/**
 * 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 * as ExcelJS from 'exceljs';

import { TdsAccountLine, TdsInterestRow, TdsInterestSummary } from './tds-reports.compute';

/** What the workbook needs from the screen, so it prints exactly what the user is looking at. */
export interface TdsExportInput {
  fy: string;
  scopeLabel: string;
  /** The financial-year rules, from Organization › TDS Configuration. */
  rules: { general: number; senior: number; rate: number; rateNoPan: number } | null;
  /** The quarterly return the declarants' gross-paid interest is reported in. */
  statement: string;
  rows: TdsInterestRow[];
  declaredRows: TdsInterestRow[];
  summary: TdsInterestSummary;
  statusOf: (row: TdsInterestRow) => { label: string };
}

const MONEY = '"₹"#,##0.00';
const DATE = 'dd-mmm-yyyy';
const NAVY = 'FF1F4E79';
const STRIPE = 'FFF3F6FA';
const LINE = 'FFD0D7E2';
const GREEN = 'FF15803D';
const AMBER = 'FFB45309';

const ACCOUNT_TYPE: Record<TdsAccountLine['type'], string> = {
  FD: 'Fixed deposit',
  RD: 'Recurring deposit',
  SB: 'Savings',
  OTHER: 'Other'
};

/** A column: its heading, width and, for figures, the cell format. */
interface Col {
  header: string;
  width: number;
  fmt?: string;
  /** Totalled in the closing row. */
  sum?: boolean;
}

/**
 * The Deposit Interest & TDS register as a workbook a branch can read without the screen beside it:
 * a one-page summary, one row per customer, one row per account, and the declarants on their own.
 */
export function buildTdsInterestWorkbook(input: TdsExportInput): ExcelJS.Workbook {
  const wb = new ExcelJS.Workbook();
  wb.creator = 'CBS Nexora';
  wb.created = new Date();

  summarySheet(wb, input);
  customersSheet(wb, input);
  accountsSheet(wb, input);
  declarationsSheet(wb, input);
  return wb;
}

// ─────────────────────────────── Sheets ───────────────────────────────

function summarySheet(wb: ExcelJS.Workbook, input: TdsExportInput): void {
  const ws = wb.addWorksheet('Summary', { views: [{ showGridLines: false }] });
  ws.columns = [
    { width: 46 },
    { width: 22 }
  ];
  title(ws, `Deposit Interest & TDS — FY ${input.fy}`, 2);
  ws.addRow([`Branch: ${input.scopeLabel}`]);
  ws.addRow([`Prepared on: ${new Date().toLocaleDateString('en-IN', { day: '2-digit', month: 'short', year: 'numeric' })}`]);
  ws.getRow(2).font = { color: { argb: 'FF555555' } };
  ws.getRow(3).font = { color: { argb: 'FF555555' } };
  ws.addRow([]);

  const s = input.summary;
  section(ws, 'Key figures');
  const figures: [string, number, string?][] = [
    ['Customers in this report', s.deductees],
    ['  of whom have an FD / RD being tracked', s.trackedCustomers],
    ['FD / RD interest received this year', s.applicableInterest, MONEY],
    ['Savings interest (shown only — no TDS)', s.exemptInterest, MONEY],
    ['Customers over the TDS limit', s.crossed],
    ['TDS due by the rules', s.totalTds, MONEY],
    ['TDS actually deducted from accounts', s.actualTds, MONEY],
    ['Difference (due − deducted) — should be 0', s.totalTds - s.actualTds, MONEY],
    ['Customers with Form 121 / 15G / 15H', s.declarations],
    ['TDS not deducted because of those forms', s.tdsSaved, MONEY],
    ['Interest paid without TDS (report in the return)', s.paidWithoutDeduction, MONEY]
  ];
  for (const [label, value, fmt] of figures) {
    const r = ws.addRow([label, value]);
    r.getCell(2).numFmt = fmt ?? '#,##0';
    r.getCell(2).alignment = { horizontal: 'right' };
    boxRow(r, 2);
  }
  // The control figure stands out when it is not zero.
  const diffRow = ws.getRow(ws.rowCount - 3);
  if (Math.round(s.totalTds - s.actualTds) !== 0) {
    diffRow.font = { bold: true, color: { argb: AMBER } };
  }
  ws.addRow([]);

