helper.ts

import {
  z,
  ZodArray,
  ZodBoolean,
  ZodDate,
  ZodDefault,
  ZodEffects,
  ZodEnum,
  ZodLiteral,
  ZodNativeEnum,
  ZodNumber,
  ZodObject,
  ZodOptional,
  ZodString,
  ZodType,
  ZodTypeAny,
} from 'zod'

function isIterable(
  maybeIterable: unknown,
): maybeIterable is Iterable<unknown> {
  return Symbol.iterator in Object(maybeIterable)
}

function parseParams(o: any, schema: any, key: string, value: any) {
  // find actual shape definition for this key
  let shape = schema
  while (shape instanceof ZodObject || shape instanceof ZodEffects) {
    shape =
      shape instanceof ZodObject
        ? shape.shape
        : shape instanceof ZodEffects
        ? shape._def.schema
        : null
    if (shape === null) {
      throw new Error(`Could not find shape for key ${key}`)
    }
  }

  if (key.includes('.')) {
    let [parentProp, ...rest] = key.split('.')
    o[parentProp] = o[parentProp] ?? {}
    parseParams(o[parentProp], shape[parentProp], rest.join('.'), value)
    return
  }
  let isArray = false
  if (key.includes('[]')) {
    isArray = true
    key = key.replace('[]', '')
  }
  const def = shape[key]
  if (def) {
    processDef(def, o, key, value as string)
  }
}

function getParamsInternal<T>(
  params: URLSearchParams | FormData | Record<string, string | undefined>,
  schema: any,
):
  | { success: true; data: T; errors: undefined }
  | { success: false; data: undefined; errors: { [key: string]: string } } {
  // @ts-ignore
  let o: any = {}
  let entries: [string, unknown][] = []
  if (isIterable(params)) {
    entries = Array.from(params)
  } else {
    entries = Object.entries(params)
  }
  for (let [key, value] of entries) {
    // infer an empty param as if it wasn't defined in the first place
    if (value === '') {
      continue
    }
    parseParams(o, schema, key, value)
  }

  const result = schema.safeParse(o)
  if (result.success) {
    return { success: true, data: result.data as T, errors: undefined }
  } else {
    let errors: any = {}
    const addError = (key: string, message: string) => {
      if (!errors.hasOwnProperty(key)) {
        errors[key] = message
      } else {
        if (!Array.isArray(errors[key])) {
          errors[key] = [errors[key]]
        }
        errors[key].push(message)
      }
    }
    for (let issue of result.error.issues) {
      const { message, path, code, expected, received } = issue
      const [key, index] = path
      let value = o[key]
      let prop = key
      if (index !== undefined) {
        value = value[index]
        prop = `${key}[${index}]`
      }
      addError(key, message)
    }
    return { success: false, data: undefined, errors }
  }
}

export function getParams<T extends ZodType<any, any, any>>(
  params: URLSearchParams | FormData | Record<string, string | undefined>,
  schema: T,
) {
  type ParamsType = z.infer<T>
  return getParamsInternal<ParamsType>(params, schema)
}

export function getSearchParams<T extends ZodType<any, any, any>>(
  request: Pick<Request, 'url'>,
  schema: T,
) {
  type ParamsType = z.infer<T>
  let url = new URL(request.url)
  return getParamsInternal<ParamsType>(url.searchParams, schema)
}

export async function getFormData<T extends ZodType<any, any, any>>(
  request: Pick<Request, 'formData'>,
  schema: T,
) {
  type ParamsType = z.infer<T>
  let data = await request.formData()
  return getParamsInternal<ParamsType>(data, schema)
}

export function getParamsOrFail<T extends ZodType<any, any, any>>(
  params: URLSearchParams | FormData | Record<string, string | undefined>,
  schema: T,
) {
  type ParamsType = z.infer<T>
  const result = getParamsInternal<ParamsType>(params, schema)
  if (!result.success) {
    throw new Error(JSON.stringify(result.errors))
  }
  return result.data
}

