/*
 *	This file is not a part of musl-tcc,but a standalone editor which
 *	is used to check the usability of musl-tcc
 */

/*** includes ***/

// feature test macro ??
#define _DEFAULT_SOURCE
#define _BSD_SOURCE
#define _GNU_SOURCE

#include <ctype.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdarg.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>  // Input/Output ConTroL
#include <sys/types.h>
#include <termios.h>
#include <time.h>
#include <unistd.h>

/*** defines ***/

// Cool ascii thing, clearing bits 5 and 6 gets the control sequence associated with that character
// Also bit five toggles lowercase and uppercase
#define CTRL_KEY(k) ((k) & 0x1f)

#define PICO_VERSION "0.0.1"
#define PICO_TAB_STOP 8
#define PICO_QUIT_TIMES 3

enum EditorKey {
    BACKSPACE = 127,
    ARROW_LEFT = 1000,
    ARROW_RIGHT,
    ARROW_UP,
    ARROW_DOWN,
    DEL_KEY,
    HOME_KEY,
    END_KEY,
    PAGE_UP,
    PAGE_DOWN,
};

enum EditorHighlight {
    HL_NORMAL = 0,
    HL_COMMENT,
    HL_MLCOMMENT,
    HL_KEYWORD1,
    HL_KEYWORD2,
    HL_STRING,
    HL_NUMBER,
    HL_MATCH
};

#define HL_HIGHLIGHT_NUMBERS (1<<0)
#define HL_HIGHLIGHT_STRINGS (1<<1)

/*** data ***/

typedef struct {
    char* filetype;
    char** filematch;
    char** keywords;
    char* singleline_comment_start;
    char* multiline_comment_start;
    char* multiline_comment_end;
    int flags;
} EditorSyntax;

typedef struct {
    int idx;
    int size;
    int rsize;  // The size of the render of the row (tabs are more than one character)
    char *chars;
    char *render;
    unsigned char* hl;  // Highlight
    int hl_open_comment;
} Row;

struct EditorConfig {
    int cx, cy;
    int rx;     // index into the render field
    int rowoff;
    int coloff;
    int screenrows;
    int screencols;
    int numrows;
    Row *row;
    int dirty;
    char *filename;
    char statusmsg[80];
    time_t statusmsg_time;
    EditorSyntax* syntax;
    struct termios orig_termios;
};

struct EditorConfig E;

/*** filetypes ***/

char* C_HL_extensions[] = { ".c", ".h", ".cpp", NULL };
char* C_HL_keywords[] = {
    "switch", "if", "while", "for", "break", "continue", "return", "else", "struct", "union", "typedef", "static", "enum", "case",
    "int|", "long|", "double|", "float|", "char|", "float|", "unsigned|", "signed|", "void|", NULL
};

EditorSyntax HLDB[] = {
    {
        "c",
        C_HL_extensions,
        C_HL_keywords,
        "//", "/*", "*/",
        HL_HIGHLIGHT_NUMBERS | HL_HIGHLIGHT_STRINGS
    }
};

// HighLight DataBase Entries
#define HLDB_ENTRIES (sizeof(HLDB) / sizeof(HLDB[0]))

/*** prototypes ***/
/* c was meant to be compiled in a single pass */

void editor_set_status_message(const char *fmt, ...);
void editor_refresh_screen();
char* editor_prompt(char* prompt, void (*callback)(char*, int));

/*** terminal ***/

void die(const char *s) {
    // Clear screen
    write(STDOUT_FILENO, "\x1b[2J", 4);
    write(STDOUT_FILENO, "\x1b[H", 3);

    // Most libc functions that fail set the global errno variable to indicate what the error was.
    // `perror` looks at errno and prints a descriptive error message for it.
    // It also prints the given string.
    perror(s);
    // Exit with status of 1, indicating error, like an non-zero exit code.
    exit(1);
}

void disable_raw_mode() {
    if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &E.orig_termios) == -1)
        die("tcsetattr");
}

void enable_raw_mode() {
    if (tcgetattr(STDIN_FILENO, &E.orig_termios) == -1)
        die("tcgetattr");
    atexit(disable_raw_mode);

    struct termios raw = E.orig_termios;

    // Flags documented with * are usually already off and/or don't apply, but good practices

