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

# 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 in "") or plain. None implies plain.
CNFS="PREFIX:/usr/local:string:T:F
EPREFIX:/usr/local:string:T:F
DEBUG:no::T:F
CPREFIX:::T:F
CC:cc::T:F
CFLAGS:::T:F
LFLAGS:::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 for this machine."
	echo "  --prefix=PREFIX         Set PREFIX as installation prefix for"
	echo "                          architecture independent files."
	echo "                          In default /usr/local"
	echo "  --exec-prefix=EPREFIX   Set EPREFIX as installation prefix for"
	echo "                          architecture dependent files."
	echo "                          In default PREFIX"
	echo
	echo "Environment variables:"
	echo "  CPREFIX                 Compilation tools prefix."
	echo "  CC                      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 CC 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

# Requested operation.
# c - Configure, default configuration behavior
# m - Prints output for Makefile
# h - Prints C header file (machine validation is skipped)
OP=c

# Parse arguments
while [ "$#" -gt 0 ]; do
	case $1 in
		-h|--help)
			print_help
			exit 0
			;;
		--prefix)
			PREFIX=$2
			[ -z "$EPREFIX_USER" ] && EPREFIX="$PREFIX"
			shift
			;;
		--prefix=*)
			PREFIX=${1#--prefix=}
			[ -z "$EPREFIX_USER" ] && EPREFIX="$PREFIX"
			;;
		--exec-prefix)
			EPREFIX=$2
			EPREFIX_USER=y
			shift
			;;
		--exec-prefix=*)
			EPREFIX=${1#--exec-prefix=}
			EPREFIX_USER=y
			;;
		-d|--debug)
			DEBUG=yes
			;;
		-r|--release)
			DEBUG=no
			;;
		--op-makefile)
			OP=m
			;;
		--op-h)
			OP=h
			;;
		*)
			echo Unknown option $1 1>&2
			exit 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 "# GEML 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"
		echo "$NAME=$VALUE" >> "$CONFIG_FILE"
	done
	echo "Configuration written to \"$CONFIG_FILE\""
}

# Generate Makefile and configure them if they doesn't exists in PWD
doext() {
	if [ -f "Makefile" ] || [ -f configure ]; then
		return
	fi
	GEMLDIR=`dirname "$0"`

	echo "# This is external Makefile for GEML." > Makefile
	echo >> Makefile
	echo "GEML_PATH = $GEMLDIR" >> Makefile
	echo >> Makefile
	echo "MAKEARGS := -C \"\$(GEML_PATH)\"" >> Makefile
	echo "MAKEARGS += O=\"\$(shell pwd)\"" >> Makefile
	echo >> Makefile
	echo "MAKEFLAGS += --no-print-directory" >> Makefile
	echo >> Makefile
	echo "Q ?= @" >> Makefile
	echo ".PHONY: all \$(MAKECMDGOALS)" >> Makefile
	echo "all \$(MAKECMDGOALS):" >> Makefile
	echo "	\$(Q)\$(MAKE) \$(MAKEARGS) \$@" >> Makefile

	echo Created local Makefile

	echo "# This is external configure script for GEML." > configure
	echo "GEML_PATH=$GEMLDIR" >> configure
	echo "cd \$(dirname \$0)" >> configure
	echo "\$GEML_PATH/configure \$@" >> configure
	chmod +x configure

	echo Created local configure script
}

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
}

validate() {
	echo -n
	# TODO check dependencies and programs
}

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