diff --git a/app/src/main/kotlin/docthor/app/App.kt b/app/src/main/kotlin/docthor/app/App.kt
index 8426865..388d7b7 100644
--- a/app/src/main/kotlin/docthor/app/App.kt
+++ b/app/src/main/kotlin/docthor/app/App.kt
@@ -6,10 +6,12 @@ import com.github.ajalt.clikt.parameters.options.option
 import com.github.ajalt.clikt.parameters.options.required
 import com.github.ajalt.clikt.parameters.types.enum
 import com.github.ajalt.clikt.parameters.types.file
+import de.itkl.textprocessing.TextFile
 import de.itkl.tfidf.Language
 import de.itkl.tfidf.TfIdf
+import de.itkl.tfidf.TfIdfPipeline
+import kotlinx.coroutines.flow.take
 import kotlinx.coroutines.runBlocking
-import java.io.File
 
 class ComputeTf : CliktCommand() {
     private val corpus  by option(help = "corpus")
@@ -20,13 +22,17 @@ class ComputeTf : CliktCommand() {
         .required()
 
     override fun run() = runBlocking {
-        val tfIdf = TfIdf()
-        val histogram = tfIdf.computeTf(
-            corpus,
-            language
-        )
-        tfIdf.normalizeTf(histogram, corpus.toPath().parent.resolve("${corpus.nameWithoutExtension}-tf.csv").toFile())
-
+        TfIdfPipeline(language = Language.DE)
+            .input(corpus)
+//        TextFile(corpus).splitByEmptyLines()
+//            .take(10)
+//            .collect { println(it) }
+//        val tfIdf = TfIdf()
+//        val histogram = tfIdf.computeTf(
+//            corpus,
+//            language
+//        )
+//        val tf = tfIdf.normalizeTf(histogram, corpus.toPath().parent.resolve("${corpus.nameWithoutExtension}-tf.csv").toFile())
     }
 }
 
