#include <defs.h>
#include <x86.h>
#include <stdio.h>
#include <string.h>
#include <kbdreg.h>
#include <picirq.h>
#include <trap.h>

/* stupid I/O delay routine necessitated by historical PC design flaws */
static void
delay(void) {
    inb(0x84);
    inb(0x84);
    inb(0x84);
    inb(0x84);
}

/***** Serial I/O code *****/
#define COM1            0x3F8

#define COM_RX          0       // In:  Receive buffer (DLAB=0)
#define COM_TX          0       // Out: Transmit buffer (DLAB=0)
#define COM_DLL         0       // Out: Divisor Latch Low (DLAB=1)
#define COM_DLM         1       // Out: Divisor Latch High (DLAB=1)
#define COM_IER         1       // Out: Interrupt Enable Register
#define COM_IER_RDI     0x01    // Enable receiver data interrupt
#define COM_IIR         2       // In:  Interrupt ID Register
#define COM_FCR         2       // Out: FIFO Control Register
#define COM_LCR         3       // Out: Line Control Register
#define COM_LCR_DLAB    0x80    // Divisor latch access bit
#define COM_LCR_WLEN8   0x03    // Wordlength: 8 bits
#define COM_MCR         4       // Out: Modem Control Register
#define COM_MCR_RTS     0x02    // RTS complement
#define COM_MCR_DTR     0x01    // DTR complement
#define COM_MCR_OUT2    0x08    // Out2 complement
#define COM_LSR         5       // In:  Line Status Register
#define COM_LSR_DATA    0x01    // Data available
#define COM_LSR_TXRDY   0x20    // Transmit buffer avail
#define COM_LSR_TSRE    0x40    // Transmitter off

#define MONO_BASE       0x3B4
#define MONO_BUF        0xB0000
#define CGA_BASE        0x3D4
#define CGA_BUF         0xB8000
#define CRT_ROWS        25
#define CRT_COLS        80
#define CRT_SIZE        (CRT_ROWS * CRT_COLS)

#define LPTPORT         0x378

static uint16_t *crt_buf;
static uint16_t crt_pos;
static uint16_t addr_6845;

/* TEXT-mode CGA/VGA display output */
// 显示器初始化，CGA 是 Color Graphics Adapter 的缩写
// CGA显存按照下面的方式映射：
//   -- 0xB0000 - 0xB7777 单色字符模式
//   -- 0xB8000 - 0xBFFFF 彩色字符模式及 CGA 兼容图形模式
// 6845芯片是IBM PC中的视频控制器
// CPU通过IO地址0x3B4-0x3B5来驱动6845控制单色显示，通过IO地址0x3D4-0x3D5来控制彩色显示。
//    -- 数据寄存器 映射 到 端口 0x3D5或0x3B5 
//    -- 索引寄存器 0x3D4或0x3B4,决定在数据寄存器中的数据表示什么。
static void
cga_init(void) {
    volatile uint16_t *cp = (uint16_t *)CGA_BUF;   //CGA_BUF: 0xB8000 (彩色显示的显存物理基址)
    uint16_t was = *cp;                                            //保存当前光标所在值
    *cp = (uint16_t) 0xA55A;
    if (*cp != 0xA55A) {
        cp = (uint16_t*)MONO_BUF;                         //黑白显示的显存基址 MONO_BUF： 0xB0000
        addr_6845 = MONO_BASE;                           //黑白显示控制的IO地址，MONO_BASE: 0x3B4
    } else {
        *cp = was;                                                      //还原原来的光标所在值
        addr_6845 = CGA_BASE;                               // 彩色显示控制的IO地址， CGA_BASE: 0x3D4 
    }

    // Extract cursor location
    // 6845索引寄存器的index 0x0E（及十进制的14）== 光标位置(高位)
    // 6845索引寄存器的index 0x0F（及十进制的15）== 光标位置(低位)
    // 6845 reg 15 : Cursor Address (Low Byte)
    uint32_t pos;
    outb(addr_6845, 14);                                        
    pos = inb(addr_6845 + 1) << 8;                       //读出了光标位置(高位)
    outb(addr_6845, 15);
    pos |= inb(addr_6845 + 1);                             //读出了光标位置(低位)

    crt_buf = (uint16_t*) cp;                                  //crt_buf是CGA显存起始地址
    crt_pos = pos;                                                  //crt_pos是CGA当前光标位置
}

static bool serial_exists = 0;

static void
serial_init(void) {
    // Turn off the FIFO
    outb(COM1 + COM_FCR, 0);

