how to write if loop for delay reason

I've a data table where in I'm trying to get where is it causing a delay using the time stamps I've. I've a tracking number which is going from point A to point B

   `df
 ID          t1          t2                     t3                    t4  
 ABC  2017-07-05 12:30  2017-07-05 13:32     2017-07-05 14:00    2017-07-05 11:15
 ABC  2017-07-05 14:30  2017-07-05 15:11     2017-07-05 16:00       -      `

where

t1=  Planned Arrival time 
t2= Actualt arrival time 
t3= plannedeparturetime
t4= Actualdeparturetime

The first row shows date and time at point A and the second shows it at point B.

what I need to do is to find where the delay occured so I did some calculations

i <- strptime(x = as.character(df$t1),format = "%Y-%m-%d %H:%M") i1 <- strptime(x = as.character(df$t2),format = "%Y-%m-%d %H:%M") df$r1<-difftime(h, h1, units ="min")

so that is giving me the time difference between t1 and t2 and similarly for t3 and t4 and I get

f1- f2 118 -165 -139

then I tried to give a condition df$d2=ifelse(30>c,"delay bypersonc","ontime")

which gave me another column with

      `d2
 delay bypersonc
 delay bypersonc`

Now i've to do two things 1. to find who is causing the delay personc (who is like the driver) or person D ( is customer who has to get the items) where the load has to first go to person D on time and get of out on time which are (planned arrival and departure time) so that he can reach to point B on the time(planned arrival time present in second row)

let suppose in this the driver was to arrive at 12:30 but he came at 10:30 (so he is early here) and is supposed to leave from here at 14:00 but leaves at 11:15 (he left early here as well) and he was planned to come at 14:30 at point B (second row data) but comes at 15:11 which is late

so at point B he is late and overall the delay was caused by driver or personc so I want this to be the output.

this leads to four cases

 `c comes on time at A and leaves on time at A ---- no delay`

  `c comes late at A but leaves early at point A --- delay by c`

 ` c comes late and leave late at A       ---- delay by c`

  `c comes early but leaves late from A ----- delay by customer at A`

so I want this conditions to be fullfilled. I wrote some if statements which were very dirty. Any suggestion would help