/**
 * Copyright since 2025 Mifos Initiative
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 */

import {
  Component,
  EventEmitter,
  Input,
  OnChanges,
  OnDestroy,
  OnInit,
  Output,
  SimpleChanges,
  inject
} from '@angular/core';
import {
  AbstractControl,
  FormGroupDirective,
  NgForm,
  UntypedFormBuilder,
  UntypedFormGroup,
  Validators
} from '@angular/forms';
import { ErrorStateMatcher } from '@angular/material/core';
import { Router } from '@angular/router';
import { MatIcon } from '@angular/material/icon';
import { MatProgressSpinner } from '@angular/material/progress-spinner';
import { Observable, Subject, merge, of } from 'rxjs';
import { catchError, debounceTime, map, switchMap, takeUntil, tap } from 'rxjs/operators';
import { STANDALONE_SHARED_IMPORTS } from 'app/standalone-shared.module';
import { AuthenticationService } from 'app/core/authentication/authentication.service';
import { RestrictInputDirective } from '../../../directives/restrict-input.directive';
import { ClientsService } from '../../clients.service';
import { ClientIdentityLookupResult, ClientIdentityMatch } from '../../models/client-identity.model';
import { aadhaarHash } from '../../utils/aadhaar-hash.util';

export type ClientIdentityStatus = 'idle' | 'checking' | 'not-found' | 'matched' | 'conflict' | 'error';

/**
 * What the parent needs from the identity check: whether creation must stop, and the identifiers the officer entered
 * so the KYC step can be filled in without typing them again.
 */
export interface ClientIdentityState {
  status: ClientIdentityStatus;
  /** Individual: the person's PAN. Entity: the company's PAN. */
  pan: string | null;
  /** The 12 digits, held in memory only to pre-fill the KYC step. Never sent: only its hash is. */
  aadhaar: string | null;
  gstin: string | null;
  /** True when the customer already exists (or the identifiers disagree), so a new client must not be created. */
  blocking: boolean;
}

/**
 * Shows a field's error as soon as something has been typed in it, not only after the field is left: a PAN that is
 * wrong should say so while it is being typed, and the form should not look fine in the meantime.
 */
class ShowErrorWhenDirty implements ErrorStateMatcher {
  isErrorState(control: AbstractControl | null, _form: FormGroupDirective | NgForm | null): boolean {
    return !!control && control.invalid && (control.dirty || control.touched);
  }
}

const PAN_PATTERN = /^[A-Za-z]{5}\d{4}[A-Za-z]$/;
const AADHAAR_PATTERN = /^\d{12}$/;
const GSTIN_PATTERN = /^\d{2}[A-Za-z]{5}\d{4}[A-Za-z][1-9A-Za-z]Z[0-9A-Za-z]$/;

/**
 * "Is this person already a customer of the bank?" — asked at the top of the General step, before anything is saved.
 *
 * Any ONE of PAN / Aadhaar (individual) or PAN / GSTIN (entity) matching an existing customer, in any branch, means
 * the same customer, so a second client must not be created. When nothing matches, what was entered is carried to the
 * KYC step so it does not have to be typed again.
 */
@Component({
  selector: 'mifosx-client-identity-check',
  templateUrl: './client-identity-check.component.html',
  styleUrls: ['./client-identity-check.component.scss'],
  imports: [
    ...STANDALONE_SHARED_IMPORTS,
    MatIcon,
    MatProgressSpinner,
    RestrictInputDirective
  ]
})
export class ClientIdentityCheckComponent implements OnInit, OnChanges, OnDestroy {
  private formBuilder = inject(UntypedFormBuilder);
  private clientsService = inject(ClientsService);
  private router = inject(Router);
  private authenticationService = inject(AuthenticationService);

  /** 1 = individual, 2 = entity (non-individual). */
  @Input() legalFormType = 1;
  @Output() identityChange = new EventEmitter<ClientIdentityState>();

  form: UntypedFormGroup;
  readonly errorMatcher = new ShowErrorWhenDirty();
  status: ClientIdentityStatus = 'idle';
  matches: ClientIdentityMatch[] = [];
  /** True while the customer is being introduced to this branch. */
  linking = false;

  private destroy$ = new Subject<void>();
  private recheck$ = new Subject<void>();

  get isEntity(): boolean {
    return this.legalFormType === 2;
  }

  /** The first (and normally only) existing customer found. */
  get match(): ClientIdentityMatch | null {
    return this.matches[0] ?? null;
  }

  /**
   * True while a field holds something that is not a valid PAN / Aadhaar / GSTIN. Such a value is never looked up or
   * carried to the KYC step, so the parent must not let the officer carry on past it as if the check had passed.
   */
  get hasInvalidInput(): boolean {
    return !!this.form?.invalid;
  }

  markAllAsTouched(): void {
    this.form?.markAllAsTouched();
  }

  get state(): ClientIdentityState {
    const v = this.normalized();
    return {
      status: this.status,
      pan: v.pan,
      aadhaar: v.aadhaar,
      gstin: v.gstin,
      blocking: this.status === 'matched' || this.status === 'conflict'
    };
  }

  ngOnInit(): void {
    this.form = this.formBuilder.group({
      pan: [
        '',
        Validators.pattern(PAN_PATTERN)
      ],
      aadhaar: [
        '',
        Validators.pattern(AADHAAR_PATTERN)
      ],
      gstin: [
        '',
        Validators.pattern(GSTIN_PATTERN)
      ]
    });

