/*

	EXP equation evaluation routines
	Copyright (C) 2000, 2001  Brian Koropoff

	This program 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 2
	of the License, or (at your option) any later version.

	This program 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 this program; if not, write to the Free Software
	Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, US

*/

#include <stdlib.h>
#include <ctype.h>
#include <string.h>
#include <stdio.h>

#include "QF/qtypes.h"
#include "QF/va.h"

#include "exp.h"
#include "ops.h"

exp_error_t EXP_ERROR;
char *exp_error_msg = 0;

optable_t optable[] = 
{
	{"!", OP_Not, 1},
	{"**", OP_Exp, 2},
	{"/", OP_Div, 2},
	{"-", OP_Negate, 1},
	{"*", OP_Mult, 2},
	{"+", OP_Add, 2},
	{"-", OP_Sub, 2},
	{"==", OP_Eq, 2},
	{"!=", OP_Neq, 2},
	{">=", OP_GreaterThanEqual, 2},
	{">", OP_GreaterThan, 2},
	{"<=", OP_LessThanEqual, 2},
	{"<", OP_LessThan, 2},
	{"||", OP_Or, 2},
	{"or", OP_Or, 2},
	{"&&", OP_And, 2},
	{"and", OP_And, 2},
	{"", 0, 0}
};

functable_t functable[] =
{
	{"sqrt", Func_Sqrt, 1},
	{"abs", Func_Abs, 1},
	{"sin", Func_Sin, 1},
	{"cos", Func_Cos, 1},
	{"tan", Func_Tan, 1},
	{"asin", Func_Asin, 1},
	{"acos", Func_Acos, 1},
	{"atan", Func_Atan, 1},
	{"", 0, 0}
};

// Error handling
static exp_error_t 
EXP_Error (exp_error_t err, const char *msg)
{
		EXP_ERROR = err;
		if (exp_error_msg)
			free (exp_error_msg);
		exp_error_msg = strdup(msg);
		return err;
}

const char *
EXP_GetErrorMsg (void)
{
		return exp_error_msg;
}

static token
*EXP_NewToken (void)
{
	token *new;

	new = malloc(sizeof(token));

	if (!new)
		return 0;
	new->generic.type = TOKEN_GENERIC;
	return new;
}

/*
int
EXP_FindIndexByFunc (opfunc func)
{
	int i;
	for (i = 0; optable[i].func; i++)
		if (func == optable[i].func)
			return i;
	return -1;
}
*/

static optable_t *
EXP_FindOpByStr (const char *str)
{
	int i, len, fi;

	for (i = 0, len = 0, fi = -1; optable[i].func; i++)
		if (!strncmp(str, optable[i].str, strlen(optable[i].str)) && strlen(optable[i].str) > len) {
			len = strlen(optable[i].str);
			fi = i;
		}
	if (fi >= 0)
		return optable+fi;
	else
		return 0;
}

static functable_t *
EXP_FindFuncByStr (const char *str)
{
	int i, len, fi;

	for (i = 0, len = 0, fi = -1; functable[i].func; i++)
		if (!strncmp(str, functable[i].str, strlen(functable[i].str)) && strlen(functable[i].str) > len) {
			len = strlen(functable[i].str);
			fi = i;
		}
	if (fi >= 0)
		return functable+fi;
	else
		return 0;
}

static int
EXP_ContainsCommas (token *chain)
{
	token *cur;
	int paren = 0;
	for (cur = chain; cur; cur = cur->generic.next) {
		if (cur->generic.type == TOKEN_OPAREN)
			paren++;
		if (cur->generic.type == TOKEN_CPAREN)
			paren--;
		if (!paren)
			return 0;
		if (cur->generic.type == TOKEN_COMMA)
			return 1;
	}
	return -1; // We should never get here
}

static int
EXP_DoFunction (token *chain)
{
	token *cur, *temp;
	double *oplist = 0;
	double value;
	unsigned int numops = 0;


