#!/usr/bin/env sh
# simple and flexible configure script for people who don't like to waste time
# licensed to the public domain

set -e

mkf=config.mk
di='di'
imports="$di"
objs='esvapi.o util.o initial.o'
srcs='esvapi.d util.d initial.d'

# utility functions

present () {
	command -v "$1" 1>/dev/null 2>/dev/null
}
throw () {
	>&2 printf "%s: %s\n" "$(basename "$0")" "$1"
	exit 1
}
using () {
	>&2 printf "using %s\n" "$1"
}

# generators

## D compiler
gen_DC () {
	if [ -n "$dc" ]; then
		using "$dc"
		return 0
	fi
	if present ldc2; then
		dc=ldc2
		dcname="$dc"
	elif present dmd; then
		dc=dmd
		dcname="$dc"
	else
		throw "D compiler not found; install LDC or DMD"
	fi

	using "$dc"
}

## flags used in the compilation step
gen_CFLAGS () {
	if [ -z "$debug" ]; then
		case "$dcname" in
			ldc2) cflags="-Oz";;
			 dmd) cflags="-O";;
		 esac
	else
		cflags="-g"
		case "$dcname" in
			ldc2) cflags="$cflags -O0 -d-debug";;
			 dmd) cflags="$cflags -debug";;
		esac
	fi
	[ -n "$unittest" ] && cflags="$cflags -unittest -main"

	for flag in $cflags; do
		using "$flag"
	done
}

## flags used in the linking step
gen_LDFLAGS () {
	if [ "$dcname" = ldc2 ]; then
		if present ld.lld; then
			ldflags="-linker=lld"
		elif present ld.gold; then
			ldflags="-linker=gold"
		fi
	fi
	if [ -z "$debug" ]; then
		if [ -n "$ldflags" ]; then ldflags="$ldflags "; fi
		ldflags="$ldflags-L--gc-sections"
	fi

	for flag in $ldflags; do
		using "$flag"
	done
}

# command line interface

while getopts c:dhrt ch; do
	case "$ch" in
		c)
			dcname="$(basename "$OPTARG")"
			case "$dcname" in
				ldc2) dc="$OPTARG" ;;
				dmd)  dc="$OPTARG" ;;
				*) throw "unknown D compiler '$dcname' specified (valid options: ldc2, dmd)" ;;
			esac
			;;
		d) debug=1 ;;
		r) unset debug ;;
		t) unittest=1; debug=1 ;;
		h)
			cat <<EOF
configure: create an optimised makefile for the current environment

options:
  -c: force use of a particular compiler (dmd or ldc2)
  -d: build in debug mode, with debug symbols and statements enabled
  -r: build in release mode with optimisation flags enabled (default)
  -t: build an executable to run unit tests (implies -d)
  -h: show this help message
EOF
			exit 0
			;;
		'?') exit 1 ;;
		:) exit 1 ;;
	esac
done

# creating the makefile

gen_DC
gen_CFLAGS
gen_LDFLAGS

for directory in $imports; do
	mkdir -p "$directory"
	Iflags="$(printf '%s -I%s' "$Iflags" "$directory" | xargs)"
done

for src in $srcs; do
	! (echo "$src" | grep -Eq '\.d$') \
		&& throw "$src: invalid source file extension"
	[ -t 2 ] && printf ' (DI) %s        \r' "$src" 1>&2
	"$dc" -o- -op -H -Hd="$di" "$src"
done

rm -f "$mkf"

{
	printf '# begin generated definitions
_DC = %s
_CFLAGS = %s
_LDFLAGS = %s
' "$dc" "$(echo "$cflags $Iflags" | xargs)" "$ldflags"

	## generate obj list
	printf '_OBJS ='
	for obj in $objs; do
		printf ' %s' "$obj"
	done
	printf '\n# end generated definitions\n'

	## generate dependency list
	printf '\n# begin generated dependencies\n'
	i=1
	for obj in $objs; do
		src="$(printf '%s' "$srcs" | awk '{print $'"$i"'}')"
		[ -t 2 ] && printf ' (MK) %s        \r' "$src" 1>&2
		"$dc" -o- -makedeps "$src"
		i="$((i + 1))"
	done
	unset i
	printf '# end generated dependencies\n'
} >>"$mkf"