// SPDX-FileCopyrightText: 2026 ExoPro. Inspired by @jasonish/pi-prompt-history
// SPDX-License-Identifier: MIT

import fs from "node:fs";

interface SharedHistoryEntry {
  text: string;
}

function isSharedHistoryEntry(value: unknown): value is SharedHistoryEntry {
  if (!value || typeof value !== "object") return false;
  return typeof (value as { text?: unknown }).text === "string";
}

function toSharedHistoryValue(value: unknown): string | null {
  if (typeof value === "string") return value.length > 0 ? value : null;
  if (isSharedHistoryEntry(value))
    return value.text.length > 0 ? value.text : null;
  return null;
}

function isNonEmptyString(value: string | null): value is string {
  return typeof value === "string" && value.length > 0;
}

export function loadSharedHistory(historyFile: string): string[] {
  if (!fs.existsSync(historyFile)) return [];

  try {
    const raw = fs.readFileSync(historyFile, "utf8");
    const parsed: unknown = JSON.parse(raw);

    if (!Array.isArray(parsed)) return [];

    return parsed.map(toSharedHistoryValue).filter(isNonEmptyString);
  } catch {
    return [];
  }
}