#!/bin/bash

##################################################################################
# This script extracts the changelog for a given release version from the project
# changelog file. It is intended to be used in a release pipeline to generate a
# summary of the changes for the current release. The version number can be
# specified with the -v/--version flag.
#
# Usage: ./scripts/extract_changelog.sh -v <version> <changelog>
#
# Example: ./scripts/extract_changelog.sh -v 0.1.0 CHANGELOG.md
#
# Dependencies: grep, cut, sed, awk
##################################################################################

# Get flags
VALID_ARGS=$(getopt -o v --long version -- "$@")
if [[ $? -ne 0 ]]
then
    exit 1;
fi

# Parse flags
eval set -- "$VALID_ARGS"
while [ : ];
do
  case "$1" in
    -v | --version) version="$3"; changelog="$4" shift ;;
    --) shift; break;;
  esac
done

# Check if changelog is set or use default
if [ -z "$changelog" ]
then
  changelog="CHANGELOG.md"
fi

# Check if changelog exists
if [ ! -f "$changelog" ]
then
  echo "Changelog file not found: $changelog"
  exit 1
fi

# Check if version is set
if [ -z "$version" ]
then
  echo "Please specify a version, using the -v flag."
  exit 1 
fi

start_line=$(grep -n "## \[$version\]" $changelog | cut -d: -f1)

# Check if version exists in changelog
if [ -z "$start_line" ]
then
    echo "Version $version not found in changelog"
    exit 1
fi

end_lines=$(grep -n "^## \[" $changelog | cut -d: -f1)

# Find first line containing a version after the specified version
while read -r end_line; do
  if (( end_line > start_line )); then
    break
  fi
done <<< "$end_lines"

# If no version is found, set end_line to the end of the file
if [ -z "$end_line" ]
then
    end_line=$(wc -l < $changelog)
fi

# Subtract 2 from end_line to remove empty line and header for next section
end_line=$(($end_line-2))

# Return text between start_line and end_line
TEXT=$(awk "NR>=$start_line && NR<=$end_line" $changelog)
echo -e "$TEXT"