package tool;

import parser.Lexer;
import parser.Parser;
import trees.ExpressionTree;

import java.io.IOException;
import java.io.InputStream;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class CodeGen {
	/** Pull char from where? */
	InputStream in;
	/** Variable to local-variable number map used by code generator */
	public Map variables = new HashMap();
	/** Code generation output */
	public StringBuffer out = new StringBuffer();
	int maxStackDepth = 0;
	int maxLocals = 0;

	public static void main(String[] args) throws IOException {
		CodeGen generator = new CodeGen(System.in);
		generator.compile();
		generator.emit();
	}

	public void emit() {
		System.out.println(header);
		System.out.println(".limit stack "+maxStackDepth); // how much stack space do we need?
		System.out.println(".limit locals "+maxLocals); // how many locals do we need?
		String code = out.toString();
		System.out.println(code);
		System.out.println(footer);
	}

	public CodeGen(InputStream in) {
		this.in = in;
	}

	/** Compiles code to a buffer (minus header/footer); sets this.out */
	public void compile() throws IOException {
		Map variables = new HashMap();
		Lexer lex = new Lexer(in);
		Parser parser = new Parser(lex);
		List statements = parser.prog();
		computeStackSize(statements);
		for (int i = 0; i < statements.size(); i++) {
			ExpressionTree t = (ExpressionTree) statements.get(i);
			t.gen(this);
		}
	}

	private void computeStackSize(List statements) {
		for (int i = 0; i < statements.size(); i++) {
			ExpressionTree t = (ExpressionTree) statements.get(i);
			int height = t.height();
			maxStackDepth = Math.max(maxStackDepth, height);
			int vars = t.countVarNodes();
			maxLocals = Math.max(maxLocals, vars);
		}
		maxLocals++; // make room for args parameter to main()
	}

	// B Y T E C O D E  S T U F F

	/** Class definition for Calc in bytecodes.  Templates are
	 *  a better approach here, but for simplicity, I use strings.
	 */
	public static final String header =
		"; public class Calc extends Object { ...}\n" +
		".class public Calc\n" +
		".super java/lang/Object\n" +
		"\n" +
		"; public Calc() { super(); } // calls java.lang.Object()\n" +
		".method public <init>()V\n" +
		"  aload_0\n" +
		"  invokenonvirtual java/lang/Object/<init>()V\n" +
		"  return\n" +
		".end method\n" +
		"\n" +
		"; main(): Expr.g will generate bytecode in this method\n" +
		".method public static main([Ljava/lang/String;)V";

	public static final String footer =
			"  return\n" +
			".end method";
}