import {
  TPS,
} from '@/constants.js';
import Ecs from '@/ecs/ecs.js';
import Components from '@/ecs-components/index.js';
import Systems from '@/ecs-systems/index.js';
import {decode, encode} from '@/packets/index.js';
import Script from '@/util/script.js';

function join(...parts) {
  return parts.join('/');
}

export default class Engine {

  incomingActions = [];

  connections = [];

  connectedPlayers = new Map();

  ecses = {};

  frame = 0;

  handle;

  last = Date.now();

  server;

  constructor(Server) {
    this.ecses = {};
    class SilphiusServer extends Server {
      accept(connection, packed) {
        super.accept(connection, decode(packed));
      }
      transmit(connection, packet) {
        super.transmit(connection, encode(packet));
      }
    }
    this.server = new SilphiusServer();
    this.server.addPacketListener('Action', (connection, payload) => {
      this.incomingActions.push([this.connectedPlayers.get(connection).entity, payload]);
    });
  }

  async connectPlayer(connection, id) {
    const entityJson = await this.loadPlayer(id);
    if (!this.ecses[entityJson.Ecs.path]) {
      await this.loadEcs(entityJson.Ecs.path);
    }
    const ecs = this.ecses[entityJson.Ecs.path];
    const entity = ecs.create(entityJson);
    this.connections.push(connection);
    this.connectedPlayers.set(
      connection,
      {
        entity: ecs.get(entity),
        id,
        memory: new Set(),
      },
    );
  }

  createEcs() {
    return new Ecs({Components, Systems});
  }

  async createHomestead(id) {
    const ecs = this.createEcs();
    const area = {x: 100, y: 60};
    ecs.create({
      AreaSize: {x: area.x * 16, y: area.y * 16},
      TileLayers: {
        layers: [
          {
            area,
            data: Array(area.x * area.y).fill(0).map(() => 1 + Math.floor(Math.random() * 4)),
            source: '/assets/tileset.json',
            tileSize: {x: 16, y: 16},
          }
        ],
      },
    });
    const defaultSystems = [
      'ApplyControlMovement',
      'ApplyMomentum',
      'ClampPositions',
      'FollowCamera',
      'CalculateAabbs',
      'UpdateSpatialHash',
      'ControlDirection',
      'SpriteDirection',
      'RunAnimations',
      'RunTickingPromises',
    ];
    defaultSystems.forEach((defaultSystem) => {
      const System = ecs.system(defaultSystem);
      if (System) {
        System.active = true;
      }
    });
    this.saveEcs(join('homesteads', `${id}`), ecs);
  }

  async createPlayer(id) {
    const player = {
      Camera: {},
      Controlled: {},
      Direction: {direction: 2},
      Ecs: {path: join('homesteads', `${id}`)},
      Momentum: {},
      Inventory: {
        slots: {
          1: {
            qty: 10,
            source: '/assets/potion',
          },
        },
      },
      Health: {health: 100},
      Position: {x: 368, y: 368},
      VisibleAabb: {},
      Speed: {speed: 100},
      Sprite: {
        anchor: {x: 0.5, y: 0.8},
        animation: 'moving:down',
        frame: 0,
        frames: 8,
        source: '/assets/dude.json',
        speed: 0.115,
      },
      Ticking: {},
      Wielder: {
        activeSlot: 0,
      },
    };
    const buffer = (new TextEncoder()).encode(JSON.stringify(player));
    await this.server.writeData(
      join('players', `${id}`),
      buffer,
    );
    return buffer;
  }

  async disconnectPlayer(connection) {
    const {entity, id} = this.connectedPlayers.get(connection);
    const ecs = this.ecses[entity.Ecs.path];
    await this.savePlayer(id, entity);
    ecs.destroy(entity.id);
    this.connectedPlayers.delete(connection);
    this.connections.splice(this.connections.indexOf(connection), 1);
  }

  async load() {
  }

  async loadEcs(path) {
    this.ecses[path] = Ecs.deserialize(
      this.createEcs(),
      await this.server.readData(path),
    );
  }

  async loadPlayer(id) {
    let buffer;
    try {
      buffer = await this.server.readData(['players', `${id}`].join('/'))
    }
    catch (error) {
      if ('ENOENT' !== error.code) {
        throw error;
      }
      await this.createHomestead(id);
      buffer = await this.createPlayer(id);
    }
    return JSON.parse((new TextDecoder()).decode(buffer));
  }

  async saveEcs(path, ecs) {
    const view = Ecs.serialize(ecs);
    await this.server.writeData(path, view);
  }

  async saveEcses() {
    const promises = []
    for (const i in this.ecses) {
      promises.push(this.saveEcs(i, this.ecses[i]));
    }
    await Promise.all(promises);
  }

  async savePlayer(id, entity) {
    const encoder = new TextEncoder();
    const buffer = encoder.encode(JSON.stringify(entity.toJSON()));
    await this.server.writeData(['players', `${id}`].join('/'), buffer);
  }

  start() {
    this.handle = setInterval(() => {
      const elapsed = (Date.now() - this.last) / 1000;
      this.last = Date.now();
      this.tick(elapsed);
      this.update(elapsed);
      this.frame += 1;
    }, 1000 / TPS);
  }

  stop() {
    clearInterval(this.handle);
    this.handle = undefined;
  }

  tick(elapsed) {
    for (const i in this.ecses) {
      this.ecses[i].setClean();
    }
    for (const [
      entity,
      payload,
    ] of this.incomingActions) {
      const {Controlled, Inventory, Ticking, Wielder} = entity;
      switch (payload.type) {
        case 'changeSlot': {
          Wielder.activeSlot = payload.value - 1;
          break;
        }
        case 'moveUp':
        case 'moveRight':
        case 'moveDown':
        case 'moveLeft': {
          Controlled[payload.type] = payload.value;
          break;
        }
        case 'use': {
          if (payload.value) {
            const item = Inventory.item(Wielder.activeSlot + 1);
            this.server.readAsset(item.source + '/start.js')
              .then((response) => response.text())
              .then((code) => {
                Ticking.addTickingPromise(
                  Script.tickingPromise(code, {item, wielder: entity}),
                );
              });
          }
        }
      }
    }
    this.incomingActions = [];
    for (const i in this.ecses) {
      this.ecses[i].tick(elapsed);
    }
  }

  update(elapsed) {
    for (const connection of this.connections) {
      this.server.send(
        connection,
        {
          type: 'Tick',
          payload: {
            ecs: this.updateFor(connection),
            elapsed,
            frame: this.frame,
          },
        },
      );
    }
  }

  updateFor(connection) {
    const update = {};
    const {entity, memory} = this.connectedPlayers.get(connection);
    const mainEntityId = entity.id;
    const ecs = this.ecses[entity.Ecs.path];
    const nearby = ecs.system('UpdateSpatialHash').nearby(entity);
    // Master entity.
    nearby.add(ecs.get(1));
    const lastMemory = new Set(memory.values());
    for (const entity of nearby) {
      const {id} = entity;
      lastMemory.delete(id);
      if (!memory.has(id)) {
        update[id] = entity.toJSON();
        if (mainEntityId === id) {
          update[id].MainEntity = {};
        }
      }
      else if (ecs.diff[id]) {
        update[id] = ecs.diff[id];
      }
      memory.add(id);
    }
    for (const id of lastMemory) {
      memory.delete(id);
      update[id] = false;
    }
    return update;
  }

}