Download displaycode.cc 
//cgi which displays source code (C, C++) in html using prims.js and
//prism.css. Source code file is passed in variable filename in get request:
//displaycode?lang=en&filename=loggbok.c ... for example.

#include<iostream>
#include<string>
#include<string.h>
#include<fstream>
#include<sstream>
#include<cgicc/Cgicc.h>
#include<cgicc/HTMLClasses.h>
#include<cgicc/HTTPHTMLHeader.h>

using namespace cgicc;
using namespace std;

//Next two strings contain html to be placed at beginning and end of output.
string header = "<!DOCTYPE html>\n"
	"<html lang=\"en\">\n"
	"<head>\n"
	"<meta charset=\"UTF-8\"/>\n"
	"<title>filename</title>"
	"<link href=\"https://briansmath.ddns.net/Code/prism.css\" rel=\"stylesheet\">\n"
	"<link rel = \"icon\" href = \"https://briansmath.ddns.net/mathicon.png\" type = \"image/x-icon\">"
	"</head>\n"
	"<body>\n"
	"<script src=\"https://briansmath.ddns.net/Code/prism.js\"></script>\n"
	"<a href=\"filename\" download>Download filename</a>\n"
	"<pre class=\"line-numbers\">\n"
	"<code class=\"language-c\">";
//NOTE: 'filenanme' to be replaced by file name given in GET request. 

string footer = "</code>\n</pre>\n</body>\n</html>";
//Output will be header + data_from_file + footer.


//MAIN *********************************************************************************************
int main(int argc, char **argv){
	Cgicc formData; //File name should be formData("filename")
	ifstream myfile;
	
	if(formData("filename").find("/") != string::npos){ //Why do you think this block is here 🤔
		if(formData("lang")=="en")
			myfile.open("error.en.html");
		else	
			myfile.open("error.html");
		cout << cgicc::HTTPHTMLHeader() << endl;
		cout << myfile.rdbuf();
		myfile.close();
		return 0;
	}


	//Replace 'filename' with actual file name.
	header.replace(header.find("filename"), strlen("filename"), formData("filename"));
	header.replace(header.find("filename"), strlen("filename"), formData("filename"));
	header.replace(header.find("filename"), strlen("filename"), formData("filename"));
	// ... ok, that was a lazy way to do that.

	myfile.open(formData("filename").c_str()); //Attempt to open the file.
	if(!myfile.is_open()){ //Check if file is open: if not display error page and return.
		if(formData("lang")=="en")
			myfile.open("error.en.html");
		else
			myfile.open("error.html");
		cout << cgicc::HTTPHTMLHeader() << endl;
		cout << myfile.rdbuf();
		myfile.close();
		return 0;
	}

	ostringstream os; 
	os << myfile.rdbuf(); //read the file into osstream os.
	myfile.close();

	string outs = os.str(); //File contents now in string outs.

	//We now need to replace html speicial characters with approppriate codes
	size_t pos = 0; 
	while(true){
		pos = outs.find("<", pos);
		if (pos == string::npos)
			break;
		outs.replace(pos, 1, "<"); //  '<' here is actually &lt in source code.
	}
	pos = 0;
	while(true){
		pos = outs.find(">", pos);
		if (pos == string::npos)
			break;
		outs.replace(pos, 1, ">"); //  '>' here is actually &lt in source code.
	}

	
	//Hopefully the output string has been doctored enough:
	//SEND IT DOWN THE WIRE 🙂	
	cout << cgicc::HTTPHTMLHeader() << endl;
	cout << header << outs << footer << endl;

	return 0;
}