There has to be a way to do this with awk or maybe I'm just focusing on the wrong tool and making this harder than it needs to be.

I'm trying to do a file field lookup/join at a very large scale but the output changes has to change dramatically. I have an input file to do a field lookup from and essentially do a field join out output with a one to many relationship of values that will be found. For each result, I need to write out a block of text based on results found.

If results are found, data is pulled together. If there's multiple results found in the data file, then it needs to organize the somewhat like the below. If no results are found, then it just uses field values from the original file. Once that is done to determine fields, then the output has to be output way different on separate lines.

Example:
1) File1.txt (file to process)

Code:

Site~Location~date~person
1~15~2017-01-01~me
2~28~2016-05-01~owner
3~68~2015-01-28~supervisor
4~69~2012-10-15~extra

2) File2.txt (file with data to pull in...join field2 from file1 to field1 from file2)

Code:

Location~Overriding Sites
15~12
15~13
15~14
15~10
28~99
68~100

3) Output text to write out (site value from file1 is dropped if results found and overriding site values used where a location can have multiple side ids):

Code:

Begin Record
Location: 15
Site Id: 12
Site Id: 13
Site Id: 14
Site Id: 10
Date: 2017-01-01
Contact: me
End Record

Begin Record
Location: 28
Site Id: 99
Date: 2016-05-01
Contact: owner
End Record

Begin Record
Location: 68
Site Id: 100
Date: 2015-01-28
Contact: supervisor
End Record

Begin Record
Location: 69
Site Id: 4
Date: 2012-10-15
Contact: extra
End Record

I've looked at this at a few different ways. And I'm getting myself turned around. Can you help?

Moderator's Comments:

Please use CODE tags when displaying sample input, output, and code segments.