printservant/index.js

require('console-stamp')(console)

const ipp = require('ipp')
const express = require('express')
const bodyParser = require('body-parser')

// --- Config ---

const PORT = Number(process.env.PRINTSERVANT_PORT) || 3199
const CONFIG = JSON.parse(process.env.PRINTSERVANT_CONFIG || 'null')
const MAX_SIZE_MB = Number(process.env.PRINTSERVANT_MAX_SIZE_MB) || 10

if (!(PORT && CONFIG)) {
  throw new Error("PRINTSERVANT_PORT and PRINTSERVANT_CONFIG environment variables must be set")
}

const printers = []

for (const printerConfig of CONFIG.printers) {
  const { name, aliases = [], ipp_url } = printerConfig

  if (!(name && ipp_url)) {
    throw new Error("Printer config must have a name and url")
  }

  const ippPrinter = ipp.Printer(ipp_url)

  printers.push({ name, aliases, ippPrinter })
}

const printerMap = new Map()
printers.forEach(printer => {
  printerMap.set(printer.name.toLowerCase(), printer)
  printer.aliases.forEach(alias => {
    printerMap.set(alias.toLowerCase(), printer)
  })
})

function getPrinter(name) {
  return printerMap.get(name.toLowerCase())
}

// --- Debug API ---

const app = express()

app.get('/', (req, res) => {
  res.send(`<pre>Hello world! API routes available:
    - GET /
    - GET /health
    - GET /printers
      - Lists all printers (names and aliases)
    - GET /printers/:name/attributes
      - Prints IPP attributes
    - GET /printers/:name/jobs
      - Prints IPP jobs
    - POST /print?printer=:name
      - Prints a PDF
      - ?printer= printer name or alias (case insensitive)
      - ?copies= (optional) number of copies (1-10 allowed)
      - Body: PDF or PNG data; *or* any data if Content-Type header is passed
      - Response: 200 OK if sent to printer successfully (not necessarily printed), 4xx/5xx otherwise
  </pre>`)
})

app.get('/health', (req, res) => {
  res.send(`Printservant is healthy (probably)`)
})

app.get('/printers', (req, res) => {
  res.send(printers.map(({ name, aliases }) => ({ name, aliases })))
})

function executeSimpleCommand(printerName, command, res) {
  const printer = getPrinter(printerName)
  if (!printer) {
    console.log(`Printer '${printerName}' not found`)
    res.status(404).send(`Printer '${printerName}' not found`)
    return
  }

  printer.ippPrinter.execute(command, null, function (error, result) {
    if (error || result.statusCode !== 'successful-ok') {
      console.error(error || result);
      res.status(500)
    }

    res.send({ result, error })
  });
}

app.get('/printers/:name/attributes', (req, res) => {
  const { name } = req.params
  console.log(`Getting attributes for printer: '${name}'`)
  executeSimpleCommand(name, "Get-Printer-Attributes", res)
})

app.get('/printers/:name/jobs', (req, res) => {
  const { name } = req.params
  console.log(`Getting jobs for printer: '${name}'`)
  executeSimpleCommand(name, "Get-Jobs", res)
})

// --- Print API ---

app.post('/print', bodyParser.raw({ type: () => true, limit: MAX_SIZE_MB * 1_000_000 }), (req, res) => {
  const { body, query, headers } = req
  console.log("Received print job: ", { body, query })

  // validate query params
  const { printer: printerName, copies: copiesParam, ...otherParams } = query
  if (!printerName) {
    res.status(400).send("No printer specified, pass ?printer=:name in the query params")
    return
  } else if (Object.keys(otherParams).length) {
    res.status(400).send("Unknown query params, only ?printer=:name is supported")
    return
  }

  const printer = getPrinter(printerName)
  if (!printer) {
    console.log(`Printer '${name}' not found`)
    res.status(404).send(`Printer '${name}' not found`)
    return
  }

  // validate body
  if (!body || !body.length) {
    res.status(400).send("No data received")
    return
  }

  const contentType = headers['content-type']
  const hasValidContentType = contentType
    && contentType !== 'application/octet-stream'
    && contentType !== 'application/x-www-form-urlencoded'

  const isPDF = body.subarray(0, 4).toString() === "%PDF"
  const isPNG = body.subarray(0, 8).equals(Buffer.from([0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a]))

  const hasValidFormat = isPDF || isPNG || hasValidContentType
  if (!hasValidFormat) {
    res.status(415).send("Unknown media type. Pass a PDF or PNG file, or set Content-Type header to print something else.")
    return
  }

  // validate job attributes
  const copies = Number(copiesParam) || 1
  if (!(copies >= 1 && copies <= 10)) {
    res.status(400).send("Copies must be between 1 and 10")
    return
  }

  // send print job
  const msg = {
    "operation-attributes-tag": {
      "document-format": (() => {
        if (isPDF) return "application/pdf"
        if (isPNG) return "image/png"
        if (contentType) return contentType
        throw new Error('unreachable')
      })(),
    },
    "job-attributes-tag": {
      "copies": copies,
    },
    data: body
  };
  console.log("Sending print job: ", msg)

  printer.ippPrinter.execute("Print-Job", msg, function(error, result){
    console.log({ result, error });

    if (error) {
      res.status(500)
    } else if (result.statusCode !== 'successful-ok') {
      res.status(400) // not sure, depends lol
    }

    res.send({ result, error })
  });
})

// --- Let's goooooooo ---

app.listen(PORT, () => {
  console.log(`printservant listening on port ${PORT}`)
})