/**
 * 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 { GL_PERIOD } from '../gl-reports/gl-reports-data';
import {
  FORM_THRESHOLD,
  FormDeclarant,
  FormDeclarantTxn,
  FormType,
  formDeclarants,
  formDeclarantTxns
} from './form-declaration-data';

export interface DateRange {
  from: string;
  to: string;
}

export interface FormReportFilter {
  range: DateRange;
  /** '' means every branch. */
  branchCode: string;
  /** '' means both declaration types. */
  formType: FormType | '';
  /** '' means every transaction category (Cash, Clearing, Loan, …). */
  group: string;
  /** Free text over name, account number and acknowledgement number. */
  search: string;
  /** Show only rows a compliance officer would need to look at. */
  flaggedOnly: boolean;
}

/** One transaction, joined to the declarant who filed for it. */
export interface FormTxnRow extends FormDeclarantTxn {
  declarantName: string;
  formType: FormType;
  fatherName: string;
  declaredOn: string;
  reasonForNoPan: string;
  estimatedIncome: number;
  /** Counter or ATM cash, as opposed to a book or electronic entry. */
  isCash: boolean;
  /**
   * The transaction is one of the categories in Rule 114B, so PAN — and in its
   * absence the Form 97/98 declaration — was mandatory for it.
   */
  declarationRequired: boolean;
  /** Cash at or above the CTR limit — also lands in the monthly CTR. */
  ctrReportable: boolean;
}

/** A declarant with their totals for the period. */
export interface FormPersonRow {
  declarant: FormDeclarant;
  txns: FormTxnRow[];
  txnCount: number;
  cashCount: number;
  totalCredit: number;
  totalDebit: number;
  cashTotal: number;
  /** Largest single transaction, used to sort the riskiest to the top. */
  maxAmount: number;
  /** How many of the period's transactions needed the declaration. */
  declaredCount: number;
  ctrCount: number;
  /** Distinct categories the customer transacted in during the period. */
  groups: string[];
  /**
   * Aggregate cash for the period against the income the customer declared.
   * A ratio well above 1 is the classic "turnover inconsistent with declared
   * income" flag, which is why the declaration is collected in the first place.
   */
  incomeRatio: number;
}

export interface FormReportSummary {
  persons: number;
  form60Persons: number;
  form61Persons: number;
  txnCount: number;
  cashTotal: number;
  cashCount: number;
  totalCredit: number;
  totalDebit: number;
  /** Transactions falling in a Rule 114B category. */
  declarationRequired: number;
  ctrReportable: number;
  /** Transaction count by category, largest first — drives the mix panel. */
  byGroup: { group: string; count: number; amount: number }[];
}

function clamp(range: DateRange): DateRange {
  const from = range.from < GL_PERIOD.fyStart ? GL_PERIOD.fyStart : range.from;
  const to = range.to > GL_PERIOD.fyEnd ? GL_PERIOD.fyEnd : range.to;
  // A backwards range would silently return nothing; collapse it to a single day.
  return from > to ? { from: to, to: to } : { from, to };
}

/** Monday-to-Saturday banking week containing the given date. */
export function weekRange(anchor: string): DateRange {
  const d = new Date(`${anchor}T00:00:00Z`);
  const dow = d.getUTCDay(); // 0 = Sunday
  const monday = new Date(d.getTime());
  monday.setUTCDate(d.getUTCDate() - (dow === 0 ? 6 : dow - 1));
  const saturday = new Date(monday.getTime());
  saturday.setUTCDate(monday.getUTCDate() + 5);
  const iso = (x: Date) => x.toISOString().slice(0, 10);
  return { from: iso(monday), to: iso(saturday) };
}

export function monthRange(month: string): DateRange {
  const [
    y,
    m
  ] = month.split('-').map(Number);
  const last = new Date(Date.UTC(y, m, 0)).getUTCDate();
  return { from: `${month}-01`, to: `${month}-${`${last}`.padStart(2, '0')}` };
}

/**
 * Transactions matching the filter, each joined to its declarant.
 *
 * Memoised on the filter signature: the getters that feed the template are read
 * many times per change-detection pass, and re-scanning several hundred rows on
 * every read is what made the GL reports stall.
 */
let rowCacheKey = '';
let rowCache: FormTxnRow[] = [];

export function formTxnRows(filter: FormReportFilter): FormTxnRow[] {
  const range = clamp(filter.range);
  const key = [
    range.from,
    range.to,
    filter.branchCode,
    filter.formType,
    filter.group,
    filter.search.trim().toLowerCase(),
    filter.flaggedOnly ? '1' : '0'
  ].join('|');

  if (key === rowCacheKey) {
    return rowCache;
  }

  const byAck = new Map(
    formDeclarants().map((d) => [
      d.ackNo,
      d
    ])
  );
  const needle = filter.search.trim().toLowerCase();

