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map.js
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map.js
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import rdf from 'rdf-ext'
import { Transform } from 'readable-stream'
function mapDataset (map, { factory = rdf } = {}) {
const mapper = mapQuad(map, { factory })
return dataset => {
return factory.dataset([...dataset].map(quad => mapper(quad)))
}
}
function mapQuad (map, { factory = rdf } = {}) {
const mapper = mapTerm(map, { factory })
return quad => {
const subject = mapper(quad.subject)
const predicate = mapper(quad.predicate)
const object = mapper(quad.object)
const graph = mapper(quad.graph)
if (subject === quad.subject && predicate === quad.predicate && object === quad.object && graph === quad.graph) {
return quad
}
return factory.quad(subject, predicate, object, graph)
}
}
function mapStream (map, { factory = rdf } = {}) {
const mapper = mapQuad(map, { factory })
return new Transform({
objectMode: true,
transform (quad, encoding, callback) {
callback(null, mapper(quad))
}
})
}
function mapTerm (map, { factory = rdf } = {}) {
return term => {
if (!term) {
return term
}
if (term.termType !== 'NamedNode') {
return term
}
for (const [from, to] of map) {
const fromStr = from.value || from.toString()
if (term.value.startsWith(fromStr)) {
const toStr = to.value || to.toString()
return factory.namedNode(toStr + term.value.slice(fromStr.length))
}
}
return term
}
}
export {
mapDataset,
mapQuad,
mapStream,
mapTerm
}