/*
 * Copyright 2014-2024 JetBrains s.r.o and contributors. Use of this source code is governed by the Apache 2.0 license.
 */

package io.ktor.client.engine.cio

import io.ktor.client.call.*
import io.ktor.client.engine.*
import io.ktor.client.request.*
import io.ktor.client.utils.*
import io.ktor.http.*
import io.ktor.http.cio.*
import io.ktor.http.content.*
import io.ktor.util.date.*
import io.ktor.utils.io.*
import io.ktor.utils.io.CancellationException
import io.ktor.websocket.*
import kotlinx.coroutines.*
import kotlinx.io.IOException
import kotlin.coroutines.*

internal suspend fun writeRequest(
    request: HttpRequestData,
    output: ByteWriteChannel,
    callContext: CoroutineContext,
    overProxy: Boolean,
    closeChannel: Boolean = true
) = withContext(callContext) {
    writeHeaders(request, output, overProxy, closeChannel)
    writeBody(request, output, callContext)
}

@OptIn(InternalAPI::class)
internal suspend fun writeHeaders(
    request: HttpRequestData,
    output: ByteWriteChannel,
    overProxy: Boolean,
    closeChannel: Boolean = true
) {
    val builder = RequestResponseBuilder()

    val method = request.method
    val url = request.url
    val headers = request.headers
    val body = request.body

    val contentLength = headers[HttpHeaders.ContentLength] ?: body.contentLength?.toString()
    val contentEncoding = headers[HttpHeaders.TransferEncoding]
    val responseEncoding = body.headers[HttpHeaders.TransferEncoding]
    val chunked = isChunked(contentLength, responseEncoding, contentEncoding)
    val expected = headers[HttpHeaders.Expect]

    try {
        val normalizedUrl = if (url.rawSegments.isEmpty()) URLBuilder(url).apply { encodedPath = "/" }.build() else url
        val urlString = if (overProxy) normalizedUrl.toString() else normalizedUrl.fullPath

        builder.requestLine(method, urlString, HttpProtocolVersion.HTTP_1_1.toString())
        // this will only add the port to the host header if the port is non-standard for the protocol
        if (!headers.contains(HttpHeaders.Host)) {
            val host = if (url.protocol.defaultPort == url.port) {
                url.host
            } else {
                url.hostWithPort
            }
            builder.headerLine(HttpHeaders.Host, host)
        }

        if (contentLength != null) {
            if ((method != HttpMethod.Get && method != HttpMethod.Head) || body !is OutgoingContent.NoContent) {
                builder.headerLine(HttpHeaders.ContentLength, contentLength)
            }
        }

        mergeHeaders(headers, body) { key, value ->
            if (key == HttpHeaders.ContentLength || key == HttpHeaders.Expect) return@mergeHeaders

            builder.headerLine(key, value)
        }

        if (chunked && contentEncoding == null && responseEncoding == null && body !is OutgoingContent.NoContent) {
            builder.headerLine(HttpHeaders.TransferEncoding, "chunked")
        }

        if (expectContinue(expected, body)) {
            builder.headerLine(HttpHeaders.Expect, expected!!)
        }

        builder.emptyLine()
        output.writePacket(builder.build())
        output.flush()
    } catch (cause: Throwable) {
        if (closeChannel) {
            output.flushAndClose()
        }
        throw cause
    } finally {
        builder.release()
    }
}

@Suppress("TYPEALIAS_EXPANSION_DEPRECATION", "DEPRECATION")
internal suspend fun writeBody(
    request: HttpRequestData,
    output: ByteWriteChannel,
    callContext: CoroutineContext,
    closeChannel: Boolean = true
) {
    val body = request.body.getUnwrapped()
    if (body is OutgoingContent.NoContent) {
        if (closeChannel) output.close()
        return
    }
    if (body is OutgoingContent.ProtocolUpgrade) {
        throw UnsupportedContentTypeException(body)
    }

    val contentLength = request.headers[HttpHeaders.ContentLength] ?: body.contentLength?.toString()
    val contentEncoding = request.headers[HttpHeaders.TransferEncoding]
    val responseEncoding = body.headers[HttpHeaders.TransferEncoding]
    val chunked = isChunked(contentLength, responseEncoding, contentEncoding)

    val chunkedJob: EncoderJob? = if (chunked) encodeChunked(output, callContext) else null
    val channel = chunkedJob?.channel ?: output

    val scope = CoroutineScope(callContext + CoroutineName("cio-client-body-writer"))
    scope.launch {
        try {
            processOutgoingContent(request, body, channel)
        } catch (cause: Throwable) {
            channel.close(cause)
            throw cause
        } finally {
            channel.flush()
            chunkedJob?.channel?.close()
            chunkedJob?.join()

            output.closedCause?.unwrapCancellationException()?.takeIf { it !is CancellationException }?.let {
                throw it
            }
            if (closeChannel) {
                output.close()
            }
        }
    }
}

private fun OutgoingContent.getUnwrapped(): OutgoingContent = when (this) {
    is OutgoingContent.ContentWrapper -> delegate().getUnwrapped()
    else -> this
}

private suspend fun processOutgoingContent(request: HttpRequestData, body: OutgoingContent, channel: ByteWriteChannel) {
    when (body) {
        is OutgoingContent.ByteArrayContent -> channel.writeFully(body.bytes())
        is OutgoingContent.ReadChannelContent -> body.readFrom().copyAndClose(channel)
        is OutgoingContent.WriteChannelContent -> body.writeTo(channel)
        is OutgoingContent.ContentWrapper -> processOutgoingContent(request, body.delegate(), channel)
        is OutgoingContent.ProtocolUpgrade -> error("unreachable code")
        is OutgoingContent.NoContent -> error("unreachable code")
    }
}