	for (cur = chain->generic.next; cur; cur = temp) {
		if (cur->generic.type != TOKEN_CPAREN)
			temp = cur->generic.next;
		else
			temp = 0;
		if (cur->generic.type == TOKEN_NUM) {
			numops++;
			oplist = realloc(oplist, sizeof(double)*numops);
			oplist[numops-1] = cur->num.value;
		}
		EXP_RemoveToken (cur);
	}
	if (numops == chain->func.func->operands) {
		value = chain->func.func->func(oplist, numops); // Heh
		chain->generic.type = TOKEN_NUM;
		chain->num.value = value;
		if (oplist)
			free (oplist);
		return 0;
	} else {
		if (oplist)
			free (oplist);
		return -1;
	}
	return -2; // We shouldn't get here
}

static int
EXP_DoUnary (token *chain)
{
	if (chain->generic.next->generic.type == TOKEN_OP)
		EXP_DoUnary (chain->generic.next);
	if (chain->generic.next->generic.type != TOKEN_NUM)
		return -1; // In theory, this should never happen
	chain->generic.next->num.value = chain->op.op->func(chain->generic.next->num.value, 0);
	EXP_RemoveToken (chain);
	return 0;
}

token *
EXP_ParseString (char *str)
{
	char buf[256];

	token *chain, *new, *cur;
	int i,m;
	optable_t *op;
	functable_t *func;

	cur = chain = EXP_NewToken();
	chain->generic.type = TOKEN_OPAREN;
	chain->generic.prev = 0;
	chain->generic.next = 0;

	for (i = 0; i < strlen(str); i++)
	{
		m = 0;
		while(isspace((byte)str[i]))
			i++;
		if (!str[i])
			break;
		if (isdigit((byte)str[i]) || str[i] == '.')
		{
			while ((isdigit((byte)str[i]) // A number
			  || str[i] == '.' // A decimal point
			  || str[i] == 'e' // An exponent
			  || ((str[i] == '-' || str[i] == '+') && str[i-1] == 'e')) // A + or - after an exponent
			  && i < strlen(str) // We are within the string
			  && m < 256) // And there is space in the buffer
				buf[m++] = str[i++];
			buf[m] = 0;
			new = EXP_NewToken();
			new->generic.type = TOKEN_NUM;
			new->num.value = atof(buf);
			new->generic.prev = cur;
			new->generic.next = 0;
			cur->generic.next = new;
			cur = new;
			i--;
		}
		else if (str[i] == ',')
		{
			new = EXP_NewToken();
			new->generic.type = TOKEN_COMMA;
			new->generic.prev = cur;
			new->generic.next = 0;
			cur->generic.next = new;
			cur = new;
		}
		else if (str[i] == '(')
		{
			new = EXP_NewToken();
			new->generic.type = TOKEN_OPAREN;
			new->generic.prev = cur;
			new->generic.next = 0;
			cur->generic.next = new;
			cur = new;
		}
		else if (str[i] == ')')
		{
			new = EXP_NewToken();
			new->generic.type = TOKEN_CPAREN;
			new->generic.prev = cur;
			new->generic.next = 0;
			cur->generic.next = new;
			cur = new;
		}
		else
		{
			while(!(isdigit((byte)str[i])) && !isspace((byte)str[i])
				&& str[i] != '.' && str[i] != '(' && str[i] != ')'
				&& str[i] != ',' && m < 256) {
					buf[m++] = str[i++];
			}
			buf[m] = 0;
			if (m)
			{
				if ((op = EXP_FindOpByStr (buf))) {
					i -= (m - strlen(op->str) + 1);
					new = EXP_NewToken();
					new->generic.type = TOKEN_OP;
					if (*(op->str) == '-') // HACK HACK HACK
						op = optable + 6; // Always assume subtraction for - initially
					new->op.op = op;
					new->generic.prev = cur;
					new->generic.next = 0;
					cur->generic.next = new;
					cur = new;
				} else if ((func = EXP_FindFuncByStr(buf))) {
					i -= (m - strlen(func->str) + 1);
					new = EXP_NewToken();
					new->generic.type = TOKEN_FUNC;
					new->func.func = func;
					new->generic.prev = cur;
					new->generic.next = 0;
					cur->generic.next = new;
					cur = new;
				} else {
					EXP_DestroyTokens (chain);
					EXP_Error (EXP_E_INVOP, va("Unknown operator or function '%s'.", buf));
					return 0;
				}
			}
		}
	}
	new = EXP_NewToken();
	new->generic.type = TOKEN_CPAREN;
	new->generic.prev = cur;
	new->generic.next = 0;
	cur->generic.next = new;
	return chain;
}

