697 - Tag

[justBadProgrammer]

// your answers
type IsEqual<X,Y> =(<A>()=>A extends X ? 1 : 2) extends 
    (<B>()=>B extends Y ? 1 : 2)
    ? true
    : false ;

declare const a:unique symbol;
type Unique =typeof a;

declare const d: unique symbol;
type CommonValue=typeof d;

declare const b:unique symbol;
type NonRegular = typeof b;

type GetTagValue<
    Source> =
    Unique extends keyof Source
    ? Exclude<keyof Exclude<Source[Unique],undefined>,symbol|number>
    : never ;

type TagValueFromTagTuple<
    T extends readonly string[],
    TagValue extends string = never,
    PossiblyEmptyValue extends string = [TagValue] extends [never] ? '' : TagValue> =
    T extends readonly [infer R extends string,...infer U extends readonly string[]]
    ? U extends []
    ? TagValueFromTagTuple<U,`${PossiblyEmptyValue}${R}`>
    : TagValueFromTagTuple<U,`${PossiblyEmptyValue}${R}|`>
    : TagValue  ;

type TagTupleFromTagValue<
    TagValue extends string> =
    [TagValue] extends [never]
    ? []
    : TagValue extends `${infer R extends string}|${infer U extends string}`
    ? [R,...TagTupleFromTagValue<U>]
    : [TagValue] ;

type GetTags<
    Source> =
     [Source] extends [never] 
    ? []
    : 1 extends 2&Source
    ? []
    : TagTupleFromTagValue<GetTagValue<Source>> ;

type SetMarker<
    Source,
    NewTagValue extends string,
    OldTagValue extends string = 
        GetTagValue<Source>,
    TagValue extends string  = 
        [OldTagValue] extends [never] 
        ? `${NewTagValue}`
        : `${OldTagValue}|${NewTagValue}` ,
    Marker extends object = {[J in Unique]? : {[J in TagValue|CommonValue]? : true}}   > =
    NonRegular extends keyof Source  
    ? {[J in NonRegular] : Source[J]}&Marker
    : UnTag<Source>&Marker  ;      

type EffectiveSource<
    Source,
    > =
    [IsEqual<Source,{}>&IsEqual<Source,never>&IsEqual<Source,any>] extends [never] 
    ? {[J in NonRegular] : Source}
    : Source  ;
    
type Tag<
    Source, 
    NewTagValue extends string,
    > =
    IsEqual<Source,undefined>&IsEqual<Source,null> extends [never]
    ? Source
    : SetMarker<EffectiveSource<Source>,NewTagValue>  ;

type UnTag<
    Source,
    Marker ={[J in Unique&keyof Source]? :Source[J]}> =
    NonRegular extends keyof Source
    ? Source[NonRegular]
    : Source extends infer R&Marker
    ? R
    : Source  ;

type UnionMemberHasTag<
    Source, 
    TagValue extends string> =     
    Source extends Source
    ? [GetTagValue<Source>] extends [never]
    ? false
    : GetTagValue<Source> extends `${infer R}${TagValue}${infer U}`
    ? true
    : false
    : never;

type UnionMemberHasExactTag<
    Source,
    TagValue extends string> =
    Source extends Source
    ? IsEqual<GetTagValue<Source>,TagValue>
    : never ;

type HasTag<
    Source,
    TagValue extends string> = 
    UnionMemberHasTag<Source,TagValue> extends true 
    ? true 
    : false ;

type HasTags<
    Source, 
    TagTuple extends readonly string[]> =
    HasTag<Source,TagValueFromTagTuple<TagTuple>> ;

type HasExactTags<
    Source, 
    TagTuple extends readonly string[]> =
    TagTuple extends []
    ? true 
    : UnionMemberHasExactTag<Source,TagValueFromTagTuple<TagTuple>> extends true 
    ? true
    : false ;