ariane/app/src/main/java/oppen/ariane/io/gemini/GeminiDatasource.kt

package oppen.ariane.io.gemini

import android.content.Context
import androidx.core.net.toUri
import androidx.preference.PreferenceManager
import kotlinx.coroutines.GlobalScope
import kotlinx.coroutines.launch
import oppen.ariane.io.GemState
import java.io.*
import java.net.ConnectException
import java.net.URI
import java.security.SecureRandom
import java.security.cert.X509Certificate
import javax.net.ssl.*

const val GEMINI_SCHEME = "gemini"

/**
 *
 *
 * @param protocol see: https://docs.oracle.com/javase/7/docs/technotes/guides/security/StandardNames.html#SSLContext
 *
 */
class GeminiDatasource(
    private val context: Context): Datasource {

    private val prefs = PreferenceManager.getDefaultSharedPreferences(context)
    private var last: URI? = null

    override fun request(uri: URI, onUpdate: (state: GemState) -> Unit) {

        //Any inputted uri starting with a colon is an app-specific command, eg. :prefs :settings
        if(uri.toString().startsWith(":")){
            onUpdate(GemState.AppQuery(uri))
            return
        }

        when (uri.scheme) {
            GEMINI_SCHEME -> {
                val cached = RuntimeCache.get(uri)
                if(cached != null){
                    last = uri
                    onUpdate(
                        GemState.ResponseGemtext(
                            uri,
                            cached.first,
                            cached.second
                        )
                    )
                    return
                }else{
                    onUpdate(GemState.Requesting(uri))

                    GlobalScope.launch {
                        geminiRequest(uri, onUpdate)
                    }
                }
            }
            else -> {
                val address = uri.toString()
                val parsedUri = when {
                    address.startsWith("//") -> {
                        //just missing protocol
                        URI.create("gemini:$address")
                    }
                    address.startsWith("/") -> {
                        //internal navigation
                        val internalNav = "gemini://${last?.host}$address"
                        URI.create(internalNav)
                    }
                    !address.contains("://") -> {
                        //looks like a relative link
                        val lastAddress = last.toString()
                        val relAddress = "${lastAddress.substring(0, lastAddress.lastIndexOf("/") + 1)}$address"
                        URI.create(relAddress)
                    }
                    else -> {
                        onUpdate(GemState.NotGeminiRequest(uri))
                        return
                    }
                }

                val cached = RuntimeCache.get(parsedUri)
                if(cached != null){
                    last = parsedUri
                    onUpdate(
                        GemState.ResponseGemtext(
                            parsedUri,
                            cached.first,
                            cached.second
                        )
                    )
                }else{
                    request(parsedUri, onUpdate)
                }
            }
        }
    }

    /**
     *
     * This was originally largely copied from:

        https://framagit.org/waweic/gemini-client/-/blob/master/app/src/main/java/rocks/ism/decentral/geminiclient/GeminiConnection.kt
     *
     */

    private val trustAllCerts: Array<TrustManager> = arrayOf(object : X509TrustManager {
            override fun checkClientTrusted(chain: Array<out X509Certificate>?, authType: String?) {

            }

            override fun checkServerTrusted(chain: Array<out X509Certificate>?, authType: String?) {
                println("checkServerTrusted()")
                println("checkServerTrusted() authType: $authType")
                chain?.forEach { cert ->
                    println("checkServerTrusted() cert: ${cert.subjectDN}")
                }
            }

            override fun getAcceptedIssuers(): Array<X509Certificate> {
                return arrayOf()
            }
        })


    private fun geminiRequest(uri: URI, onUpdate: (state: GemState) -> Unit){
        last = uri
        val port = if(uri.port == -1) 1965 else uri.port

        val protocol = prefs.getString("tls_protocol", "TLS")

        println("REQ_PROTOCOL: $protocol")

        val sslContext = SSLContext.getInstance(protocol)
        sslContext.init(null, trustAllCerts, SecureRandom())

        val factory: SSLSocketFactory = sslContext.socketFactory

        val socket: SSLSocket?
        try {
            socket = factory.createSocket(uri.host, port) as SSLSocket
            socket.enabledCipherSuites = factory.supportedCipherSuites

            when (protocol) {
                "TLS" -> socket.enabledProtocols = socket.supportedProtocols
                else -> socket.enabledProtocols = arrayOf(protocol)
            }

            socket.startHandshake()
        }catch(ce: ConnectException){
            println("socket error: $ce")
            onUpdate(
                GemState.ResponseError(
                    GeminiResponse.Header(
                        -1,
                        ce.message ?: ce.toString()
                    )
                )
            )
            return
        }catch(she: SSLHandshakeException){
            println("socket error: $she")
            onUpdate(
                GemState.ResponseError(
                    GeminiResponse.Header(
                        -2,
                        she.message ?: she.toString()
                    )
                )
            )
            return
        }


