#!/usr/bin/awk -f
#
# ZyklonB eval plugin, LISP-like expression evaluator
#
# Copyright 2013, 2014 Přemysl Janouch.  All rights reserved.
# See the file LICENSE for licensing information.
#

BEGIN \
{
	RS = "\r"
	ORS = "\r\n"
	IGNORECASE = 1
	srand()

	prefix = get_config("prefix")

	print "ZYKLONB register"
	fflush("")

	# All functions have to be in this particular array
	min_args["int"]    = 1
	min_args["+"]      = 1
	min_args["-"]      = 1
	min_args["*"]      = 1
	min_args["/"]      = 1
	min_args["%"]      = 1
	min_args["^"]      = 1
	min_args["**"]     = 1
	min_args["exp"]    = 1
	min_args["sin"]    = 1
	min_args["cos"]    = 1
	min_args["atan2"]  = 2
	min_args["log"]    = 1
	min_args["rand"]   = 0
	min_args["sqrt"]   = 1

	min_args["pi"]     = 0
	min_args["e"]      = 0

	min_args["min"]    = 1
	min_args["max"]    = 1

	# Whereas here their presence is only optional
	max_args["int"]    = 1
	max_args["sin"]    = 1
	max_args["cos"]    = 1
	max_args["atan2"]  = 2
	max_args["log"]    = 1
	max_args["rand"]   = 0
	max_args["sqrt"]   = 1

	max_args["pi"]     = 0
	max_args["e"]      = 0
}

{
	parse($0)
}

msg_command == "PRIVMSG" \
{
	# Context = either channel or user nickname
	match(msg_prefix, /^[^!]+/)
	ctx = substr(msg_prefix, RSTART, RLENGTH)
	if (msg_param[0] ~ /^[#&!+]/)
	{
		ctxquote = ctx ": "
		ctx = msg_param[0]
	}
	else
		ctxquote = ""


	if (substr(msg_param[1], 1, length(prefix)) == prefix)
	{
		keyword = "eval"
		text = substr(msg_param[1], 1 + length(prefix))
	 	if (match(text, "^" keyword "([^A-Za-z0-9].*|$)"))
			process_request(substr(text, 1 + length(keyword)))
	}
}

{
	fflush("")
}

function pmrespond (text)
{
	print "PRIVMSG " ctx " :" ctxquote text
}

function process_request (input,    res, x)
{
	delete funs
	delete accumulator
	delete n_args

	res = ""
	fun_top = 0
	funs[0] = ""
	accumulator[0] = 0
	n_args[0] = 0

	if (match(input, "^[ \t]*"))
		input = substr(input, RLENGTH + 1)
	if (input == "")
		res = "expression missing"

	while (res == "" && input != "") {
		if (match(input, "^-?[0-9]+\\.?[0-9]*")) {
			x = substr(input, RSTART, RLENGTH)
			input = substr(input, RLENGTH + 1)

			match(input, "^ *")
			input = substr(input, RLENGTH + 1)

			res = process_argument(x)
		} else if (match(input, "^[(]([^ ()]+)")) {
			x = substr(input, RSTART + 1, RLENGTH - 1)
			input = substr(input, RLENGTH + 1)

			match(input, "^ *")
			input = substr(input, RLENGTH + 1)

			if (!(x in min_args)) {
				res = "undefined function '" x "'"
			} else {
				fun_top++
				funs[fun_top] = x
				accumulator[fun_top] = 636363
				n_args[fun_top] = 0
			}
		} else if (match(input, "^[)] *")) {
			input = substr(input, RLENGTH + 1)
			res = process_end()
		} else
			res = "invalid input at '" substr(input, 1, 10) "...'"
	}

	if (res == "") {
		if (fun_top != 0)
			res = "unclosed '" funs[fun_top] "'"
		else if (n_args[0] != 1)
			res = "internal error, expected one result" \
				", got " n_args[0] " instead"
	}

	if (res == "")
		pmrespond(accumulator[0])
	else
		pmrespond(res)
}

function process_argument (arg)
{
	if (fun_top == 0) {
		if (n_args[0]++ != 0)
			return "too many results, I only expect one"

