process.c

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#include "../include/process.h"
#include "../include/file.h"  // Required for INVALID_NATIVE_HANDLE
 
#include <errno.h>
#include <stddef.h>
 
#ifdef _WIN32
#include <io.h>  // for _access
#define ACCESS _access
#ifndef X_OK
// Windows doesn't have X_OK, but MinGW does.
#define X_OK 0
#endif
 
#define PATH_SEP ";"   // Windows uses semicolon
#define DIR_SEP  "\\"  // Windows directory separator
// #define strtok_r strtok_s  // MSVC equivalent (this line caused issues on POSIX)
 
#else
#include <unistd.h>  // for access
#define ACCESS   access
#define PATH_SEP ":"  // POSIX uses colon
#define DIR_SEP  "/"  // POSIX directory separator
#endif
 
// Helper function to search for command in PATH
static char* find_in_path(const char* command, const char* const* environment) {
    if (!command) return NULL;
 
#ifdef _WIN32
    // Windows: Check for absolute path (C:\ or \\‍) or relative path (. or ..)
    if ((command[0] != '\0' && command[1] == ':') ||  // C:\path
        command[0] == '\\' ||                         // \path or \\network
        command[0] == '.') {                          // .\path or ..\path
        return strdup(command);
    }
#else
    // POSIX: Check for absolute or relative path
    if (command[0] == '/' || command[0] == '.') {
        return strdup(command);
    }
#endif
 
    // Find PATH in environment
    const char* path_env = NULL;
    for (int i = 0; environment && environment[i]; i++) {
        if (strncmp(environment[i], "PATH=", 5) == 0) {
            path_env = environment[i] + 5;
            break;
        }
    }
 
    if (!path_env) {
        return NULL;  // No PATH in environment
    }
 
    // Search each PATH component
    char* path_copy = strdup(path_env);
    if (!path_copy) return NULL;
 
    char* saveptr = NULL;
    char* dir = strtok_r(path_copy, PATH_SEP, &saveptr);
    char full_path[4096];
 
    while (dir) {
        snprintf(full_path, sizeof(full_path), "%s%s%s", dir, DIR_SEP, command);
#ifdef _WIN32
        // Windows: Try with and without .exe extension
        if (ACCESS(full_path, X_OK) == 0) {
            free(path_copy);
            return strdup(full_path);
        }
 
        // Try adding .exe extension
        char exe_path[4096];
        snprintf(exe_path, sizeof(exe_path), "%s.exe", full_path);
 
        if (ACCESS(exe_path, X_OK) == 0) {
            free(path_copy);
            return strdup(exe_path);
        }
#else
        if (ACCESS(full_path, X_OK) == 0) {
            free(path_copy);
            return strdup(full_path);
        }
#endif
 
        dir = strtok_r(NULL, PATH_SEP, &saveptr);
    }
 
    free(path_copy);
    return NULL;
}
 
/* Platform-specific implementations of process and pipe handles */
#ifdef _WIN32
struct ProcessHandle {
    PROCESS_INFORMATION process_info;
    bool detached;
};
 
#else
struct ProcessHandle {
    pid_t pid;
    bool detached;
};
#endif
 
struct PipeHandle {
    PipeFd read_fd;
    PipeFd write_fd;
    bool read_closed;
    bool write_closed;
};
 
// New structure to represent file redirection
struct FileRedirection {
    int fd;              // File descriptor
    bool close_on_exec;  // Whether to close on exec
};
 
/* Default options for process creation */
static const ProcessOptions DEFAULT_OPTIONS = {
    .working_directory = NULL,
    .inherit_environment = true,
    .environment = NULL,
    .detached = false,
    .io =
        {
            .stdin_pipe = NULL,
            .stdout_pipe = NULL,
            .stderr_pipe = NULL,
            .merge_stderr = false,
        },
};
 
