import { HttpClient, HttpErrorResponse } from '@angular/common/http';
import {
  afterNextRender,
  ChangeDetectionStrategy,
  Component,
  computed,
  inject,
  input,
  signal,
} from '@angular/core';
import {
  applyWhen,
  email,
  form,
  FormField,
  minLength,
  required,
  submit,
} from '@angular/forms/signals';
import {
  PiActionButtonComponent,
  PiCheckboxComponent,
  PiEmailFieldComponent,
  PiLabelDirective,
  PiNoteComponent,
  PiNumberFieldComponent,
  PiSegmentedControlComponent,
  PiTextareaComponent,
  PiTextFieldComponent,
  PiTextXSmallDirective,
  type SegmentedControlOption,
} from '@pi/ui';

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

type FormState = 'idle' | 'sending' | 'sent' | 'duplicate' | 'error';
type Kind = 'contribute' | 'request';

/**
 * The public API's write path, reached through this app's own `/api/contact`
 * handler rather than directly: the API throttles per e-mail address on the
 * assumption that an SSR frontend posts on the visitor's behalf, and going
 * through the server keeps the API host out of the browser.
 *
 * The fields are `@pi/ui`'s, which implement Signal Forms' control contracts —
 * `[formField]` wires value, disabled, errors, touched and required, so none of
 * those may be bound by hand here (Angular rejects it with NG8022).
 */
@Component({
  selector: 'app-contact-form',
  changeDetection: ChangeDetectionStrategy.OnPush,
  imports: [
    FormField,
    PiTextFieldComponent,
    PiEmailFieldComponent,
    PiTextareaComponent,
    PiNumberFieldComponent,
    PiCheckboxComponent,
    PiSegmentedControlComponent,
    PiActionButtonComponent,
    PiLabelDirective,
    PiNoteComponent,
    PiTextXSmallDirective,
  ],
  styleUrl: './contact-form.scss',
  template: `
    @if (!enabled()) {
      <pi-note
        status="info"
        appearance="fill"
        gap="xs"
        [title]="copy().form.closed"
        [text]="''"
      />
    } @else if (state() === 'sent' || state() === 'duplicate') {
      <pi-note
        status="success"
        appearance="fill"
        gap="xs"
        role="status"
        [title]="copy().sections.contact.title"
        [text]="receiptMessage()"
      />
    } @else {
      <form class="landing-form" (ngSubmit)="send()" novalidate>
        <!-- An application to a call is always an offer of time. -->
        @if (!callSlug()) {
          <fieldset class="landing-form__kind">
            <legend>{{ copy().form.kind }}</legend>
            <pi-segmented-control
              [ariaLabel]="copy().form.kind"
              [options]="kinds()"
              [(value)]="kind"
            />
          </fieldset>
        }

        <div class="landing-form__row">
          <pi-text-field [formField]="contact.name" [placeholder]="copy().form.name">
            <pi-label [isRequired]="true">{{ copy().form.name }}</pi-label>
          </pi-text-field>

          <pi-email-field
            [formField]="contact.email"
            [placeholder]="copy().form.email"
          >
            <pi-label [isRequired]="true">{{ copy().form.email }}</pi-label>
          </pi-email-field>
        </div>

        <div class="landing-form__row">
          @if (kind() === 'request') {
            <pi-text-field
              [formField]="contact.organisation"
              [placeholder]="copy().form.organisation"
            >
              <pi-label [isRequired]="true">{{ copy().form.organisation }}</pi-label>
            </pi-text-field>
          } @else {
            <!--
              The placeholder is not decoration. Without one, Material leaves
              this label in its unfloated position and writes an inline
              translateY(-50%) that drops the text straight onto the outline's
              top border, struck through by it. Every other field here has a
              placeholder, which is why this was the only one that looked wrong.
            -->
            <pi-number-field
              [formField]="contact.hours_per_week"
              [placeholder]="copy().form.hoursHint"
            >
              <pi-label>{{ copy().form.hours }}</pi-label>
            </pi-number-field>
          }
        </div>

        <pi-textarea
          [formField]="contact.message"
          [placeholder]="copy().form.messageHint"
        >
          <pi-label [isRequired]="true">{{ copy().form.message }}</pi-label>
        </pi-textarea>

        <!--
          Honeypot. Never rendered visibly and never focusable: a submission
          carrying it is filed as spam upstream and still answers 201, so a bot
          learns nothing from the response.
        -->
        <div class="visually-hidden" aria-hidden="true">
          <label>
            Website
            <input
              type="text"
              tabindex="-1"
              autocomplete="off"
              [value]="website()"
              (input)="website.set($any($event.target).value)"
            />
          </label>
        </div>

        <pi-checkbox [formField]="contact.consent" [label]="copy().form.consent" />

        @if (state() === 'error') {
          <p xs role="alert" class="landing-form__error">{{ errorMessage() }}</p>
        }

