/**
 * 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/.
 */

/** Angular Imports */
import {
  Component,
  ElementRef,
  EventEmitter,
  Input,
  OnChanges,
  OnDestroy,
  Output,
  QueryList,
  SimpleChanges,
  ViewChildren,
  inject
} from '@angular/core';
import { UntypedFormControl } from '@angular/forms';
import { MatProgressSpinner } from '@angular/material/progress-spinner';
import { FaIconComponent } from '@fortawesome/angular-fontawesome';
import { STANDALONE_SHARED_IMPORTS } from 'app/standalone-shared.module';

/** Custom Services */
import { ClientsService } from '../../clients.service';

/** Emitted every time this block's verification result changes — including a reset back
 * to `{ otpId: null, verified: false }` when the destination it was verifying no longer
 * matches (e.g. staff kept editing the mobile number after verifying an earlier value). */
export interface ContactOtpState {
  otpId: number | null;
  verified: boolean;
}

/**
 * Small presentational OTP-entry block reused up to four times inside the Edit Client
 * "Verify Contact Change" panel (old mobile / new mobile / old email / new email — see
 * `EditClientComponent`), and once each for mobile/email in the Create Client flow (see
 * `ClientGeneralStepComponent`). Renders as 6 individually-bordered digit boxes (one real
 * `<input>` each, auto-advancing focus) rather than the single-input/background-gradient trick
 * used elsewhere in this app — each box needs its own focus/border state, which a shared input
 * can't express.
 */
@Component({
  selector: 'mifosx-client-contact-otp-block',
  templateUrl: './contact-otp-block.component.html',
  styleUrls: ['./contact-otp-block.component.scss'],
  imports: [
    ...STANDALONE_SHARED_IMPORTS,
    FaIconComponent,
    MatProgressSpinner
  ]
})
export class ContactOtpBlockComponent implements OnChanges, OnDestroy {
  private clientsService = inject(ClientsService);

  /** The 6 individual digit-box <input> elements, in order — used to move focus between them. */
  @ViewChildren('digitBox') digitBoxes: QueryList<ElementRef<HTMLInputElement>>;

  /** One independent control per box — NOT a single 6-char string sliced up. Editing box 0
   * can never disturb box 3's value this way. (An earlier version kept one shared string and
   * rebuilt it via `chars.join('')` on every keystroke — `['', '2', '3'].join('') === '23'`
   * silently drops empty slots instead of preserving them as gaps, so deleting an early digit
   * collapsed/shifted every digit after it. Per-box controls sidestep that class of bug
   * entirely — there's no string to rebuild until the moment we actually submit.) */
  readonly digitControls: UntypedFormControl[] = Array.from({ length: 6 }, () => new UntypedFormControl(''));

  /** Fixed-length array so the template can `*ngFor` over exactly 6 boxes. */
  readonly digitIndexes = [
    0,
    1,
    2,
    3,
    4,
    5
  ];

  /** Client whose mobileNo/emailAddress is being changed. Omit this input entirely for the
   * CLIENT CREATION flow — there is no client id yet, so the block falls back to the
   * clientId-less creation-time OTP endpoints (`ClientsService.sendClientCreationContactOtp()` /
   * `verifyClientCreationContactOtp()`) instead of the edit-flow `/clients/{clientId}/...` ones. */
  @Input() clientId?: string;
  /** Which LincPay OTP channel to use. */
  @Input() channel: 'MOBILE' | 'EMAIL';
  /** Raw destination (old or new mobile number / email address) this block verifies. */
  @Input() destination = '';
  /** Display label, e.g. "Old Mobile Number" / "New Email Address". */
  @Input() label = '';

  /** Fires whenever `{ otpId, verified }` changes — including resets. */
  @Output() stateChange = new EventEmitter<ContactOtpState>();

  otpId: number | null = null;
  otpSent = false;
  verified = false;
  sending = false;
  verifying = false;
  errorMessage = '';
  resendCountdown = 0;
  private resendTimer: ReturnType<typeof setInterval> | null = null;

  /** The full 6-digit code, assembled fresh from the 6 independent box controls only when
   * actually needed (display never needs this — each box renders its own control's value). */
  get code(): string {
    return this.digitControls.map((c) => c.value || '').join('');
  }

  get codeValid(): boolean {
    return /^\d{6}$/.test(this.code);
  }

  ngOnChanges(changes: SimpleChanges): void {
    // If the value being verified changes after the fact (staff kept typing), any
    // previously-sent/verified OTP no longer applies to the current destination.
    if (changes['destination'] && !changes['destination'].firstChange && this.otpSent) {
      this.resetState();
    }
  }

  ngOnDestroy(): void {
    if (this.resendTimer) {
      clearInterval(this.resendTimer);
    }
  }

