Generate sequense from a value using R

I have a dataset that looks like this:

date    |country   | crisis | 
2011 q2 |   AT     |    0   |
2011 q3 |   AT     |    0   |
2011 q4 |   AT     |    1   |
2012 q1 |   AT     |    0   |
2012 q2 |   AT     |    1   | 
2011 q1 |   BE     |    0   |
2011 q3 |   BE     |    0   |
2011 q4 |   BE     |    0   |
2012 q1 |   BE     |    1   |
2012 q2 |   BE     |    0   | 

And I would like to compute another variable for each country-crisis pair that is 0 when crisis is 1 and then create a sequence from -24 to +24 starting from zero, like this

date    |country   | crisis | AT_crisis1 | AT_crisis2 | BE_crisis 1
2011 q2 |   AT     |    0   |  -2        |     -4     |    NA
2011 q3 |   AT     |    0   |  -1        |     -3     |    NA
2011 q4 |   AT     |    1   |   0        |     -2     |    NA
2012 q1 |   AT     |    0   |   1        |     -1     |    NA
2012 q2 |   AT     |    1   |   2        |      0     |    NA
2011 q1 |   BE     |    0   |   NA       |     NA     |    -3
2011 q3 |   BE     |    0   |   NA       |     NA     |    -2
2011 q4 |   BE     |    0   |   NA       |     NA     |    -1
2012 q1 |   BE     |    1   |   NA       |     NA     |     0
2012 q2 |   BE     |    0   |   NA       |     NA     |    +1

Here a reproducible example for the first dataset

library(zoo)

date <- c("2011Q2","2011Q3","2011Q4","2012Q1","2012Q2","2011Q2","2011Q3","2011Q4","2012Q1","2012Q2")
date <- as.yearqtr(date)
country <- c("AT","AT","AT","AT","AT","BE","BE","BE","BE","BE")
crisis <- c(0,0,1,0,1,0,0,0,1,0)

df <- data.frame(date, country, crisis)

Thank you.