#include <errno.h>
#include <stdio.h>

#include <time.h>
#include <unistd.h>
#include <dirent.h>

#include <sys/mman.h>
#include <sys/stat.h>

#include "action.h"
#include "cart.h"
#include "nese.h"
#include "overlay.h"
#include "port.h"
#include "save.h"
#include "draw.h"
#include "cartinfo.h"
#include "menu.h"

#define NESE_DEBUG "Port"
#include "log.h"

//#define NESE_TURBO


/*
 * OS-specific file operations
 * Memory mapping specifically needs to be ported for each OS
 */

void* nese_map_file(FILE* file, int size, Filemap_Mode map_mode) {
    int prot = (    Filemap_Mode_Write == map_mode ?
                    PROT_WRITE : PROT_READ);
    int flags = (   Filemap_Mode_Write == map_mode ?
                    MAP_SHARED : MAP_PRIVATE);
    void* mem = mmap(NULL, size, prot, flags, fileno(file), 0);
    if ((void*)-1 == mem) {
        fprintf(stderr, "Failed to map file: %d\n", errno);
        mem = NULL;
    }
    return mem;
}

void nese_unmap_file(void* mem, int size) {
    munmap(mem, size);
}

int nese_mkdir(const char* dir) {
    return mkdir(dir, 0777);
}

int nese_file_size(FILE* file) {
    int size = -1;
    if (0 == fseek(file, 0, SEEK_END)) {
        size = ftell(file);
    }
    return size;
}


/*
 * Platform-specific allocation
 * GPU and CPU refer to emulator memory spaces
 * Note: GPU (and possibly CPU) regions may need
 * to be placed into internal ram for performance
 */

void* nese_alloc_gpu(int size) {
    return calloc(1, size);
}

void* nese_alloc_cpu(int size) {
    return calloc(1, size);
}

void* nese_alloc(int size) {
    return calloc(1, size);
}


/*
 * Platform-specific features and controls
 */

#define PLAT_FILENAME_SIZE  (1024U)

typedef enum {
    Flag_Turbo = 0b1,
} Platform_Flags;

typedef struct {
    nes* sys;
    Cart_Info cart;
    int64_t t_target;
    Render_Info renderer;
    Overlay overlay;
    int fps_msg_id;
    Platform_Flags flags;
    char filename[PLAT_FILENAME_SIZE];
} platform_data;


/* Directories */

static int cmp_files(const void* _a, const void* _b) {
    const char* a = *(const char**)_a;
    const char* b = *(const char**)_b;

    int diff = 0;
    for (char ca = 1, cb = 1; ca && cb && 0 == diff; ++a, ++b) {
        // Cut extensions; replace underscore with space
        ca = (*a == '_' ? ' ' : (*a == '.' ? '\0' : *a));
        cb = (*b == '_' ? ' ' : (*b == '.' ? '\0' : *b));
        diff = (ca - cb);
    }

    return diff;
}

static int count_files(DIR* dir) {
    int count = 0;
    struct dirent* de = NULL;
    while (NULL != (de = readdir(dir))) {
        if ('.' != de->d_name[0]) ++count;
    }
    rewinddir(dir);
    return count;
}

static void make_file_list(DIR* dir, File_List* files) {
    files->count = count_files(dir);
    files->files = calloc(files->count, sizeof(char*));
    struct dirent* de = NULL;
    int i_file = 0;
    while (NULL != (de = readdir(dir))) {
        if ('.' != de->d_name[0]) {
            files->files[i_file] = strdup(de->d_name);
            ++i_file;
        }
    }
    qsort(files->files, files->count, sizeof(char*), cmp_files);
}

static void free_file_list(File_List* files) {
    for (int i = 0; i < files->count; ++i) {
        free(files->files[i]);
    }
    free(files->files);
}

static int find_file(File_List* files, const char* filename) {
    int i = (files->count - 1);
    for ( ; i >= 0 &&
            (0 != strcmp(files->files[i], filename)); --i);
    return i;
}


/* Input */

static const int sdl_action_keycodes[Action_Max] = {
    [Action_Menu]  = SDLK_ESCAPE,
    [Action_Reset] = SDLK_BACKSPACE,
    [Action_Load]  = SDLK_F2,
    [Action_Save]  = SDLK_F1,
    [Action_FPS]   = SDLK_f,
    [Action_Turbo] = SDLK_t,
};

static const int sdl_button_keycodes[2 * nes_controller_num_buttons] = {
    SDLK_a,
    SDLK_s,
    SDLK_q,
    SDLK_w,
    SDLK_UP,
    SDLK_DOWN,
    SDLK_LEFT,
    SDLK_RIGHT,

