// WHY: single source of truth for group -> section, cancelled is reported not placed
function groupToSection(group) {
  switch (group) {
    case 'completed':
      return 'completed';
    case 'started':
      return 'inProgress';
    case 'unstarted':
      return 'todo';
    case 'backlog':
      return 'backlog';
    default:
      return null;
  }
}

function buildDiscrepancies(planeIssues, todoRows, identifier) {
  const todoById = new Map(todoRows.map(row => [row.id, row]));
  const planeById = new Map();
  const cancelled = [];

  for (const issue of planeIssues) {
    const id = `${identifier}-${issue.sequence_id}`;
    const group = (issue.state && issue.state.group) || 'backlog';
    const section = groupToSection(group);
    if (!section) {
      cancelled.push({ id, name: issue.name });
      continue;
    }
    planeById.set(id, { id, name: issue.name, section, group });
  }

  const mismatches = [];
  const newIssues = [];
  const orphans = [];

  for (const [id, p] of planeById) {
    const t = todoById.get(id);
    if (t && t.section !== p.section) mismatches.push({ id, fromSection: t.section, toSection: p.section, name: p.name });
    if (!t) newIssues.push({ id, section: p.section, name: p.name });
  }
  for (const [id, t] of todoById) {
    if (!planeById.has(id)) orphans.push({ id, section: t.section, name: t.name });
  }

  return { mismatches, newIssues, orphans, cancelled, planeById, todoById };
}

// WHY: Plane is authoritative, so plane rows always win; decisions only move/add local rows
function buildFinalSections(buildData, decisions) {
  const final = { completed: [], todo: [], inProgress: [], backlog: [] };
  const { planeById, todoById, mismatches } = buildData;

  for (const [id, p] of planeById) {
    const t = todoById.get(id);
    const note = t ? t.note : '';
    const isMismatch = mismatches.some(m => m.id === id);
    if (isMismatch && !decisions.moveToPlane.has(id)) {
      final[t.section].push({ id, name: p.name, note });
    } else {
      final[p.section].push({ id, name: p.name, note });
    }
  }

  for (const orphan of buildData.orphans) {
    if (decisions.keepOrphan.has(orphan.id)) {
      final[orphan.section].push({ id: orphan.id, name: orphan.name, note: '' });
    }
  }

  return final;
}

module.exports = { groupToSection, buildDiscrepancies, buildFinalSections };