/* quark.c
 * A simple, line-oriented text editor
 * Written by Feky, 2008 */
 
 #include <stdio.h>
 #include <stdlib.h>
 #include <stdbool.h>
 #include <string.h>
 #include <ctype.h>
 
 #define VERSION "quark 0.2"
 #define LINE_LEN 255
 
 typedef struct _list {
	 struct _list *next;
	 struct _list *prev;
	 char line[LINE_LEN];
 } LIST;
 typedef unsigned int uint;
 
 void help (char *); /* show help */
 bool insert (void); /* insert a new node into the list */
 bool erase (void); /* delete a node */
 bool save (char *); /* save the buffer to a file */
 void printall (uint); /* see 'p*' in help */
 
 LIST list;
 LIST *head, *curr;
 
 void help (char *argv) {
    printf("%s\nUsage: %s [FILE]\n\n", VERSION, argv);
    puts("Command\tMeaning\n"
	    "p\tPrint the current line.\n"
	    "\t\'p*\' prints all lines until EOF is reached.");
    puts(">\tOverwrite the current line with some text.");
    puts("n\tInsert a new, blank line after the current.");
    puts("d\tDelete the current line.");
    puts("+\tGo forward for a number of lines.");
    puts("-\tGo backwards for a number of lines.");
    puts("s\tSave changes to file.");
    puts("q\tExit the program.");
}	 
 
 bool insert (void) {
	LIST *node;
	 
	node = calloc(1, sizeof(LIST));
	
	if(node != NULL) {
		node->next = curr->next;
		node->prev = curr;
		if(curr->next != NULL)
			curr->next->prev = node;
		curr->next = node;
		curr = curr->next;
		return false;
	}
	/* not enough memory for a new node */
	return true;
}

 bool erase (void) {
	 LIST *node;
	 
	 node = curr->prev;
	 
	 if(node == head) /* we're at the first node */
		 node = curr->next;
	 if(node == NULL) /* there's nothing to delete anymore */
		 return true;
	 
	 if(curr->next != NULL) /* if it's not the last node */
		 curr->next->prev = curr->prev;
	 curr->prev->next = curr->next;
	 
	 free(curr);
	 
	 curr = node;
	 return false;
 }
 
 bool save (char *fn) {
	 LIST *node;
	 FILE *pf;
	 
	 pf = fopen(fn, "w");
	 
	 if(pf == NULL)
		 return true;
	 
	 node = curr;
	 curr = head->next;
	 while(curr != NULL) {
		 fprintf(pf, "%s", curr->line);
		 curr = curr->next;
	 }
	 
	 curr = node;
	 fclose(pf);
	 
	 return false;
 }
 
 void printall (uint line) {
	 LIST *node;
	 uint l = line;
	 
	 node = curr;
	 while(curr != NULL) {
		 printf("%d: %s", l, curr->line);
		 curr = curr->next;
		 l++;
	 }
	 putchar('\n');
	 curr = node;
 }
 
 int main (int argc, char **argv) {
	 FILE *pf;
	 char *line;
	 char *filename;
	 char *mode = "r";
	 uint ln = 0;
	 int i;
	 
	 if(argc != 2) {
		 help(argv[0]);
		 return 0;
	 }
	 
	 line = calloc(LINE_LEN, sizeof(char));
	 
	 if(line == NULL) {
		 perror("calloc");
		 return -1;
	 }
	 
	 pf = fopen(argv[1], mode);
	 /* if the file doesn't exist, it will be created */
	 if(pf == NULL) {
		 mode = "w";
		 pf = fopen(argv[1], mode);
		 if(pf == NULL) {
			 perror("fopen");
			 return -1;
		 }
	 }
	 
	 filename = argv[1];
	 
	 /* prepare the list */
	 curr = head = &list;
	 head->prev = NULL;
	 head->next = curr;
	 curr->prev = head;
	 curr->next = NULL;
	 
	 if(!strcmp(mode, "r")) {
	 /* store the contents of the file in the list */
		 while(fgets(line, LINE_LEN, pf) != NULL) {
			 if(insert()) {
				 perror("calloc");
				 fclose(pf);
				 goto die;
			 }
			 strcpy(curr->line, line);
			 ln++;
		 }
		 curr = head->next;
		 ln = 1;
	 } else {
		 strcpy(curr->line, "\n");
		 ln++;
	 }
	 
	 fclose(pf);
	 
	 while(fgets(line, LINE_LEN, stdin) != NULL) {
		 switch(*line) {
			 case 'p':
				 line++;
				 if(*line == '*')
					 printall(ln);
				 else printf("%d: %s", ln, curr->line);
			 break;
			 
			 case '+':
				 line++;
				 if(isdigit(*line)) {
					 for(i = atoi(line); i > 0; i--) {
						 if(curr->next == NULL) {
							 puts("End of file.");
							 break;
						 }
						 curr = curr->next;
						 ln++;
					 }
				 } else puts("Bad use of \'+\'.");
			 break;
				 
			 case '-':
				 line++;
				 if(isdigit(*line)) {
					 for(i = atoi(line); i > 0; i--) {
						 if(curr->prev == head) {
							 puts("Start of file.");
							 break;
						 }
						 curr = curr->prev;
						 ln--;
					 }
				 } else puts("Bad use of \'-\'.");
			 break;
				 
			 case 'q':
			         goto die;
			 break;
			 
			 case 'd':
				 if(erase())
					 puts("Can't delete more.");
				 else if(ln > 1) ln--;
			 break;
			
			 case 'n':
				 if(insert()) {
					 perror("calloc");
					 goto die;
				 }
				 else {
					 strcpy(curr->line, "\n");
					 ln++;
				 }
			 break;
			 
			 case '>':
				 line++;
			         strcpy(curr->line, line);
			 break;
			 
			 case 's':
				 if(save(filename))
					 printf("Can't save to %s.\n", filename);
				 else printf("Saved to %s.\n", filename);
			 break;
				 
			 default:
				 puts("Unknown command.");
			 break;
		 }
	 }
	 
	 die: /* clean up and exit */
	 while(!erase());
	 return 0;
 }