Store agent objectives as a map

[alexdewar]

Description

As we're only currently supporting the "single" objective type (and likely won't support anything else for the forseeable future) I was able to write this in a more simplified way than planned. I've written a check to disable the other objective types for now.

I'm opening this as draft because this might not be uncontroversial 😛. I haven't added commodity IDs as keys to the map yet (#542) because I wanted to run this by you before building on top of it, plus I think it can wait till later anyway.

Instead of a HashMap<u32, Vec<AgentObjective>>, I've gone with HashMap<u32, ObjectiveType>, as a) we will only have one objective per year and b) that objective won't have any additional parameters. Writing things this way made the validation checks simpler and it should be slightly simpler to use too.

Now the check_agent_objectives function is unused outside of the unit tests. I'd be inclined to delete it with the tests for now (we can leave a note somewhere saying we've done this) -- but it's also probably pretty harmless so we could just leave it.

If you're happy with all this, I was planning on refactoring the tests a bit to use rstest fixtures, like elsewhere.

Closes #506.

Type of change

• Bug fix (non-breaking change to fix an issue)
• New feature (non-breaking change to add functionality)
• Refactoring (non-breaking, non-functional change to improve maintainability)
• Optimization (non-breaking change to speed up the code)
• Breaking change (whatever its nature)
• Documentation (improve or add documentation)

Key checklist

• All tests pass: $ cargo test
• The documentation builds and looks OK: $ cargo doc

Further checks

• Code is commented, particularly in hard-to-understand areas
• Tests added that prove fix is effective or that feature works

[Copilot]

Pull Request Overview

This PR refactors agent objectives by changing their representation from a vector to a map keyed by milestone year, simplifying objective lookups and validation logic. Key changes include updating the CSV parsing logic to handle string year representations, refactoring objective validations to populate an AgentObjectiveMap, and adapting related tests and structures accordingly.

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
src/input/agent/objective.rs	Updated CSV parsing and validation for agent objectives; replaced vector with map.
src/input/agent/commodity_portion.rs	Adjusted tests to construct AgentObjectiveMap instead of a vector.
src/input/agent.rs	Updated agent creation and tests to reflect the new objectives representation.
src/agent.rs	Revised documentation and type definitions to use AgentObjectiveMap.

Comments suppressed due to low confidence (1)

src/input/agent/objective.rs:83

• The error message does not properly interpolate the variables 'agent_id' and 'year'. Consider using '{}' placeholders and providing the variables as arguments to ensure the message displays the correct values.

ensure!(agent_objectives.contains_key(year), "Agent {agent_id} is missing objectives for year {year}");

[codecov]

Codecov Report

Attention: Patch coverage is 78.94737% with 8 lines in your changes missing coverage. Please review.

Project coverage is 92.49%. Comparing base (9fda41e) to head (a5de4a0).

Files with missing lines	Patch %	Lines
src/input/agent/objective.rs	77.41%	4 Missing and 3 partials ⚠️
src/input/agent.rs	80.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #543      +/-   ##
==========================================
- Coverage   92.84%   92.49%   -0.35%     
==========================================
  Files          37       37              
  Lines        4274     4173     -101     
  Branches     4274     4173     -101     
==========================================
- Hits         3968     3860     -108     
- Misses        149      153       +4     
- Partials      157      160       +3     

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[tsmbland]

I'm fine with this. Keep the code simple for now. I'd say delete check_agent_objectives and provide a link to this PR in an appropriate place

[tsmbland]

We just need to make sure we keep in the back of our minds that multiple objectives will be added at some point in the future, and do things in a way that makes that as easy as possible when the time comes

[alexdewar]

I meant to mark this as draft before... anyway, this is ready for review now whenever you are.