Refactors datamodel (#49)

* Refactors datamodel

Major changes:
- Create dedicated Statifier.Datamodel module for all datamodel operations
- Rename DataElement to Data for consistency with SCXML <data> elements
- Extract common In() function setup to reduce code duplication
- Consolidate datamodel tests into single comprehensive test file

Datamodel module features:
- Initialize datamodel from <data> elements with expression evaluation
- Build evaluation contexts for conditions and expressions
- Support for datamodel variable access (get/set/has/merge)
- Proper event data merging as top-level variables in conditions
- Session ID generation and SCXML built-in variables

Code quality improvements:
- Fix all credo consistency issues (meaningful unused variable names)
- Eliminate duplicate code between ConditionEvaluator and ValueEvaluator
- Extract common test setup with helper functions
- Pass all dialyzer type checks with no errors
- Achieve 0 credo issues with --strict flag

Testing improvements:
- Combine datamodel_test.exs and datamodel_init_test.exs
- Add comprehensive edge case testing
- Use setup blocks and helper functions to reduce duplication
- All 361 tests passing with 91.2% coverage

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

* Improves context handling

This refactor simplifies context building across evaluators and improves naming consistency:

- Replace complex tuple-based context with direct StateChart parameter
- Unify context building in `Datamodel.build_evaluation_context/2`
- Eliminate redundant `|| %{}` checks (field is always a map)
- Single source of truth for SCXML context preparation

- Rename StateChart field: `data_model` → `datamodel`
- Update helper function: `update_data_model/2` → `update_datamodel/2`
- Use proper typing: `Statifier.Datamodel.t()` instead of generic `map()`
- Consistent naming across codebase matches module name

- Cleaner evaluator APIs: `evaluate_condition(compiled, state_chart)`
- Remove complex context building from individual modules
- Better type safety and Dialyzer compliance (0 warnings)
- More intuitive parameter passing throughout

- Reduced code duplication across evaluators
- Better type documentation and IDE support
- Simplified test code with cleaner StateChart initialization
- All 566 tests passing with 91.9% coverage maintained

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

* Consolidates evaluators and improves datamodel

- Consolidate ConditionEvaluator and ValueEvaluator into unified Statifier.Evaluator module
- Move put_in_path function from Evaluator to Datamodel module for better separation of concerns
- Update all imports across codebase to use new unified evaluator
- Remove old evaluator modules and tests, create comprehensive consolidated test suite
- Improve error handling in Datamodel.put_in_path with proper {:ok, result} | {:error, reason} pattern
- Prepare architecture for future pluggable datamodel support (ECMAScript, XPath)

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

* Adds new passing SCION and SCXML tests

- Mark datamodel and data_elements as :supported in feature registry
- Update feature detector tests to reflect new datamodel support status
- Add 13 new passing tests to baseline (9 SCION, 4 W3C)
- New test categories: assign actions, data model initialization, foreach loops, if/else control flow
- Significant progress in SCXML compliance: 61/184 total tests now passing (33%)

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

* Adds datamodel, evaluator improvements to docs

- Document unified Statifier.Evaluator module consolidation
- Detail enhanced Datamodel module with improved error handling
- Record 13 new passing tests unlocked by these improvements
- Track progress from 48/184 to 61/184 total tests passing (33% compliance)
- Update feature detection improvements and test baseline changes

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

---------

Co-authored-by: Claude <noreply@anthropic.com>

Author: johnnyt

.githooks/pre-push

@@ -67,10 +67,10 @@ fi
 
 # Run type checking (optional - can be slow)
 # Uncomment if you want type checking in the pre-push hook
-# echo "🔬 Running type checking (Dialyzer)..."
-# if ! mix dialyzer; then
-#     echo "❌ Dialyzer type checking failed."
-#     exit 1
-# fi
+echo "🔬 Running type checking (Dialyzer)..."
+if ! mix dialyzer; then
+    echo "❌ Dialyzer type checking failed."
+    exit 1
+fi
 
 echo "✅ All validation checks passed! Ready to push."

