FeedView.js

/**
 * @providesModule FeedView
 */
'use strict';

var ListViewDataSource = require('ListViewDataSource');
var React = require('react-native');
var RCTScrollViewManager = require('NativeModules').ScrollViewManager;
var ScrollView = require('ScrollView');
var ScrollResponder = require('ScrollResponder');
var StaticRenderer = require('StaticRenderer');
var TimerMixin = require('react-timer-mixin');
var View = require('View');
var InteractionManager = require('InteractionManager');
InteractionManager.setDeadline(100);

var isEmpty = require('isEmpty');
var logError = require('logError');
var merge = require('merge');

var PropTypes = React.PropTypes;

var DEFAULT_PAGE_SIZE = 1;
var DEFAULT_INITIAL_ROWS = 6;
var DEFAULT_SCROLL_RENDER_AHEAD = 1000;
var DEFAULT_END_REACHED_THRESHOLD = 1000;
var DEFAULT_SCROLL_CALLBACK_THROTTLE = 50;
var SCROLLVIEW_REF = 'listviewscroll';

const DEBUG = false;

var FeedView = React.createClass({
  mixins: [ScrollResponder.Mixin, TimerMixin],

  statics: {
    DataSource: ListViewDataSource,
  },

  /**
   * You must provide a renderRow function. If you omit any of the other render
   * functions, ListView will simply skip rendering them.
   *
   * - renderRow(rowData, sectionID, rowID, highlightRow);
   * - renderSectionHeader(sectionData, sectionID);
   */
  propTypes: {
    ...ScrollView.propTypes,

    dataSource: PropTypes.instanceOf(ListViewDataSource).isRequired,
    /**
     * (sectionID, rowID, adjacentRowHighlighted) => renderable
     *
     * If provided, a renderable component to be rendered as the separator
     * below each row but not the last row if there is a section header below.
     * Take a sectionID and rowID of the row above and whether its adjacent row
     * is highlighted.
     */
    renderSeparator: PropTypes.func,
    /**
     * (rowData, sectionID, rowID, highlightRow) => renderable
     *
     * Takes a data entry from the data source and its ids and should return
     * a renderable component to be rendered as the row.  By default the data
     * is exactly what was put into the data source, but it's also possible to
     * provide custom extractors. ListView can be notified when a row is
     * being highlighted by calling highlightRow function. The separators above and
     * below will be hidden when a row is highlighted. The highlighted state of
     * a row can be reset by calling highlightRow(null).
     */
    renderRow: PropTypes.func.isRequired,
    /**
     * Called when all rows have been rendered and the list has been scrolled
     * to within onEndReachedThreshold of the bottom.  The native scroll
     * event is provided.
     */
    onEndReached: PropTypes.func,
    /**
     * Threshold in pixels for onEndReached.
     */
    onEndReachedThreshold: PropTypes.number,
    /**
     * Number of rows to render per event loop.
     */
    pageSize: PropTypes.number,
    /**
     * () => renderable
     *
     * The header and footer are always rendered (if these props are provided)
     * on every render pass.  If they are expensive to re-render, wrap them
     * in StaticContainer or other mechanism as appropriate.  Footer is always
     * at the bottom of the list, and header at the top, on every render pass.
     */
    renderFooter: PropTypes.func,
    renderHeader: PropTypes.func,
    /**
     * (sectionData, sectionID) => renderable
     *
     * If provided, a sticky header is rendered for this section.  The sticky
     * behavior means that it will scroll with the content at the top of the
     * section until it reaches the top of the screen, at which point it will
     * stick to the top until it is pushed off the screen by the next section
     * header.
     */
    renderSectionHeader: PropTypes.func,
    /**
     * (props) => renderable
     *
     * A function that returns the scrollable component in which the list rows
     * are rendered. Defaults to returning a ScrollView with the given props.
     */
    renderScrollComponent: React.PropTypes.func.isRequired,
    /**
     * How early to start rendering rows before they come on screen, in
     * pixels.
     */
    scrollRenderAheadDistance: React.PropTypes.number,
    /**
     * (visibleRows, changedRows) => void
     *
     * Called when the set of visible rows changes.  `visibleRows` maps
     * { sectionID: { rowID: true }} for all the visible rows, and
     * `changedRows` maps { sectionID: { rowID: true | false }} for the rows
     * that have changed their visibility, with true indicating visible, and
     * false indicating the view has moved out of view.
     */
    onChangeVisibleRows: React.PropTypes.func,
    /**
     * A performance optimization for improving scroll perf of
     * large lists, used in conjunction with overflow: 'hidden' on the row
     * containers.  This is enabled by default.
     */
    removeClippedSubviews: React.PropTypes.bool,
    /**
     * An array of child indices determining which children get docked to the
     * top of the screen when scrolling. For example, passing
     * `stickyHeaderIndices={[0]}` will cause the first child to be fixed to the
     * top of the scroll view. This property is not supported in conjunction
     * with `horizontal={true}`.
     * @platform ios
     */
    stickyHeaderIndices: PropTypes.arrayOf(PropTypes.number),
    /**
     * How many rows to render synchronously on initial component mount.  Use
     * this to make it so that the first screen worth of data appears more quickly
     * than it would to render the full pageSize
     */
    initialListSize: PropTypes.number,
  },

