#include "../include/instruction_handler.h"
#include "../include/logger.h"

InstructionHandler::InstructionHandler() {
    this->handlers[0x0000] = handle0000;
    this->handlers[0x1000] = handle1000;
}

/**
 * Attempts to handle the Chip8 instruction by the given instruction number.
 * If the handler doesn't exist for the instruction, an error is logged, but the program resumes.
 *
 * @param instructionNumber the 16-bit value to determine the instruction
 * @param chip8 the Chip8 instance
 * @param instruction the Instruction instance
 */
void InstructionHandler::handleInstruction(unsigned short instructionNumber, Chip8& chip8, Instruction instruction) {
    if (!this->handlers.contains(instructionNumber)) {
        Logger::error("Unregistered instruction", instructionNumber);
        return;
    }

    this->handlers[instructionNumber](chip8, instruction);
}

/**
 * Handles the 0x0000 Chip-8 instruction.
 * This handles 2 other instructions:
 * - 0x00E0 which is used to clear the screen.
 * - 0x00EE which is used to return from a subroutine.
 *
 * In older interpreters, 0x0NNN was also used to jump to a machine code at NNN, but this shouldn't be implemented.
 *
 * @param chip8 The Chip8 instance
 * @param instruction The Instruction instance
 */
void InstructionHandler::handle0000(Chip8& chip8, Instruction instruction) {
    switch (instruction.kk()) {
        case 0x00E0:
            chip8.getDisplay().clear();
            break;
        case 0x00EE:
            chip8.setProgramCounter(chip8.popFromStack());
            break;
    }
}

/**
 * Handles the 0x1NNN Chip8 instruction which is used to jump to location NNN.
 * This will set the program counter to the NNN value.
 *
 * @param chip8 The Chip8 instance
 * @param instruction The Instruction instance
 */
void InstructionHandler::handle1000(Chip8& chip8, Instruction instruction) {
    chip8.setProgramCounter(instruction.nnn());
}

/**
 * Handles the 0x2NNN Chip8 instruction which is used to call a subroutine at NNN.
 * This will increments the stack pointer and puts PC on top of the stack.
 *
 * @param chip8 The Chip8 instance
 * @param instruction The Instruction instance
 */
void InstructionHandler::handle2000(Chip8& chip8, Instruction instruction) {
    chip8.pushToStack(chip8.getProgramCounter());
    chip8.setProgramCounter(instruction.nnn());
}