		accumulator[0] = arg
		return ""
	}

	fun = funs[fun_top]
	if (fun in max_args && max_args[fun] <= n_args[fun_top])
		return "too many operands for " fun

	if (fun == "int") {
		accumulator[fun_top] = int(arg)
	} else if (fun == "+") {
		if (n_args[fun_top] == 0)
			accumulator[fun_top] = arg
		else
			accumulator[fun_top] += arg
	} else if (fun == "-") {
		if (n_args[fun_top] == 0)
			accumulator[fun_top] = arg
		else
			accumulator[fun_top] -= arg
	} else if (fun == "*") {
		if (n_args[fun_top] == 0)
			accumulator[fun_top] = arg
		else
			accumulator[fun_top] *= arg
	} else if (fun == "/") {
		if (n_args[fun_top] == 0)
			accumulator[fun_top] = arg
		else if (arg == 0)
			return "division by zero"
		else
			accumulator[fun_top] /= arg
	} else if (fun == "%") {
		if (n_args[fun_top] == 0)
			accumulator[fun_top] = arg
		else if (arg == 0)
			return "division by zero"
		else
			accumulator[fun_top] %= arg
	} else if (fun == "^" || fun == "**" || fun == "exp") {
		if (n_args[fun_top] == 0)
			accumulator[fun_top] = arg
		else
			accumulator[fun_top] ^= arg
	} else if (fun == "sin") {
		accumulator[fun_top] = sin(arg)
	} else if (fun == "cos") {
		accumulator[fun_top] = cos(arg)
	} else if (fun == "atan2") {
		if (n_args[fun_top] == 0)
			accumulator[fun_top] = arg
		else
			accumulator[fun_top] = atan2(accumulator[fun_top], arg)
	} else if (fun == "log") {
		accumulator[fun_top] = log(arg)
	} else if (fun == "rand") {
		# Just for completeness, execution never gets here
	} else if (fun == "sqrt") {
		accumulator[fun_top] = sqrt(arg)
	} else if (fun == "min") {
		if (n_args[fun_top] == 0)
			accumulator[fun_top] = arg
		else if (accumulator[fun_top] > arg)
			accumulator[fun_top] = arg
	} else if (fun == "max") {
		if (n_args[fun_top] == 0)
			accumulator[fun_top] = arg
		else if (accumulator[fun_top] < arg)
			accumulator[fun_top] = arg
	} else
		return "internal error, unhandled operands for " fun

	n_args[fun_top]++
	return ""
}

function process_end ()
{
	if (fun_top <= 0)
		return "extraneous ')'"

	fun = funs[fun_top]
	if (!(fun in min_args))
		return "internal error, unhandled ')' for '" fun "'"
	if (min_args[fun] > n_args[fun_top])
		return "not enough operands for '" fun "'"

	# There's no 'init' function to do it in
	if (fun == "rand")
		accumulator[fun_top] = rand()
	else if (fun == "pi")
		accumulator[fun_top] = 3.141592653589793
	else if (fun == "e")
		accumulator[fun_top] = 2.718281828459045

	return process_argument(accumulator[fun_top--])
}

function get_config (key)
{
	print "ZYKLONB get_config :" key
	fflush("")

	getline
	parse($0)
	return msg_param[0]
}

function parse (line,     s, n, id, token)
{
	s = 1
	id = 0

	# NAWK only uses the first character of RS
	if (line ~ /^\n/)
		line = substr(line, 2)

	msg_prefix = ""
	msg_command = ""
	delete msg_param

	n = match(substr(line, s), / |$/)
	while (n)
	{
		token = substr(line, s, n - 1)
		if (token ~ /^:/)
		{
			if (s == 1)
				msg_prefix = substr(token, 2)
			else
			{
				msg_param[id] = substr(line, s + 1)
				break
			}
		}
		else if (!msg_command)
			msg_command = toupper(token)
		else
			msg_param[id++] = token

		s = s + n
		n = index(substr(line, s), " ")

		if (!n)
		{
		       n = length(substr(line, s)) + 1
		       if (n == 1)
			       break;
		}
	}
}