        <pi-action-button
          size="large"
          color="primary"
          [text]="state() === 'sending' ? copy().form.sending : copy().form.submit"
          [disabled]="!hydrated() || state() === 'sending'"
          (execute)="send()"
        />
      </form>
    }
  `,
})
export class ContactForm {
  readonly copy = input.required<Copy>();
  readonly locale = input.required<Locale>();
  readonly enabled = input(true);
  /** Set, the form applies to that call instead of writing in generally. */
  readonly callSlug = input<string | null>(null);

  private readonly http = inject(HttpClient);

  protected readonly state = signal<FormState>('idle');
  private readonly receipt = signal<SubmissionReceipt | null>(null);

  /**
   * The page is server-rendered, so for a moment the form is real HTML with no
   * listener on it: a click in that window submits natively, navigates away,
   * and takes the visitor's message with it. The button waits for hydration.
   */
  protected readonly hydrated = signal(false);

  /** Not part of the form: a bot filling it must not fail validation. */
  protected readonly website = signal('');

  /** Drives which second field is shown, and whether `organisation` is required. */
  protected readonly kind = signal<Kind>('contribute');

  private readonly model = signal({
    name: '',
    email: '',
    organisation: '',
    hours_per_week: null as number | null,
    message: '',
    consent: false,
  });

  /**
   * Every rule is gated on the field having been touched.
   *
   * `@pi/ui`'s fields derive their error state from `errors().length` alone —
   * `touched` is not part of it — so an untouched empty form would render red
   * borders and "falta el nombre" before the visitor typed a character. Adding
   * the rules only once a field has been left keeps that away, and `submit()`
   * marks the whole tree touched before it checks validity, so an empty form
   * still cannot be sent.
   */
  protected readonly contact = form(this.model, (field) => {
    const touched = (ctx: { state: { touched: () => boolean } }) =>
      ctx.state.touched();

    applyWhen(field.name, touched, (name) => {
      required(name, { message: 'Falta el nombre' });
      minLength(name, 2, { message: 'Nombre demasiado corto' });
    });

    applyWhen(field.email, touched, (address) => {
      required(address, { message: 'Falta el correo' });
      email(address, { message: 'Correo no válido' });
    });

    applyWhen(field.message, touched, (message) => {
      required(message, { message: 'Falta el mensaje' });
      // The API rejects anything shorter, and rightly: a one-word submission
      // is never anything but noise.
      minLength(message, 20, { message: 'Mínimo 20 caracteres' });
    });

    applyWhen(field.consent, touched, (consent) => {
      required(consent, { message: 'Hace falta tu consentimiento' });
    });

    // Only an organisation asking for help has to name itself.
    applyWhen(field.organisation, touched, (organisation) => {
      required(organisation, {
        when: () => this.kind() === 'request',
        message: 'Falta la organización',
      });
    });
  });

  protected readonly kinds = computed<SegmentedControlOption<Kind>[]>(() => [
    { value: 'contribute', label: this.copy().form.kindContribute },
    { value: 'request', label: this.copy().form.kindRequest },
  ]);

  protected readonly receiptMessage = computed(
    () =>
      this.receipt()?.message ??
      (this.state() === 'duplicate'
        ? this.copy().form.duplicate
        : this.copy().form.success)
  );

  protected readonly errorMessage = computed(() => {
    const errors = this.receipt()?.errors;
    const first = errors ? Object.values(errors)[0]?.[0] : null;

    return first ?? this.copy().form.error;
  });

  constructor() {
    afterNextRender(() => this.hydrated.set(true));
  }

  protected send(): void {
    // `submit()` marks the tree touched and only runs the action when valid,
    // so there is no separate "have they tried yet" flag to keep.
    void submit(this.contact, {
      action: async () => {
        const value = this.model();

        this.state.set('sending');
        this.receipt.set(null);

        const payload = {
          ...value,
          kind: this.kind(),
          organisation: value.organisation || null,
          website: this.website() || null,
        };

        try {
          const body = await this.post(payload);

          this.receipt.set(body);
          this.state.set(body.data?.duplicate ? 'duplicate' : 'sent');
        } catch (error) {
          this.receipt.set((error as HttpErrorResponse).error as SubmissionReceipt);
          this.state.set('error');
        }

        return undefined;
      },
    });
  }

  private endpoint(): string {
    const slug = this.callSlug();
    const path = slug ? `/api/calls/${encodeURIComponent(slug)}/apply` : '/api/contact';

    return `${path}?lang=${this.locale()}`;
  }

  private post(payload: unknown): Promise<SubmissionReceipt> {
    return new Promise((resolve, reject) => {
      this.http
        .post<SubmissionReceipt>(this.endpoint(), payload)
        .subscribe({ next: resolve, error: reject });
    });
  }
}