farmer.js

const { Vec3 } = require('vec3')
const mineflayer = require('mineflayer')

if (process.argv.length < 4 || process.argv.length > 6) {
  console.log('Usage : node farmer.js <host> <port> [<name>] [<password>]')
  process.exit(1)
}

const bot = mineflayer.createBot({
  host: process.argv[2],
  port: parseInt(process.argv[3]),
  username: process.argv[4] ? process.argv[4] : 'farmer',
  password: process.argv[5]
})

// To fish we have to give bot the seeds
// /give farmer wheat_seeds 64

function blockToSow () {
  return bot.findBlock({
    point: bot.entity.position,
    matching: bot.registry.blocksByName.farmland.id,
    maxDistance: 6,
    useExtraInfo: (block) => {
      const blockAbove = bot.blockAt(block.position.offset(0, 1, 0))
      return !blockAbove || blockAbove.type === 0
    }
  })
}

function blockToHarvest () {
  return bot.findBlock({
    point: bot.entity.position,
    maxDistance: 6,
    matching: (block) => {
      return block && block.type === bot.registry.blocksByName.wheat.id && block.metadata === 7
    }
  })
}

async function loop () {
  try {
    while (1) {
      const toHarvest = blockToHarvest()
      if (toHarvest) {
        await bot.dig(toHarvest)
      } else {
        break
      }
    }
    while (1) {
      const toSow = blockToSow()
      if (toSow) {
        await bot.equip(bot.registry.itemsByName.wheat_seeds.id, 'hand')
        await bot.placeBlock(toSow, new Vec3(0, 1, 0))
      } else {
        break
      }
    }
  } catch (e) {
    console.log(e)
  }

  // No block to harvest or sow. Postpone next loop a bit
  setTimeout(loop, 1000)
}

bot.once('login', loop)