exp_error_t
EXP_SimplifyTokens (token *chain)
{
	exp_error_t res;
	int i;
	token *cur;
	token *temp;

	/* First, get rid of parentheses */

	for (cur = chain->generic.next; cur->generic.type != TOKEN_CPAREN; cur = cur->generic.next)
	{
		if (cur->generic.type == TOKEN_OPAREN)
		{
			res = EXP_SimplifyTokens(cur); /* Call ourself to simplify parentheses content */
			if (res)
				return res;
			if (cur->generic.prev->generic.type == TOKEN_FUNC) { // These are arguments to a function
				cur = cur->generic.prev;
				if (EXP_DoFunction (cur))
					return EXP_Error (EXP_E_SYNTAX, va("Invalid number of arguments to function '%s'.", cur->func.func->str));
			} else {
				if (EXP_ContainsCommas (cur))
					return EXP_Error (EXP_E_SYNTAX, "Comma used outside of a function argument list.");
				temp = cur;
				cur = cur->generic.next;
				EXP_RemoveToken(temp); /* Remove parentheses, leaving value behind */
				EXP_RemoveToken(cur->generic.next);
			}
		}
	}

	/* Next, evaluate all operators in order of operations */

	for (i = 0; optable[i].func; i++)
	{
		for (cur = chain->generic.next; cur->generic.type != TOKEN_CPAREN; cur = cur->generic.next)
		{
			if (cur->generic.type == TOKEN_OP && cur->op.op == optable + i && cur->generic.next) {
				// If a unary operator is in our way, it gets evaluated early
				if (cur->generic.next->generic.type == TOKEN_OP)
					if (EXP_DoUnary (cur->generic.next))
						return EXP_Error (EXP_E_SYNTAX, va("Unary operator '%s' not followed by a unary operator or numerical value.", cur->generic.next->op.op->str));
				if (optable[i].operands == 1 && cur->generic.next->generic.type == TOKEN_NUM) {
					cur->generic.next->num.value = optable[i].func(cur->generic.next->num.value, 0);
					temp = cur;
					cur = cur->generic.next;
					EXP_RemoveToken(temp);
				}
				else if (cur->generic.prev->generic.type == TOKEN_NUM && cur->generic.next->generic.type == TOKEN_NUM)
				{
					cur->generic.prev->num.value = optable[i].func(cur->generic.prev->num.value, cur->generic.next->num.value);
					temp = cur;
					cur = cur->generic.prev;
					EXP_RemoveToken(temp->generic.next);
					EXP_RemoveToken(temp);
				}
			}
		}
	}
	return EXP_E_NORMAL;
}

void
EXP_RemoveToken (token *tok)
{
	tok->generic.prev->generic.next = tok->generic.next;
	tok->generic.next->generic.prev = tok->generic.prev;
	free(tok);
}

void
EXP_DestroyTokens (token *chain)
{
	token *temp;
	for (;chain; chain = temp)
	{
		temp = chain->generic.next;
		free(chain);
	}
}

double
EXP_Evaluate (char *str)
{
	token *chain;
	double res;