  /**
   * Exports some data, e.g. for perf investigations or analytics.
   */
  getMetrics: function() {
    return {
      contentLength: this.scrollProperties.contentLength,
      totalRows: this.props.dataSource.getRowCount(),
      renderedRows: this.state.curRenderedRowsCount,
      visibleRows: Object.keys(this._visibleRows).length,
    };
  },

  /**
   * Provides a handle to the underlying scroll responder to support operations
   * such as scrollTo.
   */
  getScrollResponder: function() {
    return this.refs[SCROLLVIEW_REF] &&
      this.refs[SCROLLVIEW_REF].getScrollResponder &&
      this.refs[SCROLLVIEW_REF].getScrollResponder();
  },

  scrollTo: function(destY, destX) {
    this.getScrollResponder().scrollResponderScrollTo(destX || 0, destY || 0);
  },

  setNativeProps: function(props) {
    this.refs[SCROLLVIEW_REF].setNativeProps(props);
  },

  /**
   * React life cycle hooks.
   */

  getDefaultProps: function() {
    return {
      initialListSize: DEFAULT_INITIAL_ROWS,
      pageSize: DEFAULT_PAGE_SIZE,
      renderScrollComponent: props => <ScrollView {...props} />,
      scrollRenderAheadDistance: DEFAULT_SCROLL_RENDER_AHEAD,
      onEndReachedThreshold: DEFAULT_END_REACHED_THRESHOLD,
      stickyHeaderIndices: [],
    };
  },

  getInitialState: function() {
    return {
      curRenderedRowsCount: 0,
      updateBatchId: 0,
      highlightedRow: {},
    };
  },

  getInnerViewNode: function() {
    return this.refs[SCROLLVIEW_REF].getInnerViewNode();
  },

  componentWillMount: function() {
    // this data should never trigger a render pass, so don't put in state
    this.scrollProperties = {
      visibleLength: null,
      contentLength: null,
      offset: 0
    };
    this._childFrames = [];
    this._visibleRows = {};
    this._prevRenderedRowsCount = 0;
    this._sentEndForContentLength = null;
    this._updateBatches = {};
    this._rowRefs = {};
    this._separatorRefs = {};
    this._pageInNewRows(this.props);
  },

  componentDidMount: function() {
    // do this in animation frame until componentDidMount actually runs after
    // the component is laid out
    this.requestAnimationFrame(() => {
      this._measureAndUpdateScrollProps();
    });
  },

  componentWillReceiveProps: function(nextProps) {
    if (this.props.dataSource !== nextProps.dataSource) {
      this._resetRowCount = true;
      this._pageInNewRows(nextProps);
    }
  },

  componentDidUpdate: function() {
    this.requestAnimationFrame(() => {
      this._measureAndUpdateScrollProps();
    });
  },

