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import type { Context, RDF } from "../rdf.ts";import type { Property, Schema } from "../schema/mod.ts";import { encode } from "../encoder.ts";import type { Entity } from "./types.ts";
export class QueryHelper {  private readonly entity: Entity;  private readonly schema: Schema;  private readonly context: Context;  private readonly variableInitCounter: number;
  private quads?: RDF.Quad[];  private variableQuads?: RDF.Quad[];
  constructor(    entity: Entity,    schema: Schema,    context: Context,    variableInitCounter = 0,  ) {    this.entity = entity;    this.schema = schema;    this.context = context;    this.variableInitCounter = variableInitCounter;  }
  getQuads() {    if (!this.quads) {      this.quads = encode(        this.entity,        this.schema,        this.context,        this.variableInitCounter,      );    }    return this.quads;  }
  getVariableQuads() {    if (!this.variableQuads) {      this.variableQuads = encode(        this.getEntityWithReplacedVariables(),        this.schema,        this.context,        this.variableInitCounter,      );    }    return this.variableQuads;  }
  getDeleteQuads() {    return this.getVariableQuads().filter(      (quad) => quad.object.termType === "Variable",    );  }
  getInsertQuads() {    return this.getQuads();  }
  getWhereQuads() {    return this.getVariableQuads();  }
  private getEntityWithReplacedVariables() {    return this.replaceVariables(this.entity, this.schema);  }
  private replaceVariables(entity: Entity, schema: Schema) {    return Object.keys(entity).reduce((output, key) => {      const value = entity[key];
      if (key === "$id") {        output.$id = value as string;        return output;      }      if (key === "$type") {        output.$type = value;        return output;      }
      const property = schema[key] as Property;      if (!property) {        throw new Error("Unknown field '${key}' detected in entity");      }
      if (!property["@context"]) {        output[key] = null;        return output;      }
      if (property["@array"]) {        if ((value as Entity[]).length === 0) {          output[key] = null;        } else {          output[key] = (value as Entity[]).map((subEntity) =>            this.replaceVariables(subEntity, property["@context"]!)          );        }      } else {        output[key] = this.replaceVariables(          value as Entity,          property["@context"],        );      }
      return output;    }, {} as Entity);  }}