import { DOCUMENT, isPlatformBrowser } from '@angular/common';
import {
  afterNextRender,
  DestroyRef,
  inject,
  Injectable,
  Injector,
  PLATFORM_ID,
  signal,
} from '@angular/core';

@Injectable({ providedIn: 'root' })
export class CommandPaletteService {
  private readonly document = inject(DOCUMENT);
  private readonly destroyRef = inject(DestroyRef);
  private readonly injector = inject(Injector);
  private readonly isBrowser = isPlatformBrowser(inject(PLATFORM_ID));

  readonly open = signal(false);
  readonly dialogId = 'command-palette-dialog';
  readonly titleId = 'command-palette-title';
  readonly descriptionId = 'command-palette-description';
  readonly inputId = 'command-palette-input';
  readonly suggestionsId = 'command-palette-suggestions';

  private opener: HTMLElement | null = null;
  private previousOverflow = '';
  private scrollLocked = false;

  constructor() {
    afterNextRender(
      () => {
        if (!this.isBrowser) {
          return;
        }

        this.document.addEventListener('keydown', this.onDocumentKeydown);
      },
      { injector: this.injector },
    );

    this.destroyRef.onDestroy(() => this.teardown());
  }

  openPalette(opener?: HTMLElement | null): void {
    if (this.open()) {
      return;
    }

    const active = opener ?? this.document.activeElement;
    this.opener = active instanceof HTMLElement ? active : null;
    this.lockScroll();
    this.open.set(true);
  }

  close(): void {
    if (!this.open()) {
      return;
    }

    this.open.set(false);
    this.unlockScroll();
    this.restoreFocus();
  }

  private restoreFocus(): void {
    const opener = this.opener;
    this.opener = null;

    afterNextRender(
      () => {
        if (opener instanceof HTMLElement && opener.isConnected) {
          opener.focus();
        }
      },
      { injector: this.injector },
    );
  }

  private lockScroll(): void {
    if (!this.isBrowser || this.scrollLocked) {
      return;
    }

    this.previousOverflow = this.document.body.style.overflow;
    this.document.body.style.overflow = 'hidden';
    this.scrollLocked = true;
  }

  private unlockScroll(): void {
    if (!this.isBrowser || !this.scrollLocked) {
      return;
    }

    this.document.body.style.overflow = this.previousOverflow;
    this.previousOverflow = '';
    this.scrollLocked = false;
  }

  private teardown(): void {
    this.document.removeEventListener('keydown', this.onDocumentKeydown);
    this.unlockScroll();
    this.open.set(false);
    this.opener = null;
  }

  private readonly onDocumentKeydown = (event: KeyboardEvent): void => {
    if (event.key.toLowerCase() !== 'k' || !(event.ctrlKey || event.metaKey) || event.altKey) {
      return;
    }

    event.preventDefault();
    this.openPalette();
  };
}