/*
 * \brief  Escape-sequence decoder
 * \author Norman Feske
 * \date   2011-06-06
 */

/*
 * Copyright (C) 2011-2012 Genode Labs GmbH
 *
 * This file is part of the Genode OS framework, which is distributed
 * under the terms of the GNU General Public License version 2.
 */

#ifndef _TERMINAL__DECODER_H_
#define _TERMINAL__DECODER_H_

#include <terminal/character_screen.h>

namespace Terminal {

	class Decoder
	{
		private:

			/**
			 * Return digit value of character
			 */
			static inline int digit(char c)
			{
				if (c >= '0' && c <= '9') return c - '0';
				return -1;
			}

			/**
			 * Return true if character is a digit
			 */
			static inline bool is_digit(char c)
			{
				return (digit(c) >= 0);
			}

			/**
			 * Return true if number starts with the specified digit
			 *
			 * \param digit  digit 0..9 to test for
			 */
			static inline bool starts_with_digit(int digit, int number)
			{
				for (; number > 9; number /= 10);
				return (number == digit);
			}

			/**
			 * Return number with the first digit removed
			 */
			static inline int remove_first_digit(int number)
			{
				int factor = 1;
				for (; number/factor > 9; factor *= 10);
				return number % factor;
			}

			/**
			 * Buffer used for collecting escape sequences
			 */
			class Escape_stack
			{
				public:

					struct Entry
					{
						enum { INVALID, NUMBER, CODE };

						int type;
						int value;
					};

					struct Number_entry : Entry
					{
						Number_entry(int number) { type = NUMBER, value = number; }
					};

					struct Code_entry : Entry
					{
						Code_entry(int code) { type = CODE, value = code; }
					};

					struct Invalid_entry : Entry
					{
						Invalid_entry() { type = INVALID; }
					};

				private:

					enum { MAX_ENTRIES = 16 };
					Entry _entries[MAX_ENTRIES];
					int   _index;

					void _dump() const
					{
						Genode::printf("--- escape stack follows ---\n");
						for (int i = 0; i < _index; i++) {
							int type = _entries[i].type;
							int value = _entries[i].value;
							Genode::printf("%s %d (0x%x '%c')\n",
							               type == Entry::INVALID ? " INVALID" :
							               type == Entry::NUMBER  ? " NUMBER "
							                                      : " CODE   ",
							               value, value, value);
						}
					}

				public:

					Escape_stack() : _index(0) { }

					void reset() { _index = 0; }

					void push(Entry const &entry)
					{
						if (_index == MAX_ENTRIES - 1) {
							Genode::printf("Error: escape stack overflow\n");
							_dump();
							reset();
							return;
						}
						_entries[_index++] = entry;
					}

					/**
					 * Return number of stack elements
					 */
					unsigned num_elem() const { return _index; }

					/**
					 * Return Nth stack entry
					 *
					 * 'index' is relative to the bottom of the stack.
					 */
					Entry operator [] (int index)
					{
						return (index <= _index) ? _entries[index] : Invalid_entry();
					}

			} _escape_stack;

			enum State {
				STATE_IDLE,
				STATE_ESC_SEQ,    /* read escape sequence */
				STATE_ESC_NUMBER  /* read number argument within escape sequence */
			} _state;

			Character_screen &_screen;

			int _number; /* current number argument supplied in escape sequence */

			void _append_to_number(char c)
			{
				_number = _number*10 + digit(c);
			}

			void _enter_state_idle()
			{
				_state = STATE_IDLE;
				_escape_stack.reset();
			}

			void _enter_state_esc_seq()
			{
				_state = STATE_ESC_SEQ;
				_escape_stack.reset();
			}

			void _enter_state_esc_number()
			{
				_state = STATE_ESC_NUMBER;
				_number = 0;
			}

			/**
			 * Try to handle single-element escape sequence
			 *
			 * \return true if escape sequence was handled
			 */
			bool _handle_esc_seq_1()
			{
				switch (_escape_stack[0].value) {
				case '7': return (_screen.sc(),  true);
				case 'c': return (_screen.ris(), true);
				case 'H': return (_screen.hts(), true);
				case 'M': return (_screen.ri(),  true);
				default:  return false;
				}
			}

			bool _handle_esc_seq_2()
			{
				switch (_escape_stack[0].value) {

				case '[':

					switch (_escape_stack[1].value) {
					case 'A': return (_screen.cuu1(), true);
					case 'C': return (_screen.cuf(1), true);
					case 'c': return (_screen.u9(),   true);
					case 'H': return (_screen.home(), true);
					case 'J': return (_screen.ed(),   true);
					case 'K': return (_screen.el(),   true);
					case 'L': return (_screen.il(1),  true);
					case 'M': return (_screen.dl(1),  true);
					case 'P': return (_screen.dch(1), true);
					case '@': return (_screen.ich(1), true);
					case 'R': return (_screen.cpr(),  true);
					default:  return false;
					}
					break;

				case ']':

					switch (_escape_stack[1].value) {
					case 'R': return (_screen.oc(), true);
					default : return false;
					}

				case 8:

					return (_escape_stack[1].value == 'A') && (_screen.rc(), true);

				default: return false;
				}
				return false;
			}

			bool _handle_esc_seq_3()
			{

				/*
				 * All three-element sequences have the form \E[<NUMBER><COMMAND>
				 */
				if ((_escape_stack[0].value != '[')
				 || (_escape_stack[1].type  != Escape_stack::Entry::NUMBER))
					return false;

				int  const p1      = _escape_stack[1].value;
				char const command = _escape_stack[2].value;

				switch (command) {
				case 'm':
					if (p1 < 30)
						return (_screen.sgr(p1), true);

