BMP-CodeEditor.c

#include <ctype.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/ioctl.h>
#include <termios.h>
#include <unistd.h>
#include <string.h>

/* REMEMBER!! THERE IS NO STRING TYPE IN C!
   ITS ALWAYS ARRAY OF CHARS WITH '\0' (null terminator) AT THE END  */

/*  k stands for 'key' but the name doesnt matter. could be anything. 
    And 0x1f is 00011111 in binary. it turns first 3 bits to zeros.
    For example C (01000011) becomes 00000011 via biteise AND operation
    because with AND only bitd that are both 1 remain 1. 
    In other owrds:
        01000011
    AND 00011111
       ---------
      = 00000011
*/
#define CTRL_KEY(k)  ((k) & 0x1f)

#define BMPCODEEDITOR_VERSION "0.0.1"

enum editorKey {
    /*Since first one is assigned to 1000, the others below it auto assign as
      1001, 1002, 1003, etc in C*/
    ARROW_LEFT = 1000,
    ARROW_RIGHT,  // = 1001
    ARROW_UP, // = 1002
    ARROW_DOWN,
    PAGE_UP,
    PAGE_DOWN, 
    HOME_KEY,
    END_KEY,
    DEL_KEY
};
/**************************************** DATA ****************************************/
struct editorConfig {
    int cx, cy;
    int screenrows;
    int screencols;
    struct termios orig_termios;
};

struct editorConfig E;

/************************************** TERMINAL **************************************/
void die(const char *s) {//check down for explanation for s

    /*write(fd, buffer, length) ...
      fd     = file descriptor (address where to send)
      buffer = pointer to stuff (bytes) to write
      length = how many bytes sending */
    write(STDOUT_FILENO, "\x1b[2J", 4); //ansi code for "clear screen"
    write(STDOUT_FILENO, "\x1b[H", 3); //ansi code for "move cursor to top left"

/*  So remember this: 's' is the name of the function/operation that failed.
    And perror(s) prints the error message that it gets from errno... So,
    it prints out like this: "(errorname): (error code/num from errno)       */
    perror(s); 
    exit(1);
}

void disableRawMode() {
    /*tcsetattr = terminal control set attributes*/
    if(tcsetattr(STDIN_FILENO, TCSAFLUSH, &E.orig_termios) == -1)
        die("tcsetattr");
}

void enableRawMode() {
    /*tcgetattr = terminal control get attributes*/
    if (tcgetattr(STDIN_FILENO, &E.orig_termios) == -1) die("tcgetattr");
    atexit(disableRawMode);

    struct termios raw = E.orig_termios;
    raw.c_iflag &= ~(BRKINT | ICRNL | INPCK | ISTRIP | IXON);
    raw.c_oflag &= ~(OPOST);
    raw.c_cflag |= (CS8);
    raw.c_lflag &= ~(ECHO | ICANON | IEXTEN | ISIG);
    raw.c_cc[VMIN] = 0;
    raw.c_cc[VTIME] = 1;

    if(tcsetattr(STDIN_FILENO, TCSAFLUSH, &raw) == -1) die("tcsetattr");
}

int editorReadKey()
{
    int nread;
    char c;
    /*check stdinput (usually keyboard) while output != success (1)*/
    while ((nread = read(STDIN_FILENO, &c, 1)) != 1)
    {
        /*if error (-1) && error != try again*/
        if (nread ==-1 && errno != EAGAIN) die("read");
    }
    /*Check if c = ESC or ANSI Escape Code*/
    if (c == '\x1b')
    {
        /*How many bytes (3) stored*/
        char seq[3];
        /*Expected:  seq[0] = '[',  seq[1] = some number,  seq[2] = '~' */

        /*if read(input, store in seq[0], 1byte) returns NOT ERROR (-1), retrn ESC key*/
        /*So these 2 lines are failsafe: if something goes wrong, return ESC*/
        if (read(STDIN_FILENO, &seq[0], 1) != 1) return '\x1b';
        if (read(STDIN_FILENO, &seq[1], 1) != 1) return '\x1b';

        if (seq[0] == '[')
        {
            if (seq[1] >= '0' && seq[1] <= '9')
            {
                if (read(STDIN_FILENO, &seq[2], 1) != 1) return '\x1b';
                if (seq[2] == '~')
                {
                    switch (seq[1])
                    {
                        case '1': return HOME_KEY;
                        case '3': return DEL_KEY;
                        case '4': return END_KEY;
                        case '5': return PAGE_UP;
                        case '6': return PAGE_DOWN;
                        case '7': return HOME_KEY;
                        case '8': return END_KEY;
                    }
                }
            }
            else
            {
                switch (seq[1]) 
                {
                    case 'A': return ARROW_UP;
                    case 'B': return ARROW_DOWN;
                    case 'C': return ARROW_RIGHT;
                    case 'D': return ARROW_LEFT;
                    case 'H': return HOME_KEY;
                    case 'F': return END_KEY;
                }
            }
        }
        /*The 0-form (letter O not zero) of these ansi sequences wokr on modern
          terminals only*/
        else if (seq[0] == 'O')
        {
            switch (seq[1])
            {
                case 'H': return HOME_KEY;
                case 'F': return END_KEY;
            }
        }
        /* return ESC Key if none of the above*/
        return '\x1b';
    }
    /*if c was NOT ESC, then return c (could be norm char)*/
    else
    {
        return c;
    }
}

int getCursorPosition(int *rows, int *cols) {
    char buf[32];
    unsigned int i = 0;

