#!/usr/bin/env bash
#
# Converts assertion failure text involving two mutations to a diff.
#

cmd="diff -au"
sed_cmd="sed -E"

while getopts ":d:" opt; do
    case $opt in
    d)
        cmd="$OPTARG";;
    *)
        echo "Usage: $0 [-d diff_command] [<path-to-test-output-file>]" 1>&2
        exit 1;;
    esac
done
shift $((OPTIND-1))

file="$1"
if [ -z "$file" -o "$file" = "-" ]; then
    tmpfile=$(mktemp)
    cat > "$tmpfile"
    file="$tmpfile"
fi

function filter {
    $sed_cmd 's/@0x[0-9a-f]*//g'
}

begin="(expected |critical check .+ == .+ has failed \[)"
middle="(got:|\!=)"
end="^$|\}\]|Leaving test case"

$cmd <($sed_cmd -n "/$begin/,/$middle/p" "$file" | head -n-1 | $sed_cmd "s/.*$begin/&\n/" | filter) \
     <($sed_cmd -n "/$middle/,/$end/p" "$file" | $sed_cmd "s/.*$middle /&\n/" | filter) | less -R

if [ -n "$tmpfile" ]; then
    rm -f "$tmpfile"
fi