package org.javanext.apt;

import javax.tools.Diagnostic;

import javax.annotation.processing.Messager;
import javax.annotation.processing.ProcessingEnvironment;
import javax.lang.model.element.Element;
import javax.lang.model.element.TypeElement;
import javax.lang.model.type.TypeKind;

import org.javanext.Getter;

import com.sun.source.tree.MethodTree;
import com.sun.source.util.Trees;
import com.sun.tools.javac.code.Symbol;
import com.sun.tools.javac.code.Type;
import com.sun.tools.javac.processing.JavacProcessingEnvironment;
import com.sun.tools.javac.tree.JCTree;
import com.sun.tools.javac.tree.TreeMaker;
import com.sun.tools.javac.tree.JCTree.JCAnnotation;
import com.sun.tools.javac.tree.JCTree.JCBlock;
import com.sun.tools.javac.tree.JCTree.JCClassDecl;
import com.sun.tools.javac.tree.JCTree.JCExpression;
import com.sun.tools.javac.tree.JCTree.JCStatement;
import com.sun.tools.javac.tree.JCTree.JCTypeParameter;
import com.sun.tools.javac.tree.JCTree.JCVariableDecl;
import com.sun.tools.javac.util.List;
import com.sun.tools.javac.util.Name;

public class HandleGetter {
	private final JavacProcessingEnvironment env;
	private final Trees trees;
	private final Messager messager;

	public HandleGetter(ProcessingEnvironment env) {
		this.messager = env.getMessager();

		if ( env instanceof JavacProcessingEnvironment ) this.env = (JavacProcessingEnvironment)env;
		else {
			this.env = null;
			this.trees = null;
			messager.printMessage(Diagnostic.Kind.ERROR, "I only work with JavacProcessingEnvironment. Perhaps you aren't compiling with javac?");
			return;
		}

		this.trees = Trees.instance(env);
	}

	public void handle(Element element, Getter getter) {
		if ( !element.getKind().isField() ) {
			messager.printMessage(Diagnostic.Kind.ERROR, "@Getter is only supported on a field.");
			return;
		}

		TypeElement classElement = (TypeElement)element.getEnclosingElement();
		JCClassDecl javacClassTree = (JCClassDecl)trees.getTree(classElement);

		Name.Table nameTable = Name.Table.instance(env.getContext());
		TreeMaker treeMaker = TreeMaker.instance(env.getContext());

		MethodTree getterMethod = createGetter(element, treeMaker, nameTable);
		javacClassTree.defs = javacClassTree.defs.append((JCTree)getterMethod);
	}

	private MethodTree createGetter(Element field, TreeMaker treeMaker, Name.Table nameTable) {
		JCStatement returnStatement = treeMaker.Return(treeMaker.Ident((Symbol)field));
		JCBlock methodBody = treeMaker.Block(0, com.sun.tools.javac.util.List.of(returnStatement));
		Name methodName = Name.fromString(nameTable, toGetterName(field));
		JCExpression methodType = treeMaker.Type((Type)field.asType());

		List<JCTypeParameter> returnTypeGenerics = List.nil();
		List<JCVariableDecl> parameters = List.nil();
		List<JCExpression> throwsClauses = List.nil();

		MethodTree method = treeMaker.MethodDef(treeMaker.Modifiers(1L, List.<JCAnnotation>nil()), methodName, methodType,
				returnTypeGenerics, parameters, throwsClauses, methodBody, null);
		return method;
	}

	private static String toGetterName(Element element) {
		CharSequence fieldName = element.getSimpleName();
		if ( fieldName.length() == 0 ) return "get";

		final String prefix, suffix;

		if ( element.asType().getKind() == TypeKind.BOOLEAN || "java.lang.Boolean".equals(element.asType().toString()) ) prefix = "is";
		else prefix = "get";

		char first = fieldName.charAt(0);
		if ( Character.isLowerCase(first) )
			suffix = String.format("%s%s", Character.toTitleCase(first), fieldName.subSequence(1, fieldName.length()));
		else suffix = fieldName.toString();
		return String.format("%s%s", prefix, suffix);
	}
}