#!/bin/sh
set -e

usage() {
    argv0=$(basename $0)
    echo "Usage:" >&2
    echo "For comparing files created my cairo-perf:" >&2
    echo "" >&2
    echo "	$argv0 old.perf new.perf" >&2
    echo "" >&2
    echo "For comparing (cached) performance of revisions:" >&2
    echo "" >&2
    echo "	$argv0 <revision>" >&2
    echo "	$argv0 <rev1> <rev2>" >&2
    echo "" >&2
    echo "If given a single revision, compares its results to that of its" >&2
    echo "(first-parent) predecessor. Otherwise compares the two given revisions." >&2
    echo "The revisions can be any revision accepted by git. For example:" >&2
    echo "" >&2
    echo "	$argv0 HEAD		# Show impact of latest commit" >&2
    echo "	$argv0 1.2.0 1.2.4	# Compare performance of 1.2.0 to 1.2.4" >&2
    echo "" >&2
    echo "The performance results are cached in .perf next to the .git directory." >&2
    exit 1
}

if [ $# -eq 1 ]; then
    old="$1^"
    new="$1"
elif [ $# -eq 2 ]; then
    old="$1"
    new="$2"
else
    usage
fi

git_setup() {
    SUBDIRECTORY_OK='Yes'
    . git-sh-setup
    CAIRO_DIR=$(dirname $GIT_DIR)
    if [ "$CAIRO_DIR" = "." ]; then
	CAIRO_DIR=$(pwd)
    fi
    CAIRO_PERF_DIR=$CAIRO_DIR/.perf
}

rev2sha() {
    rev=$1
    git rev-parse --verify $rev || ( echo "Cannot resolve $rev as a git object" && exit 1 )
}

# We cache performance output based on a two-part name capturing the
# current performance test suite and the library being tested. We
# capture these as the tree object of the perf directory in HEAD and
# the tree object of the src directory of the revision being tested.
#
# This way, whenever the performance suite is updated, cached output
# from old versions of the suite are automatically invalidated. Also,
# if a commit just changes things outside of the src tree, (say it
# changes the "test" test suite, or README or configure.in, or
# whatever), cairo-perf-diff will be smart enough to still use cached
# results from a run with an equivalent src tree.
rev2perf() {
    rev=$1
    src_tree_sha=$(rev2sha $rev:src)
    perf_tree_sha=$(rev2sha HEAD:perf)
    echo "$CAIRO_PERF_DIR/${perf_tree_sha}-${src_tree_sha}.perf"
}

# Usage: run_cairo_perf_if_not_cached <rev>
run_cairo_perf_if_not_cached() {
    rev=$1

    owd=$(pwd)
    sha=$(rev2sha $rev)
    perf=$(rev2perf $rev)
    if [ -e $perf ]; then
	return 0
    fi
    if [ ! -d $CAIRO_PERF_DIR ]; then
	echo "Creating new perf cache in $CAIRO_PERF_DIR"
	mkdir $CAIRO_PERF_DIR
    fi
    cd $CAIRO_PERF_DIR

    if [ ! -d build ]; then
	git clone -s $CAIRO_DIR build
	(cd build; git checkout -b tmp-cairo-perf-diff $sha; CFLAGS="-O2" ./autogen.sh)
    fi
    cd build

    git checkout tmp-cairo-perf-diff
    git reset --hard $sha
    make CFLAGS="-O2" || (rm config.cache && make CFLAGS="-O2")
    cp -a $CAIRO_DIR/boilerplate .
    (cd boilerplate; make)
    cp -a $CAIRO_DIR/perf .
    cd perf;
    make || exit 1
    (make perf || echo "*** Performance test crashed") > $perf
    cd $owd
}

if [ ! -e $old ]; then
    git_setup
    run_cairo_perf_if_not_cached $old
    old=$(rev2perf $old)
fi

if [ ! -e $new ]; then
    git_setup
    run_cairo_perf_if_not_cached $new
    new=$(rev2perf $new)
fi

cairo-perf-diff-files $old $new