#!/bin/bash

set -euo pipefail

name="$1"
f1="${2-/dev/null}"
f2="${5-/dev/null}"

name1="a/$name"
name2="b/$name"

if [ "$f1" = /dev/null ]
then
    name1=/dev/null
fi
if [ "$f2" = /dev/null ]
then
    name2=/dev/null
fi


if diff "$f1" "$f2" >/dev/null
then
  exit 0
fi


readlink_f()
{
    if [ $(uname) = 'Darwin' ]
    then
        local f=$(readlink "$1")
        if [ -z "$f" ]
        then
            f="$1"
        fi
        local d=$(dirname "$f")
        local b=$(basename "$f")
        if [ -d "$d" ]
        then
            (cd "$d" && echo "$(pwd -P)/$b")
        elif [[ "$d" = /* ]]
        then
            echo "$f"
        elif [[ "$d" = ./* ]]
        then
            echo "$(pwd -P)/${f/.\//}"
        else
            echo "$(pwd -P)/$f"
        fi
    else
        readlink -f "$1"
    fi
}

thisdir="$(dirname $(readlink_f "$0"))"

e_flag=''
if [ -z "${GIT_DIFF_IMAGE_ENABLED-}" ] || \
   ! which compare > /dev/null || \
   ! which montage > /dev/null
then
  e_flag='-e'
fi

o_flag=''
if [ -n "${GIT_DIFF_IMAGE_OUTPUT_DIR-}" ]
then
    mkdir -p "$GIT_DIFF_IMAGE_OUTPUT_DIR"
    destfile=''
    if [ "$name1" -ne '/dev/null' ]
    then
        destfile=$(basename "$name1")
    else
        destfile=$(basename "$name2")
    fi
    o_flag="-o $GIT_DIFF_IMAGE_OUTPUT_DIR/$destfile"
fi


exec "$thisdir/diff-image" $e_flag $o_flag -n "$name1" -N "$name2" "$f1" "$f2"