feat: create Theme class and registry with finalized color gradients

engine/themes.py

@@ -0,0 +1,60 @@
+"""
+Theme definitions with color gradients for terminal rendering.
+
+This module is data-only and does not import config or render
+to prevent circular dependencies.
+"""
+
+
+class Theme:
+    """Represents a color theme with two gradients."""
+
+    def __init__(self, name, main_gradient, message_gradient):
+        """Initialize a theme with name and color gradients.
+
+        Args:
+            name: Theme identifier string
+            main_gradient: List of 12 ANSI 256-color codes for main gradient
+            message_gradient: List of 12 ANSI 256-color codes for message gradient
+        """
+        self.name = name
+        self.main_gradient = main_gradient
+        self.message_gradient = message_gradient
+
+
+# ─── GRADIENT DEFINITIONS ─────────────────────────────────────────────────
+# Each gradient is 12 ANSI 256-color codes in sequence
+# Format: [light...] → [medium...] → [dark...] → [black]
+
+_GREEN_MAIN = [231, 195, 123, 118, 82, 46, 40, 34, 28, 22, 22, 235]
+_GREEN_MSG = [231, 225, 219, 213, 207, 201, 165, 161, 125, 89, 89, 235]
+
+_ORANGE_MAIN = [231, 215, 209, 208, 202, 166, 130, 94, 58, 94, 94, 235]
+_ORANGE_MSG = [231, 195, 33, 27, 21, 21, 21, 18, 18, 18, 18, 235]
+
+_PURPLE_MAIN = [231, 225, 177, 171, 165, 135, 129, 93, 57, 57, 57, 235]
+_PURPLE_MSG = [231, 226, 226, 220, 220, 184, 184, 178, 178, 172, 172, 235]
+
+
+# ─── THEME REGISTRY ───────────────────────────────────────────────────────
+
+THEME_REGISTRY = {
+    "green": Theme("green", _GREEN_MAIN, _GREEN_MSG),
+    "orange": Theme("orange", _ORANGE_MAIN, _ORANGE_MSG),
+    "purple": Theme("purple", _PURPLE_MAIN, _PURPLE_MSG),
+}
+
+
+def get_theme(theme_id):
+    """Retrieve a theme by ID.
+
+    Args:
+        theme_id: Theme identifier string
+
+    Returns:
+        Theme object matching the ID
+
+    Raises:
+        KeyError: If theme_id is not in registry
+    """
+    return THEME_REGISTRY[theme_id]

