#!/usr/bin/env bash

set -e
set -u
set -o pipefail

readonly URL='https://github.com/MetaMask/metamask-mobile'

git fetch --tags

most_recent_tag="$(git describe --tags "$(git rev-list --tags --max-count=1)")"

git rev-list "${most_recent_tag}"..HEAD --reverse | while read commit

do
	subject="$(git show -s --format="%s" "$commit")"

	# Squash & Merge: the commit subject is parsed as `<description> (#<PR ID>)`
	if grep -E -q '\(#[[:digit:]]+\)' <<< "$subject"
	then
		pr="$(awk '{print $NF}' <<< "$subject" | tr -d '()')"
		prefix="[$pr]($URL/pull/${pr###}): "
		description="$(awk '{NF--; print $0}' <<< "$subject")"

	# Merge: the PR ID is parsed from the git subject (which is of the form `Merge pull request
	#   #<PR ID> from <branch>`, and the description is assumed to be the first line of the body.
	#   If no body is found, the description is set to the commit subject
	elif grep -E -q '#[[:digit:]]+\sfrom' <<< "$subject"
	then
		pr="$(awk '{print $4}' <<< "$subject")"
		prefix="[$pr]($URL/pull/${pr###}): "

		first_line_of_body="$(git show -s --format="%b" "$commit" | head -n 1 | tr -d '\r')"
		if [[ -z "$first_line_of_body" ]]
		then
			description="$subject"
		else
			description="$first_line_of_body"
		fi

	# Normal commits: The commit subject is the description, and the PR ID is omitted.
	else
		pr=''
		prefix=''
		description="$subject"
	fi

	# add entry to CHANGELOG
	if [[ "$OSTYPE" == "linux-gnu" ]]
	then
		# shellcheck disable=SC1004
		sed -i'' '/## Current Main Branch/a\
- '"$prefix$description"''$'\n' CHANGELOG.md
	else
		# shellcheck disable=SC1004
		sed -i '' '/## Current Main Branch/a\
- '"$prefix$description"''$'\n' CHANGELOG.md
	fi
done
echo 'CHANGELOG updated'