@OptIn(InternalAPI::class)
internal suspend fun readResponse(
    requestTime: GMTDate,
    request: HttpRequestData,
    input: ByteReadChannel,
    output: ByteWriteChannel,
    callContext: CoroutineContext
): HttpResponseData = withContext(callContext) {
    val rawResponse = parseResponse(input)
        ?: throw kotlinx.io.EOFException("Failed to parse HTTP response: the server prematurely closed the connection")

    rawResponse.use {
        val status = HttpStatusCode(rawResponse.status, rawResponse.statusText.toString())
        val contentLength = rawResponse.headers[HttpHeaders.ContentLength]?.toString()?.toLong() ?: -1L
        val transferEncoding = rawResponse.headers[HttpHeaders.TransferEncoding]?.toString()
        val connectionType = ConnectionOptions.parse(rawResponse.headers[HttpHeaders.Connection])

        val rawHeaders = rawResponse.headers
        val headers = HeadersImpl(rawHeaders.toMap())
        val version = HttpProtocolVersion.parse(rawResponse.version)

        if (status == HttpStatusCode.SwitchingProtocols) {
            val session = RawWebSocket(input, output, masking = true, coroutineContext = callContext)
            return@withContext HttpResponseData(status, requestTime, headers, version, session, callContext)
        }

        val body = when {
            request.method == HttpMethod.Head ||
                status in listOf(HttpStatusCode.NotModified, HttpStatusCode.NoContent) ||
                status.isInformational() -> {
                ByteReadChannel.Empty
            }

            else -> {
                val coroutineScope = CoroutineScope(callContext + CoroutineName("cio-client-body-reader"))
                val httpBodyParser = coroutineScope.writer(autoFlush = true) {
                    parseHttpBody(version, contentLength, transferEncoding, connectionType, input, channel)
                }
                httpBodyParser.channel
            }
        }

        val responseBody: Any = request.attributes.getOrNull(ResponseAdapterAttributeKey)
            ?.adapt(request, status, headers, body, request.body, callContext)
            ?: body

        return@withContext HttpResponseData(status, requestTime, headers, version, responseBody, callContext)
    }
}

internal suspend fun startTunnel(
    request: HttpRequestData,
    output: ByteWriteChannel,
    input: ByteReadChannel
) {
    val builder = RequestResponseBuilder()

    try {
        val hostWithPort = request.url.hostWithPort
        builder.requestLine(HttpMethod("CONNECT"), hostWithPort, HttpProtocolVersion.HTTP_1_1.toString())
        builder.headerLine(HttpHeaders.Host, hostWithPort)
        builder.headerLine("Proxy-Connection", "Keep-Alive") // For HTTP/1.0 proxies like Squid.
        request.headers[HttpHeaders.UserAgent]?.let {
            builder.headerLine(HttpHeaders.UserAgent, it)
        }
        request.headers[HttpHeaders.ProxyAuthenticate]?.let {
            builder.headerLine(HttpHeaders.ProxyAuthenticate, it)
        }
        request.headers[HttpHeaders.ProxyAuthorization]?.let {
            builder.headerLine(HttpHeaders.ProxyAuthorization, it)
        }

        builder.emptyLine()
        output.writePacket(builder.build())
        output.flush()

        val rawResponse = parseResponse(input)
            ?: throw kotlinx.io.EOFException("Failed to parse CONNECT response: unexpected EOF")
        rawResponse.use {
            if (rawResponse.status / 200 != 1) {
                throw IOException("Can not establish tunnel connection")
            }
            rawResponse.headers[HttpHeaders.ContentLength]?.let {
                input.discard(it.toString().toLong())
            }
        }
    } finally {
        builder.release()
    }
}

internal fun HttpHeadersMap.toMap(): Map<String, List<String>> {
    val result = mutableMapOf<String, MutableList<String>>()

    for (offset in offsets()) {
        val key = nameAtOffset(offset).toString()
        val value = valueAtOffset(offset).toString()

        if (result[key]?.add(value) == null) {
            result[key] = mutableListOf(value)
        }
    }

    return result
}

internal fun HttpStatusCode.isInformational(): Boolean = (value / 100) == 1

/**
 * Wrap channel so that [ByteWriteChannel.close] of the resulting channel doesn't lead to closing of the base channel.
 */
@OptIn(DelicateCoroutinesApi::class)
internal fun ByteWriteChannel.withoutClosePropagation(
    coroutineContext: CoroutineContext,
    closeOnCoroutineCompletion: Boolean = true
): ByteWriteChannel {
    if (closeOnCoroutineCompletion) {
        // Pure output represents a socket output channel that is closed when request fully processed or after
        // request sent in case TCP half-close is allowed.
        coroutineContext.job.invokeOnCompletion {
            close(it)
        }
    }

    return GlobalScope.reader(coroutineContext, autoFlush = true) {
        channel.copyTo(this@withoutClosePropagation, Long.MAX_VALUE)
        this@withoutClosePropagation.flush()
    }.channel
}

/**
 * Wrap channel using [withoutClosePropagation] if [propagateClose] is false otherwise return the same channel.
 */
internal fun ByteWriteChannel.handleHalfClosed(
    coroutineContext: CoroutineContext,
    propagateClose: Boolean
): ByteWriteChannel = if (propagateClose) this else withoutClosePropagation(coroutineContext)

internal fun isChunked(
    contentLength: String?,
    responseEncoding: String?,
    contentEncoding: String?
) = contentLength == null || responseEncoding == "chunked" || contentEncoding == "chunked"

internal fun expectContinue(expectHeader: String?, body: OutgoingContent) =
    expectHeader != null && body !is OutgoingContent.NoContent
