Fluid-chains

A simple way to organize asynchronous Javascript functions that looks like this:

And turn it into something like this: (ES6)

Table of Contents

• Getting Started
• Installation
• Creating your first chain
• Starting the chain
• Creating chain sequence
• Reusing Chains
• Error handling
• Using decorator
• Adding specifications and validation
• Strict mode
• Caching
• Middlewares
• How it works
• Examples
• Documentation
  • Chain
  • ChainSpec
  • ChainMiddleware
  • ExecuteChain
  • ChainExists
  • ChainList
• Authors
• License

Getting Started

Installing fluid-chains is easy. We want to make it light and simple.

Installation

npm install --save fluid-chains

• Javascript (ES6)

import {Chain} from 'fluid-chains';

• Javascript

var FluidChains = require('fluid-chains');
var Chain  = FluidChains.Chain;

Creating your first chain

new Chain('FindPeople', function(context, param, next) {
    var people = ['john','jane','sam'];
    context.set('people', people.filter(
      function(person) { 
         person === param.filterBy() 
        }));
      next();
});

Starting the chain

• ES6

import {ExecuteChain} from 'fluid-chains';

• Javascript

var FluidChains = require('fluid-chains');
var ExecuteChain = FluidChains.ExecuteChain;

ExecuteChain('FindPeople', {filterBy: 'jane'}, 
    function(result) {
       var people = result.people();;
     console.log('people', people);
});

Creating chain sequence

new Chain('firstChain', function(context, param, next) {
    /* 
        context.set(key, value) will set 
        param value of the next chain. 
    */ 
    if (param.name) {
        context.set('remarksTo', param.name());
    } else {
        context.set('remarksTo','everyone');
    }

    next(); 
    /* call to proceed to the next chain. 
    Good for asynchronous callbacks */

}, 'secondChain' /* name of the next chain */); 

new Chain('secondChain', function(context, param, next) { 

    /* 
        the context value of the previous chain can
        be accessed with param.{field}() and it's always
        a Function.
    */
    
    context.set('remarks','Hello, '+param.remarksTo()+'!');

    next(); 
    /* not calling next() will break the chain 
    and will not trigger the callback below.*/
});

ExecuteChain('firstChain', function(result) {
    /* 
        This will run because you call next()
        from the last chain.
    */
    console.log(result.remarks());
});

Note: You cannot put Function as a value in context.set(key, value). You can put value and object.

Reusing Chains

ExecuteChains(Array, Parameter, Done);

new Chain('first', function(context,param, next){
   // param.host() can be accessed here
   next()},'second');
new Chain('second', function(context,param,next) {
   next()},'third');
new Chain('third', function(context,param,next {
   // param.host() can be accessed here
   next()},'fourth');
new Chain('fourth', function(context,param,next) {
   next()});

ExecuteChain(['first','third'],{host: 'http://localhost'}, function(result) {
    // last chain processed was "third"
});

Note: Executing chains like the sample above will ignore the chain's predefined sequence and it will follow the chain sequence in the array. The sample above will run the "first" chain then "third" as long as you satify their parameter and it will complete the sequence even if there is a sequence defined in the "third" chain (which is the "fourth") thus make the chains reuseable.

Additional note: Parameters can be used throughout the chains.

Error handling

You can also use a chain as an error handler. Basically you're just creating another chain.

new Chain('firstChain', function(context, param, next) {

    /* 
        context.set(key, value) will set param value of the 
        next chain. 
    */ 

    if (param.name) {
        context.set('remarksTo', param.name());
    } else {
      throw new Error('Name is required.');
    }
    next();

}, 'secondChain', 'firstErrorHandler' 
  /*error handler is on the fourth argument*/); 

new Chain('firstErrorHandler', function(context, param, next) { 
    /*
        param.$error and param.$errorMessage functions
        are created.
    */
    console.log('error', param.$error());  
        // Error('Name is required.');
    console.log('errorMessage', param.$errorMessage()); 
        // 'Name is required.'
    next(); 
    /* 
        You can call next() to finish the chain or 
        just ignore it and break the chain. 
        You can even start a new chain of actions. 
    */
});

Note: You can place an error handler for each chain otherwise it will be thrown to the nearest error handler of its previous chain.

