import { BadRequestException } from "@nestjs/common";
import { jalaliToGregorianDate } from "src/helpers/date-jalali";
import { gregorianDateInIran } from "src/helpers/iran-datetime";

export type FanavaranPolicyInquiryRow = {
  PolicyId?: unknown;
  EndDate?: unknown;
};

export type SelectedFanavaranPolicy = {
  policy: FanavaranPolicyInquiryRow;
  policyId: number;
  endDate: string;
  endDateGregorian: string;
};

type DatedFanavaranPolicy = {
  policy: FanavaranPolicyInquiryRow;
  endDate: string;
  endDateGregorian: string;
};

const NO_POLICY_MESSAGE =
  "No Fanavaran policies were found for the insurer national code. PolicyId is required; contact the administrator.";

const EXPIRED_POLICY_MESSAGE =
  "The latest insurance policy is expired and cannot be sent to Fanavaran. Contact the administrator.";

const INVALID_POLICY_MESSAGE =
  "Fanavaran policy inquiry returned policies without a valid PolicyId or EndDate. PolicyId is required; contact the administrator.";

function parsePolicyId(value: unknown): number | null {
  if (value === null || value === undefined) return null;
  if (typeof value === "string" && value.trim() === "") return null;
  const id = Number(value);
  return Number.isFinite(id) && id > 0 ? id : null;
}

function normalizeEndDate(value: unknown): {
  endDate: string;
  endDateGregorian: string;
} | null {
  if (value === null || value === undefined) return null;
  const endDate = String(value).trim();
  if (!endDate) return null;

  const endDateGregorian = jalaliToGregorianDate(endDate);
  if (!endDateGregorian) return null;

  return { endDate, endDateGregorian };
}

export function selectLatestActiveFanavaranPolicy(
  policies: unknown,
  todayGregorian: string = gregorianDateInIran(new Date()),
): SelectedFanavaranPolicy {
  if (!Array.isArray(policies) || policies.length === 0) {
    throw new BadRequestException(NO_POLICY_MESSAGE);
  }

  const candidates = policies
    .map((policy) => {
      if (!policy || typeof policy !== "object") return null;
      const row = policy as FanavaranPolicyInquiryRow;
      const endDate = normalizeEndDate(row.EndDate);
      if (!endDate) return null;
      return {
        policy: row,
        endDate: endDate.endDate,
        endDateGregorian: endDate.endDateGregorian,
      };
    })
    .filter((policy): policy is DatedFanavaranPolicy => policy !== null);

  if (candidates.length === 0) {
    throw new BadRequestException(INVALID_POLICY_MESSAGE);
  }

  const latest = candidates.reduce((currentLatest, candidate) =>
    candidate.endDateGregorian > currentLatest.endDateGregorian
      ? candidate
      : currentLatest,
  );

  if (latest.endDateGregorian < todayGregorian) {
    throw new BadRequestException(EXPIRED_POLICY_MESSAGE);
  }

  const policyId = parsePolicyId(latest.policy.PolicyId);
  if (policyId === null) {
    throw new BadRequestException(INVALID_POLICY_MESSAGE);
  }

  return { ...latest, policyId };
}