    SDLK_LCTRL,
    SDLK_LALT,
    SDLK_TAB,
    SDLK_RETURN,
    SDLK_KP_8,
    SDLK_KP_2,
    SDLK_KP_4,
    SDLK_KP_6,
};

static int keycode_index(int keycode, const int* codes, int n_codes) {
    int index = n_codes - 1;
    for ( ; index >= 0 && keycode != codes[index]; --index);
    return index;
}

static nese_Action process_events(nes* sys) {
    nese_Action action = Action_OK;
    nes_Input* input = &sys->core.memory.input;

    SDL_Event event = {0};
    while (Action_OK == action && 0 != SDL_PollEvent(&event)) {
        if (SDL_QUIT == event.type) {
            action = Action_Quit;

        } else if ( (   SDL_KEYDOWN == event.type ||
                        SDL_KEYUP == event.type) &&
                    0 == event.key.repeat
                ) {
            int index = keycode_index(
                    event.key.keysym.sym,
                    sdl_button_keycodes,
                    2 * nes_controller_num_buttons
                );
            if (index >= 0) {
                index %= nes_controller_num_buttons;
                uint8_t mask = (1 << index);
                if (SDL_KEYDOWN == event.type) {
                    input->gamepads[0].buttons |= mask;
                } else {
                    input->gamepads[0].buttons &= ~mask;
                }

            } else if (SDL_KEYDOWN == event.type) {
                index = keycode_index(
                        event.key.keysym.sym,
                        sdl_action_keycodes, Action_Max
                    );
                if (index >= 0) action = index;
            }
        }
        // TODO: Controller inputs
    }

    return action;
}


/*
 * Time / Video - Should be maximally reusable across platforms
 */

int nese_frame_start(void* plat_data, uint8_t background) {
    return render_frame_start(  &((platform_data*)plat_data)->renderer,
                                background);
}

int nese_line_ready(void* plat_data, uint8_t* buffer, int line) {
/*
    platform_data* plat = (platform_data*)plat_data;

    SDL_Rect rect = {
        .x = 0,
        .y = line,
        .w = nes_ppu_render_w,
        .h = 1,
    };

    SDL_BlitSurface(plat->scanline, NULL, plat->target, &rect);
*/
    return 0;
}


#define NS_PER_S      (1000L * 1000L * 1000L)
#define FRAME_TIME_NS (16639267L)

uint64_t time_now(void) {
  struct timespec ts_now = {0};
  clock_gettime(CLOCK_REALTIME, &ts_now);
  return (ts_now.tv_sec * NS_PER_S) + ts_now.tv_nsec;
}

int64_t time_sleep_until(int64_t t_target) {
  int64_t t_now = time_now();
  int64_t t_diff = (t_target - t_now) / 1000;
  if (t_diff > 0) {
    usleep(t_diff);
  }
  return t_diff * 1000;
}

static nese_Action game_menu(platform_data* plat);

int nese_frame_ready(void* plat_data) {
    platform_data* plat = (platform_data*)plat_data;
/*
    uint8_t* ptr = &plat->sys->core.memory.ppu.vram[0x3C0];
    for (int y = 0; y < 16; y += 2) {
        printf("%04lX", 0x2000 + ptr - plat->sys->core.memory.ppu.vram);
        for (int x = 0; x < 8; ++x) {
            printf(" %d %d", (*ptr >> 0) & 3, (*ptr >> 2) & 3);
            ++ptr;
        }
        ptr -= 8;
        fputs("\n    ", stdout);
        for (int x = 0; x < 8; ++x) {
            printf(" %d %d", (*ptr >> 4) & 3, (*ptr >> 6) & 3);
            ++ptr;
        }
        putc('\n', stdout);
    }
    putc('\n', stdout);
*/
    int status = render_frame(&plat->renderer);

    if (0 == status) {
        overlay_render(&plat->overlay,
                       nes_ppu_render_w, nes_ppu_render_h,
                       &plat->renderer.view, plat->renderer.renderer);
    }

    if (0 == status) {
        status = render_frame_end(&plat->renderer);
    }


    // TODO: Check status first?

