QueryBeak

querybeak.ts

type Condition<O> = (o: O) => boolean

type QueryableProperty<Alias extends string, Subject, Property> = {
  eq(other: Property): Condition<{ [K in Alias]: Subject }>
  eq<OtherAlias extends string, OtherSubject>(other: QueryableProperty<OtherAlias, OtherSubject, Property>): Condition<{ [K in Alias]: Subject } & { [K in OtherAlias]: OtherSubject }>
}
type Queryable<Alias extends string, Subject> = { [KS in keyof Subject]: QueryableProperty<Alias, Subject, Subject[KS]> }

type Query<O> = {
  where(condition: Condition<O>): Query<O>
  join<OtherAlias extends string, OtherSubject>(other: Queryable<OtherAlias, OtherSubject>): Query<O & {[K in OtherAlias]: OtherSubject}>
}

type Person = {
  id: string
  address: string
  name: string
  age: number
}

type Address = {
  id: string
  street: string
}

declare const person: Queryable<'person', Person>
declare const address: Queryable<'address', Address>
declare function select<Alias extends string, Subject>(queryable: Queryable<Alias, Subject>): Query<{ [K in Alias]: Subject }>

select(person).where(person.age.eq(4), trivial()).where(address.street.eq("")).where(person.id.eq(""))
select(person)
  .join(address)
  .where(person.age.eq(4))
  .where(person.address.eq(address.id))
  .where(person.id.eq(""))