// Pure helpers for ExportRoomHistory.tsx, kept SDK/DOM-free so they're easy to
// unit test in isolation.

export type RawExportRecord = {
  eventId: string;
  ts: number;
  sender: string;
  body: string;
  msgtype: string;
  // Set when this record IS an m.replace edit event, to the event id it targets.
  editsEventId?: string;
  // The m.new_content.body carried by an m.replace edit event.
  newBody?: string;
};

export type ResolvedExportRecord = {
  eventId: string;
  ts: number;
  sender: string;
  body: string;
  msgtype: string;
  edited: boolean;
};

// Human-readable label for media msgtypes, used to prefix txt/html export rows
// so a media message isn't indistinguishable from a plain-text one.
export const MEDIA_TYPE_LABELS: Partial<Record<string, string>> = {
  'm.image': 'Image',
  'm.video': 'Video',
  'm.audio': 'Audio',
  'm.file': 'File',
};

/**
 * Resolves m.replace (edit) events against the original message they target:
 * the edit event is dropped from the output (it should not appear as its own
 * row), and the original message's body is replaced with the edit's
 * `m.new_content.body`, marked `edited: true`.
 *
 * Order-independent: edits may appear before or after their target in the
 * input (e.g. across separate back-pagination batches).
 */
export function resolveMessageEdits(records: RawExportRecord[]): ResolvedExportRecord[] {
  const edits = new Map<string, string>();
  for (const record of records) {
    if (record.editsEventId && record.newBody) {
      edits.set(record.editsEventId, record.newBody);
    }
  }

  const resolved: ResolvedExportRecord[] = [];
  for (const record of records) {
    // Edit events never become their own row.
    if (record.editsEventId) continue;
    const editedBody = edits.get(record.eventId);
    resolved.push({
      eventId: record.eventId,
      ts: record.ts,
      sender: record.sender,
      body: editedBody ?? record.body,
      msgtype: record.msgtype,
      edited: editedBody !== undefined,
    });
  }
  return resolved;
}

// Prefixes a media message's body with a "[Image]"-style marker for txt/html
// export output, and appends an "(edited)" suffix when applicable. Plain-text
// messages are returned unchanged (aside from the edited suffix).
export function formatExportBody(record: ResolvedExportRecord): string {
  const label = MEDIA_TYPE_LABELS[record.msgtype];
  const mediaPrefix = label ? `[${label}] ` : '';
  const editedSuffix = record.edited ? ' (edited)' : '';
  return `${mediaPrefix}${record.body}${editedSuffix}`;
}