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    1.0.15 • Public • Published

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    Uniform, auditable and secure use case javascript library. Influenced by Clean Architecture and Trailblazer


    $ npm install buchu


    Check the complete examples here or for a complete solution using herbsJS here.


    const { entity, field } = require('gotu')
    const Item = entity('Item', {
      id: field(Number),
      description: field(String),
      isDone: field(Boolean),
      position: field(Number)
    const { Ok, Err, usecase, step, ifElse } = require('../../../src/buchu')
    const dependency = {
        ItemRepository: require('../repositories/ItemRepository').ItemRepository,
    const addOrUpdateItem = (injection) =>
        usecase('Add or Update an Item on a to-do List', {
            // Input/Request type validation 
            request: { listId: Number, item: Item },
            // Output/Response type
            response: { item: Item },
            // Authorization Audit  
            authorize: async (user) => user.isAdmin ? Ok() : Err(),
            // Dependency Injection control
            setup: (ctx) => ctx.di = Object.assign({}, dependency, injection),
            // Step audit and description
            'Check if the Item is valid': step((ctx) => {
                return item.validate() // Ok or Error
            'Check if the List exists': step(async (ctx) => {
                return Ok()
            // Conditional step
            'Add or Update the Item': ifElse({
                'If the Item exists': step(async (ctx) => {
                    return Ok(newItem)
                'Then: Add a new Item to the List': step(async (ctx) => {
                    return ctx.ret = await // Ok or Error
                'Else: Update Item on the List': step(async (ctx) => {
                    return ctx.ret = await // Ok or Error


    app.put('/items/:item', function (req, res) {
        const request = req.params
        const user = { name: 'John', id: '923b8b9a', isAdmin: true } // from session
        const uc = addOrUpdateItem()
        await uc.authorize(user)
        const ret = await


      type: 'use case',
      description: 'Add or Update an Item on a to-do List',
      request: { listId: Number, item: Item },
      response: String,
      steps: [
        { type: 'step', description: 'Check if the Item is valid', steps: null },
        { type: 'step', description: 'Check if the List exists', steps: null },
            type: 'if else',
            if: { type: 'step', description: 'If the Item exists', steps: null },
            then: { type: 'step', description: 'Then: Add a new Item to the List', steps: null },
            else: { type: 'step', description: 'Else: Update Item on the List', steps: null }


    It is possible to retrieve the audit trail of an use case after its execution


        type: 'use case',
        description: 'Add or Update an Item on a to-do List',
        transactionId: '9985fb70-f56d-466a-b466-e200d1d4848c',
        elapsedTime: 1981800n, // in nanosecods
        user: { name: 'John', id: '923b8b9a', isAdmin: true },
        authorized: true,
        return: {
            Ok: { item: { id: 100, name: 'Do not forget this', position: 9 } }
        steps: [
            { type: 'step', description: 'Check if the Item is valid', elapsedTime: 208201n , return: {} },
            { type: 'step', description: 'Check if the List exists', elapsedTime: 114300n , return: {}  },
                type: 'if else', 
                description: 'Add or Update the Item',
                returnIf: { Ok: true },
                returnThen: {}

    TIP: If you need to audit the exceptions thrown by the use case use process.env.HERBS_EXCEPTION = "audit". This will swallow the exceptions and return a Err on the step. Recommended for production environments.

    Request Validation

    A request can be validated against the field's type.

    const addOrUpdateItem = (injection) =>
        usecase('Add or Update an Item on a to-do List', {
            // Input/Request type validation 
            request: { listId: Number, item: Object },

    Request types

    A field in a request can be basic types from Javascript or entities created from gotu herbs lib:

    Number: double-precision 64-bit binary format IEEE 754 value

    String: a UTF‐16 character sequence

    Boolean: true or false

    Date: represents a single moment in time in a platform-independent format.

    Object: the Object class represents one of JavaScript's data types.

    Array: the Array class is a object that is used in the construction of arrays.

    Entity: entity object represents an gotu base entity.