/* Error handling helper functions */
ProcessError process_system_error(void) {
#ifdef _WIN32
    DWORD error = GetLastError();
    switch (error) {
        case ERROR_INVALID_PARAMETER:
            return PROCESS_ERROR_INVALID_ARGUMENT;
        case ERROR_NOT_ENOUGH_MEMORY:
            return PROCESS_ERROR_MEMORY;
        case ERROR_ACCESS_DENIED:
            return PROCESS_ERROR_PERMISSION_DENIED;
        case ERROR_BROKEN_PIPE:
        case ERROR_PIPE_BUSY:
        case ERROR_PIPE_NOT_CONNECTED:
            return PROCESS_ERROR_IO;
        default:
            return PROCESS_ERROR_UNKNOWN;
    }
#else
    switch (errno) {
        case EINVAL:
            return PROCESS_ERROR_INVALID_ARGUMENT;
        case ENOMEM:
            return PROCESS_ERROR_MEMORY;
        case EACCES:
        case EPERM:
            return PROCESS_ERROR_PERMISSION_DENIED;
        case EBADF:
        case EPIPE:
            return PROCESS_ERROR_IO;
        case ECHILD:
            return PROCESS_ERROR_WAIT_FAILED;
        default:
            return PROCESS_ERROR_UNKNOWN;
    }
#endif
}
 
bool pipe_read_closed(PipeHandle* handle) { return handle->read_closed; }
 
bool pipe_write_closed(PipeHandle* handle) { return handle->write_closed; }
 
PipeFd pipe_read_fd(PipeHandle* handle) { return handle->read_fd; }
 
PipeFd pipe_write_fd(PipeHandle* handle) { return handle->write_fd; }
 
/* String descriptions for error codes */
const char* process_error_string(ProcessError error) {
    switch (error) {
        case PROCESS_SUCCESS:
            return "Success";
        case PROCESS_ERROR_INVALID_ARGUMENT:
            return "Invalid argument";
        case PROCESS_ERROR_FORK_FAILED:
            return "Fork failed";
        case PROCESS_ERROR_EXEC_FAILED:
            return "Exec failed";
        case PROCESS_ERROR_PIPE_FAILED:
            return "Pipe creation failed";
        case PROCESS_ERROR_MEMORY:
            return "Memory allocation failed";
        case PROCESS_ERROR_WAIT_FAILED:
            return "Wait for process failed";
        case PROCESS_ERROR_KILL_FAILED:
            return "Failed to terminate process";
        case PROCESS_ERROR_TERMINATE_FAILED:
            return "Failed to terminate process";
        case PROCESS_ERROR_PERMISSION_DENIED:
            return "Permission denied";
        case PROCESS_ERROR_IO:
            return "I/O error";
        case PROCESS_ERROR_TIMEOUT:
            return "Operation timed out";
        case PROCESS_ERROR_WOULD_BLOCK:
            return "Operation would block (no data available)";
        case PROCESS_ERROR_PIPE_CLOSED:
            return "Pipe was closed";
        case PROCESS_ERROR_UNKNOWN:
            return "Unknown error";
        default:
            return "Invalid error code";
    }
}
 
/* Implementation of the pipe API */
ProcessError pipe_create(PipeHandle** pipeHandle) {
    if (!pipeHandle) {
        return PROCESS_ERROR_INVALID_ARGUMENT;
    }
 
    *pipeHandle = (PipeHandle*)calloc(1, sizeof(PipeHandle));
    if (!*pipeHandle) {
        return PROCESS_ERROR_MEMORY;
    }
 
#ifdef _WIN32
    SECURITY_ATTRIBUTES security_attrs;
    memset(&security_attrs, 0, sizeof(security_attrs));
    security_attrs.nLength = sizeof(security_attrs);
    security_attrs.bInheritHandle = TRUE;
 
    if (!CreatePipe(&(*pipeHandle)->read_fd, &(*pipeHandle)->write_fd, &security_attrs, 0)) {
        free(*pipeHandle);
        *pipeHandle = NULL;
        return PROCESS_ERROR_PIPE_FAILED;
    }
#else
    int fds[2];
    if (pipe(fds) != 0) {
        free(*pipeHandle);
        *pipeHandle = NULL;
        return PROCESS_ERROR_PIPE_FAILED;
    }
 
    (*pipeHandle)->read_fd = fds[0];
    (*pipeHandle)->write_fd = fds[1];
#endif
 
    return PROCESS_SUCCESS;
}
 
ProcessError pipe_set_nonblocking(PipeHandle* pipe, bool nonblocking) {
    if (!pipe) {
        return PROCESS_ERROR_INVALID_ARGUMENT;
    }
 
#ifdef _WIN32
    DWORD mode = nonblocking ? PIPE_NOWAIT : PIPE_WAIT;
    if (!SetNamedPipeHandleState(pipe->read_fd, &mode, NULL, NULL)) {
        return process_system_error();
    }
    if (!SetNamedPipeHandleState(pipe->write_fd, &mode, NULL, NULL)) {
        return process_system_error();
    }
#else
    int flags;
 