					/* p1 starting with digit '3' -> set foreground color */
					if (starts_with_digit(3, p1))
						return (_screen.setaf(remove_first_digit(p1)), true);

					/* p1 starting with digit '4' -> set background color */
					if (starts_with_digit(4, p1))
						return (_screen.setab(remove_first_digit(p1)), true);

				case 'd': return (_screen.vpa(p1), true);
				case 'g': return (p1 == 3) && (_screen.tbc(), true);
				case 'G': return (_screen.hpa(p1), true);
				case 'h': return (p1 == 4) && (_screen.smir(), true);
				case 'K': return (p1 == 1) && (_screen.el1(),  true);
				case 'l': return (p1 == 4) && (_screen.rmir(), true);
				case 'L': return (_screen.il(p1), true);
				case 'M': return (_screen.dl(p1), true);
				case 'n': return (p1 == 6) && (_screen.u7(), true);
				case 'P': return (_screen.dch(p1), true);
				case '@': return (_screen.ich(p1), true);
				case 'X': return (_screen.ech(p1), true);
				case 'C': return (_screen.cuf(p1), true);

				default: return false;
				}
			}

			bool _handle_esc_seq_4()
			{
				/*
				 * All four-element escape sequences have the form
				 * \E[?<NUMBER><COMMAND>
				 */
				if ((_escape_stack[0].value != '[')
				 || (_escape_stack[1].value != '?')
				 || (_escape_stack[2].type  != Escape_stack::Entry::NUMBER))
				 	return false;

				int  const p1      = _escape_stack[2].value;
				char const command = _escape_stack[3].value;

				switch (command) {
				case 'l':
					if (p1 ==  7) return (_screen.rmam(),  true);
					if (p1 == 25) return (_screen.civis(), true);
					return false;
				case 'h':
					if (p1 ==  7) return (_screen.smam(),  true);
					if (p1 == 25) return (_screen.cnorm(), true);
					return false;
				case 'c':
					if (p1 == 0) return true; /* appended to cnorm */
					if (p1 == 1) return true; /* appended to civis */
					if (p1 == 6) return (_screen.u8(),    true);
					if (p1 == 8) return (_screen.cvvis(), true);
					return false;
				default: return false;
				}
			}

			bool _handle_esc_seq_5()
			{
				/*
				 * All five-element escape sequences have the form
				 * \E[<NUMBER1>;<NUMBER2><COMMAND>
				 */
				if ((_escape_stack[0].value != '[')
				 || (_escape_stack[1].type  != Escape_stack::Entry::NUMBER)
				 || (_escape_stack[2].value != ';')
				 || (_escape_stack[3].type  != Escape_stack::Entry::NUMBER))
					return false;

				int const p1      = _escape_stack[1].value;
				int const p2      = _escape_stack[3].value;
				int const command = _escape_stack[4].value;

				switch (command) {
				case 'r': return (_screen.csr(p1, p2), true);
				case 'H': return (_screen.cup(p1, p2), true);
				case 'm':
					if ((p1 == 39) && (p2 == 49)) return (_screen.op(),   true);
					if ((p1 ==  0) && (p2 == 10)) return (_screen.sgr(0), true);
					return false;
				case 'R': return (_screen.u6(p1, p2), true);
				default: return false;
				}
			}

		public:

			Decoder(Character_screen &screen)
			: _state(STATE_IDLE), _screen(screen), _number(0) { }

			void insert(unsigned char c)
			{
				switch (_state) {

				case STATE_IDLE:

					enum { ESC_PREFIX = 0x1b };
					if (c == ESC_PREFIX) {
						_enter_state_esc_seq();
						break;
					}

					/* handle special characters */

					/* handle normal characters */
					_screen.output(c);

					break;

				case STATE_ESC_SEQ:

					/*
					 * We received the prefix character of an escape sequence,
					 * collect the escape-sequence elements until we detect the
					 * completion of the sequence.
					 */

					/* check for start of a number argument */
					if (is_digit(c) && !_number)
					{
						_enter_state_esc_number();
						_append_to_number(c);
						break;
					}

					/* non-number character of escape sequence */
					_escape_stack.push(Escape_stack::Code_entry(c));
					break;

				case STATE_ESC_NUMBER:

					/*
					 * We got the first character belonging to a number
					 * argument of an escape sequence. Keep reading digits.
					 */
					if (is_digit(c)) {
						_append_to_number(c);
						break;
					}

					/*
					 * End of number is reached.
					 */

					/* push the complete number to the escape stack */
					_escape_stack.push(Escape_stack::Number_entry(_number));
					_number = 0;

					/* push non-number character as commend entry */
					_escape_stack.push(Escape_stack::Code_entry(c));

					break;
				}

				/*
				 * Check for the completeness of an escape sequence.
				 */
				if (((_escape_stack.num_elem() == 1) && _handle_esc_seq_1())
				 || ((_escape_stack.num_elem() == 2) && _handle_esc_seq_2())
				 || ((_escape_stack.num_elem() == 3) && _handle_esc_seq_3())
				 || ((_escape_stack.num_elem() == 4) && _handle_esc_seq_4())
				 || ((_escape_stack.num_elem() == 5) && _handle_esc_seq_5()))
					_enter_state_idle();
			};
	};
}

#endif /* _TERMINAL__DECODER_H_ */