feat(blueprint): Add feature evaluator

go.mod

@@ -7,6 +7,7 @@ require (
 	github.com/abiosoft/colima v0.8.4
 	github.com/briandowns/spinner v1.23.2
 	github.com/compose-spec/compose-go/v2 v2.8.2
+	github.com/expr-lang/expr v1.17.6
 	github.com/fluxcd/helm-controller/api v1.3.0
 	github.com/fluxcd/kustomize-controller/api v1.6.1
 	github.com/fluxcd/pkg/apis/kustomize v1.11.0

go.sum

@@ -189,6 +189,8 @@ github.com/envoyproxy/protoc-gen-validate v1.2.1 h1:DEo3O99U8j4hBFwbJfrz9VtgcDfU
 github.com/envoyproxy/protoc-gen-validate v1.2.1/go.mod h1:d/C80l/jxXLdfEIhX1W2TmLfsJ31lvEjwamM4DxlWXU=
 github.com/evanphx/json-patch/v5 v5.9.11 h1:/8HVnzMq13/3x9TPvjG08wUGqBTmZBsCWzjTM0wiaDU=
 github.com/evanphx/json-patch/v5 v5.9.11/go.mod h1:3j+LviiESTElxA4p3EMKAB9HXj3/XEtnUf6OZxqIQTM=
+github.com/expr-lang/expr v1.17.6 h1:1h6i8ONk9cexhDmowO/A64VPxHScu7qfSl2k8OlINec=
+github.com/expr-lang/expr v1.17.6/go.mod h1:8/vRC7+7HBzESEqt5kKpYXxrxkr31SaO8r40VO/1IT4=
 github.com/extism/go-sdk v1.7.1 h1:lWJos6uY+tRFdlIHR+SJjwFDApY7OypS/2nMhiVQ9Sw=
 github.com/extism/go-sdk v1.7.1/go.mod h1:IT+Xdg5AZM9hVtpFUA+uZCJMge/hbvshl8bwzLtFyKA=
 github.com/fatih/color v1.18.0 h1:S8gINlzdQ840/4pfAwic/ZE0djQEH3wM94VfqLTZcOM=

pkg/blueprint/feature_evaluator.go

@@ -0,0 +1,169 @@
+package blueprint
+
+import (
+	"fmt"
+
+	"github.com/expr-lang/expr"
+)
+
+// FeatureEvaluator provides lightweight expression evaluation for blueprint feature conditions.
+// It uses the expr library for fast compilation and evaluation of simple comparison expressions
+// without the overhead of a full expression language like CEL for basic equality checks.
+// The FeatureEvaluator enables efficient feature activation based on user configuration values.
+
+// =============================================================================
+// Types
+// =============================================================================
+
+// FeatureEvaluator provides lightweight expression evaluation for feature conditions.
+type FeatureEvaluator struct{}
+
+// =============================================================================
+// Constructor
+// =============================================================================
+
+// NewFeatureEvaluator creates a new lightweight feature evaluator for expression evaluation.
+func NewFeatureEvaluator() *FeatureEvaluator {
+	return &FeatureEvaluator{}
+}
+
+// =============================================================================
+// Public Methods
+// =============================================================================
+
+// EvaluateExpression evaluates an expression string against the provided configuration data.
+// The expression should use simple comparison syntax supported by expr:
+// - Equality/inequality: ==, !=
+// - Logical operators: &&, ||
+// - Parentheses for grouping: (expression)
+// - Nested object access: provider, observability.enabled, vm.driver
+// Returns true if the expression evaluates to true, false otherwise.
+func (e *FeatureEvaluator) EvaluateExpression(expression string, config map[string]any) (bool, error) {
+	if expression == "" {
+		return false, fmt.Errorf("expression cannot be empty")
+	}
+
+	program, err := expr.Compile(expression)
+	if err != nil {
+		return false, fmt.Errorf("failed to compile expression '%s': %w", expression, err)
+	}
+
+	result, err := expr.Run(program, config)
+	if err != nil {
+		return false, fmt.Errorf("failed to evaluate expression '%s': %w", expression, err)
+	}
+
+	boolResult, ok := result.(bool)
+	if !ok {
+		return false, fmt.Errorf("expression '%s' must evaluate to boolean, got %T", expression, result)
+	}
+
+	return boolResult, nil
+}
+
+// MatchConditions evaluates whether all conditions in a map match the provided configuration.
+// This provides a simple key-value matching interface for basic feature conditions.
+// Each condition key-value pair must match for the overall result to be true.
+func (e *FeatureEvaluator) MatchConditions(conditions map[string]any, config map[string]any) bool {
+	if len(conditions) == 0 {
+		return true
+	}
+
+	for key, expectedValue := range conditions {
+		if !e.matchCondition(key, expectedValue, config) {
+			return false
+		}
+	}
+
+	return true
+}
+
+// =============================================================================
+// Private Methods
+// =============================================================================
+
+// matchCondition checks if a single condition matches the configuration.
+// Supports dot notation for nested field access and array matching for OR logic.
+func (e *FeatureEvaluator) matchCondition(key string, expectedValue any, config map[string]any) bool {
+	actualValue := e.getNestedValue(key, config)
+
+	if expectedArray, ok := expectedValue.([]any); ok {
+		for _, expected := range expectedArray {
+			if e.valuesEqual(actualValue, expected) {
+				return true
+			}
+		}
+		return false
+	}
+
+	return e.valuesEqual(actualValue, expectedValue)
+}
+
+// getNestedValue retrieves a value from a nested map using dot notation.
+// For example, "observability.enabled" retrieves config["observability"]["enabled"].
+func (e *FeatureEvaluator) getNestedValue(key string, config map[string]any) any {
+	keys := e.splitKey(key)
+	current := config
+
+	for i, k := range keys {
+		if current == nil {
+			return nil
+		}
+
+		value, exists := current[k]
+		if !exists {
+			return nil
+		}
+
+		if i == len(keys)-1 {
+			return value
+		}
+
+		if nextMap, ok := value.(map[string]any); ok {
+			current = nextMap
+		} else {
+			return nil
+		}
+	}
+
+	return nil
+}
+
+// splitKey splits a dot-notation key into its component parts.
+func (e *FeatureEvaluator) splitKey(key string) []string {
+	if key == "" {
+		return []string{}
+	}
+
+	var parts []string
+	current := ""
+
+	for _, char := range key {
+		if char == '.' {
+			if current != "" {
+				parts = append(parts, current)
+				current = ""
+			}
+		} else {
+			current += string(char)
+		}
+	}
+
+	if current != "" {
+		parts = append(parts, current)
+	}
+
+	return parts
+}
+
+// valuesEqual compares two values for equality, handling type conversion.
+func (e *FeatureEvaluator) valuesEqual(actual, expected any) bool {
+	if actual == nil && expected == nil {
+		return true
+	}
+	if actual == nil || expected == nil {
+		return false
+	}
+
+	return fmt.Sprintf("%v", actual) == fmt.Sprintf("%v", expected)
+}