import test from 'node:test';
import assert from 'node:assert/strict';
import { computeDeltaCostCents, normalizeTokenState } from './billing.mjs';

const config = {
  useBackendCost: false,
  usdCnyRate: 7.2,
  inputCentsPer1k: 2,
  outputCentsPer1k: 6,
  minBillCents: 1,
};

test('normalizeTokenState reads camelCase fields', () => {
  const state = normalizeTokenState({
    inputTokens: 10,
    outputTokens: 20,
    accumulatedInputTokens: 100,
    accumulatedOutputTokens: 200,
  });
  assert.equal(state.accumulatedInputTokens, 100);
  assert.equal(state.accumulatedOutputTokens, 200);
});

test('computeDeltaCostCents bills token deltas', () => {
  const previous = { lastInputTokens: 1000, lastOutputTokens: 500 };
  const current = normalizeTokenState({
    accumulatedInputTokens: 2000,
    accumulatedOutputTokens: 1500,
  });
  const cost = computeDeltaCostCents(previous, current, config);
  assert.equal(cost, 8);
});

test('computeDeltaCostCents returns zero when no usage delta', () => {
  const previous = { lastInputTokens: 1000, lastOutputTokens: 500 };
  const current = normalizeTokenState({
    accumulatedInputTokens: 1000,
    accumulatedOutputTokens: 500,
  });
  assert.equal(computeDeltaCostCents(previous, current, config), 0);
});

test('computeDeltaCostCents ignores backend USD cost unless explicitly enabled', () => {
  const previous = { lastInputTokens: 0, lastOutputTokens: 0, lastAccumulatedCost: 0.01 };
  const current = normalizeTokenState({
    accumulatedInputTokens: 1000,
    accumulatedOutputTokens: 500,
    accumulatedCost: 0.02,
  });
  const rmbConfig = { ...config, useBackendCost: false };
  assert.equal(computeDeltaCostCents(previous, current, rmbConfig), 5);
  // 成本模式默认 margin=1：deltaUsd 0.01 × 7.2 × 100 = 7.2 → ceil = 8
  const usdConfig = { ...config, useBackendCost: true, marginMultiplier: 1 };
  assert.equal(computeDeltaCostCents(previous, current, usdConfig), 8);
});

test('computeDeltaCostCents applies margin multiplier in cost mode', () => {
  const previous = { lastInputTokens: 0, lastOutputTokens: 0, lastAccumulatedCost: 0 };
  const current = normalizeTokenState({
    accumulatedInputTokens: 1_000_000,
    accumulatedOutputTokens: 10_000,
    accumulatedCost: 0.25,
  });
  // deltaUsd 0.25 × 7.2 × 100 × 3 = 540 分（而非 flat token 的 2060 分）
  const costConfig = { ...config, useBackendCost: true, marginMultiplier: 3 };
  assert.equal(computeDeltaCostCents(previous, current, costConfig), 540);
});

test('computeDeltaCostCents falls back to token path when accumulatedCost missing', () => {
  const previous = { lastInputTokens: 0, lastOutputTokens: 0 };
  const current = normalizeTokenState({
    accumulatedInputTokens: 1000,
    accumulatedOutputTokens: 500,
    // 上游未回传 accumulatedCost → 即便开启成本模式也回退 token 计费
  });
  const costConfig = { ...config, useBackendCost: true, marginMultiplier: 3 };
  assert.equal(computeDeltaCostCents(previous, current, costConfig), 5);
});