new Chain('firstChain', function(context, param, next) {
    if (param.name){
        context.set('remarksTo', param.name());
    } else {
        context.set('remarksTo','everyone');
    }
    next();

}, 'secondChain', 'firstErrorHandler'); 

new Chain('secondChain', function(context, param, next) {
    context.set('remarks','Hello, '+param.remarksTo()+'!');
    next();

}, 'thirdChain', 'anotherErrorHandler'); 

new Chain('thirdChain', function(context, param, next) {
   if (param.name){
        context.set('remarksTo', param.name());
    } else {
      throw new Error('Name is required.');
    }
    next();
}); 

new Chain('firstErrorHandler', function(context, param, next) { 
    console.log('error', param.$error());  
        // Error('Name is required.');
    console.log('errorMessage', param.$errorMessage()); 
        // 'Name is required.'
    next();
});

new Chain('anotherErrorHandler', function(context, param, next) { 
    //thirdChain error will also be handled here.
    next();
});

Note: For asynchronous callback errors you may do "next(Error)".

new Chain('firstChain', function(context, param, next) {
    setTimeout(function() {
        next(new Error('sample'));
    });
}, 'secondChain', 'firstErrorHandler'); 

Using decorator

You can create a chain by using decorator @ChainAction.

import {ChainAction, ExecuteChain} from 'fluid-chains';

class Student {

    @ChainAction
    createStudent(context, param, next) {
        //param.name();
        //context.set('studentId',####);
    }

    @ChainAction
    findAll(context, param, next) {

    }

}

const student = new Student();

ExecuteChain(student.CHAIN_CREATESTUDENT, {
        name:'John Doe'
    }, result =>{
        //result.studentId
    })
// student.CHAIN_FINDALL
// student.CHAIN_CREATESTUDENT

ChainAction can only be used in a function inside a class. It will initialize a chain based on the function name and will set a string constant CHAIN_{Name of the function in upper case} in the current class.

Adding specifications and validation

For each chain we can specify required fields and custom validations

var FindPeopleChain = new Chain('FindPeople', function(context, param, next) { 
    param.name() // should not be null or empty
    param.type() // should not be null or empty and must be "quick"
    next();
});

/*
    @param field: string,
    @param required: boolean
    @param customerValidation (Optional) : Function(callback) => callback(valid, message)
*/
FindPeopleChain.addSpec('name', true);
FindPeopleChain.addSpec('type',true, function(done) {
    done(type ==='quick', 'Type should be "quick"'); });

// or

FindPeopleChain.addSpec('email').require('custom message').validator((currentValue, valid)=>{
    valid(currentValue.match('email regex here'));
});

Strict mode

You can turn on strict mode by invoking "ChainStrictModeEnabled" function.

• ES6

import {ChainStrictModeEnabled} from 'fluid-chains';
ChainStrictModeEnabled();

• Javascript

var FluidChains = require('fluid-chains');
var ChainStrictModeEnabled = FluidChains.ChainStrictModeEnabled;
ChainStrictModeEnabled();

With strict mode "on", chains can will only accept parameter that is specified in addSpec.

 new Chain('StrictModeChain01', function(context, param, next) {
    context.set('name', 'John');
    context.set('surname', 'Wick');
    context.set('age', 'unknown');
    next();
 }, 'StrictModeChain02');


var strictChain = new Chain('StrictModeChain02', function(context, param, next) {
    param.name() // is available
    param.surname() // is available
    param.age() // is not available 
    next();
}, null, null);

strictChain.addSpec('name', true);
strictChain.addSpec('surname', true)

Caching

Since the chain output can be based on the value of its parameter making it possible to cache the output of a chain.

To enable caching you must have strict mode enabled.

• ES6

import {ChainStrictModeEnabled, ChainCacheEnabled} from 'fluid-chains';
ChainStrictModeEnabled();
ChainCacheEnabled();

• Javascript

var FluidChains = require('fluid-chains');
var ChainStrictModeEnabled = FluidChains.ChainStrictModeEnabled;
var ChainCacheEnabled = FluidChains.ChainCacheEnabled;
ChainStrictModeEnabled();
ChainCacheEnabled();

Note: Only the fields specified in Chain.addSpec() will be used as identifier of the chain cache. If Chain.addSpec() are not used it will cache the chain using its name.

