feat: support creating documents from an existing Prismic repo

src/createMigration.ts

@@ -3,15 +3,15 @@ import type {
 	FilledContentRelationshipField,
 } from "./types/value/contentRelationship"
 import type { PrismicDocument } from "./types/value/document"
-import type { LinkField } from "./types/value/link"
+import type { EmptyLinkField, LinkField } from "./types/value/link"
 
 type PendingPrismicDocument<TDocument extends PrismicDocument> =
 	InjectMigrationSpecificTypes<
 		Pick<TDocument, "type" | "uid" | "lang" | "tags" | "data">
 	>
 
 type ExistingPrismicDocument<TDocument extends PrismicDocument> =
-	PendingPrismicDocument<TDocument> & Pick<TDocument, "id">
+	InjectMigrationSpecificTypes<TDocument>
 
 type MigrationDocument<TDocument extends PrismicDocument> =
 	| PendingPrismicDocument<TDocument>
@@ -24,21 +24,20 @@ type MigrationContentRelationship =
 	| (() => PrismicDocument | PrismicMigrationDocument | undefined)
 	| (() => Promise<PrismicDocument | PrismicMigrationDocument | undefined>)
 
-type MigrationFilledContentRelationshipField = Pick<
-	FilledContentRelationshipField,
-	"link_type" | "id"
->
-
-type InjectMigrationSpecificTypes<T> = T extends null
-	? undefined
-	: T extends LinkField | ContentRelationshipField
-		? T | MigrationContentRelationship
-		: // eslint-disable-next-line @typescript-eslint/no-explicit-any
-			T extends Record<any, any>
-			? { [P in keyof T]: InjectMigrationSpecificTypes<T[P]> }
-			: T extends Array<infer U>
-				? Array<InjectMigrationSpecificTypes<U>>
-				: T
+type MigrationContentRelationshipField =
+	| Pick<FilledContentRelationshipField, "link_type" | "id">
+	| EmptyLinkField<"Document">
+
+type InjectMigrationSpecificTypes<T> = T extends
+	| LinkField
+	| ContentRelationshipField
+	? T | MigrationContentRelationship
+	: // eslint-disable-next-line @typescript-eslint/no-explicit-any
+		T extends Record<any, any>
+		? { [P in keyof T]: InjectMigrationSpecificTypes<T[P]> }
+		: T extends Array<infer U>
+			? Array<InjectMigrationSpecificTypes<U>>
+			: T
 
 export const createMigration = <
 	TDocument extends PrismicDocument,
@@ -83,6 +82,27 @@ export class Migration<TDocument extends PrismicDocument> {
 		return migrationDocument
 	}
 
+	createDocumentFromPrismic(
+		document: TDocument,
+		title: string,
+	): PrismicMigrationDocument<TDocument> {
+		const migrationDocument = new PrismicMigrationDocument(
+			this.#migratePrismicDocumentData({
+				type: document.type,
+				lang: document.lang,
+				uid: document.uid,
+				tags: document.tags,
+				data: document.data,
+			} as PendingPrismicDocument<TDocument>),
+			title,
+			{ originalPrismicID: document.id },
+		)
+
+		this.documents.push(migrationDocument)
+
+		return migrationDocument
+	}
+
 	getByUID<TType extends TDocument["type"]>(
 		type: TType,
 		uid: string,
@@ -105,6 +125,45 @@ export class Migration<TDocument extends PrismicDocument> {
 				doc.document.type === type,
 		)
 	}
+
+	getByOriginalID(id: string): PrismicMigrationDocument | undefined {
+		return this.documents.find((doc) => doc.originalPrismicID === id)
+	}
+
+	#migratePrismicDocumentData(
+		input: PendingPrismicDocument<TDocument>,
+	): PendingPrismicDocument<TDocument>
+	#migratePrismicDocumentData(input: unknown): unknown {
+		if (isFilledContentRelationshipField(input)) {
+			if (input.isBroken) {
+				return { link_type: "Document", id: "_____broken_____", isBroken: true }
+			}
+
+			return () => this.getByOriginalID(input.id)
+		}
+
+		if (input === null) {
+			return undefined
+		}
+
+		if (Array.isArray(input)) {
+			return input.map((element) => this.#migratePrismicDocumentData(element))
+		}
+
+		if (typeof input === "object") {
+			const res: Record<PropertyKey, unknown> = {}
+
+			for (const key in input) {
+				res[key] = this.#migratePrismicDocumentData(
+					input[key as keyof typeof input],
+				)
+			}
+
+			return res
+		}
+
+		return input
+	}
 }
 
 export class PrismicMigrationDocument<
@@ -114,22 +173,31 @@ export class PrismicMigrationDocument<
 	title?: string
 	masterLanguageDocument?: MigrationContentRelationship
 
+	// Only used when the document originally came from Prismic.
+	originalPrismicID?: string
+
 	constructor(
 		document: MigrationDocument<TDocument>,
 		title?: string,
 		options?: {
 			masterLanguageDocument?: MigrationContentRelationship
+			originalPrismicID?: string
 		},
 	) {
 		this.document = document
 		this.title = title
 		this.masterLanguageDocument = options?.masterLanguageDocument
+		this.originalPrismicID = options?.originalPrismicID
 	}
 }
 
 export async function resolveMigrationDocumentData(
 	input: unknown,
 ): Promise<unknown> {
+	if (input === null) {
+		return undefined
+	}
+
 	if (input instanceof PrismicMigrationDocument || isPrismicDocument(input)) {
 		return resolveMigrationContentRelationship(input)
 	}
@@ -161,20 +229,22 @@ export async function resolveMigrationDocumentData(
 
 export async function resolveMigrationContentRelationship(
 	relation: MigrationContentRelationship,
-): Promise<MigrationFilledContentRelationshipField | undefined> {
+): Promise<MigrationContentRelationshipField> {
 	if (typeof relation === "function") {
 		return resolveMigrationContentRelationship(await relation())
 	}
 
 	if (relation instanceof PrismicMigrationDocument) {
 		return relation.document.id
 			? { link_type: "Document", id: relation.document.id }
-			: undefined
+			: { link_type: "Document" }
 	}
 
 	if (relation) {
 		return { link_type: "Document", id: relation.id }
 	}
+
+	return { link_type: "Document" }
 }
 
 function isPrismicDocument(input: unknown): input is PrismicDocument {
@@ -191,3 +261,14 @@ function isPrismicDocument(input: unknown): input is PrismicDocument {
 		return false
 	}
 }
+
+function isFilledContentRelationshipField(
+	input: unknown,
+): input is FilledContentRelationshipField {
+	return (
+		typeof input === "object" &&
+		input !== null &&
+		"link_type" in input &&
+		input.link_type === "Document"
+	)
+}

src/createWriteClient.ts

@@ -71,7 +71,10 @@ export class WriteClient<
 			...doc.document,
 			data: documentData,
 			title: doc.title,
-			alternate_language_id: alternateLanguageDocument?.id,
+			alternate_language_id:
+				"id" in alternateLanguageDocument
+					? alternateLanguageDocument.id
+					: undefined,
 		}
 
 		const response = await this.#fetch(