using System.Reflection.Emit;

// Z# Code Item.
// An item stores the attributes of an operand during code generation.
public class Item
{
    public enum Kind { Const, Arg, Local, Static, Field, Stack, Elem, Meth, Cond }

    public Kind kind;             // Const, Local, Static, Stack, Field, Elem, Method, Cond
    public Struct type;           // item type
    public int val;               // Const: value
    public int adr;               // Arg, Local: offset
    public int relop;             // Cond: token code of relational operator
    public Symbol sym;            // Field, Meth: node from symbol table
    public Label tLabel, fLabel;  // Cond: true jumps, false jumps

    public Item (Symbol sym)
    {
        type = sym.type;
        this.sym = sym;
        switch (sym.kind) {
            case Symbol.Kind.Const:
                kind = Kind.Const;
                val = sym.val;
                break;
            case Symbol.Kind.Arg:
                kind = Kind.Arg;
                adr = sym.adr;
                break;
            case Symbol.Kind.Local:
                kind = Kind.Local;
                adr = sym.adr;
                break;
            case Symbol.Kind.Global:
                kind = Kind.Static;
                break;
            case Symbol.Kind.Field:
                kind = Kind.Field;
                break;
            case Symbol.Kind.Meth:
                kind = Kind.Meth;
                break;
            default:
                Parser.Error("Cannot create code item for this kind of symbol table object");
                break;
        }
    }

    // special constructor for Const Items
    public Item (int val)
    {
        kind = Kind.Const;
        type = Tab.intType;
        this.val = val;
    }

    // special constructor for Cond Items
    public Item (int relop, Struct type)
    {
        this.kind = Kind.Cond;
        this.type = type;
        this.relop = relop;
        tLabel = Code.il.DefineLabel();
        fLabel = Code.il.DefineLabel();
    }

    // special constructor for Stack Items
    public Item (Struct type)
    {
        kind = Kind.Stack;
        this.type = type;
    }
}