Running with Middlewares

• ES6

import { ChainMiddleware } from 'fluid-chains';

• Javascript

var FluidChains = require('fluid-chains');
var ChainMiddleware = FluidChains.ChainMiddleware;

/*
* Will only get here before chain 'FindPeople' is executed
*/
new ChainMiddleware('FindPeople', function(param, context, next) { 
    next();
});

/*
* Will only get here before chain name that starts with "Find" is executed
*/
new ChainMiddleware(\^Find\g, function(param, context, next) { 
    if(context.$next() === 'CreatePeopleChain' && param.sessionKey){
        //validates 
    } else {
        throw new Error('Chain authentication failed.');
    }
    next();
});

/*
* Will run before every chains
*/
new ChainMiddleware(function(param, context, next) {
   console.log('param',param.$owner());
   next();
});

How it works

Examples

• Examples

Documentation

Chain

The star of this package.

    var chainSample = new Chain('ChainSample', function(context, param) {
        // do something
    })

constructor(name:String, action:Function, next:String, errorHandler:String)

• name: defines the name of the chain
• action: function(context:ChainContext, param: ChainContext, [next:Function])
  • context: context of the current chain
  • param: consist of root parameters and context or the previous chain
  • next (optional): triggers the callback of the chain
• next: defines the next chain in sequence
• errorHandler: defines the name of the error handler chain

Note: chain will run synchronously if next is not defined in action parameters

field | description | usage -------------|--------------------------------------------|-------- addSpec() | sets the chain parameter spec | chain.addSpec(ChainSpec) info() | returns the name, status & response time | chain.info() status() | returns thes current status of chain | chain.status() terminate() | stops the running chain | chain.terminate() execute() | executes the chain | chain.execute(callback, ChainContext, NextChain, disableNext)

ChainSpec

Defines the input of the chain.

   var chainSample = new Chain('ChainSample', function(context, param) {
    param.name() // this is required for this chain
    param.email() // this is required for this email and validated before going here
   });
   
   chainSample.addSpec('name', true);
   chainSample.addSpec('user')
            .transform(function(currentValue, newForm){
                if(currentValue){
                    findUser(currentValue, function(userData) {
                        newForm(userData);
                    });
                }
            });
   chainSample.addSpec('email')
            .require()
            .validator(function(currentValue, valid) {
                valid(currentValue.match(/email-regex/g));
            });
   chainSample.addSpec('fullname')
            .translate(function(currentValue, context) {
                const names = currentValue.split(',');
                context.set('lastname', names[0]);
                context.set('firstname', names[1]);
            });       
   

field | description | usage -------------|---------------------------------------------|-------- require() | mark the field as a required input in chain | chain.addSpec(field:String).require(customMessage:String) default() | defines the default value | chain.addSpec(field:String).default(value:String) validator() | defines the validator | chain.addSpec(field:String).validator(validate:Function) transform() | defines the transformer | chain.addSpec(field:String).transform(transformer:Function) translate() | defines the translator | chain.addSpec(field:String).translate(translator:Function)

ChainMiddleware

constructor(target:String, action:Function(param:ChainContext, context:ChainContext, next:Function(err:Error)));

new ChainMiddleware('{targetChainName}', function(param, context, next) {
    next();
   });

• target: defines the name of the target chain
• action: function(param:ChainContext, context: ChainContext, [next:Function])
  • param: consist of root parameters and context of the previous chain
  • context: context of the target chain
  • next (optional): triggers the callback of the chain

ExecuteChain

Executes and composes sequence of chains.

• function([name:String|Array], parameters, callback);

    
    ExecuteChain('ChainSample', {
        hello: 'hello'
     }, function(result) {
     
     });
     
      ExecuteChain(['ChainSample','ChainSample_2'], {
        hello: 'hello'
     }, function(result) {
     
     });
     

ChainExists

Availability checker of chain in the current instance.

ChainExists = function(name:String):Boolean

ChainList

Returns an array of all the available chains in the current instance

Authors

• Jerico de Guzman - LinkedIn

See also the list of contributors who participated in this project.

License

This project is licensed under the MIT License - see the LICENSE.md file for details