  onRowHighlighted: function(sectionID, rowID) {
    this.setState({highlightedRow: {sectionID, rowID}});
  },

  render: function() {
    DEBUG && console.log({
      curRenderedRowsCount: this.state.curRenderedRowsCount
    })

    var bodyComponents = [];

    var dataSource = this.props.dataSource;
    var allRowIDs = dataSource.rowIdentities;
    var rowCount = 0;
    var sectionHeaderIndices = [];

    var header = this.props.renderHeader && this.props.renderHeader();
    var footer = this.props.renderFooter && this.props.renderFooter();
    var totalIndex = header ? 1 : 0;

    for (var sectionIdx = 0; sectionIdx < allRowIDs.length; sectionIdx++) {
      var sectionID = dataSource.sectionIdentities[sectionIdx];
      var rowIDs = allRowIDs[sectionIdx];

      if (rowIDs.length === 0) {
        continue;
      }

      if (this.props.renderSectionHeader) {
        var shouldUpdateHeader = rowCount >= this._prevRenderedRowsCount &&
          dataSource.sectionHeaderShouldUpdate(sectionIdx);
        bodyComponents.push(
          <StaticRenderer
            key={'s_' + sectionID}
            shouldUpdate={!!shouldUpdateHeader}
            render={this.props.renderSectionHeader.bind(
              null,
              dataSource.getSectionHeaderData(sectionIdx),
              sectionID
            )}
          />
        );
        sectionHeaderIndices.push(totalIndex++);
      }

      for (var rowIdx = 0; rowIdx < rowIDs.length; rowIdx++) {
        var rowID = rowIDs[rowIdx];
        var comboID = sectionID + '_' + rowID;

        var shouldUpdateRow = rowCount >= this._prevRenderedRowsCount &&
          dataSource.rowShouldUpdate(sectionIdx, rowIdx);
        var key = 'r_' + comboID;

        var row =
          <StaticRenderer
            key={key}
            shouldUpdate={!!shouldUpdateRow}
            render={this._renderRow.bind(
              this,
              key,
              this.state.updateBatchId,
              dataSource.getRowData(sectionIdx, rowIdx),
              sectionID,
              rowID,
              this.onRowHighlighted
            )}
          />;
        bodyComponents.push(row);
        totalIndex++;

        if (this.props.renderSeparator &&
            (rowIdx !== rowIDs.length - 1 || sectionIdx === allRowIDs.length - 1)) {
          var adjacentRowHighlighted =
            this.state.highlightedRow.sectionID === sectionID && (
              this.state.highlightedRow.rowID === rowID ||
              this.state.highlightedRow.rowID === rowIDs[rowIdx + 1]
            );
          var separator = this._renderSeparator(
            this.state.updateBatchId,
            sectionID,
            rowID,
            adjacentRowHighlighted
          );
          bodyComponents.push(separator);
          totalIndex++;
        }
        if (++rowCount === this.state.curRenderedRowsCount) {
          break;
        }
      }
      if (rowCount >= this.state.curRenderedRowsCount) {
        break;
      }
    }

    var {
      renderScrollComponent,
      ...props,
    } = this.props;
    if (!props.scrollEventThrottle) {
      props.scrollEventThrottle = DEFAULT_SCROLL_CALLBACK_THROTTLE;
    }
    if (props.removeClippedSubviews === undefined) {
      props.removeClippedSubviews = true;
    }
    Object.assign(props, {
      onScroll: this._onScroll,
      stickyHeaderIndices: this.props.stickyHeaderIndices.concat(sectionHeaderIndices),

      // Do not pass these events downstream to ScrollView since they will be
      // registered in ListView's own ScrollResponder.Mixin
      onKeyboardWillShow: undefined,
      onKeyboardWillHide: undefined,
      onKeyboardDidShow: undefined,
      onKeyboardDidHide: undefined,
    });

    // TODO(ide): Use function refs so we can compose with the scroll
    // component's original ref instead of clobbering it
    return React.cloneElement(renderScrollComponent(props), {
      ref: SCROLLVIEW_REF,
      onContentSizeChange: this._onContentSizeChange,
      onLayout: this._onLayout,
    }, header, bodyComponents, footer);
  },

