1 files changed, 80 insertions, 0 deletions

diff --git a/subprojects/frontend/src/editor/exposeDiagnostics.ts b/subprojects/frontend/src/editor/exposeDiagnostics.ts
new file mode 100644
index 00000000..82f24c93
--- /dev/null
+++ b/subprojects/frontend/src/editor/exposeDiagnostics.ts
@@ -0,0 +1,80 @@
+import { setDiagnosticsEffect } from '@codemirror/lint';
+import {
+  StateField,
+  RangeSet,
+  type Extension,
+  type EditorState,
+} from '@codemirror/state';
+
+import DiagnosticValue, { type Severity } from './DiagnosticValue';
+
+type SeverityCounts = Partial<Record<Severity, number>>;
+
+interface ExposedDiagnostics {
+  readonly diagnostics: RangeSet<DiagnosticValue>;
+
+  readonly severityCounts: SeverityCounts;
+}
+
+function countSeverities(
+  diagnostics: RangeSet<DiagnosticValue>,
+): SeverityCounts {
+  const severityCounts: SeverityCounts = {};
+  const iter = diagnostics.iter();
+  while (iter.value !== null) {
+    const {
+      value: { severity },
+    } = iter;
+    severityCounts[severity] = (severityCounts[severity] ?? 0) + 1;
+    iter.next();
+  }
+  return severityCounts;
+}
+
+const exposedDiagnosticsState = StateField.define<ExposedDiagnostics>({
+  create() {
+    return {
+      diagnostics: RangeSet.of([]),
+      severityCounts: {},
+    };
+  },
+
+  update({ diagnostics: diagnosticsSet, severityCounts }, transaction) {
+    let newDiagnosticsSet = diagnosticsSet;
+    if (transaction.docChanged) {
+      newDiagnosticsSet = newDiagnosticsSet.map(transaction.changes);
+    }
+    transaction.effects.forEach((effect) => {
+      if (effect.is(setDiagnosticsEffect)) {
+        const diagnostics = effect.value.map(({ severity, from, to }) =>
+          DiagnosticValue.VALUES[severity].range(from, to),
+        );
+        diagnostics.sort(({ from: a }, { from: b }) => a - b);
+        newDiagnosticsSet = RangeSet.of(diagnostics);
+      }
+    });
+    return {
+      diagnostics: newDiagnosticsSet,
+      severityCounts:
+        // Only recompute if the diagnostics were changed.
+        diagnosticsSet === newDiagnosticsSet
+          ? severityCounts
+          : countSeverities(newDiagnosticsSet),
+    };
+  },
+});
+
+const exposeDiagnostics: Extension = [exposedDiagnosticsState];
+
+export default exposeDiagnostics;
+
+export function getDiagnostics(state: EditorState): RangeSet<DiagnosticValue> {
+  return state.field(exposedDiagnosticsState).diagnostics;
+}
+
+export function countDiagnostics(
+  state: EditorState,
+  severity: Severity,
+): number {
+  return state.field(exposedDiagnosticsState).severityCounts[severity] ?? 0;
+}