  if (input.rules) {
    section(ws, 'Rules for this year');
    const rules: [string, string][] = [
      ['TDS limit — below 60', rupees(input.rules.general)],
      ['TDS limit — senior citizen (60+)', rupees(input.rules.senior)],
      ['Rate with PAN', `${input.rules.rate}%`],
      ['Rate without PAN', `${input.rules.rateNoPan}%`]
    ];
    for (const [label, value] of rules) {
      const r = ws.addRow([label, value]);
      r.getCell(2).alignment = { horizontal: 'right' };
      boxRow(r, 2);
    }
    ws.addRow([]);
  }

  section(ws, 'How to read this workbook');
  const notes = [
    'Only interest from fixed and recurring deposits counts toward the limit — on the day it reaches savings, or when paid out at closure.',
    "A savings account's own interest is shown for information and never attracts TDS.",
    "Once a customer's interest for the year crosses the limit, TDS is due on the whole year's interest, not only the excess.",
    'A Form 121 / 15G / 15H stops TDS on interest received after the form was accepted.',
    'Sheet "Customers": one row per customer. Sheet "Accounts": every account behind those figures.',
    'Sheet "Form 121 given": customers with a declaration, and the TDS the form saved them.'
  ];
  for (const n of notes) {
    const r = ws.addRow([`•  ${n}`]);
    ws.mergeCells(r.number, 1, r.number, 2);
    r.alignment = { wrapText: true, vertical: 'top' };
    r.height = 30;
  }
}

function customersSheet(wb: ExcelJS.Workbook, input: TdsExportInput): void {
  const cols: Col[] = [
    { header: 'S.No', width: 6 },
    { header: 'Customer name', width: 26 },
    { header: 'Customer ID', width: 13 },
    { header: 'PAN', width: 13 },
    { header: 'Branch', width: 14 },
    { header: 'Age group', width: 12 },
    { header: 'FD/RD interest received (₹)', width: 16, fmt: MONEY, sum: true },
    { header: 'TDS limit (₹)', width: 13, fmt: MONEY },
    { header: 'Over the limit?', width: 10 },
    { header: 'Rate', width: 7 },
    { header: 'TDS due (₹)', width: 13, fmt: MONEY, sum: true },
    { header: 'TDS deducted (₹)', width: 13, fmt: MONEY, sum: true },
    { header: 'Difference (₹)', width: 13, fmt: MONEY, sum: true },
    { header: 'Form 121 given?', width: 10 },
    { header: 'Status', width: 42 }
  ];
  const ws = table(wb, 'Customers', `Customers — FY ${input.fy} · ${input.scopeLabel}`, cols);

  input.rows.forEach((r, i) => {
    const line = ws.addRow([
      i + 1,
      r.deductee.name,
      r.deductee.customerId,
      r.deductee.pan || 'Not on record',
      r.branchCode,
      r.band === 'SENIOR' ? 'Senior (60+)' : 'Below 60',
      r.tdsApplicableInterest,
      r.threshold,
      r.crossed ? 'Yes' : 'No',
      `${Math.round(r.rateApplied * 100)}%`,
      r.schedule.totalTds,
      r.actualTds,
      null,
      r.hasDeclaration ? 'Yes' : 'No',
      input.statusOf(r).label
    ]);
    // Due − deducted as a formula, so an edited figure keeps the check honest.
    line.getCell(13).value = { formula: `K${line.number}-L${line.number}` };
    styleDataRow(line, cols, i);
    if (!r.deductee.pan) {
      line.getCell(4).font = { color: { argb: AMBER } };
    }
    if (r.crossed) {
      line.getCell(9).font = { bold: true, color: { argb: AMBER } };
    }
    if (Math.round(r.schedule.totalTds - r.actualTds) !== 0) {
      line.getCell(13).font = { bold: true, color: { argb: AMBER } };
    }
  });
  totals(ws, cols, input.rows.length);
}

