/**
 * groupSizeUtils.js
 * -----------------------------------------
 * Utilities for group size calculation and
 * print-safe layout generation.
 *
 * Vanilla ECMAScript, framework-agnostic.
 */

/**
 * Create group definitions with base sizes
 * and remainder distribution.
 *
 * @param {number} totalPlayers
 * @param {Array<string>} groupIds
 * @returns {Array<Object>}
 */
export function calculateGroupSizes(totalPlayers, groupIds) {
  if (!Array.isArray(groupIds) || groupIds.length === 0) {
    throw new Error('groupIds must be a non-empty array');
  }

  const totalGroups = groupIds.length;
  const baseSize = Math.floor(totalPlayers / totalGroups);
  const remainder = totalPlayers % totalGroups;

  return groupIds.map(function (id, index) {
    return {
      id: id,
      size: baseSize + (index < remainder ? 1 : 0),
      players: []
    };
  });
}

/**
 * Assign players to groups sequentially
 * based on calculated group sizes.
 *
 * @param {Array<Object>} players
 * @param {Array<Object>} groups
 * @returns {Array<Object>}
 */
export function assignPlayersToGroups(players, groups) {
  var playerIndex = 0;

  groups.forEach(function (group) {
    for (var i = 0; i < group.size; i++) {
      if (playerIndex >= players.length) break;

      var player = players[playerIndex];
      player.groupId = group.id;
      group.players.push(player);

      playerIndex++;
    }
  });

  return groups;
}

/**
 * Remove dropped players without rebalancing groups.
 *
 * @param {Array<Object>} groups
 * @param {Array<string|number>} droppedPlayerIds
 * @returns {Array<Object>}
 */
export function applyDrops(groups, droppedPlayerIds) {
  if (!Array.isArray(droppedPlayerIds)) return groups;

  var dropSet = new Set(droppedPlayerIds);

  groups.forEach(function (group) {
    group.players = group.players.filter(function (player) {
      return !dropSet.has(player.id);
    });
  });

  return groups;
}

/**
 * Calculate print rows for a group.
 *
 * @param {Object} group
 * @param {number} headerRows
 * @param {number} spacerRows
 * @returns {number}
 */
export function calculateGroupPrintRows(group, headerRows, spacerRows) {
  return headerRows + group.players.length + spacerRows;
}

/**
 * Generate print layout with page breaks.
 *
 * @param {Array<Object>} groups
 * @param {Object} options
 * @param {number} options.rowsPerPage
 * @param {number} options.headerRows
 * @param {number} options.spacerRows
 * @returns {Array<Object>}
 */
export function generatePrintLayout(groups, options) {
  var rowsPerPage = options.rowsPerPage;
  var headerRows = options.headerRows || 1;
  var spacerRows = options.spacerRows || 1;

  var pages = [];
  var currentPage = {
    pageNumber: 1,
    groups: [],
    usedRows: 0
  };

  groups.forEach(function (group) {
    var groupRows = calculateGroupPrintRows(group, headerRows, spacerRows);

    if (currentPage.usedRows + groupRows > rowsPerPage) {
      pages.push(currentPage);
      currentPage = {
        pageNumber: currentPage.pageNumber + 1,
        groups: [],
        usedRows: 0
      };
    }

    currentPage.groups.push(group);
    currentPage.usedRows += groupRows;
  });

  pages.push(currentPage);
  return pages;
}

/**
 * High-level helper that runs the full pipeline.
 *
 * @param {Array<Object>} players
 * @param {Array<string>} groupIds
 * @param {Object} printOptions
 * @returns {Array<Object>}
 */
export function buildGroupPrintPages(players, groupIds, printOptions) {
  var groups = calculateGroupSizes(players.length, groupIds);
  assignPlayersToGroups(players, groups);
  return generatePrintLayout(groups, printOptions);
}