How to create a list considering a condition in sql (azure databricks)

I am working on a SQL query (Azure Databricks environment), where considering the following dataset:

I want to get the following output:

where the user_jorney column is composed of the channels that participated in a conversion journey. Note that the journey of users who, until then, have not made a purchase is also built.

Looking for commands that can help with this task, I found concat_ws, where I wrote the code below:

select 
  clientid, 
  concat_ws(',', collect_list(channel)) as user_journey, 
  sum(purchase) as conversion
from table_name group by  clientid;

I get this result:

Now I'm trying to consider a condition to get the desired result but so far I haven't been able to find.

Could you help me how can i solve this task?

I tried to repro your scenario,

where I gave sub query instead of original table in that query, I am selecting original table along with one extra column as row number where I am giving row number two every row partitioned by visit_order column and orderd by visited column.

My Query:

select 
  clientid,
  concat_ws(',', collect_list(channel)) as user_journey, 
  sum(purchase) as conversion
from (SELECT *,ROW_NUMBER() OVER (PARTITION BY visit_order ORDER BY visited) AS RowNumber FROM docs) as docstb group by clientid , RowNumber order by clientid asc

Execution and Output: