# Develop Plugin

Let's try to create a log plugin as tutorial.

# Initialize Plugin

Create plugin for your repo

create a folder under <rootDir>/plugins:

# ensure <rootDir>/plugins exist
mkdir plugins

# create folder for your plugin
mkdir plugins/log-plugin

# create plugin entry
touch plugins/log-plugin/index.ts

# create plugin type
touch plugins/log-plugin/type.ts

Note that, type.ts will be used in .bootrc.ts if your plugin provides specific configuration.

# Write Plugin Function

type.ts is used to define the specific configuration required in your plugin.

Open plugins/log-plugin/type.ts, with below code boilerplate:

import { HttpRequest } from 'express-api-bootstrap'

export interface IPluginType {
  /**
   * Log configuration.
   *
   * This plugin is enable by default
   */
  log?: ILogConfig | false
}

interface ILogConfig {
  /**
   * Log formatter
   */
  logFormatter: (req: HttpRequest) => string
}

Open plugins/log-plugin/index.ts, with below code boilerplate:

import { Express, PluginOrderEnum, IPluginFactory, HttpRequest, HttpResponse } from 'express-api-bootstrap'
import { IPluginType } from './type'

export default <IPluginFactory>(opts => {
  return {
    // define what lifecycle you want your plugin to be executed
    order: PluginOrderEnum.BEFORE_API_INIT,
    // this func is important, by which the user can use this plugin without any config
    configHandler(config: IPluginType) {
      const opts = {
        logFormatter: (req: HttpRequest) => {
          return `INFO: ${req.ip} => ${req.path} => query:${JSON.stringify(req.query)} => body:${JSON.stringify(
            req.body
          )}`
        }
      }

      if (config.log === undefined || config.log === null) {
        return {
          log: opts
        }
      }
      
      if (config.log === false) {
        return {
          log: false
        }
      }

      if (config.log.logFormatter) {
        opts.logFormatter = config.log.logFormatter
      }

      return {
        log: opts
      }
    },
    // this func is the core part of your plugin
    pluginHandler(app: Express, config: IPluginType) {
      app.use((req: HttpRequest, res: HttpResponse, next: Function) => {
        if (config.log === false) {
          return next()
        }

        // i choose console here, you can use any log system you prefered
        console.log(config.log.logFormatter(req))
        next()
      })
    }
  }
})

Add this plugin in your .bootrc.ts, as below:

import { IBootConfig } from 'express-api-bootstrap/types'

export default <IBootConfig>{
  plugins: [
     { name: 'log-plugin' }
  ]
}

And at last, if you want to use this plugin with configuration intelliSense, you need to:

# re-generate express-api-bootstrap/types
npx boot init

express-api-bootstrap will scan plugins defined in .bootrc.ts from node_modules/ and <rootDir>/Plugins/, and re-generate proper ts type for you

After that, you are going to get intelliSense like:

← Plugin