@jahed/sparql-engine/dist/formatters/json-formatter.js

SPARQL query engine for servers and web browsers.

// SPDX-License-Identifier: MIT
import { isBoolean } from "lodash-es";
import { Pipeline } from "../engine/pipeline/pipeline.js";
import { BindingBase, Bindings } from "../rdf/bindings.js";
import { termIsBNode, termIsIRI, termIsLiteral } from "../utils/rdf.js";
/**
 * Write the JSON headers
 * @private
 * @param bindings - Input bindings
 * @param input - Output where to write results
 */
function writeHead(bindings, input) {
    const variables = Array.from(bindings.variables())
        .map((v) => (v.startsWith("?") ? `"${v.substring(1)}"` : `"${v}"`))
        .join(",");
    input.next(`"head":{"vars": [${variables}]}`);
}
/**
 * Write a set of bindings as JSON
 * @private
 * @param bindings - Input bindings
 * @param input - Output where to write results
 */
function writeBindings(bindings, input) {
    let cpt = 0;
    bindings.forEach((variable, value) => {
        if (cpt >= 1) {
            input.next(",");
        }
        input.next(`"${variable}":`);
        const term = value;
        if (termIsIRI(term)) {
            input.next(`{"type":"uri","value":"${term.value}"}`);
        }
        else if (termIsBNode(term)) {
            input.next(`{"type":"bnode","value":"${term.value}"}`);
        }
        else if (termIsLiteral(term)) {
            if (term.language.length > 0) {
                input.next(`{"type":"literal","value":"${term.value}","xml:lang":"${term.language}"}`);
            }
            else if (term.datatype) {
                input.next(`{"type":"literal","value":"${term.value}","datatype":"${term.datatype.value}"}`);
            }
            else {
                input.next(`{"type":"literal","value":"${term.value}"}`);
            }
        }
        else {
            input.error(`Invalid RDF term "${value}" encountered during JSON serialization`);
        }
        cpt++;
    });
}
/**
 * Formats query solutions (bindings or booleans) from a PipelineStage in W3C SPARQL JSON format
 * @see https://www.w3.org/TR/2013/REC-sparql11-results-json-20130321/
 * @param source - Input pipeline
 * @return A pipeline that yields results in W3C SPARQL JSON format
 */
export default function jsonFormat(source) {
    return Pipeline.getInstance().fromAsync(async (input) => {
        try {
            input.next("{");
            let cpt = 0;
            let isAsk = false;
            for await (const b of source) {
                // Build the head attribute from the first set of bindings
                if (cpt === 0 && b instanceof BindingBase) {
                    writeHead(b, input);
                    input.next(',"results": {"bindings": [');
                }
                else if (cpt === 0 && isBoolean(b)) {
                    isAsk = true;
                    input.next('"boolean":');
                }
                else if (cpt >= 1) {
                    input.next(",");
                }
                // handle results (boolean for ASK queries, bindings for SELECT queries)
                if (isBoolean(b)) {
                    input.next(b ? "true" : "false");
                }
                else if (b instanceof BindingBase) {
                    input.next("{");
                    writeBindings(b, input);
                    input.next("}");
                }
                cpt++;
            }
            input.next(isAsk ? "}" : "]}}");
            input.complete();
        }
        catch (error) {
            console.error(error);
        }
    });
}
//# sourceMappingURL=json-formatter.js.map