NativeScript/nativescript-core/ui/list-view/list-view.ios.ts

import { ItemEventData } from ".";
import {
    ListViewBase, View, KeyedTemplate, Length, Observable, Color,
    separatorColorProperty, itemTemplatesProperty, iosEstimatedRowHeightProperty, layout, EventData
} from "./list-view-common";
import { StackLayout } from "../layouts/stack-layout";
import { ProxyViewContainer } from "../proxy-view-container";
import { profile } from "../../profiling";
import * as trace from "../../trace";

export * from "./list-view-common";

const ITEMLOADING = ListViewBase.itemLoadingEvent;
const LOADMOREITEMS = ListViewBase.loadMoreItemsEvent;
const ITEMTAP = ListViewBase.itemTapEvent;
const DEFAULT_HEIGHT = 44;

const infinity = layout.makeMeasureSpec(0, layout.UNSPECIFIED);

interface ViewItemIndex {
    _listViewItemIndex?: number;
}

type ItemView = View & ViewItemIndex;

class ListViewCell extends UITableViewCell {
    public static initWithEmptyBackground(): ListViewCell {
        const cell = <ListViewCell>ListViewCell.new();
        // Clear background by default - this will make cells transparent
        cell.backgroundColor = null;

        return cell;
    }

    initWithStyleReuseIdentifier(style: UITableViewCellStyle, reuseIdentifier: string): this {
        const cell = <this>super.initWithStyleReuseIdentifier(style, reuseIdentifier);
        // Clear background by default - this will make cells transparent
        cell.backgroundColor = null;

        return cell;
    }

    public willMoveToSuperview(newSuperview: UIView): void {
        let parent = <ListView>(this.view ? this.view.parent : null);

        // When inside ListView and there is no newSuperview this cell is
        // removed from native visual tree so we remove it from our tree too.
        if (parent && !newSuperview) {
            parent._removeContainer(this);
        }
    }

    public get view(): View {
        return this.owner ? this.owner.get() : null;
    }

    public owner: WeakRef<View>;
}

function notifyForItemAtIndex(listView: ListViewBase, cell: any, view: View, eventName: string, indexPath: NSIndexPath) {
    let args = <ItemEventData>{ eventName: eventName, object: listView, index: indexPath.row, view: view, ios: cell, android: undefined };
    listView.notify(args);

    return args;
}

class DataSource extends NSObject implements UITableViewDataSource {
    public static ObjCProtocols = [UITableViewDataSource];

    private _owner: WeakRef<ListView>;

    public static initWithOwner(owner: WeakRef<ListView>): DataSource {
        let dataSource = <DataSource>DataSource.new();
        dataSource._owner = owner;

        return dataSource;
    }

    public tableViewNumberOfRowsInSection(tableView: UITableView, section: number) {
        let owner = this._owner.get();

        return (owner && owner.items) ? owner.items.length : 0;
    }

    public tableViewCellForRowAtIndexPath(tableView: UITableView, indexPath: NSIndexPath): UITableViewCell {
        // We call this method because ...ForIndexPath calls tableViewHeightForRowAtIndexPath immediately (before we can prepare and measure it).
        let owner = this._owner.get();
        let cell: ListViewCell;
        if (owner) {
            let template = owner._getItemTemplate(indexPath.row);
            cell = <ListViewCell>(tableView.dequeueReusableCellWithIdentifier(template.key) || ListViewCell.initWithEmptyBackground());
            owner._prepareCell(cell, indexPath);

            let cellView: View = cell.view;
            if (cellView && cellView.isLayoutRequired) {
                // Arrange cell views. We do it here instead of _layoutCell because _layoutCell is called
                // from 'tableViewHeightForRowAtIndexPath' method too (in iOS 7.1) and we don't want to arrange the fake cell.
                let width = layout.getMeasureSpecSize(owner.widthMeasureSpec);
                let rowHeight = owner._effectiveRowHeight;
                let cellHeight = rowHeight > 0 ? rowHeight : owner.getHeight(indexPath.row);
                cellView.iosOverflowSafeAreaEnabled = false;
                View.layoutChild(owner, cellView, 0, 0, width, cellHeight);
            }
        }
        else {
            cell = <ListViewCell>ListViewCell.initWithEmptyBackground();
        }

        return cell;
    }
}

class UITableViewDelegateImpl extends NSObject implements UITableViewDelegate {
    public static ObjCProtocols = [UITableViewDelegate];

    private _owner: WeakRef<ListView>;

    private _measureCellMap: Map<string, ListViewCell>;

