add a function to generate code for function declarations

core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/codeGen/FunctionCodegen.kt

@@ -0,0 +1,137 @@
+package org.jetbrains.kotlinx.dataframe.codeGen
+
+import com.squareup.kotlinpoet.ClassName
+import com.squareup.kotlinpoet.FunSpec
+import com.squareup.kotlinpoet.ParameterSpec
+import com.squareup.kotlinpoet.ParameterizedTypeName.Companion.parameterizedBy
+import com.squareup.kotlinpoet.TypeName
+import com.squareup.kotlinpoet.TypeSpec
+import com.squareup.kotlinpoet.asTypeName
+import com.squareup.kotlinpoet.typeNameOf
+import org.jetbrains.dataframe.impl.codeGen.CodeGenerator
+import org.jetbrains.kotlinx.dataframe.DataFrame
+import org.jetbrains.kotlinx.dataframe.api.dataFrameOf
+import org.jetbrains.kotlinx.dataframe.api.schema
+import org.jetbrains.kotlinx.dataframe.impl.DELIMITERS_REGEX
+import org.jetbrains.kotlinx.dataframe.impl.api.dataFrameOf
+import org.jetbrains.kotlinx.dataframe.impl.codeGen.toStandaloneSnippet
+import org.jetbrains.kotlinx.dataframe.impl.joinToCamelCaseString
+import org.jetbrains.kotlinx.dataframe.impl.schema.intersectSchemas
+import java.io.File
+import kotlin.reflect.KClass
+import kotlin.reflect.KFunction
+import kotlin.reflect.jvm.javaMethod
+
+public inline fun <reified T> generateCode(noinline f: () -> DataFrame<T>, sourceSet: File, name: String) {
+    return generateCode(f, name, T::class, sourceSet)
+}
+
+public inline fun <reified I1, reified T> generateCode(
+    noinline f: (I1) -> DataFrame<T>, sourceSet: File, name: String, arguments: List<I1> = emptyList()
+) {
+    return generateCode(f, name, arguments, typeNameOf<I1>(), T::class, sourceSet)
+}
+
+//public fun <I1, I2, T> generateCode(f: Function2<I1, I2, DataFrame<T>>, arguments: List<Pair<I1, I2>>) {
+//
+//}
+
+@PublishedApi
+internal fun <I1, T> generateCode(
+    f: (I1) -> DataFrame<T>,
+    name: String,
+    arguments: List<I1> = emptyList(),
+    inputName: TypeName,
+    marker: KClass<*>,
+    sourceSet: File
+) {
+    val schema = if (arguments.isNotEmpty()) {
+        arguments.map { f(it).schema() }.intersectSchemas()
+    } else {
+        MarkersExtractor.get(marker).schema
+    }
+    val packageName = (f as KFunction<*>).javaMethod?.declaringClass?.packageName!!
+    val functionName = (f as KFunction<*>).javaMethod?.name!!
+    val method = object : DefaultReadDfMethod {
+        override val additionalImports: List<String> = emptyList()
+
+        override fun toDeclaration(marker: Marker, visibility: String): String {
+            val cl = (f as KFunction<*>).javaMethod?.declaringClass?.name!!
+            val format =
+                """
+                        val f = this::class.java.classLoader.loadClass("$cl").getDeclaredMethod("$functionName", ${inputName}::class.java)
+                        f.isAccessible = true
+                        return (f.invoke(null, v) as DataFrame<*>).cast()
+                        """.trimIndent()
+
+            val typeSpec = TypeSpec.companionObjectBuilder()
+                .addFunction(
+                    FunSpec.builder("from")
+                        .addParameter(
+                            ParameterSpec.builder("v", inputName).build()
+                        )
+                        .returns(DataFrame::class.asTypeName().parameterizedBy(ClassName(packageName, marker.shortName)))
+                        .addCode(format, "v")
+                        .build()
+                ).build()
+            return typeSpec.toString()
+        }
+    }
+
+    val generator = CodeGenerator.create(useFqNames = true).generate(schema, name, true, false, true, visibility = MarkerVisibility.EXPLICIT_PUBLIC,readDfMethod = method)
+
+    println(packageName)
+    println(generator.code.toStandaloneSnippet(packageName, emptyList()))
+    val destination = sourceSet
+    val targetPackage = File(destination, packageName.replace(".", "/"))
+    val file = File(targetPackage, "${name.split(DELIMITERS_REGEX).joinToString("")}.Generated.kt")
+    file.writeText(generator.code.toStandaloneSnippet(packageName, emptyList()))
+}
+
+@PublishedApi
+internal fun <T> generateCode(f: () -> DataFrame<T>, name: String, marker: KClass<*>, sourceSet: File) {
+    // refine nullability from compile time schema
+//    val schema = MarkersExtractor.get(marker).schema
+    val schema = f().schema()
+    val packageName = (f as KFunction<*>).javaMethod?.declaringClass?.packageName!!
+    val functionName = (f as KFunction<*>).javaMethod?.name!!
+    val method = object : DefaultReadDfMethod {
+        override val additionalImports: List<String> = emptyList()
+
+        override fun toDeclaration(marker: Marker, visibility: String): String {
+            val cl = (f as KFunction<*>).javaMethod?.declaringClass?.name!!
+            val format =
+                """
+                        val f = this::class.java.classLoader.loadClass("$cl").getDeclaredMethod("$functionName")
+                        f.isAccessible = true
+                        return (f.invoke(null) as DataFrame<*>).cast()
+                        """.trimIndent()
+
+            val typeSpec = TypeSpec.companionObjectBuilder()
+                .addFunction(
+                    FunSpec.builder("sample")
+                        .returns(DataFrame::class.asTypeName().parameterizedBy(ClassName(packageName, marker.shortName)))
+                        .addCode(format, "v")
+                        .build()
+                ).build()
+            return typeSpec.toString()
+        }
+    }
+
+    val generator = CodeGenerator.create(useFqNames = true).generate(schema, name, true, false, true, visibility = MarkerVisibility.EXPLICIT_PUBLIC,readDfMethod = method)
+
+    println(packageName)
+    println(generator.code.toStandaloneSnippet(packageName, emptyList()))
+    val destination = sourceSet
+    val targetPackage = File(destination, packageName.replace(".", "/"))
+    val file = File(targetPackage, "${name.split(DELIMITERS_REGEX).joinToString("")}.Generated.kt")
+    file.writeText(generator.code.toStandaloneSnippet(packageName, emptyList()))
+}
+
+private fun ff() = dataFrameOf("a")(123)
+private fun ff1(s: String) = dataFrameOf("a")(123)
+
+internal fun main() {
+    generateCode(::ff, File("core/src/main/kotlin"), "F")
+    generateCode(::ff1, File("main"), "F", listOf("a"))
+}