// BAA stands for Before Around After

import { getQuery, type H3Event } from "h3";
import { type QueryObject } from "ufo";

import { isString } from "./isString";

import { createError } from "#imports";

type queryType<none extends boolean = boolean> = none extends false ? {
  type: "before" | "after" | "around",
  id: bigint
} : {
  type: null
};

export type pageData<none extends boolean = boolean> = queryType<none> & { count: number }

/**
 * Gets queryType for a given query with a value
 * @param query the query to parse
 * @throws if query malformed (multiple before/after/around)
 */
function getLocationParameterType(query: QueryObject): queryType {
  const before = query.before;
  const after = query.after;
  const around = query.around;

  let setLocationParametersCount = 0;
  let rvalue: queryType = { type: null };

  if (isString(before)) {
    setLocationParametersCount++;
    rvalue = { type: "before", id: BigInt(before) };
  }

  if (isString(after)) {
    setLocationParametersCount++;
    rvalue = { type: "after", id: BigInt(after) };
  }

  if (isString(around)) {
    setLocationParametersCount++;
    rvalue = { type: "around", id: BigInt(around) };
  }

  if (setLocationParametersCount > 1) {
    throw createError({
      statusCode: 400,
      message: "multiple location parameters not allowed",
    });
  }

  return rvalue;
}

/** Gets the count parameter from the query object.
 * @param query the query to check.
 * @param defaultCount the default count if the query doesn't have count parameter. (default 50)
 * @param countLimit the maximum count of the parameter before throwing. (default 200)
 * @returns the value of count parameter.
 * @throws if the parameter in query exceeds provided countLimit.
 */
function getRequestedCount(
  query: QueryObject,
  defaultCount = 50,
  countLimit = 200,
) {
  let count = defaultCount;
  if (query.limit) count = Number(query.limit);

  if (count > countLimit) {
    throw createError({
      statusCode: 400,
      message: `Cannot retrieve more than ${countLimit} records`,
    });
  }
  if (count <= 0) {
    throw createError({
      statusCode: 400,
      message: "Tried to retireve 0 or less records",
    });
  }

  return count;
}

/** Gets the baa page parameters from the H3event,
 * @param e the H3event to fetch parameters.
 * @param defaultCount the default count to use if there is no count parameter. (default 50)
 * @param countLimit the maximum value of the count parameter before throwing an error. (default 200)
 * @returns the page data found in the query.
 * @throws if event has a count parameter in the query that exceed provided countLimit.
 */
export default function getPaginatedParameters(
  e: H3Event,
  defaultCount = 50,
  countLimit = 200,
): pageData {
  const query = getQuery(e);
  const queryParameters = getLocationParameterType(query);
  const queryCount = getRequestedCount(query, defaultCount, countLimit);

  return {
    ...queryParameters,
    count: queryCount,
  };
}