Idealista to Messenger

Idealista2Messenger (I2M) is an app that provides the ability to forward notification emails from idealista.com to Meta's Messenger accounts.

Business Driver

As an idealista.com user I want to share its offer notifications with group of people via different channel than email.

How the application works

1. I2M authorizes to Google API with the OAuth 2.0 credentials.
2. Using Gmail API I2M fetches emails specified by the custom query.
3. Using Facebook's Open Graph API the I2M tells the Meta application to send a message on behalf of the FB Page to its user

Before you start

You will need:

1. Google Cloud project.
2. Google account with Gmail enabled.
3. Facebook Page.
4. Meta App.

Configuration

Google

Create Project

1. Create the Google Project

Enable the Gmail API

1. In the Google Cloud console, enable the Gmail API.

Add required privileges for the project

1. In the OAuth screen project's section you need to add privileges to Gmail API with .../auth/gmail.modify scope.

Obtain the credentials.json file

1. In the Google Cloud console, go to Menu > APIs & Services > Credentials.
2. Click Create Credentials > OAuth client ID.
3. Click Application type > Desktop app.
4. In the Name field, type a name for the credential. This name is only shown in the Google Cloud console.
5. Click Create. The OAuth client created screen appears, showing your new Client ID and Client secret.
6. Click OK. The newly created credential appears under OAuth 2.0 Client IDs.
7. Save the downloaded JSON file as credentials.json, and move the file to config directory.

Obtain the token.json file

1. The first time you run the I2M, it prompts you to authorize access:
   • If you're not already signed in to your Google Account, you're prompted to sign in. If you're signed in to multiple accounts, select one account to use for authorization.
   • Click Accept.
   • Copy the code from the browser, paste it into the command-line prompt, and press Enter.
2. token.json file will be created in config directory.
3. Authorization information is stored in the file system, so the next time you run the I2M, you aren't prompted for authorization.

Meta

1. Create Facebook Page
2. Create Meta App
   • App might be in dev mode, you will just need to invite users to participate f.e. as a testers
   • If you invite someone, their not getting any notification, invitations might be accepted here
3. Get a Page Access Token

Obtain Long Lived Paged Access Token

Long-lived Page Access Token procedure:

1. Get User Access Token:
   • App: {your meta app}
   • User or Page token: User token
   • Permissions: pages_show_list, pages_messaging, pages_read_engagement
   • Tool: https://developers.facebook.com/tools/explorer/
2. Go with token to Access Token Debugger:
   • Debug token
   • Click “Extend Access Token”
   • Tool: https://developers.facebook.com/tools/debug/accesstoken/
3. With long-lived User Access Token get long-lived Page Access Token:
   • Graph API version: v15.0
   • App Scoped User ID: {your app scoped user id}
   • CURL: curl -i -X GET "https://graph.facebook.com/{graph-api-version}/{app-scoped-user-id}/accounts?access_token={long-lived-user-access-token}"
   • Docs: https://developers.facebook.com/docs/facebook-login/guides/access-tokens/get-long-lived/#long-lived-page-token
4. Long-lived Page Access Token save in config/page_access_token.json file.

Obtain Facebook Page Scoped User IDs for sending messages

1. CURL: curl -i -X GET "https://graph.facebook.com/{latest-api-version}/{page-id}/conversations?fields=participants&access_token={page-access-token}"
2. Docs: https://developers.facebook.com/docs/messenger-platform/get-started

Putting all together in the .env file

1. FB_PAGE_ID - Facebook Page ID
2. FB_PAGE_RECIPIENTS - Comma separated recipients lists (no whitespace allowed)

Run the I2M application

If everything is set up correctly, you should be able run application and see similar output:

go run main.go
Idealista2Messenger 2022.12.10 17:44:37
Main process
Sending 1 message(s) to [<PAGE_SCOPED_USER_ID> <PAGE_SCOPED_USER_ID>]
Message <MESSAGE_ID> to <PAGE_SCOPED_USER_ID> sent
Message <MESSAGE_ID> to <PAGE_SCOPED_USER_ID> sent
Application "Idealista 2 Messenger" has finished processing

Troubleshooting

Gmail token expired or revoked

If your Gmail token is expired or revoked and you can see similar output:

Main process
Unable to retrieve messages: Get "https://gmail.googleapis.com/gmail/v1/users/me/messages?alt=json&prettyPrint=false&q=is%3Aunread+from%3Aidealista.com": oauth2: cannot fetch token: 400 Bad Request
Response: {
  "error": "invalid_grant",
  "error_description": "Token has been expired or revoked."
}
Application "Idealista 2 Messenger" has finished processing

1. Delete the config/token.json file: rm -rf config/token.json
2. Run the application to regenerate it (See Obtain the token.json file section)

Other issues

If you have any questions, just submit an Issue with all the details.