getTypeSchema.ts

import {DataType} from "@code0-tech/sagittarius-graphql-types"
import ts from "typescript"
import {getSchema, Schema} from "../util/schema.util"
import {createCompilerHost, getSharedTypeDeclarations} from "../utils"

/**
 * Generates a schema for a given TypeScript type expression string.
 *
 * This function creates a virtual TypeScript environment, wraps the provided type expression
 * into a type alias 'T', and extracts the schema for it.
 *
 * @param typeString - The TypeScript type expression (e.g., "string | number" or "{ a: string }").
 * @param dataTypes - An optional array of additional data type definitions to be included in the environment.
 * @returns The generated Schema for the identified type, or undefined if no valid type was found or an error occurred.
 */
export const getTypeSchema = (
    typeString: string,
    dataTypes: DataType[] = [],
): Schema | undefined => {
    const fileName = "index.ts"
    const typeDefs = getSharedTypeDeclarations(dataTypes)
    const sourceCode = `${typeDefs}\ntype MyType = ${typeString}`

    const host = createCompilerHost(fileName, sourceCode)
    const program = host.languageService.getProgram()
    const sourceFile = program?.getSourceFile(fileName)
    const checker = program?.getTypeChecker()

    if (!sourceFile || !checker) return undefined

    const targetStatement = sourceFile.statements
        .filter((stmt): stmt is ts.TypeAliasDeclaration | ts.InterfaceDeclaration | ts.ClassDeclaration =>
            ts.isTypeAliasDeclaration(stmt) || ts.isInterfaceDeclaration(stmt) || ts.isClassDeclaration(stmt)
        ).pop()
    if (!targetStatement) return undefined

    const targetType = checker.getTypeAtLocation(targetStatement)
    if (!targetType) return undefined

    return getSchema(checker, undefined, targetType, [], [], false)
}