Start Skohub provider (#29)

providers/skohub.js

@@ -0,0 +1,151 @@
+const BaseProvider = require("./base-provider")
+const _ = require("../utils/lodash")
+const errors = require("../errors")
+
+/**
+ * ```json
+ * {
+ *  "uri": "http://coli-conc.gbv.de/registry/skohub.io",
+ *  "provider": "Skohub",
+ *  "schemes": [
+ *    {
+ *      "uri": "https://w3id.org/class/esc/scheme",
+ *    }
+ *  ]
+ * }
+ */
+class SkohubProvider extends BaseProvider {
+
+  _setup() {
+    this._jskos.schemes = this.schemes || []
+  }
+
+  async getSchemes({ ...config }) {
+    const { schemes } = this._jskos
+
+    for (let i=0; i<schemes.length; i++) {
+      schemes[i] = await this._loadScheme(schemes[i], config)
+    }
+
+    return schemes
+  }
+
+  async _loadScheme(scheme, config) {
+    const { uri, topConcepts } = scheme
+
+    if (!uri || topConcepts) {
+      return scheme
+    }
+
+    const data = await this.axios({ ...config, url: `${uri}.json` })
+
+    // TODO: if not found
+
+    if (data.id !== uri) {
+      throw new errors.InvalidRequestError({ message: "Skohub URL did not return expected concept scheme" })
+    }
+
+    const { title } = data //, description, issued, created, modified, creator, publisher } = data
+    const { preferredNamespaceUri } = data //, preferredNamespacePrefix, isBasedOn, source } = data
+    const { hasTopConcept } = data
+
+    scheme.prefLabel = title
+    scheme.namespace = preferredNamespaceUri
+    scheme.topConcepts = (hasTopConcept || []).map(c => this._mapConcept(c))
+
+    const hasNarrower = scheme.topConcepts.find(c => c.narrower && c.narrower.length)
+
+    scheme.concepts = [...scheme.topConcepts]
+    if (hasNarrower) {
+      scheme.concepts.push(null)
+    }
+
+    // TODO: map remaining fields
+
+    // remove fields without value
+    for (let key of Object.keys(scheme).filter(key => !scheme[key])) {
+      delete scheme[key]
+    }
+
+    return scheme
+  }
+
+  async getTop({ scheme, ...config }) {
+    if (!scheme || !scheme.uri) {
+      throw new errors.InvalidOrMissingParameterError({ parameter: "scheme", message: "Missing scheme URI" })
+    }
+
+    scheme = this._jskos.schemes.find(s => s.uri === scheme.uri)
+    if (scheme) {
+      scheme = await this._loadScheme(scheme, config)
+      return scheme.topConcepts
+    } else {
+      return []
+    }
+  }
+
+  async getConcepts({ concepts, ...config }) {
+    if (!_.isArray(concepts)) {
+      concepts = [concepts]
+    }
+    concepts = concepts.map(c => ({ uri: c.uri, inScheme: c.inScheme }))
+
+    const newConcepts = []
+    for (let concept of concepts) {
+      const { uri, inScheme } = concept
+
+      if (!(inScheme && inScheme[0] && inScheme[0].uri)) {
+        throw new errors.InvalidOrMissingParameterError({ parameter: "inScheme", message: "Missing inScheme URI" })
+      }
+
+      var scheme = this._jskos.schemes.find(s => s.uri === inScheme[0].uri)
+      if (scheme) {
+        scheme = await this._loadScheme(scheme, config)
+      }
+      if (!scheme) {
+        continue
+      }
+
+      const found = scheme.concepts.find(c => (c && c.uri === uri))
+
+      if (found) {
+        newConcepts.push(found)
+      } else if (_.last(scheme.concepts) === null) {
+        const loaded = await this._loadConcept(uri)
+        if (loaded) {
+          newConcepts.push(loaded)
+          // TODO: add it to scheme.concepts (caching)
+        }
+      }
+    }
+
+    return newConcepts
+  }
+
+  async _loadConcept(uri, config) {
+    const data = await this.axios({ ...config, url: `${uri}.json` })
+
+    // TODO: if not found
+
+    if (data.id !== uri) {
+      throw new errors.InvalidRequestError({ message: "Skohub URL did not return expected concept URI" })
+    }
+
+    return this._mapConcept(data)
+  }
+
+  _mapConcept(data) {
+    const concept = { uri: data.id }
+
+    concept.prefLabel = data.prefLabel
+    concept.narrower = (data.narrower || []).map(c => this._mapConcept(c))
+
+    // TODO: convert to JSKOS
+
+    return concept 
+  }
+}
+
+SkohubProvider.providerName = "Skohub"
+
+module.exports = SkohubProvider