    // Set read end
    flags = fcntl(pipe->read_fd, F_GETFL);
    if (flags == -1) {
        return process_system_error();
    }
 
    if (nonblocking) {
        flags |= O_NONBLOCK;
    } else {
        flags &= ~O_NONBLOCK;
    }
 
    if (fcntl(pipe->read_fd, F_SETFL, flags) == -1) {
        return process_system_error();
    }
 
    // Set write end
    flags = fcntl(pipe->write_fd, F_GETFL);
    if (flags == -1) {
        return process_system_error();
    }
 
    if (nonblocking) {
        flags |= O_NONBLOCK;
    } else {
        flags &= ~O_NONBLOCK;
    }
 
    if (fcntl(pipe->write_fd, F_SETFL, flags) == -1) {
        return process_system_error();
    }
#endif
 
    return PROCESS_SUCCESS;
}
 
ProcessError pipe_read(PipeHandle* pipe, void* buffer, size_t size, size_t* bytes_read, int timeout_ms) {
    if (!pipe || !buffer || pipe->read_closed) {
        return PROCESS_ERROR_INVALID_ARGUMENT;
    }
 
    if (bytes_read) {
        *bytes_read = 0;
    }
 
#ifdef _WIN32
    // Windows implementation remains similar but with better error codes
    DWORD bytes_read_win = 0;
    OVERLAPPED overlapped;
    memset(&overlapped, 0, sizeof(overlapped));
    overlapped.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
 
    if (!overlapped.hEvent) {
        return process_system_error();
    }
 
    if (!ReadFile(pipe->read_fd, buffer, (DWORD)size, NULL, &overlapped)) {
        DWORD error = GetLastError();
        if (error != ERROR_IO_PENDING) {
            CloseHandle(overlapped.hEvent);
            if (error == ERROR_BROKEN_PIPE) {
                return PROCESS_ERROR_PIPE_CLOSED;
            }
            return process_system_error();
        }
    }
 
    DWORD wait_result = WaitForSingleObject(overlapped.hEvent, timeout_ms < 0 ? INFINITE : (DWORD)timeout_ms);
 
    if (wait_result == WAIT_OBJECT_0) {
        if (!GetOverlappedResult(pipe->read_fd, &overlapped, &bytes_read_win, FALSE)) {
            CloseHandle(overlapped.hEvent);
            DWORD error = GetLastError();
            if (error == ERROR_BROKEN_PIPE) {
                return PROCESS_ERROR_PIPE_CLOSED;
            }
            return process_system_error();
        }
        if (bytes_read) {
            *bytes_read = bytes_read_win;
        }
    } else if (wait_result == WAIT_TIMEOUT) {
        CancelIo(pipe->read_fd);
        CloseHandle(overlapped.hEvent);
        // Map 0ms timeout to WOULDBLOCK for consistency with non-blocking reads
        return (timeout_ms == 0) ? PROCESS_ERROR_WOULD_BLOCK : PROCESS_ERROR_TIMEOUT;
    } else {
        CloseHandle(overlapped.hEvent);
        return process_system_error();
    }
 
    CloseHandle(overlapped.hEvent);
#else
    // posix implementation
    if (timeout_ms >= 0) {
        fd_set read_fds;
        FD_ZERO(&read_fds);
        FD_SET(pipe->read_fd, &read_fds);
 
        struct timeval timeout;
        timeout.tv_sec = timeout_ms / 1000;
        timeout.tv_usec = (long)((timeout_ms % 1000) * 1000);
 
        // select returns: -1 (error), 0 (timeout), >0 (ready)
        int select_result = select(pipe->read_fd + 1, &read_fds, NULL, NULL, &timeout);
 
        if (select_result == -1) {
            if (errno == EINTR)
                return PROCESS_ERROR_WOULD_BLOCK;  // Retry logic usually handles this, but here we return
            return process_system_error();
        } else if (select_result == 0) {
            // If timeout was 0, this means "Would Block".
            // If timeout was > 0, this means "Timed Out".
            return (timeout_ms == 0) ? PROCESS_ERROR_WOULD_BLOCK : PROCESS_ERROR_TIMEOUT;
        }
        // If select_result > 0, data is ready, proceed to read()
    }
 
    ssize_t result = read(pipe->read_fd, buffer, size);
    if (result < 0) {
        if (errno == EAGAIN || errno == EWOULDBLOCK) {
            // Non-blocking read with no data available
            return PROCESS_ERROR_WOULD_BLOCK;
        } else if (errno == EPIPE) {
            // Pipe was closed/broken
            return PROCESS_ERROR_PIPE_CLOSED;
        } else if (errno == EBADF) {
            // Invalid file descriptor
            return PROCESS_ERROR_PIPE_CLOSED;
        }
        return process_system_error();
    }
 