CHANGELOG.md

@@ -7,6 +7,42 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+#### Architecture Improvements
+
+- **Unified `Statifier.Evaluator` Module**: Consolidated `ConditionEvaluator` and `ValueEvaluator` into single module
+  - **Single Entry Point**: One module for all expression evaluation (conditions and values)
+  - **Improved Maintainability**: Eliminated code duplication between evaluator modules
+  - **Future Extensibility**: Better prepared for pluggable datamodel architectures (ECMAScript, XPath)
+  - **Consistent API**: Unified function signatures and error handling patterns
+
+- **Enhanced `Statifier.Datamodel` Module**: Improved data model operations and separation of concerns
+  - **`put_in_path/3` Function**: Moved from Evaluator to Datamodel for better architecture
+  - **Improved Error Handling**: Returns `{:ok, result} | {:error, reason}` instead of raising exceptions
+  - **Type Safety**: Proper `Datamodel.t()` typing throughout the codebase
+  - **Data Model Operations**: Centralized location for all data model manipulation logic
+
+- **Feature Detection Updates**: Enhanced SCXML feature tracking for better test validation
+  - **Datamodel Support**: Marked `:datamodel` and `:data_elements` as `:supported` in feature registry
+  - **Accurate Test Results**: Prevents false test failures from unsupported feature detection
+  - **Better Compliance Tracking**: Improved visibility into SCXML feature implementation status
+
+### Changed
+
+#### Test Coverage Improvements
+
+- **13 New Passing Tests**: Unlocked additional test coverage through datamodel improvements
+  - **9 SCION Tests**: Including assign actions, current small step assignments, data initialization
+  - **4 W3C Tests**: Including executable content evaluation, foreach loops, conditional execution
+  - **Test Categories**: `assign/`, `assign_current_small_step/`, `data/`, `foreach/`, `if_else/`
+  - **Overall Progress**: Improved from 48/184 to 61/184 total tests passing (33% compliance)
+
+- **Updated Test Baseline**: Added new passing tests to regression test suite
+  - **SCION Tests**: 44 → 53 passing tests
+  - **W3C Tests**: 5 → 9 passing tests
+  - **Maintained Quality**: All 98 regression tests continue to pass
+
 ## [1.1.0] 2025-08-26
 
 ### Added
@@ -42,9 +78,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 #### StateChart Data Model Enhancement
 
-- **Data Model Storage**: Added `data_model` field to `Statifier.StateChart` for variable persistence
+- **Datamodel Storage**: Added `datamodel` field to `Statifier.StateChart` for variable persistence
 - **Current Event Context**: Added `current_event` field for expression evaluation context
-- **Helper Methods**: `update_data_model/2` and `set_current_event/2` for state management
+- **Helper Methods**: `update_datamodel/2` and `set_current_event/2` for state management
 - **SCXML Context Building**: Enhanced context building for comprehensive expression evaluation
 
 #### Parser Extensions

CLAUDE.md

@@ -71,7 +71,7 @@ Also use this initial Elixir implementation as reference: <https://github.com/ca
   - Built via `Document.build_lookup_maps/1` during validation phase
 - **`Statifier.State`** - Individual state with `id`, optional `initial` state, nested `states` list, and `transitions` list
 - **`Statifier.Transition`** - State transitions with optional `event`, `target`, and `cond` attributes
-- **`Statifier.DataElement`** - Datamodel elements with required `id` and optional `expr` and `src` attributes
+- **`Statifier.Data`** - Datamodel elements with required `id` and optional `expr` and `src` attributes
 
 ### Parsers (Parse Phase)
 
@@ -124,7 +124,7 @@ Also use this initial Elixir implementation as reference: <https://github.com/ca
 - **`Statifier.StateChart`** - Runtime container for SCXML state machines
   - Combines document, configuration, event queues, and data model
   - Maintains internal and external event queues per SCXML specification
-  - **Data model storage**: Persistent variable storage with `data_model` field
+  - **Datamodel storage**: Persistent variable storage with `datamodel` field
   - **Current event context**: Tracks current event for expression evaluation
 - **`Statifier.Configuration`** - Active state configuration management
   - Stores only leaf states for efficient memory usage
@@ -207,7 +207,7 @@ The implementation follows a clean **Parse → Validate → Optimize** architect
 
 All parsed SCXML elements include precise source location information for validation error reporting:
 
-- **Element locations**: Each parsed element (`Statifier.Document`, `Statifier.State`, `Statifier.Transition`, `Statifier.DataElement`) includes a `source_location` field with line/column information
+- **Element locations**: Each parsed element (`Statifier.Document`, `Statifier.State`, `Statifier.Transition`, `Statifier.Data`) includes a `source_location` field with line/column information
 - **Attribute locations**: Individual attributes have dedicated location fields (e.g., `name_location`, `id_location`, `event_location`) for precise error reporting
 - **Multiline support**: Accurately tracks locations for both single-line and multiline XML element definitions
 - **SAX-based tracking**: Uses Saxy's event-driven parsing to maintain position information throughout the parsing process
@@ -332,7 +332,7 @@ XML content within triple quotes uses 4-space base indentation.
 
 ✅ **Completed:**
 
-- Core data structures (Document, State, Transition, DataElement) with location tracking
+- Core data structures (Document, State, Transition, Data) with location tracking
 - SCXML parser using Saxy SAX parser for accurate position tracking
 - **Parse → Validate → Optimize architecture** with clean separation of concerns
 - Complete interpreter infrastructure (Interpreter, StateChart, Configuration, Event, Validator)  

README.md

@@ -107,7 +107,6 @@ The next major areas for development focus on expanding SCXML feature support:
 ### **High Priority Features**
 
 - **Executable Content** - `<script>` elements (`<onentry>`, `<onexit>`, `<assign>` now supported!)
-- **Datamodel Support** - `<data>` elements with expression evaluation
 - **History States** - Shallow and deep history state support
 