  _renderSeparator(updateBatchId, sectionID, rowID, adjacentRowHighlighted) {
    DEBUG && console.log({rowID, separator: true});

    return (
      <IncrementalSeparatorRenderer
        key={'sp_' + rowID}
        ref={view => { this._separatorRefs[rowID] = view; }}
        synchronous={!this._hasRenderedInitialListSize}
        isBatchComplete={this._isUpdatedBatchComplete(updateBatchId)}
        render={this.props.renderSeparator.bind(null, sectionID, rowID, adjacentRowHighlighted)}
      />
    );
  },

  _renderRow(key, updateBatchId, rowData, sectionID, rowID, onRowHighlighted) {
    DEBUG && console.log({rowID});

    return (
      <IncrementalRowRenderer
        isBatchComplete={this._isUpdatedBatchComplete(updateBatchId)}
        onRender={() => { this._onRenderRowInBatch(updateBatchId) }}
        rowID={rowID}
        synchronous={!this._hasRenderedInitialListSize}
        ref={view => { this._rowRefs[rowID] = view; }}
        render={this.props.renderRow.bind(null, rowData, sectionID, rowID, onRowHighlighted)}
      />
    );
  },

  _isUpdatedBatchComplete(updateBatchId) {
    if (!this._updateBatches[updateBatchId]) {
      return true;
    }

    return (
      this._updateBatches[updateBatchId].complete ===
      this._updateBatches[updateBatchId].rows
    );
  },

  _onRenderRowInBatch(updateBatchId) {
    if (!this._updateBatches[updateBatchId]) {
      return;
    }

    this._updateBatches[updateBatchId].complete += 1;
    DEBUG && console.log({updateBatchId, complete: this._updateBatches[updateBatchId].complete});

    if (this._isUpdatedBatchComplete(updateBatchId)) {
      DEBUG && console.log({finished: updateBatchId});

      this._presentBatch(updateBatchId);
      this.props.onPresentBatch && this.props.onPresentBatch();
    }
  },

  _presentBatch(updateBatchId) {
    let {
      rows,
      firstRow,
    } = this._updateBatches[updateBatchId];

    for (var i = firstRow; i <= firstRow + rows; i++) {
      this._rowRefs[i] && this._rowRefs[i].batchIsComplete();
      this._separatorRefs[i] && this._separatorRefs[i].batchIsComplete();
    }
  },

  /**
   * Private methods
   */

  _measureAndUpdateScrollProps: function() {
    var scrollComponent = this.getScrollResponder();
    if (!scrollComponent || !scrollComponent.getInnerViewNode) {
      return;
    }

    // RCTScrollViewManager.calculateChildFrames is not available on
    // every platform
    RCTScrollViewManager && RCTScrollViewManager.calculateChildFrames &&
      RCTScrollViewManager.calculateChildFrames(
        React.findNodeHandle(scrollComponent),
        this._updateVisibleRows,
      );
  },

  _onContentSizeChange: function(width, height) {
    var contentLength = !this.props.horizontal ? height : width;
    if (contentLength !== this.scrollProperties.contentLength) {
      this.scrollProperties.contentLength = contentLength;
      this._updateVisibleRows();
      this._renderMoreRowsIfNeeded();
    }
    this.props.onContentSizeChange && this.props.onContentSizeChange(width, height);
  },

  _onLayout: function(event) {
    var {width, height} = event.nativeEvent.layout;
    var visibleLength = !this.props.horizontal ? height : width;
    if (visibleLength !== this.scrollProperties.visibleLength) {
      this.scrollProperties.visibleLength = visibleLength;
      this._updateVisibleRows();
      this._renderMoreRowsIfNeeded();
    }
    this.props.onLayout && this.props.onLayout(event);
  },

