/** 数据资源预览：扩展名分流与展示名。 */

export type DataResourcePreviewKind = "excel" | "text" | "table";

export const EXCEL_EXTENSIONS = [".xlsx", ".xls"] as const;
export const TEXT_EXTENSIONS = [".txt", ".json"] as const;
export const TABLE_EXTENSIONS = [".csv", ".tsv"] as const;

/** Excel 整文件拉取上限。 */
export const EXCEL_PREVIEW_MAX_BYTES = 80 * 1024 * 1024;
/** 文本预览拉取上限。 */
export const TEXT_PREVIEW_MAX_BYTES = 5 * 1024 * 1024;

export type DataResourcePreviewTarget = {
  resourceId: string;
  resourceName: string;
  fileExtension: string | null;
  sizeBytes: number;
  kind: DataResourcePreviewKind;
};

function lowerName(name: string | null | undefined): string {
  return (name ?? "").toLowerCase();
}

function matchesExt(name: string, exts: readonly string[]): boolean {
  return exts.some((ext) => name.endsWith(ext));
}

export function isExcelFileName(name: string | null | undefined): boolean {
  return matchesExt(lowerName(name), EXCEL_EXTENSIONS);
}

export function isTextPreviewFileName(name: string | null | undefined): boolean {
  return matchesExt(lowerName(name), TEXT_EXTENSIONS);
}

export function isTablePreviewFileName(name: string | null | undefined): boolean {
  return matchesExt(lowerName(name), TABLE_EXTENSIONS);
}

export function previewKindFromFileName(
  name: string | null | undefined,
): DataResourcePreviewKind | null {
  const lower = lowerName(name);
  if (matchesExt(lower, EXCEL_EXTENSIONS)) return "excel";
  if (matchesExt(lower, TEXT_EXTENSIONS)) return "text";
  if (matchesExt(lower, TABLE_EXTENSIONS)) return "table";
  return null;
}

export function canPreviewDataResource(name: string | null | undefined): boolean {
  return previewKindFromFileName(name) !== null;
}

export function resourceDisplayName(
  resourceName: string,
  fileExtension: string | null | undefined,
): string {
  if (!fileExtension) return resourceName;
  const ext = fileExtension.startsWith(".")
    ? fileExtension
    : `.${fileExtension}`;
  if (resourceName.toLowerCase().endsWith(ext.toLowerCase())) {
    return resourceName;
  }
  return `${resourceName}${ext}`;
}

/** @deprecated use resourceDisplayName */
export const excelDisplayName = resourceDisplayName;

export function monacoLanguageFromFileName(name: string): string {
  const lower = lowerName(name);
  if (lower.endsWith(".json")) return "json";
  return "plaintext";
}