Function buildCostReport

src/lib/usage-scanner.ts:127–265

(filterDays?: number)

 * Build full cost report from JSONL data
 */
export async function buildCostReport(filterDays?: number) {
  const allEntries = await scanAllUsage();

  const now = new Date();
  const todayStr = now.toISOString().split("T")[0];
  const yesterday = new Date(now);
  yesterday.setDate(yesterday.getDate() - 1);
  const yesterdayStr = yesterday.toISOString().split("T")[0];
  const thisMonthPrefix = `${now.getFullYear()}-${String(now.getMonth() + 1).padStart(2, "0")}`;
  const lastMonth = new Date(now.getFullYear(), now.getMonth() - 1, 1);
  const lastMonthPrefix = `${lastMonth.getFullYear()}-${String(lastMonth.getMonth() + 1).padStart(2, "0")}`;

  // Filter by timeframe if specified
  let cutoffDate = "";
  if (filterDays) {
    const cutoff = new Date(now);
    cutoff.setDate(cutoff.getDate() - filterDays);
    cutoffDate = cutoff.toISOString().split("T")[0];
  }

  const filtered = cutoffDate
    ? allEntries.filter((e) => e.date >= cutoffDate)
    : allEntries;

  // Calculate costs for each entry
  function entryCost(e: UsageEntry): number {
    return calculateCost(e.model, e.inputTokens, e.outputTokens, e.cacheReadTokens, e.cacheWriteTokens);
  }

  // Summary costs
  const todayEntries = allEntries.filter((e) => e.date === todayStr);
  const yesterdayEntries = allEntries.filter((e) => e.date === yesterdayStr);
  const thisMonthEntries = allEntries.filter((e) => e.date.startsWith(thisMonthPrefix));
  const lastMonthEntries = allEntries.filter((e) => e.date.startsWith(lastMonthPrefix));

  const todayCost = todayEntries.reduce((s, e) => s + entryCost(e), 0);
  const yesterdayCost = yesterdayEntries.reduce((s, e) => s + entryCost(e), 0);
  const thisMonthCost = thisMonthEntries.reduce((s, e) => s + entryCost(e), 0);
  const lastMonthCost = lastMonthEntries.reduce((s, e) => s + entryCost(e), 0);

  const daysInMonth = new Date(now.getFullYear(), now.getMonth() + 1, 0).getDate();
  const daysElapsed = now.getDate();
  const projected = daysElapsed > 0 ? (thisMonthCost / daysElapsed) * daysInMonth : 0;

  // By agent
  const agentMap = new Map<string, { cost: number; tokens: number; in: number; out: number; cr: number; cw: number; msgs: number }>();
  for (const e of filtered) {
    const key = e.agentId;
    const prev = agentMap.get(key) || { cost: 0, tokens: 0, in: 0, out: 0, cr: 0, cw: 0, msgs: 0 };
    prev.cost += entryCost(e);
    prev.tokens += e.totalTokens;
    prev.in += e.inputTokens;
    prev.out += e.outputTokens;
    prev.cr += e.cacheReadTokens;
    prev.cw += e.cacheWriteTokens;
    prev.msgs += 1;
    agentMap.set(key, prev);
  }