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);
  const usdConfig = { ...config, useBackendCost: true };
  assert.equal(computeDeltaCostCents(previous, current, usdConfig), 8);
});