# Eggshell parser
#
# 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/>.

ptrace=false

#
# Function tracing
#

ptrace_begn()
{
	local fn="${1}"
	shift 1

	if ${ptrace}; then
		printf 'TRACE: BEGN %s()\n' "${fn}" >&2
	fi
}

ptrace_pass()
{
	local fn="${1}"
	shift 1

	if ${ptrace}; then
		printf 'TRACE: PASS %s()\n' "${fn}" >&2
	fi
}

ptrace_fail()
{
	local fn="${1}"
	shift 1

	if ${ptrace}; then
		printf 'TRACE: FAIL %s()\n' "${fn}" >&2
	fi
}

#
# Parser
#

complete_command()
{
	linebreak
	if list; then
		separator
		return 0
	fi
	return 1
}

list()
{
	ptrace_begn list
	if and_or; then
		while separator && and_or; do
			:
		done
		ptrace_pass list
		return 0
	fi
	ptrace_fail list
	return 1
}

and_or()
{
	ptrace_begn and_or
	if pipeline; then
		while accept T_AND_IF || accept T_OR_IF; do
			if ! linebreak || ! pipeline; then
				ptrace_fail and_or
				return 1
			fi
		done
		ptrace_pass and_or
		return 0
	fi
	ptrace_fail and_or
	return 1
}

pipeline()
{
	ptrace_begn pipeline
	accept T_BANG
	if pipe_sequence; then
		ptrace_pass pipeline
		return 0
	fi
	ptrace_fail pipeline
	return 1
}

pipe_sequence()
{
	ptrace_begn pipe_sequence
	if command; then
		while accept T_PIPE; do
			if ! linebreak || ! command; then
				ptrace_fail pipe_sequence
				return 1
			fi
		done
		ptrace_pass pipe_sequence
		return 0
	fi
	ptrace_fail pipe_sequence
	return 1
}

command()
{
	ptrace_begn command
	if simple_command; then
		ptrace_pass command
		return 0
	elif compound_command; then
		redirect_list
		ptrace_pass command
		return 0
	fi
	ptrace_fail command
	return 1
}

compound_command()
{
	ptrace_begn compound_command
	if brace_group; then
		ptrace_pass compound_command
		return 0
	elif subshell; then
		ptrace_pass compound_command
		return 0
	elif for_clause; then
		ptrace_pass compound_command
		return 0
	elif case_clause; then
		ptrace_pass compound_command
		return 0
	elif if_clause; then
		ptrace_pass compound_command
		return 0
	elif while_clause; then
		ptrace_pass compound_command
		return 0
	elif until_clause; then
		ptrace_pass compound_command
		return 0
	fi
	ptrace_fail compound_command
	return 1
}

subshell()
{
	ptrace_begn subshell
	if accept T_LPAREN && compound_list && expect T_RPAREN; then
		ptrace_pass subshell
		return 0
	fi
	ptrace_fail subshell
	return 1
}

compound_list()
{
	ptrace_begn compound_list
	newline_list
	if term; then
		separator
		ptrace_pass compound_list
		return 0
	fi
	ptrace_fail compound_list
	return 1
}

term()
{
	ptrace_begn term
	if and_or; then
		while separator; do
			and_or
		done
		ptrace_pass term
		return 0
	fi
	ptrace_fail term
	return 1
}

for_clause()
{
	ptrace_begn for_clause
	if accept T_FOR; then
		if expect T_NAME && linebreak; then
			if accept T_IN; then
				wordlist
				if ! sequential_sep; then
					ptrace_fail for_clause
					return 1
				fi
			fi
			if do_group; then
				ptrace_pass for_clause
				return 0
			fi
		fi
	fi
	ptrace_fail for_clause
	return 1
}

wordlist()
{
	ptrace_begn wordlist
	if accept T_WORD; then
		while accept T_WORD; do :; done
		ptrace_pass wordlist
		return 0
	fi
	ptrace_fail wordlist
	return 1
}

case_clause()
{
	if accept T_CASE; then
		if expect T_WORD && linebreak && expect T_IN && linebreak; then
			case_list || case_list_ns
			expect T_ESAC
			return 0
		fi
	fi
	return 1
}

case_list_ns()
{
	if case_list && case_item_ns; then
		return 0
	elif case_item_ns; then
		return 0
	fi
	return 1
}

case_list()
{
	if case_item; then
		while case_item; do
			:
		done
		return 0
	fi
	return 1
}

case_item_ns()
{
	accept T_LPAREN
	if pattern && expect RPAREN; then
		compound_list
		if linebreak; then
			return 0
		fi
	fi
	return 1
}

case_item()
{
	accept T_LPAREN
	if pattern && expect T_RPAREN; then
		if compound_list || linebreak; then
			if expect T_DSEMI && linebreak; then
				return 0
			fi
		fi
	fi
	return 1
}

pattern()
{
	if accept T_CMDNAME; then
		while accept T_PIPE; do
			expect T_WORD
		done
		return 0
	fi
	return 1
}

