import {
  ChangeDetectionStrategy,
  Component,
  computed,
  inject,
  input,
  output,
  signal,
} from '@angular/core';
import { DOCUMENT } from '@angular/common';
import {
  PiActionButtonComponent,
  PiIconButtonComponent,
  PiSegmentedControlComponent,
  type SegmentedControlOption,
} from '@pi/ui';

import { AppearanceService } from '../core/appearance';

import type { Copy } from '../core/copy';
import type { Locale, SitePayload } from '../core/api';

/**
 * A section of the landing (`anchor`) or another address altogether (`href`),
 * such as one of the pages the panel publishes.
 */
export interface NavLink {
  label: string;
  anchor?: string;
  href?: string;
}

@Component({
  selector: 'app-site-header',
  changeDetection: ChangeDetectionStrategy.OnPush,
  imports: [
    PiActionButtonComponent,
    PiIconButtonComponent,
    PiSegmentedControlComponent,
  ],
  styleUrl: './site-header.scss',
  template: `
    <header class="landing-header">
      <div class="landing-shell landing-header__inner">
        <a class="landing-brand" [href]="brandHref()">
          <img
            class="landing-brand__mark"
            src="/logo.png"
            alt=""
            width="256"
            height="256"
            decoding="async"
          />
          <span>Pireon</span>
        </a>

        <nav class="landing-header__nav" aria-label="Principal">
          @for (link of links(); track link.label) {
            <a [href]="hrefOf(link)">{{ link.label }}</a>
          }
        </nav>

        <div class="landing-header__actions">
          @if (localeOptions().length > 1) {
            <pi-segmented-control
              class="landing-header__locales"
              ariaLabel="Idioma"
              [options]="localeOptions()"
              [value]="locale()"
              (valueChange)="switchLocale($event)"
            />
          }


          <pi-icon-button
            class="landing-header__appearance"
            iconType="custom"
            color="grey"
            [icon]="appearance.dark() ? 'sun' : 'moon'"
            [attr.aria-label]="
              appearance.dark() ? copy().nav.lightMode : copy().nav.darkMode
            "
            [attr.aria-pressed]="appearance.dark()"
            (execute)="appearance.toggle()"
          />

          <pi-action-button
            class="landing-header__cta"
            color="primary"
            [text]="copy().nav.contact"
            (execute)="navigate.emit('#contacto')"
          />

          <button
            type="button"
            class="landing-header__toggle"
            aria-label="Menú"
            [attr.aria-expanded]="open()"
            aria-controls="mobile-nav"
            (click)="open.set(!open())"
          >
            <span></span><span></span><span></span>
          </button>
        </div>
      </div>

      @if (open()) {
        <nav id="mobile-nav" class="landing-header__mobile">
          <div class="landing-shell">
            @for (link of links(); track link.label) {
              <a [href]="hrefOf(link)" (click)="open.set(false)">{{
                link.label
              }}</a>
            }

            <!--
              The segmented control is hidden on this width, so the languages
              come back here as plain links rather than being unreachable on a
              phone.
            -->
            <button
              type="button"
              class="landing-header__mobile-appearance"
              [attr.aria-pressed]="appearance.dark()"
              (click)="appearance.toggle()"
            >
              {{ appearance.dark() ? copy().nav.lightMode : copy().nav.darkMode }}
            </button>

            @if (locales().length > 1) {
              <div class="landing-header__mobile-locales">
                @for (option of locales(); track option.code) {
                  <a
                    [href]="localeHref(option.code)"
                    [attr.hreflang]="option.code"
                    [attr.aria-current]="option.code === locale() ? 'true' : null"
                    [class.is-active]="option.code === locale()"
                    >{{ option.code.toUpperCase() }}</a
                  >
                }
              </div>
            }
          </div>
        </nav>
      }
    </header>
  `,
})
export class SiteHeader {
  readonly copy = input.required<Copy>();
  readonly locale = input.required<Locale>();
  readonly links = input.required<NavLink[]>();
  readonly locales = input.required<SitePayload['locales']>();
  /** Where the logo leads: the top of the landing when on it, the landing itself elsewhere. */
  readonly brandHref = input('#top');
  /**
   * The same page in each language, as the API's `alternates` spells it. Null
   * on the landing, which answers on `?lang=` instead. A language missing from
   * it has no translation of this page, so the switcher leads to the landing
   * in that language rather than to a 404.
   */
  readonly alternates = input<Partial<Record<string, string>> | null>(null);

  readonly navigate = output<string>();

  protected readonly appearance = inject(AppearanceService);
  private readonly document = inject(DOCUMENT);

  protected readonly open = signal(false);

  protected readonly localeOptions = computed<SegmentedControlOption<Locale>[]>(
    () =>
      this.locales().map((option) => ({
        value: option.code as Locale,
        label: option.code.toUpperCase(),
      }))
  );

  /**
   * A full navigation rather than a client-side one: the page's content is
   * resolved from `?lang=` on the server, so the server has to render it again.
   */
  protected switchLocale(next: Locale | undefined): void {
    if (!next || next === this.locale()) {
      return;
    }

    this.document.defaultView?.location.assign(this.localeHref(next));
  }

  protected localeHref(code: string): string {
    return this.alternates()?.[code] ?? `/?lang=${code}`;
  }

  protected hrefOf(link: NavLink): string {
    return link.href ?? `#${link.anchor}`;
  }
}