    // IXON: When on enables C-s and C-q, which involve "software control flow".
    //      stands for input XON because C-s and C-q are XON and XOFF.
    // ICRNL: When on enables coercing a \r without a \n to a \n (C-m is \r and C-j is \n).
    //      stands for input carriage return new line.
    // *BRKINT: When on a "break condition" will cause a SIGINT signal to be sent.
    // *INPCK: When on enables parity checking, which doesn't seem to apply to modern terminal emulators.
    // *ISTRIP: When on enables causes the high bit to be 0 for every input byte.
    raw.c_iflag &= ~(IXON | ICRNL | BRKINT | INPCK | ISTRIP);

    // OPOST: When on enables output processing, in reality the only feature would be coercing \n into \r\n.
    //      This means whenever we want a new line we have to do \r\n, otherwise the cursor will not
    //      go to the start of the line and will just move down.
    raw.c_oflag &= ~(OPOST);

    // *CS8: not a flag, a mask. Sets the character size to 8=bits per bytes, lmao, imagine needing this.
    raw.c_cflag |= (CS8);

    // ECHO: When on enables echoing back of input.
    // ICANON: When on enables reading line by line (we want it byte by byte).
    // ISIG: When on enables SIGINT and SIGTSTP from C-c and C-z, respectively.
    //      these are signal interrupt and signal temporary stop.
    // IEXTEN: When on enables C-v to send another character "literally" (e.g. C-v and C-c would only send a literal 3 and not SIGINT).
    raw.c_lflag &= ~(ECHO | ICANON | ISIG | IEXTEN);

    // cc stands for control characters
    // Both measured in tenths of a second.

    // Minimum amount of time before read returns.
    raw.c_cc[VMIN] = 0;
    // Maximum amount of time to wait before read returns.
    //      On time out read() returns 0.
    raw.c_cc[VTIME] = 1;

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

int editor_read_key() {
    // read in character
    int nread;
    char c;
    while ((nread = read(STDIN_FILENO, &c, 1)) != 1) {
        if (nread == -1 && errno != EAGAIN)
            die("read");
    }

    // Process character if escape character
    if (c == '\x1b') {
        char seq[3];

        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;
                }
            }
        } else if (seq[0] == 'O') {
            switch (seq[1]) {
                case 'H': return HOME_KEY;
                case 'F': return END_KEY;
            }
        }

        return '\x1b';

    } else {
        return c;
    }
}

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

    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++;
    }

    // printf expected a null byte at the end
    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 get_window_size(int *rows, int *cols) {
    struct winsize ws;

    // Terminal IOCtl Get Window Size
    if (ioctl(STDOUT_FILENO, TIOCGWINSZ, &ws) == -1 || ws.ws_col == 0) {
        if (write(STDOUT_FILENO, "\x1b[999C\x1b[999B", 12) != 12) 
            return -1;
        return get_cursor_position(rows, cols);
    } else {
        *cols = ws.ws_col;
        *rows = ws.ws_row;
        return 0;
    }
}

/*** syntax highlighting ***/

int is_separator(int c) {
    return isspace(c) || c == '\0' || strchr(",.()+-/*=~%<>[];", c) != NULL;
}

void editor_update_syntax(Row* row) {
    row->hl = realloc(row->hl, row->rsize);
    memset(row->hl, HL_NORMAL, row->rsize);

    if (E.syntax == NULL)
        return;

    char** keywords = E.syntax->keywords;

    char* scs = E.syntax->singleline_comment_start;
    char* mcs = E.syntax->multiline_comment_start;
    char* mce = E.syntax->multiline_comment_end;

    int scs_len = scs ? strlen(scs) : 0;
    int mcs_len = scs ? strlen(mcs) : 0;
    int mce_len = scs ? strlen(mce) : 0;

    int prev_sep = 1;
    int in_string = 0;
    int in_comment = (row->idx > 0 && E.row[row->idx - 1].hl_open_comment);

    int i = 0;
    while (i < row->rsize) {
        char c = row->render[i];
        unsigned char prev_hl = (i > 0) ? row->hl[i - 1] : HL_NORMAL;

        if (scs_len && !in_string && !in_comment) {
            if (!strncmp(&row->render[i], scs, scs_len)) {
                memset(&row->hl[i], HL_COMMENT, row->rsize - i);
                break;
            }
        }

