I'm discovering the use of Google APIs batching ca...

# ktor

[Olivier Patry]

I'm discovering the use of Google APIs batching capabilities and at the same time, trying to use them with Ktor client.
I noticed the MultiPartFormDataContent and ContentType.MultiPart.Mixed.withParameter("boundary", boundary) but I'm a bit lost on the next steps.
Does anyone achieve this already?

[Olivier Patry]

Resources I followed so far:
• https://ktor.io/docs/client-requests.html
• https://developers.google.com/gmail/api/guides/batch
• https://stackoverflow.com/questions/35343365/gmail-rest-api-batch-support-for-getting-messages/35344321#35344321

[Olivier Patry]

So, my main pain point as of today, is to determine how to provide the sub requests given the initial MultiPartFormDataContent

[Olivier Patry]

It seems to work by doing that, but I'm a bit lost on the way to interpret and handle the response

val response = httpClient.post("<https://tasks.googleapis.com/batch>") {
    // FIXME what would be a better boundary name?
    val boundary = "batch_${Clock.System.now().toEpochMilliseconds().toString().encodeBase64()}"
    val contentType = ContentType.MultiPart.Mixed.withParameter("boundary", boundary)
    setBody(
        MultiPartFormDataContent(
            listOf(
                PartData.FormItem(
                    value = "GET /tasks/v1/users/@me/lists HTTP/1.1",
                    dispose = {},
                    partHeaders = headersOf("Content-Type", "application/http"),
                ),
                PartData.FormItem(
                    value = "GET /tasks/v1/users/@me/liPLOPsts HTTP/1.1",
                    dispose = {},
                    partHeaders = headersOf("Content-Type", "application/http"),
                ),
            ),
            boundary,
            contentType
        )
    )
}

[Olivier Patry]

I feel that I missed the point when I have to parse the HTTP body myself while using a tool like Ktor

if (response.status.isSuccess()) {
    val contentType = response.headers["Content-Type"]
        ?: error("No Content-Type header")
    println("Content-Type: $contentType")
    when {
        contentType.startsWith("multipart/mixed") -> {
            val boundary = contentType
                .split("; ")
                .onEach(::println)
                .find { it.startsWith("boundary=") }
                ?.removePrefix("boundary=")
                ?: error("No boundary in Content-Type header")

            val batchBody = response.bodyAsText().removeSuffix("--$boundary--\r\n")
            val parts = batchBody.split("--$boundary").mapNotNull { part ->
                if (part.isBlank()) return@mapNotNull null  // Skip empty segments
                val partData = part.trim().split("\r\n\r\n", limit = 3)
                // TODO check status line
                val body = partData.getOrElse(2) { "" }
                Json.decodeFromString<ResourceListResponse<TaskList>>(body)
            }
                .onEach { println(it) }
        }

        else -> error("Unexpected Content-Type: $contentType")
    }
} else {
    throw ClientRequestException(response, response.bodyAsText())
}

[Olivier Patry]

Ultimately, I'd like to create a HttpResponse from each batch subpart, but can't figure out how to do so.

[Olivier Patry]

I noticed the Multipart.kt impl but struggle to use it for my needs.

I also found https://youtrack.jetbrains.com/issue/KTOR-6632/Support-receiving-multipart-data-with-Ktor-client which goes in the same direction, but using an internal API

[Olivier Patry]

maybe @leonid have some info (being assigned to the issue)

[Osip Fatkullin]

The correct tag is @e5l

[e5l]

Hey, let me try bumping this!

[e5l]

https://github.com/ktorio/ktor/pull/4458