export interface LogQLHistoryItem {
  query: string;
  usageCount: number;
  lastUsedAt: number;
}

const MAX_HISTORY_ITEMS = 20;
const MAX_COMPLETION_ITEMS = 10;

function isHistoryItem(value: unknown): value is LogQLHistoryItem {
  if (typeof value !== 'object' || value === null) return false;
  const item = value as Record<string, unknown>;
  return (
    typeof item.query === 'string' &&
    item.query.trim().length > 0 &&
    typeof item.usageCount === 'number' &&
    Number.isFinite(item.usageCount) &&
    item.usageCount > 0 &&
    typeof item.lastUsedAt === 'number' &&
    Number.isFinite(item.lastUsedAt)
  );
}

function sortByUsage(items: LogQLHistoryItem[]): LogQLHistoryItem[] {
  return [...items].sort((a, b) => b.usageCount - a.usageCount || b.lastUsedAt - a.lastUsedAt);
}

export function readHistory(historyKey: string | undefined): LogQLHistoryItem[] {
  if (!historyKey || typeof window === 'undefined') return [];
  try {
    const value = window.localStorage.getItem(historyKey);
    if (!value) return [];
    const parsed: unknown = JSON.parse(value);
    if (!Array.isArray(parsed)) return [];
    return sortByUsage(parsed.filter(isHistoryItem)).slice(0, MAX_HISTORY_ITEMS);
  } catch {
    return [];
  }
}

export function saveHistory(historyKey: string | undefined, query: string, now = Date.now()): LogQLHistoryItem[] {
  const normalizedQuery = query.trim();
  if (!historyKey || !normalizedQuery || typeof window === 'undefined') return [];

  const history = readHistory(historyKey);
  const existing = history.find((item) => item.query === normalizedQuery);
  const next = existing
    ? history.map((item) => (item === existing ? { ...item, usageCount: item.usageCount + 1, lastUsedAt: now } : item))
    : [...history, { query: normalizedQuery, usageCount: 1, lastUsedAt: now }];
  const sorted = sortByUsage(next).slice(0, MAX_HISTORY_ITEMS);

  try {
    window.localStorage.setItem(historyKey, JSON.stringify(sorted));
  } catch {
    // Storage may be unavailable (e.g. private browsing or a full quota).
  }
  return sorted;
}

export function getHistoryCompletionItems(historyKey: string | undefined): LogQLHistoryItem[] {
  return readHistory(historyKey).slice(0, MAX_COMPLETION_ITEMS);
}