package eu.brassepc.fitnessdroid.data

import android.content.Context
import android.content.Intent
import androidx.core.content.FileProvider
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.withContext
import kotlinx.serialization.json.Json
import kotlinx.serialization.json.intOrNull
import kotlinx.serialization.json.jsonObject
import kotlinx.serialization.json.jsonPrimitive
import okhttp3.OkHttpClient
import okhttp3.Request
import java.io.File
import java.security.MessageDigest
import java.util.concurrent.TimeUnit

data class UpdateInfo(
    val versionCode: Long,
    val versionName: String,
    val apkUrl: String,
    val sha256: String?,
)

/**
 * Uppdateringskoll mot släppsidans version.json (skrivs av CI:t).
 * Nedladdning till appens cache + verifiering, sedan Androids
 * installationsdialog — samma signeringsnyckel gör att den uppdaterar
 * rakt över befintlig installation.
 */
class UpdateChecker(private val context: Context) {

    private val http = OkHttpClient.Builder()
        .connectTimeout(10, TimeUnit.SECONDS)
        .readTimeout(120, TimeUnit.SECONDS)
        .build()

    private fun installedVersionCode(): Long =
        context.packageManager.getPackageInfo(context.packageName, 0).longVersionCode

    /** null = uppdaterad, nätfel eller trasig manifest — stör aldrig användaren. */
    suspend fun check(): UpdateInfo? = withContext(Dispatchers.IO) {
        runCatching {
            val request = Request.Builder().url(VERSION_URL).build()
            http.newCall(request).execute().use { response ->
                if (!response.isSuccessful) return@withContext null
                val o = Json.parseToJsonElement(response.body!!.string()).jsonObject
                val info = UpdateInfo(
                    versionCode = (o["versionCode"]?.jsonPrimitive?.intOrNull ?: 0).toLong(),
                    versionName = o["versionName"]?.jsonPrimitive?.content ?: "?",
                    apkUrl = o["apkUrl"]?.jsonPrimitive?.content ?: return@withContext null,
                    sha256 = o["sha256"]?.jsonPrimitive?.content,
                )
                if (info.versionCode > installedVersionCode()) info else null
            }
        }.getOrNull()
    }

    /** Laddar ner APK:n till cachen, verifierar sha256, returnerar filen. */
    suspend fun download(info: UpdateInfo, onProgress: (Float) -> Unit): File =
        withContext(Dispatchers.IO) {
            val dir = File(context.cacheDir, "updates").apply { mkdirs() }
            val file = File(dir, "FitnessDroid-${info.versionCode}.apk")
            val request = Request.Builder().url(info.apkUrl).build()
            http.newCall(request).execute().use { response ->
                if (!response.isSuccessful) error("HTTP ${response.code}")
                val body = response.body!!
                val total = body.contentLength().takeIf { it > 0 }
                val digest = MessageDigest.getInstance("SHA-256")
                body.byteStream().use { input ->
                    file.outputStream().use { output ->
                        val buffer = ByteArray(64 * 1024)
                        var read: Int
                        var done = 0L
                        while (input.read(buffer).also { read = it } != -1) {
                            output.write(buffer, 0, read)
                            digest.update(buffer, 0, read)
                            done += read
                            total?.let { onProgress(done.toFloat() / it) }
                        }
                    }
                }
                val actual = digest.digest().joinToString("") { "%02x".format(it) }
                if (info.sha256 != null && !actual.equals(info.sha256, ignoreCase = true)) {
                    file.delete()
                    error("sha256 stämmer inte — avbryter")
                }
            }
            file
        }

    /** Öppnar Androids installationsdialog för den nedladdade APK:n. */
    fun install(file: File) {
        val uri = FileProvider.getUriForFile(
            context, "${context.packageName}.fileprovider", file,
        )
        context.startActivity(
            Intent(Intent.ACTION_VIEW).apply {
                setDataAndType(uri, "application/vnd.android.package-archive")
                addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION or Intent.FLAG_ACTIVITY_NEW_TASK)
            }
        )
    }

    companion object {
        private const val VERSION_URL =
            "https://gitea.brasse-pc.eu/brasse/FitnessDroid/releases/download/latest/version.json"
    }
}