Nim/lib/std/jsfetch.nim

## - Fetch for the JavaScript target: https://developer.mozilla.org/docs/Web/API/Fetch_API
## .. Note:: jsfetch is Experimental. jsfetch module requires `-d:nimExperimentalJsfetch`
when not defined(js):
  {.fatal: "Module jsfetch is designed to be used with the JavaScript backend.".}

when defined(nimExperimentalJsfetch) or defined(nimdoc):
  import std/[asyncjs, jsheaders, jsformdata]
  from std/httpcore import HttpMethod
  from std/jsffi import JsObject

  type
    FetchOptions* = ref object of JsRoot  ## Options for Fetch API.
      keepalive*: bool
      metod* {.importjs: "method".}: cstring
      body*, integrity*, referrer*, mode*, credentials*, cache*, redirect*, referrerPolicy*: cstring

    FetchModes* = enum  ## Mode options.
      fmCors = "cors"
      fmNoCors = "no-cors"
      fmSameOrigin = "same-origin"

    FetchCredentials* = enum  ## Credential options. See https://developer.mozilla.org/en-US/docs/Web/API/Request/credentials
      fcInclude = "include"
      fcSameOrigin = "same-origin"
      fcOmit = "omit"

    FetchCaches* = enum  ## https://developer.mozilla.org/docs/Web/API/Request/cache
      fchDefault = "default"
      fchNoStore = "no-store"
      fchReload = "reload"
      fchNoCache = "no-cache"
      fchForceCache = "force-cache"

    FetchRedirects* = enum  ## Redirects options.
      frFollow = "follow"
      frError = "error"
      frManual = "manual"

    FetchReferrerPolicies* = enum  ## Referrer Policy options.
      frpNoReferrer = "no-referrer"
      frpNoReferrerWhenDowngrade = "no-referrer-when-downgrade"
      frpOrigin = "origin"
      frpOriginWhenCrossOrigin = "origin-when-cross-origin"
      frpUnsafeUrl = "unsafe-url"

    Body* = ref object of JsRoot  ## https://developer.mozilla.org/en-US/docs/Web/API/Body
      bodyUsed*: bool

    Response* = ref object of JsRoot  ## https://developer.mozilla.org/en-US/docs/Web/API/Response
      bodyUsed*, ok*, redirected*: bool
      typ* {.importjs: "type".}: cstring
      url*, statusText*: cstring
      status*: cint
      headers*: Headers
      body*: Body

    Request* = ref object of JsRoot  ## https://developer.mozilla.org/en-US/docs/Web/API/Request
      bodyUsed*, ok*, redirected*: bool
      typ* {.importjs: "type".}: cstring
      url*, statusText*: cstring
      status*: cint
      headers*: Headers
      body*: Body


  func newResponse*(body: cstring | FormData): Response {.importjs: "(new Response(#))".}
    ## Constructor for `Response`. This does *not* call `fetch()`. Same as `new Response()`.

  func newRequest*(url: cstring): Request {.importjs: "(new Request(#))".}
    ## Constructor for `Request`. This does *not* call `fetch()`. Same as `new Request()`.

  func clone*(self: Response | Request): Response {.importjs: "#.$1()".}
    ## https://developer.mozilla.org/en-US/docs/Web/API/Response/clone

  proc text*(self: Response): Future[cstring] {.importjs: "#.$1()".}
    ## https://developer.mozilla.org/en-US/docs/Web/API/Body/text

  proc json*(self: Response): Future[JsObject] {.importjs: "#.$1()".}
    ## https://developer.mozilla.org/en-US/docs/Web/API/Body/json

  proc formData*(self: Body): Future[FormData] {.importjs: "#.$1()".}
    ## https://developer.mozilla.org/en-US/docs/Web/API/Body/formData

  proc unsafeNewFetchOptions*(metod, body, mode, credentials, cache, referrerPolicy: cstring;
      keepalive: bool; redirect = "follow".cstring; referrer = "client".cstring; integrity = "".cstring): FetchOptions {.importjs:
      "{method: #, body: #, mode: #, credentials: #, cache: #, referrerPolicy: #, keepalive: #, redirect: #, referrer: #, integrity: #}".}
    ## .. warning:: Unsafe `newfetchOptions`.