        if (mcs_len && mce_len && !in_string) {
            if (in_comment) {
                row->hl[i] = HL_MLCOMMENT;
                if (!strncmp(&row->render[i], mce, mce_len)) {
                    memset(&row->hl[i], HL_MLCOMMENT, mce_len);
                    i += mce_len;
                    in_comment = 0;
                    prev_sep = 1;
                    continue;
                } else {
                    i++;
                    continue;
                }
            } else if (!strncmp(&row->render[i], mcs, mcs_len)) {
                memset(&row->hl[i], HL_MLCOMMENT, mcs_len);
                i += mcs_len;
                in_comment = 1;
                continue;
            }
        }

        if (E.syntax->flags & HL_HIGHLIGHT_STRINGS) {
            if (in_string) {
                row->hl[i] = HL_STRING;
                // backslash escapes strings
                if (c == '\\' && i + 1 < row->rsize) {
                    row->hl[i + 1] = HL_STRING;
                    i += 2;
                    continue;
                }
                if (c == in_string)
                    in_string = 0;
                i++;
                prev_sep = 1;
                continue;
            } else {
                if (c == '"' || c == '\'') {
                    in_string = c;
                    row->hl[i] = HL_STRING;
                    i++;
                    continue;
                }
            }
        }

        if (E.syntax->flags & HL_HIGHLIGHT_NUMBERS) {
            if ( (isdigit(c) && (prev_sep || prev_hl == HL_NUMBER)) || 
                (c == '.' && prev_hl == HL_NUMBER)
            ) {
                row->hl[i] = HL_NUMBER;
                i++;
                prev_sep = 0;
                continue;
            }
        }

        if (prev_sep) {
            int j;
            for (j = 0; keywords[j]; j++) {
                int klen = strlen(keywords[j]);
                int kw2 = keywords[j][klen-1] == '|';
                if (kw2)
                    klen--;

                if (
                    !strncmp(&row->render[i], keywords[j], klen) &&
                    is_separator(row->render[i + klen])
                ) {
                    memset(&row->hl[i], kw2 ? HL_KEYWORD2 : HL_KEYWORD1, klen);
                    i += klen;
                    // this break gets us to the if statement to continue
                    break;
                }
            }
            // Triggered on break
            if (keywords[j] != NULL) {
                prev_sep = 0;
                continue;
            }
        }

        prev_sep = is_separator(c);
        i++;
    }

    // update next rows if this line has the start of a multiline comment
    int changed = (row->hl_open_comment != in_comment);
    row->hl_open_comment = in_comment;
    if (changed && row->idx + 1 < E.numrows)
        editor_update_syntax(&E.row[row->idx + 1]);
}

int editor_syntax_to_color(int hl) {
    switch (hl) {
        case HL_COMMENT: 
        case HL_MLCOMMENT: return 36;
        case HL_STRING: return 35;
        case HL_KEYWORD1: return 33;
        case HL_KEYWORD2: return 32;
        case HL_NUMBER: return 31;
        case HL_MATCH: return 34;
        default: return 37;
    }
}

void editor_select_syntax_highlight() {
    E.syntax = NULL;
    if (E.filename == NULL)
        return;

    char* ext = strrchr(E.filename, '.');

    for (unsigned int j = 0; j < HLDB_ENTRIES; j++) {
        EditorSyntax* s = &HLDB[j];
        unsigned int i = 0;
        while (s->filematch[i]) {
            int is_ext = (s->filematch[i][0] == '.');
            if (
                (is_ext && ext && !strcmp(ext, s->filematch[i])) ||
                (!is_ext && strstr(E.filename, s->filematch[i]))
            ) {
                E.syntax = s;

                int filerow;
                for (filerow = 0; filerow < E.numrows; filerow++) {
                    editor_update_syntax(&E.row[filerow]);
                }

                return;
            }
            i++;
        }
    }
}

/*** row operations ***/

int editor_row_cx_to_rx(Row *row, int cx) {
    int rx = 0;
    int j;
    for (j = 0; j < cx; j++) {
        if (row->chars[j] == '\t')
            rx += (PICO_TAB_STOP - 1) - (rx % PICO_TAB_STOP);
        rx++;
    }
    return rx;
}

int editor_row_rx_to_cx(Row* row, int rx) {
    int cur_rx = 0;
    int cx;
    for (cx = 0; cx < row->size; cx++) {
        if (row->chars[cx] == '\t') {
            cur_rx += (PICO_TAB_STOP - 1) - (cur_rx % PICO_TAB_STOP);
        }
        cur_rx++;

