// Lesson note storage format, shared by the client and the server.
//
// Each lesson's notes are stored as one string. Current format (v2):
//   {"v":2,"entries":[{"id","anchor","html","updatedAt"}]}
// Legacy format (v1) was a JSON object of { anchor: html }, and older still was
// plain text. Both are still read and are upgraded to v2 on the next save.

export const NOTE_ANCHORS = ['scripture', 'commentary', 'questions', 'general']

export const NOTE_ANCHOR_LABELS = {
  scripture: 'Scripture Text',
  commentary: 'Commentary',
  questions: 'Reflection Questions',
  general: 'General Notes',
}

export function newNoteId() {
  return `n${Date.now().toString(36)}${Math.random().toString(36).slice(2, 7)}`
}

export function parseNoteEntries(raw) {
  if (typeof raw !== 'string' || !raw.trim()) return []
  let parsed = null
  try {
    parsed = JSON.parse(raw)
  } catch {
    // Legacy plain-text note.
    return [{ id: newNoteId(), anchor: 'general', html: raw, updatedAt: null }]
  }
  if (!parsed || typeof parsed !== 'object' || Array.isArray(parsed)) {
    return [{ id: newNoteId(), anchor: 'general', html: raw, updatedAt: null }]
  }
  if (parsed.v === 2 && Array.isArray(parsed.entries)) {
    return parsed.entries
      .filter(e => e && typeof e.html === 'string' && e.html.trim())
      .map(e => ({
        id: typeof e.id === 'string' && e.id ? e.id : newNoteId(),
        anchor: NOTE_ANCHORS.includes(e.anchor) ? e.anchor : 'general',
        html: e.html,
        updatedAt: typeof e.updatedAt === 'string' ? e.updatedAt : null,
      }))
  }
  return Object.entries(parsed)
    .filter(([, html]) => typeof html === 'string' && html.trim())
    .map(([anchor, html]) => ({
      id: `legacy-${anchor}`,
      anchor: NOTE_ANCHORS.includes(anchor) ? anchor : 'general',
      html,
      updatedAt: null,
    }))
}

export function serializeNoteEntries(entries) {
  const kept = entries.filter(e => e.html && e.html.trim())
  if (kept.length === 0) return ''
  return JSON.stringify({ v: 2, entries: kept })
}

export function noteHtmlToText(html) {
  return String(html)
    .replace(/<\/(p|li|h[1-6]|blockquote)>/gi, '\n')
    .replace(/<br\s*\/?>/gi, '\n')
    .replace(/<[^>]*>/g, '')
    .replace(/&nbsp;/g, ' ')
    .replace(/&lt;/g, '<')
    .replace(/&gt;/g, '>')
    .replace(/&quot;/g, '"')
    .replace(/&#39;/g, "'")
    .replace(/&amp;/g, '&')
    .replace(/\n{3,}/g, '\n\n')
    .trim()
}

// Plain-text rendering of a whole lesson's notes (used by the Word export).
export function noteEntriesToText(raw) {
  return parseNoteEntries(raw)
    .map(e => `${NOTE_ANCHOR_LABELS[e.anchor]}\n${noteHtmlToText(e.html)}`)
    .join('\n\n')
}