    // A pause in typing (or a manual re-check) runs one lookup; typing again cancels the one in flight.
    merge(this.form.valueChanges, this.recheck$)
      .pipe(
        debounceTime(400),
        tap(() => this.startChecking()),
        switchMap(() => this.lookup()),
        takeUntil(this.destroy$)
      )
      .subscribe((result) => this.applyResult(result));
  }

  ngOnChanges(changes: SimpleChanges): void {
    // Switching individual <-> entity swaps which identifiers apply; what was typed for the other kind is stale.
    if (changes['legalFormType'] && !changes['legalFormType'].firstChange) {
      this.reset();
    }
  }

  ngOnDestroy(): void {
    this.destroy$.next();
    this.destroy$.complete();
  }

  /** Clears the fields and the result, e.g. when a new client creation session starts. */
  reset(): void {
    this.form?.reset({ pan: '', aadhaar: '', gstin: '' }, { emitEvent: false });
    this.status = 'idle';
    this.matches = [];
    this.identityChange.emit(this.state);
  }

  recheck(): void {
    this.recheck$.next();
  }

  /**
   * PAN and GSTIN are always written in capitals, so what is typed is capitalised as it is typed. The caret is put
   * back where it was, otherwise editing the middle of a PAN would throw it to the end. The shared restrict-input
   * directive only capitalises when the field is left, which let lower-case show while typing.
   */
  capitalise(controlName: 'pan' | 'gstin', event: Event): void {
    const input = event.target as HTMLInputElement;
    const upper = input.value.toUpperCase();
    if (upper !== input.value) {
      const { selectionStart, selectionEnd } = input;
      input.value = upper;
      input.setSelectionRange(selectionStart, selectionEnd);
    }
    this.form.get(controlName)?.setValue(upper, { emitEvent: false });
  }

  /** Identifiers that are complete and well formed; anything half-typed is ignored rather than looked up. */
  private normalized(): { pan: string | null; aadhaar: string | null; gstin: string | null } {
    const raw = this.form?.getRawValue() ?? { pan: '', aadhaar: '', gstin: '' };
    const pan = String(raw.pan ?? '')
      .replace(/\s+/g, '')
      .toUpperCase();
    const aadhaar = String(raw.aadhaar ?? '').replace(/[\s-]/g, '');
    const gstin = String(raw.gstin ?? '')
      .replace(/\s+/g, '')
      .toUpperCase();
    return {
      pan: PAN_PATTERN.test(pan) ? pan : null,
      aadhaar: !this.isEntity && AADHAAR_PATTERN.test(aadhaar) ? aadhaar : null,
      gstin: this.isEntity && GSTIN_PATTERN.test(gstin) ? gstin : null
    };
  }

  private startChecking(): void {
    const v = this.normalized();
    if (!v.pan && !v.aadhaar && !v.gstin) {
      this.status = 'idle';
      this.matches = [];
      this.identityChange.emit(this.state);
      return;
    }
    this.status = 'checking';
    this.matches = [];
    this.identityChange.emit(this.state);
  }

  private lookup(): Observable<ClientIdentityLookupResult | 'error' | null> {
    const v = this.normalized();
    if (!v.pan && !v.aadhaar && !v.gstin) {
      return of(null);
    }
    return this.clientsService
      .lookupClientIdentity({ panNumber: v.pan, aadhaarHash: aadhaarHash(v.aadhaar), gstinNumber: v.gstin })
      .pipe(
        map((result): ClientIdentityLookupResult | 'error' => result),
        catchError(() => of('error' as const))
      );
  }

  private applyResult(result: ClientIdentityLookupResult | 'error' | null): void {
    if (result === null) {
      // Nothing complete to look up; startChecking() already reset to idle.
      return;
    }
    if (result === 'error') {
      // Not blocking: the server checks again when the KYC is saved, so a failed lookup must not stop onboarding.
      this.status = 'error';
      this.matches = [];
    } else if (result.conflict) {
      this.status = 'conflict';
      this.matches = result.matches;
    } else if (result.matched) {
      this.status = 'matched';
      this.matches = result.matches;
    } else {
      this.status = 'not-found';
      this.matches = [];
    }
    this.identityChange.emit(this.state);
  }

  /**
   * Starts opening an account at THIS branch for a customer registered at another one. The customer stays at the home
   * branch (one CIF). This branch is introduced to them, which only lets it open their page; they are listed under
   * this branch once an account is actually opened here. An account opened for a customer of another branch is held
   * at the branch that opens it.
   */
  openAccountHere(match: ClientIdentityMatch): void {
    const officeId = this.authenticationService.getCredentials()?.officeId;
    if (this.linking || officeId == null) {
      return;
    }
    this.linking = true;
    this.clientsService.linkClientToMyBranch(match.clientId).subscribe({
      next: () => {
        this.linking = false;
        this.router.navigate([
          '/clients',
          match.clientId,
          'general'
        ]);
      },
      // The failure is shown by the global error handler.
      error: () => (this.linking = false)
    });
  }

  /** Legal form of the existing customer, for the card. */
  legalFormLabel(match: ClientIdentityMatch): string {
    return match.legalFormEnum === 2 ? 'Non-Individual' : 'Individual';
  }

  matchedByLabel(by: string): string {
    return by === 'AADHAAR' ? 'Aadhaar' : by;
  }
}