import {
  ChangeDetectionStrategy,
  Component,
  booleanAttribute,
  computed,
  Injector,
  inject,
  input,
  model,
  output,
  signal,
  viewChild,
} from '@angular/core';
import { SlLookupApi } from '../../core/sl/sl-lookup';
import { ValueHelp } from '../value-help/value-help';
import type { VhLookup, VhRow } from '../value-help/value-help.types';
import { TextInput } from './controls';
import { FieldBase } from './field-base';
import { SboField } from './sbo-field';

/**
 * Campo con botón "…" que abre una lista de valores (flecha dorada de SAP).
 * Escribir el código a mano también es válido; elegir de la lista lo rellena y emite `picked`.
 */
@Component({
  selector: 'sbo-lookup-field',
  changeDetection: ChangeDetectionStrategy.OnPush,
  imports: [SboField, TextInput, ValueHelp],
  template: `
    <sbo-field
      [label]="label()"
      [required]="required()"
      [error]="error() || missingText()"
      action
      [linkable]="linkable()"
      (labelClick)="linkClick.emit()"
    >
      <sbo-input
        #box
        [(value)]="value"
        [readonly]="readOnly()"
        [disabled]="disabled()"
        [required]="required()"
        (keydown.f4)="$event.preventDefault(); openList()"
        (focusout)="resolveTyped()"
      />
      <button
        type="button"
        class="sbo-btn"
        title="Lista de valores (F4)"
        [attr.aria-label]="'Abrir la lista de ' + label()"
        [disabled]="readOnly() || disabled()"
        (click)="openList()"
      >
        …
      </button>
    </sbo-field>
    <sbo-value-help
      [open]="listOpen()"
      [title]="lookup().title"
      [resource]="lookup().resource"
      [columns]="lookup().columns"
      [baseFilter]="lookup().baseFilter"
      [orderby]="lookup().orderby"
      [extraFields]="lookup().extraFields ?? []"
      (selected)="onPicked($event)"
      (closed)="closeList()"
    />
  `,
  styles: ':host { display: block; }',
})
export class LookupField extends FieldBase {
  readonly value = model('');
  readonly lookup = input.required<VhLookup>();
  /** La etiqueta abre el objeto enlazado (evento `linkClick`). */
  readonly linkable = input(false, { transform: booleanAttribute });

  /** Al salir del campo con un código escrito a mano, lo busca en la lista (como si se hubiera elegido). */
  readonly resolveOnLeave = input(false, { transform: booleanAttribute });

  readonly picked = output<VhRow>();
  readonly linkClick = output<void>();

  protected readonly listOpen = signal(false);
  /** Código que no existe; el aviso desaparece en cuanto el texto cambia. */
  private readonly missing = signal<{ code: string; text: string } | null>(null);
  protected readonly missingText = computed(() => {
    const m = this.missing();
    return m && m.code === this.value().trim() ? m.text : '';
  });
  private readonly injector = inject(Injector);
  /** Último código ya resuelto, para no repetir la consulta al salir y volver a entrar sin cambios. */
  private resolved = '';
  private readonly box = viewChild.required<TextInput>('box');

  protected openList(): void {
    if (!this.readOnly() && !this.disabled()) this.listOpen.set(true);
  }

  protected closeList(): void {
    this.listOpen.set(false);
    this.box().focus();
  }

  protected onPicked(rows: VhRow[]): void {
    const row = rows[0];
    if (!row) return;
    this.apply(row);
  }

  private apply(row: VhRow): void {
    const key = this.lookup().valueKey ?? this.lookup().columns[0]?.key ?? '';
    this.missing.set(null);
    this.value.set(String(row[key] ?? ''));
    this.resolved = this.value();
    this.picked.emit(row);
  }

  protected async resolveTyped(): Promise<void> {
    const code = this.value().trim();
    if (!this.resolveOnLeave() || this.readOnly() || this.disabled() || this.listOpen()) return;
    if (!code) {
      this.missing.set(null);
      this.resolved = '';
      return;
    }
    if (code === this.resolved) return;
    try {
      const row = await this.injector.get(SlLookupApi).find(this.lookup(), code);
      if (this.value().trim() !== code) return; // el usuario siguió escribiendo
      if (row) this.apply(row);
      else this.missing.set({ code, text: `No existe «${code}» en ${this.lookup().title.toLowerCase()}.` });
    } catch {
      this.missing.set({ code, text: 'No se pudo comprobar el código.' });
    }
  }
}