const fs = require('fs')
const os = require('os')
const md5 = require('md5')
const { promisify } = require('util')
const PythonWorker = require('./pythonWorker')

const readdir = promisify(fs.readdir)
const stat = promisify(fs.stat)

/**
 * INTERFACE BACKEND
 *
 * Communication with workers (for now only Python)
 * The workers are implemented as REPL clients that
 * communicate with JSON.
 *
 * Names:
 *  * Worker: a Python file that implements a REPL client (e.g. serial)
 *  * Port:
 *  * Connection:
 */

const WORKER_DIR = `${__dirname}/python_workers`
const HOST = os.hostname()

const state = {
  interfaces: [],
  ports: [],
  connections: [],
  lastScan: {
    workers: Date.now() - 100000,
    ports: Date.now() - 100000,
    connections: Date.now() - 100000,
  },
}

const typeDefs = `
  type Interface {
    id: ID!
    interfaceName: String!
    workerScript: WorkerScript!
    workerProcess: WorkerProcess
    ports: [Port]!
    connections: [Connection]!
    options: [Option!]
  }

  type WorkerScript {
    path: String!
    mtime: DateTime!
    updated: DateTime
  }

  type WorkerProcess {
    pid: Int!
    killed: Boolean!
    signalCode: String
    exitCode: Int
    spawnfile: String!
    spawnargs: [String]!
  }

  type Option {
    name: String!
    type: String!
    description: String
    values: [String!]
  }

  type Port {
    id: String!
    interfaceName: String!
    host: String!
    device: String
    name: String
    description: String
  }

  type Connection {
    id: ID!
    port: Port!
    workerProcess: WorkerProcess
  }

  input ConnectionCommand {
    type: String!
    data: String
    options: String
  }

  extend type Query {
    interfaces: [Interface]!
    interface(id: ID, interfaceName: String): Interface!
    ports(interfaceName: String, force: Boolean): [Port]!
    port(id: ID!): Port!
    connections: [Connection]!
    connection(id: ID!): Connection!
  }

  extend type Mutation {
    connect(portId: ID!): Connection!
    endConnection(connectionId: ID!): Connection!
    killConnection(connectionId: ID!): Connection!
    sendCommand(connectionId: ID!, command: ConnectionCommand!): String!
  }
`

/**
 * INTERFACE SECTION
 */
async function findInterfaces() {
  // 1. Don't check more frequently than once per second.
  // if (state.lastScan.workers + 1000 > Date.now()) return null
  // state.lastScan.workers = Date.now()

  // 2. Find all files in ./python_workers that end in _worker.py
  const fileNames = await readdir(WORKER_DIR)
  const workerFiles = fileNames.filter(fileName =>
    fileName.includes('_worker.py')
  )

  // 3. For every worker script
  const workerPromises = workerFiles.map(async workerFile => {
    const interfaceName = workerFile.replace(/_worker\.py/, '')
    const path = `${WORKER_DIR}/${workerFile}`
    // a. Find out if it was modified.
    const { mtime } = await stat(path)
    const workerScript = { path, mtime, updated: null }
    const foundInterface = state.interfaces.find(
      iface => iface.interfaceName === interfaceName
    )
    if (foundInterface) {
      // b. If it was modified, save the modification time.
      if (foundInterface.workerScript.mtime < mtime)
        foundInterface.workerScript.updated = mtime
      return
    }
    // c. Spawn a new worker connection.
    const workerProcess = new PythonWorker(workerScript)
    const { data, error } = await workerProcess.spawn()
    if (error) throw new Error(error)
    // d. Save the worker in the state.
    state.interfaces.push({
      id: md5(`${interfaceName}${workerScript}${mtime}`),
      interfaceName,
      workerScript,
      workerProcess,
      ports: [],
      connections: [],
      options: await options(workerProcess),
    })
  })
  await Promise.all(workerPromises)
}

async function interfaces(parent, args, context, info) {
  await findInterfaces()
  return state.interfaces.map(iface => ({
    ...iface,
    ports: ports(iface.interfaceName, args, context, info),
    // Serialize worker process
    workerProcess: workerProcess(iface.workerProcess, args, context, info),
  }))
}

async function interface(parent, args, context, info) {
  await findInterfaces()
  const { id, interfaceName } = args
  if (!id && !interfaceName) {
    throw new Error('Either id or interfaceName needs to be provided!')
  }
  const iface = state.interfaces.find(
    iface => iface.id === id || iface.interfaceName === interfaceName
  )
  if (!iface) {
    throw new Error(`Worker id=${id}, interfaceName=${interfaceName} not found`)
  }
  return {
    ...iface,
    workerProcess: workerProcess(iface.workerProcess, args, context, info),
  }
}

async function options(workerProcess) {
  const { data, error } = await workerProcess.send({
    type: 'options',
  })
  if (error) throw new Error(error)
  return data
}

function workerProcess(parent, args, ctx, info) {
  const {
    killed,
    exitCode,
    signalCode,
    spawnargs,
    spawnfile,
    pid,
  } = parent.pythonShell
  return {
    pid,
    killed,
    exitCode,
    signalCode,
    spawnfile,
    spawnargs,
  }
}

