#include "coreclrutil.h"
#include <dirent.h>
#include <assert.h>
#include <string.h>
#include <sys/stat.h>
#include <set>

namespace CoreCLRUtil
{

bool GetAbsolutePath(const char* path, std::string& absolutePath)
{
    bool result = false;

    char realPath[PATH_MAX];
    if (realpath(path, realPath) != nullptr && realPath[0] != '\0')
    {
        absolutePath.assign(realPath);
        // realpath should return canonicalized path without the trailing slash
        assert(absolutePath.back() != '/');

        result = true;
    }

    return result;
}

bool GetDirectory(const char* absolutePath, std::string& directory)
{
    directory.assign(absolutePath);
    size_t lastSlash = directory.rfind('/');
    if (lastSlash != std::string::npos)
    {
        directory.erase(lastSlash);
        return true;
    }

    return false;
}

bool GetClrFilesAbsolutePath(const char* currentExePath, const char* clrFilesPath, std::string& clrFilesAbsolutePath)
{
    std::string clrFilesRelativePath;
    const char* clrFilesPathLocal = clrFilesPath;
    if (clrFilesPathLocal == nullptr)
    {
        // There was no CLR files path specified, use the folder of the corerun/coreconsole
        if (!GetDirectory(currentExePath, clrFilesRelativePath))
        {
            perror("Failed to get directory from argv[0]");
            return false;
        }

        clrFilesPathLocal = clrFilesRelativePath.c_str();

        // TODO: consider using an env variable (if defined) as a fall-back.
        // The windows version of the corerun uses core_root env variable
    }

    if (!GetAbsolutePath(clrFilesPathLocal, clrFilesAbsolutePath))
    {
        perror("Failed to convert CLR files path to absolute path");
        return false;
    }

    return true;
}

void AddFilesFromDirectoryToTpaList(const char* directory, std::string& tpaList)
{
    const char * const tpaExtensions[] = {
                ".ni.dll",      // Probe for .ni.dll first so that it's preferred if ni and il coexist in the same dir
                ".dll",
                ".ni.exe",
                ".exe",
                };
                
    DIR* dir = opendir(directory);
    if (dir == nullptr)
    {
        return;
    }

    std::set<std::string> addedAssemblies;

    // Walk the directory for each extension separately so that we first get files with .ni.dll extension,
    // then files with .dll extension, etc.
    for (int extIndex = 0; extIndex < sizeof(tpaExtensions) / sizeof(tpaExtensions[0]); extIndex++)
    {
        const char* ext = tpaExtensions[extIndex];
        int extLength = strlen(ext);

        struct dirent* entry;

        // For all entries in the directory
        while ((entry = readdir(dir)) != nullptr)
        {
            // We are interested in files only
            switch (entry->d_type)
            {
            case DT_REG:
                break;

            // Handle symlinks and file systems that do not support d_type
            case DT_LNK:
            case DT_UNKNOWN:
                {
                    std::string fullFilename;

                    fullFilename.append(directory);
                    fullFilename.append("/");
                    fullFilename.append(entry->d_name);

                    struct stat sb;
                    if (stat(fullFilename.c_str(), &sb) == -1)
                    {
                        continue;
                    }

                    if (!S_ISREG(sb.st_mode))
                    {
                        continue;
                    }
                }
                break;

            default:
                continue;
            }

            std::string filename(entry->d_name);

            // Check if the extension matches the one we are looking for
            int extPos = filename.length() - extLength;
            if ((extPos <= 0) || (filename.compare(extPos, extLength, ext) != 0))
            {
                continue;
            }

            std::string filenameWithoutExt(filename.substr(0, extPos));

            // Make sure if we have an assembly with multiple extensions present,
            // we insert only one version of it.
            if (addedAssemblies.find(filenameWithoutExt) == addedAssemblies.end())
            {
                addedAssemblies.insert(filenameWithoutExt);

                tpaList.append(directory);
                tpaList.append("/");
                tpaList.append(filename);
                tpaList.append(":");
            }
        }
        
        // Rewind the directory stream to be able to iterate over it for the next extension
        rewinddir(dir);
    }
    
    closedir(dir);
}

} // namespace CoreCLRUtil