Shell Programming and Scripting

Just began to learn on Shell Script. I got an exercise from my friend. I know how to make this happen in C, but I'm not familiar with Shell Script. Hope I can get some help from all of you.
I want to write a bash script to comment code blocks in a bash source file. What I mean comment is '#', I know that there is a build in command : would help. But I still have no idea how should I start this.
Should I read the source file first, Then output it as another file?

Here is an example:

Original Source File:

Code:

Final=$(date -d "2016-12-15 14:00" "+%j")
while true ; do
  Today=$(date "+%j")
  Days=$((Final - Today))
  if (( Days >= 14 )) ; then
    echo party
  elif (( Days >= 2 )) ; then
    echo study
  elif (( Days == 1 )) ; then
    for Count in 1 2 3   # loop 2
      do
      echo panic
    done   # loop 2
  else
    break
  fi
  sleep 8h
done

After Script:

Code:

Final=$(date -d "2016-12-15 14:00" "+%j")
while true ; do   # loop 1
  Today=$(date "+%j")
  Days=$((Final - Today))
  if (( Days >= 14 )) ; then   # selection 1
    echo party
  elif (( Days >= 2 )) ; then
    echo study
  elif (( Days == 1 )) ; then
    for Count in 1 2 3   # loop 2
      do
      echo panic
    done   # loop 2
  else
    break
  fi   # selection 1
  sleep 8h
done   # loop 1

Here is some other requirement:
Read from standard input, write to standard output.
At the end of any line containing while until for add the comment: # loop n
At the end of any line containing done add the comment: # loop n
At the end of any line containing if case add the comment: # selection n
At the end of any line containing fi esac add the comment: # selection n

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