Magic numbers support

src/commonMain/kotlin/content/Content.kt

@@ -5,6 +5,8 @@ import kotlinx.serialization.ExperimentalSerializationApi
 import kotlinx.serialization.SerialName
 import kotlinx.serialization.Serializable
 import kotlinx.serialization.json.JsonClassDiscriminator
+import kotlin.io.encoding.Base64
+import kotlin.io.encoding.ExperimentalEncodingApi
 
 @Serializable
 @JsonClassDiscriminator("type")
@@ -33,3 +35,21 @@ interface ContentBuilder {
   }
 
 }
+
+interface DataBuilder {
+
+  var bytes: ByteArray?
+
+  fun magicNumber(): MagicNumber {
+    val bytes = requireNotNull(bytes) {
+      "bytes must be provided"
+    }
+    return requireNotNull(bytes.findMagicNumber()) {
+      "provided bytes do not contain any supported format"
+    }
+  }
+
+  @OptIn(ExperimentalEncodingApi::class)
+  fun toBase64(): String = Base64.encode(bytes!!)
+
+}

src/commonMain/kotlin/content/Document.kt

@@ -3,6 +3,7 @@ package com.xemantic.anthropic.content
 import com.xemantic.anthropic.cache.CacheControl
 import kotlinx.serialization.SerialName
 import kotlinx.serialization.Serializable
+import kotlin.io.encoding.ExperimentalEncodingApi
 
 @Serializable
 @SerialName("document")
@@ -32,10 +33,30 @@ data class Document(
 
   }
 
-  class Builder {
-    var data: ByteArray? = null
-    var mediaType: MediaType? = null
+  class Builder : DataBuilder {
+    override var bytes: ByteArray? = null
     var cacheControl: CacheControl? = null
   }
 
 }
+
+fun MagicNumber.toDocumentMediaType(): Document.MediaType? = when (this) {
+  MagicNumber.PDF -> Document.MediaType.APPLICATION_PDF
+  else -> null
+}
+
+fun Document(block: Document.Builder.() -> Unit): Document {
+  val builder = Document.Builder()
+  block(builder)
+  val magicNumber = builder.magicNumber()
+  val mediaType = requireNotNull(magicNumber.toDocumentMediaType()) {
+    "provided bytes do not contain supported Document format"
+  }
+  @OptIn(ExperimentalEncodingApi::class)
+  return Document(
+    source = Document.Source(
+      mediaType = mediaType,
+      data = builder.toBase64()
+    )
+  )
+}

src/commonMain/kotlin/content/Image.kt

@@ -3,8 +3,6 @@ package com.xemantic.anthropic.content
 import com.xemantic.anthropic.cache.CacheControl
 import kotlinx.serialization.SerialName
 import kotlinx.serialization.Serializable
-import kotlin.io.encoding.Base64
-import kotlin.io.encoding.ExperimentalEncodingApi
 
 @Serializable
 @SerialName("image")
@@ -40,32 +38,32 @@ data class Image(
 
   }
 
-  class Builder {
-    var data: ByteArray? = null
-    var mediaType: MediaType? = null
+  class Builder : DataBuilder {
+    override var bytes: ByteArray? = null
     var cacheControl: CacheControl? = null
   }
 
 }
 
-// TODO move image magic here from Claudine to further simplify the API
+fun MagicNumber.toImageMediaType(): Image.MediaType? = when (this) {
+  MagicNumber.JPEG -> Image.MediaType.IMAGE_JPEG
+  MagicNumber.PNG -> Image.MediaType.IMAGE_PNG
+  MagicNumber.GIF -> Image.MediaType.IMAGE_GIF
+  MagicNumber.WEBP -> Image.MediaType.IMAGE_WEBP
+  else -> null
+}
 
-// TODO write it functional way
 fun Image(block: Image.Builder.() -> Unit): Image {
   val builder = Image.Builder()
   block(builder)
+  val magicNumber = builder.magicNumber()
+  val mediaType = requireNotNull(magicNumber.toImageMediaType()) {
+    "provided bytes do not contain any supported Image format"
+  }
   return Image(
     source = Image.Source(
-      mediaType = requireNotNull(builder.mediaType) {
-        "Image 'mediaType' must be defined"
-      },
-      data =
-        @OptIn(ExperimentalEncodingApi::class)
-        Base64.encode(
-          requireNotNull(builder.data) {
-            "Image 'data' must be defined"
-          }
-        )
+      mediaType = mediaType,
+      data = builder.toBase64()
     )
   )
 }