    nese_Action action = process_events(plat->sys);
    switch (action) {
    case Action_Quit:
        // TODO: Save SRAM
        status = -1;
        break;

    case Action_Save:
        status = save_state(plat->sys, plat->cart.filename);
        break;

    case Action_Load:
        status = load_state(plat->sys, plat->cart.filename);
        break;

    case Action_FPS:
        if (plat->fps_msg_id <= 0) {
            plat->fps_msg_id = overlay_add_message(&plat->overlay, "", 0);
        } else {
            overlay_clear_message(&plat->overlay, plat->fps_msg_id);
            plat->fps_msg_id = 0;
        }
        break;

    case Action_Turbo:
        plat->flags ^= Flag_Turbo;
        break;

    case Action_Menu:
        action = game_menu(plat);
        if (Action_Reset == action) {
            nes_reset(plat->sys);
        } else if (Action_Save == action) {
            status = save_state(plat->sys, plat->cart.filename);
        } else if (Action_Load == action) {
            status = load_state(plat->sys, plat->cart.filename);
        } else if (Action_Quit == action || NULL == plat->sys->cart_header) {
            status = -1;
        }
        // TODO: Other Actions?
        break;

    default:
    }

    // TODO: Perform more actions?

    if (0 == status) {
        plat->t_target += FRAME_TIME_NS;
        int64_t slept_ns = 0;
        if (plat->flags & Flag_Turbo) {
            int64_t now = time_now();
            slept_ns = plat->t_target - now;
            plat->t_target = now;
        } else {
            slept_ns = time_sleep_until(plat->t_target);
            if (slept_ns <= -FRAME_TIME_NS) {
                // We're way out of sync.
                plat->t_target = time_now();
                printf("Out of sync: %d\n", (int)slept_ns);
            }
        }

        static int frame = 0;
        static int64_t slept_total = 0;
        slept_total += slept_ns;
        if (60 == ++frame) {
            if (plat->fps_msg_id > 0) {
                int64_t game_elapsed = frame * FRAME_TIME_NS;
                int64_t cpu_elapsed = game_elapsed - slept_total;
                float fps = (double)(NS_PER_S * frame) / cpu_elapsed;

                char message[32];
                snprintf(message, sizeof(message), "%.1f fps", fps);
                overlay_update_message(&plat->overlay, plat->fps_msg_id, message);
            }

            slept_total = 0;
            frame = 0;
        }

    }

    return status;
}


/* Drawing */

void nese_draw_begin(void* plat_data) {
    platform_data* plat = (platform_data*)plat_data;
    draw_begin(&plat->renderer, NULL != plat->sys->cart_header);
}

void nese_draw_text(void* plat_data, const char* str, int x, int y, uint32_t c) {
    draw_text(&((platform_data*)plat_data)->renderer,
              &((platform_data*)plat_data)->overlay.font,
              str, x, y, c);
}

void nese_text_size(void* plat_data, const char* str, int* w, int* h) {
    overlay_font_measure(&((platform_data*)plat_data)->overlay.font, str, w, h);
}

void nese_draw_finish(void* plat_data) {
    render_frame_end(&((platform_data*)plat_data)->renderer);
}


/* Audio */

int nese_get_audio_frequency(void*) {
    return 44100;
}

// TODO: Audio functions


/* Menus */

nese_Action nese_update_input(void* plat_data, nes_Input* input) {
    time_sleep_until(time_now() + (NS_PER_S / 60));
    platform_data* plat = (platform_data*)plat_data;
    nese_Action action = process_events(plat->sys);
    if (NULL != input) *input = plat->sys->core.memory.input;
    return action;
}

static nese_Action run_rom_menu(platform_data* plat, Menu_State* state,
                                char* filename, int sz_filename) {
    nese_Action action = Action_Cancel;

    DIR* dir = opendir("rom");

    if (NULL == dir) {
        modal_popup(plat, "No ROMS found!\nPress any key to exit",
                    color_error);

    } else {
        File_List files = {0};
        make_file_list(dir, &files);
        closedir(dir);

        Menu_State menu = {0};
        if (NULL != state) menu = *state;

        // Add 4 to skip past "rom/"
        if (strlen(filename) > 4) {
            int current = find_file(&files, filename + 4);
            if (current >= 0) menu.cursor = current;
        }

        action = run_menu(plat, &menu, &files, 20);

        if (Action_OK == action) {
            if (    menu.cursor >= 0 &&
                    menu.cursor < files.count) {
                snprintf(filename, sz_filename - 1,
                         "%s/%s", "rom", files.files[menu.cursor]);
            } else {
                action = Action_Cancel;
            }
        }

        free_file_list(&files);

        if (NULL != state) *state = menu;
    }

    return action;
}

static nese_Action nese_load_cart(platform_data* plat, const char* filename) {
    nese_Action action = Action_OK;
    unload_cart(&plat->cart);
    plat->sys->cart_header = NULL;
    int status = load_cart(&plat->cart, filename, plat->sys);
    if (0 != status) {
        char message[1024];
        snprintf(message, sizeof(message), "Failed to load\n%s", filename);
        action = modal_popup(plat, message, color_error);
        if (Action_Quit != action) action = Action_Cancel;
    }
    return action;
}

static nese_Action select_rom(platform_data* plat, char* file, int sz_file) {
    nese_Action action = Action_OK;
    Menu_State menu = {0};