    if (result == 0) {
        // EOF - pipe was closed on the write end
        return PROCESS_ERROR_PIPE_CLOSED;
    }
 
    if (bytes_read) {
        *bytes_read = (size_t)result;
    }
#endif
 
    return PROCESS_SUCCESS;
}
 
ProcessError pipe_write(PipeHandle* pipe, const void* buffer, size_t size, size_t* bytes_written, int timeout_ms) {
    if (!pipe || !buffer || pipe->write_closed) {
        return PROCESS_ERROR_INVALID_ARGUMENT;
    }
 
    if (bytes_written) {
        *bytes_written = 0;
    }
 
#ifdef _WIN32
    DWORD bytes_written_win = 0;
    OVERLAPPED overlapped;
    memset(&overlapped, 0, sizeof(overlapped));
    overlapped.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
 
    if (!overlapped.hEvent) {
        return process_system_error();
    }
 
    if (!WriteFile(pipe->write_fd, buffer, (DWORD)size, NULL, &overlapped)) {
        DWORD error = GetLastError();
        if (error != ERROR_IO_PENDING) {
            CloseHandle(overlapped.hEvent);
            if (error == ERROR_BROKEN_PIPE || error == ERROR_NO_DATA) {
                return PROCESS_ERROR_PIPE_CLOSED;
            }
            return process_system_error();
        }
    }
 
    DWORD wait_result = WaitForSingleObject(overlapped.hEvent, timeout_ms < 0 ? INFINITE : (DWORD)timeout_ms);
 
    if (wait_result == WAIT_OBJECT_0) {
        if (!GetOverlappedResult(pipe->write_fd, &overlapped, &bytes_written_win, FALSE)) {
            CloseHandle(overlapped.hEvent);
            DWORD error = GetLastError();
            if (error == ERROR_BROKEN_PIPE || error == ERROR_NO_DATA) {
                return PROCESS_ERROR_PIPE_CLOSED;
            }
            return process_system_error();
        }
        if (bytes_written) {
            *bytes_written = bytes_written_win;
        }
    } else if (wait_result == WAIT_TIMEOUT) {
        CancelIo(pipe->write_fd);
        CloseHandle(overlapped.hEvent);
        return PROCESS_ERROR_TIMEOUT;
    } else {
        CloseHandle(overlapped.hEvent);
        return process_system_error();
    }
 
    CloseHandle(overlapped.hEvent);
#else
    if (timeout_ms >= 0) {
        // For non-zero timeout, we need to use select
        fd_set write_fds;
        FD_ZERO(&write_fds);
        FD_SET(pipe->write_fd, &write_fds);
 
        struct timeval timeout;
        struct timeval* timeout_ptr = NULL;
        timeout.tv_sec = timeout_ms / 1000;
        timeout.tv_usec = ((long)timeout_ms % 1000) * 1000;
        timeout_ptr = &timeout;
        int select_result = select(pipe->write_fd + 1, NULL, &write_fds, NULL, timeout_ptr);
        if (select_result == -1) {
            if (errno == EINTR)
                return PROCESS_ERROR_WOULD_BLOCK;  // Retry logic usually handles this, but here we return
            return process_system_error();
        } else if (select_result == 0) {
            // If timeout was 0, this means "Would Block".
            // If timeout was > 0, this means "Timed Out".
            return (timeout_ms == 0) ? PROCESS_ERROR_WOULD_BLOCK : PROCESS_ERROR_TIMEOUT;
        }
        // If select_result > 0, data is ready, proceed to read()
    }
 
    ssize_t result = write(pipe->write_fd, buffer, size);
    if (result < 0) {
        if (errno == EAGAIN || errno == EWOULDBLOCK) {
            // Non-blocking write - buffer full, no space available
            return PROCESS_ERROR_WOULD_BLOCK;
        } else if (errno == EPIPE) {
            // Broken pipe - read end was closed
            return PROCESS_ERROR_PIPE_CLOSED;
        } else if (errno == EBADF) {
            // Invalid file descriptor
            return PROCESS_ERROR_PIPE_CLOSED;
        }
        return process_system_error();
    }
 
