All files / lib/internal/text-highlight text-highlight.component.ts

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/*******************************************************************************
 * Copyright bei
 * Entwicklungs- und Pflegeverbund für das gemeinsame Fachverfahren gefa
 *
 *******************************************************************************/
import {
  AfterContentInit,
  Component,
  EventEmitter,
  HostBinding,
  Injectable,
  Input,
  OnChanges,
  OnDestroy,
  Optional,
  SimpleChanges,
} from '@angular/core';
import { Subscription } from 'rxjs';
 
// Defined in MDN - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions#escaping
function escapeRegExp(expression: string) {
  return expression.replace(/[.*+?^${}()|[\]\\]/g, '\\$&'); // $& means the whole matched string
}
 
function createRegex(
  search: string,
  prefixOnly: boolean,
  patterns: Patterns[],
): RegExp {
  const out = escapeRegExp(search);
  let regex = prefixOnly ? '^' + out : out;
  for (const pattern of patterns) {
    regex = escapePattern(regex, pattern);
  }
  return new RegExp(regex, 'gi');
}
 
function escapePattern(regex: string, pattern: Patterns) {
  if (pattern === 'asterisk') {
    return regex.replaceAll('\\*', '.*');
  } else {
    return regex.replaceAll('\\?', '.');
  }
}
 
@Injectable()
export class TextHighlightService {
  public set highlightString(val: string | undefined) {
    this._highlightString = val;
    this.highlightStringChange.emit(val);
  }
 
  public get highlightString(): string | undefined {
    return this._highlightString;
  }
 
  public readonly highlightStringChange: EventEmitter<string | undefined> =
    new EventEmitter<string | undefined>();
 
  private _highlightString?: string;
}
 
interface TextHighlightPart {
  text: string;
  mark?: boolean;
}
 
export type Patterns = 'asterisk' | 'question-mark';
 
/**
 * Highlight substrings within a text.
 */
@Component({
  selector: 'gc-text-highlight',
  templateUrl: './text-highlight.component.html',
  styleUrls: ['./text-highlight.component.css'],
})
export class TextHighlightComponent
  implements AfterContentInit, OnChanges, OnDestroy
{
  /**
   * The text to display.
   */
  @Input()
  public text?: string;
 
  /**
   * Optional substring to highlight within the displayed text.
   */
  @Input()
  public highlight?: string;
 
  /**
   * If `true`, the highlight is only shown if it's a prefix of the displayed text. Otherwise, all
   * occurrences of the highlight are marked.
   */
  @Input()
  public prefixOnly = false;
 
  /**
   * List of patterns supported by the highlighting
   * - asterisk: `*` in highlight means any number of character
   * - question-mark: `?` in highlight means one character
   */
  @Input()
  public supportedPatterns: Patterns[] = ['asterisk', 'question-mark'];
 
  /**
   * Display variant of the marked highlights.
   */
  @Input()
  public variant: 'default' | 'inverted' | 'reduced' = 'default';
 
  /** @ignore */
  @HostBinding('class')
  private get cssClass(): string {
    return `gc-text-highlight-variant-${this.variant}`;
  }
 
  /** @ignore */
  public _highlightParts: TextHighlightPart[] = [];
 
  /** @ignore */
  private readonly highlightStringChangeSubscription?: Subscription;
 
  constructor(@Optional() private service: TextHighlightService | null) {
    service?.highlightStringChange.subscribe(val => {
      this.highlight = val;
      this.calculateHighlightParts(); // direct setting does not trigger Angular change detection, update thus invoked manually
    });
  }
 
  /** @ignore */
  public ngOnDestroy(): void {
    this.highlightStringChangeSubscription?.unsubscribe();
  }
 
  /** @ignore */
  public ngAfterContentInit(): void {
    if (this.service) {
      this.highlight = this.service.highlightString;
      this.calculateHighlightParts();
    }
  }
 
  /** @ignore */
  public ngOnChanges(changes: SimpleChanges): void {
    if (
      'text' in changes ||
      'highlight' in changes ||
      'prefixOnly' in changes
    ) {
      this.calculateHighlightParts();
    }
  }
 
  /** @ignore */
  public _partTrackBy(index: number, part: TextHighlightPart): string {
    return `${index.toString()}_${part.mark ? 't' : 'f'}_${part.text}`;
  }
 
  /** @ignore */
  private calculateHighlightParts(): void {
    if (!this.text) {
      this._highlightParts = [];
    } else if (!this.highlight) {
      this._highlightParts = [{ text: this.text }];
    } else {
      const regex = createRegex(
        this.highlight,
        this.prefixOnly,
        this.supportedPatterns,
      );
      const parts: TextHighlightPart[] = [];
 
      // using String.matchAll instead of RegExp.exec, as looping over exec gets stuck at the end when using the regex ".*"
      // matchAll doesn't have this problem as it returns an iterator and can be used as direct replacement otherwise
      // see also:
      // - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp/exec#finding_successive_matches ("pitfalls [...] match zero-length characters")
      // - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/matchAll#regexp.prototype.exec_and_matchall)
      let lastMatchEnd = 0;
      for (const match of this.text.matchAll(regex)) {
        if (match.index - lastMatchEnd > 0) {
          // store text between the previous match and the current one as unmarked part
          parts.push({ text: this.text.substring(lastMatchEnd, match.index) });
        }
        if (match[0].length > 0) {
          parts.push({ text: match[0], mark: true });
        }
        lastMatchEnd = match.index + match[0].length;
      }
      // store text following after the last match
      if (lastMatchEnd < this.text.length) {
        parts.push({ text: this.text.substring(lastMatchEnd) });
      }
 
      this._highlightParts = parts;
    }
  }
}