const groups = require('./groups')

module.exports = isbn13 => {

const prefix = isbn13.substring(0, 3)

const restAfterPrefix = isbn13.substring(3)

const foundGroup = findGroup(prefix, restAfterPrefix, 5)

if (!foundGroup) return null

return {

group: foundGroup.groupId,

groupPrefix: foundGroup.groupPrefix,

ranges: foundGroup.groupData.ranges,

restAfterGroup: restAfterPrefix.slice(foundGroup.groupId.length)

}

}

function findGroup (prefix, restAfterPrefix, maxGroupIdLength) {

let length = 0

while (length <= maxGroupIdLength) {

const groupId = restAfterPrefix.slice(0, length)

const groupPrefix = `${prefix}-${groupId}`

const groupData = groups[groupPrefix]

if (groupData) return { groupId, groupPrefix, groupData }

else length++

}

}