/**
 * 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 { MatrixTable, ReturnGeneralInfoRow, ReturnLine, ReturnSignatory, SIGNATORY_FIELDS } from './oss-return.model';

/** Palette lifted from the RBI CIMS workbooks so exports look like the originals. */
export const XL = {
  banner: 'FF002F5F',
  bannerText: 'FFFFFFFF',
  headerGrey: 'FFC0C0C0',
  derivedBlue: 'FF9CC3F5',
  auditYellow: 'FFFFFFCC',
  keyCell: 'FFD9D9D9',
  border: 'FF000000'
};

const AMOUNT_FMT = '#,##0.00';
const COUNT_FMT = '#,##0';

export function solidFill(argb: string): ExcelJS.Fill {
  return { type: 'pattern', pattern: 'solid', fgColor: { argb } };
}

/**
 * The diagonal hatching RBI's templates put on a cell that is waiting to be filled in by hand.
 *
 * It reads differently from an empty cell, and the difference matters on a statutory form: an empty
 * cell says nothing was reported, hatching says someone still has to report it. The templates use
 * it on the signatory block and on the particulars a bank writes in itself.
 */
export function hatchFill(): ExcelJS.Fill {
  return { type: 'pattern', pattern: 'lightUp', fgColor: { argb: 'FF808080' }, bgColor: { argb: 'FFFFFFFF' } };
}

/** Dark-blue full-width banner that heads every sheet in the RBI templates. */
export function addBanner(sheet: ExcelJS.Worksheet, title: string, lastCol: string): void {
  const row = sheet.addRow([title]);
  sheet.mergeCells(`A${row.number}:${lastCol}${row.number}`);
  row.height = 26;
  const cell = row.getCell(1);
  cell.fill = solidFill(XL.banner);
  cell.font = { bold: true, size: 13, color: { argb: XL.bannerText } };
  cell.alignment = { vertical: 'middle', horizontal: 'center' };
  sheet.addRow([]);
}

export function boxAllCells(sheet: ExcelJS.Worksheet, from: number, to: number, lastColIndex: number): void {
  for (let r = from; r <= to; r++) {
    for (let c = 1; c <= lastColIndex; c++) {
      sheet.getRow(r).getCell(c).border = {
        top: { style: 'thin', color: { argb: XL.border } },
        left: { style: 'thin', color: { argb: XL.border } },
        bottom: { style: 'thin', color: { argb: XL.border } },
        right: { style: 'thin', color: { argb: XL.border } }
      };
    }
  }
}

export function addSectionHeader(sheet: ExcelJS.Worksheet, label: string, unitLabel?: string): void {
  const row = sheet.addRow([
    label,
    unitLabel ?? ''
  ]);
  row.font = { bold: true };
  row.eachCell((cell) => (cell.fill = solidFill(XL.headerGrey)));
  row.getCell(2).alignment = { horizontal: 'right' };
}

/** Renders a labelled block; indents by level and shades derived totals. */
export function addLineRows(sheet: ExcelJS.Worksheet, lines: ReturnLine[]): void {
  for (const line of lines) {
    const row = sheet.addRow([
      line.label,
      line.value
    ]);
    const labelCell = row.getCell(1);
    const valueCell = row.getCell(2);

    labelCell.alignment = { wrapText: true, vertical: 'middle', indent: line.level };
    if (line.level === 0) {
      labelCell.font = { bold: true };
    }
    valueCell.numFmt = line.count ? COUNT_FMT : AMOUNT_FMT;
    valueCell.alignment = { horizontal: 'right' };
    if (line.total) {
      valueCell.fill = solidFill(XL.derivedBlue);
      valueCell.font = { bold: true };
    }
  }
}

/**
 * Writes a multi-column statement: title band, column header row, then the matrix
 * rows. Returns the row number after the block so callers can keep stacking.
 */
export function addMatrixTable(sheet: ExcelJS.Worksheet, table: MatrixTable): void {
  const colCount = table.columns.length + 1;
  const start = sheet.rowCount + 1;

  const titleRow = sheet.addRow([
    table.title,
    ...(table.unit ? [table.unit] : [])
  ]);
  if (!table.unit) {
    sheet.mergeCells(titleRow.number, 1, titleRow.number, colCount);
  }
  titleRow.font = { bold: true };
  for (let c = 1; c <= colCount; c++) {
    titleRow.getCell(c).fill = solidFill(XL.headerGrey);
  }

