# Eggshell runtime library
#
# Copyright (C) 2016  Patrick "P. J." McDermott
#
# This file is part of the Eggshell Linker.
#
# The Eggshell Linker is free software: you can redistribute it
# and/or modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation, either version 3 of
# the License, or (at your option) any later version.
#
# The Eggshell Linker is distributed in the hope that it will be
# useful, but WITHOUT ANY WARRANTY; without even the implied warranty
# of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with the Eggshell Linker  If not, see
# <http://www.gnu.org/licenses/>.

eshrtbegin()
{
	cat <<-'EOF'
__ESC="$(printf '\033.')"; __ESC="${__ESC%.}"
 __RS="$(printf '\036.')";  __RS="${__RS%.}"
 __US="$(printf '\037.')";  __US="${__US%.}"
__fn_stack=''
__fn_frame=''
__fn_name=''
__fn_tu=''
__fn_vars=''
__fn_var_vals=''
__fn=''
__prev_tu=''
__prev_vars=''
__var=''
__val=''
__init_funcs=''

__fn_stack_push()
{
	__fn_stack="${__fn_stack}${__RS}${__fn_frame}"
}

__fn_stack_peek()
{
	__fn_frame="${__fn_stack##*${__RS}}"
}

__fn_stack_pop()
{
	__fn_stack_peek
	__fn_stack="${__fn_stack%${__RS}*}"
}

__fn_frame_encode()
{
	# RS and US in frame variable values must be encoded.
	__fn_var_vals="$(printf '%s' "${__fn_var_vals}" | sed "
		s|${__ESC}|${__ESC}0|g;
		s|${__RS}|${__ESC}1|g; s|${__US}|${__ESC}2|g;
		")"
	__fn_frame="${__fn_name}${__US}${__fn_tu}"
	__fn_frame="${__fn_frame}${__US}${__fn_vars}${__US}${__fn_var_vals}"
}

__fn_frame_decode()
{
	__fn_name="${__fn_frame%%${__US}*}"
	__fn_frame="${__fn_frame#*${__US}}"
	__fn_tu="${__fn_frame%%${__US}*}"
	__fn_frame="${__fn_frame#*${__US}}"
	__fn_vars="${__fn_frame%%${__US}*}"
	__fn_var_vals="${__fn_frame#*${__US}}"
	__fn_var_vals="$(printf '%s' "${__fn_var_vals}" | sed "
		s|${__ESC}0|${__ESC}|g;
		s|${__ESC}1|${__RS}|g; s|${__ESC}2|${__US}|g;
		")"
}

__fn_ctxsw()
{
	unset IFS
	case "${__prev_tu}" in
		${__fn_tu});;
		?*)
			# Unset static variables and functions from previous TU.
			case "$(eval "printf '%s' \
					\"\${__${__prev_tu}_static_vars}\"")" \
					in ?*)
				eval "unset \${__${__prev_tu}_static_vars}"
			;; esac
			for __fn in $(eval printf '%s' \
					"\"\${__${__prev_tu}_static_fns}\""); do
				unset -f "${__fn%:*}"
			done
	;; esac
	case "${__fn_tu}" in
		${__prev_tu});;
		?*)
			# Set static variables and function for the current TU.
			eval "$(eval printf '%s' "\"$(eval printf '%s' \
				"'\${__${__fn_tu}_static_var_vals}'")\"")"
			for __fn in $(eval printf '%s' \
					"\"\${__${__fn_tu}_static_fns}\""); do
				eval "${__fn%:*}() { ${__fn#*:}; }"
			done
	;; esac
	case "${__prev_vars}" in ?*)
		unset ${__prev_vars}
	;; esac
	eval "${__fn_var_vals}"
}

__fn_update_vars()
{
	for __var in ${__fn_vars}; do
		__val="$(eval "printf '%s' \"\${${__var}}\"" | \
			sed "s|'|'\\\\''|g;")"
		__fn_var_vals="${__fn_var_vals} ${__var}='${__val}'"
	done
}

__fn_start()
{
	# Old state.
	__prev_tu="${__fn_tu}"
	__prev_vars="${__fn_vars}"

	# Update local vars in stack.
	__fn_stack_pop
	__fn_vars="${__prev_vars}"
	__fn_update_vars
	__fn_frame_encode
	__fn_stack_push

	# New state.
	__fn_name="${2}"
	__fn_tu="${1}"
	__fn_vars=
	__fn_var_vals=
	__fn_frame_encode
	__fn_stack_push

	# Switch.
	__fn_ctxsw
}

__fn_end()
{
	# Old state.
	__fn_stack_pop
	__fn_frame_decode
	__prev_tu="${__fn_tu}"
	__prev_vars="${__fn_vars}"

	# New state.
	__fn_stack_peek
	__fn_frame_decode

	# Switch.
	__fn_ctxsw
}

__tu_end()
{
	# Save TU static vars.
	for __var in $(eval "printf '%s' \"\${__${__tu}_static_vars}\""); do
		__val="$(eval "printf '%s' \"\${${__var}}\"" | \
			sed "s|'|'\\\\''|g")"
		eval "__${__tu}_static_var_vals=\"\${__${__tu}_static_var_vals}\
			${__var}='\${__val}'\""
		unset ${__var}
	done

	__tu=''
}

__stack_trace()
{
	IFS="${__RS}"
	for __fn_frame in ${__fn_stack#${__RS}}; do
		printf '%s\n' "${__fn_frame%%${__US}*}"
	done
}

__local()
{
	for __var in "${@}"; do
		case "${__var}" in
			*=*)
				__val="${__var#*=}"
				__var="${__var%%=*}"
				;;
			*)
				__val=''
				;;
		esac
		case "${__var}" in [!A-Za-z_]* | *[!0-9A-Za-z_]*)
			printf 'Syntax error: %s %s\n' \
				'illegal static variable name:' "${__var}" >&2
			exit 1
		;; esac
		eval "${__var}=\${__val}"
		__fn_vars="${__fn_vars} ${__var}"
	done
}

static()
{
	case "${__tu}" in '')
		printf 'Error: Cannot declare static variables in functions' >&2
		exit 1
	;; esac
	for __var in "${@}"; do
		case "${__var}" in
			*=*)
				__val="${__var#*=}"
				__var="${__var%%=*}"
				;;
			*)
				__val=''
				;;
		esac
		case "${__var}" in [!A-Za-z_]* | *[!0-9A-Za-z_]*)
			printf 'Syntax error: %s %s\n' \
				'illegal static variable name:' "${__var}" >&2
			exit 1
		;; esac
		eval "${__var}=\${__val}"
		eval "__${__tu}_static_vars=\"\${__${__tu}_static_vars} \
			${__var}\""
	done
}

__init()
{
	__init_funcs="${__init_funcs} ${1}"
}
EOF
}

eshrtend()
{
	local entry="${1}"
	shift 1

	cat <<-'EOF'
for __func in ${__init_funcs}; do
	${__func}
done
EOF
	printf '%s "${@}"\n' "${entry_point}"
}