// Headless validation of the solver — runs the same MATLAB script the
// browser worker runs, in Node, against the installed numbl. Each solve
// fills matlab/solve_template.m with the parameters (mirroring
// buildSolveScript in src/engine/engine.ts), runs it standalone (as the
// browser does in a fresh session), and reads result.json back from the
// VFS. The VFS is shared across solves, standing in for numbl/browser's
// IndexedDB-persisted /system, so `mip load --install surfacefun` only
// downloads once. Node has no synchronous XMLHttpRequest, so
// websave/webread are shimmed with curl (responses cached in .cache/ keyed
// by URL, so repeat runs are offline).
//
//   npm run engine-test

import {
  executeCode,
  VirtualFileSystem,
  BrowserFileIOAdapter,
  BrowserSystemAdapter,
} from 'numbl'
import {unzipSync} from 'fflate'
import {execFileSync} from 'node:child_process'
import crypto from 'node:crypto'
import fs from 'node:fs'
import path from 'node:path'
import {fileURLToPath} from 'node:url'

const root = path.dirname(path.dirname(fileURLToPath(import.meta.url)))
const cacheDir = path.join(root, '.cache')

const MIP_MHL_URL =
  'https://github.com/mip-org/mip-core/releases/download/mip-numbl/mip-numbl-any.mhl'
const MIP_SYSTEM_PREFIX = '/system/mip/packages/gh/mip-org/core/mip/'
// In the browser this is passed by numbl/browser's session worker; executeCode
// scans searchPaths directories since the same numbl change.
const MIP_SEARCH_PATH = MIP_SYSTEM_PREFIX + 'mip'

function curlCached(url) {
  fs.mkdirSync(cacheDir, {recursive: true})
  const key = crypto.createHash('sha1').update(url).digest('hex').slice(0, 16)
  const cached = path.join(cacheDir, key)
  if (!fs.existsSync(cached)) {
    console.log(`fetching ${url}`)
    execFileSync('curl', ['-sfL', '-o', cached, url], {stdio: 'inherit'})
  }
  return fs.readFileSync(cached)
}

// numbl's BrowserFileIOAdapter implements websave/webread with synchronous
// XHR (fine in a web worker, absent in Node); override with curl.
class NodeFileIOAdapter extends BrowserFileIOAdapter {
  constructor(vfs) {
    super(vfs)
    this.nodeVfs = vfs
  }
  websave(url, filename) {
    this.nodeVfs.writeFile(this.nodeVfs.normalizePath(filename), new Uint8Array(curlCached(url)))
  }
  webread(url) {
    return curlCached(url).toString('utf8')
  }
}

const template = fs.readFileSync(path.join(root, 'matlab', 'solve_template.m'), 'utf8')

// Mirrors buildSolveScript in src/engine/engine.ts.
const buildSolveScript = params => {
  const fills = {
    MESHFILE: 'mesh.msh',
    PDE: params.pde,
    F_EXPR: params.f,
    C_EXPR: params.pde === 'helmholtz' ? params.c : '0',
    ORDER: String(params.p),
    CLOSED: params.closed ? 'true' : 'false',
  }
  return template.replace(/\{\{(\w+)\}\}/g, (token, key) => fills[key] ?? token)
}

async function main() {
  const vfs = new VirtualFileSystem()
  const enc = new TextEncoder()

  // Bootstrap mip into the system VFS, as the browser worker does.
  const mipEntries = unzipSync(new Uint8Array(curlCached(MIP_MHL_URL)))
  let nMip = 0
  for (const [name, content] of Object.entries(mipEntries)) {
    if (name.endsWith('/')) continue
    vfs.writeFile(MIP_SYSTEM_PREFIX + name, content)
    nMip++
  }
  console.log(`mip core: ${nMip} files into VFS`)

  vfs.writeFile(
    '/project/mesh.msh',
    fs.readFileSync(path.join(root, 'public', 'samples', 'sphere.msh'))
  )
  vfs.setCwd('/project')

  const decoder = new TextDecoder()

  const solve = params => {
    const script = buildSolveScript(params)
    vfs.writeFile('/project/solve_pde.m', enc.encode(script))
    vfs.writeFile('/project/result.json', enc.encode('')) // no stale reads
    const t = Date.now()
    executeCode(
      script,
      {
        onOutput: text => process.stdout.write(`[numbl] ${text}`),
        onDrawnow: () => {},
        displayResults: false,
        maxIterations: 1e9,
        optimization: '1',
        fileIO: new NodeFileIOAdapter(vfs),
        system: new BrowserSystemAdapter(vfs),
      },
      [{name: 'solve_pde.m', source: script}],
      vfs.normalizePath('/project/solve_pde.m'),
      [MIP_SEARCH_PATH]
    )
    const result = JSON.parse(decoder.decode(vfs.readFile('/project/result.json')))
    console.log(`solve [${params.pde}] in ${(Date.now() - t) / 1000}s`)
    return result
  }

