import { UpperCaseCharacters, WordSeparators } from "./sourceUtilities";

/**
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.

@category Template Literals
*/
export type SplitIncludingDelimiters<Source extends string, Delimiter extends string> = 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<FirstPart, Delimiter>,
                      UsedDelimiter,
                      ...SplitIncludingDelimiters<SecondPart, Delimiter>,
                  ]
                : 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 string,
    UsedWordSeparators extends string,
    UsedUpperCaseCharacters extends string,
    Delimiter extends string,
> = StringPart extends UsedWordSeparators
    ? Delimiter
    : StringPart extends UsedUpperCaseCharacters
    ? `${Delimiter}${Lowercase<StringPart>}`
    : 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 any[],
    UsedWordSeparators extends string,
    UsedUpperCaseCharacters extends string,
    Delimiter extends string,
> = Parts extends [`${infer FirstPart}`, ...infer RemainingParts]
    ? `${StringPartToDelimiterCase<
          FirstPart,
          UsedWordSeparators,
          UsedUpperCaseCharacters,
          Delimiter
      >}${StringArrayToDelimiterCase<RemainingParts, UsedWordSeparators, UsedUpperCaseCharacters, Delimiter>}`
    : "";

/**
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 OddlyCasedProperties<T> = {
	[K in keyof T as DelimiterCase<K, '#'>]: T[K]
};

interface SomeOptions {
	dryRun: boolean;
	includeFile: string;
	foo: number;
}

const rawCliOptions: OddlyCasedProperties<SomeOptions> = {
	'dry#run': true,
	'include#file': 'bar.js',
	foo: 123
};
```

@category Template Literals
*/
export type DelimiterCase<Value, Delimiter extends string> = Value extends string
    ? StringArrayToDelimiterCase<
          SplitIncludingDelimiters<Value, WordSeparators | UpperCaseCharacters>,
          WordSeparators,
          UpperCaseCharacters,
          Delimiter
      >
    : Value;