Add Assist timers

[synesthesiam]

Proposed change

Adds support for timers to Assist. These timers are internal to Assist and do not persist across HA restarts.

Sentences have not been added yet, just intents!

Capabilities

The following capabilities for timers are supported:

• Starting a timer with hours/minutes/seconds and an optional name
• Pausing and unpausing
• Adding and removing time
• Cancelling
• Getting the status
• Attaching an Assist command for when the timer finishes (more below)

Targeting Timers

When performing an action on a timer, such as pausing or cancelling, the timer must be targeted with constraints. Multiple timers cannot be targeted, so the constraints must result in one timer.

The following explicit constraints are supported:

• Name - "cancel pizza timer"
• Start time - "pause 5 second timer"
• Ordinal - "add a minute to the 2nd 10 minute timer"

There are also implicit constraints when timers are set with a device_id. In this case, timers in the same area are prioritized, followed by timers on the same floor.

Attaching Assist Commands

User data may be attached to a timer when started and forwarded to consumers of timer events. A special data.assist_command key allows a text command to be executed when the timer is finished.

This feature enables sentences like "open the garage door in 5 minutes" and "turn off all lights in an hour".

Implementation

Assist timers are implemented using events and asyncio.sleep in background tasks. Timer events include:

• intent.timer_started - fired when a timer starts
• intent.timer_updated - fired when a timer is paused/unpaused or time is added/removed
• intent.timer_cancelled - fired when a timer is cancelled
• intent.timer_finished - fired when a timer finishes successfully (not cancelled)

Using events makes it very easy for other integrations to make use of Assist timers, and makes it possible to users to create automations with them.

All information about the timer, including the device it was set on and language used to set it, are included with each event.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Deprecation (breaking change to happen in the future)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue:
• Link to documentation pull request:

Checklist

• The code change is tested and works locally.
• Local tests pass. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.
• I have followed the development checklist
• I have followed the perfect PR recommendations
• The code has been formatted using Ruff (ruff format homeassistant tests)
• Tests have been added to verify that the new code works.

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated for www.home-assistant.io

If the code communicates with devices, web services, or third-party tools:

• The manifest file has all fields filled out correctly.
  Updated and included derived files by running: python3 -m script.hassfest.
• New or updated dependencies have been added to requirements_all.txt.
  Updated by running python3 -m script.gen_requirements_all.
• For the updated dependencies - a link to the changelog, or at minimum a diff between library versions is added to the PR description.
• Untested files have been added to .coveragerc.

To help with the load of incoming pull requests:

• I have reviewed two other open pull requests in this repository.

[home-assistant]

Hey there @home-assistant/core, mind taking a look at this pull request as it has been labeled with an integration (conversation) you are listed as a code owner for? Thanks!

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[home-assistant]

Hey there @home-assistant/core, mind taking a look at this pull request as it has been labeled with an integration (intent) you are listed as a code owner for? Thanks!

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• @home-assistant close Closes the pull request.
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[balloob]

the downside of not using UTC seconds is that we cannot share this info with other consumers. Not sure if we want this? I guess we can add it later.

[balloob]

Looks good! Can be merged if my final comments addressed