Blink(1) for Google Calendar (calblink)

What is this?

Calblink is a small program to watch your Google Calendar and set a blink(1) USB LED to change colors based on your next meeting. The colors it will use are:

• Off: nothing on your calendar for the next 60 minutes
• Green: 30 to 60 minutes
• Yellow: 10 to 30 minutes
• Red: 5 to 10 minutes
• Flashing red: 0 to 5 minutes, flashing faster for the last 2 minutes
• Flashing blue and red: First minute of the meeting
• Blue: In meeting
• Flashing magenta: Unable to connect to Calendar server. This is to prevent the case where calblink silently fails and leaves you unaware that it has failed.

What do I need use it?

To use calblink, you need the following:

1. A blink(1) from ThingM - calblink supports mk1, mk2, and mk3 blink(1).
2. A place to connect the blink(1) where you can see it.
3. The latest version of Go.
4. The calblink code, found in this directory.
5. libusb-compat. The go-blink1 page has details.
6. A directory to run this in.
7. A few go packages, which we'll install later in the Setup section.
8. A Google Calendar account.
9. A Google Calendar OAuth 2 client ID. (We'll discuss getting one in the Setup section as well.)

How do I set this up?

1. Install Go, and plug your blink(1) in somewhere that you can see it.

2. Bring up a command-line window, and create the directory you want to run this in.

3. Put calblink.go into the directory you just created.

4. Install libusb-compat, if needed.

5. Create your module file:

   go mod init calblink
   go mod tidy
   

6. Get an OAuth 2 ID as described in step 1 of the Google Calendar Quickstart. Put the client_secret.json file in your GOPATH directory.

7. Build the calblink program as appropriate for your environment:

   • For a Linux environment or another that doesn't use Homebrew:

       go build calblink.go
     

   • For a default Homebrew install on an Intel-based Mac:

       CGO_LDFLAGS="-L/usr/local/lib" CGO_CFLAGS="-I/usr/local/include" go build calblink.go
     

   • For a default Homebrew install on an ARM-based Mac:

       CGO_LDFLAGS="-L/opt/homebrew/lib" CGO_CFLAGS="-I/opt/homebrew/include" go build calblink.go
     

   • For a customized Homebrew install, modify the above to match your configuration.

8. Run the calblink program:

   ./calblink
   

9. It will request that you go to a URL. On macOS, it will also request that you allow the program to receive network requests; you should allow this. You should access this URL from the account you want to read the calendar of.

10. That's it! It should just run now, and set your blink(1) to change color appropriately. To quit out of it, hit Ctrl-C in the window you ran it in. (It will turn the blink(1) off automatically.) It will output a . into the terminal window every time it checks the server and sets the LED.

11. Optionally, set up a config file, as below.

What are the configuration options?

First off, run it with the --help option to see what the command-line options are. Useful, perhaps, but maybe not what you want to use every time you run it.

calblink will look for a file named (by default) conf.json for its configuration options. conf.json includes several useful options you can set:

