How to get previous state for each state per customer

[HeirsPowerBi]

Hello Guys i have a dataset  that looks like this

Task	Date	State
A	1/1/2022	Enter
A	1/2/2022	Break
A	1/3/2022	Continue
B	1/4/2022	Enter
B	1/5/2022	Fall out
B	1/6/2022	Carrier Step
C	1/7/2022	Enter
C	1/8/2022	Go Live
C	1/9/2022	Retrace

I am trying to create another column that will tell me the previous state based on the date for each state per task.

output would look like this

Task	Date	State	Previous State
A	1/1/2022	Enter
A	1/2/2022	Break	Enter
A	1/3/2022	Continue	Break
B	1/4/2022	Enter
B	1/5/2022	Fall out	Enter
B	1/6/2022	Carrier Step	Fall out
C	1/7/2022	Enter
C	1/8/2022	Go Live	Enter
C	1/9/2022	Retrace	Go Live

I need to do this in power query because there are some other transformations i need to with that column before loading it.

[Vijay_A_Verma · Accepted solution]

Solution file uploaded to - https://1drv.ms/x/s!Akd5y6ruJhvhuSf4jBWInubgMG_Q?e=K1J6Dq 

Below is M Code

let
    Source = Excel.CurrentWorkbook(){[Name="Table1"]}[Content],
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Task", type text}, {"Date", type date}, {"State", type text}}),
    #"Grouped Rows" = Table.Group(#"Changed Type", {"Task"}, {{"Temp", each _, type table [Task=nullable text, Date=nullable date, State=nullable text]}}),
    //Function Start
    fxProcessTable = (InputTable)=>
        let
            #"Added Index" = Table.AddIndexColumn(InputTable, "Index", 0, 1, Int64.Type),
            #"Added Custom" = Table.AddColumn(#"Added Index", "Previous State", each try if [State]="Enter" then "null" else #"Added Index"[State]{[Index]-1} otherwise null),
            #"Removed Columns" = Table.RemoveColumns(#"Added Custom",{"Index"})
        in
            #"Removed Columns",
    //Function End
    #"Custom" = Table.AddColumn(#"Grouped Rows", "RunFunction", each fxProcessTable([Temp])),
    #"Expanded RunFunction" = Table.ExpandTableColumn(Custom, "RunFunction", {"Date", "State", "Previous State"}, {"Date", "State", "Previous State"}),
    #"Removed Columns" = Table.RemoveColumns(#"Expanded RunFunction",{"Temp"})
in
    #"Removed Columns"

[HeirsPowerBi]

I figured out a way around that is similar to this but was not working but your solution has pointed me to what was missing.

[HeirsPowerBi]

Thank you so much, this helped alot