function accountsSheet(wb: ExcelJS.Workbook, input: TdsExportInput): void {
  const cols: Col[] = [
    { header: 'S.No', width: 6 },
    { header: 'Customer name', width: 26 },
    { header: 'Customer ID', width: 13 },
    { header: 'Account no.', width: 19 },
    { header: 'Account type', width: 17 },
    { header: 'Counted for TDS?', width: 10 },
    { header: 'Why', width: 46 },
    { header: 'Interest this year (₹)', width: 15, fmt: MONEY, sum: true },
    { header: 'Credits', width: 8 },
    { header: 'Last credited', width: 13, fmt: DATE },
    { header: 'TDS deducted (₹)', width: 13, fmt: MONEY, sum: true },
    { header: 'Account held by', width: 22 }
  ];
  const ws = table(wb, 'Accounts', `Accounts — FY ${input.fy} · ${input.scopeLabel}`, cols);

  let n = 0;
  for (const r of input.rows) {
    for (const a of r.accounts) {
      const line = ws.addRow([
        n + 1,
        r.deductee.name,
        r.deductee.customerId,
        a.accountNo,
        ACCOUNT_TYPE[a.type],
        a.tracked ? 'Yes' : 'No',
        a.reason,
        a.interest,
        a.postings,
        a.lastPostedOn ? isoToDate(a.lastPostedOn) : '—',
        a.tdsDeducted,
        a.holderName ?? 'Same customer'
      ]);
      styleDataRow(line, cols, n);
      if (a.tracked) {
        line.getCell(6).font = { bold: true, color: { argb: GREEN } };
      }
      n++;
    }
  }
  totals(ws, cols, n);
}

function declarationsSheet(wb: ExcelJS.Workbook, input: TdsExportInput): void {
  const cols: Col[] = [
    { header: 'S.No', width: 6 },
    { header: 'Customer name', width: 26 },
    { header: 'Customer ID', width: 13 },
    { header: 'PAN', width: 13 },
    { header: 'Branch', width: 14 },
    { header: 'Form', width: 10 },
    { header: 'UIN', width: 18 },
    { header: 'Accepted on', width: 13, fmt: DATE },
    { header: 'FD/RD interest received (₹)', width: 16, fmt: MONEY, sum: true },
    { header: `Paid without TDS — report in ${input.statement} (₹)`, width: 20, fmt: MONEY, sum: true },
    { header: 'TDS not deducted because of the form (₹)', width: 18, fmt: MONEY, sum: true },
    { header: 'TDS deducted before the form (₹)', width: 16, fmt: MONEY, sum: true }
  ];
  const ws = table(wb, 'Form 121 given', `Customers with Form 121 / 15G / 15H — FY ${input.fy} · ${input.scopeLabel}`, cols);

  input.declaredRows.forEach((r, i) => {
    const line = ws.addRow([
      i + 1,
      r.deductee.name,
      r.deductee.customerId,
      r.deductee.pan || 'Not on record',
      r.branchCode,
      `Form ${r.form}`,
      r.declarationUin ?? 'Not allotted',
      r.declarationAcceptedOn ? isoToDate(r.declarationAcceptedOn) : '—',
      r.tdsApplicableInterest,
      r.paidWithoutDeduction,
      r.tdsSaved,
      r.actualTds
    ]);
    styleDataRow(line, cols, i);
    if (!r.declarationUin) {
      line.getCell(7).font = { color: { argb: AMBER } };
    }
  });
  if (input.declaredRows.length === 0) {
    const r = ws.addRow(['', 'No customer has a declaration on record for this year.']);
    r.font = { italic: true, color: { argb: 'FF777777' } };
  } else {
    totals(ws, cols, input.declaredRows.length);
  }
}

