import { testRun, expectErrorToBeBounded, SqValueTag } from "./TestHelpers";
import * as fc from "fast-check";

describe("Mean of mixture is weighted average of means", () => {
  test.skip("mx(beta(a,b), lognormal(m,s), [x,y])", () => {
    fc.assert(
      fc.property(
        fc.float({ min: 1e-1 }), // alpha
        fc.float({ min: 1 }), // beta
        fc.float(), // mu
        fc.float({ min: 1e-1 }), // sigma
        fc.float({ min: 1e-7 }),
        fc.float({ min: 1e-7 }),
        (a, b, m, s, x, y) => {
          let squiggleString = `mean(mixture(beta(${a},${b}), lognormal(${m},${s}), [${x}, ${y}]))`;
          let res = testRun(squiggleString);
          let weightDenom = x + y;
          let betaWeight = x / weightDenom;
          let lognormalWeight = y / weightDenom;
          let betaMean = 1 / (1 + b / a);
          let lognormalMean = m + s ** 2 / 2;
          if (res.tag === SqValueTag.Number) {
            expectErrorToBeBounded(
              res.value,
              betaWeight * betaMean + lognormalWeight * lognormalMean,
              1,
              2
            );
          } else {
            expect(res.value).toEqual("some error message");
          }
        }
      )
    );
  });
});