Select with Case Example in MS-SQL Server

SELECT [t0].[ProductID], ...
FROM [dbo].[Products] AS [t0]
LEFT OUTER JOIN [dbo].[Categories] AS [t1] ON [t1].[CategoryID] = [t0].[CategoryID]
WHERE (
    (CASE
        WHEN [t1].[CategoryName] = @p0 THEN
            (CASE
                WHEN [t0].[UnitsInStock] < @p1 THEN 1
                WHEN NOT ([t0].[UnitsInStock] < @p1) THEN 0
                ELSE NULL
             END)
        ELSE CONVERT(Int,
            (CASE
                WHEN NOT ([t0].[Discontinued] = 1) THEN 1
                WHEN NOT NOT ([t0].[Discontinued] = 1) THEN 0
                ELSE NULL
             END))
     END)) = 1