ddmills/geotic

import { Engine, Component } from 'geotic';

// define some simple components
class Position extends Component {
    static properties = {
        x: 0,
        y: 0,
    };
}

class Velocity extends Component {
    static properties = {
        x: 0,
        y: 0,
    };
}

class IsFrozen extends Component {}

const engine = new Engine();

// all Components and Prefabs must be `registered` by the engine
engine.registerComponent(Position);
engine.registerComponent(Velocity);
engine.registerComponent(IsFrozen);

...
// create a world to hold and create entities and queries
const world = engine.createWorld();

// Create an empty entity. Call `entity.id` to get the unique ID.
const entity = world.createEntity();

// add some components to the entity
entity.addComponent(Position, { x: 4, y: 10 });
entity.addComponent(Velocity, { x: 1, y: .25 });

// create a query that tracks all components that have both a `Position`
// and `Velocity` component but not a `IsFrozen` component. A query can
// have any combination of `all`, `none` and `any`
const kinematics = world.createQuery({
    all: [Position, Velocity],
    none: [IsFrozen]
});

...

// geotic does not dictate how your game loop should behave
const loop = (dt) => {
    // loop over the result set to update the position for all entities
    // in the query. The query will always return an up-to-date array
    // containing entities that match
    kinematics.get().forEach((entity) => {
        entity.position.x += entity.velocity.x * dt;
        entity.position.y += entity.velocity.y * dt;
    });
};

...

// serialize all world entities into a JS object
const data = world.serialize();

...

// convert the serialized data back into entities and components
world.deserialize(data);

import { Engine } from 'geotic';

const engine = new Engine();

engine.registerComponent(clazz);
engine.registerPrefab({ ... });
engine.destroyWorld(world);

import { Engine } from 'geotic';

const engine = new Engine();
const world = engine.createWorld();

// create/destroy entities
world.createEntity();
world.getEntity(entityId);
world.getEntities();
world.destroyEntity(entityId);
world.destroyEntities();

// create queries
world.createQuery({ ... });

// create entity from prefab
world.createPrefab('PrefabName', { ... });

// serialize/deserialize entities
world.serialize();
world.serialize(entities);
world.deserialize(data);

// create an entity with a new ID and identical components & properties
world.cloneEntity(entity);

// generate unique entity id
world.createId();

// destroy all entities and queries
world.destroy();

const zombie = world.createEntity();

zombie.add(Name, { value: 'Donnie' });
zombie.add(Position, { x: 2, y: 0, z: 3 });
zombie.add(Velocity, { x: 0, y: 0, z: 1 });
zombie.add(Health, { value: 200 });
zombie.add(Enemy);

zombie.name.value = 'George';
zombie.velocity.x += 12;

zombie.fireEvent('hit', { damage: 12 });

if (zombie.health.value <= 0) {
    zombie.destroy();
}

import { Component } from 'geotic';

class Health extends Component {
    // these props are defaulting to 10
    // anything defined here will be serialized
    static properties = {
        current: 10,
        maximum: 10,
    };

    // arbitrary helper methods and properties can be declared on
    // components. Note that these will NOT be serialized
    get isAlive() {
        return this.current > 0;
    }

    reduce(amount) {
        this.current = Math.max(this.current - amount, 0);
    }

    heal(amount) {
        this.current = Math.min(this.current + amount, this.maximum);
    }

    // This is automatically invoked when a `damage-taken` event is fired
    // on the entity: `entity.fireEvent('damage-taken', { damage: 12 })`
    // the `camelcase` library is used to map event names to methods
    onDamageTaken(evt) {
        // event `data` is an arbitray object passed as the second parameter
        // to entity.fireEvent(...)
        this.reduce(evt.data.damage);

        // handling the event will prevent it from continuing
        // to any other components on the entity
        evt.handle();
    }
}

class Impulse extends Component {
    static properties = {
        x: 0,
        y: 0,
    };
    static allowMultiple = true;
}

ecs.registerComponent(Impulse);

...

// add multiple `Impulse` components to the player
player.add(Impulse, { x: 3, y: 2 });
player.add(Impulse, { x: 1, y: 0 });
player.add(Impulse, { x: 5, y: 6 });

...

// returns the array of Impulse components
player.impulse;
// returns the Impulse at position `2`
player.impulse[2];
// returns `true` if the component has an `Impulse` component
player.has(Impulse);

// the `player.impulse` property is an array
player.impulse.forEach((impulse) => {
    console.log(impulse.x, impulse.y);
});

// remove and destroy the first impulse
player.impulse[0].destroy();

...

class EquipmentSlot extends Component {
    static properties = {
        name: 'hand',
        itemId: 0,
    };
    static allowMultiple = true;
    static keyProperty = 'name';

    get item() {
        return this.world.getEntity(this.itemId);
    }

    set item(entity) {
        return this.itemId = entity.id;
    }
}

ecs.registerComponent(EquipmentSlot);

...

const player = ecs.createEntity();
const helmet = ecs.createEntity();
const sword = ecs.createEntity();

// add multiple equipment slot components to the player
player.add(EquipmentSlot, { name: 'rightHand' });
player.add(EquipmentSlot, { name: 'leftHand', itemId: sword.id });
player.add(EquipmentSlot, { name: 'head', itemId: helmet.id });

...

// since the `EquipmentSlot` had a `keyProperty=name`, the `name`
// is used to access them
player.equipmentSlot.head;
player.equipmentSlot.rightHand;

// this will `destroy` the `sword` entity and automatically
// set the `rightHand.item` property to `null`
player.equipmentSlot.rightHand.item.destroy();

// remove and destroy the `rightHand` equipment slot
player.equipmentSlot.rightHand.destroy();

const query = world.createQuery({
    any: [A, B], // exclude any entity that does not have at least one of A OR B.
    all: [C, D], // exclude entities that don't have both C AND D
    none: [E, F], // exclude entities that have E OR F
});

query.get().forEach((entity) => ...); // loop over the latest set (array) of entites that match

// alternatively, listen for when an individual entity is created/updated that matches
query.onEntityAdded((entity) => {
    console.log('an entity was updated or created that matches the query!', entity);
});

query.onEntityRemoved((entity) => {
    console.log('an entity was updated or destroyed that previously matched the query!', entity);
});

const query = world.createQuery({
    all: [A, B],
    immutableResult: false, // defaults to TRUE
});

const results = query.get();

results.splice(0, 1); // DANGER! do not modify results if immutableResult is false!

const saveGame = () => {
    const data = world.serialize();
    localStorage.setItem('savegame', data);
};

...

const loadGame = () => {
    const data = localStorage.getItem('savegame');
    world.deserialize(data);
};

// a `Health` component which listens for a `take damage` event
class Health extends Component {
    ...
    // event names are mapped to methods using the `camelcase` library.
    onTakeDamage(evt) {
        console.log(evt);
        this.value -= evt.data.amount;

        // the event gets passed to all components the `entity` unless a component
        // invokes `evt.prevent()` or `evt.handle()`
        evt.handle();
    }

    // watch ALL events coming to component
    onEvent(evt) {
        console.log(evt.name);
        console.log(evt.is('take-damage'));
    }
}

...

entity.add(Health);

const evt = entity.fireEvent('take-damage', { amount: 12 });

console.log(evt.name); // return the name of the event. "take-damage"
console.log(evt.data); // return the arbitrary data object attached. { amount: 12 }
console.log(evt.handled); // was `handle()` called?
console.log(evt.prevented);  // was `prevent()` or `handle()` called?
console.log(evt.handle()); // handle and prevent the event from continuing
console.log(evt.prevent()); // prevent the event from continuing without marking `handled`
console.log(evt.is('take-damage')); // simple name check

// prefabs must be registered before they can be instantiated
engine.registerPrefab({
    name: 'Being',
    components: [
        {
            type: 'Position',
            properties: {
                x: 4,
                y: 10,
            },
        },
        {
            type: 'Material',
            properties: {
                name: 'flesh',
            },
        },
    ],
});

ecs.registerPrefab({
    // name used when creating the prefab
    name: 'HumanWarrior',
    // an array of other prefabs of which this one derives. Note they must be registered in order.
    inherit: ['Being', 'Warrior'],
    // an array of components to attach
    components: [
        {
            // this should be a component constructor name
            type: 'EquipmentSlot',
            // what properties should be assigned to the component
            properties: {
                name: 'head',
            },
        },
        {
            // components that allow multiple can easily be added in
            type: 'EquipmentSlot',
            properties: {
                name: 'legs',
            },
        },
        {
            type: 'Material',
            // if a parent prefab already defines a `Material` component, this flag
            // will say how to treat it. Defaults to overwrite=true
            overwrite: true,
            properties: {
                name: 'silver',
            },
        },
    ],
});

...

const warrior1 = world.createPrefab('HumanWarrior');

// property overrides can be provided as the second argument
const warrior2 = world.createPrefab('HumanWarrior', {
    equipmentSlot: {
        head: {
            itemId: world.createPrefab('Helmet').id
        },
    },
    position: {
        x: 12,
        y: 24,
    },
});