import {UpperCaseCharacters, WordSeparators} from '../source/utilities'; /** Unlike a simpler split, this one includes the delimiter splitted on in the resulting array literal. This is to enable splitting on, for example, upper-case characters. */ export type SplitIncludingDelimiters = Source extends '' ? [] : Source extends `${infer FirstPart}${Delimiter}${infer SecondPart}` ? ( Source extends `${FirstPart}${infer UsedDelimiter}${SecondPart}` ? UsedDelimiter extends Delimiter ? Source extends `${infer FirstPart}${UsedDelimiter}${infer SecondPart}` ? [...SplitIncludingDelimiters, UsedDelimiter, ...SplitIncludingDelimiters] : never : never : never ) : [Source]; /** Format a specific part of the splitted string literal that `StringArrayToDelimiterCase<>` fuses together, ensuring desired casing. @see StringArrayToDelimiterCase */ type StringPartToDelimiterCase = StringPart extends UsedWordSeparators ? Delimiter : StringPart extends UsedUpperCaseCharacters ? `${Delimiter}${Lowercase}` : StringPart; /** Takes the result of a splitted string literal and recursively concatenates it together into the desired casing. It receives `UsedWordSeparators` and `UsedUpperCaseCharacters` as input to ensure it's fully encapsulated. @see SplitIncludingDelimiters */ type StringArrayToDelimiterCase = Parts extends [`${infer FirstPart}`, ...infer RemainingParts] ? `${StringPartToDelimiterCase}${StringArrayToDelimiterCase}` : ''; /** Convert a string literal to a custom string delimiter casing. This can be useful when, for example, converting a camel-cased object property to an oddly cased one. @see KebabCase @see SnakeCase @example ``` import {DelimiterCase} from 'type-fest'; // Simple const someVariable: DelimiterCase<'fooBar', '#'> = 'foo#bar'; // Advanced type OddlyCasedProps = { [K in keyof T as DelimiterCase]: T[K] }; interface SomeOptions { dryRun: boolean; includeFile: string; foo: number; } const rawCliOptions: OddlyCasedProps = { 'dry#run': true, 'include#file': 'bar.js', foo: 123 }; ``` */ export type DelimiterCase = Value extends string ? StringArrayToDelimiterCase< SplitIncludingDelimiters, WordSeparators, UpperCaseCharacters, Delimiter > : Value;