  if (table.subtitle) {
    const sub = sheet.addRow([table.subtitle]);
    sheet.mergeCells(sub.number, 1, sub.number, colCount);
    sub.font = { bold: true, size: 10 };
    sub.alignment = { wrapText: true };
    sub.getCell(1).fill = solidFill(XL.headerGrey);
  }

  const head = sheet.addRow([
    'Particulars',
    ...table.columns
  ]);
  head.font = { bold: true };
  head.alignment = { wrapText: true, horizontal: 'center', vertical: 'middle' };
  head.eachCell((c) => (c.fill = solidFill(XL.headerGrey)));

  for (const row of table.rows) {
    const excelRow = sheet.addRow([
      row.label,
      ...row.values
    ]);
    const labelCell = excelRow.getCell(1);
    labelCell.alignment = { wrapText: true, vertical: 'middle', indent: row.level };
    if (row.level === 0 || row.header) {
      labelCell.font = { bold: true };
    }
    if (row.header) {
      labelCell.fill = solidFill(XL.headerGrey);
      continue;
    }
    for (let c = 2; c <= colCount; c++) {
      const cell = excelRow.getCell(c);
      cell.numFmt = row.percent ? '0.00"%"' : AMOUNT_FMT;
      cell.alignment = { horizontal: 'right' };
      if (row.total) {
        cell.fill = solidFill(XL.derivedBlue);
        cell.font = { bold: true };
      }
    }
  }
  boxAllCells(sheet, start, sheet.rowCount, colCount);

  for (const note of table.notes ?? []) {
    const noteRow = sheet.addRow([note]);
    sheet.mergeCells(noteRow.number, 1, noteRow.number, colCount);
    noteRow.font = { bold: true, size: 9 };
    noteRow.alignment = { wrapText: true };
    noteRow.getCell(1).fill = solidFill(XL.headerGrey);
  }
  sheet.addRow([]);
}

/** The General Information sheet is identical in shape across every OSS return. */
export function buildGeneralInfoSheet(wb: ExcelJS.Workbook, rows: ReturnGeneralInfoRow[]): void {
  const sheet = wb.addWorksheet('General Information');
  sheet.columns = [
    { width: 26 },
    { width: 58 }];
  addBanner(sheet, 'General Information', 'B');

  const first = sheet.rowCount + 1;
  for (const item of rows) {
    const row = sheet.addRow([
      item.label,
      item.value
    ]);
    row.getCell(1).fill = solidFill(XL.keyCell);
    // The workbook tints the audit flag yellow and leaves unfilled cells grey.
    const fill = item.label === 'Audit Flag' ? XL.auditYellow : item.value ? XL.derivedBlue : XL.headerGrey;
    row.getCell(2).fill = solidFill(fill);
  }
  boxAllCells(sheet, first, sheet.rowCount, 2);
}

/** The Signatory sheet is likewise identical across returns. */
export function buildSignatorySheet(
  wb: ExcelJS.Workbook,
  signatories: ReturnSignatory[],
  sheetName = 'Signatory'
): void {
  const sheet = wb.addWorksheet(sheetName);
  sheet.columns = [
    { width: 44 },
    { width: 24 }];
  addBanner(sheet, sheetName, 'B');

  for (const person of signatories) {
    const start = sheet.rowCount + 1;
    const head = sheet.addRow([
      person.heading,
      ''
    ]);
    head.font = { bold: true };
    head.alignment = { horizontal: 'center' };
    head.getCell(1).fill = solidFill(XL.keyCell);

    for (const f of SIGNATORY_FIELDS) {
      const row = sheet.addRow([
        person[f.key],
        f.caption
      ]);
      row.getCell(2).font = { bold: true };
      row.getCell(2).alignment = { horizontal: 'center' };
      row.getCell(2).fill = solidFill(XL.keyCell);
    }
    boxAllCells(sheet, start, sheet.rowCount, 2);
    sheet.addRow([]);
  }
}

/** Serialises the workbook and triggers a browser download. */
export async function downloadWorkbook(wb: ExcelJS.Workbook, filename: string): Promise<void> {
  const buffer = await wb.xlsx.writeBuffer();
  const blob = new Blob([buffer], {
    type: 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet'
  });
  const url = URL.createObjectURL(blob);
  const a = document.createElement('a');
  a.href = url;
  a.download = filename;
  document.body.appendChild(a);
  a.click();
  document.body.removeChild(a);
  URL.revokeObjectURL(url);
}

export function newWorkbook(): ExcelJS.Workbook {
  const wb = new ExcelJS.Workbook();
  wb.creator = 'CBSNexora';
  wb.created = new Date();
  return wb;
}