fix(components): gs-mutation-filter: allow for reference genome with …

…no genes

components/src/preact/mutationFilter/ExampleMutation.tsx

@@ -0,0 +1,68 @@
+import { useContext } from 'preact/hooks';
+import type { FC } from 'react';
+
+import { type ReferenceGenome } from '../../lapisApi/ReferenceGenome';
+import type { SequenceType } from '../../types';
+import { ReferenceGenomeContext } from '../ReferenceGenomeContext';
+
+type ExampleMutationProps = {
+    sequenceType: SequenceType;
+    mutationType: 'substitution' | 'insertion';
+};
+
+export const ExampleMutation: FC<ExampleMutationProps> = ({ sequenceType, mutationType }) => {
+    const referenceGenome = useContext(ReferenceGenomeContext);
+
+    return <b>{getExampleMutation(referenceGenome, sequenceType, mutationType)}</b>;
+};
+
+export function getExampleMutation(
+    referenceGenome: ReferenceGenome,
+    sequenceType: SequenceType,
+    mutationType: 'substitution' | 'insertion',
+) {
+    switch (sequenceType) {
+        case 'amino acid': {
+            if (referenceGenome.genes.length === 0) {
+                return '';
+            }
+
+            const firstGene = referenceGenome.genes[0].name;
+
+            switch (mutationType) {
+                case 'substitution':
+                    return `${firstGene}:57Q`;
+                case 'insertion':
+                    return `ins_${firstGene}:31:N`;
+            }
+        }
+        // Issue of linter https://github.com/typescript-eslint/typescript-eslint/issues/3455
+        // eslint-disable-next-line no-fallthrough
+        case 'nucleotide': {
+            switch (referenceGenome.nucleotideSequences.length) {
+                case 0: {
+                    return '';
+                }
+                case 1: {
+                    switch (mutationType) {
+                        case 'substitution':
+                            return '23T';
+                        case 'insertion':
+                            return 'ins_1046:A';
+                    }
+                }
+                // Issue of linter https://github.com/typescript-eslint/typescript-eslint/issues/3455
+                // eslint-disable-next-line no-fallthrough
+                default: {
+                    const firstSegment = referenceGenome.nucleotideSequences[0].name;
+                    switch (mutationType) {
+                        case 'substitution':
+                            return `${firstSegment}:23T`;
+                        case 'insertion':
+                            return `ins_${firstSegment}:10462:A`;
+                    }
+                }
+            }
+        }
+    }
+}