#include <limits.h>
#include <stdlib.h>
#include <time.h>

#include "nes.h"
#include "render.h"
#include "input.h"


/*
void e6502_print_registers(const e6502_Registers* regs,
                           FILE* file) {
    fprintf(file, "PC: $%04x\n", regs->PC);
    fprintf(file, " S:   $%02x\n", regs->S);
    fprintf(file, " A:   $%02x\n", regs->A);
    fprintf(file, " X:   $%02x\n", regs->X);
    fprintf(file, " Y:   $%02x\n", regs->Y);
    fprintf(file, " P:   $%02x\n", regs->P);
}

void e6502_dump_mem(e6502_Core* core, uint16_t addr,
                    int len, FILE* file) {
    for ( ; len > 0; --len, ++addr) {
        fprintf(file, "$%04x: %02x\n",
                      addr, e6502_r8(core, addr));
    }
}

void e6502_dump_stack(e6502_Core* core, FILE* file) {
    int len = 0x100U + 2U - core->registers.S;
    uint16_t addr = e6502_Memory_Stack + 0xFFU;
    for ( ; len > 0; --len, --addr) {
        fprintf(file, "$%03x: %02x\n",
                      addr, e6502_r8(core, addr));
    }
}
*/

#define NS_PER_S    (1000U * 1000U * 1000U)
/*
static int t_diff_ns(const struct timespec* b,
                     const struct timespec* a) {
    int sec = (b->tv_sec - a->tv_sec);
    int nsec = (b->tv_nsec - a->tv_nsec);
    return ((sec * NS_PER_S) + nsec);
}
*/
static void t_add_ns(struct timespec* s,
                     const struct timespec* a,
                     int b) {
    int nsec = a->tv_nsec + b;
    s->tv_sec = a->tv_sec + (nsec / NS_PER_S);
    s->tv_nsec = nsec % NS_PER_S;
}


extern nes_Renderer sdl_renderer;

extern nes_Input_Reader sdl_input;


static nes sys = {0};


int main(int argc, char* argv[]) {
    int status = 0;

    int n_loops = (argc > 1) ? atoi(argv[1]) : 0;
    if (n_loops <= 0) n_loops = INT_MAX;

    status = nes_cart_init_file(&sys.cart, stdin);

    nes_Renderer* rend = &sdl_renderer;
    if (status == 0) {
        status = nes_render_init(rend);
    }

    nes_Input_Reader* input = &sdl_input;
    if (status == 0) {
        status = nes_input_init(input);
    }

    if (status == 0) {
        status = nes_init(&sys);
    }

    if (status == 0) {
        nes_reset(&sys);

        nes_render(rend, &sys.ppu);

        struct timespec t_target = {0};
        clock_gettime(CLOCK_MONOTONIC, &t_target);
        uint64_t cycle_last_frame = 0;

        uint64_t total_cycles = 0;
//        int last_frame_rendered = -1;
        for (int i = 0; i < n_loops && status == 0; ++i) {
            int run = 0;
            nes_ppu_Result result = nes_run(&sys, 1U, &run);
            total_cycles += run;
/*
            float us_run = (    run * 1000. * 1000. *
                                nes_clock_master_den) /
                           nes_clock_master_num;
            fprintf(stdout, "Ran %f us, %d master cycles (%s)\n",
                            us_run, run,
                            status == 0 ? "OK" : "Halted");
*/
            if (    result == ppu_Result_Ready ||
                    result == ppu_Result_VBlank_Off) {
                status = nes_render(rend, &sys.ppu);

                if (status > 0) {
//                    last_frame_rendered = sys.ppu.frame;

                    // Sleep to catch up to master clock
                    uint64_t elapsed_cycles = total_cycles -
                                              cycle_last_frame;
                    int elapsed_ns = (  elapsed_cycles *
                                        nes_clock_master_den *
                                        NS_PER_S ) /
                                     nes_clock_master_num;

                    t_add_ns(&t_target, &t_target, elapsed_ns);

                    clock_nanosleep(CLOCK_MONOTONIC, TIMER_ABSTIME,
                                    &t_target, NULL);

                    cycle_last_frame = total_cycles;

                    // Update button states every rendered frame
                    status = nes_input_update(input, &sys.input);
                }
            } else if (result == ppu_Result_Halt) {
                status = -1;
            }
        }

        float ms_run = (    total_cycles * 1000. *
                            nes_clock_master_den) /
                       nes_clock_master_num;
        fprintf(stdout, "Ran %f ms, %lu master cycles (%s)\n",
                        ms_run, total_cycles,
                        status == 0 ? "OK" : "Halted");
/*
        e6502_print_registers(&sys.cpu.registers, stdout);
        e6502_dump_stack(&sys.cpu, stdout);
*/
    }

    return status;
}