// inspired by (https://github.com/unicode-org/message-format-wg/blob/main/spec/syntax.md)

export type Language = string

export type NodeName =
	| "Identifier"
	| "Resource"
	| "Message"
	| "Pattern"
	| "Text"
	| "LanguageTag"
	| "Placeholder"
	| "VariableReference"

/**
 * A utility type to extend any node with a new property.
 * Does this recursively for all child nodes.
 *
 * @example attach a verified property to all nodes
 * ```
 * type VerifiedResource = Resource<{ verified: boolean }>
 * ```
 * @example attach a verified property only to the Message node
 * ```
 * type ResourceWithVerifiedMessages = Resource<{ Message: { verified: boolean } }>
 * ```
 */
type ExtensionInformation = {
	[node in NodeName | "Node"]?: Record<string, unknown>
}

/**
 * A single node of the AST.
 *
 * Every other definitions are based on Node.
 */
type Node<
	Name extends NodeName,
	Extension extends ExtensionInformation = ExtensionInformation,
> = Extension[Name] &
	Extension["Node"] & {
		type: Name
		/**
		 *
		 * @deprecated Will be removed in the future, see https://github.com/inlang/inlang/issues/945.
		 */
		metadata?: any
	}

/**
 * An identifier.
 *
 * Some Nodes have Identifiers such as a Message.
 */
export type Identifier<Extension extends ExtensionInformation = ExtensionInformation> = Node<
	"Identifier",
	Extension
> & {
	name: string
}

/**
 * A resource is a collection of messages.
 */
export type Resource<Extension extends ExtensionInformation = ExtensionInformation> = Node<
	"Resource",
	Extension
> & {
	languageTag: LanguageTag<Extension>
	body: Array<Message<Extension>>
}

/**
 * A message is what's rendered to a user.
 */
export type Message<Extension extends ExtensionInformation = ExtensionInformation> = Node<
	"Message",
	Extension
> & {
	id: Identifier<Extension>
	// comment?: MessageComment
	pattern: Pattern<Extension>
}

/**
 * A pattern denotes how a Message is composed.
 */
export type Pattern<Extension extends ExtensionInformation = ExtensionInformation> = Node<
	"Pattern",
	Extension
> & {
	elements: Array<Text<Extension> | Placeholder<Extension>>
}

/**
 * Text can be translated.
 */
export type Text<Extension extends ExtensionInformation = ExtensionInformation> = Node<
	"Text",
	Extension
> & {
	value: string
}

export type Placeholder<Extension extends ExtensionInformation = ExtensionInformation> = Node<
	"Placeholder",
	Extension
> & {
	// only variable reference for now, but will be extended in the future
	body: VariableReference<Extension>
}

export type VariableReference<Extension extends ExtensionInformation = ExtensionInformation> = Node<
	"VariableReference",
	Extension
> & {
	name: string
}

/**
 * A language tag that identifies a human language.
 *
 * The node is planned to obey to [IETF BCP 47 language tags](https://en.wikipedia.org/wiki/IETF_language_tag).
 * For now, only a name that acts as an ID can be set. See
 * https://github.com/inlang/inlang/issues/296
 */
export type LanguageTag<Extension extends ExtensionInformation = ExtensionInformation> = Node<
	"LanguageTag",
	Extension
> & {
	/**
	 * The ID of the language.
	 */
	name: string

	/**
	 *
	 * The language can be named freely. It's advisable to follow the IETF BCP 47 language tag scheme.
	 *
	 * @see https://www.ietf.org/rfc/bcp/bcp47.txt
	 * @see https://www.iana.org/assignments/language-subtag-registry/language-subtag-registry
	 */
	// language: Language
}