diff --git a/libraries/fileprocessing/build.gradle.kts b/libraries/fileprocessing/build.gradle.kts
new file mode 100644
index 0000000..c74f63c
--- /dev/null
+++ b/libraries/fileprocessing/build.gradle.kts
@@ -0,0 +1,7 @@
+plugins {
+    id("docthor.kotlin-library-conventions")
+}
+
+dependencies {
+    implementation("org.jetbrains.kotlinx:kotlinx-coroutines-core:1.7.3")
+}
diff --git a/libraries/fileprocessing/src/main/kotlin/de/itkl/fileprocessing/FileProcessor.kt b/libraries/fileprocessing/src/main/kotlin/de/itkl/fileprocessing/FileProcessor.kt
new file mode 100644
index 0000000..3f156a0
--- /dev/null
+++ b/libraries/fileprocessing/src/main/kotlin/de/itkl/fileprocessing/FileProcessor.kt
@@ -0,0 +1,10 @@
+package de.itkl.fileprocessing
+
+import java.io.File
+import java.io.InputStream
+import java.nio.file.Path
+
+interface FileProcessor {
+    fun willProduce(path: Path): Path
+    suspend fun process(resource: Resource): File
+}
\ No newline at end of file
diff --git a/libraries/fileprocessing/src/main/kotlin/de/itkl/fileprocessing/ProcessingPipeline.kt b/libraries/fileprocessing/src/main/kotlin/de/itkl/fileprocessing/ProcessingPipeline.kt
new file mode 100644
index 0000000..04a7872
--- /dev/null
+++ b/libraries/fileprocessing/src/main/kotlin/de/itkl/fileprocessing/ProcessingPipeline.kt
@@ -0,0 +1,25 @@
+package de.itkl.fileprocessing
+
+import io.github.oshai.kotlinlogging.KotlinLogging
+import java.io.File
+import kotlin.io.path.exists
+
+private val Log = KotlinLogging.logger { }
+
+abstract class FileProcessingPipeline {
+
+    protected abstract val fileProcessor: List<FileProcessor>
+    suspend fun input(file: File) {
+        var currentFile = file
+        fileProcessor.forEach { processor ->
+            val target = processor.willProduce(currentFile.toPath())
+            if(target.exists()) {
+                Log.info { "$target exists. Skipping" } 
+            } else {
+                Log.info { "$target does not exists. Creating" }
+                processor.process(FileResource(currentFile))
+            }
+            currentFile = target.toFile()
+        }
+    }
+}
\ No newline at end of file
diff --git a/libraries/fileprocessing/src/main/kotlin/de/itkl/fileprocessing/ProgressInputStream.kt b/libraries/fileprocessing/src/main/kotlin/de/itkl/fileprocessing/ProgressInputStream.kt
new file mode 100644
index 0000000..fceb3bb
--- /dev/null
+++ b/libraries/fileprocessing/src/main/kotlin/de/itkl/fileprocessing/ProgressInputStream.kt
@@ -0,0 +1,39 @@
+package de.itkl.fileprocessing
+
+import java.io.InputStream
+
+/**
+ * Represents an input stream that tracks the progress of reading from an underlying input stream.
+ *
+ * @property inputStream The underlying input stream to read from.
+ * @property updateOp The operation to be executed when the number of bytes read changes.
+ * @property bytesRead The number of bytes read from the input stream.
+ */
+class ProgressInputStream(
+    private val inputStream: InputStream,
+    private val updateOp: (Long) -> Unit) : InputStream() {
+    @Volatile
+    var bytesRead: Long = 0
+        private set(value) {
+            field = value
+            updateOp(value)
+        }
+
+    override fun read(): Int {
+        val byte = inputStream.read()
+        if (byte != -1) {
+            bytesRead++
+        }
+        return byte
+    }
+    override fun read(b: ByteArray, off: Int, len: Int): Int {
+        val bytesRead = inputStream.read(b, off, len)
+        if (bytesRead != -1) {
+            this.bytesRead += bytesRead
+        }
+        return bytesRead
+    }
+    override fun read(b: ByteArray): Int {
+        return this.read(b, 0, b.size)
+    }
+}
\ No newline at end of file
diff --git a/libraries/fileprocessing/src/main/kotlin/de/itkl/fileprocessing/Resource.kt b/libraries/fileprocessing/src/main/kotlin/de/itkl/fileprocessing/Resource.kt
new file mode 100644
index 0000000..4955bdd
--- /dev/null
+++ b/libraries/fileprocessing/src/main/kotlin/de/itkl/fileprocessing/Resource.kt
@@ -0,0 +1,34 @@
+package de.itkl.fileprocessing
+
+import java.io.File
+import java.io.InputStream
+import java.nio.file.Files
+import java.nio.file.Path
+
+interface Resource {
+    val path: Path
+    val size: Long
+    fun toFile(): File = path.toFile()
+    fun read(): InputStream
+}
+
+class ProgressResource(
+    private val resource: Resource,
+    private val progressOpSupplier: () -> (Long) -> Unit
+) : Resource by resource
+{
+    override fun read(): InputStream {
+        return ProgressInputStream(
+            read(),
+            progressOpSupplier()
+        )
+    }
+}
+
+class FileResource(override val path: Path) : Resource {
+    constructor(file: File): this(file.toPath())
+    override val size: Long by lazy { path.toFile().length() }
+    override fun read(): InputStream {
+        return Files.newInputStream(path)
+    }
+}
\ No newline at end of file
diff --git a/libraries/fileprocessing/src/main/kotlin/de/itkl/processing/ParallelFlowProcessor.kt b/libraries/fileprocessing/src/main/kotlin/de/itkl/processing/ParallelFlowProcessor.kt
new file mode 100644
index 0000000..0564950
--- /dev/null
+++ b/libraries/fileprocessing/src/main/kotlin/de/itkl/processing/ParallelFlowProcessor.kt
@@ -0,0 +1,25 @@
+package de.itkl.processing
+
+import kotlinx.coroutines.async
+import kotlinx.coroutines.channels.Channel
+import kotlinx.coroutines.channels.consumeEach
+import kotlinx.coroutines.coroutineScope
+import kotlinx.coroutines.flow.*
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.sync.Semaphore
+import kotlinx.coroutines.sync.withPermit
+import kotlin.coroutines.coroutineContext
+
+class ParallelFlowProcessor<T,U>(
+    private val mapperFn: (T) -> U,
+    private val concurrencyLimit: Int) {
+    suspend fun process(flow: Flow<T>): Flow<U> = coroutineScope {
+        val gate = Semaphore(concurrencyLimit)
+        flow.map { item ->
+            async {
+                gate.withPermit { mapperFn(item) }
+            }
+        }
+            .map { it.await() }
+    }
+}
\ No newline at end of file
diff --git a/libraries/textprocessing/src/main/kotlin/de/itkl/textprocessing/BagOfWords.kt b/libraries/textprocessing/src/main/kotlin/de/itkl/textprocessing/BagOfWords.kt
new file mode 100644
index 0000000..8998e9e
--- /dev/null
+++ b/libraries/textprocessing/src/main/kotlin/de/itkl/textprocessing/BagOfWords.kt
@@ -0,0 +1,33 @@
+package de.itkl.textprocessing
+
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.toSet
+
+class BagOfWords(private val data: MutableSet<String> = mutableSetOf()) : Iterable<String> {
+
+    companion object {
+        suspend fun from(flow: Flow<String>): BagOfWords {
+            return BagOfWords(flow.toSet().toMutableSet())
+        }
+    }
+
+    fun add(word: String) {
+        data.add(word)
+    }
+
+    fun join(bagOfWords: BagOfWords): BagOfWords {
+        return BagOfWords(data.toMutableSet().apply { addAll(bagOfWords.data) })
+    }
+
+    override fun iterator(): Iterator<String> {
+        return iterator {
+            data.forEach { yield(it) }
+        }
+
+    }
+
+    override fun toString(): String {
+        return data.joinToString(",")
+    }
+
+}
\ No newline at end of file
diff --git a/libraries/textprocessing/src/main/kotlin/de/itkl/textprocessing/DocumentFrequency.kt b/libraries/textprocessing/src/main/kotlin/de/itkl/textprocessing/DocumentFrequency.kt
new file mode 100644
index 0000000..91bd7b5
--- /dev/null
+++ b/libraries/textprocessing/src/main/kotlin/de/itkl/textprocessing/DocumentFrequency.kt
@@ -0,0 +1,4 @@
+package de.itkl.textprocessing
+
+class DocumentFrequency {
+}
\ No newline at end of file
diff --git a/libraries/textprocessing/src/main/kotlin/de/itkl/textprocessing/Histogram.kt b/libraries/textprocessing/src/main/kotlin/de/itkl/textprocessing/Histogram.kt
index d3721c4..54c3c67 100644
--- a/libraries/textprocessing/src/main/kotlin/de/itkl/textprocessing/Histogram.kt
+++ b/libraries/textprocessing/src/main/kotlin/de/itkl/textprocessing/Histogram.kt
@@ -1,6 +1,6 @@
 package de.itkl.textprocessing
 