    // Set speed; requires DLAB latch
    outb(COM1 + COM_LCR, COM_LCR_DLAB);
    outb(COM1 + COM_DLL, (uint8_t) (115200 / 9600));
    outb(COM1 + COM_DLM, 0);

    // 8 data bits, 1 stop bit, parity off; turn off DLAB latch
    outb(COM1 + COM_LCR, COM_LCR_WLEN8 & ~COM_LCR_DLAB);

    // No modem controls
    outb(COM1 + COM_MCR, 0);
    // Enable rcv interrupts
    outb(COM1 + COM_IER, COM_IER_RDI);

    // Clear any preexisting overrun indications and interrupts
    // Serial port doesn't exist if COM_LSR returns 0xFF
    serial_exists = (inb(COM1 + COM_LSR) != 0xFF);
    (void) inb(COM1+COM_IIR);
    (void) inb(COM1+COM_RX);

    if (serial_exists) {
        pic_enable(IRQ_COM1);
    }
}

static void
lpt_putc_sub(int c) {
    int i;
    for (i = 0; !(inb(LPTPORT + 1) & 0x80) && i < 12800; i ++) {
        delay();
    }
    outb(LPTPORT + 0, c);
    outb(LPTPORT + 2, 0x08 | 0x04 | 0x01);
    outb(LPTPORT + 2, 0x08);
}

/* lpt_putc - copy console output to parallel port */
static void
lpt_putc(int c) {
    if (c != '\b') {
        lpt_putc_sub(c);
    }
    else {
        lpt_putc_sub('\b');
        lpt_putc_sub(' ');
        lpt_putc_sub('\b');
    }
}

/* cga_putc - print character to console */
static void
cga_putc(int c) {
    // set black on white
    if (!(c & ~0xFF)) {
        c |= 0x0700;
    }

    switch (c & 0xff) {
    case '\b':
        if (crt_pos > 0) {
            crt_pos --;
            crt_buf[crt_pos] = (c & ~0xff) | ' ';
        }
        break;
    case '\n':
        crt_pos += CRT_COLS;
    case '\r':
        crt_pos -= (crt_pos % CRT_COLS);
        break;
    default:
        crt_buf[crt_pos ++] = c;     // write the character
        break;
    }

    // What is the purpose of this?
    if (crt_pos >= CRT_SIZE) {
        int i;
        memmove(crt_buf, crt_buf + CRT_COLS, (CRT_SIZE - CRT_COLS) * sizeof(uint16_t));
        for (i = CRT_SIZE - CRT_COLS; i < CRT_SIZE; i ++) {
            crt_buf[i] = 0x0700 | ' ';
        }
        crt_pos -= CRT_COLS;
    }

    // move that little blinky thing
    outb(addr_6845, 14);
    outb(addr_6845 + 1, crt_pos >> 8);
    outb(addr_6845, 15);
    outb(addr_6845 + 1, crt_pos);
}

static void
serial_putc_sub(int c) {
    int i;
    for (i = 0; !(inb(COM1 + COM_LSR) & COM_LSR_TXRDY) && i < 12800; i ++) {
        delay();
    }
    outb(COM1 + COM_TX, c);
}

/* serial_putc - print character to serial port */
static void
serial_putc(int c) {
    if (c != '\b') {
        serial_putc_sub(c);
    }
    else {
        serial_putc_sub('\b');
        serial_putc_sub(' ');
        serial_putc_sub('\b');
    }
}

/* *
 * Here we manage the console input buffer, where we stash characters
 * received from the keyboard or serial port whenever the corresponding
 * interrupt occurs.
 * */

#define CONSBUFSIZE 512

static struct {
    uint8_t buf[CONSBUFSIZE];
    uint32_t rpos;
    uint32_t wpos;
} cons;

/* *
 * cons_intr - called by device interrupt routines to feed input
 * characters into the circular console input buffer.
 * */
static void
cons_intr(int (*proc)(void)) {
    int c;
    while ((c = (*proc)()) != -1) {
        if (c != 0) {
            cons.buf[cons.wpos ++] = c;
            if (cons.wpos == CONSBUFSIZE) {
                cons.wpos = 0;
            }
        }
    }
}

