Merge with Dates

[Wkp]

Hi there, I am trying to improve my actual script to make it more functional.
Let me please paste below the result of merging the variables "i" and "u", getting result variable "r".
The condition I need to follow is the below:

merge i$id following the conditions:

         #####  if i$id = u$end.date AND there are no any u$id where  i$date >= u$registration.date AND i$date <u$end.date    ,   then merge i$id = u$end.date   ...... If not, merge i$id when i$date >= u$registration.date AND i$date <u$end.date 

i<-data.frame(id = c(1, 2), date= as.Date.character( c("2019-01-01", "2018-01-01")))



u<-data.frame(id = c(1, 1, 2, 1, 2, 1, 1, 2, 1,2), registration.date= as.Date.character( c("2011-01-01", "2012-01-01",
                                                                                           "2013-01-01", "2014-01-01",
                                                                                           "2015-01-01", "2016-01-01",
                                                                                           "2017-01-01", "2018-02-02",
                                                                                           "2019-01-01", "2020-01-01")),
              end.date= as.Date.character( c("2014-01-01", "2013-01-01",
                                             "2016-01-01", "2017-01-01",
                                             "2018-01-01", "2019-01-01",
                                             "2020-01-01", "2021-01-01",
                                             "2022-01-01", "2023-01-01")),
              Tarif= c(100, 150, 175, 179, 199, 194, 193, 188, 185, 166) )



r <- data.frame(id= c(1,2), date = as.Date.character( c("2019-01-01", "2018-01-01")), 
                registration.date= as.Date.character( c("2019-01-01", "2015-01-01")),
                end.date= as.Date.character( c("2022-01-01", "2018-01-01")), 
                Tarif= c(185, 188))