netdata/netdata

// SPDX-License-Identifier: GPL-3.0-or-later

#ifndef NETDATA_EVAL_H
#define NETDATA_EVAL_H 1

#include "../libnetdata.h"

#define EVAL_MAX_VARIABLE_NAME_LENGTH 300

struct eval_expression;
typedef struct eval_expression EVAL_EXPRESSION;
typedef bool (*eval_expression_variable_lookup_t)(STRING *variable, void *data, NETDATA_DOUBLE *result);

// parsing and evaluation
#define EVAL_ERROR_OK                             0

// parsing errors
#define EVAL_ERROR_MISSING_CLOSE_SUBEXPRESSION    1
#define EVAL_ERROR_UNKNOWN_OPERAND                2
#define EVAL_ERROR_MISSING_OPERAND                3
#define EVAL_ERROR_MISSING_OPERATOR               4
#define EVAL_ERROR_REMAINING_GARBAGE              5
#define EVAL_ERROR_IF_THEN_ELSE_MISSING_ELSE      6

// evaluation errors
#define EVAL_ERROR_INVALID_VALUE                101
#define EVAL_ERROR_INVALID_NUMBER_OF_OPERANDS   102
#define EVAL_ERROR_VALUE_IS_NAN                 103
#define EVAL_ERROR_VALUE_IS_INFINITE            104
#define EVAL_ERROR_UNKNOWN_VARIABLE             105

// parse the given string as an expression and return:
//   a pointer to an expression if it parsed OK
//   NULL in which case the pointer to error has the error code
EVAL_EXPRESSION *expression_parse(const char *string, const char **failed_at, int *error);

// free all resources allocated for an expression
void expression_free(EVAL_EXPRESSION *expression);

// convert an error code to a message
const char *expression_strerror(int error);

// evaluate an expression and return
// 1 = OK, the result is in: expression->result
// 2 = FAILED, the error message is in: buffer_tostring(expression->error_msg)
int expression_evaluate(EVAL_EXPRESSION *expression);

const char *expression_source(EVAL_EXPRESSION *expression);
const char *expression_parsed_as(EVAL_EXPRESSION *expression);
const char *expression_error_msg(EVAL_EXPRESSION *expression);
NETDATA_DOUBLE expression_result(EVAL_EXPRESSION *expression);
void expression_set_variable_lookup_callback(EVAL_EXPRESSION *expression, eval_expression_variable_lookup_t cb, void *data);

void expression_hardcode_variable(EVAL_EXPRESSION *expression, STRING *variable, NETDATA_DOUBLE value);

#endif //NETDATA_EVAL_H