Added check to prevent page down from looping endlessly

.gitignore

@@ -0,0 +1,2 @@
+editor
+editor.o

Makefile

@@ -0,0 +1,23 @@
+EXEC_FILE=editor
+CFLAGS=
+
+all: $(EXEC_FILE)
+
+$(EXEC_FILE): $(EXEC_FILE).o
+	gcc $(CFLAGS) -o $@ $^ -lncurses
+
+$(EXEC_FILE).o: $(EXEC_FILE).c
+	gcc $(CFLAGS) -c -o $@ $^
+
+.PHONY: debug
+debug: CFLAGS+=-g
+debug: $(EXEC_FILE)
+
+.PHONY: allwarn
+allwarn: CFLAGS+=-Wall -Wextra -pedantic
+allwarn: $(EXEC_FILE)
+
+.PHONY: clean
+clean:
+	rm $(EXEC_FILE)
+	rm $(EXEC_FILE).o

editor.c

@@ -4,6 +4,14 @@
 #include <signal.h>
 #include <string.h>
 #include <stdbool.h>
+#include <unistd.h>
+#include <sys/stat.h>
+
+#define ctrl(x) ((x) & 0x1f)
+
+int index_to_start = 0;
+WINDOW* mainwin;
+WINDOW* statusbar;
 
 typedef struct Buffer_struct Buffer;
 struct Buffer_struct {
@@ -27,14 +35,17 @@ Buffer* new_buffer(int size) {
 
 void buffer_grow(Buffer* buffer) {
 
-	int old_size = buffer->size;
+	int old_size = buffer->size;  /* I am making use of the fact that, whenever this 
+					function is called, the strlen of the string must 
+					equal the size of the buffer (since the gap size is zero) */
+
 	int start_offset = buffer->start - buffer->text;
 	buffer->size += 10;
 	buffer->text = realloc(buffer->text,buffer->size);
 	buffer->start = buffer->text + start_offset;
 
 	buffer->gap_size = 10;
-	for (int i=0; i < (old_size - start_offset); i++) {
+	for (int i= (old_size - start_offset) - 1; i >= 0; i--) {
 		*(buffer->start + i + buffer->gap_size) = *(buffer->start + i);
 		*(buffer->start + i) = 0;
 	}
@@ -52,13 +63,20 @@ void buffer_insert(char ch, Buffer* buffer) {
 	}
 }
 
-void buffer_delete(Buffer* buffer) {
+void buffer_delete_front(Buffer* buffer) {
 	if (buffer->start != buffer->text) {
 		buffer->start--;
 		buffer->gap_size++;
 	}
 }
 
+void buffer_delete_back(Buffer* buffer) {
+	if (buffer->end != buffer->text + buffer->size) {
+		buffer->end++;
+		buffer->gap_size++;
+	}
+}
+
 void buffer_right(Buffer* buffer) {
 	if (buffer->end != buffer->text + buffer->size) {
 		char c = *(buffer->end);
@@ -68,6 +86,12 @@ void buffer_right(Buffer* buffer) {
 	}
 }
 
+void right_key_handler(Buffer* buffer) {
+	if ((*(buffer->end) != '\n') || (getcury(mainwin) + 1 < getmaxy(mainwin))) {
+		buffer_right(buffer);
+	}
+}
+
 void buffer_left(Buffer* buffer) {
 	if (buffer->start != buffer->text) {
 		char c = *(buffer->start - 1);
@@ -78,70 +102,242 @@ void buffer_left(Buffer* buffer) {
 	}
 }
 
-void init_curses() {
-	initscr();
-	noecho();
-	keypad(stdscr,TRUE);
-	cbreak();
+void left_key_handler(Buffer* buffer) {
+	if ((getcurx(mainwin) > 0) || (getcury(mainwin) > 0)) {
+		buffer_left(buffer);
+	}
 }
 