  // 1. Poisson on the closed sphere
  let d = solve({pde: 'poisson', f: 'x.*y.*z', c: '', p: 6, closed: true})
  console.log(`  npatches=${d.npatches} n=${d.n} u in [${d.umin.toFixed(6)}, ${d.umax.toFixed(6)}]`)
  if (d.npatches !== 216 || d.n !== 7 || d.ptype !== 'quad')
    throw new Error('unexpected solution shape')
  if (!isFinite(d.umin) || !isFinite(d.umax) || d.umin === d.umax)
    throw new Error('degenerate solution values')

  // Eigenfunction check: x*y*z is a degree-3 solid harmonic, so on the unit
  // sphere lap_S (x*y*z) = -12 * (x*y*z). Solving with f = -12*x*y*z must
  // reproduce u = x*y*z, whose max on the sphere is 1/(3*sqrt(3)).
  d = solve({pde: 'poisson', f: '-12*(x.*y.*z)', c: '', p: 8, closed: true})
  const expected = 1 / (3 * Math.sqrt(3))
  console.log(`  eigencheck: umax=${d.umax.toFixed(6)} expected~${expected.toFixed(6)}`)
  if (Math.abs(d.umax - expected) > 0.01) throw new Error('eigenfunction check failed')

  // 2. Helmholtz with a variable coefficient
  d = solve({pde: 'helmholtz', f: '1 + 0*x', c: '100*(1 - z)', p: 6, closed: true})
  console.log(`  u in [${d.umin.toFixed(6)}, ${d.umax.toFixed(6)}]`)

  // 3. Bad expression errors out of the run (the host surfaces the message)
  let err = null
  try {
    solve({pde: 'poisson', f: 'this is not matlab', c: '', p: 4, closed: true})
  } catch (e) {
    err = e
  }
  if (!err) throw new Error('expected an error for bad expression')
  console.log(`  error path OK: ${String(err.message).slice(0, 100)}`)

  // 4. A later solve is unaffected (fresh run per solve)
  d = solve({pde: 'poisson', f: 'x', c: '', p: 4, closed: true})
  if (d.type !== 'solution') throw new Error('solve after error failed')

  // 5. Triangle mesh: the same eigenfunction check on an icosahedral sphere.
  // Flat triangles hug the sphere worse than the cubed sphere's bilinear
  // quads, so geometry error dominates: umax is ~0.0107 low at this
  // subdivision level and shrinks 4x per level (O(h^2)) — hence the wider
  // tolerance.
  vfs.writeFile(
    '/project/mesh.msh',
    fs.readFileSync(path.join(root, 'public', 'samples', 'sphere-tri.msh'))
  )
  d = solve({pde: 'poisson', f: '-12*(x.*y.*z)', c: '', p: 6, closed: true})
  console.log(`  tri eigencheck: umax=${d.umax.toFixed(6)} expected~${expected.toFixed(6)}`)
  if (d.ptype !== 'tri' || d.npatches !== 320 || d.n !== 7)
    throw new Error('unexpected triangle solution shape')
  if (Math.abs(d.umax - expected) > 0.015)
    throw new Error('triangle eigenfunction check failed')

  // Helmholtz with a variable coefficient also works on triangle patches
  d = solve({pde: 'helmholtz', f: '1 + 0*x', c: '100*(1 - z)', p: 6, closed: true})
  console.log(`  tri helmholtz: u in [${d.umin.toFixed(6)}, ${d.umax.toFixed(6)}]`)
  if (d.ptype !== 'tri' || !isFinite(d.umin) || d.umin === d.umax)
    throw new Error('triangle helmholtz solve failed')

  console.log('engine-test: all checks passed')
}

main().catch(err => {
  console.error(err)
  process.exit(1)
})