$ // This file is part of NIT ( http://www.nitlanguage.org ).
$ //
$ // Copyright 2008 Jean Privat <jean@pryen.org>
$ // Based on algorithms developped for ( http://www.sablecc.org/ ).
$ //
$ // Licensed under the Apache License, Version 2.0 (the "License");
$ // you may not use this file except in compliance with the License.
$ // You may obtain a copy of the License at
$ //
$ //     http://www.apache.org/licenses/LICENSE-2.0
$ //
$ // Unless required by applicable law or agreed to in writing, software
$ // distributed under the License is distributed on an "AS IS" BASIS,
$ // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
$ // See the License for the specific language governing permissions and
$ // limitations under the License.

$ template make_parser()

# State of the parser automata as stored in the parser stack.
private class State
	# The internal state number
	readable writable var _state: Int

	# The node stored with the state in the stack
	readable writable var _nodes: nullable Object

	init(state: Int, nodes: nullable Object)
	do
		_state = state
		_nodes = nodes
	end
end

class Parser
special ParserTable
	# Associated lexer
	var _lexer: Lexer

	# Stack of pushed states and productions
	var _stack: Array[State]

	# Position in the stack
	var _stack_pos: Int

	# Create a new parser based on a given lexer
	init(lexer: Lexer)
	do
		_lexer = lexer
		_stack = new Array[State]
		_stack_pos = -1
		build_goto_table
		build_action_table
		build_reduce_table
	end

	# Do a transition in the automata
	private fun go_to(index: Int): Int
	do
		var state = state
		var table = _goto_table[index]
		var low = 1
		var high = table.length/2 - 1

		while low <= high do
			var middle = (low + high) / 2
			var subindex = middle * 2

			if state < table[subindex] then
				high = middle - 1
			else if state > table[subindex] then
				low = middle + 1
			else
				return table[subindex + 1]
			end
		end

		return table[1] # Default value
	end

	# Push someting in the state stack
	private fun push(numstate: Int, list_node: nullable Object)
	do
		var pos = _stack_pos + 1
		_stack_pos = pos
		if pos < _stack.length then
			var state = _stack[pos]
			state.state = numstate
			state.nodes = list_node
		else
			_stack.push(new State(numstate, list_node))
		end
	end

	# The current state
	private fun state: Int
	do
		return _stack[_stack_pos].state
	end

	# Pop something from the stack state
	private fun pop: nullable Object
	do
		var res = _stack[_stack_pos].nodes
		_stack_pos = _stack_pos -1
		return res
	end

	# Build and return a full AST.
	fun parse: Start
	do
		push(0, null)

		var lexer = _lexer
		loop
			var token = lexer.peek
			if token isa PError then
				return new Start(null, token)
			end

			var index = token.parser_index
			var table = _action_table[state]
			var action_type = table[1]
			var action_value = table[2]

			var low = 1
			var high = table.length/3 - 1

			while low <= high do
				var middle = (low + high) / 2
				var subindex = middle * 3

				if index < table[subindex] then
					high = middle - 1
				else if index > table[subindex] then
					low = middle + 1
				else
					action_type = table[subindex + 1]
					action_value = table[subindex + 2]
					high = low -1 # break
				end
			end

			if action_type == 0 then # SHIFT
				push(action_value, lexer.next)
			else if action_type == 1 then # REDUCE
				_reduce_table[action_value].action(self)
			else if action_type == 2 then # ACCEPT
				var node2 = lexer.next
				assert node2 isa EOF
				var node1 = pop
				assert node1 isa ${/parser/prods/prod/@ename}
				var node = new Start(node1, node2)
				(new ComputeProdLocationVisitor).enter_visit(node)
				return node
			else if action_type == 3 then # ERROR
				var node2 = new PError.init_error("Syntax error: unexpected token.", token.location)
				var node = new Start(null, node2)
				return node
			end
			if false then break # FIXME remove once unreach loop exits are in c_src
		end
		abort # FIXME remove once unreach loop exits are in c_src
	end

	var _reduce_table: Array[ReduceAction]
	private fun build_reduce_table
	do
		_reduce_table = new Array[ReduceAction].with_items(
$ foreach {rules/rule}
			new ReduceAction@index[-sep ','-]
$ end foreach
		)
	end
end

redef class Prod
	# Location on the first token after the start of a production
	# So outside the production for epilon production
	var _first_location: nullable Location