        if (cur_rx > rx)
            return cx;
    }

    return cx;
}

void editor_update_row(Row* row) {
    // used for iteration twice
    int j;

    int tabs = 0;
    for (j = 0; j < row->size; j++)
        if (row->chars[j] == '\t') 
            tabs++;

    free(row->render);
    row->render = malloc(row->size + tabs * (PICO_TAB_STOP - 1) + 1);

    int idx = 0;
    for (j = 0; j < row->size; j++) {
        if (row->chars[j] == '\t') {
            row->render[idx++] = ' ';
            // get us to the next tab spot
            while (idx % PICO_TAB_STOP != 0) row->render[idx++] = ' ';
        } else {
            row->render[idx++] = row->chars[j];
        }
    }
    row->render[idx] = '\0';
    row->rsize = idx;

    editor_update_syntax(row);
}

void editor_insert_row(int at, char* s, size_t len) {
    if (at < 0 || at > E.numrows)
        return;

    // Allocate space for the new row
    E.row = realloc(E.row, sizeof(Row) * (E.numrows + 1));
    memmove(&E.row[at + 1], &E.row[at], sizeof(Row) * (E.numrows - at));
    for (int j = at + 1; j <= E.numrows; j++)
        E.row[j].idx++;

    E.row[at].idx = at;

    E.row[at].size = len;
    E.row[at].chars = malloc(len + 1);
    memcpy(E.row[at].chars, s, len);
    E.row[at].chars[len] = '\0';

    E.row[at].rsize = 0;
    E.row[at].render = NULL;
    E.row[at].hl = NULL;
    E.row[at].hl_open_comment = 0;
    editor_update_row(&E.row[at]);

    E.numrows++;
    E.dirty++;
}

void editor_free_row(Row* row) {
    free(row->render);
    free(row->chars);
    free(row->hl);
}

void editor_del_row(int at) {
    if (at < 0 || at >= E.numrows)
        return;
    editor_free_row(&E.row[at]);
    memmove(&E.row[at], &E.row[at + 1], sizeof(Row) * (E.numrows - at - 1));
    for (int j = at; j < E.numrows - 1; j++)
        E.row[j].idx--;

    E.numrows--;
    E.dirty++;
}

void editor_row_insert_char(Row* row, int at, int c) {
    if (at < 0 || at > row->size) 
        at = row->size;
    // allocate one more byte for the new character, and one more byte for the null byte
    row->chars = realloc(row->chars, row->size + 2);
    // like memcpy, but safe to use if the source and destination places overlap
    memmove(&row->chars[at + 1], &row->chars[at], row->size - at + 1);
    row->size++;
    row->chars[at] = c;
    editor_update_row(row);
    E.dirty++;
}

void editor_row_append_string(Row* row, char* s, size_t len) {
    row->chars = realloc(row->chars, row->size + len + 1);
    memcpy(&row->chars[row->size], s, len);
    row->size += len;
    row->chars[row->size] = '\0';
    editor_update_row(row);
    E.dirty++;
}

void editor_row_del_char(Row* row, int at) {
    if (at < 0 || at >= row->size)
        return;
    // include the NULL byte!
    memmove(&row->chars[at], &row->chars[at + 1], row->size - at);
    row->size--;
    editor_update_row(row);
    E.dirty++;
}

/*** editor operations ***/

void editor_insert_char(int c) {
    if (E.cy == E.numrows) {
        editor_insert_row(E.numrows, "", 0);
    }
    editor_row_insert_char(&E.row[E.cy], E.cx, c);
    E.cx++;
}

void editor_insert_newline() {
    if (E.cx == 0) {
        editor_insert_row(E.cy, "", 0);
    } else {
        Row* row = &E.row[E.cy];
        editor_insert_row(E.cy + 1, &row->chars[E.cx], row->size - E.cx);
        // Reassign because memmove might invalidate it (uhhhhh)
        row = &E.row[E.cy];
        row->size = E.cx;
        row->chars[row->size] = '\0';
        editor_update_row(row);
    }
    E.cy++;
    E.cx = 0;
}

void editor_del_char() {
    if (E.cy == E.numrows)
        return;
    if (E.cx == 0 && E.cy == 0)
        return;

