Authorization/services/policy_evaluator.go

package services

import (
	"authorization/models"
	"fmt"
	"log"
	"regexp"
	"strconv"
	"strings"
)

func resolveVariables(value string, ctx *models.AuthorizationContext) string {
	re := regexp.MustCompile(`\$\{([^.]+)\.([^}]+)\}`)

	return re.ReplaceAllStringFunc(value, func(match string) string {
		parts := re.FindStringSubmatch(match)
		if len(parts) != 3 {
			return match
		}

		attrType := parts[1]
		attrName := parts[2]

		switch attrType {
		case "user":
			if val, ok := ctx.UserAttributes[attrName]; ok {
				return val
			}
		case "resource":
			if val, ok := ctx.ResourceData[attrName]; ok {
				return val
			}
		case "environment":
			if val, ok := ctx.Environment[attrName]; ok {
				return val
			}
		}

		return match
	})
}

// hasUnresolvedPlaceholders checks if a string still contains placeholders that couldn't be resolved
func hasUnresolvedPlaceholders(value string) bool {
	re := regexp.MustCompile(`\$\{[^}]+\}`)
	return re.MatchString(value)
}

// extractUnresolvedPlaceholders returns a list of unresolved placeholders
func extractUnresolvedPlaceholders(value string) []string {
	re := regexp.MustCompile(`\$\{[^}]+\}`)
	return re.FindAllString(value, -1)
}

// compare evaluates comparison operators between actual and expected values
// Note: "=" and "!=" are case-sensitive, while IN/CONTAINS/STARTS_WITH/ENDS_WITH are case-insensitive
func compare(actual, expected, operator string) bool {
	actual = strings.TrimSpace(actual)
	expected = strings.TrimSpace(expected)

	switch operator {
	case "=":
		return actual == expected // case-sensitive

	case "!=":
		return actual != expected // case-sensitive

	case ">":
		return numericCompare(actual, expected, func(a, e float64) bool { return a > e })

	case "<":
		return numericCompare(actual, expected, func(a, e float64) bool { return a < e })

	case ">=":
		return numericCompare(actual, expected, func(a, e float64) bool { return a >= e })

	case "<=":
		return numericCompare(actual, expected, func(a, e float64) bool { return a <= e })

	case "IN":
		return inComparison(actual, expected)

	case "CONTAINS":
		return strings.Contains(strings.ToLower(actual), strings.ToLower(expected))

	case "STARTS_WITH":
		return strings.HasPrefix(strings.ToLower(actual), strings.ToLower(expected))

	case "ENDS_WITH":
		return strings.HasSuffix(strings.ToLower(actual), strings.ToLower(expected))

	default:
		return false
	}
}

func numericCompare(actual, expected string, compareFn func(float64, float64) bool) bool {
	actualNum, err1 := strconv.ParseFloat(actual, 64)
	expectedNum, err2 := strconv.ParseFloat(expected, 64)

	if err1 != nil || err2 != nil {
		return false
	}

	return compareFn(actualNum, expectedNum)
}

func inComparison(actual, expected string) bool {
	values := strings.Split(expected, ",")
	actual = strings.ToLower(strings.TrimSpace(actual))

	log.Print("IN comparison values: ", values)
	log.Print("Actual value: ", actual)
	log.Print("Expected values: ", expected)
	for _, val := range values {
		if strings.ToLower(strings.TrimSpace(val)) == actual {
			return true
		}
	}

	return false
}

func evaluatePolicy(policyAttribute models.PolicyAttribute, ctx *models.AuthorizationContext) (bool, string) {
	var actualValue string
	var exists bool

	log.Print("Attribute Type: ", policyAttribute.AttributeType)

	switch policyAttribute.AttributeType {
	case "user":
		log.Print("Fetching from User Attributes")
		log.Print("User Attributes: ", ctx.UserAttributes)
		actualValue, exists = ctx.UserAttributes[policyAttribute.AttributeName]
		if !exists {
			return false, fmt.Sprintf("User attribute '%s' not found", policyAttribute.AttributeName)
		}
		log.Print("Found User Attribute: ", actualValue)
	case "resource":
		actualValue, exists = ctx.ResourceData[policyAttribute.AttributeName]
		if !exists {
			return false, fmt.Sprintf("Resource attribute '%s' not found", policyAttribute.AttributeName)
		}

	case "environment":
		actualValue, exists = ctx.Environment[policyAttribute.AttributeName]
		if !exists {
			return false, fmt.Sprintf("Environment attribute '%s' not found", policyAttribute.AttributeName)
		}

	default:
		return false, fmt.Sprintf("Unknown attribute type: %s", policyAttribute.AttributeType)
	}

	expectedValue := resolveVariables(policyAttribute.AttributeValue, ctx)

	fmt.Printf("[POLICY EVALUATION] Type: %s, Attribute: %s\n", policyAttribute.AttributeType, policyAttribute.AttributeName)
	fmt.Printf("  Expected: %s %s %s\n", policyAttribute.AttributeName, policyAttribute.Comparison, expectedValue)
	fmt.Printf("  Actual:   %s = %s\n", policyAttribute.AttributeName, actualValue)

	log.Print("Comparison: ", policyAttribute.Comparison)
	satisfied := compare(actualValue, expectedValue, policyAttribute.Comparison)

	if !satisfied {
		fmt.Printf("  Result:   ❌ FAILED\n\n")

		// Check if the failure is due to unresolved placeholders
		if hasUnresolvedPlaceholders(expectedValue) {
			unresolvedPlaceholders := extractUnresolvedPlaceholders(expectedValue)
			return false, fmt.Sprintf(
				"Policy failed: %s %s %s (actual: %s) - Missing required attributes: %v",
				policyAttribute.AttributeName,
				policyAttribute.Comparison,
				expectedValue,
				actualValue,
				unresolvedPlaceholders,
			)
		}

		return false, fmt.Sprintf(
			"Policy failed: %s %s %s (actual: %s)",
			policyAttribute.AttributeName,
			policyAttribute.Comparison,
			expectedValue,
			actualValue,
		)
	}

	fmt.Printf("  Result:   ✔️ PASSED\n\n")
	return true, ""
}

func EvaluatePolicies(policies []models.PolicyAttribute, ctx *models.AuthorizationContext) (bool, string) {
	if len(policies) == 0 {
		// No policies means permission is granted by default (RBAC only)
		return true, "No policies to evaluate"
	}

	for _, policy := range policies {
		satisfied, reason := evaluatePolicy(policy, ctx)
		if !satisfied {
			return false, reason
		}
	}

	return true, "All policies satisfied"
}