  const rows: FormTxnRow[] = [];
  for (const t of formDeclarantTxns()) {
    if (t.date < range.from || t.date > range.to) {
      continue;
    }
    if (filter.branchCode && t.branchCode !== filter.branchCode) {
      continue;
    }
    if (filter.group && t.group !== filter.group) {
      continue;
    }
    const d = byAck.get(t.ackNo);
    if (!d) {
      continue;
    }
    if (filter.formType && d.formType !== filter.formType) {
      continue;
    }
    if (
      needle &&
      !d.name.toLowerCase().includes(needle) &&
      !t.accountNo.toLowerCase().includes(needle) &&
      !d.ackNo.toLowerCase().includes(needle)
    ) {
      continue;
    }

    // ATM dispensing is cash in the customer's hands, so it counts towards the
    // cash view even though it never crossed the counter.
    const isCash = t.mode === 'CASH' || t.mode === 'ATM';
    const ctrReportable = isCash && t.amount >= FORM_THRESHOLD.CTR;

    if (filter.flaggedOnly && !ctrReportable) {
      continue;
    }

    rows.push({
      ...t,
      declarantName: d.name,
      formType: d.formType,
      fatherName: d.fatherName,
      declaredOn: d.declaredOn,
      reasonForNoPan: d.reasonForNoPan,
      estimatedIncome: d.estimatedIncome,
      isCash,
      declarationRequired: t.rule114B,
      ctrReportable
    });
  }

  rowCacheKey = key;
  rowCache = rows;
  return rows;
}

/** The same rows grouped by declarant, heaviest customer first. */
export function formPersonRows(filter: FormReportFilter): FormPersonRow[] {
  const byAck = new Map(
    formDeclarants().map((d) => [
      d.ackNo,
      d
    ])
  );
  const grouped = new Map<string, FormTxnRow[]>();

  for (const r of formTxnRows(filter)) {
    const list = grouped.get(r.ackNo);
    if (list) {
      list.push(r);
    } else {
      grouped.set(r.ackNo, [r]);
    }
  }

  const out: FormPersonRow[] = [];
  for (const [
    ackNo,
    txns
  ] of grouped) {
    const declarant = byAck.get(ackNo);
    if (!declarant) {
      continue;
    }
    const cash = txns.filter((t) => t.isCash);
    const cashTotal = cash.reduce((s, t) => s + t.amount, 0);
    out.push({
      declarant,
      txns,
      txnCount: txns.length,
      cashCount: cash.length,
      totalCredit: txns.filter((t) => t.drCr === 'CR').reduce((s, t) => s + t.amount, 0),
      totalDebit: txns.filter((t) => t.drCr === 'DR').reduce((s, t) => s + t.amount, 0),
      cashTotal,
      maxAmount: txns.reduce((m, t) => Math.max(m, t.amount), 0),
      declaredCount: txns.filter((t) => t.declarationRequired).length,
      ctrCount: txns.filter((t) => t.ctrReportable).length,
      groups: [...new Set(txns.map((t) => t.group))].sort(),
      incomeRatio: declarant.estimatedIncome > 0 ? cashTotal / declarant.estimatedIncome : 0
    });
  }

  out.sort((a, b) => b.cashTotal - a.cashTotal);
  return out;
}

export function formReportSummary(filter: FormReportFilter): FormReportSummary {
  const rows = formTxnRows(filter);
  const acks = new Set(rows.map((r) => r.ackNo));
  const form61 = new Set(rows.filter((r) => r.formType === 'FORM_61').map((r) => r.ackNo));
  const form60 = new Set(rows.filter((r) => r.formType === 'FORM_60').map((r) => r.ackNo));

  const groupMap = new Map<string, { group: string; count: number; amount: number }>();
  for (const r of rows) {
    const g = groupMap.get(r.group);
    if (g) {
      g.count++;
      g.amount += r.amount;
    } else {
      groupMap.set(r.group, { group: r.group, count: 1, amount: r.amount });
    }
  }

  const cash = rows.filter((r) => r.isCash);

  return {
    persons: acks.size,
    form60Persons: form60.size,
    form61Persons: form61.size,
    txnCount: rows.length,
    cashTotal: cash.reduce((s, r) => s + r.amount, 0),
    cashCount: cash.length,
    totalCredit: rows.filter((r) => r.drCr === 'CR').reduce((s, r) => s + r.amount, 0),
    totalDebit: rows.filter((r) => r.drCr === 'DR').reduce((s, r) => s + r.amount, 0),
    declarationRequired: rows.filter((r) => r.declarationRequired).length,
    ctrReportable: rows.filter((r) => r.ctrReportable).length,
    byGroup: [...groupMap.values()].sort((a, b) => b.count - a.count)
  };
}