    // TODO: Save SRAM

    while (Action_OK == action || NULL == plat->sys->cart_header) {
        action = run_rom_menu(plat, &menu, file, sz_file);
        if (Action_OK == action) {
            plat->sys->cart_header = NULL;
            action = nese_load_cart(plat, file);
            if (Action_OK == action) break;
            // Failure - Now no ROM is currently loaded
            render_clear(&plat->renderer);
            file[0] = '\0';
            if (Action_Quit != action) action = Action_OK;
        } else if ( (   Action_Cancel == action &&
                        NULL == plat->sys->cart_header) ||
                    Action_Quit == action) {
            // If no cart is loaded, or the user tried to quit, just leave
            break;
        }
    }

    return action;
}

static nese_Action run_game_menu(platform_data* plat, Menu_State* state) {
    static char* items[] = {
        "Resume",
        "Save",
        "Restore",
        "Reset",
        "Select ROM",
        "Exit",
    };
    static const nese_Action choices[] = {
        Action_Cancel,
        Action_Save,
        Action_Load,
        Action_Reset,
        Action_Menu,
        Action_Quit,
    };
    static const File_List options = {
        .files = items,
        .count = (sizeof(items) / sizeof(*items)),
    };

    Menu_State menu = {0};
    if (NULL != state) menu = *state;

    nese_Action action = run_menu(plat, &menu, &options, 100);
    if (Action_Menu == action) {
        action = Action_Cancel;
    } else if (Action_OK == action) {
        if (    menu.cursor >= 0 &&
                menu.cursor < (sizeof(choices) / sizeof(*choices))) {
            action = choices[menu.cursor];
        }
    }

    if (NULL != state) *state = menu;

    return action;
}

static nese_Action game_menu(platform_data* plat) {
    nese_Action action = Action_OK;
    Menu_State menu = {0};

    while (Action_OK == action) {
        action = run_game_menu(plat, &menu);

        if (Action_Menu == action) {
            // Select ROM
            action = select_rom(plat, plat->filename, PLAT_FILENAME_SIZE);
            if (Action_OK == action) {
                // New ROM selected - Exit loop and reset
                action = Action_Reset;

            } else if (Action_Cancel == action) {
                // No ROM selected - Keep the menu running
                action = Action_OK;
            }

            if (NULL == plat->sys->cart_header) {
                // A failed ROM load means we shouldn't return to the game menu
                action = Action_Quit;
            }
        }
    }

    return action;
}


/* Platform Data */

static int plat_init(platform_data* plat) {
    int status = render_info_init(&plat->renderer, plat->sys);

    if (0 == status) {
        status = overlay_init(&plat->overlay, plat->renderer.renderer);
    }

    if (0 == status) {
        plat->t_target = time_now();
    }

    return status;
}

static void plat_done(platform_data* plat) {
    render_info_done(&plat->renderer);
    overlay_done(&plat->overlay);
    SDL_Quit();
}


// This is too big for the stack.
static nes sys = {0};


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

    // This should be tiny enough to keep on the stack.
    platform_data plat = {
        .sys = &sys,
    };

    if (0 == status) {
        status = plat_init(&plat);
    }

    if (0 == status) {
        if (1 < argc) {
            strncpy(plat.filename, argv[1], PLAT_FILENAME_SIZE - 1);
            plat.filename[PLAT_FILENAME_SIZE - 1] = '\0';
            nese_Action action = nese_load_cart(&plat, plat.filename);
            status = (Action_OK == action) ? 0 : -1;
        }

        if (NULL == sys.cart_header) {
            nese_Action action = select_rom(
                    &plat, plat.filename, PLAT_FILENAME_SIZE
                );
            status = (Action_OK == action) ? 0 : -1;
        }
    }

    // This shall invoke menus as needed
    if (0 == status) {
        status = nese_start(&sys, &plat);
    }

    unload_cart(&plat.cart);

    plat_done(&plat);

    return status;
}