From 2f249f6be2e49e57fd59ecd50f73e6a734c6bbb4 Mon Sep 17 00:00:00 2001
From: Johnny Richard <johnny@johnnyrichard.com>
Date: Mon, 25 Apr 2022 03:37:55 +0200
Subject: Enable terminal raw mode and draw editor

---
 .gitignore |   1 +
 ted.c      | 190 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 190 insertions(+), 1 deletion(-)

diff --git a/.gitignore b/.gitignore
index 8830688..8490248 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,2 @@
 ted
+tags
diff --git a/ted.c b/ted.c
index 90f1213..a01ac7e 100644
--- a/ted.c
+++ b/ted.c
@@ -15,9 +15,197 @@
  * You should have received a copy of the GNU General Public License
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
+#include <ctype.h>
+#include <errno.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
 #include <stdlib.h>
+#include <sys/ioctl.h>
+#include <termios.h>
+#include <unistd.h>
 
-int main()
+#define CTRL_KEY(k) ((k) & 0x1F)
+
+typedef struct editor_config {
+  int screen_rows;
+  int screen_cols;
+  struct termios orig_termios;
+} editor_config_t;
+
+editor_config_t E;
+
+
+void editor_init(editor_config_t *ec);
+char editor_read_key();
+int get_cursor_position(int *rows, int *cols);
+int get_window_size(int *rows, int *cols);
+void editor_process_key();
+void editor_draw_rows(editor_config_t *ec);
+void editor_clear_screen();
+void editor_refresh_screen(editor_config_t *ec);
+void disable_raw_mode();
+void enable_raw_mode();
+void die(const char *s);
+
+int
+main()
 {
+  enable_raw_mode();
+
+  editor_init(&E);
+
+  while (true) {
+    editor_refresh_screen(&E);
+    editor_process_key();
+  }
+
   return EXIT_SUCCESS;
 }
+
+void
+editor_init(editor_config_t *ec)
+{
+  if (get_window_size(&ec->screen_rows, &ec->screen_rows) == -1) {
+    die("get_window_size");
+  }
+}
+
+char
+editor_read_key()
+{
+  int nread;
+  char c;
+  while ((nread = read(STDIN_FILENO, &c, 1)) != 1) {
+    if (nread == -1 && errno != EAGAIN) {
+      die("read");
+    }
+  }
+  return c;
+}
+
+int
+get_cursor_position(int *rows, int *cols)
+{
+  char buf[32];
+  uint32_t i = 0;
+
+  if (write(STDIN_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
+get_window_size(int *rows, int *cols)
+{
+  struct winsize ws;
+
+  if (ioctl(STDIN_FILENO, TIOCGWINSZ, &ws) == -1 || ws.ws_col == 0) {
+    if (write(STDIN_FILENO, "\x1b[999C\x1b[999B", 12) != 12) {
+      return -1;
+    }
+    return get_cursor_position(rows, cols);
+  }
+
+  *cols = ws.ws_col;
+  *rows = ws.ws_row;
+  return 0;
+}
+
+void
+editor_process_key()
+{
+  char c = editor_read_key();
+
+  switch (c) {
+    case CTRL_KEY('q'):
+      editor_clear_screen();
+      exit(EXIT_SUCCESS);
+      break;
+  }
+}
+
+void
+editor_clear_screen()
+{
+  write(STDOUT_FILENO, "\x1b[2J", 4);
+  write(STDOUT_FILENO, "\x1b[H", 3);
+}
+
+void
+editor_draw_rows(editor_config_t *ec)
+{
+  for (int y = 0; y < ec->screen_rows; ++y) {
+    write(STDOUT_FILENO, "~", 1);
+
+    if (y < ec->screen_rows - 1) {
+      write(STDOUT_FILENO, "\r\n", 2);
+    }
+  }
+}
+
+void
+editor_refresh_screen(editor_config_t *ec)
+{
+  editor_clear_screen();
+  editor_draw_rows(ec);
+  write(STDOUT_FILENO, "\x1b[H", 3);
+}
+
+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;
+  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");
+  }
+}
+
+void
+die(const char *s)
+{
+  editor_clear_screen();
+  perror(s);
+  exit(EXIT_FAILURE);
+}
-- 
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