Clarify cover toggle logic; prevent opening when already open

[vexofp]

Proposed change

This is a follow-on to #106848. During that review, it became clear that the logic by which CoverEntity.toggle() chooses which action to take next was confusing, and could possibly misbehave in some unusual edge cases.

This PR refactors _get_toggle_function() and adds comments to improve clarity. All cases covered by the existing tests continue to work the same. It also adds a new test case for toggling after the unusual state sequence:

1. Closing
2. Fully open

Such a sequence of states might occur if the cover was moved manually or due to dropped communication. Previously in this case, toggle() would map to open_cover(), because the most recent transitional state was "closing" (despite knowing that we are already fully open). The refactored logic correctly maps this case to close_cover().

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: Prevent toggle from calling stop on covers which do not support it #106848 Cover toggle incorrectly calls stop when not supported #106791
• 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 (cover) you are listed as a code owner for? Thanks!

Code owner commands

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[github-actions]

There hasn't been any activity on this pull request recently. This pull request has been automatically marked as stale because of that and will be closed if no further activity occurs within 7 days.
If you are the author of this PR, please leave a comment if you want to keep it open. Also, please rebase your PR onto the latest dev branch to ensure that it's up to date with the latest changes.
Thank you for your contribution!

[bdraco]

not stale, awaits review

[emontnemery]

This looks good, thanks @vexofp 👍

I'd like a second opinion before merging though.

[MartinHjelmare]

Thanks!