import React from 'react';
import { connect } from 'react-redux';
import { assign, pick } from 'lodash';
import { Map as makeMap } from 'immutable';

import { event as d3Event, select } from 'd3-selection';
import { zoom, zoomIdentity } from 'd3-zoom';

import { shownNodesSelector } from '../selectors/node-filters';
import { clickBackground } from '../actions/app-actions';
import Logo from '../components/logo';
import NodesChartElements from './nodes-chart-elements';
import { getActiveTopologyOptions, zoomCacheKey } from '../utils/topology-utils';

import { topologyZoomState } from '../selectors/nodes-chart-zoom';
import { layoutWithSelectedNode } from '../selectors/nodes-chart-focus';
import { graphLayout } from '../selectors/nodes-chart-layout';


const GRAPH_COMPLEXITY_NODES_TRESHOLD = 100;
const ZOOM_CACHE_FIELDS = [
  'panTranslateX', 'panTranslateY',
  'zoomScale', 'minZoomScale', 'maxZoomScale'
];


class NodesChart extends React.Component {
  constructor(props, context) {
    super(props, context);

    this.state = {
      layoutNodes: makeMap(),
      layoutEdges: makeMap(),
      zoomScale: 0,
      minZoomScale: 0,
      maxZoomScale: 0,
      panTranslateX: 0,
      panTranslateY: 0,
      selectedScale: 1,
      height: props.height || 0,
      width: props.width || 0,
      // TODO: Move zoomCache to global Redux state. Now that we store
      // it here, it gets reset every time the component gets destroyed.
      // That happens e.g. when we switch to a grid mode in one topology,
      // which resets the zoom cache across all topologies, which is bad.
      zoomCache: {},
    };

    this.handleMouseClick = this.handleMouseClick.bind(this);
    this.zoomed = this.zoomed.bind(this);
  }

  componentWillMount() {
    this.setState(graphLayout(this.state, this.props));
  }

  componentDidMount() {
    // distinguish pan/zoom from click
    this.isZooming = false;
    this.zoom = zoom().on('zoom', this.zoomed);

    this.svg = select('.nodes-chart svg');
    this.svg.call(this.zoom);
  }

  componentWillUnmount() {
    // undoing .call(zoom)
    this.svg
      .on('mousedown.zoom', null)
      .on('onwheel', null)
      .on('onmousewheel', null)
      .on('dblclick.zoom', null)
      .on('touchstart.zoom', null);
  }

  componentWillReceiveProps(nextProps) {
    // Don't modify the original state, as we only want to call setState once at the end.
    const state = assign({}, this.state);

    // Reset layout dimensions only when forced (to prevent excessive rendering on resizing).
    state.height = nextProps.forceRelayout ? nextProps.height : (state.height || nextProps.height);
    state.width = nextProps.forceRelayout ? nextProps.width : (state.width || nextProps.width);

    // Update the state with memoized graph layout information based on props nodes and edges.
    assign(state, graphLayout(state, nextProps));

    // Now that we have the graph layout information, we use it to create a default zoom
    // settings for the current topology if we are rendering its layout for the first time, or
    // otherwise we use the cached zoom information from local state for this topology layout.
    assign(state, topologyZoomState(state, nextProps));

    // Finally we update the layout state with the circular
    // subgraph centered around the selected node (if there is one).
    if (nextProps.selectedNodeId) {
      assign(state, layoutWithSelectedNode(state, nextProps));
    }

    this.applyZoomState(state);
    this.setState(state);
  }

  render() {
    // Not passing transform into child components for perf reasons.
    const { panTranslateX, panTranslateY, zoomScale } = this.state;
    const transform = `translate(${panTranslateX}, ${panTranslateY}) scale(${zoomScale})`;

    const svgClassNames = this.props.isEmpty ? 'hide' : '';
    const isAnimated = !this.isTopologyGraphComplex();

    return (
      <div className="nodes-chart">
        <svg
          width="100%" height="100%" id="nodes-chart-canvas"
          className={svgClassNames} onClick={this.handleMouseClick}>
          <g transform="translate(24,24) scale(0.25)">
            <Logo />
          </g>
          <NodesChartElements
            layoutNodes={this.state.layoutNodes}
            layoutEdges={this.state.layoutEdges}
            selectedScale={this.state.selectedScale}
            transform={transform}
            isAnimated={isAnimated} />
        </svg>
      </div>
    );
  }

  handleMouseClick() {
    if (!this.isZooming || this.props.selectedNodeId) {
      this.props.clickBackground();
    } else {
      this.isZooming = false;
    }
  }

  isTopologyGraphComplex() {
    return this.state.layoutNodes.size > GRAPH_COMPLEXITY_NODES_TRESHOLD;
  }

  cacheZoomState(state) {
    const zoomState = pick(state, ZOOM_CACHE_FIELDS);
    const zoomCache = assign({}, state.zoomCache);
    zoomCache[zoomCacheKey(this.props)] = zoomState;
    return { zoomCache };
  }

  applyZoomState({ zoomScale, minZoomScale, maxZoomScale, panTranslateX, panTranslateY }) {
    this.zoom = this.zoom.scaleExtent([minZoomScale, maxZoomScale]);
    this.svg.call(this.zoom.transform, zoomIdentity
      .translate(panTranslateX, panTranslateY)
      .scale(zoomScale));
  }

  zoomed() {
    this.isZooming = true;
    // don't pan while node is selected
    if (!this.props.selectedNodeId) {
      let state = assign({}, this.state, {
        panTranslateX: d3Event.transform.x,
        panTranslateY: d3Event.transform.y,
        zoomScale: d3Event.transform.k
      });
      // Cache the zoom state as soon as it changes as it is cheap, and makes us
      // be able to skip difficult conditions on when this caching should happen.
      state = assign(state, this.cacheZoomState(state));
      this.setState(state);
    }
  }
}


function mapStateToProps(state) {
  return {
    nodes: shownNodesSelector(state),
    forceRelayout: state.get('forceRelayout'),
    selectedNodeId: state.get('selectedNodeId'),
    topologyId: state.get('currentTopologyId'),
    topologyOptions: getActiveTopologyOptions(state),
  };
}


export default connect(
  mapStateToProps,
  { clickBackground }
)(NodesChart);