overleaf/services/web/app/src/Features/SplitTests/SplitTestManager.js

const { SplitTest } = require('../../models/SplitTest')
const OError = require('@overleaf/o-error')
const _ = require('lodash')

const ALPHA_PHASE = 'alpha'
const BETA_PHASE = 'beta'
const RELEASE_PHASE = 'release'

async function getSplitTests({ name, activeOnly, archivedOnly }) {
  const filters = {}
  if (name && name !== '') {
    filters.name = { $regex: _.escapeRegExp(name) }
  }
  if (activeOnly) {
    filters.$where = 'this.versions[this.versions.length - 1].active === true'
  }
  if (archivedOnly) {
    filters.archived = true
  } else {
    filters.archived = { $ne: true }
  }
  try {
    return await SplitTest.find(filters).limit(100).exec()
  } catch (error) {
    throw OError.tag(error, 'Failed to get split tests list')
  }
}

async function getSplitTest(query) {
  try {
    return await SplitTest.findOne(query).exec()
  } catch (error) {
    throw OError.tag(error, 'Failed to get split test', { query })
  }
}

async function createSplitTest(name, configuration, info = {}) {
  const stripedVariants = []
  let stripeStart = 0
  _checkNewVariantsConfiguration([], configuration.variants)
  for (const variant of configuration.variants) {
    stripedVariants.push({
      name: (variant.name || '').trim(),
      rolloutPercent: variant.rolloutPercent,
      rolloutStripes:
        variant.rolloutPercent > 0
          ? [
              {
                start: stripeStart,
                end: stripeStart + variant.rolloutPercent,
              },
            ]
          : [],
    })
    stripeStart += variant.rolloutPercent
  }
  const splitTest = new SplitTest({
    name: (name || '').trim(),
    description: info.description,
    expectedEndDate: info.expectedEndDate,
    ticketUrl: info.ticketUrl,
    reportsUrls: info.reportsUrls,
    winningVariant: info.winningVariant,
    versions: [
      {
        versionNumber: 1,
        phase: configuration.phase,
        active: configuration.active,
        analyticsEnabled:
          configuration.active && configuration.analyticsEnabled,
        variants: stripedVariants,
      },
    ],
  })
  return _saveSplitTest(splitTest)
}

async function updateSplitTestConfig(name, configuration) {
  const splitTest = await getSplitTest({ name })
  if (!splitTest) {
    throw new OError(`Cannot update split test '${name}': not found`)
  }
  if (splitTest.archived) {
    throw new OError('Cannot update an archived split test', { name })
  }
  const lastVersion = splitTest.getCurrentVersion().toObject()
  if (configuration.phase !== lastVersion.phase) {
    throw new OError(
      `Cannot update with different phase - use /switch-to-next-phase endpoint instead`
    )
  }
  _checkNewVariantsConfiguration(lastVersion.variants, configuration.variants)
  const updatedVariants = _updateVariantsWithNewConfiguration(
    lastVersion.variants,
    configuration.variants
  )

  splitTest.versions.push({
    versionNumber: lastVersion.versionNumber + 1,
    phase: configuration.phase,
    active: configuration.active,
    analyticsEnabled: configuration.active && configuration.analyticsEnabled,
    variants: updatedVariants,
  })
  return _saveSplitTest(splitTest)
}

async function updateSplitTestInfo(name, info) {
  const splitTest = await getSplitTest({ name })
  if (!splitTest) {
    throw new OError(`Cannot update split test '${name}': not found`)
  }
  splitTest.description = info.description
  splitTest.expectedEndDate = info.expectedEndDate
  splitTest.ticketUrl = info.ticketUrl
  splitTest.reportsUrls = info.reportsUrls
  splitTest.winningVariant = info.winningVariant
  return _saveSplitTest(splitTest)
}

async function switchToNextPhase(name) {
  const splitTest = await getSplitTest({ name })
  if (!splitTest) {
    throw new OError(
      `Cannot switch split test with ID '${name}' to next phase: not found`
    )
  }
  if (splitTest.archived) {
    throw new OError('Cannot switch an archived split test to next phase', {
      name,
    })
  }
  const lastVersionCopy = splitTest.getCurrentVersion().toObject()
  lastVersionCopy.versionNumber++
  if (lastVersionCopy.phase === ALPHA_PHASE) {
    lastVersionCopy.phase = BETA_PHASE
  } else if (lastVersionCopy.phase === BETA_PHASE) {
    if (splitTest.forbidReleasePhase) {
      throw new OError('Switch to release phase is disabled for this test', {
        name,
      })
    }
    lastVersionCopy.phase = RELEASE_PHASE
  } else if (splitTest.phase === RELEASE_PHASE) {
    throw new OError(
      `Split test with ID '${name}' is already in the release phase`
    )
  }
  for (const variant of lastVersionCopy.variants) {
    variant.rolloutPercent = 0
    variant.rolloutStripes = []
  }
  splitTest.versions.push(lastVersionCopy)
  return _saveSplitTest(splitTest)
}

