import { DOCUMENT } from '@angular/common';
import {
  afterNextRender,
  ChangeDetectionStrategy,
  Component,
  computed,
  ElementRef,
  inject,
  Injector,
  input,
  signal,
  viewChild,
} from '@angular/core';
import { RouterLink } from '@angular/router';
import { SIGNATURE_COPY } from '../../core/content/signature-copy';
import { type AppLocale } from '../../core/i18n/locale';
import { LocaleService } from '../../core/i18n/locale.service';
import { NavigationService } from '../../core/navigation/navigation.service';
import { isBrowserPlatform } from '../../core/platform/browser';
import {
  connectedNodeIds,
  nodeHref,
  SYSTEMS_MAP_EDGES,
  SYSTEMS_MAP_NODE_KINDS,
  SYSTEMS_MAP_NODES,
  type SystemsMapNode,
  type SystemsMapNodeId,
} from './systems-map.model';

let systemsMapInstanceId = 0;

export interface SystemsMapNodeView {
  readonly id: SystemsMapNodeId;
  readonly kind: SystemsMapNode['kind'];
  readonly routeId: SystemsMapNode['routeId'];
  readonly fragment: string;
  readonly x: number;
  readonly y: number;
  readonly label: string;
  readonly labelLines: readonly string[];
  readonly summary: string;
  readonly gist: string;
  readonly href: string;
  readonly link: unknown[];
  readonly relationship: string;
  readonly accessibleName: string;
  readonly linkLabel: string;
  readonly shapeWidth: number;
  readonly shapeHeight: number;
  readonly textStartDy: number;
}

export interface SystemsMapEdgeView {
  readonly from: SystemsMapNodeId;
  readonly to: SystemsMapNodeId;
  readonly x1: number;
  readonly y1: number;
  readonly x2: number;
  readonly y2: number;
}

@Component({
  selector: 'app-systems-map',
  changeDetection: ChangeDetectionStrategy.OnPush,
  imports: [RouterLink],
  templateUrl: './systems-map.html',
  styleUrl: './systems-map.scss',
})
export class SystemsMap {
  readonly heading = input('');
  readonly intro = input('');
  readonly headingLevel = input<2 | 3>(2);

  private readonly document = inject(DOCUMENT);
  private readonly injector = inject(Injector);
  private readonly navigation = inject(NavigationService);
  private readonly localeService = inject(LocaleService);
  private readonly isBrowser = isBrowserPlatform();
  private readonly instanceId = systemsMapInstanceId++;
  private readonly dialogRef = viewChild<ElementRef<HTMLElement>>('gistDialog');
  private opener: HTMLElement | null = null;

  protected readonly headingId = `systems-map-heading-${this.instanceId}`;
  protected readonly svgTitleId = `systems-map-svg-title-${this.instanceId}`;
  protected readonly svgDescId = `systems-map-svg-desc-${this.instanceId}`;
  protected readonly listHeadingId = `systems-map-list-${this.instanceId}`;
  protected readonly legendHeadingId = `systems-map-legend-${this.instanceId}`;
  protected readonly dialogTitleId = `systems-map-dialog-title-${this.instanceId}`;
  protected readonly dialogDescId = `systems-map-dialog-desc-${this.instanceId}`;

  protected readonly activeNodeId = signal<SystemsMapNodeId | null>(null);
  protected readonly openNodeId = signal<SystemsMapNodeId | null>(null);

  protected readonly copy = computed(() => SIGNATURE_COPY[this.localeService.locale()].systemsMap);

  protected readonly headingText = computed(() => {
    const override = this.heading().trim();
    return override.length > 0 ? override : this.copy().heading;
  });

  protected readonly introText = computed(() => {
    const override = this.intro().trim();
    return override.length > 0 ? override : this.copy().intro;
  });

  protected readonly nodes = computed(() => {
    const locale = this.localeService.locale();
    return SYSTEMS_MAP_NODES.map((node) => this.toNodeView(node, locale));
  });

  protected readonly edges = computed((): readonly SystemsMapEdgeView[] => {
    const byId = new Map(SYSTEMS_MAP_NODES.map((node) => [node.id, node]));

    return SYSTEMS_MAP_EDGES.map((edge) => {
      const from = byId.get(edge.from);
      const to = byId.get(edge.to);

      return {
        from: edge.from,
        to: edge.to,
        x1: from?.x ?? 0,
        y1: from?.y ?? 0,
        x2: to?.x ?? 0,
        y2: to?.y ?? 0,
      };
    });
  });

  protected readonly legendItems = computed(() => {
    const legend = this.copy().legend;

    return SYSTEMS_MAP_NODE_KINDS.map((kind) => ({
      kind,
      label: legend[kind],
    }));
  });

  protected readonly openNode = computed(() => {
    const id = this.openNodeId();
    return id ? (this.nodes().find((node) => node.id === id) ?? null) : null;
  });