/* serial_proc_data - get data from serial port */
static int
serial_proc_data(void) {
    if (!(inb(COM1 + COM_LSR) & COM_LSR_DATA)) {
        return -1;
    }
    int c = inb(COM1 + COM_RX);
    if (c == 127) {
        c = '\b';
    }
    return c;
}

/* serial_intr - try to feed input characters from serial port */
void
serial_intr(void) {
    if (serial_exists) {
        cons_intr(serial_proc_data);
    }
}

/***** Keyboard input code *****/

#define NO              0

#define SHIFT           (1<<0)
#define CTL             (1<<1)
#define ALT             (1<<2)

#define CAPSLOCK        (1<<3)
#define NUMLOCK         (1<<4)
#define SCROLLLOCK      (1<<5)

#define E0ESC           (1<<6)

static uint8_t shiftcode[256] = {
    [0x1D] CTL,
    [0x2A] SHIFT,
    [0x36] SHIFT,
    [0x38] ALT,
    [0x9D] CTL,
    [0xB8] ALT
};

static uint8_t togglecode[256] = {
    [0x3A] CAPSLOCK,
    [0x45] NUMLOCK,
    [0x46] SCROLLLOCK
};

static uint8_t normalmap[256] = {
    NO,   0x1B, '1',  '2',  '3',  '4',  '5',  '6',  // 0x00
    '7',  '8',  '9',  '0',  '-',  '=',  '\b', '\t',
    'q',  'w',  'e',  'r',  't',  'y',  'u',  'i',  // 0x10
    'o',  'p',  '[',  ']',  '\n', NO,   'a',  's',
    'd',  'f',  'g',  'h',  'j',  'k',  'l',  ';',  // 0x20
    '\'', '`',  NO,   '\\', 'z',  'x',  'c',  'v',
    'b',  'n',  'm',  ',',  '.',  '/',  NO,   '*',  // 0x30
    NO,   ' ',  NO,   NO,   NO,   NO,   NO,   NO,
    NO,   NO,   NO,   NO,   NO,   NO,   NO,   '7',  // 0x40
    '8',  '9',  '-',  '4',  '5',  '6',  '+',  '1',
    '2',  '3',  '0',  '.',  NO,   NO,   NO,   NO,   // 0x50
    [0xC7] KEY_HOME,    [0x9C] '\n' /*KP_Enter*/,
    [0xB5] '/' /*KP_Div*/,  [0xC8] KEY_UP,
    [0xC9] KEY_PGUP,    [0xCB] KEY_LF,
    [0xCD] KEY_RT,      [0xCF] KEY_END,
    [0xD0] KEY_DN,      [0xD1] KEY_PGDN,
    [0xD2] KEY_INS,     [0xD3] KEY_DEL
};

static uint8_t shiftmap[256] = {
    NO,   033,  '!',  '@',  '#',  '$',  '%',  '^',  // 0x00
    '&',  '*',  '(',  ')',  '_',  '+',  '\b', '\t',
    'Q',  'W',  'E',  'R',  'T',  'Y',  'U',  'I',  // 0x10
    'O',  'P',  '{',  '}',  '\n', NO,   'A',  'S',
    'D',  'F',  'G',  'H',  'J',  'K',  'L',  ':',  // 0x20
    '"',  '~',  NO,   '|',  'Z',  'X',  'C',  'V',
    'B',  'N',  'M',  '<',  '>',  '?',  NO,   '*',  // 0x30
    NO,   ' ',  NO,   NO,   NO,   NO,   NO,   NO,
    NO,   NO,   NO,   NO,   NO,   NO,   NO,   '7',  // 0x40
    '8',  '9',  '-',  '4',  '5',  '6',  '+',  '1',
    '2',  '3',  '0',  '.',  NO,   NO,   NO,   NO,   // 0x50
    [0xC7] KEY_HOME,    [0x9C] '\n' /*KP_Enter*/,
    [0xB5] '/' /*KP_Div*/,  [0xC8] KEY_UP,
    [0xC9] KEY_PGUP,    [0xCB] KEY_LF,
    [0xCD] KEY_RT,      [0xCF] KEY_END,
    [0xD0] KEY_DN,      [0xD1] KEY_PGDN,
    [0xD2] KEY_INS,     [0xD3] KEY_DEL
};

