/*

COMP2123 Mini Group Project Members List

Name				StudentID
Chan Tik Shun		3035536553
Lui Kin Ping		3035537363

*/

#include <iostream>
#include <stdlib.h> // for system()
#include <string> // for storing, processing and validating command
#include <ctime> // for clock_t, clock()

using namespace std;

struct history { // struct for each command
    string command;
    double runTime;
    history *next;
};

void historyInsert(history *& h, const string & c, const double & r);

void printHistory(history *h, int displayed);

void copyHistory(history *source, history *&destin);

bool isSorted(history *h);

void sortHistory(history *&h);

string normalize(const string original_string) { // delete optional space and determine whether the string fits the format
    string temp_string;
    bool potential_sbu = true;

    for(int i=0; i < original_string.size(); i++) { // check every character one by one
    	if (original_string[i] != ' ') // omit the space character
    		temp_string += ((char)(original_string[i])); // directly input the character

    	if (temp_string == "history" && potential_sbu) {
    		if( ((original_string.size() - 1 - i) >= 6) && potential_sbu ) { // check length of remaining string after "(optional space)history" (prevent array index out of bound!!!)
    			string remain_option = original_string.substr(i+1, original_string.size()-1-i); // remaining string

    			if(remain_option[0] != ' ' || remain_option[remain_option.size()-1] != ' ') // omit "(optional space)history(NO space)-sbu(optional space)", "(optional space)history(optional space)-sbu(NO space)"
    				potential_sbu = false;

    			string temp_substring; // for storing remaining string without spaces
    			for(int j=0; (j < remain_option.size() && potential_sbu); j++) {
    				if (remain_option[j] != ' ') // omit the space character
    					temp_substring += ((char)(remain_option[j])); // directly input the character
				}

    			if(temp_substring == "-sbu" && potential_sbu) // whether remaining string after "(optional space)history" is "(one or more space)-sbu(one or more space)"
    				return "history -sbu ";
			} else {
				potential_sbu = false; // treat "(optional space)history(more than one space)-sbu(optional space)" as a normal command
			}
		}
 	}

    if (temp_string == "history" || temp_string == "exit")
    	return temp_string; // history or exit command

	return original_string; // return the original string as command and keep all the spaces
}

int main() {

	string command;
	history *listOfHistory = NULL;

	while ( (cout << "tinyshell>") && (getline(cin, command)) ) {  // store the user input into command (whole line)

		string new_command = normalize(command); // remove any optional space and check whether it matches the format of built-in command

		clock_t begin = clock(); // start time of the command

		if(new_command == "history") {
			// display last 5 commands, later command first
			printHistory(listOfHistory, 1); // print first 5 history, or until the end

		} else if (new_command == "history -sbu ") {
			// display slowest 5 commands, slower command first
			history *sortedHistory = NULL;
			copyHistory(listOfHistory, sortedHistory);
    		sortHistory(sortedHistory);
    		printHistory(sortedHistory, 1);
    		delete sortedHistory;
    		sortedHistory = NULL;
		} else if (new_command == "exit") {
			// terminate program
			exit(0);
		} else {
			// pass the command to the terminal
			system(command.c_str());

			clock_t end = clock(); // end time of the command
			double runTime = double(end - begin) / CLOCKS_PER_SEC; // return total execution time
			historyInsert(listOfHistory, command, runTime); // update history
		}
		cout << endl; // break line
	}
}

void historyInsert(history *& h, const string & c, const double & r) {
    history *newH = new history;
    newH -> command = c;
    newH -> runTime = r;
    newH -> next = h;
    h = newH;
}

void printHistory(history *h, int displayed) {
    if ( (h == NULL) || (displayed > 5) )
        return;
    else {
        cout << h -> command << "  " << h -> runTime << "s" << endl;
        printHistory(h->next, displayed+1);
    }
}

void copyHistory(history *source, history *&destin){
	if (source == NULL)
		return;
	else{
		copyHistory(source->next, destin);
		historyInsert(destin, source->command, source->runTime);
	}
}

bool isSorted(history *h) {
    if (h == NULL || h->next == NULL) {
        return true;
    } else if (h->runTime >= h->next->runTime){
    	return isSorted(h->next);
    } else {
    	return false;
    }
}

void sortHistory(history *&h) {
    if (h == NULL || h->next == NULL)
        return;
    while (!isSorted(h)){
        if (h->runTime >= h->next->runTime){
            sortHistory(h->next);
        } else {
            history *tempHistory1 = new history;
            history *tempHistory2 = new history;
            tempHistory1->command = h->command;
            tempHistory1->runTime = h->runTime;
            tempHistory1->next = h->next->next;
            tempHistory2 = h->next;
            tempHistory2->next = tempHistory1;
            h = tempHistory2;
            sortHistory(h->next);
        }
    }
}