#include <stdio.h>

/*A program for finding the longest line in its input, and then returning the
 * longest. Primarily copied from page 30 of KNR C by Kernigham Ritchie.
 * Annotation is extremely verbose so that I could break this code down for
 * myself in a way that made more sense than as-written.*/

#define MAXLINE 1000 //Define maximum allowable line length.

//Forward declaration for a function that will retreive the current line and
//store it in array line[]. Since modern C actually has a getline function, we
//declare this as pullline
int pullLine(char line[], int maxline);
//Forward declaration for a function to copy between arrays.
void copy(char from[], char to[]);

int main(){

	//Declare ints related to tracking line lengths.
	int currentLength; //Length of current line; originally len.
	int max = 0; //Length of longest line encountered; originally max.
					 //Initialized as 0 as opposed to using a separate
					 //statement to set value as in original code.

	char line[MAXLINE]; //Initialize array for storing current line.
	char longest[MAXLINE]; //Initialize array for storing longest line so far.
	
	while ((currentLength = pullLine(line, MAXLINE)) > 0){
		if (currentLength > max){
			max = currentLength;
			copy(line, longest);
		}
	}
	if (max > 0) //If any lines were encountered, print the longest.
		printf("%s", longest);
	return 0;
}

//pullLine will read a line into array s[] and return its length.
int pullLine(char s[], int lim){
	int c, i;
	/*Set i= 0, check if i is < lim, which is MAXLINE as written AND that
	 * getchar returns a non EOF character (while stepping c) AND that the 
	 * character pulled (c), is not a newline character, then increment i. The
	 * actual body of this loop simply stores the value of the retrieved 
	 * character in array s[] at position |i|.*/
	for (i = 0; i < lim-1 && (c=getchar())!=EOF && c!='\n'; ++i)
		s[i] = c;

	if (c == '\n'){ //If |c| is \n, then still set pos \i\ in array s[] and 
					//increment i. This has to be handled outside the for loop,
					//since c =='\n' is a break condition.
		s[i] = c;
		++i;
	}
	s[i] = '\0'; //Set a null value at the end of the line for termination.
	return i; //Return the length of the line pulled.
}

//Function for copying one array to another. I chose to write this as
//from -- > to instead of to --> from because it's not the 90s any more and 
//I feel like I'm allowed to have a little temporal linearity as a treat.
void copy(char from[], char to[]){
	int i = 0; //I have once again initialized and declared in the same line
			   //because it is 2025.

	//Set the value of pos \i\ in to[] to the value of pos \i\ in from as long
	//as it is not null.
	while ((to[i] = from[i]) != '\0')
		++i;
}