Replace every nth occurrence of 'foo' with the nth consecutive regular range of lines from a given file

Question

I would like to replace each nth occurrence of foo on the 1.txt file with the nth consecutive regular range of lines every nth lines (say in this case every 2 lines) from the 0.txt file containing the following content below (this is MWE).

source file is 0.txt:

The sun has its own light
foo
The moon reflects the sunlight
foo
The planet Earth receives both sunlight and moonlight
foo

target file is 1.txt:

source-text1
[(('f1','b1'), ('g1','h1'))]
source-text-2
[(('f2','b2'), ('g2','h2'))]
source-text-3
[(('f3','b3'), ('g3','h3'))]

Applying the replacement, e.g. 'command_method' 0.txt 1.txt > 2.txt , pseudocode, I would have the desired output file is as below, being the printed output on a third 2.txt file:

expected output is 2.txt:

The sun has its own light
source-text1
[(('f1','b1'), ('g1','h1'))]
The moon reflects the sunlight
source-text-2
[(('f2','b2'), ('g2','h2'))]
The planet Earth receives both sunlight and moonlight
source-text-3
[(('f3','b3'), ('g3','h3'))]

I tried:

awk 'NR==FNR {a[NR]=$0; next} /foo/{gsub("foo", a[int(k++/2)%3 + 2])} 1' 1.txt 0.txt > 2.txt

but this gives me 2.txt:

The sun has its own light
[(('f1','b1'), ('g1','h1'))]
The moon reflects the sunlight
[(('f1','b1'), ('g1','h1'))]
The planet Earth receives both sunlight and moonlight
source-text-2

I don't have ideas anymore. I'm looking for a solution that can work with any size range of lines

Answer 1

Assumptions:

• foo only occurs in a line by itself
• if foo occurs more times than we have replacement strings, do not replace foo

Setup:

$ cat 0.txt
The sun has its own light
foo
The moon reflects the sunlight
foo
The planet Earth receives both sunlight and moonlight
foo
The following line should NOT be replaced
foo

$ cat 1.txt
source-text1
[(('f1','b1'), ('g1','h1'))]
source-text-2
[(('f2','b2'), ('g2','h2'))]
source-text-3
[(('f3','b3'), ('g3','h3'))]

One awk idea:

awk -v setsize=2 -v ptn="foo" '                        # setsize == number of lines from first file that define a replacement set
                                                       # ptn == string to be replaced

FNR==NR { replace[++rcount]= $0                        # start replacement string
          for (i=1;i<setsize;i++) {                    # append to replacement string until we have read "setsize" lines into the replacement string
              getline
              replace[rcount]=replace[rcount] RS $0
          }
          next
        }
$0~ptn  { if (++pcount in replace)                     # if we have a replacement string then ...
              $0=replace[pcount]                       # replace the current line
        }
1                                                      # print the current line

' 1.txt 0.txt

This generates:

The sun has its own light
source-text1
[(('f1','b1'), ('g1','h1'))]
The moon reflects the sunlight
source-text-2
[(('f2','b2'), ('g2','h2'))]
The planet Earth receives both sunlight and moonlight
source-text-3
[(('f3','b3'), ('g3','h3'))]
The following line should NOT be replaced
foo