• excludes - a list of event titles which it will ignore. If you like blocking out time with "Make Time" or similar, you can add these names to the 'excludes' array.
• excludePrefixes - a list of event title prefixes which it will ignore. This is useful for blocks that start consistently but may not end consistently, such as "On call, secondary is PERSON".
• startTime - an HH:MM time (24-hour clock) which calblink won't turn on before. Because you might not want it turning on at 4am.
• endTime - an HH:MM time (24-hour clock) which it won't turn on after.
• skipDays - a list of days of the week that it should skip. A blink(1) in the offices doesn't need to run on Saturday/Sunday, after all, and if you WFH every Friday, why distract your coworkers?
• pollInterval - how often (in seconds) it should check with Calendar for an update. Default is 30 seconds. Don't push this too frequent or you'll run out of API quota.
• calendar - which calendar to watch (defaults to primary). This is the email address of the calendar - either the calendar's owner, or the ID in its details page for a secondary calendar. "primary" is a magic string that means "the main calendar of the account whose auth token I'm using".
• calendars - array of calendars to watch. This will override calendar if it is set. All calendars listed will be watched for events. Note that the signed-in account must have access to all calendars, and that if you query too many calendars you may run into issues with the free query quota for Google Calendar, especially if you are using your oauth key in multiple locations.
• responseState - which response states are marked as being valid for a meeting. Can be set to "all", in which case any item on your calendar will light up; "accepted", in which case only items marked as 'accepted' on calendar will light up; or "notRejected", in which case items that you have rejected will not light up. Default is "notRejected".
• deviceFailureRetries - how many times to retry accessing the blink(1) before failing out and terminating the program. Default is 10.
• showDots - whether to show a dot (or similar mark) after every poll interval to show that the program is running. Default is true. Symbols have the following meanings:
  • . - working normally
  • , - unable to talk to the calendar server. After 3 consecutive failures, the blink(1) will be set to flashing magenta to indicate that it is no longer current.
  • < - sleeping because we've reached endTime for today.
  • > - sleeping because we haven't reached startTime yet today.
  • ~ - sleeping because it's a skip day
  • X - device failure.
• multiEvent - if true, calblink will check the next two events, and if they are both in the time frame to show, it will show both.
• priorityFlashSide - if 0 (the default), which side of the blink(1) is flashing will not be adjusted. If set to 1, then flashing will be prioritized on LED 1; if 2, flashing will be prioritized on LED2. Any other values are undefined.
• workingLocations - a list of working locations to filter results by. If all calendars with working locations set have locations that are not in the list of locations, no events will be shown. Handling of multiple calendars with working locations set may be suboptimal - if one calendar is set to homeOffice and another is set to an office location, both will be valid for all events on either calendar. Values should be in the following formats:
  • 'home' to indicate WFH
  • 'office:NAME' to match an office location called NAME.
  • 'custom:NAME' to match a custom location called NAME.

An example file:

    {
        "excludes": ["Commute"],
        "skipDays": ["Saturday", "Sunday"],
        "startTime": "08:45",
        "endTime": "18:00",
        "pollInterval": 60,
        "calendars": ["primary", "username@example.com"],
        "responseState": "accepted",
        "multiEvent": "true",
        "priorityFlashSide": 1,
        "workingLocations": ["home"]
    }

(Yes, the curly braces are required. Sorry. It's a JSON dictionary.)

New Requirements

In addition to the existing setup, please ensure the following requirements are met:

1. File Permission Check: The client secret file (client_secret.json) must have restricted permissions to ensure sensitive credentials are protected.

Why This Change is Necessary

Ensuring that sensitive files, such as client secret files containing authentication credentials, are accessible only by authorized users is crucial for preventing unauthorized access and potential security breaches. By implementing a file permission check, we mitigate the risk of exposing sensitive information to unauthorized users or processes.

Configuration Notes:

To comply with the new security measure and meet the new requirements, please follow these configuration steps:

1. File Permission Requirement:
   • Ensure that the client secret file (client_secret.json) is only readable by the owner. This can be achieved by setting appropriate file permissions using the chmod command. For example:

     chmod 600 client_secret.json
     

   This command restricts read and write permissions to the owner only, ensuring that sensitive credentials are protected from unauthorized access.

Known Issues

• Occasionally the shutdown is not as clean as it should be.

Troubleshooting

• If the blink(1) is flashing magenta, this means it was unable to connect to or authenticate to the Google Calendar server. If your network is okay, your auth token may have expired. Remove ~/.credentials/calendar-blink1.json and reconnect the app to your account.
• Another reason it may flash magenta is an issue with Go 1.8 and Xcode 8.3 or later. Upgrade to Go 1.8.1 to fix this issue.
• If attempting to install the blink1 go library or run calblink.go on OSX gives an error about "'usb.h' file not found", make sure that C_INCLUDE_PATH and LIBRARY_PATH are set appropriately.
• Sending a SIGQUIT will turn on debug mode while the app is running. By default on Unix-based systems, this is sent by hitting Ctrl-\ (backslash). There is currently no way to turn debug mode off once it is set.

Legal

• Calblink is not an official Google product.
• Calblink is licensed under the Apache 2 license; see the LICENSE file for details.
• Calblink contains code from the Google Calendar API Quickstart which is licensed under the Apache 2 license.
• All trademarks are the property of their respective holders.