 ### **Medium Priority Features**  
@@ -273,7 +272,7 @@ xml = """
 {:ok, state_chart} = Statifier.interpret(document)
 
 # Check the data model after onentry execution
-data_model = state_chart.data_model
+datamodel = state_chart.datamodel
 # Returns: %{
 #   "userName" => "John Doe",
 #   "counter" => 43,  # incremented to 43 in working state
@@ -306,7 +305,7 @@ The project maintains high code quality through automated checks:
 mix format              # Auto-fix formatting
 mix test.regression     # Run critical regression tests (22 tests)
 mix credo --strict      # Static code analysis
-mix dialyzer           # Type checking
+mix dialyzer            # Type checking
 ```
 
 ### Regression Testing
@@ -367,7 +366,7 @@ mix test test/statifier/parser/scxml_test.exs
 - **`Statifier.Document`** - Root SCXML document with states, metadata, and O(1) lookup maps
 - **`Statifier.State`** - Individual states with transitions and hierarchical nesting support
 - **`Statifier.Transition`** - State transitions with events and targets
-- **`Statifier.DataElement`** - Datamodel elements with expressions
+- **`Statifier.Data`** - Datamodel elements with expressions
 
 ### Architecture Flow
 
@@ -486,7 +485,7 @@ git push origin feature-branch
 - All code is formatted with `mix format`
 - Static analysis with Credo (strict mode)
 - Type checking with Dialyzer
-- Comprehensive test coverage (95%+ maintained)
+- Comprehensive test coverage (90%+ maintained)
 - Detailed documentation with `@moduledoc` and `@doc`
 - Pattern matching preferred over multiple assertions in tests
 - Git pre-push hook enforces validation workflow automatically
@@ -500,5 +499,3 @@ This project is licensed under the MIT License - see the [LICENSE](LICENSE) file
 
 - [W3C SCXML Specification](https://www.w3.org/TR/scxml/) - Official specification
 - [SCION Test Suite](https://github.com/jbeard4/SCION) - Comprehensive test cases
-- [ex_statechart](https://github.com/camshaft/ex_statechart) - Reference implementation
-

lib/statifier/actions/assign_action.ex

@@ -27,7 +27,7 @@ defmodule Statifier.Actions.AssignAction do
 
   """
 
-  alias Statifier.{StateChart, ValueEvaluator}
+  alias Statifier.{Evaluator, StateChart}
 
   require Logger
 
@@ -73,7 +73,7 @@ defmodule Statifier.Actions.AssignAction do
 
   # Safely compile expressions, returning nil on error
   defp compile_safe(expr, _type) do
-    case ValueEvaluator.compile_expression(expr) do
+    case Evaluator.compile_expression(expr) do
       {:ok, compiled} -> compiled
       {:error, _reason} -> nil
     end
@@ -82,7 +82,7 @@ defmodule Statifier.Actions.AssignAction do
   @doc """
   Execute the assign action by evaluating the expression and assigning to the location.
 
-  This uses Statifier.ValueEvaluator to:
+  This uses Statifier.Evaluator to:
   1. Validate the assignment location path
   2. Evaluate the expression to get the value
   3. Perform the assignment in the data model
@@ -91,18 +91,16 @@ defmodule Statifier.Actions.AssignAction do
   """
   @spec execute(t(), StateChart.t()) :: StateChart.t()
   def execute(%__MODULE__{} = assign_action, %StateChart{} = state_chart) do
-    context = build_evaluation_context(state_chart)
-
-    # Use ValueEvaluator.evaluate_and_assign with pre-compiled expression if available
-    case ValueEvaluator.evaluate_and_assign(
+    # Use Evaluator.evaluate_and_assign with pre-compiled expression if available
+    case Evaluator.evaluate_and_assign(
            assign_action.location,
            assign_action.expr,
-           context,
+           state_chart,
            assign_action.compiled_expr
          ) do
-      {:ok, updated_data_model} ->
-        # Update the state chart with the new data model
-        %{state_chart | data_model: updated_data_model}
+      {:ok, updated_datamodel} ->
+        # Update the state chart with the new datamodel
+        %{state_chart | datamodel: updated_datamodel}
 
       {:error, reason} ->
         # Log the error and continue without modification
@@ -114,13 +112,4 @@ defmodule Statifier.Actions.AssignAction do
         state_chart
     end
   end
-
-  # Build evaluation context for assign action execution
-  defp build_evaluation_context(%StateChart{} = state_chart) do
-    %{
-      configuration: state_chart.configuration,
-      current_event: state_chart.current_event,
-      data_model: state_chart.data_model || %{}
-    }
-  end
 end

lib/statifier/condition_evaluator.ex

@@ -1,6 +1,9 @@
-defmodule Statifier.DataElement do
+defmodule Statifier.Data do
   @moduledoc """
   Represents a data element in an SCXML datamodel.
+
+  Corresponds to SCXML `<data>` elements which define variables in the state machine's datamodel.
+  Each data element has an `id` (required) and optional `expr` or `src` for initialization.
   """
 
   defstruct [