// Tools for managing system services with systemctl (and eventually other options)
import { execSync } from 'child_process'
import path from 'path'
import fs from 'fs'
import { aoEnv, setAoEnv } from './settings.js'
import { isFile } from './files.js'
import { askQuestionText } from './welcome.js'

const SERVICE_FOLDER_PATH = '/etc/systemd/system'

// Manages a single systemctl service. serviceName is required. Implements the same functions as an AO feature module.
// serviceFileText is optional but if omitted, install(), uninstall(), and isInstalledToSpec() will not exist
// The only thing in this world that needs to be 'managed' is systemctl
export default class SystemServiceManager {
  constructor(serviceName, serviceFileText = false) {
    this.name = serviceName + '.service'
    this.serviceFileText = serviceFileText
    this.assertInitialized()
    if(this.serviceFileText && this.serviceFileText.length >= 1) {
      this.install = this.willBeInstall
      this.uninstall = this.willBeUninstall
      this.isInstalledToSpec = this.willBeIsInstalledToSpec
    }
  }
  
  // Throws an exception if the service name has not been set
  assertInitialized() {
    if(!this.name || this.name.length < ('.service'.length + 1)) {
      throw new Error('SystemServiceManager: Service name must be a string at least one character long.')
    }
  }
  
  // Throws an exception if the serviceFileText has not been set
  assertServiceFileText() {
    if(!this.serviceFileText || this.serviceFileText.length < 1) {
      return false
      //throw new Error('SystemServiceManager: Attempt to use a function that requires serviceFileText, but serviceFileText is blank.')
    }
    return true
  }
  
  // Returns the full path of the service file, based on the service name
  servicePath() {
    this.assertInitialized()
    return path.join(SERVICE_FOLDER_PATH, this.name)
  }
  
  status(verbose = true) {
    if(this.isInstalled(verbose)) {
      if(this.isRunning(verbose)) {
        return 'running'
      }
      return 'installed'
    }
    console.log('its off')
    return 'off'
  }
  
  // Returns true if the service file exists (does not check if it matches serviceFileText)
  isInstalled(verbose = true) {
    this.assertInitialized()
    let error
    try {
      const stdout = execSync('systemctl cat -- ' + this.name + ' 2>&1')
      if(stdout.length >= 1) {
        return true
      }
    } catch(error) {
      if(error.output.toString().includes('No files found for')) {
        return false
      }
    }
    if(verbose) console.log('Unknown status, assuming not installed' + (error ? error.output.toString() : '.'))
    return false
  }
  
  // Return true if the file at the service file path matches the serviceFileText
  // This function and isInstalled use different methods of getting this text but it should be identical, if not we will notice someday
  willBeIsInstalledToSpec(verbose = true) {
    console.log('isInstalled()')
    this.assertInitialized()
    this.assertServiceFileText()
    const serviceFileText = fs.readFileSync(this.servicePath())
    if(serviceFileText === this.serviceFileText) {
      return true
    } else {
      if(verbose) console.log('Failed to write service file, sorry.')
      return false
    }
  }
  
  // Creates or overwrites the service file
  willBeInstall(force = false, verbose = true) {
    console.log('Creating service file. You may be asked for you sudo password.')
    this.assertInitialized()
    this.assertServiceFileText()
    try {
      const tempPath = path.join(process.env.HOME, '.ao/generatedservice.temp')
      fs.writeFileSync(tempPath, this.serviceFileText, force ? { flag: "wx" } : undefined)
      execSync('sudo mv ' + tempPath + ' ' + this.servicePath())
      execSync('sudo systemctl daemon-reload')
      return true
    } catch(error) {
        if(verbose) console.log('Service file already exists, or other error:', error)
    }
    // Clean up the temp file
    try {
      if(isFile(tempPath)) execSync('sudo rm ' + tempPath + ' 2>&1')
    } catch(error) {} // If it failed, the temp file probably didn't exist
    return false
  }
  
  // Deletes the service file
  willBeUninstall(verbose = true) {
    this.assertInitialized()
    console.log('Deleting service file. You may be asked for you sudo password.')
    try {
      execSync('sudo rm ' + this.servicePath())
      if(verbose) console.log("Deleted service file.")
      execSync('sudo systemctl daemon-reload')
      return true
    } catch(error) {
      if(verbose) console.log('Failed to delete service file:', error)
    }
    return false
  }
  
  // Returns true if the service is currently running without errors
  isRunning(verbose = true) {
    this.assertInitialized()
    try {
      const stdout = execSync('systemctl status -- ' + this.name)
      if(stdout.includes('active (running)')) {
        return true
      }
    } catch(error) {
      error = error.output.toString()
      if(error.includes(' could not be found.')) {
        if(verbose) console.log('Warning: Checking whether a nonexistent service ' + this.name, 'is running. Check whether it is installed first.')
        return false
      } else if(error.includes('inactive (dead)')) {
        return false
      } else if(error.includes('failed')) {
        return false
      } else if(error.includes('stopped')) {
        return false
      } else {
        if(verbose) console.log('Unknown error checking ' + this.name + ' running status:', error)
      }
    }
    return false
  }
  
  // Attempts to start the service. Asks for sudo.
  start(verbose = true) {
    this.assertInitialized()
    try {
      const stdout = execSync('sudo systemctl start -- ' + this.name)
      // todo: check for errors including wrong sudo password here
      return true
    } catch(error) {
      if(verbose) console.log('Error starting service:', error)
    }
    return false
  }
  
  // Attempts to stop the service. Asks for sudo.
  stop(verbose = true) {
    this.assertInitialized()
    try {
      const stdout = execSync('sudo systemctl stop -- ' + this.name)
      // todo: check for errors including wrong sudo password here
      return true
    } catch(error) {
      if(verbose) console.log('Error stopping service:', error)
    }
  }
}

// Returns the saved list of custom services the user has saved in ao-cli's feature management interface
export function getCustomServicesList() {
  let servicesList = aoEnv('AO_CLI_CUSTOM_SERVICES')
  if(!servicesList) {
    return []
  }
  return servicesList.split(',')
}

// Adds the given service name to the custom list of services saved for ao-cli in .env, and returns a new SystemServiceManager to control it
// Adding custom services is only for starting and stopping them, not for adding a service file (could add this but would need to make a UI)
function addCustomService(serviceName) {
  const customServices = getCustomServicesList()
  customServices.push(serviceName)
  const serialized = customServices.join(',')
  setAoEnv('AO_CLI_CUSTOM_SERVICES', serialized)
  return new SystemServiceManager(serviceName)
}

export function removeCustomService(serviceName) {
  let customServices = getCustomServicesList()
  customServices = customServices.filter(service => service !== serviceName)
  const serialized = customServices.join(',')
  setAoEnv('AO_CLI_CUSTOM_SERVICES', serialized)
}

// Asks the user for a new service name and save it
export async function addCustomServiceInteractive() {
  let serviceName = await askQuestionText('What is the name of the service?')
  if(!serviceName || serviceName.length < 1) {
    console.log('Nothing entered, going back.')
    return false
  }
  serviceName = serviceName.toLowerCase()
  if(getCustomServicesList().includes(serviceName)) {
    console.log('You have already add that service to the list.')
    return true
  }
  const service = new SystemServiceManager(serviceName)
  if(!service.isInstalled()) {
    console.log('That service does not exist, sorry.')
    return true
  }
  addCustomService(serviceName)
  return false
}