cli-demo

Project for Demoing CLI Development using golang

Use Case

Hi, I am Ram, and I am devops professional employed by a pet store which deals with adoption of pets. Company has another employee named Shyam who works on store's front desk and deals with adopters. This employee is a volunteer who is not so tech-savvy and has requested an easy way to deal with day to day activities like getting pets, add new pets and so on and so forth.

Shyam asked Ram if he can give a very easy to use system to interact with backend database which is maintained by Pet Adoption community. So Ram decided to give Shyam a very easy to use cli program which he can use to get information he need easily and efficiently.

Agenda

In this branch Ram will initialize go project and get dependencies for creating CLI.

He has decided to use following tools:

• GoLang : Language which Ram will use to create CLI.
• Cobra : It's an opensource module which provides framework to create CLI's in golang.
• Viper : It's an opensource module which helps to manage configuration for any go program.
• osapi-codegen : Helps to create client/server code based on open api specification.
• go-pretty : helps in outputting text in cli application in go.

Steps

Step 1 : Go Module

Let's create go module and start with creating app directory which will host go code and then create module

mkdir cli-demo
cd myapp
go mod init github.com/ankurnema/cli-demo

Step 2: Download dependencies

Let's download go dependencies we will need to create our commands

go get -u github.com/spf13/cobra@latest
go get github.com/spf13/viper
go get github.com/jedib0t/go-pretty/v6

# For generating code using osapi-codegen we need to install this tool
go install github.com/deepmap/oapi-codegen/cmd/oapi-codegen@latest

# For using cobra CLI we need to install this tool
go install github.com/spf13/cobra-cli@latest

Step 3: Project Folder Structure

Lets create folder structure for organizing our code.

cli-demo/           # Root Directory
├── cmd/            # Directory which contains all command high level code
├── pkg/            # Contain packages which are public in nature
│   └── petstore/   # Package containing Pet Store client code and type code
└── internal/       # directory containing internal code.

Step 4: Pet Store Client

Since we want to create a wrapper around pet store using this cli tool, we will need a client for interacting with pet store api's. Let's create our client using oapi-codegen tool. For this to work we need open api specification of pet store. We also need to access pet store server.

Pet store Server: https://Pet Store.swagger.io/

API Key: special-key

Pet store open api spec: https://Pet Store.swagger.io/v2/swagger.json

Lets generate client using oapi-codegen

cd pkg/Pet Store
oapi-codegen -package Pet Store --generate types,client Pet Store.yaml > Pet Store.gen.go

Above command will generate Pet Store client in Pet Store package.

Step 5: Command initialization

Now lets move on and initialize our root command using cobra and viper framework. We have already downloaded cobra-cli lets use same and initialize our root command.

cobra-cli init --author "Ankur Nema ankurnema@gmail.com" --license apache --viper

Above command will create main.go under cli-demo directory and root.go under cli-demo/cmd directory. main.go will start executing command is our main package. root.go contains rootCmd and its description.

At this point you should be able to execute below command and see long description about command.

Step 6: Get Command

Let's create our first command which will be parent command to get Pets. So we will add get command and pet, store and user sub command.

# Add Get command
cobra-cli add get -p 'rootCmd'

# Add sub commands
cobra-cli add pet -p 'getCmd'
cobra-cli add store -p 'getCmd'
cobra-cli add user -p 'getCmd'

Above commands have created get.go, pet.go, store.go and user.go files under cmd directory.

Step 7: Pet Command Business Logic

Now lets implement business logic to get pets based on status. User will provide status and will get pets by status.

For these lets add a flag to command first called status and then implement business logic to get details.

Check out commit for changes done.