    public static initWithOwner(owner: WeakRef<ListView>): UITableViewDelegateImpl {
        const delegate = <UITableViewDelegateImpl>UITableViewDelegateImpl.new();
        delegate._owner = owner;
        delegate._measureCellMap = new Map<string, ListViewCell>();

        return delegate;
    }

    public tableViewWillDisplayCellForRowAtIndexPath(tableView: UITableView, cell: UITableViewCell, indexPath: NSIndexPath) {
        const owner = this._owner.get();
        if (owner && (indexPath.row === owner.items.length - 1)) {
            owner.notify(<EventData>{ eventName: LOADMOREITEMS, object: owner });
        }
    }

    public tableViewWillSelectRowAtIndexPath(tableView: UITableView, indexPath: NSIndexPath): NSIndexPath {
        const cell = <ListViewCell>tableView.cellForRowAtIndexPath(indexPath);
        const owner = this._owner.get();
        if (owner) {
            notifyForItemAtIndex(owner, cell, cell.view, ITEMTAP, indexPath);
        }

        return indexPath;
    }

    public tableViewDidSelectRowAtIndexPath(tableView: UITableView, indexPath: NSIndexPath): NSIndexPath {
        tableView.deselectRowAtIndexPathAnimated(indexPath, true);

        return indexPath;
    }

    public tableViewHeightForRowAtIndexPath(tableView: UITableView, indexPath: NSIndexPath): number {
        const owner = this._owner.get();
        if (!owner) {
            return tableView.estimatedRowHeight;
        }

        let height = owner.getHeight(indexPath.row);
        if (height === undefined) {
            // in iOS8+ after call to scrollToRowAtIndexPath:atScrollPosition:animated: this method is called before tableViewCellForRowAtIndexPath so we need fake cell to measure its content.
            const template = owner._getItemTemplate(indexPath.row);
            let cell = this._measureCellMap.get(template.key);
            if (!cell) {
                cell = (<any>tableView.dequeueReusableCellWithIdentifier(template.key)) || ListViewCell.initWithEmptyBackground();
                this._measureCellMap.set(template.key, cell);
            }

            height = owner._prepareCell(cell, indexPath);
        }

        return layout.toDeviceIndependentPixels(height);
    }
}

class UITableViewRowHeightDelegateImpl extends NSObject implements UITableViewDelegate {
    public static ObjCProtocols = [UITableViewDelegate];

    private _owner: WeakRef<ListView>;

    public static initWithOwner(owner: WeakRef<ListView>): UITableViewRowHeightDelegateImpl {
        let delegate = <UITableViewRowHeightDelegateImpl>UITableViewRowHeightDelegateImpl.new();
        delegate._owner = owner;

        return delegate;
    }

    public tableViewWillDisplayCellForRowAtIndexPath(tableView: UITableView, cell: UITableViewCell, indexPath: NSIndexPath) {
        let owner = this._owner.get();
        if (owner && (indexPath.row === owner.items.length - 1)) {
            owner.notify(<EventData>{ eventName: LOADMOREITEMS, object: owner });
        }
    }

    public tableViewWillSelectRowAtIndexPath(tableView: UITableView, indexPath: NSIndexPath): NSIndexPath {
        let cell = <ListViewCell>tableView.cellForRowAtIndexPath(indexPath);
        let owner = this._owner.get();
        if (owner) {
            notifyForItemAtIndex(owner, cell, cell.view, ITEMTAP, indexPath);
        }

        return indexPath;
    }

    public tableViewDidSelectRowAtIndexPath(tableView: UITableView, indexPath: NSIndexPath): NSIndexPath {
        tableView.deselectRowAtIndexPathAnimated(indexPath, true);

        return indexPath;
    }

    public tableViewHeightForRowAtIndexPath(tableView: UITableView, indexPath: NSIndexPath): number {
        let owner = this._owner.get();
        if (!owner) {
            return tableView.estimatedRowHeight;
        }

        return layout.toDeviceIndependentPixels(owner._effectiveRowHeight);
    }
}

export class ListView extends ListViewBase {
    public nativeViewProtected: UITableView;
    // tslint:disable-next-line
    private _dataSource;
    private _delegate;
    private _heights: Array<number>;
    private _preparingCell: boolean;
    private _isDataDirty: boolean;
    private _map: Map<ListViewCell, ItemView>;
    widthMeasureSpec: number = 0;

    constructor() {
        super();
        this._map = new Map<ListViewCell, ItemView>();
        this._heights = new Array<number>();
    }

    createNativeView() {
        return UITableView.new();
    }

    initNativeView() {
        super.initNativeView();
        const nativeView = this.nativeViewProtected;
        nativeView.registerClassForCellReuseIdentifier(ListViewCell.class(), this._defaultTemplate.key);
        nativeView.estimatedRowHeight = DEFAULT_HEIGHT;
        nativeView.rowHeight = UITableViewAutomaticDimension;
        nativeView.dataSource = this._dataSource = DataSource.initWithOwner(new WeakRef(this));
        this._delegate = UITableViewDelegateImpl.initWithOwner(new WeakRef(this));
        this._setNativeClipToBounds();
    }

    disposeNativeView() {
        this._delegate = null;
        this._dataSource = null;
        super.disposeNativeView();
    }

