import "core-js/stable/array/fill.js";
import faker from "faker";
import { VNode } from "../../package/vnode";
import { h } from "../../package/h";
import { init as curInit } from "../../package/init";
import { init as refInit } from "latest-snabbdom-release/init";
import { assert } from "chai";
import pReduce from "p-reduce";
import pMapSeries from "p-map-series";
import { std, mean } from "mathjs";

const RUNS = 5;
const PATCHES_PER_RUN = 100;
const WARM_UP_RUNS = 1;
const REQUEST_ANIMATION_FRAME_EVERY_N_PATCHES = 1;
const BENCHMARK_TIMEOUT_MINUTES = 10;
const REQUIRED_PRECISION = 0.02;

/* eslint-disable @typescript-eslint/no-unused-vars */
declare global {
  // eslint-disable-next-line @typescript-eslint/naming-convention
  const __karma__: {
    info(info: unknown): void;
  };
}
/* eslint-enable @typescript-eslint/no-unused-vars */

const ALLOWED_REGRESSION = 0.03;
describe("core benchmark", () => {
  it("does not regress", async function Benchmark() {
    this.timeout(BENCHMARK_TIMEOUT_MINUTES * 1000 * 60);

    faker.seed(0);
    const inputs = Array(PATCHES_PER_RUN)
      .fill(null)
      .map(() => {
        return new Array(faker.random.number(20)).fill(null).map(() => ({
          name: faker.company.companyName(),
          catchPhrase: faker.company.catchPhrase(),
          suffix: faker.company.companySuffix(),
          products: Array(faker.random.number(3))
            .fill(null)
            .map(() => ({
              name: faker.commerce.productName(),
              color: faker.commerce.color(),
              price: faker.commerce.price() + faker.finance.currencySymbol(),
            })),
          founded: faker.date.past(),
        }));
      });

    type Input = typeof inputs[0];

    const view = (companies: Input): VNode =>
      h("table", [
        h("caption", ["Companies"]),
        h("thead", [
          h(
            "tr",
            ["Details", "Products"].map((th) => h("th", [th]))
          ),
        ]),
        h(
          "tbody",
          companies.map(function companyView(company) {
            return h("tr", [
              h("td", [
                h("div", [
                  h("b", [company.name]),
                  company.suffix && `\xa0${company.suffix}`,
                ]),
                h("div", h("i", [company.catchPhrase])),
                h("td", [
                  h("dt", ["Founded"]),
                  h("dd", [company.founded.toLocaleDateString()]),
                ]),
              ]),
              h("td", [
                h(
                  "ul",
                  company.products.map(function productView(product) {
                    return h("li", [
                      h("dl", [
                        h("dt", ["Name"]),
                        h("dd", [product.name]),
                        h("dt", ["Color"]),
                        h("dd", [product.color]),
                        h("dt", ["Price"]),
                        h("dd", [product.price]),
                      ]),
                    ]);
                  })
                ),
              ]),
            ]);
          })
        ),
      ]);

    type Patcher = ReturnType<typeof refInit | typeof curInit>;

    interface SingleRunResult {
      i: number;
      cur: number;
      ref: number;
    }

    const subjectToResult = async (
      subject: Patcher,
      subjectId: string
    ): Promise<number> => {
      await new Promise((resolve) => {
        requestAnimationFrame(resolve);
      });
      const markName = `mark:${subjectId}`;
      const measureName = `measure:${subjectId}`;
      performance.mark(markName);
      const lastVnode = await pReduce(
        inputs,
        async function subjectToResultReducer(
          acc: HTMLElement | VNode,
          input,
          i
        ) {
          const vnode = view(input);
          subject(acc, vnode);
          if (i % REQUEST_ANIMATION_FRAME_EVERY_N_PATCHES === 0) {
            await new Promise((resolve) => {
              requestAnimationFrame(resolve);
            });
          }
          return vnode;
        },
        document.body.appendChild(document.createElement("section"))
      );
      performance.measure(measureName, markName);
      if (!("elm" in lastVnode)) throw new Error();
      if (!lastVnode.elm) throw new Error();
      document.body.removeChild(lastVnode.elm);
      const measure = performance.getEntriesByName(measureName)[0];
      performance.clearMarks(markName);
      performance.clearMeasures(measureName);
      return measure.duration;
    };

    const singleRun = async (
      _: null,
      runI: number
    ): Promise<SingleRunResult> => {
      const cur = await subjectToResult(curInit([]), `cur:${runI}`);
      const ref = await subjectToResult(refInit([]), `ref:${runI}`);

      return { i: runI, cur, ref };
    };

    const runResults = (
      await pMapSeries(Array(RUNS + WARM_UP_RUNS).fill(null), singleRun)
    ).slice(WARM_UP_RUNS);

    __karma__.info({ benchmark: runResults });

    const results = {
      ref: runResults.map((result) => result.ref),
      cur: runResults.map((result) => result.cur),
    };
    const means = {
      ref: mean(results.ref),
      cur: mean(results.cur),
    };
    const stds = {
      ref: std(results.ref, "uncorrected"),
      cur: std(results.cur, "uncorrected"),
    };

    (["ref", "cur"] as const).forEach((subject) => {
      const stdRatio = stds[subject] / means[subject];
      assert.isAtMost(
        stdRatio,
        REQUIRED_PRECISION,
        `${subject} not precise enough`
      );
    });

    assert.isAtMost(means.cur, means.ref * (1 + ALLOWED_REGRESSION));
  });
});