import type { PdfFile } from '../pdf/pdfTypes';
import type { MergeMode, MergeQueueItem } from './mergeTypes';

export function createMergeQueueItemId(): string {
  return `merge_${Math.random().toString(36).slice(2)}`;
}

export function moveMergeQueueItem(
  items: MergeQueueItem[],
  itemId: string,
  direction: 'up' | 'down'
): MergeQueueItem[] {
  const index = items.findIndex((item) => item.id === itemId);
  if (index < 0) return items;

  const targetIndex = direction === 'up' ? index - 1 : index + 1;
  if (targetIndex < 0 || targetIndex >= items.length) return items;

  const next = [...items];
  const [item] = next.splice(index, 1);
  next.splice(targetIndex, 0, item);
  return next;
}

export function getReadyMergeQueuePdfs(items: MergeQueueItem[]): PdfFile[] {
  return items
    .filter((item) => item.status === 'ready' && item.pdf)
    .map((item) => item.pdf as PdfFile);
}

export function canMergeQueue(items: MergeQueueItem[]): boolean {
  return (
    items.length > 0 &&
    items.every((item) => item.status === 'ready' && item.pdf !== null)
  );
}

export function hasMergeQueueErrors(items: MergeQueueItem[]): boolean {
  return items.some((item) => item.status === 'error');
}

export function isMergeQueueLoading(items: MergeQueueItem[]): boolean {
  return items.some((item) => item.status === 'loading');
}

export function clampMergeInsertAt(value: string, pageCount: number): number {
  const parsed = Number.parseInt(value, 10);
  if (!Number.isFinite(parsed)) return pageCount;

  return Math.min(Math.max(parsed - 1, 0), pageCount);
}

export function defaultMergeInsertPosition(pageCount: number): string {
  return String(pageCount + 1);
}

export function createMergedPdfName(
  currentPdfName: string | null,
  incomingPdfNames: string[],
  mode: MergeMode
): string {
  const incomingBaseNames = incomingPdfNames.map(stripPdfExtension);

  if (incomingBaseNames.length === 0) {
    return currentPdfName ?? 'merged.pdf';
  }

  if (
    incomingBaseNames.length === 1 &&
    (!currentPdfName || mode === 'overwrite')
  ) {
    return `${incomingBaseNames[0]}_merged.pdf`;
  }

  if (currentPdfName && mode !== 'overwrite') {
    const currentBaseName = stripPdfExtension(currentPdfName);
    return `${currentBaseName}_plus_${incomingBaseNames.length}_pdfs.pdf`;
  }

  return `merged_${incomingBaseNames.length}_pdfs.pdf`;
}

function stripPdfExtension(filename: string): string {
  const base = filename.replace(/\.pdf$/i, '').trim();
  return base || 'document';
}