import mongoose from "mongoose";

type ParsedQuery = Array<
  Record<
    string,
    Record<"$eq" | "$neq" | "$in" | "$nin", string | Date | Object>
  >
>;

function convertValue(value: any) {
  if (mongoose.Types.ObjectId.isValid(value)) {
    return mongoose.Types.ObjectId.createFromHexString(value);
  } else if (
    !isNaN(parseInt(value)) &&
    parseInt(value).toString().length == value.toString().length
  ) {
    return parseInt(value);
  } else if (!isNaN(Date.parse(value))) {
    return new Date(value);
  } else {
    return value;
  }
}

export function parse(query: string, validFields: Array<string>): ParsedQuery {
  const result = [];

  let currentStage = "field";
  let token = "";
  let field = "";
  let op = "";
  let value = "";
  let valueArr = [];
  for (let i = 0; i < query.length; i++) {
    let char = query[i];

    if (currentStage === "field") {
      if (char === "=" || char === "!") {
        field = token;
        token = "";
        currentStage = "value";

        if (char === "=") {
          op = "$eq";
        } else {
          op = "$neq";
          i++;
        }

        continue;
      }

      token += char;
    }

    if (currentStage === "value") {
      if (char === "[") {
        currentStage = "valueArr";
        continue;
      }

      if (char === "," || i == query.length - 1) {
        if (i == query.length - 1) token += char;

        value = token;
        result.push({ [field]: { [op]: convertValue(value) } });

        token = "";
        field = "";
        op = "";

        currentStage = "field";

        continue;
      }

      token += char;
    }

    if (currentStage === "valueArr") {
      if (char === ",") {
        valueArr.push(convertValue(token));
        token = "";
        continue;
      }

      if (char === "]") {
        valueArr.push(token);
        result.push({
          [field]: { [op === "$eq" ? "$in" : "$nin"]: valueArr },
        });

        token = "";
        field = "";
        op = "";
        valueArr = [];

        currentStage = "field";
        i++;

        continue;
      }

      token += char;
    }
  }

  return result;
}