import { StandardSchemaDictionary } from "./standard.js";
import { Format, Partial } from "ts-vista";
type CompleteExtension<Define extends StandardSchemaDictionary> = Readonly<{
  /** Inner extensions to merge. */extends: readonly Extension<StandardSchemaDictionary>[]; /** The env variable definitions. */
  define: Define;
}>;
/** Environment variables extension. */
type Extension<Define extends StandardSchemaDictionary> = Format<Partial<CompleteExtension<Define>, "extends">>;
/** Convert a union of object types into their intersection. */
type UnionToIntersection<U> = (U extends unknown ? (x: U) => void : never) extends ((x: infer I) => void) ? I : never;
/**
* Collapse a tuple of extensions to `Record<never, never>` when empty,
* otherwise the intersection of `Mapper` applied to each element.
*/
type CollapseExt<Ext extends readonly Extension<StandardSchemaDictionary>[], Mapper> = [Ext] extends [readonly never[]] ? Record<never, never> : UnionToIntersection<Mapper>;
/** Merge two dictionaries, with `A` winning on key collision. */
type MergeWinLeft<A, B> = { [K in keyof A | keyof B]: K extends keyof A ? A[K] : K extends keyof B ? B[K] : never };
/**
* The `define` schemas of an extension,
* collapsed to an empty record when broad.
*/
type ExtensionDefineSchemas<Ext extends Extension<StandardSchemaDictionary>> = string extends keyof NonNullable<Ext["define"]> ? Record<never, never> : NonNullable<Ext["define"]>;
/** The intersection of `define` schemas contributed by inner extensions. */
type ExtensionDefines<Ext extends readonly Extension<StandardSchemaDictionary>[]> = CollapseExt<Ext, ExtensionDefineSchemas<Ext[number]>>;
/**
* The flattened `define` after merging inner extensions
* with the outer `define` applied last.
*/
type MergedExtensionDefine<Define extends StandardSchemaDictionary, Ext extends readonly Extension<StandardSchemaDictionary>[] = readonly never[]> = MergeWinLeft<Define, ExtensionDefines<Ext>>;
/**
* Extract the inferred output of an extension's `define`,
* collapsed to an empty record when broad.
*/
type ExtensionDefineOutput<Ext extends Extension<StandardSchemaDictionary>> = NonNullable<Ext["define"]> extends StandardSchemaDictionary ? string extends keyof StandardSchemaDictionary.InferOutput<NonNullable<Ext["define"]>> ? Record<never, never> : StandardSchemaDictionary.InferOutput<NonNullable<Ext["define"]>> : Record<never, never>;
/** The inferred env output contributed by different extensions. */
type ExtensionOutputs<Ext extends readonly Extension<StandardSchemaDictionary>[]> = CollapseExt<Ext, ExtensionDefineOutput<Ext[number]>>;
/** The merged output of user-defined variables and variables from extensions. */
type MergedEnvOutput<Define extends StandardSchemaDictionary, Ext extends readonly Extension<StandardSchemaDictionary>[]> = MergeWinLeft<StandardSchemaDictionary.InferOutput<Define>, ExtensionOutputs<Ext>>;
export type { Extension, ExtensionDefineOutput, ExtensionOutputs, MergedEnvOutput, MergedExtensionDefine, UnionToIntersection };
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