path: root/backend/server.cpp

#include <stdio.h>
#include <wS2tcpip.h>
#include <string.h>
#include <assert.h>
#include <time.h>
#include "stringmanip.h"

#pragma comment (lib, "ws2_32.lib")

#define WIN32_LEAN_AND_MEAN
#define PORT 80
#define NUM_CLIENT_THREADS 8

void handleClient(SOCKET clientSocket);
DWORD WINAPI runConnection(LPVOID lpParam);

struct ClientConnection {
    bool isActive = false;
    SOCKET clientSocket;
};

struct ClientConnectionThreadArray {
    ClientConnection    connectionList[NUM_CLIENT_THREADS];
    DWORD               threadIdArray[NUM_CLIENT_THREADS];
    HANDLE              threadArray[NUM_CLIENT_THREADS];

    void start() {
        for (int tIdx = 0; tIdx < NUM_CLIENT_THREADS; tIdx++) {
            threadArray[tIdx] = CreateThread(
                NULL,
                0,
                runConnection,
                &connectionList[tIdx],
                0,
                &threadIdArray[tIdx]
            );
        }
    }

    void run(SOCKET clientSocket) {
        bool found = false;
        while (!found) {
            for (int connIdx = 0; connIdx < NUM_CLIENT_THREADS; connIdx++) {
                if (!connectionList[connIdx].isActive) {
                    connectionList[connIdx].clientSocket = clientSocket;
                    connectionList[connIdx].isActive = true;
                    found = true;
                    break;
                }
            }

            if (!found) {
                Sleep(50);
            }
        }
    }
};

int main() {
    // Initializing Winsock
    WSADATA wsaData;
    WORD version = MAKEWORD(2, 2);

    int wsOK = WSAStartup(version, &wsaData);
    if (wsOK != 0) {
        printf("Cannot initialize winsock: %d\n", wsOK);
        return EXIT_FAILURE;
    }

    // Creating a socket
    SOCKET listeningSocket = socket(AF_INET, SOCK_STREAM, 0);
    if (listeningSocket == INVALID_SOCKET) {
        printf("Cannot create socket\n");
        return EXIT_FAILURE;
    }

    // Bind an IP address and port to a socket
    sockaddr_in hint = { 0 };
    hint.sin_family = AF_INET;
    hint.sin_port = htons(PORT);   // Networking is big endian, while PCs are little endian
    hint.sin_addr.S_un.S_addr = htonl(INADDR_ANY);

    bind(listeningSocket, (sockaddr*)&hint, sizeof(hint));

    // Tell Winsock the socket is for listening
    listen(listeningSocket, SOMAXCONN);

    ClientConnectionThreadArray threadManager;
    threadManager.start();

    while (true) {
        
        // Wait for a connection
        sockaddr_in client;
        int clientSize = sizeof(client);

        SOCKET clientSocket = accept(listeningSocket, (sockaddr*)&client, &clientSize);
        if (clientSocket == INVALID_SOCKET) {
            printf("Cannot create the client socket\n");
            return EXIT_FAILURE;
        }

        char host[NI_MAXHOST];          // Client's remote name
        char service[NI_MAXSERV];      // Service (i.e. port) the client is connected on

        ZeroMemory(host, NI_MAXHOST);
        ZeroMemory(service, NI_MAXSERV);

        if (getnameinfo((sockaddr*)&client, sizeof(client), host, NI_MAXHOST, service, NI_MAXSERV, 0) == 0) {
            printf("Host %s connected on port %s\n", host, service);
        } else {
            inet_ntop(AF_INET, &client.sin_addr, host, NI_MAXHOST);
            printf("Host %s connected on port %d\n", host, ntohs(client.sin_port));
        }

        threadManager.run(clientSocket);
    }

    // Close listening socket
    closesocket(listeningSocket);

    // Cleanup winsock
    WSACleanup();

    return EXIT_SUCCESS;
}

enum HttpRequestType {
    HttpRequestType_None,
    HttpRequestType_Get
};

enum HttpRequestError {
    HttpRequestError_None,
    HttpRequestError_UnsupportedRequest,
    HttpRequestError_NoBuffer,
    HttpRequestError_ClientDisconnect
};

struct HeaderParseResult {
    HttpRequestType requestType;
    char resource[512];
    HttpRequestError error = HttpRequestError_None;
};


struct HeaderParser {
    char buffer[4096];
    int bufferPtr = 0;
    int bufferSize = 0;
    char line[512];
    int lineIndex = 0 ;

    bool tryReadLine() {
        int startIndex = bufferPtr;
        int endIndex = startIndex;
        while (true) {
            if (bufferPtr >= bufferSize) {
                endIndex = bufferPtr;
                break;
            }

            if (strncmp(&buffer[bufferPtr], "\r\n", 2) == 0) {
                endIndex = bufferPtr;
                bufferPtr += 2; // Move past the new line character
                break;
            }

            bufferPtr++;
        }

        int lineLength = endIndex - startIndex;
        if (lineLength == 0) {
            return false;
        }

        assert(lineLength < 512 && lineLength > 0);
        strncpy_s(line, &buffer[startIndex], lineLength);
        line[lineLength] = '\0';
        return true;
    }

    HeaderParseResult readHeader(SOCKET clientSocket) {
        HeaderParseResult retval;
        ZeroMemory(buffer, 4096);

