/**
 * @license
 * Copyright Google LLC All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */
import { Directive, Input, IterableDiffers, TemplateRef, ViewContainerRef, ɵRuntimeError as RuntimeError } from '@angular/core';
import * as i0 from "@angular/core";
/**
 * @publicApi
 */
export class NgForOfContext {
    constructor($implicit, ngForOf, index, count) {
        this.$implicit = $implicit;
        this.ngForOf = ngForOf;
        this.index = index;
        this.count = count;
    }
    get first() {
        return this.index === 0;
    }
    get last() {
        return this.index === this.count - 1;
    }
    get even() {
        return this.index % 2 === 0;
    }
    get odd() {
        return !this.even;
    }
}
/**
 * A [structural directive](guide/structural-directives) that renders
 * a template for each item in a collection.
 * The directive is placed on an element, which becomes the parent
 * of the cloned templates.
 *
 * The `ngForOf` directive is generally used in the
 * [shorthand form](guide/structural-directives#asterisk) `*ngFor`.
 * In this form, the template to be rendered for each iteration is the content
 * of an anchor element containing the directive.
 *
 * The following example shows the shorthand syntax with some options,
 * contained in an `<li>` element.
 *
 * ```
 * <li *ngFor="let item of items; index as i; trackBy: trackByFn">...</li>
 * ```
 *
 * The shorthand form expands into a long form that uses the `ngForOf` selector
 * on an `<ng-template>` element.
 * The content of the `<ng-template>` element is the `<li>` element that held the
 * short-form directive.
 *
 * Here is the expanded version of the short-form example.
 *
 * ```
 * <ng-template ngFor let-item [ngForOf]="items" let-i="index" [ngForTrackBy]="trackByFn">
 *   <li>...</li>
 * </ng-template>
 * ```
 *
 * Angular automatically expands the shorthand syntax as it compiles the template.
 * The context for each embedded view is logically merged to the current component
 * context according to its lexical position.
 *
 * When using the shorthand syntax, Angular allows only [one structural directive
 * on an element](guide/structural-directives#one-per-element).
 * If you want to iterate conditionally, for example,
 * put the `*ngIf` on a container element that wraps the `*ngFor` element.
 * For further discussion, see
 * [Structural Directives](guide/structural-directives#one-per-element).
 *
 * @usageNotes
 *
 * ### Local variables
 *
 * `NgForOf` provides exported values that can be aliased to local variables.
 * For example:
 *
 *  ```
 * <li *ngFor="let user of users; index as i; first as isFirst">
 *    {{i}}/{{users.length}}. {{user}} <span *ngIf="isFirst">default</span>
 * </li>
 * ```
 *
 * The following exported values can be aliased to local variables:
 *
 * - `$implicit: T`: The value of the individual items in the iterable (`ngForOf`).
 * - `ngForOf: NgIterable<T>`: The value of the iterable expression. Useful when the expression is
 * more complex then a property access, for example when using the async pipe (`userStreams |
 * async`).
 * - `index: number`: The index of the current item in the iterable.
 * - `count: number`: The length of the iterable.
 * - `first: boolean`: True when the item is the first item in the iterable.
 * - `last: boolean`: True when the item is the last item in the iterable.
 * - `even: boolean`: True when the item has an even index in the iterable.
 * - `odd: boolean`: True when the item has an odd index in the iterable.
 *
 * ### Change propagation
 *
 * When the contents of the iterator changes, `NgForOf` makes the corresponding changes to the DOM:
 *
 * * When an item is added, a new instance of the template is added to the DOM.
 * * When an item is removed, its template instance is removed from the DOM.
 * * When items are reordered, their respective templates are reordered in the DOM.
 *
 * Angular uses object identity to track insertions and deletions within the iterator and reproduce
 * those changes in the DOM. This has important implications for animations and any stateful
 * controls that are present, such as `<input>` elements that accept user input. Inserted rows can
 * be animated in, deleted rows can be animated out, and unchanged rows retain any unsaved state
 * such as user input.
