// 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

typedef enum rrdcalc_status {
    RRDCALC_STATUS_REMOVED       = -2,
    RRDCALC_STATUS_UNDEFINED     = -1,
    RRDCALC_STATUS_UNINITIALIZED =  0,
    RRDCALC_STATUS_CLEAR         =  1,
    RRDCALC_STATUS_RAISED        =  2, // DO NOT CHANGE THESE NUMBERS
    RRDCALC_STATUS_WARNING       =  3, // DO NOT CHANGE THESE NUMBERS
    RRDCALC_STATUS_CRITICAL      =  4, // DO NOT CHANGE THESE NUMBERS
} RRDCALC_STATUS;

typedef struct eval_variable {
    STRING *name;
    struct eval_variable *next;
} EVAL_VARIABLE;

typedef struct eval_expression {
    const char *source;
    const char *parsed_as;

    RRDCALC_STATUS *status;
    NETDATA_DOUBLE *myself;
    time_t *after;
    time_t *before;

    NETDATA_DOUBLE result;

    int error;
    BUFFER *error_msg;

    // hidden EVAL_NODE *
    void *nodes;

    // custom data to be used for looking up variables
    struct rrdcalc *rrdcalc;
} EVAL_EXPRESSION;

#define EVAL_VALUE_INVALID    0
#define EVAL_VALUE_NUMBER     1
#define EVAL_VALUE_VARIABLE   2
#define EVAL_VALUE_EXPRESSION 3

// 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);

int health_variable_lookup(STRING *variable, struct rrdcalc *rc, NETDATA_DOUBLE *result);

#endif //NETDATA_EVAL_H