-import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.*
 
 class Histogram(private val histo: MutableMap<String,UInt> = mutableMapOf()) : Iterable<Pair<String, UInt>>{
 
@@ -11,6 +11,14 @@ class Histogram(private val histo: MutableMap<String,UInt> = mutableMapOf()) : I
             }
         }
 
+        suspend fun fromBagOfWords(flow: Flow<BagOfWords>): Histogram {
+            val result = Histogram()
+            flow.collect { bagOfWords ->
+                bagOfWords.forEach(result::add)
+            }
+            return result
+        }
+
         fun from(sequence: Sequence<Map<String, String>>): Histogram {
             val histo = sequence.associate { map -> map["word"]!! to map["count"]!!.toUInt() }
                 .toMutableMap()
diff --git a/libraries/textprocessing/src/main/kotlin/de/itkl/textprocessing/TextFile.kt b/libraries/textprocessing/src/main/kotlin/de/itkl/textprocessing/TextFile.kt
index 54aab4f..082b99d 100644
--- a/libraries/textprocessing/src/main/kotlin/de/itkl/textprocessing/TextFile.kt
+++ b/libraries/textprocessing/src/main/kotlin/de/itkl/textprocessing/TextFile.kt
@@ -11,6 +11,23 @@ import java.io.InputStreamReader
 