    "Programs must be written for people to read, and only incidentally for machines to execute" - Harold Abelson, Structure and Interpretation of Computer Programs

    Understanding what a software is doing from a business perspective is a must in order to be able to change it quickly and in a sustainable way.

    Metadata for system intent

    It should be easy to retrieve a system's metadata for all its use cases and steps. This info could be used to leverage innovative interfaces (ex: dynamic admin pages, use case documentations, etc), helping narrow the gap between developers, testers and product managers.

    Auditable and Secure

    It should be easy to have enterprise grade features even for simple applications. Authorization and auditing, for instance, should be available out of the box. Not using should be opt-in.

    Use Case

    What is it?

    A Use Case reflects a single action exposed by the Domain to the end user. Ex: Reopen Ticket, Reply Message, Add User

    Internaly a Use Case control the interaction between Entities, Repositories (infrastructure) and other Domain components.

    It should:

    • Be modeled around business
    • Be reusable
    • Be testable / Have clear acceptance criteria
    • Help identify right architecture
    • Ubiquitous language

    "Use cases orchestrate the flow of data to and from the entities, and direct those entities to use their Critical Business Rules to achieve the goals of the use case." - Clean Architecture book

    Best pratices

    • Keep it simple by telling stories
    • Understand the big picture
    • Focus on value
    • Build the use case in steps


    • Implement business flows using Use Cases.

      Ex: Reply Message use case interacts with Message, Ticket, User and others entities in order to reply a message for a user

    • Split the flows in smaller steps

    • Avoid implement validations using Use Cases. Prefer Entities for validations

    • Access Use Cases from outside the Domain

      Use cases are the "entry points" for the Domain layer, so it is the only accessible layer from outside the Domain.

    • Don't access any other sublayer which belongs to Domain layer (Entities, etc) apart Use Case from outside Domain

    • Name the Use Case folder, file and its steps as an action (verb).

      Ex: OpenTicket.js, ReplyMessage.js, AddUser.js

      Use Cases are implemented as command patterns.


    • Clean Architecture book link
    • Use Case 2.0 link
    • Use Case diagram link
    • Service Layer link

    To Do

    • [X] Base - Run a use case
    • [X] Use Case Error - Ok or Error results for a use case (Rust inspired)
    • [X] Steps - Enable multiple steps for a use case
    • [X] Nested Steps - Enable multiple steps for a parent step
    • [ ] Nested Steps - multiple files - Enable multiple steps in diferent files for a parent step
    • [ ] Use usecase as a step
    • [X] Doc Step - Get description and structure from use case and its steps
    • [X] Request - Be able to describe and validate the use case request object
    • [X] Response - Be able to describe and validate the use case response object
    • [X] Dependency Injection (removed)
    • [X] ctx var - Share context between Steps
    • [X] Conditional Steps - Enable a If/Else constructor for steps
    • [X] Authorization - Be able to authorize the execution of a use case and its steps
    • [X] Audit - Be able to track use case runtime information
    • [X] Audit - Timing - Be able to track use case and its steps execution time
    • [ ] Async / MQ - Multiple Rounds - Be able to partially execute a use case and continue (when a MQ is necessary, for instance)
    • [X] transaction ID - A ID to track execution between steps
    • [ ] session ID - A ID to track execution between use cases
    • [X] Deal with exceptions
    • [ ] Deal with no default results (Ok/Err)
    • [X] Deal with async / await steps
    • [X] Use case examples
    • [ ] Doc - Documentation and samples for each feature


    Come with us to make an awesome Buchu.

    Now, if you do not have technical knowledge and also have intend to help us, do not feel shy, click here to open an issue and collaborate their ideas, the contribution may be a criticism or a compliment (why not?)

    If you would like to help contribute to this repository, please see CONTRIBUTING

    The Herb

    Buchu is most often used as a stimulating tonic and a diuretic. It is now commonly used to treat urinary tract infections. In the past, this herb has also been used to treat arthritis, kidney stones and gout. It can also be used externally for bruises and sprains.


    Buchu is released under the MIT license.


    npm i buchu

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