#include "zx_disk.h"
#include "z80.h"
#include <stdio.h>

#define ZX_FDC_MODE_IDLE        0
#define ZX_FDC_MODE_COMMAND     1
#define ZX_FDC_MODE_EXECUTION   2
#define ZX_FDC_MODE_RESULT      3

#define ZX_FDC_DATA_DIRECTION_INPUT     0x00
#define ZX_FDC_DATA_DIRECTION_OUTPUT    0x40

#define ZX_FDC_COMMAND_MASK                     0x1F
#define ZX_FDC_COMMAND_SPECIFY                  0x03
#define ZX_FDC_COMMAND_SENSE_DRIVE_STATUS       0x04
#define ZX_FDC_COMMAND_RECALIBRATE              0x07
#define ZX_FDC_COMMAND_SENSE_INTERRUPT_STATUS   0x08
#define ZX_FDC_COMMAND_SEEK                     0x0F

#define ZX_FDC_MAIN_DRIVE0_BUSY 1
#define ZX_FDC_MAIN_DRIVE1_BUSY 2
#define ZX_FDC_MAIN_DRIVE2_BUSY 4
#define ZX_FDC_MAIN_DRIVE3_BUSY 8
#define ZX_FDC_MAIN_BUSY        16
#define ZX_FDC_MAIN_EXEC_MODE   32
#define ZX_FDC_MAIN_DATA_DIR    64 // 0: CPU->FDC   1: FDC->CPU
#define ZX_FDC_MAIN_DATA_READY  128


namespace zx_disk
{
    uint8_t mode = ZX_FDC_MODE_IDLE;
    uint8_t call_count = 0;
    //uint8_t data_direction = 0x00;  // 0x40
    uint8_t fdd0busy = 0;
    uint8_t srt, hlt, hut, nd;
    bool seeking = false;

    uint8_t current_head = 0;
    uint8_t current_drive = 0;
    uint8_t current_track = 0;

    int zx_fdc_main_status_port_in(int port);
    int zx_fdc_data_port_in(int port);
    void zx_fdc_data_port_out(int port, int val);

    void init()
    {
        z80::connect_port(0x2ffd, 0xf002, zx_fdc_main_status_port_in, nullptr);
        z80::connect_port(0x3ffd, 0xf002, zx_fdc_data_port_in, zx_fdc_data_port_out);
    }

    void reset()
    {

    }

    uint8_t main_status_register()
    {
        const uint8_t val = (fdd0busy) |
                ((mode==ZX_FDC_MODE_IDLE) ? 0x00 : 0x10) |
                ((mode==ZX_FDC_MODE_EXECUTION) ? 0x20 : 0x00) |
                ((mode==ZX_FDC_MODE_RESULT) ? 0x40 : 0x00) |
                (0x80);
        return val;

    }

    int zx_fdc_main_status_port_in(int port)
    {
        printf("FDC port 0x2ffd IN\n");
        return main_status_register();
    }

    uint8_t ST0()
    {
        return current_drive | (current_head<<2) | (seeking ? 0x20 : 0x00) | (fdd0busy ? 0x00 : 0x40);
    }

    uint8_t ST3()
    {
        return current_drive | (current_head<<2) | 0x38; // ST3
    }

    void start_command(uint8_t command);

    uint8_t (*process_current_command)(uint8_t) = nullptr;
    uint8_t process_command_unknown(uint8_t command);
    uint8_t process_command_specify(uint8_t command);
    uint8_t process_command_sense_drive_status(uint8_t command);
    uint8_t process_command_recalibrate(uint8_t command);
    uint8_t process_command_sense_interrupt_status(uint8_t command);
    uint8_t process_command_seek(uint8_t command);

    int zx_fdc_data_port_in(int port)
    {
        printf("FDC port 0x3ffd IN\n");
        if (mode == ZX_FDC_MODE_COMMAND) {
            printf("IGNORED!\n");
            return 0;
        }
        if (process_current_command) return process_current_command(0);
        return 0;
    }

    void zx_fdc_data_port_out(int port, int val)
    {
        printf("FDC port 0x3ffd OUT: 0x%02x\n", val);
        if (mode == ZX_FDC_MODE_RESULT) {
            printf("IGNORED!\n");
            return;
        }
        if (process_current_command)
            process_current_command(val);
        else
            start_command(val & ZX_FDC_COMMAND_MASK);
    }