  _maybeCallOnEndReached: function(event) {
    if (this.props.onEndReached &&
        this.scrollProperties.contentLength !== this._sentEndForContentLength &&
        this._getDistanceFromEnd(this.scrollProperties) < this.props.onEndReachedThreshold &&
        this.state.curRenderedRowsCount === this.props.dataSource.getRowCount()) {
      this._sentEndForContentLength = this.scrollProperties.contentLength;
      this.props.onEndReached(event);
      return true;
    }
    return false;
  },

  _renderMoreRowsIfNeeded: function() {
    if (this.scrollProperties.contentLength === null ||
      this.scrollProperties.visibleLength === null ||
      this.state.curRenderedRowsCount === this.props.dataSource.getRowCount()) {
      this._maybeCallOnEndReached();
      return;
    }

    var distanceFromEnd = this._getDistanceFromEnd(this.scrollProperties);
    if (distanceFromEnd < this.props.scrollRenderAheadDistance) {
      this._pageInNewRows();
    }
  },

  _pageInNewRows: function(props = this.props) {
    if (this._isUpdatedBatchComplete(this.state.updateBatchId)) {
      DEBUG && console.log({updateBatchId: this.state.updateBatchId});

      var rowsToRender;
      var actualPageSize;
      var updateBatchId = this.state.updateBatchId;

      if (!this._hasRenderedInitialListSize) {
        actualPageSize = rowsToRender = Math.min(
          props.initialListSize,
          props.dataSource.getRowCount()
        );
      } else {
        rowsToRender = Math.min(
          this.state.curRenderedRowsCount + props.pageSize,
          props.dataSource.getRowCount()
        );

        actualPageSize = rowsToRender - this.state.curRenderedRowsCount;
      }

      if (actualPageSize > 0) {
        updateBatchId += 1;

        this._updateBatches[updateBatchId] = {
          complete: 0,
          firstRow: this.state.curRenderedRowsCount,
          rows: actualPageSize,
        };

        this.setState((state, props) => {
          if (this._resetRowCount) {
            this._prevRenderedRowsCount = 0;
            this._resetRowCount = false;
          } else {
            this._prevRenderedRowsCount = state.curRenderedRowsCount;
          }

          return {
            curRenderedRowsCount: rowsToRender,
            updateBatchId,
          };
        }, () => {
          if (!this._hasRenderedInitialListSize) {
            this._hasRenderedInitialListSize = true;
            this._updateBatches[updateBatchId].complete = this._updateBatches[updateBatchId].rows;
          }

          this._measureAndUpdateScrollProps();
          this._prevRenderedRowsCount = this.state.curRenderedRowsCount;
        });
      }
    } else {
      if (!this._pageInTimeout) {
        this._pageInTimeout = setTimeout(() => {
          this._pageInNewRows();
          this._pageInTimeout = null;
        }, 100);
      }
    }
  },

  _getDistanceFromEnd: function(scrollProperties) {
    var maxLength = Math.max(
      scrollProperties.contentLength,
      scrollProperties.visibleLength
    );
    return maxLength - scrollProperties.visibleLength - scrollProperties.offset;
  },

  _updateVisibleRows: function(updatedFrames) {
    if (!this.props.onChangeVisibleRows) {
      return; // No need to compute visible rows if there is no callback
    }
    if (updatedFrames) {
      updatedFrames.forEach((newFrame) => {
        this._childFrames[newFrame.index] = merge(newFrame);
      });
    }
    var isVertical = !this.props.horizontal;
    var dataSource = this.props.dataSource;
    var visibleMin = this.scrollProperties.offset;
    var visibleMax = visibleMin + this.scrollProperties.visibleLength;
    var allRowIDs = dataSource.rowIdentities;

