From 168a11906481f459af6d0e9ae07cdc3a3bdc45bb Mon Sep 17 00:00:00 2001
From: Aaron Fischer <aaron.fischer@marbis.net>
Date: Mon, 17 Sep 2018 13:27:19 +0200
Subject: [PATCH] Finish second part. Keys are recognized

---
 kilo.c | 138 ++++++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 133 insertions(+), 5 deletions(-)

diff --git a/kilo.c b/kilo.c
index 35a492e..28e9175 100644
--- a/kilo.c
+++ b/kilo.c
@@ -10,11 +10,28 @@
 #include <unistd.h>
 
 /*** defines ***/
+
+#define KILO_VERSION "0.0.1"
+
 #define CTRL_KEY(k) ((k) & 0x1f)
 
+enum editorKey {
+  ARROW_LEFT = 1000,
+  ARROW_RIGHT,
+  ARROW_UP,
+  ARROW_DOWN,
+  DEL_KEY,
+  HOME_KEY,
+  END_KEY,
+  PAGE_UP,
+  PAGE_DOWN
+};
+
+
 /*** data ***/
 
 struct editorConfig {
+  int cx, cy;
   int screenrows;
   int screencols;
   struct termios orig_termios;
@@ -53,13 +70,53 @@ void enableRawMode() {
     die("tcsetattr");
 }
 
-char editorReadKey() {
+int editorReadKey() {
   int nread;
   char c;
   while ((nread = read(STDIN_FILENO, &c, 1)) != 1) {
     if (nread == -1 && errno != EAGAIN) die("read");
   }
-  return c;
+
+  // Process escape sequences
+  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;
+        }
+      }
+    } else if (seq[0] == '0') {
+      switch (seq[1]) {
+        case 'H': return HOME_KEY;
+        case 'F': return END_KEY;
+      }
+    }
+
+    return '\x1b';
+  } else {
+    return c;
+  }
 }
 
 int getCursorPosition(int *rows, int *cols) {
@@ -122,7 +179,21 @@ void abFree(struct abuf *ab) {
 void editorDrawRows(struct abuf *ab) {
   int y;
   for (y = 0; y < E.screenrows; y++) {
-    abAppend(ab, "~", 1);
+    if (y == E.screenrows / 3) {
+      char welcome[80];
+      int welcomelen = snprintf(welcome, sizeof(welcome),
+          "Kilo editor -- version %s", KILO_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); // Erase one line
     if (y < E.screenrows - 1) {
@@ -139,7 +210,11 @@ void editorRefreshScreen() {
 
   editorDrawRows(&ab);
 
-  abAppend(&ab, "\x1b[H", 3);
+  // Update cursor position
+  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);
@@ -148,8 +223,34 @@ void editorRefreshScreen() {
 
 /*** 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() {
-  char c = editorReadKey(); // Blocking!
+  int c = editorReadKey(); // Blocking!
 
   switch (c) {
     case CTRL_KEY('q'):
@@ -157,12 +258,39 @@ void editorProcessKeypress() {
       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");
 }