if_clause()
{
	if accept T_IF; then
		if compound_list && expect T_THEN && compound_list; then
			else_part
			expect T_FI
			return 0
		fi
	fi
	return 1
}

else_part()
{
	while accept T_ELIF; do
		if compound_list && expect T_THEN && compound_list; then
			continue
		fi
		return 1
	done
	if accept T_ELSE; then
		if compound_list; then
			return 0
		fi
	fi
	return 1
}

while_clause()
{
	if accept T_WHILE; then
		if compound_list && do_group; then
			return 0
		fi
	fi
	return 1
}

until_clause()
{
	if accept T_UNTIL; then
		if compound_list && do_group; then
			return 0
		fi
	fi
	return 1
}

function_body()
{
	ptrace_begn function_body
	inject T_LBRACE
	inject T_FN_START
	if compound_command; then
		inject T_SEMI
		inject T_FN_END
		inject T_RBRACE
		ptrace_pass function_body
		return 0
	fi
	ptrace_fail function_body
	return 1
}

brace_group()
{
	ptrace_begn brace_group
	if accept T_LBRACE && compound_list && expect T_RBRACE; then
		ptrace_pass brace_group
		return 0
	fi
	ptrace_fail brace_group
	return 1
}

do_group()
{
	ptrace_begn do_group
	if accept T_DO && compound_list && expect T_DONE; then
		ptrace_pass do_group
		return 0
	fi
	ptrace_fail do_group
	return 1
}

simple_command()
{
	ptrace_begn simple_command
	if accept T_LOCAL || accept T_RETURN; then
		cmd_suffix
		ptrace_pass simple_command
		return 0
	fi
	accept T_STATIC
	if cmd_prefix; then
		if cmd_word; then
			cmd_suffix
		fi
		ptrace_pass simple_command
		return 0
	elif accept T_FNAME; then
		if accept T_LPAREN; then
			expect T_RPAREN
			if linebreak && function_body; then
				ptrace_pass simple_command
				return 0
			fi
		else
			cmd_suffix
			ptrace_pass simple_command
			return 0
		fi
	elif cmd_name; then
		cmd_suffix
		ptrace_pass simple_command
		return 0
	fi
	ptrace_fail simple_command
	return 1
}

cmd_name()
{
	ptrace_begn cmd_name
	# TODO: Assignment
	if accept T_CMDNAME; then
		ptrace_pass cmd_name
		return 0
	fi
	ptrace_fail cmd_name
	return 1
}

cmd_word()
{
	ptrace_begn cmd_word
	# TODO: Assignment
	if accept T_WORD; then
		ptrace_pass cmd_word
		return 0
	fi
	ptrace_fail cmd_word
	return 1
}

cmd_prefix()
{
	ptrace_begn cmd_prefix
	if io_redirect || accept T_ASSIGNMENT_WORD; then
		while io_redirect || accept T_ASSIGNMENT_WORD; do
			:
		done
		ptrace_pass cmd_prefix
		return 0
	fi
	ptrace_fail cmd_prefix
	return 1
}

cmd_suffix()
{
	ptrace_begn cmd_suffix
	if io_redirect || accept T_WORD; then
		while io_redirect || accept T_WORD; do
			:
		done
		ptrace_pass cmd_suffix
		return 0
	fi
	ptrace_fail cmd_suffix
	return 1
}

redirect_list()
{
	ptrace_begn redirect_list
	if io_redirect; then
		while io_redirect; do
			:
		done
		ptrace_pass redirect_list
		return 0
	fi
	ptrace_fail redirect_list
	return 1
}

io_redirect()
{
	ptrace_begn io_redirect
	accept T_IO_NUMBER
	if io_file || io_here; then
		ptrace_pass io_redirect
		return 0
	fi
	ptrace_fail io_redirect
	return 1
}

io_file()
{
	if accept T_LESS || accept T_LESSAND || accept T_GREAT || \
			accept T_GREATAND || accept T_DGREAT || \
			accept T_LESSGREAT || accept T_CLOBBER; then
		if filename; then
			return 0
		fi
	fi
	return 1
}

filename()
{
	if accept T_WORD; then
		return 0
	fi
	return 1
}

io_here()
{
	if accept T_DLESS || accept T_DLESSDASH; then
		if here_end; then
			return 0
		fi
	fi
	return 1
}

here_end()
{
	if accept T_WORD; then
		return 0
	fi
	return 1
}

newline_list()
{
	if accept T_NEWLINE; then
		while accept T_NEWLINE; do
			:
		done
		return 0
	fi
	return 1
}

linebreak()
{
	newline_list
	return 0
}

separator_op()
{
	if accept T_AND || accept T_SEMI; then
		return 0
	fi
	return 1
}

separator()
{
	if separator_op && linebreak; then
		return 0
	elif newline_list; then
		return 0
	fi
	return 1
}

sequential_sep()
{
	ptrace_begn sequential_sep
	if accept T_SEMI; then
		if linebreak; then
			ptrace_pass sequential_sep
			return 0
		fi
	elif newline_list; then
		ptrace_pass sequential_sep
		return 0
	fi
	ptrace_fail sequential_sep
	return 1
}