/**
 * 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/.
 */

/**
 * Derives a client's KYC exception state from their verification status.
 *
 * A KYC exception is not something an officer should have to remember to tick — it is simply the
 * fact that a mandatory identity check has not passed. Deriving it means the exception list can
 * never drift out of step with reality: raising, narrowing and closing all fall out of whether PAN
 * and Aadhaar are verified at the moment of the save.
 *
 * Shared by the client-creation stepper and the client-view KYC tab so both write identical state.
 */

export const KYC_EXCEPTION_PAN = 'PAN Card Verification Failed';
export const KYC_EXCEPTION_AADHAAR = 'Aadhaar Verification Failed';

/** The two reasons this module owns. Anything else on a record was added by an officer by hand. */
export const AUTO_MANAGED_KYC_EXCEPTION_REASONS: string[] = [
  KYC_EXCEPTION_PAN,
  KYC_EXCEPTION_AADHAAR
];

export interface KycExceptionInput {
  /** PAN verified against the Income Tax database. Unverified OR simply not entered → exception. */
  panVerified: boolean;
  /** Aadhaar verified against UIDAI. Unverified OR simply not entered → exception. */
  aadhaarVerified: boolean;
  /**
   * False for non-individual clients, where no Aadhaar is collected (the payload sends a dummy
   * masked value). Without this guard every company would carry a permanent Aadhaar exception.
   */
  aadhaarApplicable: boolean;
  /** Whether an exception is already recorded — decides raise vs. resolve on a clean save. */
  hadException: boolean;
  /** Reason currently persisted, kept verbatim when closing so the audit trail survives. */
  previousReason: string | null;
  /** Officer-entered reasons beyond the two automatic ones; carried through untouched. */
  manualReasons?: string[];
  /** Today in the tenant's date format — stamped as exceptionResolvedOn when closing. */
  todayFormatted: string;
}

export interface KycExceptionFields {
  isException: boolean;
  exceptionReason: string | null;
  exceptionResolved: boolean;
  exceptionResolvedOn: string | null;
}

/**
 * Maps verification status to the four exception columns the API expects.
 *
 * Three outcomes:
 * - **Something outstanding** → raise/keep the exception, listing only what is still failing. A
 *   record that had both PAN and Aadhaar outstanding and has since verified PAN comes back with
 *   Aadhaar alone, which is what narrows the entry rather than closing it.
 * - **Nothing outstanding, exception existed** → close it. `exceptionReason` is retained on
 *   purpose: the Resolved tab shows what was resolved, and clearing it would erase the record of
 *   why the exception was ever raised.
 * - **Nothing outstanding, no exception** → leave every flag off, so a clean client never appears
 *   in either tab.
 */
export function deriveKycExceptionFields(input: KycExceptionInput): KycExceptionFields {
  const outstanding: string[] = [];

  if (!input.panVerified) {
    outstanding.push(KYC_EXCEPTION_PAN);
  }
  if (input.aadhaarApplicable && !input.aadhaarVerified) {
    outstanding.push(KYC_EXCEPTION_AADHAAR);
  }

  // Officer-added reasons ride along, but the two automatic ones are filtered out first — a stale
  // 'PAN Card Verification Failed' left in the form must not survive PAN actually being verified.
  for (const reason of input.manualReasons || []) {
    const trimmed = (reason || '').trim();
    if (trimmed && !AUTO_MANAGED_KYC_EXCEPTION_REASONS.includes(trimmed) && !outstanding.includes(trimmed)) {
      outstanding.push(trimmed);
    }
  }

  if (outstanding.length > 0) {
    return {
      isException: true,
      exceptionReason: outstanding.join(', '),
      exceptionResolved: false,
      exceptionResolvedOn: null
    };
  }

  if (input.hadException) {
    return {
      isException: false,
      exceptionReason: input.previousReason || null,
      exceptionResolved: true,
      exceptionResolvedOn: input.todayFormatted
    };
  }

  return {
    isException: false,
    exceptionReason: null,
    exceptionResolved: false,
    exceptionResolvedOn: null
  };
}