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 oppen.isGemini
import oppen.toURI
import oppen.toUri
import java.io.*
import java.lang.IllegalStateException
import java.net.ConnectException
import java.net.URI
import javax.net.ssl.*

const val GEMINI_SCHEME = "gemini"

class GeminiDatasource(private val context: Context): Datasource {

    private val prefs = PreferenceManager.getDefaultSharedPreferences(context)
    private val addressBuilder = AddressBuilder()
    private val runtimeHistory = mutableListOf<URI>()
    private var forceDownload = false

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

    override fun request(uri: URI, forceDownload: Boolean, onUpdate: (state: GemState) -> Unit) {
        this.forceDownload = forceDownload
        //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 -> {
                addressBuilder.set(uri.toUri())
                val cached = RuntimeCache.get(uri)
                when {
                    cached != null -> {
                        onUpdate(GemState.ResponseGemtext(uri, cached.first, cached.second))
                        return
                    }
                    else -> {
                        onUpdate(GemState.Requesting(uri))

                        GlobalScope.launch {
                            geminiRequest(uri, onUpdate)
                        }
                    }
                }
            }
            else -> {
                val parsedUri = addressBuilder.request(uri).uri()
                if(parsedUri.isGemini()){
                    val cached = RuntimeCache.get(parsedUri)
                    when {
                        cached != null -> onUpdate(GemState.ResponseGemtext(parsedUri.toURI(), cached.first, cached.second))
                        else -> request(parsedUri.toURI(), forceDownload, onUpdate)
                    }
                }else{
                    onUpdate(GemState.NotGeminiRequest(uri))
                    return
                }
            }
        }
    }

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

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

        println("REQ_PROTOCOL: $protocol")

        //todo - extract and reuse this
        val sslContext = when (protocol) {
            "TLS_ALL" -> SSLContext.getInstance("TLS")
            else -> SSLContext.getInstance(protocol)
        }

        sslContext.init(null, DummyTrustManager.get(), null)
        val factory: SSLSocketFactory = sslContext.socketFactory

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

            when (protocol) {
                "TLS" -> {}//Use default enabled protocols
                "TLS_ALL" -> 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), forceDownload, 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 -> {
                //File served over Gemini but not handled in-app, eg .pdf
                if(forceDownload){
                    getBinary(socket, uri, header, onUpdate)
                }else{
                    onUpdate(GemState.ResponseUnknownMime(uri, 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://") -> throw IllegalStateException("Not a Gemini Uri")
        }

        RuntimeCache.put(uri, header, processed)

        if(runtimeHistory.isEmpty() || runtimeHistory.last().toString() != uri.toString()) runtimeHistory.add(uri)

        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){

        var filename: String? = null
        val fileSegmentIndex: Int = uri.path.lastIndexOf('/')

        when {
            fileSegmentIndex != -1 -> filename = uri.path.substring(fileSegmentIndex + 1)
        }

        val host = uri.host.replace(".", "_")
        val cacheName = "${host}_$filename"
        println("Caching file: $filename from uri: $uri, cacheName: $cacheName")

        val cacheFile = File(context.cacheDir, cacheName)

        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 -> onUpdate(GemState.ResponseBinary(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()))
                    else -> onUpdate(GemState.ResponseBinary(uri, header, cacheFile.toUri()))
                }
            }
        }
    }

    override fun canGoBack(): Boolean = runtimeHistory.size > 1

    override fun goBack(onUpdate: (state: GemState) -> Unit) {
        runtimeHistory.removeLast()
        request(runtimeHistory.last(), onUpdate)
    }
}