Find a word in a file and then add a line before the next known word - sed

Question

I am trying to add a comment "##INSERT-A NEW-LINE-HERE" in a file which looks like this:
location /test/ {
#keepalive_timeout 0;
proxy_http_version 1.1;
proxy_set_header Accept-Encoding "";
proxy_set_header X-Forwarded-For;
proxy_set_header Access-Control-Al;
proxy_pass https://test.company.in/;
proxy_set_header Host test.company.in;
#proxy_set_header Referer $http_referer;
##INSERT-A NEW-LINE-HERE
if ($http_referer ~* ^(https?\:\/\/)(.*?)\/test\/(.*?)$) {
set $real_referer https://test.company.in/$3;
}
proxy_set_header Referer $real_referer;
proxy_redirect http://test.company.in/ https://sample.company.in/test/;
proxy_redirect https://test.company.in/ https://sample.company.in/test/;
proxy_redirect / https://sample.company.in/test/
sub_filter_types *;
sub_filter 'href="/' 'href="/test/';
sub_filter 'href="../' 'href="../test/';
sub_filter 'href=../' 'href=../test/';
}
location /test_app1/ {
#keepalive_timeout 0;
proxy_http_version 1.1;
proxy_set_header Accept-Encoding "";
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header Access-Control-Allow-Origin https://test.app1.in;
proxy_pass https://test.app1.in/;
proxy_set_header Host test.app1.in;
#proxy_set_header Referer $http_referer;
##INSERT-A NEW-LINE-HERE
if ($http_referer ~* ^(https?\:\/\/)(.*?)\/test\/(.*?)$) {
set $real_referer https://test.app1.in/$3;
}
proxy_set_header Referer $real_referer;
proxy_redirect http://test.app1.in/ https://sample.company.in/test_app1/;
proxy_redirect http://sample.company.in/ https://sample.company.in/test_app1/;
proxy_redirect https://test.app1.in/ https://sample.company.in/test_app1/;
proxy_redirect https://test.app1.in https://sample.company.in/test_app1/;
proxy_redirect https://sample.company.in/ https://sample.company.in/test_app1/;
##DO-NOTINSERT-A NEW-LINE-HERE-AS-IT-IS-SECOND-IF-BLOCK
if ($http_referer ~* ^(https?\:\/\/)(.*?)\/test\/(.*?)$) {
set $real_referer https://test.app1.in/$3;
}
proxy_set_header Referer $real_referer;
proxy_redirect / https://sample.company.in/test_app1/;
}
I want to add a comment ONLY before first IF-BLOCK after every LOCATION-BLOCK
Here is what I have currently:
sed -i '/if ($http_referer/i
##INSERT-A NEW-LINE-HERE
' file.conf
Using this above code the comment appears above all IF BLOCKS and I only need this comment for first IF-BLOCK after every LOCATION-BLOCK

Answer 1

This might work for you (GNU sed):
sed '/^\s*location .*{$/{:a;n;/^\s*if /!ba;h;s/\S.*/INSERTED LINE\n/;G}' file
Match on location and then continue reading lines until another match of one beginning if.
Make a copy of if, replace the line (starting at the first non white spaced character) with the intended text (with a further newline).
Append the original line.
Repeat.
N.B. This assumes all such locations contain an if clause somewhere.

Answer 2

my guess is the code provided will insert the comment before every instance of 'if ($http_referer'. To only insert the comment before the first instance of 'if ($http_referer' after every 'location /test/ {', use the following code:
sed -i '/location \/test\//i\
##INSERT-A NEW-LINE-HERE
' file.conf

Answer 3

This sed command should do the job:
sed -i.bak '
/^[[:blank:]]*location.*{/,/^[[:blank:]]*if[[:blank:]]*(/!b
/^[[:blank:]]*if[[:blank:]]*(/i\
##INSERT-A NEW-LINE-HERE
' file