#!/bin/bash

# verify-commit:
#  Ensures that a diff doesn't introduce code that clang-format would change

# Can be executed as a pre-commit hook by symlinking this script:
#  $ ln -s .git/hooks/pre-commit scripts/verify-commit
# Or used to verify changes between two commits
#  $ verify-commit HEAD~2 HEAD


# Determine if we need to check A-B or just cached changes
if [ "$#" == 2 ]; then
	DIFF_ARGS="$1 $2"
	CAN_ACCEPT=false
elif [ "$#" == 0 ]; then
	DIFF_ARGS="--cached"
	CAN_ACCEPT=true
else
	echo "Unrecognised arguments"
	exit 1
fi

CLANG_DIFF=$(git diff ${DIFF_ARGS} -U0 | clang-format-diff -p1)
WARNED=""

# Check the diff and warn if there is anything that doesn't match the style
if [ -n "$CLANG_DIFF" ]; then
	echo "Source does not match expected clang-format"
	echo "$CLANG_DIFF"
	WARNED="1"
fi

# Allow the user to override when running as a hook
if [ -n "$WARNED" ]; then
	echo "Warnings detected"
	if [ "$CAN_ACCEPT" = true ]; then
		read -p "Are you sure you want to commit? [Y/n] " -n 1 -r
		echo    # (optional) move to a new line
		if [[ ! $REPLY =~ ^[Yy]+$ ]]; then
			exit 1
		fi
	else
		exit 1
	fi
fi