Excel BI Power Query 99 Challenge - Brian Julius solution

gistfile1.txt

let
    Source = Excel.CurrentWorkbook(){[Name="Table1"]}[Content],
    Type = Table.TransformColumnTypes(Source,{{"Date", type date}, {"Amount", Int64.Type}}),
    AddShortMon = Table.AddColumn(Type, "Month", each Text.Start( Date.MonthName( [Date] ), 3)),
    Group = Table.Group(AddShortMon, {"Month"}, {{"Min", each List.Min([Amount]), type nullable number}, {"Max", each List.Max([Amount]), type nullable number}, {"All", each _, type table [Date=nullable date, Amount=nullable number, Month=text]}}),
    Expand = Table.ExpandTableColumn(Group, "All", {"Date", "Amount"}, {"Date", "Amount"}),
    AddMinDate = Table.AddColumn(Expand, "MinDate", each if [Amount] = [Min] then [Date] else null, type text),
    AddMaxDate = Table.AddColumn(AddMinDate, "MaxDate", each if [Amount] = [Max] then [Date] else null, type text),
    Regroup = Table.Group(AddMaxDate, {"Month", "Min", "Max", "Amount"}, {{"MinDate2", each Text.Combine(List.Transform([MinDate], Text.From ), ", "), type nullable text},{"MaxDate2", each Text.Combine(List.Transform([MaxDate], Text.From ), ", "), type nullable text}}),
    ReReGroup = Table.Group(Regroup, {"Month", "Min", "Max"}, {{"Min Date", each List.Max([MinDate2]), type nullable text}, {"Max Date", each List.Max([MaxDate2]), type nullable text}}),
    Reorder = Table.ReorderColumns(ReReGroup,{"Month", "Min", "Min Date", "Max", "Max Date"})
in
    Reorder