 
 class TextFile(val file: File) {
+
+    fun splitByEmptyLines(progressOp: (read: Long) -> Unit = {}): Flow<List<String>> {
+        val reader = InputStreamReader(ProgressInputStream(file.inputStream(), progressOp))
+        var list =  mutableListOf<String>()
+        return flow {
+            reader.useLines { lines ->
+                lines.forEach { line ->
+                    if(line.isEmpty()) {
+                        emit(list)
+                        list = mutableListOf()
+                    } else {
+                        list.add(line)
+                    }
+                }
+            }
+        }
+    }
     fun words(progressOp: (read: Long) -> Unit = {}): Flow<String> {
         val factory = AttributeFactory.DEFAULT_ATTRIBUTE_FACTORY
         val tokenizer = StandardTokenizer(factory)
diff --git a/libraries/textprocessing/src/main/kotlin/de/itkl/textprocessing/Tokenizer.kt b/libraries/textprocessing/src/main/kotlin/de/itkl/textprocessing/Tokenizer.kt
new file mode 100644
index 0000000..c7aa1c5
--- /dev/null
+++ b/libraries/textprocessing/src/main/kotlin/de/itkl/textprocessing/Tokenizer.kt
@@ -0,0 +1,44 @@
+package de.itkl.textprocessing
+
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.flow
+import kotlinx.coroutines.flow.onCompletion
+import org.apache.lucene.analysis.standard.StandardTokenizer
+import org.apache.lucene.analysis.tokenattributes.CharTermAttribute
+import org.apache.lucene.util.AttributeFactory
+import java.io.StringReader
+
+
+class Tokenizer : AutoCloseable{
+
+    private val tokenizer by lazy {
+        val factory = AttributeFactory.DEFAULT_ATTRIBUTE_FACTORY
+        val tokenizer = StandardTokenizer(factory)
+        tokenizer
+//        val reader = ProgressInputStream(file.inputStream(), progressOp)
+//        tokenizer.setReader(InputStreamReader(reader))
+//        tokenizer.reset()
+//        val attr = tokenizer.addAttribute(CharTermAttribute::class.java)
+//        return flow {
+//            while (kotlin.runCatching {  tokenizer.incrementToken() }.getOrElse { true } ) {
+//                emit(attr.toString())
+//            }
+//        }.onCompletion {
+//            tokenizer.close()
+//        }
+    }
+    fun tokenize(input: String): Flow<String> {
+        val reader = StringReader(input)
+        tokenizer.setReader(reader)
+        tokenizer.reset()
+        val attr = tokenizer.addAttribute(CharTermAttribute::class.java)
+        return flow {
+            while (kotlin.runCatching { tokenizer.incrementToken() }.getOrElse { true }) {
+                emit(attr.toString())
+            }
+        }.onCompletion { tokenizer.close() }
+    }
+    override fun close() {
+        tokenizer.close()
+    }
+}
\ No newline at end of file
diff --git a/libraries/tfidf/build.gradle.kts b/libraries/tfidf/build.gradle.kts
index 738ede3..de75945 100644
--- a/libraries/tfidf/build.gradle.kts
+++ b/libraries/tfidf/build.gradle.kts
@@ -4,6 +4,7 @@ plugins {
 
 dependencies {
     api(project(":libraries:textprocessing"))
+    api(project(":libraries:fileprocessing"))
     implementation("com.github.ajalt.mordant:mordant:2.2.0")
     implementation("com.github.doyaaaaaken:kotlin-csv-jvm:1.9.2")
 }
diff --git a/libraries/tfidf/src/main/kotlin/de/itkl/tfidf/Idf.kt b/libraries/tfidf/src/main/kotlin/de/itkl/tfidf/Idf.kt
new file mode 100644
index 0000000..1d358be
--- /dev/null
+++ b/libraries/tfidf/src/main/kotlin/de/itkl/tfidf/Idf.kt
@@ -0,0 +1,40 @@
+package de.itkl.tfidf
+
+import de.itkl.fileprocessing.FileProcessor
+import de.itkl.fileprocessing.Resource
+import de.itkl.textprocessing.*
+import io.github.oshai.kotlinlogging.KotlinLogging
+import kotlinx.coroutines.flow.map
+import kotlinx.coroutines.flow.reduce
+import kotlinx.coroutines.flow.take
+import java.io.File
+import java.nio.file.Path
+import kotlin.io.path.nameWithoutExtension
+
+private val Log = KotlinLogging.logger { }
+
+class Idf : FileProcessor {
+    override fun willProduce(path: Path): Path {
+        return path.parent.resolve(path.nameWithoutExtension + "-idf.csv")
+    }
+
+    override suspend fun process(resource: Resource): File {
+        Log.info { "Would produce: ${willProduce(resource.path)}" }
+        val resultFile = willProduce(resource.path).toFile()
+        val textFile = TextFile(resource.toFile())
+        val bagOfWords = textFile.splitByEmptyLines {  }
+            .take(10)
+            .map { document ->
+                val tokenizer = Tokenizer()
+                document.map { line ->
+                    val tokens = tokenizer.tokenize(line)
+                    BagOfWords.from(tokens)
+                }
+                    .reduce { acc, bagOfWords ->  acc.join(bagOfWords) }
+            }
+        val histogram = Histogram.fromBagOfWords(bagOfWords)
+        HistogramCsvStorage().save(histogram, resultFile)
+        return resultFile
+    }
+
+}
\ No newline at end of file
diff --git a/libraries/tfidf/src/main/kotlin/de/itkl/tfidf/Tf.kt b/libraries/tfidf/src/main/kotlin/de/itkl/tfidf/Tf.kt
index ab80429..38c4480 100644
--- a/libraries/tfidf/src/main/kotlin/de/itkl/tfidf/Tf.kt
+++ b/libraries/tfidf/src/main/kotlin/de/itkl/tfidf/Tf.kt
@@ -1,31 +1,9 @@
 package de.itkl.tfidf
 
