import type { WeeklyExportBundle } from "../telemetry/weekly-export.js";

/**
 * What the bundle contains, not the bundle itself.
 *
 * This used to concatenate all fifteen files — every JSONL row and every JSON blob — into a single
 * notification, which is not a preview of anything a person can read. The point of previewing is to
 * decide whether to export, so it shows the shape and the head of each file.
 */
export function formatExportPreview(bundle: WeeklyExportBundle, headLines = 3): string {
  const files = Object.entries(bundle.files);
  const width = Math.max(0, ...files.map(([file]) => file.length));
  return [
    `UltraPi export preview for ${bundle.week}: ${files.length} files, nothing written yet.`,
    "",
    ...files.flatMap(([file, contents]) => {
      const lines = contents.split("\n").filter(Boolean);
      const head = lines.slice(0, headLines).map((line) => `    ${line.length > 160 ? `${line.slice(0, 157)}...` : line}`);
      return [
        `${file.padEnd(width)}  ${lines.length} line${lines.length === 1 ? "" : "s"}, ${contents.length} chars`,
        ...head,
        ...(lines.length > head.length ? [`    ... ${lines.length - head.length} more`] : []),
      ];
    }),
    "",
    "Run /ultra-config export week to write it.",
  ].join("\n");
}