mobx-keystone-mindreframer/src/typeChecking/object.ts

A MobX powered state management solution based on data trees with first class support for Typescript, snapshots, patches and much more

import type { O } from "ts-toolbelt"
import { Frozen } from "../frozen/Frozen"
import { assertIsFunction, assertIsObject, isObject, lateVal } from "../utils"
import { getTypeInfo } from "./getTypeInfo"
import { resolveStandardType, resolveTypeChecker } from "./resolveTypeChecker"
import type { AnyStandardType, AnyType, ObjectType, ObjectTypeFunction } from "./schemas"
import { lateTypeChecker, LateTypeChecker, TypeChecker, TypeInfo, TypeInfoGen } from "./TypeChecker"
import { TypeCheckError } from "./TypeCheckError"

function typesObjectHelper<S>(objFn: S, frozen: boolean, typeInfoGen: TypeInfoGen): S {
  assertIsFunction(objFn, "objFn")

  return lateTypeChecker(() => {
    const objectSchema: {
      [k: string]: TypeChecker | LateTypeChecker
    } = (objFn as any)()
    assertIsObject(objectSchema, "objectSchema")

    const schemaEntries = Object.entries(objectSchema)

    const getTypeName = (...recursiveTypeCheckers: TypeChecker[]) => {
      const propsMsg: string[] = []
      for (const [k, unresolvedTc] of schemaEntries) {
        const tc = resolveTypeChecker(unresolvedTc)
        let propTypename = "..."
        if (!recursiveTypeCheckers.includes(tc)) {
          propTypename = tc.getTypeName(...recursiveTypeCheckers, tc)
        }
        propsMsg.push(`${k}: ${propTypename};`)
      }

      return `{ ${propsMsg.join(" ")} }`
    }

    const thisTc: TypeChecker = new TypeChecker(
      (obj, path) => {
        if (!isObject(obj) || (frozen && !(obj instanceof Frozen)))
          return new TypeCheckError(path, getTypeName(thisTc), obj)

        // note: we allow excess properties when checking objects
        for (const [k, unresolvedTc] of schemaEntries) {
          const tc = resolveTypeChecker(unresolvedTc)
          const objVal = obj[k]

          const valueError = !tc.unchecked ? tc.check(objVal, [...path, k]) : null
          if (valueError) {
            return valueError
          }
        }

        return null
      },
      getTypeName,
      typeInfoGen
    )

    return thisTc
  }, typeInfoGen) as any
}

/**
 * A type that represents a plain object.
 * Note that the parameter must be a function that returns an object. This is done so objects can support self / cross types.
 *
 * Example:
 * ```ts
 * // notice the ({ ... }), not just { ... }
 * const pointType = types.object(() => ({
 *   x: types.number,
 *   y: types.number
 * }))
 * ```
 *
 * @typeparam T Type.
 * @param objectFunction Function that generates an object with types.
 * @returns
 */
export function typesObject<T>(objectFunction: T): T {
  // we can't type this function or else we won't be able to make it work recursively
  const typeInfoGen: TypeInfoGen = (t) => new ObjectTypeInfo(t, objectFunction as any)

  return typesObjectHelper(objectFunction, false, typeInfoGen) as any
}

/**
 * `types.object` type info for an object props.
 */
export interface ObjectTypeInfoProps {
  readonly [propName: string]: Readonly<{
    type: AnyStandardType
    typeInfo: TypeInfo
  }>
}

/**
 * `types.object` type info.
 */
export class ObjectTypeInfo extends TypeInfo {
  // memoize to always return the same object
  private _props = lateVal(() => {
    const objSchema = this._objTypeFn()

    const propTypes: O.Writable<ObjectTypeInfoProps> = {}
    Object.keys(objSchema).forEach((propName) => {
      const type = resolveStandardType(objSchema[propName])
      propTypes[propName] = { type, typeInfo: getTypeInfo(type) }
    })
    return propTypes
  })

  get props(): ObjectTypeInfoProps {
    return this._props()
  }

  constructor(thisType: AnyStandardType, private _objTypeFn: ObjectTypeFunction) {
    super(thisType)
  }
}

/**
 * A type that represents frozen data.
 *
 * Example:
 * ```ts
 * const frozenNumberType = types.frozen(types.number)
 * const frozenAnyType = types.frozen(types.unchecked<any>())
 * const frozenNumberArrayType = types.frozen(types.array(types.number))
 * const frozenUncheckedNumberArrayType = types.frozen(types.unchecked<number[]>())
 * ```
 *
 * @typeParam T Type.
 * @param dataType Type of the frozen data.
 * @returns
 */
export function typesFrozen<T extends AnyType>(dataType: T): ObjectType<{ data: T }> {
  return typesObjectHelper(
    () => ({
      data: dataType,
    }),
    true,
    (t) => new FrozenTypeInfo(t, resolveStandardType(dataType))
  ) as any
}

/**
 * `types.frozen` type info.
 */
export class FrozenTypeInfo extends TypeInfo {
  get dataTypeInfo(): TypeInfo {
    return getTypeInfo(this.dataType)
  }

  constructor(thisType: AnyStandardType, readonly dataType: AnyStandardType) {
    super(thisType)
  }
}