converter.js

const formatValueForSQL = require("./formatValue");

class Visitor {
  constructor() {
    this.context = {};
  }

  // conditions as an object
  visit(conditions) {
    return Object.entries(conditions)
      .map(([key, val]) => this.visit_pair(key, val))
      .join(" AND ");
  }

  visit_pair(key, val) {
    // handle nil type
    if (val === null || val === undefined) {
      return this.visit_null(key);
    }

    // handle primary type
    if (typeof val === "number" || typeof val === "string") {
      return this.visit_primary(key, val);
    }

    // handle not equal
    if (typeof val === "object" && val.hasOwnProperty("$neq")) {
      return this.visit_neq(key, val["$neq"]);
    }

    // handle condition op
    if (typeof val === "object" && val.hasOwnProperty("$and")) {
      return `(${this.visit_condition(key, "AND", val["$and"])})`;
    }
    if (typeof val === "object" && val.hasOwnProperty("$or")) {
      return `(${this.visit_condition(key, "OR", val["$or"])})`;
    }

    // handle compare op
    if (typeof val === "object" && val.hasOwnProperty("$gt")) {
      return this.visit_compare(key, ">", val["$gt"]);
    }
    if (typeof val === "object" && val.hasOwnProperty("$gte")) {
      return this.visit_compare(key, ">=", val["$gte"]);
    }
    if (typeof val === "object" && val.hasOwnProperty("$lt")) {
      return this.visit_compare(key, "<", val["$lt"]);
    }
    if (typeof val === "object" && val.hasOwnProperty("$lte")) {
      return this.visit_compare(key, "<=", val["$lte"]);
    }

    throw new Error(`Unknown condition pair: ${key}, ${val}`);
  }

  visit_null(key) {
    return `${key} is null`;
  }

  visit_primary(key, val) {
    return `${key} = ${formatValueForSQL(val)}`;
  }

  visit_neq(key, lhs) {
    if (typeof lhs !== "number" && typeof lhs !== "string")
      throw new Error(`Invalid neq lhs: ${lhs}`);
    return `${key} is not ${formatValueForSQL(lhs)}`;
  }

  visit_condition(key, op, conditions) {
    if (!Array.isArray(conditions))
      throw new Error(`\`${op}\` operator must be an array`);
    return conditions
      .map((entry) => this.visit_pair(key, entry))
      .join(` ${op} `);
  }

  visit_compare(key, op, lhs) {
    if (op !== "<" && op !== "<=" && op !== ">" && op != ">=")
      throw new Error(`Invalid compare op: ${op}`);
    if (typeof lhs !== "number" && typeof lhs !== "string")
      throw new Error(`Invalid compare lhs: ${lhs}`);
    return `${key} ${op} ${formatValueForSQL(lhs)}`;
  }
}

let visitor = new Visitor();

let result = visitor.visit({
  created_by: "[email protected]",
  date: "2020-12-18",
  tag: "aaa",
  created_at: {
    $or: [
      {
        $and: [{ $gt: "2020-05-01" }, { $lt: "2020-05-30" }],
      },
      {
        $and: [{ $gt: "2020-09-01" }, { $lt: "2020-09-30" }],
      },
    ],
  },
  completed_at: null,
  foo: {
    $neq: "bar",
  },
});
console.log(result);