    Row* row = &E.row[E.cy];
    if (E.cx > 0) {
        editor_row_del_char(row, E.cx - 1);
        E.cx--;
    } else {
        E.cx = E.row[E.cy - 1].size;
        editor_row_append_string(&E.row[E.cy - 1], row->chars, row->size);
        editor_del_row(E.cy);
        E.cy--;
    }
}

/*** file i/o ***/

// Returns a string of all the rows
// also modifies buflen to be the length of the string
char* editor_rows_to_string(int* buflen) {
    int totlen = 0;
    int j;
    for (j = 0; j < E.numrows; j++) {
        totlen += E.row[j].size + 1;
    }
    *buflen = totlen;

    char* buf = malloc(totlen);
    char* p = buf;
    for (j = 0; j < E.numrows; j++) {
        memcpy(p, E.row[j].chars, E.row[j].size);
        p += E.row[j].size;
        *p = '\n';
        p++;
    }

    return buf;
}

void editor_open(char *filename) {
    free(E.filename);
    E.filename = strdup(filename);

    editor_select_syntax_highlight();

    FILE *fp = fopen(filename, "r");
    if (!fp) die("fopen");

    char *line = NULL;
    size_t linecap = 0;     // This type is used for sizes of objects
    ssize_t linelen;        // This type is used for indicating errors (and also success ig)

    // Read line from file into `line` into buffer of current size `linecap` from `fp`.
    while ((linelen = getline(&line, &linecap, fp)) != -1) {

        // strip \r and \n
        while (linelen > 0 && (line[linelen - 1] == '\n' || line[linelen - 1] == '\r'))
            linelen--;

        editor_insert_row(E.numrows, line, linelen);
    }

    free(line);
    fclose(fp);
    E.dirty = 0;
}

void editor_save() {
    if (E.filename == NULL) {
        E.filename = editor_prompt("Save as: %s", NULL);
        if (E.filename == NULL) {
            editor_set_status_message("Save aborted");
            return;
        }
        editor_select_syntax_highlight();
    }

    int len;
    char* buf = editor_rows_to_string(&len);

    // 0644 is file perms, user read/write, group read
    int fd = open(E.filename, O_RDWR | O_CREAT, 0644);

    if (fd != -1) {
        // will cut off excess, or add 0 until file is of length len
        // by using ftruncate and not the O_TRUNC flag for open() (which automatically clears the file)
        // we keep the old file if the write fails, but the open doesn't
        // If we were cooler, we'd write to another file, and only if everything is good, rename it
        if (ftruncate(fd, len) != 1) {
            if (write(fd, buf, len) == len) {
                close(fd);
                free(buf);
                E.dirty = 0;
                editor_set_status_message("%d bytes written to disk", len);
                return;
            }
        }
        close(fd);
    }
    free(buf);
    editor_set_status_message("Can't save! I/O error: %s", strerror(errno));
}

/*** find ***/

void editor_find_callback(char* query, int key) {
    static int last_match = -1;
    static int direction = 1;

    static int saved_hl_line;
    static char* saved_hl = NULL;

    if (saved_hl) {
        memcpy(E.row[saved_hl_line].hl, saved_hl, E.row[saved_hl_line].rsize);
        free(saved_hl);
        saved_hl = NULL;
    }

    if (key == '\r' || key == '\x1b') {
        last_match = -1;
        direction = 1;
        return;
    } else if (key == ARROW_RIGHT || key == ARROW_DOWN) {
        direction = 1;
    } else if (key == ARROW_LEFT || key == ARROW_UP) {
        direction = -1;
    } else {
        last_match = -1;
        direction = 1;
    }

    if (last_match == -1)
        direction = 1;
    int current = last_match;

    int i;
    for (i = 0; i < E.numrows; i++) {
        // start from last match and wrap around
        current += direction;
        if (current == -1)
            current = E.numrows - 1;
        else if (current == E.numrows) 
            current = 0;