	EXP_ERROR = EXP_E_NORMAL;

	if (!(chain = EXP_ParseString (str)))
		return 0;
	if (EXP_Validate (chain))
	{
		EXP_DestroyTokens (chain);
		return 0;
	}
	if (EXP_SimplifyTokens (chain))
	{
		EXP_DestroyTokens (chain);
		return 0;
	}
	res = chain->generic.next->num.value;
	EXP_DestroyTokens (chain);
	return res;
}

void
EXP_InsertTokenAfter (token *spot, token *new)
{
	spot->generic.next->generic.prev = new;
	new->generic.next = spot->generic.next;
	new->generic.prev = spot;
	spot->generic.next = new;
}


exp_error_t
EXP_Validate (token *chain)
{
	token *cur, *new;
	int paren = 0;

	for (cur = chain; cur->generic.next; cur = cur->generic.next)
	{
		if (cur->generic.type == TOKEN_OPAREN)
			paren++;
		if (cur->generic.type == TOKEN_CPAREN)
			paren--;
		/* Implied multiplication */
		if ((cur->generic.type == TOKEN_NUM && (
			  cur->generic.next->generic.type == TOKEN_OPAREN || // 5(1+1)
		      cur->generic.next->generic.type == TOKEN_FUNC || // 5 sin (1+1)
		      (cur->generic.next->generic.type == TOKEN_OP && cur->generic.next->op.op->operands == 1))) || // 5!(1+1)
			(cur->generic.type == TOKEN_CPAREN && (
		      cur->generic.next->generic.type == TOKEN_NUM || // (1+1)5
		      cur->generic.next->generic.type == TOKEN_OPAREN))) // (1+1)(1+1)
		{
			new = EXP_NewToken ();
			new->generic.type = TOKEN_OP;
			new->op.op = EXP_FindOpByStr ("*");
			EXP_InsertTokenAfter (cur, new);
		}
		else if ((cur->generic.type == TOKEN_OP || cur->generic.type == TOKEN_OPAREN) && cur->generic.next->generic.type == TOKEN_OP)
		{
			if (cur->generic.next->op.op->func == OP_Sub) /* Stupid hack for negation */
				cur->generic.next->op.op = optable + 3;
			else if (cur->generic.next->op.op->operands == 2)
				return EXP_Error (EXP_E_SYNTAX, va ("Operator '%s' does not follow a number or numerical value.", cur->generic.next->op.op->str));
		}
		else if (cur->generic.type == TOKEN_FUNC && cur->generic.next->generic.type != TOKEN_OPAREN)
			return EXP_Error (EXP_E_SYNTAX, va("Function '%s' called without an argument list.", cur->func.func->str)); 
		else if (cur->generic.type == TOKEN_COMMA && ((cur->generic.prev->generic.type != TOKEN_CPAREN
		  && cur->generic.prev->generic.type != TOKEN_NUM) || paren <= 1))
			return EXP_Error (EXP_E_SYNTAX, "Comma used outside of a function or after a non-number.");
		else if (cur->generic.type == TOKEN_OP && cur->generic.next->generic.type == TOKEN_CPAREN)
			return EXP_Error (EXP_E_SYNTAX, va("Operator '%s' is missing an operand.", cur->op.op->str));
		else if (cur->generic.type == TOKEN_NUM && cur->generic.next->generic.type == TOKEN_NUM)
			return EXP_Error (EXP_E_SYNTAX, "Double number error (two numbers next two each other without an operator).");
		else if (cur->generic.type == TOKEN_OPAREN && cur->generic.next->generic.type == TOKEN_CPAREN)
			return EXP_Error (EXP_E_PAREN, "Empty parentheses found.");
	}

	paren--;
	if (paren)
		return EXP_Error (EXP_E_PAREN, "Parenthesis mismatch.");
	return 0;
}

void
EXP_PrintTokens (token *chain)
{
	for (; chain; chain = chain->generic.next)
		switch (chain->generic.type)
		{
			case TOKEN_OPAREN:
				printf("(");
				break;
			case TOKEN_CPAREN:
				printf(")");
				break;
			case TOKEN_COMMA:
				printf(",");
				break;
			case TOKEN_NUM:
				printf("%f", chain->num.value);
				break;
			case TOKEN_OP:
				printf("%s", chain->op.op->str);
				break;
			case TOKEN_FUNC:
				printf("%s", chain->func.func->str);
				break;
			case TOKEN_GENERIC:
				break;
		}
	printf("\n");
}