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

/** Rough per-item metrics in REM, used only to decide whether the menu must
 *  flip. Converted through remPx() at open time so the math tracks the same
 *  root font-size the CSS scales with — the old px constants (`MENU_W = 224`)
 *  were 16px-root mirrors of rem classes, so the box grew with the interface
 *  scale while the flip math still believed 224 and fired at the wrong edge. */
const ITEM_H_REM = 1.625; // px-3 py-1 row + --path-font line ≈ 26px @16
const SEPARATOR_H_REM = 0.4375; // my-1 + 1px border ≈ 7px @16
const MENU_W_REM = 14; // w-56
const EDGE_GAP = 6; // px on purpose: a viewport-edge margin, not a UI size

/**
 * 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($event)"></div>
      <div
        #menuEl
        role="menu"
        tabindex="-1"
        [attr.aria-activedescendant]="activeIndex() >= 0 ? 'ctx-item-' + activeIndex() : null"
        (keydown)="onKeydown($event)"
        [style.left.px]="position().x"
        [style.top.px]="position().y"
        class="fixed z-50 w-56 border border-border/60 bg-chrome py-1 text-foreground shadow-xl outline-none"
      >
        @for (item of req.items; track $index) {
          @if (item.type === 'separator') {
            <div class="my-1 border-t border-border/60"></div>
          } @else {
            <button
              type="button"
              role="menuitem"
              [attr.id]="'ctx-item-' + $index"
              [title]="item.tooltip ?? ''"
              [disabled]="!!item.disabled"
              [class.bg-primary-surface]="$index === activeIndex() && !item.disabled"
              [class.text-primary]="$index === activeIndex() && !item.disabled"
              (mouseenter)="activeIndex.set($index)"
              (click)="pick(item)"
              class="flex w-full items-center gap-2 px-3 py-1 text-left text-(length:--path-font) disabled:pointer-events-none disabled:opacity-50"
            >
              <span class="w-3.5 shrink-0">
                @if (item.checked) {
                  <ng-icon name="tdesignCheck" 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.
   *  All UI metrics convert through the live root font-size; window.inner* is
   *  viewport CSS px, so both sides of every comparison share units. */
  readonly position = computed(() => {
    const req = this.menu.request();
    if (!req) return { x: 0, y: 0 };
    const itemH = remPx(ITEM_H_REM);
    const separatorH = remPx(SEPARATOR_H_REM);
    const menuW = remPx(MENU_W_REM);
    const height =
      req.items.reduce((sum, i) => sum + (i.type === 'separator' ? separatorH : itemH), 0) +
      remPx(0.5); // the menu's py-1 (0.25rem x2)
    const x =
      req.x + menuW > window.innerWidth - EDGE_GAP ? Math.max(EDGE_GAP, req.x - menuW) : 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 {
    // the keyboard path never consults the disabled attribute — guard here
    if (item.disabled) return;
    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 (see stepIndex). */
  private step(items: MenuItem[], delta: 1 | -1): void {
    const selectable = items.map((i) => i.type !== 'separator' && !i.disabled);
    this.activeIndex.set(stepIndex(selectable, this.activeIndex(), delta));
  }
}