#ifndef bci_interpreter_h__
#define bci_interpreter_h__

#include <stddef.h>
#include "../base.h"
#include "../method_dispatcher/method_dispatcher.h"
#include "../stack.h"

typedef struct machine_state_s
{
	// The size of the program in 16-bit words
	uint16_t program_size; 
	void * cache_function_data;

	size_t cache_size;
	uint16_t cache_offset;
	uint16_t * cache;
	size_t (* cache_block)(uint16_t * cache
				, uint16_t offset
				, size_t cache_size
				, void * cache_function_data);
	char cache_loaded;

	uint16_t program_counter;
	uint16_t status_reg;
	// Any non-zero value in this register will
	// break the program execution.
	uint16_t shutdown_reg;
	uint16_t data_reg[BCI_CORE_NUM_REG];
	bci_stack_t stack;

	size_t memory_size;
	uint16_t * memory;


	dispatch_tree_t method_dispatcher;

	// Possible Error Codes:
	// 0b01xxxxxx: memory related internal error 
	// 0b10xxxxxx: core method related internal error
	// 0b00xxxxxx: application related internal error
	//
	//
	// 0b01000000 | 1: Program offset out of bounds
	// 0b01000000 | 2: Failed to cache new data
	// 0b01000000 | 15: Memory offset out of bounds
	//
	//
	// 0b10000000 | 1: Unknown opcode
	char error;

} * machine_state_t;

machine_state_t machine_state_t_new( void * cache_function_data
				, size_t program_size
				, size_t cache_size
				, size_t memory_size
				, size_t (* cache_block)(uint16_t * cache
							, uint16_t offset
							, size_t cache_size
							, void * cache_function_data)
				, dispatch_tree_t method_dispatcher);

void machine_state_t_del(machine_state_t state);

/*
 * This function essentially executes one cycle of the machine execution.
 * It will fetch the opcode and argument, dispatch the method and execute it.
 *
 * Also this will update the cache if needed.
 *
 * Possible return codes:
 *
 * - 0bxyXXXXXX
 *   Error while executing the cycle.
 *   - 0b01XXXXXX
 *     Error in the internal memory management (i.e. program counter out
 *     of bounds)
 *     - 0b01000000 | 1: program_counter  or argument offset > program_size
 *     - 0b01000000 | 2: failed to cache new data
 *
 *   - 0b10XXXXXX
 *     Error while dispatching the method
 *     - 0b10000000 | 1: unknown opcode
 *
 * - 0b00XXXXXX
 *   XXXXXX is the return value of the bci_core_method_t method.
 * */
char machine_state_t_exec_cycle(machine_state_t state);


/*
 * Runs ``machine_state_t_exec_cycle`` until either this function
 * returns a non-zero value or a non-zero value is stored in
 * ``state->shutdown_reg``. 
 * Sets ``state->error`` to the last return value of ``machine_state_t_exec_cycle``
 * and returns it.
 * */
char machine_state_t_exec(machine_state_t state);

/*
 * Do the default updates on the machine state.
 * This will be basically increasing the program counter.
 * */
char machine_state_t_default_afterexec(machine_state_t state, uint8_t argc);

/*
 * Get the word at offset in the program memory.
 * Returns 0 on success, a non-zero value otherwise.
 *
 * It will set state->error appropiately.
 * */
char machine_state_t_get_word(machine_state_t state, uint16_t offset, uint16_t * result);

/*
 * Get the word at offset in the RAM-alike memory.
 * Works like machine_state_t_get_word.
 * */
char machine_state_t_get_mem(machine_state_t state, uint16_t offset, uint16_t * result);
char machine_state_t_set_mem(machine_state_t state, uint16_t offset, uint16_t data);
#endif