tests/test_themes.py

@@ -0,0 +1,169 @@
+"""
+Tests for engine.themes module.
+"""
+
+import pytest
+
+from engine import themes
+
+
+class TestThemeConstruction:
+    """Tests for Theme class initialization."""
+
+    def test_theme_construction(self):
+        """Theme stores name and gradients correctly."""
+        main_grad = ["color1", "color2", "color3"]
+        msg_grad = ["msg1", "msg2", "msg3"]
+        theme = themes.Theme("test_theme", main_grad, msg_grad)
+
+        assert theme.name == "test_theme"
+        assert theme.main_gradient == main_grad
+        assert theme.message_gradient == msg_grad
+
+
+class TestGradientLength:
+    """Tests for gradient length validation."""
+
+    def test_gradient_length_green(self):
+        """Green theme has exactly 12 colors in each gradient."""
+        green = themes.THEME_REGISTRY["green"]
+        assert len(green.main_gradient) == 12
+        assert len(green.message_gradient) == 12
+
+    def test_gradient_length_orange(self):
+        """Orange theme has exactly 12 colors in each gradient."""
+        orange = themes.THEME_REGISTRY["orange"]
+        assert len(orange.main_gradient) == 12
+        assert len(orange.message_gradient) == 12
+
+    def test_gradient_length_purple(self):
+        """Purple theme has exactly 12 colors in each gradient."""
+        purple = themes.THEME_REGISTRY["purple"]
+        assert len(purple.main_gradient) == 12
+        assert len(purple.message_gradient) == 12
+
+
+class TestThemeRegistry:
+    """Tests for THEME_REGISTRY dictionary."""
+
+    def test_theme_registry_has_three_themes(self):
+        """Registry contains exactly three themes: green, orange, purple."""
+        assert len(themes.THEME_REGISTRY) == 3
+        assert set(themes.THEME_REGISTRY.keys()) == {"green", "orange", "purple"}
+
+    def test_registry_values_are_themes(self):
+        """All registry values are Theme instances."""
+        for theme_id, theme in themes.THEME_REGISTRY.items():
+            assert isinstance(theme, themes.Theme)
+            assert theme.name == theme_id
+
+
+class TestGetTheme:
+    """Tests for get_theme function."""
+
+    def test_get_theme_valid_green(self):
+        """get_theme('green') returns correct green Theme."""
+        green = themes.get_theme("green")
+        assert isinstance(green, themes.Theme)
+        assert green.name == "green"
+
+    def test_get_theme_valid_orange(self):
+        """get_theme('orange') returns correct orange Theme."""
+        orange = themes.get_theme("orange")
+        assert isinstance(orange, themes.Theme)
+        assert orange.name == "orange"
+
+    def test_get_theme_valid_purple(self):
+        """get_theme('purple') returns correct purple Theme."""
+        purple = themes.get_theme("purple")
+        assert isinstance(purple, themes.Theme)
+        assert purple.name == "purple"
+
+    def test_get_theme_invalid(self):
+        """get_theme with invalid ID raises KeyError."""
+        with pytest.raises(KeyError):
+            themes.get_theme("invalid_theme")
+
+    def test_get_theme_invalid_none(self):
+        """get_theme with None raises KeyError."""
+        with pytest.raises(KeyError):
+            themes.get_theme(None)
+
+
+class TestGreenTheme:
+    """Tests for green theme specific values."""
+
+    def test_green_theme_unchanged(self):
+        """Green theme maintains original color sequence."""
+        green = themes.get_theme("green")
+
+        # Expected main gradient: 231→195→123→118→82→46→40→34→28→22→22(dim)→235
+        expected_main = [231, 195, 123, 118, 82, 46, 40, 34, 28, 22, 22, 235]
+        # Expected msg gradient: 231→225→219→213→207→201→165→161→125→89→89(dim)→235
+        expected_msg = [231, 225, 219, 213, 207, 201, 165, 161, 125, 89, 89, 235]
+
+        assert green.main_gradient == expected_main
+        assert green.message_gradient == expected_msg
+
+    def test_green_theme_name(self):
+        """Green theme has correct name."""
+        green = themes.get_theme("green")
+        assert green.name == "green"
+
+
+class TestOrangeTheme:
+    """Tests for orange theme specific values."""
+
+    def test_orange_theme_unchanged(self):
+        """Orange theme maintains original color sequence."""
+        orange = themes.get_theme("orange")
+
+        # Expected main gradient: 231→215→209→208→202→166→130→94→58→94→94(dim)→235
+        expected_main = [231, 215, 209, 208, 202, 166, 130, 94, 58, 94, 94, 235]
+        # Expected msg gradient: 231→195→33→27→21→21→21→18→18→18→18(dim)→235
+        expected_msg = [231, 195, 33, 27, 21, 21, 21, 18, 18, 18, 18, 235]
+
+        assert orange.main_gradient == expected_main
+        assert orange.message_gradient == expected_msg
+
+    def test_orange_theme_name(self):
+        """Orange theme has correct name."""
+        orange = themes.get_theme("orange")
+        assert orange.name == "orange"
+
+
+class TestPurpleTheme:
+    """Tests for purple theme specific values."""
+
+    def test_purple_theme_unchanged(self):
+        """Purple theme maintains original color sequence."""
+        purple = themes.get_theme("purple")
+
+        # Expected main gradient: 231→225→177→171→165→135→129→93→57→57→57(dim)→235
+        expected_main = [231, 225, 177, 171, 165, 135, 129, 93, 57, 57, 57, 235]
+        # Expected msg gradient: 231→226→226→220→220→184→184→178→178→172→172(dim)→235
+        expected_msg = [231, 226, 226, 220, 220, 184, 184, 178, 178, 172, 172, 235]
+
+        assert purple.main_gradient == expected_main
+        assert purple.message_gradient == expected_msg
+
+    def test_purple_theme_name(self):
+        """Purple theme has correct name."""
+        purple = themes.get_theme("purple")
+        assert purple.name == "purple"
+
+
+class TestThemeDataOnly:
+    """Tests to ensure themes module has no problematic imports."""
+
+    def test_themes_module_imports(self):
+        """themes module should be data-only without config/render imports."""
+        import inspect
+        source = inspect.getsource(themes)
+        # Verify no imports of config or render (look for actual import statements)
+        lines = source.split('\n')
+        import_lines = [line for line in lines if line.strip().startswith('import ') or line.strip().startswith('from ')]
+        # Filter out empty and comment lines
+        import_lines = [line for line in import_lines if line.strip() and not line.strip().startswith('#')]
+        # Should have no import lines
+        assert len(import_lines) == 0, f"Found unexpected imports: {import_lines}"