#ifndef DBLTW_VM_H
#define DBLTW_VM_H


#include "joey.h"


#define OPCODE_ADD  0x01  // Add
#define OPCODE_BOC  0x02  // Branch On Condition
#define OPCODE_EXE  0x03  // Execute VM Function
#define OPCODE_JMP  0x04  // Jump to Address
#define OPCODE_HLT  0x05  // Halt Execution
#define OPCODE_POP  0x06  // Pop into Variable
#define OPCODE_PUC  0x07  // Push Constant
#define OPCODE_PUV  0x08  // Push Variable
#define OPCODE_SUB  0x09  // Subtract

#define OPCODE_LAST   OPCODE_SUB


typedef struct vmContext_ VMContextT;
typedef void (*VMFuncT)(VMContextT *context, juint16 stackCount);

typedef struct {
	jint16  value;
	jint16  allocated;
	char   *text;
} PairT;  // Signed / string pair.

typedef struct {
	juint16  value;
	jint16   allocated;
	char    *text;
} UPairT;  // Unsigned / string pair.

#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wpadded"
typedef struct {
	PairT    *stack;                // Stack for computations
	PairT    *variables;            // All variable storage
	UPairT   *labels;               // Lable jump table
	UPairT   *variableTable;        // Exported variable name-to-index table
	juint16   variablesCount;       // Number of variables in program
	juint16   labelCount;           // Number of exported labels currently loaded
	juint16   variableTableCount;   // Number of exported variables currently loaded
	juint16   stackCount;           // Maximum size stack has been
	juint16   sp;                   // Stack pointer
	juint16   pc;                   // Program counter
	byte     *memory;               // Program byte stream
	juint16   programSize;          // Number of bytes in program byte stream
	VMFuncT  *functions;            // Native function pointers
	juint16   functionCount;        // Number of native functions attached
	juint16   headerBytes;          // Header bytes (used for PC calculations)
} PrivateT;
#pragma GCC diagnostic pop

typedef struct vmContext_ {
	PrivateT  private;
	PairT    *working;         // Working space for operands
} VMContextT;


bool vmAddFunction(VMContextT *context, VMFuncT function);
bool vmCreate(VMContextT *context);
bool vmDestroy(VMContextT *context);
bool vmGetPCIndex(VMContextT *context, char *label, juint16 *pc);
bool vmGetVariable(VMContextT *context, char *name, PairT *item);
bool vmGetVariableIndex(VMContextT *context, char *name, juint16 *index);
bool vmIsItemNumber(PairT *item);
bool vmLoad(VMContextT *context, char *filename);
bool vmPop(VMContextT *context, PairT *item);
bool vmPush(VMContextT *context, PairT *item);
void vmSetItem(PairT *item, char *text, jint16 *value);
bool vmSetPC(VMContextT *context, char *label);
bool vmSetPCByIndex(VMContextT *context, juint16 index);
bool vmSetVariable(VMContextT *context, char *name, PairT *item);
bool vmSetVariableByIndex(VMContextT *context, jint16 index, PairT *item);
bool vmStep(VMContextT *context);
bool vmRun(VMContextT *context);


#endif