-void sigint_handler(int dummy) {
+void scroll_page_down_handler(Buffer* buffer) {
+	while (*(buffer->text + index_to_start) != '\n') {
+		index_to_start++;
+	}
+	index_to_start++;
+}
+
+void page_down_handler(Buffer* buffer) {
+	if ((getcury(mainwin) + 1) == getmaxy(mainwin)) {
+		scroll_page_down_handler(buffer);
+	}
+
+	buffer_right(buffer); /* I must advance the cursor at least 
+				once, so this hardcoded statement is fine. */
+
+
+	while ((*(buffer->start - 1) != '\n') && (buffer->end != (buffer->text + buffer->size))) {
+		buffer_right(buffer);
+	}
+
+	/* You would think that I need to call 'buffer_right' once 
+	more, to advance the cursor onto the next line.	In fact, if 
+	you think about it, the place where the cursor (the rectangle) 
+	is, is actually the character _after_ the gap. Therefore, by 
+	advancing the start to the newline character, the character 
+	after the gap (i.e. the cursor)	will automatically be moved to 
+	the next line. */
+
+}
+
+
+void scroll_page_up_handler(Buffer* buffer) {
+	for (int i=0;i<2;i++) { /* we need to encounter two 'newlines' before we stop */
+		while((*(buffer->text + index_to_start) != '\n') && (index_to_start >= 0)) {
+			index_to_start--;
+		}
+	}
+
+	index_to_start++;
+}
+
+void page_up_handler(Buffer* buffer) {
+	while((*(buffer->start - 1) != '\n') && (buffer->text != buffer->start)) { 
+			buffer_left(buffer);
+	}
+
+
+	buffer_left(buffer);
+
+	while((*(buffer->start - 1) != '\n') && (buffer->text != buffer->start)) {
+			buffer_left(buffer);
+	}
+
+
+	if ((getcury(mainwin) == 0) && (index_to_start > 0)) {
+		scroll_page_up_handler(buffer);
+	}
+
+}
+
+void keypress_handler(char key, Buffer* buffer) {
+	buffer_insert(key,buffer);
+	if ((getcury(mainwin) + 1) == getmaxy(mainwin)) {
+		scroll_page_down_handler(buffer);
+	}
+}
+
+int is_file(char* path) {
+	struct stat st;
+	if (stat(path, &st) < 0) {
+		return -1;
+	}
+	return S_ISREG(st.st_mode);
+}
+
+void save_text_helper(Buffer* buffer,char* filename) {
+	FILE* file = fopen(filename,"w");
+	int i = 0;
+	while (i < buffer->size) {
+		if ((buffer->start - buffer->text) == i) {  /* If we have encountered
+								the start of the gap */
+			i += buffer->gap_size;
+		}
+
+		if (i >= buffer->size) {
+			break;
+		}
+		fputc(*(buffer->text + i),file);
+		i++;
+	}
+}
+
+void init_curses() {
+	initscr();
+	mainwin = newwin(getmaxy(stdscr)-1,getmaxx(stdscr),0,0);
+
+	statusbar = newwin(1,getmaxx(stdscr),getmaxy(stdscr)-1,0);
+	wattrset(statusbar,A_REVERSE);
+	mvwhline(statusbar,0,0,' ',getmaxx(statusbar));
+	mvwprintw(statusbar,0,0,"Welcome to Editor!");
+	wrefresh(statusbar);
+
+	noecho();
+	keypad(stdscr,TRUE);
+	keypad(mainwin,TRUE);
+	raw();
+}
+
+void end_ncurses() {
 	endwin();
 	exit(130);
 }
 
-int main() {
-	signal(SIGINT,sigint_handler);
+int main(int argc, char** argv) {
 
 	Buffer* buffer = new_buffer(10);
+	FILE* logfile = fopen("logfile.txt","w");
+
+	if (argc == 2) {
+		int num_of_chars = 0;
+		if (access(argv[1],F_OK) == 0) {  /* If the file exists */
+			FILE* file = fopen(argv[1],"r");
+			char c;
+			while ((c = fgetc(file)) != EOF) {
+				buffer_insert(c,buffer);
+				num_of_chars++;
+			}
+	
+			while (num_of_chars > 0) {
+				buffer_left(buffer);
+				num_of_chars--;
+			}
+		}
+	}
+
 	init_curses();
 	int ch;
 
 	int y, x;
 	while (true) {
-		clear();
+		wclear(mainwin);
 
-		int i=0;
-		if (buffer->start != buffer->text) {  /* We don't want to print the string, if the 
-							gap starts at the first index of the string */
+		int i=index_to_start;
+		if ((buffer->start != buffer->text) || (buffer->gap_size != buffer->size)) {  /* We don't want to print the string, if the 
+							gap starts at the first index of the string, and continues till the end */
 
 	                while (i < buffer->size) {
-	                        addch(*(buffer->text + i));
-				i++;
 	                        if ((buffer->start - buffer->text) == i) {  /* If we have encountered 
 										the start of the gap */
-					getyx(stdscr,y,x);
+					getyx(mainwin,y,x);
 	                                i += buffer->gap_size;
 				}
+				if (i >= buffer->size) {
+					break;
+				}
+
+				fprintf(logfile,"At line %d of %d\n",getcury(mainwin),getmaxy(mainwin));
+				if (*(buffer->text + i) == '\n' && ((getcury(mainwin) + 1) == getmaxy(mainwin))) {
+					fprintf(logfile,"Read newline\n");
+					break;
+				}
+
+	                        waddch(mainwin,*(buffer->text + i));
+				i++;
+
 	                }
 
-			move(y,x);
+			wmove(mainwin,y,x);
+
+			wrefresh(mainwin);
 
 		}
 
 
-		ch = getch();
+		ch = wgetch(mainwin);
 
 		switch(ch) {
 			case KEY_BACKSPACE:
-				buffer_delete(buffer);
+				buffer_delete_front(buffer);
+				break;
+
+			case KEY_DC:
+				buffer_delete_back(buffer);
 				break;
 
 			case KEY_LEFT:
-				buffer_left(buffer);
+				left_key_handler(buffer);
 				break;
 
 			case KEY_RIGHT:
-				buffer_right(buffer);
+				right_key_handler(buffer);
+				break;
+
+			case 10:  /* Enter key */
+				keypress_handler('\n',buffer);  /* Why handle this separately? 
+								Because, by default, curses seems to send '\r\n', 
+								which is technically two characters. I should 
+								probably add some code to deal with this scenario 
+								in the 'insert' method (instead of creating an 
+								exception here), but that's a problem for another day. */
+				break;
+
+			case KEY_NPAGE:
+				page_down_handler(buffer);
+				break;
+
+			case KEY_PPAGE:
+				page_up_handler(buffer);
+				break;
+
+			case ctrl(KEY_NPAGE):
+				abort();
+
+			case ctrl('s'):
+				if (argc == 2) {
+					save_text_helper(buffer,argv[1]);
+				} else if (argc == 1) {
+					save_text_helper(buffer,NULL);
+				}
+				break;
+
+			case ctrl('c'):
+				end_ncurses();
 				break;
 
 			default:
-				buffer_insert(ch,buffer);
+				keypress_handler(ch,buffer);
 
 		}
 
-		continue_while_loop:
-
 	}
 	endwin();
 }