Strongly typed query condition as in Yii2 (PHP). [typscript 4.1 literal templates]

typed_condition_tree.ts

export type Path<T> =
  T extends Array<infer S> ? Path<S> & string :
  (T extends object ? {
    [K in keyof T]: T[K] extends Array<any> ? Path.Item<T, K> : K & string | Path.Item<T, K>
  }[keyof T] : never)

export namespace Path {
  export type Item<T, K extends keyof T> = `${K & string}.${Path<T[K]> & string}`
  export type Type<T, Q extends Path<T>> =
    T extends Array<infer S> ? (Q extends Path<S> ? Type<S, Q> : never) :
    Q extends keyof T ? T[Q] :
    Q extends `${infer P}.${infer REST}` ?
    P extends keyof T ? (REST extends Path<T[P]> ? Type<T[P], REST> : never)
    : never
    : never;
}

export type Expression<T> = Expression.Comparison<T> | Expression.Logical<T>
export namespace Expression {
  export type Comparison<T> = {
    [K in Path<T>]: [("<=" | ">=" | "!=") | ("=" | ">" | "<"), K, Path.Type<T, K>] | ["in" | "!in", K, Path.Type<T, K>[]]
  }[Path<T>]
  export type Logical<T> = Comparison<T> | [("&&" | "||"), ...Expression<T>[]]
}

type Entity = { id: number, items: [{ name: string }] };
const validPath: Path<Entity> = "items.name"
const typeOfPath: Path.Type<Entity, "id"> = 123
const expression: Expression<Entity> = ["||", ["<=", "items.name", "123"], ["&&", ["<", "items.name", ""], ["!in", "id", [1, 2, 2]]]]

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