  /** Masks the destination so only a few characters are visible, mirroring the masking
   * convention already used on the login 2FA screen (`maskTarget()`). */
  get maskedDestination(): string {
    const value = this.destination || '';
    if (!value) {
      return '';
    }
    if (this.channel === 'MOBILE') {
      const digits = value.replace(/\D/g, '');
      if (digits.length <= 4) {
        return value;
      }
      return 'X'.repeat(digits.length - 4) + digits.slice(-4);
    }
    const at = value.indexOf('@');
    if (at <= 0) {
      return value;
    }
    const local = value.substring(0, at);
    const domain = value.substring(at);
    const visible = local.substring(0, Math.min(2, local.length));
    const hidden = 'X'.repeat(Math.max(0, local.length - visible.length));
    return visible + hidden + domain;
  }

  sendOtp(): void {
    if (!this.destination || this.sending) {
      return;
    }
    this.sending = true;
    this.errorMessage = '';
    const request$ = this.clientId
      ? this.clientsService.sendClientContactOtp(this.clientId, this.channel, this.destination)
      : this.clientsService.sendClientCreationContactOtp(this.channel, this.destination);
    request$.subscribe({
      next: (res: any) => {
        this.sending = false;
        // The backend reports failure to actually dispatch the OTP (gateway error, flagged
        // number, SMTP failure...) as a 200 response with success:false and a real reason in
        // `message` — never a thrown error. Surface that reason instead of treating it as sent.
        if (res?.success === false) {
          this.errorMessage = res?.message || 'Could not send OTP.';
          return;
        }
        this.otpId = res?.otpId ?? res?.resourceId ?? null;
        this.otpSent = true;
        this.clearAllDigits();
        this.startResendCountdown();
        // The 6 digit boxes only render once otpSent flips true — defer the focus call to the
        // next tick so they exist in the DOM (and in `digitBoxes`) by the time it runs.
        setTimeout(() => this.focusBox(0));
        if (this.otpId == null) {
          this.errorMessage = 'OTP sent, but no reference id was returned. Please contact support.';
        }
      },
      error: (err: any) => {
        this.sending = false;
        this.errorMessage = err?.error?.defaultUserMessage || err?.error?.message || 'Could not send OTP.';
      }
    });
  }

  /** Typing a digit in box `index`: this box's own control gets exactly that digit — every
   * other box's control is untouched, so there's nothing to shift or collapse. Moves focus to
   * the next box unless this was the last one. */
  onDigitInput(index: number, rawValue: string): void {
    const digit = (rawValue || '').replace(/\D/g, '').slice(-1);
    this.digitControls[index].setValue(digit);

    if (digit && index < 5) {
      this.focusBox(index + 1);
    }
  }

  /** Backspace in an empty box clears the PREVIOUS box and moves focus there, matching the
   * usual "segmented OTP input" keyboard feel — again, only ever touching one control at a
   * time. Arrow keys move focus without altering any box's value. */
  onDigitKeydown(index: number, event: KeyboardEvent): void {
    if (event.key === 'Backspace') {
      if (!this.digitControls[index].value && index > 0) {
        this.digitControls[index - 1].setValue('');
        this.focusBox(index - 1);
        event.preventDefault();
      }
      return;
    }
    if (event.key === 'ArrowLeft' && index > 0) {
      this.focusBox(index - 1);
      event.preventDefault();
    } else if (event.key === 'ArrowRight' && index < 5) {
      this.focusBox(index + 1);
      event.preventDefault();
    }
  }

  /** Pasting a full code into any box fills all 6 boxes at once (one control per digit) and
   * focuses the last filled one. */
  onDigitPaste(event: ClipboardEvent): void {
    const pasted = event.clipboardData?.getData('text') || '';
    const digits = pasted.replace(/\D/g, '').slice(0, 6);
    if (!digits) {
      return;
    }
    event.preventDefault();
    digits.split('').forEach((d, i) => this.digitControls[i].setValue(d));
    for (let i = digits.length; i < 6; i++) {
      this.digitControls[i].setValue('');
    }
    this.focusBox(Math.min(digits.length, 6) - 1);
  }

  private clearAllDigits(): void {
    this.digitControls.forEach((c) => c.setValue(''));
  }

  private focusBox(index: number): void {
    const box = this.digitBoxes?.toArray()[index];
    box?.nativeElement.focus();
  }

  resendOtp(): void {
    if (this.resendCountdown > 0 || this.sending) {
      return;
    }
    this.sendOtp();
  }

  verifyOtp(): void {
    if (this.otpId == null || !this.codeValid || this.verifying) {
      this.digitControls.forEach((c) => c.markAsTouched());
      return;
    }
    this.verifying = true;
    this.errorMessage = '';
    const request$ = this.clientId
      ? this.clientsService.verifyClientContactOtp(this.clientId, this.otpId, this.code)
      : this.clientsService.verifyClientCreationContactOtp(this.otpId, this.code);
    request$.subscribe({
      next: (res: any) => {
        this.verifying = false;
        // Defensive shape-tolerance: treat an explicit `verified: false` as failure,
        // anything else (2xx with `verified: true`, or no `verified` field at all) as success.
        const ok = res?.verified !== false;
        if (ok) {
          this.verified = true;
          this.stateChange.emit({ otpId: this.otpId, verified: true });
        } else {
          this.errorMessage = res?.message || 'Incorrect OTP — please try again.';
        }
      },
      error: (err: any) => {
        this.verifying = false;
        this.errorMessage = err?.error?.defaultUserMessage || err?.error?.message || 'OTP verification failed.';
      }
    });
  }

  private resetState(): void {
    this.otpId = null;
    this.otpSent = false;
    this.verified = false;
    this.errorMessage = '';
    this.clearAllDigits();
    if (this.resendTimer) {
      clearInterval(this.resendTimer);
      this.resendTimer = null;
    }
    this.resendCountdown = 0;
    this.stateChange.emit({ otpId: null, verified: false });
  }

  private startResendCountdown(): void {
    this.resendCountdown = 30;
    if (this.resendTimer) {
      clearInterval(this.resendTimer);
    }
    this.resendTimer = setInterval(() => {
      this.resendCountdown--;
      if (this.resendCountdown <= 0 && this.resendTimer) {
        clearInterval(this.resendTimer);
        this.resendTimer = null;
      }
    }, 1000);
  }
}