#define C(x) (x - '@')

static uint8_t ctlmap[256] = {
    NO,      NO,      NO,      NO,      NO,      NO,      NO,      NO,
    NO,      NO,      NO,      NO,      NO,      NO,      NO,      NO,
    C('Q'),  C('W'),  C('E'),  C('R'),  C('T'),  C('Y'),  C('U'),  C('I'),
    C('O'),  C('P'),  NO,      NO,      '\r',    NO,      C('A'),  C('S'),
    C('D'),  C('F'),  C('G'),  C('H'),  C('J'),  C('K'),  C('L'),  NO,
    NO,      NO,      NO,      C('\\'), C('Z'),  C('X'),  C('C'),  C('V'),
    C('B'),  C('N'),  C('M'),  NO,      NO,      C('/'),  NO,      NO,
    [0x97] KEY_HOME,
    [0xB5] C('/'),      [0xC8] KEY_UP,
    [0xC9] KEY_PGUP,    [0xCB] KEY_LF,
    [0xCD] KEY_RT,      [0xCF] KEY_END,
    [0xD0] KEY_DN,      [0xD1] KEY_PGDN,
    [0xD2] KEY_INS,     [0xD3] KEY_DEL
};

static uint8_t *charcode[4] = {
    normalmap,
    shiftmap,
    ctlmap,
    ctlmap
};

/* *
 * kbd_proc_data - get data from keyboard
 *
 * The kbd_proc_data() function gets data from the keyboard.
 * If we finish a character, return it, else 0. And return -1 if no data.
 * */
static int
kbd_proc_data(void) {
    int c;
    uint8_t data;
    static uint32_t shift;

    if ((inb(KBSTATP) & KBS_DIB) == 0) {
        return -1;
    }

    data = inb(KBDATAP);

    if (data == 0xE0) {
        // E0 escape character
        shift |= E0ESC;
        return 0;
    } else if (data & 0x80) {
        // Key released
        data = (shift & E0ESC ? data : data & 0x7F);
        shift &= ~(shiftcode[data] | E0ESC);
        return 0;
    } else if (shift & E0ESC) {
        // Last character was an E0 escape; or with 0x80
        data |= 0x80;
        shift &= ~E0ESC;
    }

    shift |= shiftcode[data];
    shift ^= togglecode[data];

    c = charcode[shift & (CTL | SHIFT)][data];
    if (shift & CAPSLOCK) {
        if ('a' <= c && c <= 'z')
            c += 'A' - 'a';
        else if ('A' <= c && c <= 'Z')
            c += 'a' - 'A';
    }

    // Process special keys
    // Ctrl-Alt-Del: reboot
    if (!(~shift & (CTL | ALT)) && c == KEY_DEL) {
        cprintf("Rebooting!\n");
        outb(0x92, 0x3); // courtesy of Chris Frost
    }
    return c;
}

/* kbd_intr - try to feed input characters from keyboard */
static void
kbd_intr(void) {
    cons_intr(kbd_proc_data);
}

static void
kbd_init(void) {
    // drain the kbd buffer
    kbd_intr();
    pic_enable(IRQ_KBD);
}

/* cons_init - initializes the console devices */
void
cons_init(void) {
    cga_init();
    serial_init();
    kbd_init();
    if (!serial_exists) {
        cprintf("serial port does not exist!!\n");
    }
}

/* cons_putc - print a single character @c to console devices */
void
cons_putc(int c) {
    lpt_putc(c);
    cga_putc(c);
    serial_putc(c);
}

/* *
 * cons_getc - return the next input character from console,
 * or 0 if none waiting.
 * */
int
cons_getc(void) {
    int c;

    // poll for any pending input characters,
    // so that this function works even when interrupts are disabled
    // (e.g., when called from the kernel monitor).
    serial_intr();
    kbd_intr();

    // grab the next character from the input buffer.
    if (cons.rpos != cons.wpos) {
        c = cons.buf[cons.rpos ++];
        if (cons.rpos == CONSBUFSIZE) {
            cons.rpos = 0;
        }
        return c;
    }
    return 0;
}