    if (bytes_written) {
        *bytes_written = (size_t)result;
    }
#endif
 
    return PROCESS_SUCCESS;
}
 
void pipe_close(PipeHandle* pipe) {
    if (!pipe) {
        return;
    }
 
#ifdef _WIN32
    if (pipe->read_fd != INVALID_NATIVE_HANDLE && !pipe->read_closed) {
        CloseHandle(pipe->read_fd);
        pipe->read_closed = true;
        pipe->read_fd = INVALID_NATIVE_HANDLE;
    }
    if (pipe->write_fd != INVALID_NATIVE_HANDLE && !pipe->write_closed) {
        CloseHandle(pipe->write_fd);
        pipe->write_closed = true;
        pipe->write_fd = INVALID_NATIVE_HANDLE;
    }
#else
    if (pipe->read_fd != INVALID_NATIVE_HANDLE && !pipe->read_closed) {
        close(pipe->read_fd);
        pipe->read_closed = true;
        pipe->read_fd = INVALID_NATIVE_HANDLE;
    }
    if (pipe->write_fd != INVALID_NATIVE_HANDLE && !pipe->write_closed) {
        close(pipe->write_fd);
        pipe->write_closed = true;
        pipe->write_fd = INVALID_NATIVE_HANDLE;
    }
#endif
 
    free(pipe);
}
 
ProcessError pipe_close_read_end(PipeHandle* pipe) {
    if (!pipe) return PROCESS_ERROR_INVALID_ARGUMENT;
    if (pipe->read_fd != INVALID_NATIVE_HANDLE && !pipe->read_closed) {
#ifdef _WIN32
        CloseHandle(pipe->read_fd);
#else
        close(pipe->read_fd);
#endif
        pipe->read_closed = true;
        pipe->read_fd = INVALID_NATIVE_HANDLE;
    }
    return PROCESS_SUCCESS;
}
 
ProcessError pipe_close_write_end(PipeHandle* pipe) {
    if (!pipe) return PROCESS_ERROR_INVALID_ARGUMENT;
    if (pipe->write_fd != INVALID_NATIVE_HANDLE && !pipe->write_closed) {
#ifdef _WIN32
        CloseHandle(pipe->write_fd);
#else
        close(pipe->write_fd);
#endif
        pipe->write_closed = true;
        pipe->write_fd = INVALID_NATIVE_HANDLE;
    }
    return PROCESS_SUCCESS;
}
 
/* Implementation of the process API */
#ifdef _WIN32
 
static void append_escaped_win32_arg(char* dest, const char* arg) {
    /* Fast path: nothing that needs quoting */
    if (*arg != '\0' && !strpbrk(arg, " \t\n\v\"")) {
        strcat(dest, arg);
        return;
    }
 
    strcat(dest, "\"");
 
    for (const char* p = arg; *p != '\0';) {
        /* Count consecutive backslashes */
        int num_bs = 0;
        while (*p == '\\') {
            num_bs++;
            p++;
        }
 
        if (*p == '\0') {
            /* Trailing backslashes: double them before the closing quote */
            for (int k = 0; k < num_bs * 2; k++) strcat(dest, "\\");
            break;
        } else if (*p == '"') {
            /* Backslashes before a quote: double them, then escape the quote */
            for (int k = 0; k < num_bs * 2 + 1; k++) strcat(dest, "\\");
            strcat(dest, "\"");
            p++;
        } else {
            /* Literal backslashes followed by a normal char */
            for (int k = 0; k < num_bs; k++) strcat(dest, "\\");
            size_t len = strlen(dest);
            dest[len] = *p;
            dest[len + 1] = '\0';
            p++;
        }
    }
 
    strcat(dest, "\"");
}
 
static ProcessError win32_create_process(ProcessHandle** handle, const char* command, const char* const argv[],
                                         const ProcessOptions* options) {
    /* Calculate an upper-bound for the command-line buffer.
     * Each character can expand to at most 2 (backslash doubling) plus
     * 2 surrounding quotes + 1 space separator. */
    size_t cmdline_len = 0;
    int arg_count = 0;
 
    while (argv[arg_count] != NULL) {
        cmdline_len += strlen(argv[arg_count]) * 2 + 4; /* worst-case escaping */
        arg_count++;
    }
    if (arg_count == 0) {
        return PROCESS_ERROR_INVALID_ARGUMENT;
    }
 
    char* cmdline = (char*)malloc(cmdline_len + 1);
    if (!cmdline) {
        return PROCESS_ERROR_MEMORY;
    }
    cmdline[0] = '\0';
 
    for (int i = 0; i < arg_count; i++) {
        if (i > 0) strcat(cmdline, " ");
        append_escaped_win32_arg(cmdline, argv[i]);
    }
 