// ─────────────────────────────── Styling ───────────────────────────────

/** A sheet with a title, a styled header row, frozen headings and a filter. */
function table(wb: ExcelJS.Workbook, name: string, heading: string, cols: Col[]): ExcelJS.Worksheet {
  const ws = wb.addWorksheet(name, { views: [{ state: 'frozen', ySplit: 3, showGridLines: false }] });
  ws.columns = cols.map((c) => ({ width: c.width }));
  title(ws, heading, cols.length);
  ws.addRow([]);
  const head = ws.addRow(cols.map((c) => c.header));
  head.height = 34;
  head.eachCell((cell) => {
    cell.font = { bold: true, color: { argb: 'FFFFFFFF' } };
    cell.fill = { type: 'pattern', pattern: 'solid', fgColor: { argb: NAVY } };
    cell.alignment = { vertical: 'middle', horizontal: 'center', wrapText: true };
    cell.border = border();
  });
  ws.autoFilter = { from: { row: 3, column: 1 }, to: { row: 3, column: cols.length } };
  return ws;
}

function title(ws: ExcelJS.Worksheet, text: string, span: number): void {
  const r = ws.addRow([text]);
  ws.mergeCells(r.number, 1, r.number, span);
  r.font = { bold: true, size: 14, color: { argb: NAVY } };
  r.height = 24;
}

function section(ws: ExcelJS.Worksheet, text: string): void {
  const r = ws.addRow([text]);
  r.font = { bold: true, color: { argb: 'FFFFFFFF' } };
  r.getCell(1).fill = { type: 'pattern', pattern: 'solid', fgColor: { argb: NAVY } };
  r.getCell(2).fill = { type: 'pattern', pattern: 'solid', fgColor: { argb: NAVY } };
}

function styleDataRow(row: ExcelJS.Row, cols: Col[], index: number): void {
  cols.forEach((c, i) => {
    const cell = row.getCell(i + 1);
    cell.border = border();
    cell.alignment = { vertical: 'middle', wrapText: i === cols.length - 1 || c.width > 30 };
    if (c.fmt) {
      cell.numFmt = c.fmt;
      cell.alignment = { ...cell.alignment, horizontal: 'right' };
    }
    if (index % 2 === 1) {
      cell.fill = { type: 'pattern', pattern: 'solid', fgColor: { argb: STRIPE } };
    }
  });
}

/** A closing row that totals the money columns with live SUM formulas. */
function totals(ws: ExcelJS.Worksheet, cols: Col[], count: number): void {
  if (count === 0) {
    return;
  }
  const first = 4;
  const last = first + count - 1;
  const r = ws.addRow(cols.map((c, i) => (i === 1 ? 'Total' : null)));
  cols.forEach((c, i) => {
    const cell = r.getCell(i + 1);
    if (c.sum) {
      const letter = ws.getColumn(i + 1).letter;
      cell.value = { formula: `SUM(${letter}${first}:${letter}${last})` };
      cell.numFmt = c.fmt ?? '#,##0';
      cell.alignment = { horizontal: 'right' };
    }
    cell.font = { bold: true };
    cell.border = { top: { style: 'medium', color: { argb: NAVY } }, bottom: { style: 'thin', color: { argb: LINE } } };
  });
}

function boxRow(row: ExcelJS.Row, span: number): void {
  for (let i = 1; i <= span; i++) {
    row.getCell(i).border = border();
  }
}

function border(): Partial<ExcelJS.Borders> {
  const side = { style: 'thin' as const, color: { argb: LINE } };
  return { top: side, left: side, bottom: side, right: side };
}

function rupees(n: number): string {
  return `₹${Math.round(n).toLocaleString('en-IN')}`;
}

/** '2026-10-05' as a real date, so Excel sorts and filters it as one. */
function isoToDate(iso: string): Date {
  const [
    y,
    m,
    d
  ] = iso.slice(0, 10).split('-').map(Number);
  return new Date(Date.UTC(y, m - 1, d));
}