  func newfetchOptions*(metod: HttpMethod; body: cstring;
      mode: FetchModes; credentials: FetchCredentials; cache: FetchCaches; referrerPolicy: FetchReferrerPolicies;
      keepalive: bool; redirect = frFollow; referrer = "client".cstring; integrity = "".cstring): FetchOptions =
    ## Constructor for `FetchOptions`.
    result = FetchOptions(
      body: body, mode: $mode, credentials: $credentials, cache: $cache, referrerPolicy: $referrerPolicy,
      keepalive: keepalive, redirect: $redirect, referrer: referrer, integrity: integrity,
      metod: (case metod
        of HttpHead:   "HEAD".cstring
        of HttpGet:    "GET".cstring
        of HttpPost:   "POST".cstring
        of HttpPut:    "PUT".cstring
        of HttpDelete: "DELETE".cstring
        of HttpPatch:  "PATCH".cstring
        else:          "GET".cstring
      )
    )

  proc fetch*(url: cstring | Request): Future[Response] {.importjs: "$1(#)".}
    ## `fetch()` API, simple `GET` only, returns a `Future[Response]`.

  proc fetch*(url: cstring | Request; options: FetchOptions): Future[Response] {.importjs: "$1(#, #)".}
    ## `fetch()` API that takes a `FetchOptions`, returns a `Future[Response]`.

  func toCstring*(self: Request | Response | Body | FetchOptions): cstring {.importjs: "JSON.stringify(#)".}

  func `$`*(self: Request | Response | Body | FetchOptions): string = $toCstring(self)


runnableExamples("-d:nimExperimentalJsfetch -r:off"):
  import std/[asyncjs, jsconsole, jsheaders, jsformdata]
  from std/httpcore import HttpMethod
  from std/jsffi import JsObject
  from std/sugar import `=>`

  block:
    let options0: FetchOptions = unsafeNewFetchOptions(
      metod = "POST".cstring,
      body = """{"key": "value"}""".cstring,
      mode = "no-cors".cstring,
      credentials = "omit".cstring,
      cache = "no-cache".cstring,
      referrerPolicy = "no-referrer".cstring,
      keepalive = false,
      redirect = "follow".cstring,
      referrer = "client".cstring,
      integrity = "".cstring
    )
    assert options0.keepalive == false
    assert options0.metod == "POST".cstring
    assert options0.body == """{"key": "value"}""".cstring
    assert options0.mode == "no-cors".cstring
    assert options0.credentials == "omit".cstring
    assert options0.cache == "no-cache".cstring
    assert options0.referrerPolicy == "no-referrer".cstring
    assert options0.redirect == "follow".cstring
    assert options0.referrer == "client".cstring
    assert options0.integrity == "".cstring

  block:
    let options1: FetchOptions = newFetchOptions(
      metod =  HttpPost,
      body = """{"key": "value"}""".cstring,
      mode = fmNoCors,
      credentials = fcOmit,
      cache = fchNoCache,
      referrerPolicy = frpNoReferrer,
      keepalive = false,
      redirect = frFollow,
      referrer = "client".cstring,
      integrity = "".cstring
    )
    assert options1.keepalive == false
    assert options1.metod == $HttpPost
    assert options1.body == """{"key": "value"}""".cstring
    assert options1.mode == $fmNoCors
    assert options1.credentials == $fcOmit
    assert options1.cache == $fchNoCache
    assert options1.referrerPolicy == $frpNoReferrer
    assert options1.redirect == $frFollow
    assert options1.referrer == "client".cstring
    assert options1.integrity == "".cstring

  block:
    let response: Response = newResponse(body = "-. .. --".cstring)
    let request: Request = newRequest(url = "http://nim-lang.org".cstring)

  if not defined(nodejs):
    block:
      proc doFetch(): Future[Response] {.async.} =
        fetch "https://httpbin.org/get".cstring

      proc example() {.async.} =
        let response: Response = await doFetch()
        assert response.ok
        assert response.status == 200.cint
        assert response.headers is Headers
        assert response.body is Body

      discard example()

    when defined(nimExperimentalAsyncjsThen):
      block:
        proc example2 {.async.} =
          await fetch("https://api.github.com/users/torvalds".cstring)
            .then((response: Response) => response.json())
            .then((json: JsObject) => console.log(json))
            .catch((err: Error) => console.log("Request Failed", err))

        discard example2()