	# Location of the last token before the end of a production
	# So outside the production for epilon production
	var _last_location: nullable Location
end

# Find location of production nodes
# Uses existing token locations to infer location of productions.
private class ComputeProdLocationVisitor
special Visitor
	# Currenlty visited productions that need a first token
	var _need_first_prods: Array[Prod] = new Array[Prod]

	# Already visited epsilon productions that waits something after them
	var _need_after_epsilons: Array[Prod] = new Array[Prod]

	# Already visited epsilon production that waits something before them
	var _need_before_epsilons: Array[Prod] = new Array[Prod]

	# Location of the last visited token in the current production
	var _last_location: nullable Location = null

	redef fun visit(n: nullable PNode)
	do
		if n == null then
			return
		else if n isa Token then
			var loc = n.location
			_last_location = loc

			# Add a first token to productions that need one
			for no in _need_first_prods do
				no._first_location = loc
			end
			_need_first_prods.clear

			# Find location for already visited epsilon production that need one
			for no in _need_after_epsilons do
				# Epsilon production that is in the middle of a non-epsilon production
				# The epsilon production has both a token before and after it
				var endl = loc
				var startl = no._last_location
				no.location = new Location(endl.file, startl.line_end, endl.line_start, startl.column_end, endl.column_start)
			end
			_need_after_epsilons.clear
		else
			assert n isa Prod
			_need_first_prods.add(n)

			var old_last = _last_location
			_last_location = null
			n.visit_all(self)
			var endl = _last_location
			if endl == null then _last_location = old_last

			n._last_location = endl
			var startl = n._first_location
			if startl != null then
				# Non-epsilon production
				assert endl != null

				n.location = new Location(startl.file, startl.line_start, endl.line_end, startl.column_start, endl.column_end)

				for no in _need_before_epsilons do
					# Epsilon production that starts the current non-epsilon production
					#var startl = n.location
					no.location = new Location(startl.file, startl.line_start, startl.line_start, startl.column_start, startl.column_start)
				end
				_need_before_epsilons.clear

				for no in _need_after_epsilons do
					# Epsilon production that finishes the current non-epsilon production
					#var endl = n.location
					no.location = new Location(endl.file, endl.line_end, endl.line_end, endl.column_end, endl.column_end)
				end
				_need_after_epsilons.clear
			else
				# No first token means epsilon production (or "throw all my tokens" production)
				# So, it must be located it later
				if endl == null then
					# Epsilon production that starts a parent non-epsilon production
					_need_before_epsilons.add(n)
				else
					# Epsilon production in the middle or that finishes a parent non-epsilon production
					_need_after_epsilons.add(n)
				end
			end
		end
	end

	init do end
end

# Each reduca action has its own class, this one is the root of the hierarchy.
private abstract class ReduceAction
	fun action(p: Parser) is abstract
end

