mtcute/packages/tl-utils/src/patch.ts

import { TlReaderMap, TlWriterMap } from '@mtcute/tl-runtime'

import { generateReaderCodeForTlEntries } from './codegen/reader.js'
import { generateWriterCodeForTlEntries } from './codegen/writer.js'
import { parseTlToEntries } from './parse.js'

function evalForResult<T>(js: string): T {
    // eslint-disable-next-line @typescript-eslint/no-implied-eval
    return new Function(js)() as T
}

/**
 * Patch runtime TL schema (readers and writers map) with the given schema.
 *
 * Entries in the schema will override the ones in the existing one.
 * Original readers and writers will be preserved, new ones will be returned.
 *
 * @param schema  Schema containing new entries
 * @param readers  Original readers map
 * @param writers  Original writers map
 * @returns  New readers and writers map
 */
export function patchRuntimeTlSchema(
    schema: string,
    readers: TlReaderMap,
    writers: TlWriterMap,
): {
    readerMap: TlReaderMap
    writerMap: TlWriterMap
} {
    const entries = parseTlToEntries(schema, { parseMethodTypes: true })

    const readersCode = generateReaderCodeForTlEntries(entries, {
        variableName: '_',
        includeMethods: false,
        includeMethodResults: true,
    })
    const writersCode = generateWriterCodeForTlEntries(entries, {
        variableName: '_',
        includePrelude: true,
    })

    const newReaders = evalForResult<TlReaderMap>(readersCode.replace('var _=', 'return'))
    const newWriters = evalForResult<TlWriterMap>(writersCode.replace('var _=', 'return'))

    return {
        readerMap: {
            ...readers,
            ...newReaders,
            _results: {
                ...readers._results,
                ...newReaders._results,
            },
        },
        // ts is not smart enough
        // eslint-disable-next-line @typescript-eslint/ban-ts-comment
        // @ts-expect-error
        writerMap: {
            ...writers,
            ...newWriters,
            _bare: {
                ...writers._bare,
                ...newWriters._bare,
            },
        },
    }
}