 * For more on animations, see [Transitions and Triggers](guide/transition-and-triggers).
 *
 * The identities of elements in the iterator can change while the data does not.
 * This can happen, for example, if the iterator is produced from an RPC to the server, and that
 * RPC is re-run. Even if the data hasn't changed, the second response produces objects with
 * different identities, and Angular must tear down the entire DOM and rebuild it (as if all old
 * elements were deleted and all new elements inserted).
 *
 * To avoid this expensive operation, you can customize the default tracking algorithm.
 * by supplying the `trackBy` option to `NgForOf`.
 * `trackBy` takes a function that has two arguments: `index` and `item`.
 * If `trackBy` is given, Angular tracks changes by the return value of the function.
 *
 * @see [Structural Directives](guide/structural-directives)
 * @ngModule CommonModule
 * @publicApi
 */
export class NgForOf {
    /**
     * The value of the iterable expression, which can be used as a
     * [template input variable](guide/structural-directives#shorthand).
     */
    set ngForOf(ngForOf) {
        this._ngForOf = ngForOf;
        this._ngForOfDirty = true;
    }
    /**
     * Specifies a custom `TrackByFunction` to compute the identity of items in an iterable.
     *
     * If a custom `TrackByFunction` is not provided, `NgForOf` will use the item's [object
     * identity](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is)
     * as the key.
     *
     * `NgForOf` uses the computed key to associate items in an iterable with DOM elements
     * it produces for these items.
     *
     * A custom `TrackByFunction` is useful to provide good user experience in cases when items in an
     * iterable rendered using `NgForOf` have a natural identifier (for example, custom ID or a
     * primary key), and this iterable could be updated with new object instances that still
     * represent the same underlying entity (for example, when data is re-fetched from the server,
     * and the iterable is recreated and re-rendered, but most of the data is still the same).
     *
     * @see {@link TrackByFunction}
     */
    set ngForTrackBy(fn) {
        if ((typeof ngDevMode === 'undefined' || ngDevMode) && fn != null && typeof fn !== 'function') {
            console.warn(`trackBy must be a function, but received ${JSON.stringify(fn)}. ` +
                `See https://angular.io/api/common/NgForOf#change-propagation for more information.`);
        }
        this._trackByFn = fn;
    }
    get ngForTrackBy() {
        return this._trackByFn;
    }
    constructor(_viewContainer, _template, _differs) {
        this._viewContainer = _viewContainer;
        this._template = _template;
        this._differs = _differs;
        this._ngForOf = null;
        this._ngForOfDirty = true;
        this._differ = null;
    }
    /**
     * A reference to the template that is stamped out for each item in the iterable.
     * @see [template reference variable](guide/template-reference-variables)
     */
    set ngForTemplate(value) {
        // TODO(TS2.1): make TemplateRef<Partial<NgForRowOf<T>>> once we move to TS v2.1
        // The current type is too restrictive; a template that just uses index, for example,
        // should be acceptable.
        if (value) {
            this._template = value;
        }
    }
    /**
     * Applies the changes when needed.
     * @nodoc
     */
    ngDoCheck() {
        if (this._ngForOfDirty) {
            this._ngForOfDirty = false;
            // React on ngForOf changes only once all inputs have been initialized
            const value = this._ngForOf;
            if (!this._differ && value) {
                if (typeof ngDevMode === 'undefined' || ngDevMode) {
                    try {
                        // CAUTION: this logic is duplicated for production mode below, as the try-catch
                        // is only present in development builds.
