From 036b4e773c1f7b2ef16d28fc668c2bfe609ae1c4 Mon Sep 17 00:00:00 2001
From: Kristóf Marussy <kristof@marussy.com>
Date: Thu, 4 Nov 2021 20:38:44 +0100
Subject: feat(lang): add example validation checks

---
 .../ProblemCrossrefProposalProvider.java           |  4 +-
 .../language/resource/ReferenceCounter.java        | 10 ++++-
 .../language/validation/ProblemValidator.java      | 49 ++++++++++++++++++++++
 3 files changed, 59 insertions(+), 4 deletions(-)

diff --git a/language-ide/src/main/java/tools/refinery/language/ide/contentassist/ProblemCrossrefProposalProvider.java b/language-ide/src/main/java/tools/refinery/language/ide/contentassist/ProblemCrossrefProposalProvider.java
index 416535ce..f828e836 100644
--- a/language-ide/src/main/java/tools/refinery/language/ide/contentassist/ProblemCrossrefProposalProvider.java
+++ b/language-ide/src/main/java/tools/refinery/language/ide/contentassist/ProblemCrossrefProposalProvider.java
@@ -50,9 +50,7 @@ public class ProblemCrossrefProposalProvider extends IdeCrossrefProposalProvider
 			return true;
 		}
 		if (rootModel instanceof Problem problem) {
-			var referenceCounts = referenceCounter.getReferenceCounts(problem);
-			var count = referenceCounts.get(eObject);
-			return count != null && count >= 2;
+			return referenceCounter.countReferences(problem, eObject) >= 2;
 		}
 		return true;
 	}
diff --git a/language/src/main/java/tools/refinery/language/resource/ReferenceCounter.java b/language/src/main/java/tools/refinery/language/resource/ReferenceCounter.java
index 56186bc9..7525dfc6 100644
--- a/language/src/main/java/tools/refinery/language/resource/ReferenceCounter.java
+++ b/language/src/main/java/tools/refinery/language/resource/ReferenceCounter.java
@@ -16,7 +16,15 @@ public class ReferenceCounter {
 	@Inject
 	private IResourceScopeCache cache;
 
-	public Map<EObject, Integer> getReferenceCounts(Problem problem) {
+	public int countReferences(Problem problem, EObject eObject) {
+		var count = getReferenceCounts(problem).get(eObject);
+		if (count == null) {
+			return 0;
+		}
+		return count;
+	}
+
+	protected Map<EObject, Integer> getReferenceCounts(Problem problem) {
 		var resource = problem.eResource();
 		if (resource == null) {
 			return doGetReferenceCounts(problem);
diff --git a/language/src/main/java/tools/refinery/language/validation/ProblemValidator.java b/language/src/main/java/tools/refinery/language/validation/ProblemValidator.java
index f2378df6..dfd386f5 100644
--- a/language/src/main/java/tools/refinery/language/validation/ProblemValidator.java
+++ b/language/src/main/java/tools/refinery/language/validation/ProblemValidator.java
@@ -3,6 +3,19 @@
  */
 package tools.refinery.language.validation;
 
+import org.eclipse.xtext.EcoreUtil2;
+import org.eclipse.xtext.validation.Check;
+
+import com.google.inject.Inject;
+
+import tools.refinery.language.model.ProblemUtil;
+import tools.refinery.language.model.problem.Node;
+import tools.refinery.language.model.problem.Problem;
+import tools.refinery.language.model.problem.ProblemPackage;
+import tools.refinery.language.model.problem.Variable;
+import tools.refinery.language.model.problem.VariableOrNodeArgument;
+import tools.refinery.language.resource.ReferenceCounter;
+
 /**
  * This class contains custom validation rules.
  *
@@ -10,4 +23,40 @@ package tools.refinery.language.validation;
  * https://www.eclipse.org/Xtext/documentation/303_runtime_concepts.html#validation
  */
 public class ProblemValidator extends AbstractProblemValidator {
+	private static final String ISSUE_PREFIX = "tools.refinery.language.validation.ProblemValidator.";
+
+	public static final String SINGLETON_VARIABLE_ISSUE = ISSUE_PREFIX + "SINGLETON_VARIABLE";
+
+	public static final String NON_UNIQUE_NODE_ISSUE = ISSUE_PREFIX + "NON_UNIQUE_NODE";
+
+	@Inject
+	private ReferenceCounter referenceCounter;
+
+	@Check
+	public void checkUniqueVariable(VariableOrNodeArgument argument) {
+		var variableOrNode = argument.getVariableOrNode();
+		if (variableOrNode instanceof Variable variable && ProblemUtil.isImplicitVariable(variable)
+				&& !ProblemUtil.isSingletonVariable(variable)) {
+			var problem = EcoreUtil2.getContainerOfType(variable, Problem.class);
+			if (problem != null && referenceCounter.countReferences(problem, variable) <= 1) {
+				var name = variable.getName();
+				var message = "Variable '%s' has only a single reference. Add another reference or mark is as a singleton variable: '_%s'"
+						.formatted(name, name);
+				warning(message, argument, ProblemPackage.Literals.VARIABLE_OR_NODE_ARGUMENT__VARIABLE_OR_NODE,
+						INSIGNIFICANT_INDEX, SINGLETON_VARIABLE_ISSUE);
+			}
+		}
+	}
+
+	@Check
+	public void checkNonUniqueNode(VariableOrNodeArgument argument) {
+		var variableOrNode = argument.getVariableOrNode();
+		if (variableOrNode instanceof Node node && !ProblemUtil.isUniqueNode(node)) {
+			var name = node.getName();
+			var message = "Only unique nodes can be referenced in predicates. Mark '%s' as unique with the declaration 'unique %s.'"
+					.formatted(name, name);
+			error(message, argument, ProblemPackage.Literals.VARIABLE_OR_NODE_ARGUMENT__VARIABLE_OR_NODE,
+					INSIGNIFICANT_INDEX, NON_UNIQUE_NODE_ISSUE);
+		}
+	}
 }
-- 
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