    /* So the error check here is != 4 this time because the buffer size is
       4 bytes (...as in 4 bytes checked successfully)   */
    if (write(STDOUT_FILENO, "\x1b[6n", 4) != 4) return -1;

    while (i < sizeof(buf) - 1) {
        if (read(STDIN_FILENO, &buf[i], 1) != 1) break;
        if (buf[i] == 'R') break;
        i++;
    }
    buf[i] = '\0';

    if (buf[0] != '\x1b' || buf[1] != '[') return -1;
    if (sscanf(&buf[2], "%d;%d", rows, cols) != 2) return -1;

    return 0;
}

int getWindowSize(int *rows, int *cols) {
    struct winsize ws;
    if (ioctl(STDOUT_FILENO, TIOCGWINSZ, &ws) == -1 || ws.ws_col == 0) {
        if (write(STDOUT_FILENO, "\x1b[999C\x1b[999B", 12) != 12) return -1;
        return getCursorPosition(rows, cols);
    } else {
        *cols = ws.ws_col;
        *rows = ws.ws_row;
        return 0;
    }
}
/*********************************** APPEND BUFFER ************************************/
struct abuf {
    char *b;
    int len;
};

#define ABUF_INIT {NULL, 0}

void abAppend(struct abuf *ab, const char *s, int len) {
    char *new = realloc(ab->b, ab->len + len);
    if (new == NULL) return;
    memcpy(&new[ab->len], s, len);
    ab->b = new;
    ab->len += len;
}
void abFree(struct abuf *ab) {
    free(ab->b);
}

/*************************************** OUTPUT ***************************************/
void editorDrawRows(struct abuf *ab) {
    int y;
    for (y = 0; y < E.screenrows; y++) {
        if (y == E.screenrows / 3) {
            char welcome[80];
            int welcomelen = snprintf(welcome, sizeof(welcome),
                "BMP CodeEditor -- version %s", BMPCODEEDITOR_VERSION);
            if (welcomelen > E.screencols) welcomelen = E.screencols;
            int padding = (E.screencols - welcomelen) / 2;
            if (padding) {
            abAppend(ab, "#", 1);
            padding--;
            }
            while (padding--) abAppend(ab, " ", 1);
            abAppend(ab, welcome, welcomelen);
            } else {
                abAppend(ab, "#", 1);
            }

            abAppend(ab, "\x1b[K", 3);
            if (y < E.screenrows - 1) {
            abAppend(ab, "\r\n", 2);
            }
    }
}

void editorRefreshScreen() {
    struct abuf ab = ABUF_INIT;
    abAppend(&ab, "\x1b[?25l", 6); /*hide cursor*/
    abAppend(&ab, "\x1b[H", 3);
    editorDrawRows(&ab);

    char buf[32];
    snprintf(buf, sizeof(buf), "\x1b[%d;%dH", E.cy + 1, E.cx + 1);
    abAppend(&ab, buf, strlen(buf));

    abAppend(&ab, "\x1b[?25h", 6); /*show cursor*/
    write(STDOUT_FILENO, ab.b, ab.len);
    abFree(&ab);
}


/*************************************** INPUT ****************************************/
void editorMoveCursor(int key) {
    switch (key) {
        case ARROW_LEFT:
            if (E.cx != 0) {
                E.cx--;
            }
            break;
        case ARROW_RIGHT:
            if (E.cx != E.screencols - 1) {
                E.cx++;
            }
            break;
        case ARROW_UP:
            if (E.cy != 0) {
                E.cy--;
            }
            break;
        case ARROW_DOWN:
            if (E.cy != E.screenrows - 1) {
            E.cy++;
            }
            break;
    }
}

void editorProcessKeypress() {
   /*value of editorReadKey() to new var C so it can be compared with switch case*/
    int c = editorReadKey();
    switch (c) {
        case CTRL_KEY('q'):
            write(STDOUT_FILENO, "\x1b[2J", 4);
            write(STDOUT_FILENO, "\x1b[H", 3);
            exit(0);
            break;

        case HOME_KEY:
            E.cx = 0;
            break;
        case END_KEY:
            E.cx = E.screencols - 1;
            break;


        case PAGE_UP:
        case PAGE_DOWN:
            {
                int times = E.screenrows;
                while (times--)
                    editorMoveCursor(c == PAGE_UP ? ARROW_UP : ARROW_DOWN);
            }
            break;

        case ARROW_UP:
        case ARROW_DOWN:
        case ARROW_LEFT:
        case ARROW_RIGHT:
            editorMoveCursor(c);
            break;
    }
}

/**************************************** INIT ****************************************/
void initEditor() {
    E.cx = 0;
    E.cy = 0;
    if (getWindowSize(&E.screenrows, &E.screencols) == -1) die("getWindowSize");
}

int main() {
    enableRawMode();
    initEditor();
    write(STDOUT_FILENO, "\x1b[38;2;255;171;35m", 19); /*SET COLOR TO #FFAB23*/

    while (1) {
        editorRefreshScreen();
        editorProcessKeypress();
    }

    return 0;
}