/*
 * SPDX-FileCopyrightText: 2023 Linnea Gräf <nea@nea.moe>
 * SPDX-FileCopyrightText: 2024 Linnea Gräf <nea@nea.moe>
 *
 * SPDX-License-Identifier: GPL-3.0-or-later
 */

package moe.nea.firmament.repo

import io.ktor.client.call.body
import io.ktor.client.request.get
import io.ktor.client.statement.bodyAsChannel
import io.ktor.utils.io.jvm.nio.copyTo
import java.io.IOException
import java.nio.file.Files
import java.nio.file.Path
import java.nio.file.StandardOpenOption
import java.util.zip.ZipInputStream
import kotlinx.coroutines.CoroutineName
import kotlinx.coroutines.Dispatchers.IO
import kotlinx.coroutines.withContext
import kotlinx.serialization.Serializable
import kotlin.io.path.createDirectories
import kotlin.io.path.exists
import kotlin.io.path.inputStream
import kotlin.io.path.outputStream
import kotlin.io.path.readText
import kotlin.io.path.writeText
import moe.nea.firmament.Firmament
import moe.nea.firmament.Firmament.logger
import moe.nea.firmament.util.iterate


object RepoDownloadManager {

    val repoSavedLocation = Firmament.DATA_DIR.resolve("repo-extracted")
    val repoMetadataLocation = Firmament.DATA_DIR.resolve("loaded-repo-sha.txt")

    private fun loadSavedVersionHash(): String? =
        if (repoSavedLocation.exists()) {
            if (repoMetadataLocation.exists()) {
                try {
                    repoMetadataLocation.readText().trim()
                } catch (e: IOException) {
                    null
                }
            } else {
                null
            }
        } else null

    private fun saveVersionHash(versionHash: String) {
        latestSavedVersionHash = versionHash
        repoMetadataLocation.writeText(versionHash)
    }

    var latestSavedVersionHash: String? = loadSavedVersionHash()
        private set

    @Serializable
    private class GithubCommitsResponse(val sha: String)

    private suspend fun requestLatestGithubSha(): String? {
        if (RepoManager.Config.branch == "prerelease") {
            RepoManager.Config.branch = "master"
        }
        val response =
            Firmament.httpClient.get("https://api.github.com/repos/${RepoManager.Config.username}/${RepoManager.Config.reponame}/commits/${RepoManager.Config.branch}")
        if (response.status.value != 200) {
            return null
        }
        return response.body<GithubCommitsResponse>().sha
    }

    private suspend fun downloadGithubArchive(url: String): Path = withContext(IO) {
        val response = Firmament.httpClient.get(url)
        val targetFile = Files.createTempFile("firmament-repo", ".zip")
        val outputChannel = Files.newByteChannel(targetFile, StandardOpenOption.CREATE, StandardOpenOption.WRITE)
        response.bodyAsChannel().copyTo(outputChannel)
        targetFile
    }

    /**
     * Downloads the latest repository from github, setting [latestSavedVersionHash].
     * @return true, if an update was performed, false, otherwise (no update needed, or wasn't able to complete update)
     */
    suspend fun downloadUpdate(force: Boolean): Boolean = withContext(CoroutineName("Repo Update Check")) {
        val latestSha = requestLatestGithubSha()
        if (latestSha == null) {
            logger.warn("Could not request github API to retrieve latest REPO sha.")
            return@withContext false
        }
        val currentSha = loadSavedVersionHash()
        if (latestSha != currentSha || force) {
            val requestUrl =
                "https://github.com/${RepoManager.Config.username}/${RepoManager.Config.reponame}/archive/$latestSha.zip"
            logger.info("Planning to upgrade repository from $currentSha to $latestSha from $requestUrl")
            val zipFile = downloadGithubArchive(requestUrl)
            logger.info("Download repository zip file to $zipFile. Deleting old repository")
            withContext(IO) { repoSavedLocation.toFile().deleteRecursively() }
            logger.info("Extracting new repository")
            withContext(IO) { extractNewRepository(zipFile) }
            logger.info("Repository loaded on disk.")
            saveVersionHash(latestSha)
            return@withContext true
        } else {
            logger.debug("Repository on latest sha $currentSha. Not performing update")
            return@withContext false
        }
    }

    private fun extractNewRepository(zipFile: Path) {
        repoSavedLocation.createDirectories()
        ZipInputStream(zipFile.inputStream()).use { cis ->
            while (true) {
                val entry = cis.nextEntry ?: break
                if (entry.isDirectory) continue
                val extractedLocation =
                    repoSavedLocation.resolve(
                        entry.name.substringAfter('/', missingDelimiterValue = "")
                    )
                if (repoSavedLocation !in extractedLocation.iterate { it.parent }) {
                    logger.error("Firmament detected an invalid zip file. This is a potential security risk, please report this in the Firmament discord.")
                    throw RuntimeException("Firmament detected an invalid zip file. This is a potential security risk, please report this in the Firmament discord.")
                }
                extractedLocation.parent.createDirectories()
                extractedLocation.outputStream().use { cis.copyTo(it) }
            }
        }
    }


}