# Copyright (c) 2023 Peter McGoron <code@mcgoron.com>
#
# Permission to use, copy, modify, and/or distribute this software for any
# purpose with or without fee is hereby granted, provided that the above
# copyright notice and this permission notice appear in all copies.
#
# THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
# OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
from ctypes import *
import creole
from enum import Enum
dll = CDLL("./libcreole.so")

class CompileRet(Enum):
	OK = 0
	OPCODE_READ_ERROR = 1
	OPCODE_MALFORMED = 2
	ARG_READ_ERROR = 3
	ARG_MALFORMED = 4
	LAST_READ_ERROR = 5
	LAST_MALFORMED = 6
	DATA_OVERFLOW = 7
	TYPE_ERROR = 8
	PROGRAM_OVERFLOW = 9

class RunRet(Enum):
	CONTINUE = 0
	SYSCALL = 1
	STOP = 2
	STACK_OVERFLOW = 3
	STACK_UNDERFLOW = 4
	DECODE_ERROR = 5
	REGISTER_OVERFLOW = 6
	UNKNOWN_OPCODE = 7
	DIVIDE_BY_ZERO = 8
	HIGH_BIT_MALFORMED = 9
	JUMP_OVERFLOW = 10

	def is_halt(self):
		return not (self == RunRet.CONTINUE or self == RunRet.SYSCALL)

class CWord(Structure):
	_fields_ = [("len", c_int),
	            ("high_bits", c_int),
	            ("word", c_uint)]

class CReader(Structure):
	_fields_ = [("p", POINTER(c_ubyte)),
	            ("left", c_size_t)]
class Reader:
	def __init__(self, s):
		self.buf = (c_ubyte * len(s))()
		self.buf[:] = s[:]
		self.rd = CReader(self.buf, len(s))

class CEnv(Structure):
	_fields_ = [
		("dats", POINTER(POINTER(c_ubyte))),
		("datlen", c_size_t),
		("reg", POINTER(c_uint)),
		("reglen", c_size_t),
		("stk", POINTER(c_uint)),
		("stkptr", c_size_t),
		("stklen", c_size_t),
		("r_current", CReader),
		("r_start", CReader)
	]

class RegisterOverflowError(Exception):
	def __init__(self, reg):
		self.reg = reg
class StackOverflowError(Exception):
	def __init__(self, pos):
		self.pos = pos
class InvalidSyscallError(Exception):
	def __init__(self, sc):
		self.sc = sc
class CompileError(Exception):
	def __init__(self, r):
		self.r = r
class DataOverflowError(Exception):
	pass

class Environment:
	def getreg(self, reg, signed=False):
		""" Get the value at the register.

		:param reg: Register number.
		:param signed: If the register value should be interpreted
		as signed.
		"""
		if reg >= self.cenv.reglen or reg < 0:
			raise RegisterOverflowError(r)
		if signed:
			return creole.from_2c(self.cenv.reg[reg])
		else:
			return self.cenv.reg[reg]
	def getstk(self, stk, signed=False):
		""" Get the value at the stack position.

		:param reg: Register number.
		:param signed: If the stack value should be interpreted
		as signed.
		"""
		if stk >= self.cenv.stklen or stk < 0:
			raise StackOverflowError(r)
		if signed:
			return creole.from_2c(self.cenv.stk[stk])
		else:
			return self.cenv.stk[stk]
	def getdat(self, n):
		if n >= self.cenv.datlen or n < 0:
			raise DataOverflowError(n)
		rdr = CReader()
		rdr.p = self.cenv.dats[n]
		# Python does not allow for direct pointer arithmetic
		rdr_p_v = addressof(rdr.p.contents)
		r_start_p_v = addressof(self.cenv.r_start.p)

		rdr.left = self.cenv.r_start.left - (rdr_p_v - r_start_p_v)

		l = []
		w = CWord()
		while dll.creole_decode(byref(rdr), byref(w)) == 1:
			if w.word == 0 and w.len == 1:
				break
			l.append(w.word)
		return l

	def pop(self):
		if stk == 0:
			return None
		stk = stk - 1
		return self.cenv.stk[stk]

	def reset(self):
		self.cenv.r_current = self.cenv.r_start

	def __init__(self, prog=None, reglen=32, datlen=32, stklen=4096, prglen=4096):
		cenv = CEnv()
		cenv.dats = (POINTER(c_ubyte) * datlen)()
		cenv.datlen = datlen

		cenv.reglen = reglen
		cenv.reg = (c_uint * reglen)()

		cenv.stklen = stklen
		cenv.stk = (c_uint * stklen)()
		cenv.stkptr = 0

		self.cenv = cenv
		if prog is not None:
			if type(prog) is creole.Program:
				prog = prog()
			r = self.load(prog)
			if r is not CompileRet.OK:
				raise CompileError(r)

	def load(self, prog):
		self.reader = Reader(prog)
		self.cenv.r_current = self.reader.rd
		self.cenv.r_start = self.cenv.r_current
		ret = dll.creole_compile(byref(self.cenv), byref(self.cenv.r_current))
		return CompileRet(ret)

	def syscall(self, sc):
		raise InvalidSyscallError(sc)
	def __call__(self, debug=False):
		sc = c_size_t()
		ret = RunRet.CONTINUE
		while not ret.is_halt():
			ret = RunRet(dll.creole_step(byref(self.cenv), byref(sc)))
			if ret == RunRet.SYSCALL:
				self.syscall(sc)
			if debug:
				print(self.cenv.reg[0])
		return ret