    _setNativeClipToBounds() {
        // Always set clipsToBounds for list-view
        this.ios.clipsToBounds = true;
    }

    @profile
    public onLoaded() {
        super.onLoaded();
        if (this._isDataDirty) {
            this.refresh();
        }
        this.ios.delegate = this._delegate;
    }

    public onUnloaded() {
        this.ios.delegate = null;
        super.onUnloaded();
    }

    get ios(): UITableView {
        return this.nativeViewProtected;
    }

    get _childrenCount(): number {
        return this._map.size;
    }

    public eachChildView(callback: (child: View) => boolean): void {
        this._map.forEach((view, key) => {
            callback(view);
        });
    }

    public scrollToIndex(index: number) {
        this._scrollToIndex(index, false);
    }

    public scrollToIndexAnimated(index: number) {
        this._scrollToIndex(index);
    }

    private _scrollToIndex(index: number, animated: boolean = true) {
        if (!this.ios) {
            return;
        }

        const itemsLength = this.items ? this.items.length : 0;
        // mimic Android behavior that silently coerces index values within [0, itemsLength - 1] range
        if (itemsLength > 0) {
            if (index < 0) {
                index = 0;
            } else if (index >= itemsLength) {
                index = itemsLength - 1;
            }

            this.ios.scrollToRowAtIndexPathAtScrollPositionAnimated(NSIndexPath.indexPathForItemInSection(index, 0),
                UITableViewScrollPosition.Top, animated);
        } else if (trace.isEnabled()) {
            trace.write(`Cannot scroll listview to index ${index} when listview items not set`, trace.categories.Binding);
        }
    }

    public refresh() {
        // clear bindingContext when it is not observable because otherwise bindings to items won't reevaluate
        this._map.forEach((view, nativeView, map) => {
            if (!(view.bindingContext instanceof Observable)) {
                view.bindingContext = null;
            }
        });

        if (this.isLoaded) {
            this.ios.reloadData();
            this.requestLayout();
            this._isDataDirty = false;
        } else {
            this._isDataDirty = true;
        }
    }

    public isItemAtIndexVisible(itemIndex: number): boolean {
        const indexes: NSIndexPath[] = Array.from(this.ios.indexPathsForVisibleRows);

        return indexes.some(visIndex => visIndex.row === itemIndex);
    }

    public getHeight(index: number): number {
        return this._heights[index];
    }

    public setHeight(index: number, value: number): void {
        this._heights[index] = value;
    }

    public _onRowHeightPropertyChanged(oldValue: Length, newValue: Length) {
        const value = layout.toDeviceIndependentPixels(this._effectiveRowHeight);
        const nativeView = this.ios;
        if (value < 0) {
            nativeView.rowHeight = UITableViewAutomaticDimension;
            nativeView.estimatedRowHeight = DEFAULT_HEIGHT;
            this._delegate = UITableViewDelegateImpl.initWithOwner(new WeakRef(this));
        }
        else {
            nativeView.rowHeight = value;
            nativeView.estimatedRowHeight = value;
            this._delegate = UITableViewRowHeightDelegateImpl.initWithOwner(new WeakRef(this));
        }

        if (this.isLoaded) {
            nativeView.delegate = this._delegate;
        }

        super._onRowHeightPropertyChanged(oldValue, newValue);
    }

    public requestLayout(): void {
        // When preparing cell don't call super - no need to invalidate our measure when cell desiredSize is changed.
        if (!this._preparingCell) {
            super.requestLayout();
        }
    }

    public measure(widthMeasureSpec: number, heightMeasureSpec: number): void {
        this.widthMeasureSpec = widthMeasureSpec;
        const changed = this._setCurrentMeasureSpecs(widthMeasureSpec, heightMeasureSpec);
        super.measure(widthMeasureSpec, heightMeasureSpec);
        if (changed) {
            this.ios.reloadData();
        }
    }

    public onMeasure(widthMeasureSpec: number, heightMeasureSpec: number): void {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);