                        this._differ = this._differs.find(value).create(this.ngForTrackBy);
                    }
                    catch {
                        let errorMessage = `Cannot find a differ supporting object '${value}' of type '` +
                            `${getTypeName(value)}'. NgFor only supports binding to Iterables, such as Arrays.`;
                        if (typeof value === 'object') {
                            errorMessage += ' Did you mean to use the keyvalue pipe?';
                        }
                        throw new RuntimeError(-2200 /* RuntimeErrorCode.NG_FOR_MISSING_DIFFER */, errorMessage);
                    }
                }
                else {
                    // CAUTION: this logic is duplicated for development mode above, as the try-catch
                    // is only present in development builds.
                    this._differ = this._differs.find(value).create(this.ngForTrackBy);
                }
            }
        }
        if (this._differ) {
            const changes = this._differ.diff(this._ngForOf);
            if (changes)
                this._applyChanges(changes);
        }
    }
    _applyChanges(changes) {
        const viewContainer = this._viewContainer;
        changes.forEachOperation((item, adjustedPreviousIndex, currentIndex) => {
            if (item.previousIndex == null) {
                // NgForOf is never "null" or "undefined" here because the differ detected
                // that a new item needs to be inserted from the iterable. This implies that
                // there is an iterable value for "_ngForOf".
                viewContainer.createEmbeddedView(this._template, new NgForOfContext(item.item, this._ngForOf, -1, -1), currentIndex === null ? undefined : currentIndex);
            }
            else if (currentIndex == null) {
                viewContainer.remove(adjustedPreviousIndex === null ? undefined : adjustedPreviousIndex);
            }
            else if (adjustedPreviousIndex !== null) {
                const view = viewContainer.get(adjustedPreviousIndex);
                viewContainer.move(view, currentIndex);
                applyViewChange(view, item);
            }
        });
        for (let i = 0, ilen = viewContainer.length; i < ilen; i++) {
            const viewRef = viewContainer.get(i);
            const context = viewRef.context;
            context.index = i;
            context.count = ilen;
            context.ngForOf = this._ngForOf;
        }
        changes.forEachIdentityChange((record) => {
            const viewRef = viewContainer.get(record.currentIndex);
            applyViewChange(viewRef, record);
        });
    }
    /**
     * Asserts the correct type of the context for the template that `NgForOf` will render.
     *
     * The presence of this method is a signal to the Ivy template type-check compiler that the
     * `NgForOf` structural directive renders its template with a specific context type.
     */
    static ngTemplateContextGuard(dir, ctx) {
        return true;
    }
    static { this.ɵfac = i0.ɵɵngDeclareFactory({ minVersion: "12.0.0", version: "16.2.9", ngImport: i0, type: NgForOf, deps: [{ token: i0.ViewContainerRef }, { token: i0.TemplateRef }, { token: i0.IterableDiffers }], target: i0.ɵɵFactoryTarget.Directive }); }
    static { this.ɵdir = i0.ɵɵngDeclareDirective({ minVersion: "14.0.0", version: "16.2.9", type: NgForOf, isStandalone: true, selector: "[ngFor][ngForOf]", inputs: { ngForOf: "ngForOf", ngForTrackBy: "ngForTrackBy", ngForTemplate: "ngForTemplate" }, ngImport: i0 }); }
}
i0.ɵɵngDeclareClassMetadata({ minVersion: "12.0.0", version: "16.2.9", ngImport: i0, type: NgForOf, decorators: [{
            type: Directive,
            args: [{
                    selector: '[ngFor][ngForOf]',
                    standalone: true,
                }]
        }], ctorParameters: function () { return [{ type: i0.ViewContainerRef }, { type: i0.TemplateRef }, { type: i0.IterableDiffers }]; }, propDecorators: { ngForOf: [{
                type: Input
            }], ngForTrackBy: [{
                type: Input
            }], ngForTemplate: [{
                type: Input
            }] } });
// Also export the `NgForOf` class as `NgFor` to improve the DX for
// cases when the directive is used as standalone, so the class name
// matches the CSS selector (*ngFor).
export { NgForOf as NgFor };
function applyViewChange(view, record) {
    view.context.$implicit = record.item;
}
function getTypeName(type) {
    return type['name'] || typeof type;
}
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