core/gay.zharel.fateweaver.schemas/CustomStructSchema

CustomStructSchema

class CustomStructSchema<T : Any>(val type: String, val componentNames: List<String>, val componentSchemas: List<FateSchema<*>>, val encoder: (T) -> List<Any>) : FateSchema<T>

A schema you define by hand. You name the components and supply a function that produces them.

Nothing is reflected. Use it for a class you can't modify, or to write fewer bytes than reflection would. You can drop fields you never plot, round a double, convert units, or emit a computed value that isn't a field.

How it works

encoder turns one object into a list of components. Each component has a name from componentNames and a schema from componentSchemas at the same index. They are written in that order after a leading type string.

Binary format

The schema:

[4 bytes: tag] [4 bytes: component count]
[4 bytes: ".type" length] [".type" bytes] [StringSchema]
[4 bytes: name1 length] [name1 bytes] [schema1]
[4 bytes: name2 length] [name2 bytes] [schema2]
...

An encoded object:

[4 bytes: type length] [type string bytes]
[component1 data] [component2 data] ...

Examples

Basic usage

data class Person(val name: String, val age: Int, val email: String)

val personSchema = CustomStructSchema<Person>(
    type = "Person",
    componentNames = listOf("name", "age", "email"),
    componentSchemas = listOf(StringSchema, IntSchema, StringSchema),
    encoder = { person -> listOf(person.name, person.age, person.email) }
)

Transforming values

val transformedSchema = CustomStructSchema<Person>(
    type = "NormalizedPerson",
    componentNames = listOf("displayName", "ageCategory"),
    componentSchemas = listOf(StringSchema, StringSchema),
    encoder = { person ->
        listOf(
            person.name.uppercase(),
            when {
                person.age < 18 -> "MINOR"
                person.age < 65 -> "ADULT"
                else -> "SENIOR"
            }
        )
    }
)

Logging a subset of fields

val minimalSchema = CustomStructSchema<ComplexObject>(
    type = "Essential",
    componentNames = listOf("id", "status"),
    componentSchemas = listOf(LongSchema, StringSchema),
    encoder = { obj -> listOf(obj.id, obj.currentStatus.name) }
)