feat: add keyword argument support for train_from_stream (#114)

[Yegorov]

Closes #114

[greptile-apps]

Greptile Summary

This PR extends train_from_stream across all four classifiers (Bayes, KNN, LogisticRegression, LSI) to accept multiple categories via keyword arguments (e.g. train_from_stream(spam: io1, ham: io2)), alongside the existing positional form. New tests cover the multi-category path and invalid-IO validation.

• The LSI implementation moves the begin/ensure block inside the per-category loop, causing build_index to fire once per category rather than once after all streams have been loaded.
• Making category and io optional without an explicit guard means callers who supply only one of the two arguments silently get a no-op instead of an error.
• The Streaming base module stub was not updated to match the optional-positional signature now used by every implementation.

Confidence Score: 3/5

The multi-category keyword API is a useful addition, but the LSI implementation rebuilds the index after each category stream and the missing-argument case silently does nothing across all classifiers.

The LSI build_index regression means any caller who streams multiple categories while auto_rebuild is enabled will trigger redundant and increasingly expensive index rebuilds. The silent no-op for partial arguments removes a safety net that existed for free under the old required-parameter contract.

lib/classifier/lsi.rb needs the auto_rebuild guard hoisted outside the loop; lib/classifier/bayes.rb and logistic_regression.rb need an explicit guard for the partial-argument case; lib/classifier/streaming.rb base stub should be updated to match the optional signature.

Important Files Changed

Filename	Overview
lib/classifier/lsi.rb	Moving the begin/ensure block inside the category loop causes build_index to fire after each individual stream instead of once after all categories, breaking the original optimisation.
lib/classifier/bayes.rb	Adds multi-category keyword support. Missing guard means partial argument combinations silently do nothing instead of raising.
lib/classifier/logistic_regression.rb	Same pattern as Bayes; same silent no-op concern applies. synchronize and dirty handling looks structurally correct inside the loop.
lib/classifier/knn.rb	Thin delegation to lsi.train_from_stream; correctly threads **categories through.
lib/classifier/streaming.rb	Base stub not updated to match the optional-positional signature adopted by all implementations; @RBS annotation is also inconsistent.
test/lsi/streaming_test.rb	Adds multi-category and invalid-IO tests; does not cover the auto_rebuild regression.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A["train_from_stream(category=nil, io=nil, **categories)"] --> B{category && io?}
    B -- Yes --> C["{ category => io }"]
    B -- No --> D["categories hash"]
    C --> E[".each do |cat, stream|"]
    D --> E
    E --> F[Validate stream]
    F --> G[LineReader + Progress]
    G --> H[each_batch]
    H --> I[Train + update progress]
    I --> N{More batches?}
    N -- Yes --> H
    N -- No --> O{More categories?}
    O -- Yes --> E
    O -- No --> P[Done]
    subgraph LSI_BUG ["LSI only"]
        Q["save auto_rebuild, set false"]
        R["ensure: restore + build_index per-category"]
    end
    E -.-> Q
    Q --> G
    G -.-> R

Loading

Prompt To Fix All With AI

Fix the following 3 code review issues. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 3
lib/classifier/lsi.rb:667-688
**`build_index` called once per category instead of once after all streams**

The `begin/ensure` block (which saves/restores `@auto_rebuild` and calls `build_index`) is now inside the `.each` loop. When multiple categories are provided, `build_index` fires after every stream rather than once at the end. This defeats the original optimisation: if `auto_rebuild` was `true` before the call, you'll pay the full re-index cost for each category, and every intermediate rebuild immediately becomes obsolete. The fix is to hoist the `auto_rebuild` save, the `@auto_rebuild = false` assignment, and the `ensure` block outside the loop so the index is rebuilt exactly once after all categories have been loaded.

### Issue 2 of 3
lib/classifier/bayes.rb:332-333
**Silent no-op when only one of `category`/`io` is supplied**

When a caller passes only `category` (e.g. `train_from_stream(:spam, batch_size: 100)`) or only `io`, the ternary resolves to `categories` which is an empty hash, so the method returns without training or raising. Before this PR, the required positional parameters made such a call a Ruby `ArgumentError`. Consider an explicit guard to preserve that contract.

```suggestion
    def train_from_stream(category = nil, io = nil, batch_size: Streaming::DEFAULT_BATCH_SIZE, **categories)
      raise ArgumentError, 'Provide either (category, io) or keyword category: io pairs' if category.nil? == io.nil? && category.nil? && categories.empty?
      raise ArgumentError, 'Provide both category and io, or use keyword arguments' if category.nil? ^ io.nil?

      (category && io ? { category => io } : categories).each do |category, io|
```

### Issue 3 of 3
lib/classifier/streaming.rb:29-30
**Base method signature still requires `category` and `io` as positional arguments**

The `Streaming` module's stub still declares `category` and `io` as required, but every concrete implementation now makes them optional. A caller coding to the base interface would be incorrectly told these are mandatory. Update the stub and its `@rbs` annotation to match.

```suggestion
    # @rbs (?(Symbol | String), ?IO, ?batch_size: Integer, **Hash[Symbol, IO]) { (Progress) -> void } -> void
    def train_from_stream(category = nil, io = nil, batch_size: DEFAULT_BATCH_SIZE, **categories, &block)
```

_{Reviews (1): Last reviewed commit: "feat: add keyword argument support for `..." | Re-trigger Greptile}

[Yegorov]

@cardmagic can you take a look, please?