    var header = this.props.renderHeader && this.props.renderHeader();
    var totalIndex = header ? 1 : 0;
    var visibilityChanged = false;
    var changedRows = {};
    for (var sectionIdx = 0; sectionIdx < allRowIDs.length; sectionIdx++) {
      var rowIDs = allRowIDs[sectionIdx];
      if (rowIDs.length === 0) {
        continue;
      }
      var sectionID = dataSource.sectionIdentities[sectionIdx];
      if (this.props.renderSectionHeader) {
        totalIndex++;
      }
      var visibleSection = this._visibleRows[sectionID];
      if (!visibleSection) {
        visibleSection = {};
      }
      for (var rowIdx = 0; rowIdx < rowIDs.length; rowIdx++) {
        var rowID = rowIDs[rowIdx];
        var frame = this._childFrames[totalIndex];
        totalIndex++;
        if (!frame) {
          break;
        }
        var rowVisible = visibleSection[rowID];
        var min = isVertical ? frame.y : frame.x;
        var max = min + (isVertical ? frame.height : frame.width);
        if (min > visibleMax || max < visibleMin) {
          if (rowVisible) {
            visibilityChanged = true;
            delete visibleSection[rowID];
            if (!changedRows[sectionID]) {
              changedRows[sectionID] = {};
            }
            changedRows[sectionID][rowID] = false;
          }
        } else if (!rowVisible) {
          visibilityChanged = true;
          visibleSection[rowID] = true;
          if (!changedRows[sectionID]) {
            changedRows[sectionID] = {};
          }
          changedRows[sectionID][rowID] = true;
        }
      }
      if (!isEmpty(visibleSection)) {
        this._visibleRows[sectionID] = visibleSection;
      } else if (this._visibleRows[sectionID]) {
        delete this._visibleRows[sectionID];
      }
    }
    visibilityChanged && this.props.onChangeVisibleRows(this._visibleRows, changedRows);
  },

  _onScroll: function(e) {
    var isVertical = !this.props.horizontal;
    this.scrollProperties.visibleLength = e.nativeEvent.layoutMeasurement[
      isVertical ? 'height' : 'width'
    ];
    this.scrollProperties.contentLength = e.nativeEvent.contentSize[
      isVertical ? 'height' : 'width'
    ];
    this.scrollProperties.offset = e.nativeEvent.contentOffset[
      isVertical ? 'y' : 'x'
    ];
    this._updateVisibleRows(e.nativeEvent.updatedChildFrames);
    if (!this._maybeCallOnEndReached(e)) {
      this._renderMoreRowsIfNeeded();
    }

    if (this.props.onEndReached &&
        this._getDistanceFromEnd(this.scrollProperties) > this.props.onEndReachedThreshold) {
      // Scrolled out of the end zone, so it should be able to trigger again.
      this._sentEndForContentLength = null;
    }

    this.props.onScroll && this.props.onScroll(e);
  },
});

class IncrementalSeparatorRenderer extends React.Component {

  render() {
    let {
      isBatchComplete,
      synchronous,
    } = this.props;

    return (
      <View
        ref={view => { this._view = view; }}
        style={isBatchComplete || synchronous ? {} : {position: 'absolute', left: 0, right: 0, opacity: 0}}>
        {this.props.render()}
      </View>
    );
  }

  batchIsComplete() {
    if (this._view) {
      this._view.setNativeProps({style: {position: 'relative', opacity: 1}});
    }
  }
}

class IncrementalRowRenderer extends React.Component {

  constructor(props) {
    super(props);

    this.state = {
      shouldRender: this.props.synchronous,
      isBatchComplete: this.props.isBatchComplete,
    };
  }

  batchIsComplete() {
    if (this._view) {
      this._view.setNativeProps({style: {position: 'relative', opacity: 1}});
    }
  }

  componentDidMount() {
    this._scheduleRender();
  }

  render() {
    if (this.state.shouldRender) {
      return (
        <View
          ref={view => { this._view = view; }}
          style={this.state.isBatchComplete || this.props.synchronous ? {} : {position: 'absolute', left: 0, right: 0, opacity: 0}}>
          {this.props.render()}
        </View>
      );
    } else {
      return null;
    }
  }

  _scheduleRender() {
    InteractionManager.runAfterInteractions({
      name: 'FeedView row: ' + this.props.rowID,
      gen: () => new Promise(resolve => {
        this.setState({shouldRender: true}, resolve);
      }),
    }).then(() => {
      this.props.onRender && this.props.onRender();
    });
  }

}

module.exports = FeedView;