Step by Step Guide to Building a Google Contacts API Integration in Go

Introduction

Hey there, fellow Go enthusiasts! Ready to dive into the world of Google Contacts API integration? You're in for a treat. We'll be using the nifty go-google-contacts package to make our lives easier. Buckle up, and let's get coding!

Prerequisites

Before we jump in, make sure you've got these bases covered:

• Go installed on your machine (I know, obvious, right?)
• A Google Cloud Console project set up (if you haven't done this before, it's a breeze)
• OAuth 2.0 credentials (we'll need these for authentication)

Setting up the project

Let's kick things off by setting up our project:

mkdir google-contacts-integration
cd google-contacts-integration
go mod init github.com/yourusername/google-contacts-integration
go get github.com/emersion/go-google-contacts

Authentication

Now for the fun part - authentication! We'll implement the OAuth 2.0 flow:

import (
    "golang.org/x/oauth2"
    "golang.org/x/oauth2/google"
)

config := &oauth2.Config{
    ClientID:     "YOUR_CLIENT_ID",
    ClientSecret: "YOUR_CLIENT_SECRET",
    Endpoint:     google.Endpoint,
    Scopes:       []string{"https://www.googleapis.com/auth/contacts"},
}

// Implement the OAuth flow here
// ...

token, err := config.Exchange(context.Background(), authorizationCode)
if err != nil {
    log.Fatal(err)
}

Creating a client

With our token in hand, let's create a client:

import "github.com/emersion/go-google-contacts"

client := contacts.NewClient(oauth2.NewClient(context.Background(), oauth2.StaticTokenSource(token)))

Basic operations

Now we're cooking! Let's run through some basic operations:

Fetching contacts

contacts, err := client.ListContacts()
if err != nil {
    log.Fatal(err)
}
for _, contact := range contacts {
    fmt.Printf("Name: %s, Email: %s\n", contact.Name, contact.Email)
}

Creating a new contact

newContact := &contacts.Contact{
    Name:  "John Doe",
    Email: "[email protected]",
}
createdContact, err := client.CreateContact(newContact)
if err != nil {
    log.Fatal(err)
}

Updating an existing contact

contact.Name = "Jane Doe"
updatedContact, err := client.UpdateContact(contact)
if err != nil {
    log.Fatal(err)
}

Deleting a contact

err := client.DeleteContact(contact.ID)
if err != nil {
    log.Fatal(err)
}

Advanced features

Want to take it up a notch? Let's look at some advanced features:

Pagination

pageToken := ""
for {
    contacts, nextPageToken, err := client.ListContactsWithToken(pageToken)
    if err != nil {
        log.Fatal(err)
    }
    // Process contacts
    if nextPageToken == "" {
        break
    }
    pageToken = nextPageToken
}

Filtering contacts

query := "example.com"
contacts, err := client.SearchContacts(query)
if err != nil {
    log.Fatal(err)
}

Error handling

Always be prepared for errors:

if err != nil {
    switch e := err.(type) {
    case *contacts.Error:
        fmt.Printf("Google Contacts API error: %v\n", e)
    default:
        fmt.Printf("Unknown error: %v\n", e)
    }
}

Best practices

To keep your integration smooth and efficient:

• Implement rate limiting to avoid hitting API quotas
• Cache frequently accessed data to reduce API calls

Testing

Don't forget to test your code! Here's a quick example:

func TestCreateContact(t *testing.T) {
    // Mock the client
    // ...

    newContact := &contacts.Contact{
        Name:  "Test User",
        Email: "[email protected]",
    }
    createdContact, err := client.CreateContact(newContact)
    
    assert.NoError(t, err)
    assert.Equal(t, newContact.Name, createdContact.Name)
    assert.Equal(t, newContact.Email, createdContact.Email)
}

Conclusion

And there you have it! You've just built a Google Contacts API integration in Go. Pretty cool, right? Remember, this is just the tip of the iceberg. There's so much more you can do with this API, so don't be afraid to explore and experiment.

For more in-depth information, check out the go-google-contacts documentation and the Google Contacts API reference.

Now go forth and build amazing things with your newfound Google Contacts powers!