/**
 * Equivalence test: the TypeScript rewrite against the original Luminary099
 * SPSIN / SPCOS, run on the Virtual AGC CPU emulator for every one of the
 * 32,768 possible 15-bit inputs (65,536 calls in all).
 *
 * Usage: node equivalence.test.ts <sp_original.txt>
 */
import { readFileSync } from 'node:fs'
import { spsin, spcos, naiveSin, naiveCos } from './spsin.ts'

/** A 15-bit ones'-complement AGC word to an integer. Negative zero reads as 0. */
const word15 = (w: number) => (w & 0o40000 ? -(~w & 0o37777) : w)
/** The emulator's 16-bit accumulator to an integer, refusing overflowed values. */
function acc16(a: number): number {
  if (((a >> 15) & 1) !== ((a >> 14) & 1)) throw new Error(`overflowed accumulator ${a.toString(8)}`)
  return a & 0o100000 ? -(~a & 0o37777) : a & 0o37777
}

const rows = readFileSync(process.argv[2], 'utf8')
  .trim()
  .split('\n')
  .map((l) => l.split(' ').map((v) => parseInt(v, 8)))

type Fn = (x: number) => number
function compare(name: string, fn: Fn, column: 1 | 2) {
  let mismatches = 0
  let worst = 0
  const examples: string[] = []
  for (const r of rows) {
    const x = word15(r[0])
    const want = acc16(r[column])
    const got = fn(x)
    if (got !== want) {
      mismatches++
      worst = Math.max(worst, Math.abs(got - want))
      if (examples.length < 3) examples.push(`x=${r[0].toString(8).padStart(5, '0')}: original ${want}, rewrite ${got}`)
    }
  }
  console.log(`${name.padEnd(22)} ${rows.length} inputs, ${mismatches} mismatches, worst ${worst} LSB`)
  for (const e of examples) console.log(`    ${e}`)
  return mismatches
}

console.log('Naive rewrite (Math.sin / Math.cos):')
compare('  sin', naiveSin, 1)
compare('  cos', naiveCos, 2)
console.log('Rewrite from intent (fixed-point, flight coefficients):')
const failed = compare('  sin', spsin, 1) + compare('  cos', spcos, 2)
process.exit(failed ? 1 : 0)