#!/bin/sh
# vim:ft=sh:ts=4:sw=4:noexpandtab
set -e

# Configured variables #####################################################
# Described in following format:
# name:initial value:type:if exported to makefile:if exported to C header
# Where type can be just a string (in C and shell in "") or plain. None implies
# plain.
CNFS="CBUILD:::F:F
CHOST:::F:F
DEBUG:no::T:F
CPREFIX:::T:F
CHOST::string:T:F
CCX:g++::T:F
CFLAGS::string:T:F
LFLAGS::string:T:F"
############################################################################
# TODO add options to fine tune installation directories

print_help() {
	echo "Usage: ./configure [OPTION]..."
	echo "GEML configuration script. Execute this script to configure project"
	echo "and prepare it for building."
	echo
	echo "  --help, -h              Give this help list"
	echo "  --debug, -d             Enable development features."
	echo "  --release, -r           Disable development features for project."
	echo "  --dep-check             Force depencency check."
	echo "  --build=CBUILD          System compiler prefix on which project is"
	echo "                          built."
	echo "  --host=CHOST            Compiler prefix for system program and"
	echo "                          libraries will run on."
	echo
	echo "Environment variables:"
	echo "  CPREFIX                 Compilation tools prefix."
	echo "  CXX                     C++ compiler command."
	echo "  CFLAGS                  C++ compiler flags."
	echo "  LDFLAGS                 C++ Linker flags."
}

CONFIG_FILE=.config
CONFIGURED_FILE=.configured # TODO

# Backup variables from environment
ENVVARS="CPREFIX CXX CFLAGS LDFLAGS"
for E in $ENVVARS; do
	eval "[ -n \"\${$E+y}\" ]" && eval "BACKUP_$E=\$$E"
done

# Load default configuration if variable not set from environment
eval `echo "$CNFS" | sed -ne 's/^\([^:]*\):\([^:]*\).*$/\1=\2/p'`

# Load existing configuration
if [ -f "$CONFIG_FILE" ]; then
	. ./"$CONFIG_FILE"
fi

# Functions used for arguments parsing. Handles both --*=* and --* * arguments.
# First arguments is option name. Second is $1 and third $2
set_options() {
	if [[ "$2" == --*=* ]]; then
		VAL="$(echo "$2" | sed 's/--[^=]*=//')"
	else
		VAL="$3"
	fi
}

# Requested operation.
# c - Configure, default configuration behavior
# m - Prints output for Makefile
# h - Prints C header file
OP=c

# Parse arguments
while [ "$#" -gt 0 ]; do
	case $1 in
		-h|--help)
			print_help
			exit 0
			;;
		-d|--debug)
			DEBUG=yes
			;;
		-r|--release)
			DEBUG=no
			;;
		--host=*)
			CHOST=${1#--host=}
			shift
			;;
		--op-makefile)
			OP=m
			;;
		--op-h)
			OP=h
			;;
		*)
			echo Warning: Unknown option $1 1>&2
			;;
	esac
	shift
done

# Recover from enviroment variables
for E in $ENVVARS; do
	eval "[ -n \"\${BACKUP_$E+y}\" ]" && eval "$E=\$BACKUP_$E"
done

# Basically save configuration to file
configure() {
	echo "# linux-lcd configuration file" > "$CONFIG_FILE"
	echo "# Please do not edit this file directly." >> "$CONFIG_FILE"
	echo "$CNFS" | while read L; do
		NAME=`echo "$L" | grep -o -E '^[^:]*'`
		eval "VALUE=\"\$$NAME\""
		if [ "`echo $L | awk -F ':' '{ print $3 }'`" = "string" ]; then
			echo "$NAME=\"$VALUE\"" >> "$CONFIG_FILE"
		else
			echo "$NAME=$VALUE" >> "$CONFIG_FILE"
		fi
	done
	echo "Configuration written to \"$CONFIG_FILE\""
}

makefile() {
	echo "$CNFS" | while read L; do
		if [ `echo $L | awk -F ':' '{ print $4 }'` != "T" ]; then
			continue
		fi
		NAME=`echo "$L" | grep -o -E '^[^:]*'`
		eval "VALUE=\$$NAME"
		echo "$NAME := $VALUE"
	done
}

cheader() {
	echo "$CNFS" | while read L; do
		if [ `echo $L | awk -F ':' '{ print $5 }'` != "T" ]; then
			continue
		fi
		NAME=`echo "$L" | grep -o -E '^[^:]*'`
		eval "VALUE=\$$NAME"
		if [ "`echo $L | awk -F ':' '{ print $3 }'`" = "string" ]; then
			echo "#define $NAME \"$VALUE\""
		else
			echo "#define $NAME $VALUE"
		fi
	done
}

case $OP in
	c)
		configure
		;;
	m)
		makefile
		;;
	h)
		cheader
		;;
esac