import { Component, ElementRef, computed, effect, inject, signal, viewChild } from '@angular/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 = 24; // 7.css: 4px padding x2 + ~15px line
const DIVIDER_H = 7; // .has-divider:after: 2px bevel + margins
const MENU_W = 200;
const EDGE_GAP = 6;

/** One rendered <li>: separators collapse onto the item BEFORE them. */
interface MenuRow {
  item: MenuItem;
  hasDivider: boolean;
}

/**
 * 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.
 *
 * The markup is 7.css's menu contract EXACTLY — `ul[role=menu] >
 * li[role=menuitem] > button` for actions, `> input[type=checkbox] + label`
 * for the checkable column toggles, and dividers as `.has-divider` on the
 * PRECEDING item (7.css draws them as an ::after bevel, not as a node). Get
 * any of that wrong and 7.css silently styles nothing: an earlier version
 * rendered div > button, concluded "7.css has no menu component", and
 * hand-built a lookalike. It does have one; the selectors just never matched.
 *
 * Keyboard follows the platform: arrows move REAL focus between items (7.css
 * styles :focus-visible identically to :hover), Enter/Space on a button
 * activate it natively; only labels need a synthetic click.
 */
@Component({
  selector: 'app-context-menu',
  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($event)"></div>
      <ul
        #menuEl
        role="menu"
        tabindex="-1"
        (keydown)="onKeydown($event)"
        [style.left.px]="position().x"
        [style.top.px]="position().y"
        [style.width.px]="menuWidth"
        class="fixed z-50 outline-none"
      >
        @for (row of rows(); track $index) {
          <li role="menuitem" [class.has-divider]="row.hasDivider" [title]="row.item.tooltip ?? ''">
            @if (row.item.checked !== undefined) {
              <input type="checkbox" [id]="'ctx-check-' + $index" [checked]="row.item.checked" tabindex="-1" />
              <label [for]="'ctx-check-' + $index" tabindex="-1" (click)="pick(row.item, $event)">
                {{ row.item.label }}
              </label>
            } @else {
              <button type="button" (click)="pick(row.item)">
                {{ row.item.label }}
                @if (row.item.accelerator) {
                  <span>{{ row.item.accelerator }}</span>
                }
              </button>
            }
          </li>
        }
      </ul>
    }
  `,
  // 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<HTMLUListElement>>('menuEl');

  protected readonly menuWidth = MENU_W;

  /** Model items → rendered rows: a separator becomes has-divider on its predecessor. */
  readonly rows = computed<MenuRow[]>(() => {
    const items = this.menu.request()?.items ?? [];
    const rows: MenuRow[] = [];
    for (const item of items) {
      if (item.type === 'separator') {
        if (rows.length) rows[rows.length - 1].hasDivider = true;
      } else {
        rows.push({ item, hasDivider: false });
      }
    }
    return rows;
  });

  /** 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 rows = this.rows();
    const height =
      rows.length * ITEM_H + rows.filter((r) => r.hasDivider).length * DIVIDER_H + 6;
    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.focus.bump();
  }

  pick(item: MenuItem, event?: Event): void {
    // labels: don't let the click also toggle the real checkbox — the fresh
    // `checked` state comes back through settings when the menu reopens
    event?.preventDefault();
    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 {
    switch (event.key) {
      case 'Escape':
        event.preventDefault();
        event.stopPropagation();
        this.close();
        break;
      case 'ArrowDown':
        event.preventDefault();
        this.step(1);
        break;
      case 'ArrowUp':
        event.preventDefault();
        this.step(-1);
        break;
      case 'Enter':
      case ' ': {
        // buttons activate natively from their own focus; labels don't, so
        // synthesize the click (which routes through pick via the template)
        const active = document.activeElement;
        if (active instanceof HTMLLabelElement && this.menuEl()?.nativeElement.contains(active)) {
          event.preventDefault();
          active.click();
        }
        break;
      }
    }
  }

  /**
   * Move REAL focus by one item, wrapping. 7.css styles :focus-visible the
   * same as :hover, and keyboard-initiated programmatic focus counts as
   * focus-visible, so the highlight comes from the framework for free.
   */
  private step(delta: number): void {
    const root = this.menuEl()?.nativeElement;
    if (!root) return;
    const targets = Array.from(root.querySelectorAll<HTMLElement>('li > button, li > label'));
    if (!targets.length) return;
    const current = targets.indexOf(document.activeElement as HTMLElement);
    const next = current < 0 && delta < 0 ? targets.length - 1 : (current + delta + targets.length) % targets.length;
    targets[next].focus();
  }
}