Demo

Specification

Is

Case 1.1.1:

input = find a person whose @name is Maksym

output = {
    "field": "name",
    "operator": "==",
    "value": "Maksym"
}

Case 1.1.2:

input = find person whose @name is "Maksym"

output = {
    "field": "name",
    "operator": "==",
    "value": "Maksym"
}

Case 1.1.3:

input = find a person whose @name is "Maksym Oliinyk"

output = {
    "field": "name",
    "operator": "==",
    "value": "Maksym Oliinyk"
}

Case 1.1.4:

input = @name is "Maksym Oliinyk"

output = {
    "field": "name",
    "operator": "==",
    "value": "Maksym Oliinyk"
}  

Case 1.1.5:

input = find a person whose name Maksym

output = null

Case 1.1.6:

input = find a person whose @ name is Maksym

output = null   

Case 1.1.7:

input = find@name is Maksym

output = null

Case 1.1.8:

input = @@@name is Max

output = null

Case 1.1.9:

input = @nonexistingfield is Max

output = [
]        

Case 1.1.10:

input = @name could be or is Maksym Oliinyk

output = null 

Is not

Case 1.2.1:

input = @name is not Maksym

output = {
    "field": "name",
    "operator": "!=",
    "value": "Maksym"
}

Case 1.2.2:

input = @name is something not something Maksym

output = {
    "field": "name",
    "operator": "==",
    "value": "Maksym"
} 

Case 1.2.3:

input = find a person whose @name is not Maksym Oliinyk

output = {
    "field": "name",
    "operator": "!=",
    "value": "Maksym"
}    

Case 1.2.4:

input = @name is not "Maksym Oliinyk"

output = {
    "field": "name",
    "operator": "!=",
    "value": "Maksym Oliinyk"
}  

Either or / Neither nor

Case 1.3.1:

input = @forename is either Maksym or Viktor

output = {
    "field": "forename",
    "operator": "in",
    "value": [
        "\"Maksym\"",
        "\"Viktor\""
    ]
} 

Case 1.3.2:

input = @forename is neither Maksym nor Viktor

output = {
     "field": "forename",
     "operator": "not in",
     "value": [
         "\"Maksym\"",
         "\"Viktor\""
     ]
}    

And

Case 1.4.1:

input = @forename is Maksym and @surname Oliinyk and @age is 26

output = {
    "and": [
        {
            "and": [
                {
                    "field": "forename",
                    "operator": "==",
                    "value": "Maksym"
                },
                null
            ]
        },
        {
            "field": "age",
            "operator": "==",
            "value": "26"
        }
    ]
}

Case 1.4.2:

input = @age is 26 and @name is "Maksym Oliinyk"

output = {
    "and": [
        {
            "field": "age",
            "operator": "==",
            "value": "26"
        },
        {
            "field": "name",
            "operator": "==",
            "value": "Maksym Oliinyk"
        }
    ]
}  

Case 1.4.3:

input = @forename is Maksym and @surname is either Ivanov or Petrov

output = {
    "and": [
        {
            "field": "forename",
            "operator": "==",
            "value": "Maksym"
        },
        {
            "field": "surname",
            "operator": "in",
            "value": [
                "\"Ivanov\"",
                "\"Petrov\""
            ]
        }
    ]
}   

Or

Case 1.5.1:

input = @forename is Maksym or @surname Oliinyk

output = {
    "or": [
        {
            "field": "forename",
            "operator": "==",
            "value": "Maksym"
        },
        null
    ]
}   

Case 1.5.2:

input = @forename is Maksym and @surname is either Ivanov or Petrov or @forename is Viktor and @surname is neither Sokolov nor Smirnov

output = {
    "or": [
        {
            "and": [
                {
                    "field": "forename",
                    "operator": "==",
                    "value": "Maksym"
                },
                {
                    "field": "surname",
                    "operator": "in",
                    "value": [
                        "\"Ivanov\"",
                        "\"Petrov\""
                    ]
                }
            ]
        },
        {
            "and": [
                {
                    "field": "forename",
                    "operator": "==",
                    "value": "Viktor"
                },
                {
                    "field": "surname",
                    "operator": "not in",
                    "value": [
                        "\"Sokolov\"",
                        "\"Smirnov\""
                    ]
                }
            ]
        }
    ]
}  

In

Case 1.6.1:

input = @forename is in (Maksym, Viktor)

output = {
    "field": "forename",
    "operator": "in",
    "value": [
        "\"Maksym\"",
        "\"Viktor\""
    ]
}    

Case 1.6.2:

input = @forename is in ()

output = {
    "field": "forename",
    "operator": "in",
    "value": []
} 

Case 1.6.3:

input = @forename is in

output = null   

Case 1.7.1:

input = @forename is in (Maksym, Viktor) or @forename is not in (Alex, Julia)

output = 
    "or": [
        {
            "field": "forename",
            "operator": "in",
            "value": [
                "\"Maksym\"",
                "\"Viktor\""
            ]
        },
        {
            "field": "forename",
            "operator": "not in",
            "value": [
                "\"Alex\"",
                "\"Julia\""
            ]
        }
    ]
}

Case 1.7.2:

input = ((@name is either Max or Joe) or (@surname is neither Oliinyk nor Doe)) and ((@age is not 27) or (@forename is Oliinyk)) or @surname is not Smirnov

output = {
    "or": [
        {
            "and": [
                {
                    "or": [
                        {
                            "field": "name",
                            "operator": "in",
                            "value": [
                                "Max",
                                "Joe"
                            ]
                        },
                        {
                            "field": "surname",
                            "operator": "not in",
                            "value": [
                                "Oliinyk",
                                "Doe"
                            ]
                        }
                    ]
                },
                {
                    "or": [
                        {
                            "field": "age",
                            "operator": "!=",
                            "value": "27"
                        },
                        {
                            "field": "forename",
                            "operator": "==",
                            "value": "Oliinyk"
                        }
                    ]
                }
            ]
        },
        {
            "field": "surname",
            "operator": "!=",
            "value": "Smirnov"
        }
    ]
}