        Row* row = &E.row[current];
        char* match = strstr(row->render, query);
        if (match) {
            last_match = current;
            E.cy = current;
            E.cx = editor_row_rx_to_cx(row, match - row->render);
            E.rowoff = E.numrows;

            saved_hl_line = current;
            saved_hl = malloc(row->rsize);
            memcpy(saved_hl, row->hl, row->rsize);
            memset(&row->hl[match - row->render], HL_MATCH, strlen(query));
            break;
        }
    }
}

void editor_find() {
    int saved_cx = E.cx;
    int saved_cy = E.cy;
    int saved_coloff = E.coloff;
    int saved_rowoff = E.rowoff;
    char* query = editor_prompt("Search: %s", editor_find_callback);

    if (query) {
        free(query);
    } else {
        E.cx = saved_cx;
        E.cy = saved_cy;
        E.coloff = saved_coloff;
        E.rowoff = saved_rowoff;
    }
}

/*** append buffer ***/

// Avoid many small calls to write
typedef struct {
    char *b;
    int len;
} AppendBuf;

#define ABUF_INIT {NULL, 0}

void ab_append(AppendBuf *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(AppendBuf *ab) {
    free(ab->b);
}

/*** input ***/

// callback function called after every keypress
char* editor_prompt(char* prompt, void (*callback)(char*, int)) {
    size_t bufsize = 128;
    char* buf = malloc(bufsize);

    size_t buflen = 0;
    buf[0] = '\0';

    for (;;) {
        editor_set_status_message(prompt, buf);
        editor_refresh_screen();

        int c = editor_read_key();
        if (c == DEL_KEY || c == CTRL_KEY('h') || c == BACKSPACE) {
            if (buflen != 0)
                buf[--buflen] = '\0';
        } else if (c == '\x1b') {
            // escape
            editor_set_status_message("");
            if (callback)
                callback(buf, c);
            free(buf);
            return NULL;
        } else if (c == '\r') {
            if (buflen != 0) {
                editor_set_status_message("");
                if (callback)
                    callback(buf, c);
                return buf;
            }
        } else if (!iscntrl(c) && c < 128) {
            if (buflen == bufsize - 1) {
                bufsize *= 2;
                buf = realloc(buf, bufsize);
            }
            buf[buflen++] = c;
            buf[buflen] = '\0';
        }

        if (callback)
            callback(buf, c);
    }
}

void editor_move_cursor(int key) {
    Row *row = (E.cy >= E.numrows) ? NULL : &E.row[E.cy];

    switch (key) {
        case ARROW_LEFT:
            if (E.cx != 0) {
                E.cx--;
            } else if (E.cy > 0) {
                E.cy--;
                E.cx = E.row[E.cy].size;
            }
            break;
        case ARROW_RIGHT:
            if (row && E.cx < row->size) {
                E.cx++;
            } else if (row && E.cx == row->size) {
                E.cy++;
                E.cx = 0;
            }
            break;
        case ARROW_UP:
            if (E.cy != 0) {
                E.cy--;
            }
            break;
        case ARROW_DOWN:
            if (E.cy < E.numrows) {
                E.cy++;
            }
            break;
    }

    // Correct row if we moved down/up to a row that was shorter
    row = (E.cy >= E.numrows) ? NULL : &E.row[E.cy];
    int rowlen = row ? row->size : 0;
    if (E.cx > rowlen) {
        E.cx = rowlen;
    }
}

void editor_process_keypress() {
    static int quit_times = PICO_QUIT_TIMES;

    int c = editor_read_key();
    switch (c) {
        case '\r':
            editor_insert_newline();
            break;

        case CTRL_KEY('q'):
            if (E.dirty && quit_times > 0) {
                editor_set_status_message("WARNING!!! File has unsaved changes. "
                        "Press Ctrl-Q %d more times to quit.", quit_times);
                quit_times--;
                // We return so that the quit number reset at the end of the function
                // doesn't happen
                return;
            }

            // Clear screen
            write(STDOUT_FILENO, "\x1b[2J", 4);
            write(STDOUT_FILENO, "\x1b[H", 3);
            // exit
            exit(0);
            break;

        case CTRL_KEY('s'):
            editor_save();
            break;

        case HOME_KEY:
            E.cx = 0;
            break;
        case END_KEY:
            if (E.cy < E.numrows)
                E.cx = E.row[E.cy].size;
            break;

        case CTRL_KEY('f'):
            editor_find();
            break;

        case BACKSPACE:
        case CTRL_KEY('h'):
        case DEL_KEY:
            if (c == DEL_KEY)
                editor_move_cursor(ARROW_RIGHT);
            editor_del_char();
            break;

