import {
  Component,
  ElementRef,
  computed,
  effect,
  inject,
  signal,
  viewChild,
} from '@angular/core';
import { NgIcon } from '@ng-icons/core';
import { ContextMenuService, type MenuItem } from './context-menu.service';
import { FocusService } from './focus.service';

/** Rough per-item metrics, used only to decide whether the menu must flip. */
const ITEM_H = 26;
const SEPARATOR_H = 7;
const MENU_W = 224; // w-56
const EDGE_GAP = 6;

/**
 * The panel right-click menu. Replaces electrobun's native ContextMenu, which
 * is a no-op on Linux — see ContextMenuService for the why. Emits the same
 * `ctx-*` / `col:*` action strings the native menu did.
 */
@Component({
  selector: 'app-context-menu',
  imports: [NgIcon],
  template: `
    @if (menu.request(); as req) {
      <!-- click-outside catcher; mousedown so it beats the panel's own handlers -->
      <div class="fixed inset-0 z-50" (mousedown)="close()" (contextmenu)="onBackdropContext($event)"></div>
      <div
        #menuEl
        role="menu"
        tabindex="-1"
        (keydown)="onKeydown($event)"
        [style.left.px]="position().x"
        [style.top.px]="position().y"
        class="w7-menu fixed z-50 w-56 rounded-lg border border-border bg-card py-1 text-card-foreground shadow-xl outline-none"
      >
        @for (item of req.items; track $index) {
          @if (item.type === 'separator') {
            <div class="w7-menu-sep my-1 border-t border-border"></div>
          } @else {
            <button
              type="button"
              role="menuitem"
              [title]="item.tooltip ?? ''"
              [class.bg-accent]="$index === activeIndex()"
              (mouseenter)="activeIndex.set($index)"
              (click)="pick(item)"
              class="flex w-full items-center gap-2 px-3 py-1 text-left text-(length:--path-font) hover:bg-accent"
            >
              <span class="w-3.5 shrink-0">
                @if (item.checked) {
                  <ng-icon name="mynaCheck" size="0.85rem" class="text-primary" />
                }
              </span>
              <span class="flex-1 truncate">{{ item.label }}</span>
              @if (item.accelerator) {
                <span class="shrink-0 text-muted-foreground">{{ item.accelerator }}</span>
              }
            </button>
          }
        }
      </div>
    }
  `,
  // Closing on scroll/blur matches native menu behavior: the anchor row moves
  // out from under a menu that would otherwise float over stale content.
  host: {
    '(window:blur)': 'close()',
    '(window:resize)': 'close()',
    '(document:scroll)': 'close()',
  },
})
export class ContextMenu {
  readonly menu = inject(ContextMenuService);
  private readonly focus = inject(FocusService);
  private readonly menuEl = viewChild<ElementRef<HTMLDivElement>>('menuEl');

  readonly activeIndex = signal(-1);

  /** Click point, flipped/clamped so the menu never overflows the viewport. */
  readonly position = computed(() => {
    const req = this.menu.request();
    if (!req) return { x: 0, y: 0 };
    const height =
      req.items.reduce((sum, i) => sum + (i.type === 'separator' ? SEPARATOR_H : ITEM_H), 0) + 8;
    const x =
      req.x + MENU_W > window.innerWidth - EDGE_GAP
        ? Math.max(EDGE_GAP, req.x - MENU_W)
        : req.x;
    const y =
      req.y + height > window.innerHeight - EDGE_GAP
        ? Math.max(EDGE_GAP, req.y - height)
        : req.y;
    return { x, y };
  });

  constructor() {
    // Focus the menu once it exists so arrow keys / Escape reach it. Keyed on
    // the viewChild signal, NOT on request(): under zoneless CD an effect can
    // run before the @if has rendered the element.
    effect(() => this.menuEl()?.nativeElement.focus());
  }

  close(): void {
    if (!this.menu.request()) return;
    this.menu.close();
    this.activeIndex.set(-1); // a fresh menu starts with nothing highlighted
    this.focus.bump();
  }

  pick(item: MenuItem): void {
    if (!item.action) return;
    const action = item.action;
    this.close();
    this.menu.onPick(action);
  }

  /** Right-clicking the backdrop closes rather than stacking a second menu. */
  onBackdropContext(event: MouseEvent): void {
    event.preventDefault();
    this.close();
  }

  onKeydown(event: KeyboardEvent): void {
    const items = this.menu.request()?.items ?? [];
    switch (event.key) {
      case 'Escape':
        event.preventDefault();
        event.stopPropagation();
        this.close();
        break;
      case 'ArrowDown':
        event.preventDefault();
        this.step(items, 1);
        break;
      case 'ArrowUp':
        event.preventDefault();
        this.step(items, -1);
        break;
      case 'Enter':
      case ' ': {
        event.preventDefault();
        const item = items[this.activeIndex()];
        if (item) this.pick(item);
        break;
      }
    }
  }

  /** Move the highlight by one selectable item, skipping separators, wrapping. */
  private step(items: MenuItem[], delta: number): void {
    const count = items.length;
    if (!count) return;
    let index = this.activeIndex();
    for (let hops = 0; hops < count; hops++) {
      index = (index + delta + count) % count;
      if (items[index].type !== 'separator') {
        this.activeIndex.set(index);
        return;
      }
    }
  }
}