/**
 * PORTS SECTION
 */
async function findPorts() {
  // 1. Make sure, workers are updated.
  await findInterfaces()

  // 2. Don't check more frequently than once per second.
  // if (state.lastScan.ports + 1000 > Date.now()) return null
  // state.lastScan.ports = Date.now()

  // 3. Loop through all workers to find available ports.
  const portsPromises = state.interfaces.map(async iface => {
    // a) Ask interface for ports.
    const { data, error, pythonError } = await iface.workerProcess.send({
      type: 'ports',
    })
    if (error) throw new Error(error)
    // b) Add all ports that are not in the list.
    data.forEach(port => {
      const id = port.name || port.device
      if (state.ports.find(port => port.id === id)) return null
      const newPort = {
        id,
        interfaceName: iface.interfaceName,
        host: HOST,
        ...port,
      }
      state.ports.push(newPort)
      iface.ports.push(newPort)
    })
  })
  await Promise.all(portsPromises)
}

async function ports(parent, args, ctx, info) {
  await findPorts()
  const { interfaceName } = args
  const ifName = interfaceName || parent

  if (ifName) {
    const iface = state.interfaces.find(iface => iface.interfaceName === ifName)
    if (!iface) throw new Error(`Interface ${ifName} not found.`)
    return iface.ports
  } else {
    return state.ports
  }
}

async function port(parent, args, ctx, info) {
  await findPorts()
  const { id } = args
  if (!id) throw new Error('Need an id.')
  const port = state.ports.find(port => port.id === id)
  return port
}

/**
 * CONNECTION SECTION
 */
async function connect(parent, args, ctx, info) {
  await findPorts()
  const { portId } = args
  const port = state.ports.find(port => port.id === portId)
  if (!port) throw new Error(`Port ${portId} not found`)
  const iface = state.interfaces.find(
    iface => iface.interfaceName === port.interfaceName
  )
  const id = md5(iface.interfaceName + iface.device)
  if (iface.connections.find(connection => connection.id === id)) {
    throw new Error('already connected.')
  }
  const pythonWorker = new PythonWorker(iface.workerScript)
  const spawnData = await pythonWorker.spawn()
  if (spawnData.error) throw new Error(spawnData.error)
  const connection = {
    id,
    port,
    workerProcess: pythonWorker,
  }
  const connectionData = await connection.workerProcess.send({
    type: 'connect',
    device: port.device,
  })
  if (connectionData.error) throw new Error(connectionData.error)
  iface.connections.push(connection)
  state.connections.push(connection)
  return {
    ...connection,
    workerProcess: workerProcess(pythonWorker),
  }
}

async function connections(parent, args, ctx, info) {
  if (parent) {
    const iface = state.interfaces.find(iface => iface.interfaceName === parent)
    return iface.connections.map(connection => {
      return {
        ...connection,
        workerProcess: workerProcess(connection.workerProcess),
      }
    })
  } else {
    return state.connections.map(connection => {
      return {
        ...connection,
        workerProcess: workerProcess(connection.workerProcess),
      }
    })
  }
}

async function connection(parent, args, context, info) {
  const connection = state.connections.find(
    connection => connection.id === args.id
  )
  return {
    ...connection,
    workerProcess: workerProcess(connection.workerProcess),
  }
}

async function sendCommand(parent, args, ctx, info) {
  const { connectionId, command } = args
  const connection = state.connections.find(
    connection => connection.id === connectionId
  )
  const { data, error } = await connection.workerProcess.send({ ...command })
  if (error) throw new Error(JSON.stringify(error))
  return data.response
}

// TODO Also find connections in interfaces.
async function endConnection(parent, args, ctx, info) {
  const { connectionId } = args
  const connectionIndex = state.connections.findIndex(
    connection => connection.id === connectionId
  )
  const connection = state.connections[connectionIndex]
  const iface = state.interfaces.find(
    iface => (iface.interfaceName = connection.interfaceName)
  )
  const { data, error } = await connection.workerProcess.end()
  if (error) throw new Error(JSON.stringify(error))
  state.connections.splice(connectionIndex, 1)
  return connection
}

async function killConnection(parent, args, ctx, info) {
  const { connectionId } = args
  const connectionIndex = state.connections.findIndex(
    connection => connection.id === connectionId
  )
  const connection = state.connections[connectionIndex]
  const { data, error } = await connection.workerProcess.kill()
  if (error) throw new Error(JSON.stringify(error))
  state.connections.splice(connectionIndex, 1)
  return connection
}

const resolvers = {
  Query: {
    interfaces,
    interface,
    ports,
    port,
    connections,
    connection,
  },
  Mutation: {
    connect,
    sendCommand,
    endConnection,
    killConnection,
  },
}

module.exports = { typeDefs, resolvers }