        case PAGE_UP:
        case PAGE_DOWN:
            // Create code block so that we can delcare a variable
            {
                if (c == PAGE_UP) {
                    E.cy = E.rowoff;
                } else if (c == PAGE_DOWN) {
                    E.cy = E.rowoff + E.screenrows - 1;
                    if (E.cy > E.numrows) E.cy = E.numrows;
                }

                int times = E.screenrows;
                while (times--)
                    editor_move_cursor(c == PAGE_UP ? ARROW_UP : ARROW_DOWN);
            }
            break;

        case ARROW_LEFT:
        case ARROW_RIGHT:
        case ARROW_UP:
        case ARROW_DOWN:
            editor_move_cursor(c);
            break;

        case CTRL_KEY('l'):
        case '\x1b':
            break;

        default:
            editor_insert_char(c);
            break;
    }

    quit_times = PICO_QUIT_TIMES;
}

/*** output ***/

void editor_scroll() {
    E.rx = 0;
    if (E.cy < E.numrows) {
        E.rx = editor_row_cx_to_rx(&E.row[E.cy], E.cx);
    }

    if (E.cy < E.rowoff) {
        E.rowoff = E.cy;
    }
    if (E.cy >= E.rowoff + E.screenrows) {
        E.rowoff = E.cy - E.screenrows + 1;
    }
    if (E.rx < E.coloff) {
        E.coloff = E.rx;
    }
    if (E.rx >= E.coloff + E.screencols) {
        E.coloff = E.rx - E.screencols + 1;
    }
}

void editor_draw_rows(AppendBuf *ab) {
    int y;
    for (y = 0; y < E.screenrows; y++) {
        int filerow = y + E.rowoff;
        // I think the tutorial as `>=` here but it drew an extra tilde for me and now it just
        // has a blank line for appending a line to the file which is much better.
        // Is this undefined behavior or correct code ?!?!
        // It was UB...     the bug is still here... Only crashes with no file input
        if (filerow >= E.numrows) {
            if (E.numrows == 0 && filerow == E.screenrows / 3) {
                // Create welcome message
                char welcome[80];
                int welcomelen = snprintf(welcome, sizeof(welcome), "Pico editor -- version %s", PICO_VERSION);
                if (welcomelen > E.screencols) welcomelen = E.screencols;

                // Add padding
                int padding = (E.screencols - welcomelen) / 2;
                if (padding) {
                    ab_append(ab, "~", 1);
                    padding--;
                }
                while (padding--)
                    ab_append(ab, " ", 1);

                ab_append(ab, welcome, welcomelen);

            // THIS SEEMED TO FIX IT!!!!!
            // used to just be else
            } else if (E.numrows == 0 || filerow == E.screenrows) {
                ab_append(ab, "~", 1);
            }
        } else {
            // Otherwise print the text at the yth row
            int len = E.row[filerow].rsize - E.coloff;
            if (len < 0) 
                len = 0;
            if (len > E.screencols) 
                len = E.screencols;

            char* c = &E.row[filerow].render[E.coloff];
            unsigned char* hl = &E.row[filerow].hl[E.coloff];
            // -1 indicates the default color
            int current_color = -1;

            int j;
            for (j = 0; j < len; j++) {
                if (iscntrl(c[j])) {
                    // Non-printable characters
                    // Capital letters come after the '@' character
                    char sym = (c[j] <= 26) ? '@' + c[j] : '?';
                    // invert colors for printing
                    ab_append(ab, "\x1b[7m", 4);
                    ab_append(ab, &sym, 1);
                    ab_append(ab, "\x1b[m", 3);
                    if (current_color != -1) {
                        char buf[16];
                        int clen = snprintf(buf, sizeof(buf), "\x1b[%dm", current_color);
                        ab_append(ab, buf, clen);
                    }
                } else if (hl[j] == HL_NORMAL) {
                    if (current_color != -1) {
                        ab_append(ab, "\x1b[39m", 5);
                        current_color = -1;
                    }
                    ab_append(ab, &c[j], 1);
                } else {
                    int color = editor_syntax_to_color(hl[j]);
                    if (color != current_color) {
                        current_color = color;
                        char buf[16];
                        int clen = snprintf(buf, sizeof(buf), "\x1b[%dm", color);
                        ab_append(ab, buf, clen);
                    }
                    ab_append(ab, &c[j], 1);
                }
            }
            ab_append(ab, "\x1b[39m", 5);
        }