    void start_command(uint8_t command)
    {
        if ((fdd0busy) && (command != ZX_FDC_COMMAND_SENSE_INTERRUPT_STATUS)) return;

        mode = ZX_FDC_MODE_COMMAND;
        call_count = 1;
        switch(command)
        {
            case ZX_FDC_COMMAND_SPECIFY:
                process_current_command = process_command_specify;
                break;
            case ZX_FDC_COMMAND_SENSE_DRIVE_STATUS:
                process_current_command = process_command_sense_drive_status;
                break;
            case ZX_FDC_COMMAND_RECALIBRATE:
                process_current_command = process_command_recalibrate;
                fdd0busy = 1;
                break;
            case ZX_FDC_COMMAND_SENSE_INTERRUPT_STATUS:
                process_current_command = process_command_sense_interrupt_status;
                mode = ZX_FDC_MODE_RESULT;
                call_count = 0;
                break;
            case ZX_FDC_COMMAND_SEEK:
                process_current_command = process_command_seek;
                fdd0busy = 1;
                seeking = true;
                break;
            default:
            {
                process_current_command = process_command_unknown;
                mode = ZX_FDC_MODE_RESULT;
                call_count = 0;
            }
        }
    }


    // ===================================================================
    // FDC COMMAND: UNKNOWN
    // ===================================================================
    uint8_t process_command_unknown(uint8_t command)
    {
        process_current_command = nullptr;
        mode = ZX_FDC_MODE_IDLE;
        const uint8_t val = ST0();
        printf("--> (returning 0x%02x)\n", val);
        return val;
    }
    
    // ===================================================================
    // FDC COMMAND: SPECIFY (0x03)
    // ===================================================================
    uint8_t process_command_specify(uint8_t command)
    {
        switch (call_count) {
            case 1:
                srt = (command & 0xf0) >> 4;
                hut = command & 0x0f;
                call_count++;
                break;
            case 2:
                hlt = (command & 0xfe) >> 1;
                nd = command & 0x01;
                call_count=0;
                process_current_command = nullptr;
                mode = ZX_FDC_MODE_IDLE;
                break;
        }
        return 0;
    }

    // ===================================================================
    // FDC COMMAND: SENSE DRIVE STATUS (0x04)
    // ===================================================================
    uint8_t process_command_sense_drive_status(uint8_t command)
    {
        switch (mode)
        {
            case ZX_FDC_MODE_COMMAND:
                current_head = (command & 0x4)>>2;
                current_drive = command & 0x3;
                call_count = 0;
                mode = ZX_FDC_MODE_RESULT;
                break;
            case ZX_FDC_MODE_RESULT:
            {
                process_current_command = nullptr;
                mode = ZX_FDC_MODE_IDLE;
                const uint8_t val = ST3();
                printf("--> (returning 0x%02x)\n", val);
                return val;
            }
        }
        return 0;
    }

    // ===================================================================
    // FDC COMMAND: RECALIBRATE (0x07)
    // ===================================================================
    uint8_t process_command_recalibrate(uint8_t command)
    {
        switch (mode)
        {
            case ZX_FDC_MODE_COMMAND:
                current_drive = command & 0x3;
                call_count = 0;
                current_track = 0;
                process_current_command = nullptr;
                mode = ZX_FDC_MODE_IDLE;
                break;
        }
        return 0;
    }

    // ===================================================================
    // FDC COMMAND: SENSE INTERRUPT STATUS (0x08)
    // ===================================================================
    uint8_t process_command_sense_interrupt_status(uint8_t command)
    {
        switch (call_count)
        {
            case 0:
            {
                call_count++;
                const uint8_t val = ST0();
                printf("--> (returning 0x%02x)\n", val);
                return val;
            }
            case 1:
                process_current_command = nullptr;
                fdd0busy = 0;
                seeking = false;
                call_count = 0;
                mode = ZX_FDC_MODE_IDLE;
                printf("--> (returning 0x%02x)\n", current_track);
                return current_track;
        }
        return 0;
    }

    // ===================================================================
    // FDC COMMAND: SEEK (0x0F)
    // ===================================================================
    uint8_t process_command_seek(uint8_t command)
    {
        switch (call_count)
        {
            case 1:
            {
                current_head = (command & 0x4)>>2;
                current_drive = command & 0x3;
                call_count++;
                break;
            }
            case 2:
                current_track = command;
                process_current_command = nullptr;
                call_count = 0;
                mode = ZX_FDC_MODE_IDLE;
                break;
        }
        return 0;
    }
}