package fi.hu.cs.titokone;

import fi.hu.cs.ttk91.TTK91Cpu;

/** This data class contains all the register information. The registers
    are accessed via index numbers which are defined in the TTK91CPU 
    interface. */
public class Registers { 
    /** This field contains the register values. 0..7 are general-purpose 
    registers, 8..12 are CU registers. */
    private int[] registerValues = new int [13];
	
    /** Returns the value of a register. The index numbers
	are available from the TTK91CPU interface.
	@param registerId Identifying number of the register.
	@return Value stored in the register.  */
    public int getRegister(int registerId) {
        int index = getIndex (registerId);
        if (index != -1) 
            return registerValues[index];
        else
            throw new IllegalArgumentException(new Message("Unknown registerId: {0}", 
							   "" + registerId).toString());
    }

    /** Returns the value of a register. 
	@param registerName The name of the register.
	@return Value stored in the register.  */
    public int getRegister(String registerName) {
        int index = getIndex (registerName);
        if (index != -1) 
            return registerValues[index];
        else
            throw new IllegalArgumentException(new Message("Unknown registerName: {0}", 
							   "" + registerName).toString());
    }

    /** Sets a new value to a register.
	@param registerId The identifying number of the register.
	@param value New value to set.  */
    public void setRegister(int registerId, int value) {
        int index = getIndex (registerId);
        if (index != -1) 
            registerValues[index] = value;
        else
            throw new IllegalArgumentException(new Message("Unknown registerId: {0}", 
							   "" + registerId).toString());
    }
    
    /** Sets a new value to a register.
	@param registerName The name of the register.
	@param value New value to set.  */
    public void setRegister(String registerName, int value) {
        int index = getIndex (registerName);
        if (index != -1) 
            registerValues[index] = value;
        else
            throw new IllegalArgumentException(new Message("Unknown registerName: {0}", 
							   "" + registerName).toString());
    }
    
    /** Converts TTK91Cpu register to the corresponding index to registerValues array.
        @param TTK91Cpu_index Register index in TTK91Cpu notation
        @return Index to registerValues array. Returns -1 if register 
        does not exists in TTK91Cpu.
    */
    private int getIndex (int TTK91Cpu_index) {
        switch (TTK91Cpu_index) {
            case TTK91Cpu.REG_R0 : return 0;
            case TTK91Cpu.REG_R1 : return 1;
            case TTK91Cpu.REG_R2 : return 2;
            case TTK91Cpu.REG_R3 : return 3;
            case TTK91Cpu.REG_R4 : return 4;
            case TTK91Cpu.REG_R5 : return 5;
            case TTK91Cpu.REG_R6 : return 6;
            case TTK91Cpu.REG_R7 : return 7;
            case TTK91Cpu.CU_TR : return 8;
            case TTK91Cpu.CU_IR : return 9;
            case TTK91Cpu.CU_PC : return 10;
            case TTK91Cpu.CU_PC_CURRENT : return 11;
            case TTK91Cpu.CU_SR : return 12;
            default : return -1;
        }
    }
    
    /** Converts given String to the corresponding index to registerValues array.
        @param registerName The name of the register.
        @return Index to registerValues array. Returns -1 if register 
        does not exists.
    */
    private int getIndex (String registerName) {
        if (registerName == null) return -1;
        String str = registerName.toUpperCase().trim();
        if (str.equals ("R0")) return 0;
        if (str.equals ("R1")) return 1;
        if (str.equals ("R2")) return 2;
        if (str.equals ("R3")) return 3;
        if (str.equals ("R4")) return 4;
        if (str.equals ("R5")) return 5;
        if (str.equals ("R6")) return 6;
        if (str.equals ("R7")) return 7;
        if (str.equals ("SP")) return 6;
        if (str.equals ("FP")) return 7;
        if (str.equals ("TR")) return 8;
        if (str.equals ("IR")) return 9;
        if (str.equals ("PC")) return 10;
        if (str.equals ("PC_CURRENT")) return 11;
        if (str.equals ("SR")) return 12;
        return -1;
    }
}