/**
 * CSV Parsing Utilities
 * Functions for parsing and validating CSV files (RK9 player registrations)
 */

import { EXPECTED_CSV_HEADERS, CSV_HEADERS } from './constants.js';

/**
 * Validate CSV headers against expected format
 * @param {string[]} headers - Array of header names from CSV
 * @throws {Error} If headers are invalid or missing required fields
 */
export function validateCsvHeaders(headers) {
  if (!headers || headers.length === 0) {
    throw new Error('CSV file is missing headers');
  }

  if (headers.length !== EXPECTED_CSV_HEADERS.length) {
    throw new Error(
      `Invalid CSV file headers: Expected ${EXPECTED_CSV_HEADERS.length} headers but found ${headers.length}`
    );
  }

  const missingHeaders = EXPECTED_CSV_HEADERS.filter(
    expectedHeader => !headers.includes(expectedHeader)
  );

  if (missingHeaders.length > 0) {
    throw new Error(
      `Invalid CSV file headers: Missing the following headers: ${missingHeaders.join(', ')}`
    );
  }
}

/**
 * Parse CSV text content into structured player data
 * @param {string} csvData - Raw CSV file content
 * @returns {Object} Object keyed by screenname with player data
 * @throws {Error} If CSV format is invalid
 */
export function parseCsv(csvData) {
  const rows = csvData
    .split('\n')
    .map(row => row.split(','))
    .filter(row => row.some(cell => cell.trim() !== ''));

  if (rows.length === 0) {
    throw new Error('CSV file is empty');
  }

  const headers = rows[0].map(header => header.trim());
  validateCsvHeaders(headers);

  // Validate row format
  for (let i = 1; i < rows.length; i++) {
    if (rows[i].length !== EXPECTED_CSV_HEADERS.length) {
      throw new Error(`Invalid row format at line ${i + 1}`);
    }
  }

  // Parse rows into objects
  return rows.slice(1).reduce((acc, row) => {
    const participant = {};
    EXPECTED_CSV_HEADERS.forEach((header, idx) => {
      participant[header] = row[idx]?.trim();
    });
    acc[participant[CSV_HEADERS.SCREENNAME]] = participant;
    return acc;
  }, {});
}

/**
 * Parse CSV file from browser File API
 * @param {File} file - File object from input[type=file]
 * @returns {Promise<Object>} Parsed player data
 */
export async function parsePlayerCsvFile(file) {
  if (!file) {
    throw new Error('No file provided');
  }

  if (!file.name.endsWith('.csv')) {
    throw new Error('File must be a CSV file');
  }

  const text = await file.text();
  return parseCsv(text);
}

/**
 * Convert parsed CSV data to array format
 * @param {Object} csvObject - Object from parseCsv
 * @returns {Array} Array of player objects with screenname included
 */
export function csvObjectToArray(csvObject) {
  return Object.entries(csvObject).map(([screenname, data]) => ({
    ...data,
    screenname
  }));
}

/**
 * Validate individual player data
 * @param {Object} player - Player data object
 * @returns {Object} Validation result {valid: boolean, errors: string[]}
 */
export function validatePlayerData(player) {
  const errors = [];

  if (!player[CSV_HEADERS.PLAYER_ID]) {
    errors.push('Missing player_id');
  }

  if (!player[CSV_HEADERS.SCREENNAME]) {
    errors.push('Missing screenname');
  }

  if (!player[CSV_HEADERS.DIVISION]) {
    errors.push('Missing division');
  }

  const email = player[CSV_HEADERS.EMAIL];
  if (email && !isValidEmail(email)) {
    errors.push('Invalid email format');
  }

  return {
    valid: errors.length === 0,
    errors
  };
}

/**
 * Simple email validation
 * @param {string} email - Email address to validate
 * @returns {boolean} True if email format is valid
 */
function isValidEmail(email) {
  return /^[^\s@]+@[^\s@]+\.[^\s@]+$/.test(email);
}