Storage adapter for glenrobson/SimpleAnnotationServer using IIIF V2.

Converts annotations between IIIF V3 WebAnnotation model used internally
and IIIF V2 OpenAnnotation model used by current SimpleAnnotationServer.

src/SimpleAnnotationServerV2Adapter.js

+/** */
+export default class SimpleAnnotationServerV2Adapter {
+  /** */
+  constructor(canvasId, endpointUrl) {
+    this.canvasId = canvasId;
+    this.endpointUrl = endpointUrl;
+  }
+
+  /** */
+  get annotationPageId() {
+    return `${this.endpointUrl}/search?uri=${this.canvasId}`;
+  }
+
+  /** */
+  async create(annotation) {
+    return fetch(`${this.endpointUrl}/create`, {
+      body: JSON.stringify(SimpleAnnotationServerV2Adapter.createV2Anno(annotation)),
+      headers: {
+        Accept: 'application/json',
+        'Content-Type': 'application/json',
+      },
+      method: 'POST',
+    })
+      .then((response) => this.all())
+      .catch(() => this.all());
+  }
+
+  /** */
+  async update(annotation) {
+    return fetch(`${this.endpointUrl}/update`, {
+      body: JSON.stringify(SimpleAnnotationServerV2Adapter.createV2Anno(annotation)),
+      headers: {
+        Accept: 'application/json',
+        'Content-Type': 'application/json',
+      },
+      method: 'POST',
+    })
+      .then((response) => this.all())
+      .catch(() => this.all());
+  }
+
+  /** */
+  async delete(annoId) {
+    return fetch(`${this.endpointUrl}/destroy?uri=${encodeURIComponent(annoId)}`, {
+      headers: {
+        Accept: 'application/json',
+        'Content-Type': 'application/json',
+      },
+      method: 'DELETE',
+    })
+      .then((response) => this.all())
+      .catch(() => this.all());
+  }
+
+  /** */
+  async get(annoId) {
+    // SAS does not have GET for a single annotation
+    const annotationPage = await this.all();
+    if (annotationPage) {
+      return annotationPage.items.find((item) => item.id === annoId);
+    }
+    return null;
+  }
+
+  /** Returns an AnnotationPage with all annotations */
+  async all() {
+    const resp = await fetch(this.annotationPageId);
+    const annos = await resp.json();
+    return this.createAnnotationPage(annos);
+  }
+
+  /** Creates a V2 annotation from a V3 annotation */
+  static createV2Anno(v3anno) {
+    const v2anno = {
+      '@context': 'http://iiif.io/api/presentation/2/context.json',
+      '@type': 'oa:Annotation',
+      motivation: 'oa:commenting',
+      on: {
+        '@type': 'oa:SpecificResource',
+        full: v3anno.target.id,
+      },
+    };
+    // copy id if it is SAS-generated
+    if (v3anno.id && v3anno.id.startsWith('http')) {
+      v2anno['@id'] = v3anno.id;
+    }
+    if (Array.isArray(v3anno.body)) {
+      v2anno.resource = v3anno.body.map((b) => this.createV2AnnoBody(b));
+    } else {
+      v2anno.resource = this.createV2AnnoBody(v3anno.body);
+    }
+    if (v3anno.target.selector) {
+      if (Array.isArray(v3anno.target.selector)) {
+        const selectors = v3anno.target.selector.map((s) => this.createV2AnnoSelector(s));
+        // create choice, assuming two elements and 0 is default
+        v2anno.on.selector = {
+          '@type': 'oa:Choice',
+          default: selectors[0],
+          item: selectors[1],
+        };
+      } else {
+        v2anno.on.selector = this.createV2AnnoSelector(v3anno.target.selector);
+      }
+    }
+    return v2anno;
+  }
+
+  /** */
+  static createV2AnnoBody(v3body) {
+    const v2body = {
+      chars: v3body.value,
+    };
+    if (v3body.purpose === 'tagging') {
+      v2body['@type'] = 'oa:Tag';
+    } else {
+      v2body['@type'] = 'dctypes:Text';
+    }
+    if (v3body.format) {
+      v2body.format = v3body.format;
+    }
+    if (v3body.language) {
+      v2body.language = v3body.language;
+    }
+    return v2body;
+  }
+
+  /** */
+  static createV2AnnoSelector(v3selector) {
+    switch (v3selector.type) {
+      case 'SvgSelector':
+        return {
+          '@type': 'oa:SvgSelector',
+          value: v3selector.value,
+        };
+      case 'FragmentSelector':
+        return {
+          '@type': 'oa:FragmentSelector',
+          value: v3selector.value,
+        };
+      default:
+        return null;
+    }
+  }
+
+  /** Creates an AnnotationPage from a list of V2 annotations */
+  createAnnotationPage(v2annos) {
+    if (Array.isArray(v2annos)) {
+      const v3annos = v2annos.map((a) => SimpleAnnotationServerV2Adapter.createV3Anno(a));
+      return {
+        id: this.annotationPageId,
+        items: v3annos,
+        type: 'AnnotationPage',
+      };
+    }
+    return v2annos;
+  }
+
+  /** Creates a V3 annotation from a V2 annotation */
+  static createV3Anno(v2anno) {
+    const v3anno = {
+      id: v2anno['@id'],
+      motivation: 'commenting',
+      type: 'Annotation',
+    };
+    if (Array.isArray(v2anno.resource)) {
+      v3anno.body = v2anno.resource.map((b) => this.createV3AnnoBody(b));
+    } else {
+      v3anno.body = this.createV3AnnoBody(v2anno.resource);
+    }
+    let v2target = v2anno.on;
+    if (Array.isArray(v2target)) {
+      [v2target] = v2target;
+    }
+    v3anno.target = {
+      id: v2target.full, // should be source, see #25
+      selector: this.createV3AnnoSelector(v2target.selector),
+    };
+    return v3anno;
+  }
+
+  /** */
+  static createV3AnnoBody(v2body) {
+    const v3body = {
+      type: 'TextualBody',
+      value: v2body.chars,
+    };
+    if (v2body.format) {
+      v3body.format = v2body.format;
+    }
+    if (v2body.language) {
+      v3body.language = v2body.language;
+    }
+    if (v2body['@type'] === 'oa:Tag') {
+      v3body.purpose = 'tagging';
+    }
+    return v3body;
+  }
+
+  /** */
+  static createV3AnnoSelector(v2selector) {
+    switch (v2selector['@type']) {
+      case 'oa:SvgSelector':
+        return {
+          type: 'SvgSelector',
+          value: v2selector.value,
+        };
+      case 'oa:FragmentSelector':
+        return {
+          type: 'FragmentSelector',
+          value: v2selector.value,
+        };
+      case 'oa:Choice':
+        /* create alternate selectors */
+        return [
+          this.createV3AnnoSelector(v2selector.default),
+          this.createV3AnnoSelector(v2selector.item),
+        ];
+      default:
+        return null;
+    }
+  }
+}