@web-alchemy/fonttools/modules/subset/subset.js

This is the Node.js adapter of [python font tools](https://github.com/fonttools/fonttools) via [Pyodide](https://pyodide.org) without having to install python and its dependencies.

const fs = require('fs')
const { preparePyodide, PyodideFile } = require('../../pyodide.js')
const { getPythonSubsetFunction } = require('./get-python-subset-function.js')

function prepareOptions(options) {
  return Object.entries(options)
    .map(([key, value]) => {
      if (key === "*") return "*"
      if (value === true) return `--${key}`
      return `--${key}=${value}`
    })
}

async function subset(inputFontBuffer, options) {
  const pyodide = await preparePyodide()

  const files = []
  const inputFile = new PyodideFile({ pyodide })
  const outputFile = new PyodideFile({ pyodide })
  files.push(inputFile)
  files.push(outputFile)

  inputFile.upload(inputFontBuffer)

  options['output-file'] = outputFile.filename

  for (const paramName of ['gids-file', 'glyphs-file', 'text-file', 'unicodes-file']) {
    if (!options[paramName]) {
      continue
    }
    const filePath = options[paramName]
    const file = new PyodideFile({ pyodide })
    const fileBuffer = await fs.promises.readFile(filePath)
    await file.upload(fileBuffer)
    options[paramName] = file.filename
    files.push(file)
  }

  const preparedOptions = [inputFile.filename, ...prepareOptions(options)]
  const pythonFunction = await getPythonSubsetFunction(pyodide)
  pythonFunction(preparedOptions)

  const processedFileBuffer = outputFile.download()

  for (const file of files) {
    file.delete()
  }

  return processedFileBuffer
}

module.exports = {
  subset
}