# Eggshell runtime library
#
# Copyright (C) 2016  Patrick "P. J." McDermott
#
# This file is part of the Eggshell Compiler.
#
# The Eggshell Compiler 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 Compiler 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 Compiler  If not, see
# <http://www.gnu.org/licenses/>.

use nostack

__ESC="$(printf '\033.')"; __ESC="${__ESC%.}"
 __RS="$(printf '\036.')";  __RS="${__RS%.}"
 __US="$(printf '\037.')";  __US="${__US%.}"
__sp=0
__fn_name=''
__fn_tu=''
__fn_vars=''
__fn=''
__prev_tu=''
__prev_vars=''
__var=''
__val=''
__fn_frame=0
__paramc=''
__paramv=''
__param=''
__i=0
__err=false
__fn_begin_hooks=''
__fn_end_hooks=''
__init_funcs=''

__sp_inc()
{
	__sp=$((${__sp} + 1))
}

__sp_dec()
{
	__sp=$((${__sp} - 1))
}

__frame_set()
{
	eval "__frame_${__sp}_name=\${__fn_name}"
	eval "__frame_${__sp}_tu=\${__fn_tu}"
	eval "__frame_${__sp}_vars=\${__fn_vars}"
}

__frame_get()
{
	eval "__fn_name=\${__frame_${__sp}_name}"
	eval "__fn_tu=\${__frame_${__sp}_tu}"
	eval "__fn_vars=\${__frame_${__sp}_vars}"
}

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

__fn_update_vars()
{
	unset IFS
	for __var in ${__fn_vars}; do
		eval "__fn_vars_${__sp}_${__var}=\${${__var}}"
	done
}

__fn_start()
{
	# Hooks.
	unset IFS
	for __fn in ${__fn_begin_hooks}; do
		${__fn} ${2}
	done

	# Update local vars in stack.
	__fn_update_vars
	__frame_set

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

	# Set stack pointer.
	__sp_inc

	# New state.
	__fn_name="${2}"
	__fn_tu="${1}"
	__fn_vars=
	__frame_set

	# Switch.
	__fn_ctxsw
}

__fn_end()
{
	# Hooks.
	unset IFS
	for __fn in ${__fn_end_hooks}; do
		${__fn} ${__fn_name}
	done

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

	# Set stack pointer.
	__sp_dec

	# New state.
	__frame_get

	# Switch.
	__fn_ctxsw
}

__tu_end()
{
	# Save TU static vars.
	unset IFS
	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()
{
	__fn_frame=0
	while [ ${__fn_frame} -le ${__sp} ]; do
		eval "printf '%s\n' \"\${__frame_${__fn_frame}_name}\""
		__fn_frame=$((${__fn_frame} + 1))
	done
}

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

__static()
{
	case "${__tu}" in '')
		printf 'Error: Cannot declare static variables in functions' >&2
		exit 1
	;; esac
	unset IFS
	for __var in "${@}"; 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
}

__check_args()
{
	__fn="${1}"
	__paramc="${2}"
	__paramv="${3}"
	shift 3

	if [ ${#} -ne ${__paramc} ]; then
		printf 'Error: Incorrect number of arguments to function %s\n' \
			"${__fn_name}()" >&2
		exit 1
	fi
	unset IFS
	__i=0
	for __param in ${__paramv}; do
		__i=$((${__i} + 1))
		__err=false
		case "${__param%:*}" in
			'bool')
				case "${1}" in 'true'|'false');; *) __err=true;;
				esac
				;;
			'int')
				case "${1}" in *[!0-9]*) __err=true;; esac
				;;
		esac
		if ${__err}; then
			printf 'Error: Argument %d of %s() %s (%s %s)\n' \
				${__i} "${__fn_name}" 'has incorrect type' \
				'expecting' "${__param%:*}" >&2
			exit 1
		else
			__local "${__param#*:}=${1}"
		fi
		shift 1
	done
}

__fn_begin_hook()
{
	__fn_begin_hooks="${__fn_begin_hooks} ${1}"
}

__fn_end_hook()
{
	__fn_end_hooks="${__fn_end_hooks} ${1}"
}

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