  protected readonly dialogTitle = computed(() => {
    const node = this.openNode();
    return node ? this.copy().dialogTitlePattern.replace('{node}', node.label) : '';
  });

  protected onNodeActivate(event: MouseEvent, node: SystemsMapNodeView): void {
    if (event.button !== 0 || event.ctrlKey || event.metaKey || event.shiftKey || event.altKey) {
      return;
    }

    event.preventDefault();
    this.openDialog(node.id, event.currentTarget as HTMLElement);
  }

  protected onNodeKeydown(event: KeyboardEvent, node: SystemsMapNodeView): void {
    if (event.key !== 'Enter' && event.key !== ' ') {
      return;
    }

    event.preventDefault();
    this.openDialog(node.id, event.currentTarget as HTMLElement);
  }

  protected onNodeEnter(id: SystemsMapNodeId): void {
    this.activeNodeId.set(id);
  }

  protected onNodeLeave(id: SystemsMapNodeId): void {
    if (this.activeNodeId() === id) {
      this.activeNodeId.set(null);
    }
  }

  protected closeDialog(): void {
    this.openNodeId.set(null);
    const opener = this.opener;
    this.opener = null;

    if (!this.isBrowser || !(opener instanceof HTMLElement)) {
      return;
    }

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

  protected onDialogKeydown(event: KeyboardEvent): void {
    if (event.key === 'Escape') {
      event.preventDefault();
      this.closeDialog();
      return;
    }

    if (event.key !== 'Tab') {
      return;
    }

    const dialog = this.dialogRef()?.nativeElement;
    if (!dialog) {
      return;
    }

    const focusable = this.focusableIn(dialog);
    if (focusable.length === 0) {
      event.preventDefault();
      return;
    }

    const first = focusable[0];
    const last = focusable[focusable.length - 1];
    const active = this.document.activeElement;

    if (event.shiftKey && active === first) {
      event.preventDefault();
      last.focus();
    } else if (!event.shiftKey && active === last) {
      event.preventDefault();
      first.focus();
    }
  }

  protected isConnectedNode(id: SystemsMapNodeId): boolean {
    const active = this.activeNodeId();
    return !!active && (active === id || this.neighborSet(active).has(id));
  }

  protected isDimmedNode(id: SystemsMapNodeId): boolean {
    const active = this.activeNodeId();
    return !!active && active !== id && !this.neighborSet(active).has(id);
  }

  protected isConnectedEdge(edge: SystemsMapEdgeView): boolean {
    const active = this.activeNodeId();
    return !!active && (edge.from === active || edge.to === active);
  }

  protected isDimmedEdge(edge: SystemsMapEdgeView): boolean {
    const active = this.activeNodeId();
    return !!active && edge.from !== active && edge.to !== active;
  }

  private openDialog(id: SystemsMapNodeId, opener: HTMLElement): void {
    this.opener = opener;
    this.openNodeId.set(id);

    afterNextRender(
      () => {
        const dialog = this.dialogRef()?.nativeElement;
        const target = this.focusableIn(dialog)[0] ?? dialog;
        target?.focus();
      },
      { injector: this.injector },
    );
  }

  private focusableIn(root: HTMLElement | undefined): HTMLElement[] {
    if (!root) {
      return [];
    }

    return Array.from(
      root.querySelectorAll<HTMLElement>(
        'a[href], button:not([disabled]), [tabindex]:not([tabindex="-1"])',
      ),
    ).filter((element) => !element.hasAttribute('hidden'));
  }

  private toNodeView(node: SystemsMapNode, locale: AppLocale): SystemsMapNodeView {
    const copy = this.copy();
    const label = node.label[locale];
    const labelLines = node.labelLines[locale];
    const summary = node.summary[locale];
    const gist = node.gist[locale];
    const relationship = node.relationships[locale];
    const multiline = labelLines.length > 1;
    const longest = labelLines.reduce((max, line) => Math.max(max, line.length), 0);
    const linkPattern = node.kind === 'project' ? copy.caseLinkPattern : copy.sectionLinkPattern;

    return {
      id: node.id,
      kind: node.kind,
      routeId: node.routeId,
      fragment: node.fragment,
      x: node.x,
      y: node.y,
      label,
      labelLines,
      summary,
      gist,
      shapeWidth: Math.max(160, longest * 9 + 32),
      shapeHeight: multiline ? 52 : 40,
      textStartDy: multiline ? -6 : 4,
      href: nodeHref(node, locale),
      link: this.navigation.link(node.routeId),
      relationship,
      accessibleName: `${label}. ${summary} ${relationship}`,
      linkLabel: linkPattern.replace('{node}', label),
    };
  }

  private neighborSet(id: SystemsMapNodeId): ReadonlySet<SystemsMapNodeId> {
    return new Set(connectedNodeIds(id));
  }
}