var zeroPad = require('./zero-pad')
var getGroups = require('./get-groups')
var getBase = require('./get-base')
var stringify = require('./stringify')
var toggle24Hr = require('./toggle-24-hour')
var isTwelveHourTime = require('./is-twelve-hour-time')
module.exports = function adder (str, groupId, amount) {
var groups = getGroups(str)
var twelveHourTime = isTwelveHourTime(groups)
if (twelveHourTime && groupId === groups.length - 1) return stringify(toggle24Hr(groups))
return stringify(add(groups, groupId, amount, twelveHourTime))
}
function add (groups, groupId, amount, twelveHourTime) {
var base = getBase(groupId, twelveHourTime)
if (!groupId && groups[groupId] === '12' && twelveHourTime) groups[groupId] = '00'
var val = Number(groups[groupId]) + amount
groups = replace(groups, groupId, (val + base) % base)
if (groupId && val >= base) return add(groups, groupId - 1, 1, twelveHourTime)
if (groupId && val < 0) return add(groups, groupId - 1, -1, twelveHourTime)
if (!groupId && twelveHourTime) {
if (val >= base || val < 0) toggle24Hr(groups)
if (groups[0] === '00') groups[0] = '12'
}
return groups
}
function replace (groups, groupId, amount) {
var digits = groups[groupId].length
groups[groupId] = zeroPad(String(amount), digits)
return groups
}
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