#! /bin/sh
# Copyright (c) 2008-2020 Robert Virding
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
# The lfescript script.

# Follow symlinks to actual program and set env variables.  We have to
# cd to each directory following symlinks to handle relative symlinks.

follow_symlink () {
    cd "$(dirname "$1")" > /dev/null
    filename="$(basename "$1")"
    if [ -h "$filename" ]; then
        follow_symlink "$(readlink "$filename")"
    else
        echo "$(pwd -P)/$filename"
    fi
}

show_help () {
    echo "Usage: `basename $0` [flags] file [args]

    -h | --help       Print this help and exit
    -flag             Passes configuration flags to be used on startup" >&2
}

SELF=$(follow_symlink "$0")
LFE_PROGNAME=$(echo "$0" | sed 's/.*\///') # Basically basename
LFE_BINDIR=$(dirname "$SELF")
LFE_ROOTDIR=$(dirname "$LFE_BINDIR")

export LFE_ROOTDIR
export LFE_BINDIR
export LFE_PROGNAME

# Set which emulator to use, the default is erl.
emulator=${LFESCRIPT_EMULATOR-"erl28"}

# Collect any script options starting with '-' upto the script name.
# Valid script options are only flags without arguments.

i="$#"                          # Counter

while [ "$i" -gt 0 ]; do
    case "$1" in
        -h | --help) # Help
            $(show_help)
            exit 1 ;;
        -*)          # Flags
            arg=`echo $1 | sed 's/^-//'`
            set -- "$@" "$arg"
            shift ; i=`expr $i - 1`
            ;;
        *)      # Plain argument
            break ;;
    esac
done

# Get the scriptname.
scriptname="$1"

# Split options and scriptname/args.
set -- "$@" "-extra"

# Step over the args section adding them to the end.
while [ "$i" -gt 0 ]; do
    set -- "$@" "$1"
    shift ; i=`expr $i - 1`
done

# Try to find an explicit emulator flag option line in line 2 or 3 of
# script file.

# Read the first three lines of the script file.
if [ -z "$scriptname" ]; then
    echo "lfescript: Missing filename" ; exit 127
elif [ -f "$scriptname" -a -r "$scriptname"  ]; then
    { read line1; read line2; read line3; } < "$scriptname"
else
    echo "lfescript: Failed to open file: $scriptname" ; exit 127
fi

# Search for explicit emulator flag option line.
shebangs=$(expr "$line2" : '^;;! *\(.*\)')
if [ -z "$shebangs" ] ; then shebangs=$(expr "$line3" : '^;;! *\(.*\)') ; fi

# Done, now just run the emulator.
# The order of precedence for LFE libraries is as follows:
# 1) The LFE_ROOTDIR for the current bin/lfe being executed is unusurpable;
#    allowing anything else would leave LFE open to instabilities where it
#    could be executed with libraries of a different release.
# 2) A user/developer should be allowed to override anything else by updating
#    ERL_LIBS as they see fit.
# 3) A project's libraries (current directory) should be loaded automatically,
#    if they exist, but not override the previous two.
# 4) If a default library is installed in ~/.lfe/libs, then that will be added
#    last, in the event that the sought library is not picked up in any of the
#    other locations.
#
# Note that ERL_LIBS will find *either* an ebin subdir *or* lib subdir

# Find application ebin directories in lib if lib exists.

find_libs () {
    if [ -d "$1" ]; then
	echo $(find "$1" -maxdepth 1 -mindepth 1 -exec printf "%s:" {} \;)
    fi
}

# The following works for rebar and erl.mk
PROJ_LIBS=$(find_libs "./deps")
# The following works for rebar3
if [ -d "$REBAR_DEPS_DIR" ]; then
    # Use $REBAR_DEPS_DIR if set...
    R3_PROJ_LIBS=$(find_libs "$REBAR_DEPS_DIR")
else
    # ... otherwise provide a sensible default
    R3_PROJ_LIBS=$(find_libs "./_build/${REBAR_PROFILE:-default}/deps"):$(find_libs "./_build/${REBAR_PROFILE:-default}/lib")
fi
LFE_HOME_LIBS=$(find_libs "$HOME"/.lfe/lib)
ALL_LIBS="$LFE_ROOTDIR":"$ERL_LIBS":"$PROJ_LIBS""$R3_PROJ_LIBS""$LFE_HOME_LIBS"

ERL_LIBS="$ALL_LIBS" exec "$emulator" +B -boot start_clean $shebangs "-noshell" "-run" "lfescript" "start" "$@"