export function getSearchParamsOrFail<T extends ZodType<any, any, any>>(
  request: Pick<Request, 'url'>,
  schema: T,
) {
  type ParamsType = z.infer<T>
  let url = new URL(request.url)
  const result = getParamsInternal<ParamsType>(url.searchParams, schema)
  if (!result.success) {
    throw new Error(JSON.stringify(result.errors))
  }
  return result.data
}

export async function getFormDataOrFail<T extends ZodType<any, any, any>>(
  request: Pick<Request, 'formData'>,
  schema: T,
) {
  type ParamsType = z.infer<T>
  let data = await request.formData()
  const result = getParamsInternal<ParamsType>(data, schema)
  if (!result.success) {
    throw new Error(JSON.stringify(result.errors))
  }
  return result.data
}

export type InputPropType = {
  name: string
  type: string
  required?: boolean
  min?: number
  max?: number
  minLength?: number
  maxLength?: number
  pattern?: string
}

export function useFormInputProps(schema: any, options: any = {}) {
  const shape = schema.shape
  const defaultOptions = options
  return function props(key: string, options: any = {}) {
    options = { ...defaultOptions, ...options }
    const def = shape[key]
    if (!def) {
      throw new Error(`no such key: ${key}`)
    }
    return getInputProps(key, def)
  }
}

function processDef(def: ZodTypeAny, o: any, key: string, value: string) {
  let parsedValue: any
  if (def instanceof ZodString || def instanceof ZodLiteral) {
    parsedValue = value
  } else if (def instanceof ZodNumber) {
    const num = Number(value)
    parsedValue = isNaN(num) ? value : num
  } else if (def instanceof ZodDate) {
    const date = Date.parse(value)
    parsedValue = isNaN(date) ? value : new Date(date)
  } else if (def instanceof ZodBoolean) {
    parsedValue =
      value === 'true' ? true : value === 'false' ? false : Boolean(value)
  } else if (def instanceof ZodNativeEnum || def instanceof ZodEnum) {
    parsedValue = value
  } else if (def instanceof ZodOptional || def instanceof ZodDefault) {
    // def._def.innerType is the same as ZodOptional's .unwrap(), which unfortunately doesn't exist on ZodDefault
    processDef(def._def.innerType, o, key, value)
    // return here to prevent overwriting the result of the recursive call
    return
  } else if (def instanceof ZodArray) {
    if (o[key] === undefined) {
      o[key] = []
    }
    processDef(def.element, o, key, value)
    // return here since recursive call will add to array
    return
  } else if (def instanceof ZodEffects) {
    processDef(def._def.schema, o, key, value)
    return
  } else {
    throw new Error(`Unexpected type ${def._def.typeName} for key ${key}`)
  }
  if (Array.isArray(o[key])) {
    o[key].push(parsedValue)
  } else {
    o[key] = parsedValue
  }
}

function getInputProps(name: string, def: ZodTypeAny): InputPropType {
  let type = 'text'
  let min, max, minlength, maxlength, pattern
  if (def instanceof ZodString) {
    if (def.isEmail) {
      type = 'email'
    } else if (def.isURL) {
      type = 'url'
    }
    minlength = def.minLength ?? undefined
    maxlength = def.maxLength ?? undefined
    const check: any = def._def.checks.find(c => c.kind === 'regex')
    pattern = check ? check.regex.source : undefined
  } else if (def instanceof ZodNumber) {
    type = 'number'
    min = def.minValue ?? undefined
    max = def.maxValue ?? undefined
  } else if (def instanceof ZodBoolean) {
    type = 'checkbox'
  } else if (def instanceof ZodDate) {
    type = 'date'
  } else if (def instanceof ZodArray) {
    return getInputProps(name, def.element)
  } else if (def instanceof ZodOptional) {
    return getInputProps(name, def.unwrap())
  }

  let inputProps: InputPropType = {
    name,
    type,
  }
  if (!def.isOptional()) inputProps.required = true
  if (min) inputProps.min = min
  if (max) inputProps.max = max
  if (minlength && Number.isFinite(minlength)) inputProps.minLength = minlength
  if (maxlength && Number.isFinite(maxlength)) inputProps.maxLength = maxlength
  if (pattern) inputProps.pattern = pattern
  return inputProps
}