        // OUT >>>>>>>>>>>>>>>>>>>>>>>>>>
        val outputStreamWriter = OutputStreamWriter(socket.outputStream)
        val bufferedWriter = BufferedWriter(outputStreamWriter)
        val outWriter = PrintWriter(bufferedWriter)

        outWriter.print(uri.toString() + "\r\n")
        outWriter.flush()

        if (outWriter.checkError()) {
            onUpdate(
                GemState.ResponseError(
                    GeminiResponse.Header(
                        -1,
                        "Print Writer Error"
                    )
                )
            )
            outWriter.close()
            return
        }

        // IN <<<<<<<<<<<<<<<<<<<<<<<<<<<

        val inputStream = socket.inputStream
        val headerInputReader = InputStreamReader(inputStream)
        val bufferedReader = BufferedReader(headerInputReader)
        val headerLine = bufferedReader.readLine()

        println("Ariane: response header: $headerLine")

        val header = GeminiResponse.parseHeader(headerLine)

        when {
            header.code == GeminiResponse.INPUT -> onUpdate(GemState.ResponseInput(uri, header))
            header.code == GeminiResponse.REDIRECT -> request(URI.create(header.meta), onUpdate)
            header.code != GeminiResponse.SUCCESS -> onUpdate(GemState.ResponseError(header))
            header.meta.startsWith("text/gemini") -> getGemtext(bufferedReader, uri, header, onUpdate)
            header.meta.startsWith("text/") -> getString(socket, uri, header, onUpdate)
            header.meta.startsWith("image/") -> getBinary(socket, uri, header, onUpdate)
            header.meta.startsWith("audio/") -> getBinary(socket, uri, header, onUpdate)
            else -> onUpdate(GemState.ResponseError(header))
        }

        //Close input
        bufferedReader.close()
        headerInputReader.close()

        //Close output:
        outputStreamWriter.close()
        bufferedWriter.close()
        outWriter.close()

        socket.close()
    }

    private fun getGemtext(reader: BufferedReader, uri: URI, header: GeminiResponse.Header, onUpdate: (state: GemState) -> Unit){

        val lines = mutableListOf<String>()

        lines.addAll(reader.readLines())

        val processed = GemtextHelper.findCodeBlocks(lines)

        when {
            uri.toString().startsWith("gemini://") -> RuntimeCache.put(uri, header, processed)
        }

        onUpdate(GemState.ResponseGemtext(uri, header, processed))
    }

    private fun getString(socket: SSLSocket?, uri: URI, header: GeminiResponse.Header, onUpdate: (state: GemState) -> Unit){
        val content = socket?.inputStream?.bufferedReader().use { reader -> reader?.readText() }
        socket?.close()
        onUpdate(GemState.ResponseText(uri, header, content ?: "Error fetching content"))
    }

    private fun getBinary(socket: SSLSocket?, uri: URI, header: GeminiResponse.Header, onUpdate: (state: GemState) -> Unit){

        val filenameRegex = Regex("[^A-Za-z0-9]")
        val cacheFile = File(context.cacheDir, filenameRegex.replace(uri.path, "_"))

        when {
            cacheFile.exists() -> {
                when {
                    header.meta.startsWith("image/") -> onUpdate(GemState.ResponseImage(uri, header, cacheFile.toUri()))
                    header.meta.startsWith("audio/") -> onUpdate(GemState.ResponseAudio(uri, header, cacheFile.toUri()))
                }

            }
            else -> {
                cacheFile.createNewFile()
                cacheFile.outputStream().use{ outputStream ->
                    socket?.inputStream?.copyTo(outputStream)
                    socket?.close()
                }

                when {
                    header.meta.startsWith("image/") -> onUpdate(GemState.ResponseImage(uri, header, cacheFile.toUri()))
                    header.meta.startsWith("audio/") -> onUpdate(GemState.ResponseAudio(uri, header, cacheFile.toUri()))
                }
            }
        }
    }
}