src/commonMain/kotlin/content/MagicNumbers.kt

@@ -0,0 +1,44 @@
+package com.xemantic.anthropic.content
+
+@OptIn(ExperimentalUnsignedTypes::class)
+enum class MagicNumber(
+  vararg magic: UByte,
+  private val test: (
+    data: ByteArray,
+    magic: ByteArray
+  ) -> Boolean = { data, magic ->
+    data.startsWith(magic)
+  }
+) {
+
+  PDF(*"%PDF-".toUByteArray()),
+  JPEG(0xFFu, 0xD8u, 0xFFu),
+  PNG(0x89u, 0x50u, 0x4Eu, 0x47u, 0x0Du, 0x0Au, 0x1Au, 0x0Au),
+  GIF(*"GIF8".toUByteArray()),
+  WEBP(*"WEBP".toUByteArray(), test = { data, magic ->
+    (data.size >= 12) && data.slice(8..11).toByteArray().contentEquals(magic)
+  });
+
+  private val magic = magic.toUByteArray()
+
+  companion object {
+    fun find(data: ByteArray): MagicNumber? =
+      entries.find { it.test(data, it.magic.toByteArray()) }
+  }
+
+}
+
+fun ByteArray.findMagicNumber(): MagicNumber? = MagicNumber.find(this)
+
+@OptIn(ExperimentalUnsignedTypes::class)
+private fun String.toUByteArray() = toCharArray().map {
+  it.code.toUByte()
+}.toUByteArray()
+
+fun ByteArray.startsWith(
+  prefix: ByteArray
+): Boolean =
+  (size >= prefix.size)
+      && slice(prefix.indices)
+    .toByteArray()
+    .contentEquals(prefix)

src/jvmMain/kotlin/content/JvmDocument.kt

@@ -1,17 +1,15 @@
 package com.xemantic.anthropic.content
 
 import java.io.File
-import kotlin.io.encoding.Base64
 import kotlin.io.encoding.ExperimentalEncodingApi
 
-fun Document(path: String): Document = Document(File(path))
+fun Document(path: String): Document = Document {
+  path(path)
+}
+
+fun Document.Builder.path(path: String) = file(File(path))
 
-// TODO in the future this can be moved to jvmAndPosixMain
-// TODO in the future, if more types are supported, the magic number should be used to determine the media type.
 @OptIn(ExperimentalEncodingApi::class)
-fun Document(path: File): Document = Document(
-  source = Document.Source(
-    mediaType = Document.MediaType.APPLICATION_PDF,
-    data = Base64.encode(path.readBytes())
-  )
-)
+fun Document.Builder.file(file: File) {
+  bytes = file.readBytes()
+}

src/jvmMain/kotlin/content/JvmImage.kt

@@ -2,8 +2,12 @@ package com.xemantic.anthropic.content
 
 import java.io.File
 
+fun Image(path: String): Image = Image {
+  path(path)
+}
+
 fun Image.Builder.path(path: String) = file(File(path))
 
 fun Image.Builder.file(file: File) {
-  data = file.readBytes()
+  bytes = file.readBytes()
 }

src/jvmMain/kotlin/tool/computer/JvmComputer.kt

@@ -10,8 +10,7 @@ import javax.imageio.ImageIO
 object JvmComputerService : ComputerService {
 
   override fun screenshot() = Image {
-    data = takeScreenshot()
-    mediaType = Image.MediaType.IMAGE_JPEG
+    bytes = takeScreenshot()
   }
 
 }

src/jvmTest/kotlin/content/MagicNumberTest.kt

@@ -0,0 +1,28 @@
+package com.xemantic.anthropic.content
+
+import io.kotest.matchers.shouldBe
+import org.junit.jupiter.api.Test
+import java.io.File
+
+class MagicNumberTest {
+
+  @Test
+  fun shouldDetectImageMediaType() {
+    File(
+      "test-data/minimal.pdf"
+    ).readBytes().findMagicNumber() shouldBe MagicNumber.PDF
+    File(
+      "test-data/minimal.jpg"
+    ).readBytes().findMagicNumber() shouldBe MagicNumber.JPEG
+    File(
+      "test-data/minimal.png"
+    ).readBytes().findMagicNumber() shouldBe MagicNumber.PNG
+    File(
+      "test-data/minimal.gif"
+    ).readBytes().findMagicNumber() shouldBe MagicNumber.GIF
+    File(
+      "test-data/minimal.webp"
+    ).readBytes().findMagicNumber() shouldBe MagicNumber.WEBP
+  }
+
+}