#include <Windows.h>
#include <stdio.h>
#include <string.h>
#include <wchar.h>

static void printHelp();
static bool copyDirRecursively(
    const wchar_t *srcPath, const wchar_t *dstPath
);

int main() {
    /* Get command line args in Unicode */
    wchar_t *commandLine = GetCommandLineW();
    int argc;
    wchar_t **commandLineArgs = CommandLineToArgvW(
        commandLine, &argc
    );

    /*
    wprintf(L"argc=%d\n", argc);
    for (int i = 0; i < argc; ++i) {
        wprintf(
            L"argv[%d]=\"%ls\"\n", 
            i, commandLineArgs[i]
        );
    }
    */

    if (argc < 3) {
        printHelp();
        LocalFree(commandLineArgs); 
        return 1;
    }

    DWORD attr = GetFileAttributesW(commandLineArgs[1]);
    if (attr == INVALID_FILE_ATTRIBUTES) {
        printf("Illegal source directory.\n");
        LocalFree(commandLineArgs); 
        return (-1);
    } else if ((attr & FILE_ATTRIBUTE_DIRECTORY) == 0) {
        printf("Source is not a directory.\n");
        LocalFree(commandLineArgs); 
        return (-1);
    }

    attr = GetFileAttributesW(commandLineArgs[2]);
    if (attr == INVALID_FILE_ATTRIBUTES) {
        printf("Illegal destination directory.\n");
        LocalFree(commandLineArgs); 
        return (-1);
    } else if ((attr & FILE_ATTRIBUTE_DIRECTORY) == 0) {
        printf("Destination is not a directory.\n");
        LocalFree(commandLineArgs); 
        return (-1);
    }
    if (!copyDirRecursively(commandLineArgs[1], commandLineArgs[2])) {
        LocalFree(commandLineArgs); 
        return (-1);
    }

    LocalFree(commandLineArgs); 
    return 0;
}

static void printHelp() {
    wprintf(
        L"Copy contents of a directory recursively.\n"
        "Usage:\n"
        "\trcopy sourceDir destinationDir\n"
    );
}

static bool copyDirRecursively(
    const wchar_t *srcPath, const wchar_t *dstPath
) {
    DWORD attr = GetFileAttributesW(srcPath);
    if (
        attr == INVALID_FILE_ATTRIBUTES ||
        (attr & FILE_ATTRIBUTE_DIRECTORY) == 0
    ) {
        return false;
    }

    attr = GetFileAttributesW(dstPath);
    if (
        attr == INVALID_FILE_ATTRIBUTES ||
        (attr & FILE_ATTRIBUTE_DIRECTORY) == 0
    ) {
        return false;
    }

    wchar_t srcFile[MAX_PATH];
    wcscpy(srcFile, srcPath);
    size_t len = wcslen(srcFile);
    if (len == 0)
        return false;
    if (srcFile[len-1] != L'\\' && srcFile[len-1] != L'/')
        wcscat(srcFile, L"\\");
    int srcLen = wcslen(srcFile);
    
    wchar_t pattern[MAX_PATH];
    wcscpy(pattern, srcFile);
    wcscat(pattern, L"*");

    wchar_t dstFile[MAX_PATH];
    wcscpy(dstFile, dstPath);
    len = wcslen(dstFile);
    if (len == 0)
        return false;
    if (dstFile[len-1] != L'\\' && dstFile[len-1] != L'/')
        wcscat(dstFile, L"\\");
        
    size_t dstLen = wcslen(dstFile);

    WIN32_FIND_DATAW findData;
    HANDLE h;
    h = FindFirstFileW(pattern, &findData);
    while (h != INVALID_HANDLE_VALUE) {
        if (
            wcscmp(findData.cFileName, L"..") != 0 &&
            wcscmp(findData.cFileName, L".") != 0
        ) {
            wcscpy(srcFile + srcLen, findData.cFileName);
            wcscpy(dstFile + dstLen, findData.cFileName);
            wprintf(L"%ls -> %ls\n", srcFile, dstFile);

            if (
                (findData.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY) != 0
            )
            {
                // Make subdirectory in destination directory
                if (!CreateDirectoryW(
                    dstFile, NULL
                )) {
                    DWORD err = GetLastError();
                    if (err != 0 && err != ERROR_ALREADY_EXISTS) {
                        wprintf(L"Cannot create a directory, err=%d\n", err);
                        return false;
                    }
                }
                if (!copyDirRecursively(
                    srcFile, dstFile
                )) {
                    wprintf(
                        L"Failed to copy subdirectory %ls\n",
                        findData.cFileName
                    );
                    return false;
                }
            } else {
                // Normal file
                if (!CopyFileW(srcFile, dstFile, FALSE)) {
                    wprintf(
                        L"Cannot copy the file %ls\n",                
                        findData.cFileName
                    );
                    return false;
                }
            }
        }

        if (!FindNextFileW(h, &findData)) 
            break;
    }
    FindClose(h);
        
    return true;
}