+import com.github.doyaaaaaken.kotlincsv.dsl.csvReader
 import com.github.doyaaaaaken.kotlincsv.dsl.csvWriter
 import de.itkl.textprocessing.Histogram
 import io.github.oshai.kotlinlogging.KotlinLogging
 import java.io.File
-import kotlin.math.max
 
 private val Log = KotlinLogging.logger { }
-class Tf {
-    private val data: MutableMap<String, Double> = mutableMapOf()
-    fun update(histogram: Histogram): Tf {
-        val max = histogram.maxOf { (_, count) -> count }
-            .toDouble()
-        histogram.forEach { (word, count) ->
-            val tf = count.toDouble() / max
-            data[word] = tf
-        }
-        return this
-    }
-
-    suspend fun saveToCsv(file: File) {
-        csvWriter {}
-            .openAsync(file, append = false) {
-                writeRow("term", "frequency")
-                data.forEach { (t, u) ->
-                    writeRow(t, u)
-                }
-            }
-    }
-}
\ No newline at end of file
diff --git a/libraries/tfidf/src/main/kotlin/de/itkl/tfidf/TfIdf.kt b/libraries/tfidf/src/main/kotlin/de/itkl/tfidf/TfIdf.kt
index 3212c60..0e10e27 100644
--- a/libraries/tfidf/src/main/kotlin/de/itkl/tfidf/TfIdf.kt
+++ b/libraries/tfidf/src/main/kotlin/de/itkl/tfidf/TfIdf.kt
@@ -41,13 +41,6 @@ class TfIdf {
         return histogram
     }
 
-    suspend fun normalizeTf(histogram: Histogram, destination: File) {
-        Log.info { "Write tf to $destination" }
-        Tf()
-            .update(histogram)
-            .saveToCsv(destination)
-    }
-
     private fun stemmer(language: Language): SnowballStemmer {
         return when(language) {
             Language.DE -> GermanStemmer()
diff --git a/libraries/tfidf/src/main/kotlin/de/itkl/tfidf/TfIdfPipeline.kt b/libraries/tfidf/src/main/kotlin/de/itkl/tfidf/TfIdfPipeline.kt
new file mode 100644
index 0000000..38eb8be
--- /dev/null
+++ b/libraries/tfidf/src/main/kotlin/de/itkl/tfidf/TfIdfPipeline.kt
@@ -0,0 +1,10 @@
+package de.itkl.tfidf
+
+import de.itkl.fileprocessing.FileProcessingPipeline
+import de.itkl.fileprocessing.FileProcessor
+
+class TfIdfPipeline(private val language: Language) : FileProcessingPipeline() {
+    override val fileProcessor = listOf(
+        Idf()
+    )
+}
\ No newline at end of file
diff --git a/settings.gradle.kts b/settings.gradle.kts
index 3337ee0..4274775 100644
--- a/settings.gradle.kts
+++ b/settings.gradle.kts
@@ -11,4 +11,5 @@ include(
     "app",
     "libraries:tfidf",
     "libraries:textprocessing",
+    "libraries:fileprocessing",
 )