async function revertToPreviousVersion(name, versionNumber) {
  const splitTest = await getSplitTest({ name })
  if (!splitTest) {
    throw new OError(
      `Cannot revert split test with ID '${name}' to previous version: not found`
    )
  }
  if (splitTest.archived) {
    throw new OError(
      'Cannot revert an archived split test to previous version',
      {
        name,
      }
    )
  }
  if (splitTest.versions.length <= 1) {
    throw new OError(
      `Cannot revert split test with ID '${name}' to previous version: split test must have at least 2 versions`
    )
  }
  const previousVersion = splitTest.getVersion(versionNumber)
  if (!previousVersion) {
    throw new OError(
      `Cannot revert split test with ID '${name}' to version number ${versionNumber}: version not found`
    )
  }
  const lastVersion = splitTest.getCurrentVersion()
  if (
    lastVersion.phase === RELEASE_PHASE &&
    previousVersion.phase !== RELEASE_PHASE
  ) {
    splitTest.forbidReleasePhase = true
  }
  const previousVersionCopy = previousVersion.toObject()
  previousVersionCopy.versionNumber = lastVersion.versionNumber + 1
  splitTest.versions.push(previousVersionCopy)
  return _saveSplitTest(splitTest)
}

async function archive(name) {
  const splitTest = await getSplitTest({ name })
  if (!splitTest) {
    throw new OError(`Cannot archive split test with ID '${name}': not found`)
  }
  if (splitTest.archived) {
    throw new OError(`Split test with ID '${name}' is already archived`)
  }
  splitTest.archived = true
  const previousVersionCopy = splitTest.getCurrentVersion().toObject()
  previousVersionCopy.versionNumber += 1
  previousVersionCopy.active = false
  splitTest.versions.push(previousVersionCopy)
  return _saveSplitTest(splitTest)
}

function _checkNewVariantsConfiguration(variants, newVariantsConfiguration) {
  const totalRolloutPercentage = _getTotalRolloutPercentage(
    newVariantsConfiguration
  )
  if (totalRolloutPercentage > 100) {
    throw new OError(`Total variants rollout percentage cannot exceed 100`)
  }
  for (const variant of variants) {
    const newVariantConfiguration = _.find(newVariantsConfiguration, {
      name: variant.name,
    })
    if (!newVariantConfiguration) {
      throw new OError(
        `Variant defined in previous version as ${JSON.stringify(
          variant
        )} cannot be removed in new configuration: either set it inactive or create a new split test`
      )
    }
    if (newVariantConfiguration.rolloutPercent < variant.rolloutPercent) {
      throw new OError(
        `Rollout percentage for variant defined in previous version as ${JSON.stringify(
          variant
        )} cannot be decreased: revert to a previous configuration instead`
      )
    }
  }
}

function _updateVariantsWithNewConfiguration(
  variants,
  newVariantsConfiguration
) {
  let totalRolloutPercentage = _getTotalRolloutPercentage(variants)
  const variantsCopy = _.clone(variants)
  for (const newVariantConfig of newVariantsConfiguration) {
    if (newVariantConfig.rolloutPercent === 0) {
      continue
    }
    const variant = _.find(variantsCopy, { name: newVariantConfig.name })
    if (!variant) {
      variantsCopy.push({
        name: newVariantConfig.name,
        rolloutPercent: newVariantConfig.rolloutPercent,
        rolloutStripes: [
          {
            start: totalRolloutPercentage,
            end: totalRolloutPercentage + newVariantConfig.rolloutPercent,
          },
        ],
      })
      totalRolloutPercentage += newVariantConfig.rolloutPercent
    } else if (variant.rolloutPercent < newVariantConfig.rolloutPercent) {
      const newStripeSize =
        newVariantConfig.rolloutPercent - variant.rolloutPercent
      variant.rolloutPercent = newVariantConfig.rolloutPercent
      variant.rolloutStripes.push({
        start: totalRolloutPercentage,
        end: totalRolloutPercentage + newStripeSize,
      })
      totalRolloutPercentage += newStripeSize
    }
  }
  return variantsCopy
}

function _getTotalRolloutPercentage(variants) {
  return _.sumBy(variants, 'rolloutPercent')
}

async function _saveSplitTest(splitTest) {
  try {
    return (await splitTest.save()).toObject()
  } catch (error) {
    throw OError.tag(error, 'Failed to save split test', {
      splitTest: JSON.stringify(splitTest),
    })
  }
}

module.exports = {
  getSplitTest,
  getSplitTests,
  createSplitTest,
  updateSplitTestConfig,
  updateSplitTestInfo,
  switchToNextPhase,
  revertToPreviousVersion,
  archive,
}