        this._map.forEach((childView, listViewCell) => {
            View.measureChild(this, childView, childView._currentWidthMeasureSpec, childView._currentHeightMeasureSpec);
        });
    }

    public onLayout(left: number, top: number, right: number, bottom: number): void {
        super.onLayout(left, top, right, bottom);

        this._map.forEach((childView, listViewCell) => {
            let rowHeight = this._effectiveRowHeight;
            let cellHeight = rowHeight > 0 ? rowHeight : this.getHeight(childView._listViewItemIndex);
            if (cellHeight) {
                let width = layout.getMeasureSpecSize(this.widthMeasureSpec);
                childView.iosOverflowSafeAreaEnabled = false;
                View.layoutChild(this, childView, 0, 0, width, cellHeight);
            }
        });
    }

    private _layoutCell(cellView: View, indexPath: NSIndexPath): number {
        if (cellView) {
            const rowHeight = this._effectiveRowHeight;
            const heightMeasureSpec: number = rowHeight >= 0 ? layout.makeMeasureSpec(rowHeight, layout.EXACTLY) : infinity;
            const measuredSize = View.measureChild(this, cellView, this.widthMeasureSpec, heightMeasureSpec);
            const height = measuredSize.measuredHeight;
            this.setHeight(indexPath.row, height);

            return height;
        }

        return this.ios.estimatedRowHeight;
    }

    public _prepareCell(cell: ListViewCell, indexPath: NSIndexPath): number {
        let cellHeight: number;
        try {
            this._preparingCell = true;
            let view: ItemView = cell.view;
            if (!view) {
                view = this._getItemTemplate(indexPath.row).createView();
            }

            let args = notifyForItemAtIndex(this, cell, view, ITEMLOADING, indexPath);
            view = args.view || this._getDefaultItemContent(indexPath.row);

            // Proxy containers should not get treated as layouts.
            // Wrap them in a real layout as well.
            if (view instanceof ProxyViewContainer) {
                let sp = new StackLayout();
                sp.addChild(view);
                view = sp;
            }

            // If cell is reused it have old content - remove it first.
            if (!cell.view) {
                cell.owner = new WeakRef(view);
            } else if (cell.view !== view) {
                this._removeContainer(cell);
                (<UIView>cell.view.nativeViewProtected).removeFromSuperview();
                cell.owner = new WeakRef(view);
            }

            this._prepareItem(view, indexPath.row);
            view._listViewItemIndex = indexPath.row;
            this._map.set(cell, view);

            // We expect that views returned from itemLoading are new (e.g. not reused).
            if (view && !view.parent) {
                this._addView(view);
                cell.contentView.addSubview(view.nativeViewProtected);
            }

            cellHeight = this._layoutCell(view, indexPath);
        } finally {
            this._preparingCell = false;
        }

        return cellHeight;
    }

    public _removeContainer(cell: ListViewCell): void {
        let view: ItemView = cell.view;
        // This is to clear the StackLayout that is used to wrap ProxyViewContainer instances.
        if (!(view.parent instanceof ListView)) {
            this._removeView(view.parent);
        }

        // No need to request layout when we are removing cells.
        const preparing = this._preparingCell;
        this._preparingCell = true;
        view.parent._removeView(view);
        view._listViewItemIndex = undefined;
        this._preparingCell = preparing;
        this._map.delete(cell);
    }

    [separatorColorProperty.getDefault](): UIColor {
        return this.ios.separatorColor;
    }
    [separatorColorProperty.setNative](value: Color | UIColor) {
        this.ios.separatorColor = value instanceof Color ? value.ios : value;
    }

    [itemTemplatesProperty.getDefault](): KeyedTemplate[] {
        return null;
    }
    [itemTemplatesProperty.setNative](value: KeyedTemplate[]) {
        this._itemTemplatesInternal = new Array<KeyedTemplate>(this._defaultTemplate);
        if (value) {
            for (let i = 0, length = value.length; i < length; i++) {
                this.ios.registerClassForCellReuseIdentifier(ListViewCell.class(), value[i].key);
            }
            this._itemTemplatesInternal = this._itemTemplatesInternal.concat(value);
        }

        this.refresh();
    }

    [iosEstimatedRowHeightProperty.getDefault](): Length {
        return DEFAULT_HEIGHT;
    }
    [iosEstimatedRowHeightProperty.setNative](value: Length) {
        const nativeView = this.ios;
        const estimatedHeight = Length.toDevicePixels(value, 0);
        nativeView.estimatedRowHeight = estimatedHeight < 0 ? DEFAULT_HEIGHT : estimatedHeight;
    }
}