import * as I from 'immutable';
import immutablediff from 'immutablediff';

import {compose} from '@avocado/core';
import {Trait} from '@avocado/entity';
import {Rectangle, Vector} from '@avocado/math';
import {
  Packer,
  StateKeysPacket,
  StatePacket,
  Synchronizer,
} from '@avocado/state';

const decorate = compose(
);

export class Informed extends decorate(Trait) {

  initialize() {
    this._packer = new Packer();
    this._rememberedEntities = {};
    this._socket = undefined;
    this._state = I.Map();
  }

  destroy() {
    if (this._socket) {
      delete this._socket.entity;
      delete this._socket;
    }
    this._rememberedEntities = {};
    this._state = this._state.clear();
  }

  get areaToInform() {
    // Reduce entity list to visible.
    const room = this.entity.room;
    const camera = this.entity.camera;
    // Blow up camera rectangle to compensate for camera desync.
    const size = Rectangle.size(camera.rectangle);
    return Rectangle.expand(
      camera.rectangle,
      Vector.scale(size, 0.5),
    );
  }

  entityOverrides(path, fn) {
    const pathOverrides = [
      ['physical', 'state', 'addedToPhysics'],
      ['visible', 'state', 'isVisible'],
      // Ticking change last.
      ['existent', 'state', 'isTicking'],
    ]
    return I.List().withMutations((steps) => {
      for (const pathOverride of pathOverrides) {
        steps.push(I.Map({
          op: 'replace',
          path: path + '/' + pathOverride.join('/'),
          value: fn(pathOverride),
        }));
      }
    });
  }

  entityStepFilter(op) {
    return (step) => {
      if (op !== step.get('op')) {
        return false;
      }
      const parts = step.get('parts');
      if (!parts) {
        return false;
      }
      if (6 !== parts.length) {
        return false;
      }
      if ('room' !== parts[1]) {
        return false;
      }
      if ('layers' !== parts[2]) {
        return false;
      }
      if ('entityList' !== parts[4]) {
        return false;
      }
      return true;
    };
  }

  rewriteEntityAdds(state, steps) {
    steps = steps.map((step) => {
      return step.set('parts', step.get('path').split('/'));
    });
    const isAdd = this.entityStepFilter('add');
    const adds = steps.filter(isAdd);
    steps = steps.withMutations((steps) => {
      const iterator = adds.values();
      for (const add of iterator) {
        // Remember the entity.
        const parts = add.get('parts');
        const layerId = parts[3];
        const uuid = parts[5];
        if (!(uuid in this._rememberedEntities)) {
          continue;
        }
        const rememberedEntity = this._rememberedEntities[uuid];
        // Take a diff from what the client remembers to now.
        const currentState = state.getIn(
          ['room', 'layers', layerId, 'entityList', uuid]
        );
        const addSteps = immutablediff(rememberedEntity, currentState);
        // Translate step paths to full state location.
        const fullAddSteps = addSteps.map((addStep) => {
          return addStep.set('path', add.get('path') + addStep.get('path'));
        });
        for (let i = 0; i < fullAddSteps.size; ++i) {
          steps.push(fullAddSteps.get(i));
        }
        // Add overrides.
        const overrides = this.entityOverrides(
          add.get('path'),
          (path) => rememberedEntity.getIn(path),
        );
        for (let i = 0; i < overrides.size; ++i) {
          steps.push(overrides.get(i));
        }
      }
    });
    // Filter adds for remembered entities.
    steps = steps.filter((step) => {
      if (!isAdd(step)) {
        return true;
      }
      const parts = step.get('parts');
      const uuid = parts[5];
      return !(uuid in this._rememberedEntities);
    });
    // Forget all remembered entities.
    adds.forEach((step) => {
      const parts = step.get('parts');
      const uuid = parts[5];
      delete this._rememberedEntities[uuid];
    });
    return steps;
  }

  rewriteEntityRemovals(state, steps) {
    steps = steps.map((step) => {
      return step.set('parts', step.get('path').split('/'));
    });
    const isRemove = this.entityStepFilter('remove');
    const removals = steps.filter(isRemove);
    steps = steps.withMutations((steps) => {
      for (const removal of removals.values()) {
        // Remember the entity.
        const parts = removal.get('parts');
        const layerId = parts[3];
        const uuid = parts[5];
        const remembered = state.getIn(
          ['room', 'layers', layerId, 'entityList', uuid]
        );
        // Actually destroyed?
        if (!remembered) {
          return;
        }
        this._rememberedEntities[uuid] = remembered;
        // Add overrides.
        const overrides = this.entityOverrides(
          removal.get('path'),
          () => false
        );
        for (let i = 0; i < overrides.size; ++i) {
          steps.push(overrides.get(i));
        }
      }
    });
    // Remove all removes.
    return steps.filter((step) => {
      if (!isRemove(step)) {
        return true;
      }
      const parts = step.get('parts');
      const uuid = parts[5];
      return !(uuid in this._rememberedEntities);
    });
  }

  reduceState(state) {
    // Set client's self entity.
    state = state.set('selfEntity', this.entity.instanceUuid);
    const areaToInform = this.entity.areaToInform;
    const room = this.entity.room;
    // Write over entity list for every layer.
    for (const {index, layer} of room.layers) {
      const visibleEntities = layer.visibleEntities(areaToInform);
      const reduceEntityListRaw = {};
      for (let i = 0; i < visibleEntities.length; ++i) {
        const entity = visibleEntities[i];
        reduceEntityListRaw[entity.instanceUuid] = entity.state;
      }
      let reducedEntityList = I.Map(reduceEntityListRaw);
      const entityListPath = ['room', 'layers', index, 'entityList'];
      state = state.setIn(entityListPath, reducedEntityList);
    }
    return state;
  }

  get socket() {
    return this._socket;
  }

  set socket(socket) {
    socket.entity = this.entity;
    this._socket = socket;
  }

  methods() {
    return {

      inform: (state) => {
        if (!this._socket) {
          return;
        }
        // Reduce state.
        const reducedState = this.reduceState(state);
        // Take a pure JS diff.
        let steps = immutablediff(this._state, reducedState);
        if (0 === steps.size) {
          this._state = reducedState;
          return;
        }
        // Rewrite entity adds/removals.
        steps = this.rewriteEntityAdds(state, steps);
        steps = this.rewriteEntityRemovals(state, steps);
        // Remember state.
        this._state = reducedState;
        // Emit!
        const keys = this._packer.computeNewKeys(steps);
        if (0 !== keys[0].length) {
          this._socket.send(new StateKeysPacket(keys));
        }
        const packed = this._packer.pack(steps);
        this._socket.send(new StatePacket(packed));
      },

      seesEntity: (entity) => {
        const areaToInform = this.entity.areaToInform;
        const room = this.entity.room;
        const visibleEntities = room.visibleEntities(areaToInform);
        return -1 !== visibleEntities.indexOf(entity);
      }

    };
  }

}