        // Wait for client to send data
        bufferSize = recv(clientSocket, buffer, 4096, 0);
        if (bufferSize == SOCKET_ERROR) {
            printf("Error in receive. Quitting\n");
            retval.error = HttpRequestError_NoBuffer;
            return retval;
        } else if (bufferSize == 0) {
            printf("Client disconnected\n");
            retval.error = HttpRequestError_ClientDisconnect;
            return retval;
        }

        printf("Received message (%d bytes): %s", bufferSize, buffer);

        while (tryReadLine()) {
            if (lineIndex == 0) {
                // Parse request, only supporting GETs for now
                int linePtr = 0;
                if (strncmp(line, "GET ", 3) == 0) {
                    retval.requestType = HttpRequestType_Get;
                    linePtr += 4; // Move past teh get
                } else {
                    retval.error = HttpRequestError_UnsupportedRequest;
                    return retval;
                }

                copyUntilStr(retval.resource, &line[linePtr], " ");
                printf("Get request on resource: %s\n", retval.resource);
            }
                
            lineIndex++;
        }

        return retval;
    }
};

enum FileType {
    FileType_None,
    FileType_HTML,
    FileType_CSS,
    FileType_JS
};

enum HttpStatusCode {
    HttpStatusCode_OK = 200,
    HttpStatusCode_BADREQUEST = 400,
    HttpStatusCode_NOTFOUND = 404
};

void sendErrorMessage(SOCKET socket, HttpStatusCode status, const char* errorHtml) {
    char timeStr[100];
    char header[512];

    ZeroMemory(timeStr, 100);
    ZeroMemory(header, 100);

    const char* errorMessage;
    switch (status) {
    case HttpStatusCode_BADREQUEST:
        errorMessage = "Bad Request";
        break;
    case HttpStatusCode_NOTFOUND:
        errorMessage = "Not found";
        break;
    default:
        errorMessage = "Unknown";
        break;
    }

    getCurrentDateStr(timeStr);
    int contentLen = strlen(errorHtml);
    sprintf(header, "HTTP/1.1 %d %s\r\nDate: %s\r\nContent-Type: text/html; charset=utf-8\r\nConnection: keep-alive\r\nContent-Length: %d\r\n\r\n", status, errorMessage, timeStr, contentLen);
    send(socket, header, strlen(header), 0);
    
    send(socket, errorHtml, contentLen, 0);
}

#define MAXBUFLEN 1000000

int readFileToMemory(char* filepath, char source[MAXBUFLEN + 1], bool isBinary) {
    FILE* file;
    fopen_s(&file, filepath, isBinary ? "rb" : "r+");

    if(file == NULL) {
        printf("Failed to read the file\n");
        return -1;
    }

    size_t newLen = fread(source, sizeof(char), MAXBUFLEN, file);
    if ( ferror( file ) != 0 ) {
        fputs("Error reading file", stderr);
        return -1;
    }

    fclose(file);
    return newLen;
}


int fixNewLines(char* str, int strSize) {
    int removed = 0;
    for(int i = 0; i < strSize; i++) {
		if(str[i] == '\n') {
            str[i] = '\r\n';
            removed++;
		} 
	}

    return removed;
}


bool trySendFile(SOCKET clientSocket, char* filename) {
    char filePath[128];
    sprintf(filePath, "../../frontend%s", filename);

    bool isBinary = false;
    if (endsWith(filename, ".ico")) {
        isBinary = true;
    }

    char source[MAXBUFLEN + 1];
    int fileSizeBytes = readFileToMemory(filePath, source, isBinary);

    if (fileSizeBytes <= 0) {
        return false;
    }

    const char* contentType;
    if (endsWith(filename, ".html")) {
        contentType = "text/html";
    } else if (endsWith(filename, ".js")) {
        contentType = "application/javascript";
    } else if (endsWith(filename, ".css")) {
        contentType = "text/css";
    } else if (endsWith(filename, ".ico")) {
        contentType = "image/x-icon";
    } else {
        contentType = "text/plain";
    }

    char timeStr[100];
    char header[512];

    ZeroMemory(timeStr, 100);
    ZeroMemory(header, 100);

    getCurrentDateStr(timeStr);
    sprintf(header, "HTTP/1.1 200 OK\r\nDate: %s\r\nContent-Type: %s; charset=utf-8\r\nConnection: keep-alive\r\nContent-Length: %d\r\n\r\n", timeStr, contentType, fileSizeBytes);
    send(clientSocket, header, strlen(header), 0);
    

    int bytesSent = 0;
    int bytesRemaining = fileSizeBytes;
    while (bytesSent < fileSizeBytes) {
        int amountToSend = bytesRemaining >= 4096 ? 4096 : bytesRemaining; // Send 4K bytes at a time max
        send(clientSocket, &source[bytesSent], amountToSend, 0);
        bytesRemaining -= amountToSend;
        bytesSent += amountToSend;
    }

    return true;
}

void handleClient(SOCKET clientSocket) {
    while (true) {
        HeaderParser parser;
        HeaderParseResult parseResult = parser.readHeader(clientSocket);
        bool shouldBreak = false;

        switch (parseResult.error) {
        case HttpRequestError_ClientDisconnect: {
            shouldBreak = true;
            break;
        }
        case HttpRequestError_UnsupportedRequest: {
            shouldBreak = true;
            break;
        }
        }

        if (shouldBreak) {
            break;
        }

        switch (parseResult.requestType) {
        case HttpRequestType_Get: {
            if (strcmp(parseResult.resource, "/") == 0) {
                trySendFile(clientSocket, (char*)"/index.html");
            } else {
                trySendFile(clientSocket, parseResult.resource);
            }
            shouldBreak = true;
            break;
        }
        }

        if (shouldBreak) {
            break;
        }
    }

    // Close the socket
    closesocket(clientSocket);
}

DWORD WINAPI runConnection(LPVOID lpParam) {
    ClientConnection* connection = (ClientConnection*)lpParam;

    while (true) {
        Sleep(100);

        if (connection->isActive) {
            handleClient(connection->clientSocket);
            connection->isActive = false;
        }
    }
}