From d4a5b16f6d1920b0670fda7cd36380525292c20b Mon Sep 17 00:00:00 2001
From: Benjamyn Love <benjamyn.love@gmail.com>
Date: Tue, 6 Feb 2024 14:18:40 +1100
Subject: [PATCH] Step 40

---
 kilo.c | 147 ++++++++++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 134 insertions(+), 13 deletions(-)

diff --git a/kilo.c b/kilo.c
index 174f8db..ecfd560 100644
--- a/kilo.c
+++ b/kilo.c
@@ -4,30 +4,45 @@
 #include <errno.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
+#include <sys/ioctl.h>
 #include <unistd.h>
 #include <termios.h>
 
+/*** defines ***/
+
+#define CTRL_KEY(k) ((k) & 0x1f)
+
 /*** data ***/
 
-struct termios orig_termios;
+struct editorConfig {
+  int screenrows;
+  int screencols;
+  struct termios orig_termios;
+};
+
+struct editorConfig E;
 
 /*** terminal ***/
 
 void die(const char *s) {
+  write(STDOUT_FILENO, "\x1b[2J", 4);
+  write(STDOUT_FILENO, "\x1b[H", 3);
+
   perror(s);
   exit(1);
 }
 
 void disableRawMode() {
-  if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &orig_termios) == 1)
+  if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &E.orig_termios) == 1)
     die("tcsetattr");
 }
 
 void enableRawMode() {
-  if (tcgetattr(STDIN_FILENO, &orig_termios) == -1) die("tcgetattr");
+  if (tcgetattr(STDIN_FILENO, &E.orig_termios) == -1) die("tcgetattr");
   atexit(disableRawMode);
 
-  struct termios raw = orig_termios;
+  struct termios raw = E.orig_termios;
 
   raw.c_iflag &= ~(IXON | ICRNL | INPCK | ISTRIP | BRKINT);
   raw.c_oflag &= ~(OPOST);
@@ -39,21 +54,127 @@ void enableRawMode() {
   if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &raw) == -1) die("tcsetattr");
 }
 
+char editorReadKey() {
+  int nread;
+  char c;
+  while ((nread = read(STDIN_FILENO, &c, 1)) != 1) {
+    if (nread == -1 && errno != EAGAIN) die("read");
+  }
+  return c;
+}
+
+int getCursorPosition(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++;
+  }
+  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 (1 || ioctl(STDOUT_FILENO, TIOCGWINSZ, &ws) == -1 || ws.ws_col == 0) {
+    if (write(STDOUT_FILENO, "\x1b[999C\x1b[999B", 12) != 12) return -1;
+//    editorReadKey();
+    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++) {
+    abAppend(ab, "~", 1);
+
+    if (y < E.screenrows - 1) {
+      abAppend(ab, "\r\n", 2);
+    }
+  }
+}
+
+void editorRefreshScreen() {
+  struct abuf ab = ABUF_INIT;
+
+  abAppend(&ab, "\x1b[?25l", 6);
+  abAppend(&ab, "\x1b[2J", 4);
+  abAppend(&ab, "\x1b[H" , 3);
+  
+  editorDrawRows(&ab);
+
+  abAppend(&ab, "\x1b[H", 3);
+  abAppend(&ab, "\x1b[?25h", 6);
+  write(STDOUT_FILENO, ab.b, ab.len);
+  abFree(&ab);
+}
+
+
+/*** input ***/
+
+void editorProcessKeypress() {
+  char c = editorReadKey();
+
+  switch (c) {
+    case CTRL_KEY('q'):
+      write(STDOUT_FILENO, "\x1b[2J", 4);
+      write(STDOUT_FILENO, "\x1b[H", 3);
+
+      exit(0);
+      break;
+  }
+}
+
 /*** init ***/
 
+void initEditor() {
+  if (getWindowSize(&E.screenrows, &E.screencols) == -1) die("getWindowSize");
+}
+
 int main() {
   enableRawMode();
+  initEditor();
 
   while (1) {
-    char c = '\0';
-    if (read(STDIN_FILENO, &c, 1) == -1 && errno != EAGAIN) die("read");
-
-    if (iscntrl(c)) {
-      printf("%d\r\n", c);
-    } else {
-      printf("%d ('%c')\r\n", c, c);
-    }
-    if (c == 'q') break;
+    editorRefreshScreen();
+    editorProcessKeypress();
   }
 
   return 0;