        ab_append(ab, "\x1b[K", 3);
        ab_append(ab, "\r\n", 2);
    }
}

void editor_draw_status_bar(AppendBuf *ab) {
    // inverted colors
    ab_append(ab, "\x1b[7m", 4);

    char status[80], rstatus[80];
    int len = snprintf(status, sizeof(status), "%.20s - %d lines %s", 
        E.filename ? E.filename : "[No Name]", 
        E.numrows,
        E.dirty ? "(modified)" : "");
    int rlen = snprintf(rstatus, sizeof(rstatus), "%s | %d/%d", 
            E.syntax ? E.syntax->filetype : "no ft",
            E.cy + 1, 
            E.numrows);

    if (len > E.screencols) len = E.screencols;

    ab_append(ab, status, len);

    // Fill with spaces until right aligned line numbers
    while (len < E.screencols) {
        if (E.screencols - len == rlen) {
            ab_append(ab, rstatus, rlen);
            break;
        } else {
            ab_append(ab, " ", 1);
            len++;
        }
    }

    // normal text formatting
    ab_append(ab, "\x1b[m", 3);
    ab_append(ab, "\r\n", 2);
}

void editor_draw_message_bar(AppendBuf *ab) {
    ab_append(ab, "\x1b[K", 3);
    int msglen = strlen(E.statusmsg);
    if (msglen > E.screencols) msglen = E.screencols;
    if (msglen && time(NULL) - E.statusmsg_time < 5)
        ab_append(ab, E.statusmsg, msglen);
}

void editor_refresh_screen() {
    editor_scroll();

    AppendBuf ab = ABUF_INIT;

    // Hide the cursor
    ab_append(&ab, "\x1b[?25l", 6);

    // 0x1b is 27 in hexidecimal which is the escape character
    // the other three bytes are "[2j"
    // Escape sequences start with an escape character (\x1b)
    // and then '['. They instruct the terminal to do various things.
    // 'J' is erase and '2' means to erase the entire screen (0 is default argument).
    // `ab_append(&ab, "\x1b[2J", 4);`

    // The 3 means write four bytes
    // 'H' is the cursor position command.
    // takes 2 arguments we could use "\x1b[12;40H" to move the curosr to the 12th row and 40th col
    // multiple arguments are separated by a ';'. Default arguments are 1 and 1.
    ab_append(&ab, "\x1b[H", 3);

    editor_draw_rows(&ab);
    editor_draw_status_bar(&ab);
    editor_draw_message_bar(&ab);

    // move cursor
    char buf[32];
    snprintf(buf, sizeof(buf), "\x1b[%d;%dH", (E.cy - E.rowoff) + 1, (E.rx - E.coloff) + 1);
    ab_append(&ab, buf, strlen(buf));

    // Show the cursor
    ab_append(&ab, "\x1b[?25h", 6);

    write(STDOUT_FILENO, ab.b, ab.len);
    abFree(&ab);
}

// This is how you do variable arguments in C, this is now a "variadic function"
// All the cool va shit comes from <stdarg.h>
// printf comes from <stdio.h> and time, obviously <time.h>
void editor_set_status_message(const char *fmt, ...) {
    va_list ap;
    va_start(ap, fmt);
    vsnprintf(E.statusmsg, sizeof(E.statusmsg), fmt, ap);
    va_end(ap);
    E.statusmsg_time = time(NULL);
}

/*** init ***/

void editor_init() {
    E.cx = 0;
    E.cy = 0;
    E.rx = 0;
    E.rowoff = 0;
    E.coloff = 0;
    E.numrows = 0;
    E.row = NULL;
    E.dirty = 0;
    E.filename = NULL;
    E.statusmsg[0] = '\0';
    E.statusmsg_time = 0;
    E.syntax = NULL;

    if (get_window_size(&E.screenrows, &E.screencols) == -1)
        die("get_window_size");

    E.screenrows -= 2;
}

int main(int arc, char *argv[]) {
    enable_raw_mode();
    editor_init();
    if (arc >= 2) {
        editor_open(argv[1]);
    }

    editor_set_status_message("HELP: Ctrl-S to save | Ctrl-Q to quit | Ctrl-F to find");

    for (;;) {
        editor_refresh_screen();
        editor_process_keypress();
    }

    return 0;
}