// ============================================================
// test_three_body_integrator.js - 穿越三体 · 三体积分器校验
// 从 public/tools/thought_lab/labs/three_body_journey/index.html 抽取
// THREEBODY_MATH_BEGIN/END 之间的纯物理代码执行校验（测试对象 = 上线代码）。
// 校验：RK4 积分动量守恒、能量漂移极小、加速度满足牛顿第三定律对称性。
// 运行：node dev_test_scripts/unit/test_three_body_integrator.js
// ============================================================
'use strict'
const fs = require('fs')
const path = require('path')
const vm = require('vm')

const HTML = path.resolve(__dirname, '..', '..', 'public', 'tools', 'thought_lab', 'labs', 'three_body_journey', 'index.html')
const src = fs.readFileSync(HTML, 'utf8')
const m = src.match(/\/\/ ==== THREEBODY_MATH_BEGIN ====\n([\s\S]*?)\/\/ ==== THREEBODY_MATH_END ====/)
if (!m) { console.error('FAIL - 未找到 THREEBODY_MATH 标记块'); process.exit(1) }

const api = vm.runInNewContext(m[1] + ';({ tbAccel, tbStep, tbEnergy, tbMomentum })')

let pass = 0, fail = 0
const check = (name, cond) => {
  if (cond) { pass++; console.log('PASS -', name) }
  else { fail++; console.log('FAIL -', name) }
}

const masses = [1, 1, 1]
const eps2 = 0.02
let pos = [1, 0, -0.5, Math.sqrt(3) / 2, -0.5, -Math.sqrt(3) / 2]
let vel = [0, 0.42, -0.38, -0.2, 0.38, -0.22]

// 牛顿第三定律：Σ mᵢaᵢ = 0（作用力反作用力，任意位形）
{
  const ms = [1, 2, 0.5]
  const a = api.tbAccel([0, 0, 1, 0.3, -0.7, 1.2], ms, 0)
  let sx = 0, sy = 0
  for (let i = 0; i < 3; i++) { sx += ms[i] * a[2 * i]; sy += ms[i] * a[2 * i + 1] }
  check('Σ mᵢaᵢ = 0（作用反作用）', Math.abs(sx) < 1e-12 && Math.abs(sy) < 1e-12)
}

// 动量守恒：跑 5000 步
const p0 = api.tbMomentum(vel, masses)
const E0 = api.tbEnergy(pos, vel, masses, eps2)
for (let i = 0; i < 5000; i++) [pos, vel] = api.tbStep(pos, vel, masses, 0.002, eps2)
const p1 = api.tbMomentum(vel, masses)
const E1 = api.tbEnergy(pos, vel, masses, eps2)
check('动量守恒（5000 步，|Δp|<1e-9）', Math.abs(p1[0] - p0[0]) < 1e-9 && Math.abs(p1[1] - p0[1]) < 1e-9)
check(`能量漂移小（|ΔE/E0|<1e-3，实际 ${Math.abs((E1 - E0) / E0).toExponential(2)}）`, Math.abs((E1 - E0) / E0) < 1e-3)

// 有限性：5000 步后位置/速度均为有限数（软化避免奇点崩溃）
check('积分稳定（全部有限）', [...pos, ...vel].every(Number.isFinite))

console.log(fail === 0 ? `ALL PASS (${pass})` : `FAILED: ${fail} / ${pass + fail}`)
process.exit(fail === 0 ? 0 : 1)