feat: Create conditions based on input headers

src/storage/BasicConditions.ts

@@ -0,0 +1,69 @@
+import type { RepresentationMetadata } from '../ldp/representation/RepresentationMetadata';
+import { DC } from '../util/Vocabularies';
+import { getETag } from './Conditions';
+import type { Conditions } from './Conditions';
+
+export interface BasicConditionsOptions {
+  matchesETag?: string[];
+  notMatchesETag?: string[];
+  modifiedSince?: Date;
+  unmodifiedSince?: Date;
+}
+
+/**
+ * Stores all the relevant Conditions values and matches them based on RFC7232.
+ */
+export class BasicConditions implements Conditions {
+  public readonly matchesETag?: string[];
+  public readonly notMatchesETag?: string[];
+  public readonly modifiedSince?: Date;
+  public readonly unmodifiedSince?: Date;
+
+  public constructor(options: BasicConditionsOptions) {
+    this.matchesETag = options.matchesETag;
+    this.notMatchesETag = options.notMatchesETag;
+    this.modifiedSince = options.modifiedSince;
+    this.unmodifiedSince = options.unmodifiedSince;
+  }
+
+  public matchesMetadata(metadata?: RepresentationMetadata): boolean {
+    if (!metadata) {
+      // RFC7232: ...If-Match... If the field-value is "*", the condition is false if the origin server
+      // does not have a current representation for the target resource.
+      return !this.matchesETag?.includes('*');
+    }
+
+    const modified = metadata.get(DC.terms.modified);
+    const modifiedDate = modified ? new Date(modified.value) : undefined;
+    const etag = getETag(metadata);
+    return this.matches(etag, modifiedDate);
+  }
+
+  public matches(eTag?: string, lastModified?: Date): boolean {
+    // RFC7232: ...If-None-Match... If the field-value is "*", the condition is false if the origin server
+    // has a current representation for the target resource.
+    if (this.notMatchesETag?.includes('*')) {
+      return false;
+    }
+
+    if (eTag) {
+      if (this.matchesETag && !this.matchesETag.includes(eTag) && !this.matchesETag.includes('*')) {
+        return false;
+      }
+      if (this.notMatchesETag?.includes(eTag)) {
+        return false;
+      }
+    }
+
+    if (lastModified) {
+      if (this.modifiedSince && lastModified < this.modifiedSince) {
+        return false;
+      }
+      if (this.unmodifiedSince && lastModified > this.unmodifiedSince) {
+        return false;
+      }
+    }
+
+    return true;
+  }
+}