'use strict';

const chalk = require('chalk');

const Table = require('cli-table');

function percentChange(prev, current, prevSem, currentSem) {

  const [mean, sd] = calculateMeanAndSdOfRatioFromDeltaMethod(

    prev,

    current,

    prevSem,

    currentSem

  );

  const pctChange = +(mean * 100).toFixed(1);

  const ci95 = +(100 * 1.96 * sd).toFixed(1);

  const ciInfo = ci95 > 0 ? ` +- ${ci95} %` : '';

  const text = `${pctChange > 0 ? '+' : ''}${pctChange} %${ciInfo}`;

  if (pctChange + ci95 < 0) {

    return chalk.green(text);

  } else if (pctChange - ci95 > 0) {

    return chalk.red(text);

  } else {

    // Statistically insignificant.

    return text;

  }

}

function calculateMeanAndSdOfRatioFromDeltaMethod(

  meanControl,

  meanTest,

  semControl,

  semTest

) {

  const mean =

    (meanTest - meanControl) / meanControl -

    (Math.pow(semControl, 2) * meanTest) / Math.pow(meanControl, 3);

  const variance =

    Math.pow(semTest / meanControl, 2) +

    Math.pow(semControl * meanTest, 2) / Math.pow(meanControl, 4);

  return [mean, Math.sqrt(variance)];

}

function addBenchmarkResults(table, localResults, remoteMasterResults) {

  const benchmarks = Object.keys(

    (localResults && localResults.benchmarks) ||

      (remoteMasterResults && remoteMasterResults.benchmarks)

  );

  benchmarks.forEach(benchmark => {

    const rowHeader = [chalk.white.bold(benchmark)];

    if (remoteMasterResults) {

      rowHeader.push(chalk.white.bold('Time'));

    }

    if (localResults) {

      rowHeader.push(chalk.white.bold('Time'));

    }

    if (localResults && remoteMasterResults) {

      rowHeader.push(chalk.white.bold('Diff'));

    }

    table.push(rowHeader);

    const measurements =

      (localResults && localResults.benchmarks[benchmark].averages) ||

      (remoteMasterResults &&

        remoteMasterResults.benchmarks[benchmark].averages);

    measurements.forEach((measurement, i) => {

      const row = [chalk.gray(measurement.entry)];

      let remoteMean;

      let remoteSem;

      if (remoteMasterResults) {

        remoteMean = remoteMasterResults.benchmarks[benchmark].averages[i].mean;

        remoteSem = remoteMasterResults.benchmarks[benchmark].averages[i].sem;

        // https://en.wikipedia.org/wiki/1.96 gives a 99% confidence interval.

        const ci95 = remoteSem * 1.96;

        row.push(

          chalk.white(+remoteMean.toFixed(2) + ' ms +- ' + ci95.toFixed(2))

        );

      }

      let localMean;

      let localSem;

      if (localResults) {

        localMean = localResults.benchmarks[benchmark].averages[i].mean;

        localSem = localResults.benchmarks[benchmark].averages[i].sem;

        const ci95 = localSem * 1.96;

        row.push(

          chalk.white(+localMean.toFixed(2) + ' ms +- ' + ci95.toFixed(2))

        );

      }

      if (localResults && remoteMasterResults) {

        row.push(percentChange(remoteMean, localMean, remoteSem, localSem));

      }

      table.push(row);

    });

  });

}

function printResults(localResults, remoteMasterResults) {

  const head = [''];

  if (remoteMasterResults) {

    head.push(chalk.yellow.bold('Remote (Merge Base)'));

  }

  if (localResults) {

    head.push(chalk.green.bold('Local (Current Branch)'));

  }

  if (localResults && remoteMasterResults) {

    head.push('');

  }

  const table = new Table({head});

  addBenchmarkResults(table, localResults, remoteMasterResults);

  console.log(table.toString());

}

module.exports = printResults;