    pub type_id: u16,   // sprite index into the entity tileset; also the species
    pub brain:   Brain,
    pub pos:     (i16, i16),
    pub hp:      u16,
    pub hp_max:  u16,
    /// Damage dealt per bump.
    pub attack:  u16,
}

impl Entity {
    pub fn new(id: u32, kind: EntityKind, type_id: u16, brain: Brain, pos: (i16, i16), hp: u16, attack: u16) -> Self {
        Self {
            id,
            kind,
            type_id,
            brain,
            pos,
            hp,
            hp_max: hp,
            attack,
        }
    }
}