package com.example.otp_kommunikator

import android.content.Context
import net.sqlcipher.database.SQLiteDatabase
import androidx.core.content.ContextCompat
import java.io.File
import java.io.InputStream

fun generateKeyDatabases(
    context: Context,
    keyCount: Int,
    safePinA: CharArray,
    safePinB: CharArray,
    entropyFileUri: android.net.Uri
): String? {
    val sdCardDir = ContextCompat.getExternalFilesDirs(context, null).getOrNull(1) ?: return null
    val entropyStream = context.contentResolver.openInputStream(entropyFileUri) ?: return null

    fun readBytes(stream: InputStream, size: Int): ByteArray {
        val buf = ByteArray(size)
        var total = 0
        while (total < size) {
            val r = stream.read(buf, total, size - total)
            if (r == -1) throw Exception("Zu wenig Entropie in der Datei!")
            total += r
        }
        return buf
    }

    try {
        val saltA = readBytes(entropyStream, 16)
        val saltB = readBytes(entropyStream, 16)

        val masterKeyA = CryptoManager.deriveKeyArgon2(safePinA, saltA)
        val sqlCipherKeyA = CryptoManager.deriveHKDF(masterKeyA, "SQLCIPHER_KEY")
        masterKeyA.fill(0)

        val masterKeyB = CryptoManager.deriveKeyArgon2(safePinB, saltB)
        val sqlCipherKeyB = CryptoManager.deriveHKDF(masterKeyB, "SQLCIPHER_KEY")
        masterKeyB.fill(0)

        val fileA = File(sdCardDir, "Geraet_A_${CryptoManager.byteArrayToHex(saltA)}.db")
        val fileB = File(sdCardDir, "Geraet_B_${CryptoManager.byteArrayToHex(saltB)}.db")

        val dbA = SQLiteDatabase.openOrCreateDatabase(fileA.absolutePath, sqlCipherKeyA, null)
        val dbB = SQLiteDatabase.openOrCreateDatabase(fileB.absolutePath, sqlCipherKeyB, null)
        sqlCipherKeyA.fill(0); sqlCipherKeyB.fill(0)

        val sql = "CREATE TABLE otp_keys (msg_index TEXT, direction TEXT, key_material BLOB, checksum INTEGER)"
        dbA.execSQL(sql)
        dbB.execSQL(sql)
        dbA.execSQL("CREATE TABLE config (config_key TEXT PRIMARY KEY, config_value TEXT)")
        dbB.execSQL("CREATE TABLE config (config_key TEXT PRIMARY KEY, config_value TEXT)")

        val keyLength = 150 + 32
        dbA.execSQL("INSERT INTO config VALUES ('key_length', ?)", arrayOf(keyLength.toString()))
        dbB.execSQL("INSERT INTO config VALUES ('key_length', ?)", arrayOf(keyLength.toString()))

        dbA.beginTransaction()
        dbB.beginTransaction()

        val stmtA = dbA.compileStatement("INSERT INTO otp_keys VALUES (?, ?, ?, ?)")
        val stmtB = dbB.compileStatement("INSERT INTO otp_keys VALUES (?, ?, ?, ?)")

        for (i in 0 until keyCount) {
            // Richtung A -> B
            val idAtoB = CryptoManager.byteArrayToHex(readBytes(entropyStream, 8))
            val materialAtoB = readBytes(entropyStream, keyLength)
            val crcAtoB = CryptoManager.calculateChecksum(materialAtoB)

            stmtA.bindString(1, idAtoB); stmtA.bindString(2, "SEND"); stmtA.bindBlob(3, materialAtoB); stmtA.bindLong(4, crcAtoB); stmtA.executeInsert(); stmtA.clearBindings()
            stmtB.bindString(1, idAtoB); stmtB.bindString(2, "RECEIVE"); stmtB.bindBlob(3, materialAtoB); stmtB.bindLong(4, crcAtoB); stmtB.executeInsert(); stmtB.clearBindings()

            // Richtung B -> A
            val idBtoA = CryptoManager.byteArrayToHex(readBytes(entropyStream, 8))
            val materialBtoA = readBytes(entropyStream, keyLength)
            val crcBtoA = CryptoManager.calculateChecksum(materialBtoA)

            stmtA.bindString(1, idBtoA); stmtA.bindString(2, "RECEIVE"); stmtA.bindBlob(3, materialBtoA); stmtA.bindLong(4, crcBtoA); stmtA.executeInsert(); stmtA.clearBindings()
            stmtB.bindString(1, idBtoA); stmtB.bindString(2, "SEND"); stmtB.bindBlob(3, materialBtoA); stmtB.bindLong(4, crcBtoA); stmtB.executeInsert(); stmtB.clearBindings()
        }

        dbA.setTransactionSuccessful()
        dbB.setTransactionSuccessful()
        dbA.endTransaction()
        dbB.endTransaction()
        dbA.close()
        dbB.close()

        return sdCardDir.absolutePath
    } finally {
        entropyStream.close()
    }
}