$ foreach {rules/rule}
private class ReduceAction@index
special ReduceAction
	redef fun action(p: Parser)
	do
					var node_list: nullable Object = null
$   foreach {action}
$   choose
$     when {@cmd='POP'}
					var ${translate(@result,"ABCDEFGHIJKLMNOPQRSTUVWXYZ","abcdefghijklmnopqrstuvwxyz")} = p.pop
$     end
$     when {@cmd='FETCHLIST'}
					var ${translate(@result,"ABCDEFGHIJKLMNOPQRSTUVWXYZ","abcdefghijklmnopqrstuvwxyz")} = ${translate(@from,"ABCDEFGHIJKLMNOPQRSTUVWXYZ","abcdefghijklmnopqrstuvwxyz")}
					assert ${translate(@result,"ABCDEFGHIJKLMNOPQRSTUVWXYZ","abcdefghijklmnopqrstuvwxyz")} isa Array[Object]
$     end
$     when {@cmd='FETCHNODE'}
					var ${translate(@result,"ABCDEFGHIJKLMNOPQRSTUVWXYZ","abcdefghijklmnopqrstuvwxyz")} = ${translate(@from,"ABCDEFGHIJKLMNOPQRSTUVWXYZ","abcdefghijklmnopqrstuvwxyz")}
					assert ${translate(@result,"ABCDEFGHIJKLMNOPQRSTUVWXYZ","abcdefghijklmnopqrstuvwxyz")} isa nullable @etype
$     end
$     when {@cmd='ADDNODE'}
					if ${translate(@node,"ABCDEFGHIJKLMNOPQRSTUVWXYZ","abcdefghijklmnopqrstuvwxyz")} != null then
						${translate(@tolist,"ABCDEFGHIJKLMNOPQRSTUVWXYZ","abcdefghijklmnopqrstuvwxyz")}.add(${translate(@node,"ABCDEFGHIJKLMNOPQRSTUVWXYZ","abcdefghijklmnopqrstuvwxyz")})
					end
$     end
$     when {@cmd='ADDLIST'}
#					if ${translate(@fromlist,"ABCDEFGHIJKLMNOPQRSTUVWXYZ","abcdefghijklmnopqrstuvwxyz")} != null then
						if ${translate(@tolist,"ABCDEFGHIJKLMNOPQRSTUVWXYZ","abcdefghijklmnopqrstuvwxyz")}.is_empty then
							${translate(@tolist,"ABCDEFGHIJKLMNOPQRSTUVWXYZ","abcdefghijklmnopqrstuvwxyz")} = ${translate(@fromlist,"ABCDEFGHIJKLMNOPQRSTUVWXYZ","abcdefghijklmnopqrstuvwxyz")}
						else
							${translate(@tolist,"ABCDEFGHIJKLMNOPQRSTUVWXYZ","abcdefghijklmnopqrstuvwxyz")}.append(${translate(@fromlist,"ABCDEFGHIJKLMNOPQRSTUVWXYZ","abcdefghijklmnopqrstuvwxyz")})
						end
#					end
$     end
$     when {@cmd='MAKELIST'}
					var ${translate(@result,"ABCDEFGHIJKLMNOPQRSTUVWXYZ","abcdefghijklmnopqrstuvwxyz")} = new Array[Object]
$     end
$     when {@cmd='MAKENODE'}
					var ${translate(@result,"ABCDEFGHIJKLMNOPQRSTUVWXYZ","abcdefghijklmnopqrstuvwxyz")}: nullable @etype = new @etype.init_${translate(@etype,"ABCDEFGHIJKLMNOPQRSTUVWXYZ","abcdefghijklmnopqrstuvwxyz")}(
$       foreach {arg}
$           if @null
						null[-sep ','-]
$           else
						${translate(.,"ABCDEFGHIJKLMNOPQRSTUVWXYZ","abcdefghijklmnopqrstuvwxyz")}[-sep ','-]
$           end
$       end foreach
					)
$     end
$     when {@cmd='RETURNNODE'}
$       if @null
					node_list = null
$       else
					node_list = ${translate(@node,"ABCDEFGHIJKLMNOPQRSTUVWXYZ","abcdefghijklmnopqrstuvwxyz")}
$       end
$     end
$     when {@cmd='RETURNLIST'}
					node_list = ${translate(@list,"ABCDEFGHIJKLMNOPQRSTUVWXYZ","abcdefghijklmnopqrstuvwxyz")}
$     end
$   end choose
$   end foreach
					p.push(p.go_to(@leftside), node_list)
	end
init do end
end
$ end foreach
$ end template

$ template make_parser_tables()
# Parser that build a full AST
abstract class ParserTable
	var _action_table: Array[Array[Int]]
	private fun build_action_table
	do
		_action_table = once [
$ foreach {parser_data/action_table/row}
			action_table_row${position()}[-sep ','-]
$ end foreach
	        ]
	end

$ foreach {parser_data/action_table/row}
	private fun action_table_row${position()}: Array[Int]
	do
		return [
$   foreach {action}
				@from, @action, @to[-sep ','-]
$   end foreach
			]
	end
$ end foreach

	var _goto_table: Array[Array[Int]]
	private fun build_goto_table
	do
		_goto_table = once [
$ foreach {parser_data/goto_table/row}
			[
$   foreach {goto}
				@from, @to[-sep ','-]
$   end foreach
			][-sep ','-]
$ end foreach
		]
	end

	init do end
end
$ end template