    /* Prepare startup info with redirections */
    STARTUPINFOA startup_info;
    memset(&startup_info, 0, sizeof(startup_info));
    startup_info.cb = sizeof(startup_info);
    startup_info.dwFlags = STARTF_USESTDHANDLES;
    startup_info.hStdInput = GetStdHandle(STD_INPUT_HANDLE);
    startup_info.hStdOutput = GetStdHandle(STD_OUTPUT_HANDLE);
    startup_info.hStdError = GetStdHandle(STD_ERROR_HANDLE);
 
    if (options->io.stdin_pipe) startup_info.hStdInput = options->io.stdin_pipe->read_fd;
    if (options->io.stdout_pipe) startup_info.hStdOutput = options->io.stdout_pipe->write_fd;
 
    if (options->io.stderr_pipe) {
        startup_info.hStdError = options->io.stderr_pipe->write_fd;
    } else if (options->io.merge_stderr) {
        startup_info.hStdError = startup_info.hStdOutput;
    }
 
    DWORD creation_flags = 0;
    if (options->detached) {
        creation_flags |= DETACHED_PROCESS | CREATE_NEW_PROCESS_GROUP;
    }
 
    PROCESS_INFORMATION process_info;
    BOOL success = CreateProcessA(command, cmdline, NULL, NULL, TRUE, creation_flags, (LPVOID)(options->environment),
                                  options->working_directory, &startup_info, &process_info);
 
    free(cmdline);
 
    if (!success) {
        return process_system_error();
    }
 
    *handle = (ProcessHandle*)malloc(sizeof(ProcessHandle));
    if (!*handle) {
        CloseHandle(process_info.hProcess);
        CloseHandle(process_info.hThread);
        return PROCESS_ERROR_MEMORY;
    }
 
    (*handle)->process_info = process_info;
    (*handle)->detached = options->detached;
 
    return PROCESS_SUCCESS;
}
#else
static ProcessError unix_create_process(ProcessHandle** handle, const char* command, const char* const argv[],
                                        const ProcessOptions* options) {
    // Create pipes for redirection if needed
    int stdin_pipe[2] = {-1, -1};
    int stdout_pipe[2] = {-1, -1};
    int stderr_pipe[2] = {-1, -1};
 
    // Set up pipes for redirections
    if (options->io.stdin_pipe) {
        stdin_pipe[0] = options->io.stdin_pipe->read_fd;
        stdin_pipe[1] = options->io.stdin_pipe->write_fd;
    }
 
    if (options->io.stdout_pipe) {
        stdout_pipe[0] = options->io.stdout_pipe->read_fd;
        stdout_pipe[1] = options->io.stdout_pipe->write_fd;
    }
 
    if (options->io.stderr_pipe) {
        stderr_pipe[0] = options->io.stderr_pipe->read_fd;
        stderr_pipe[1] = options->io.stderr_pipe->write_fd;
    }
 
    // Fork the process
    pid_t pid = fork();
 
    if (pid < 0) {
        return PROCESS_ERROR_FORK_FAILED;
    }
 
    if (pid == 0) {
        // Child process
 
        // Handle working directory
        if (options->working_directory) {
            if (chdir(options->working_directory) != 0) {
                _exit(127);
            }
        }
 
        // Handle standard input
        if (options->io.stdin_pipe) {
            dup2(stdin_pipe[0], STDIN_FILENO);
            close(stdin_pipe[0]);
            close(stdin_pipe[1]);
        }
 
        // Handle standard output
        if (options->io.stdout_pipe) {
            dup2(stdout_pipe[1], STDOUT_FILENO);
            close(stdout_pipe[0]);
            close(stdout_pipe[1]);
        }
 
        // Handle standard error
        if (options->io.stderr_pipe) {
            dup2(stderr_pipe[1], STDERR_FILENO);
            close(stderr_pipe[0]);
            close(stderr_pipe[1]);
        } else if (options->io.merge_stderr) {
            dup2(STDOUT_FILENO, STDERR_FILENO);
        }
 
        // Detach from parent if requested
        if (options->detached) {
            if (setsid() < 0) {
                _exit(127);
            }
        }
 
        // Execute the command
        if (options->inherit_environment) {
            execvp(command, (char* const*)argv);
        } else {
            // Custom or empty environment - need to search PATH manually
            const char* const* env = options->environment ? options->environment : (const char* const[]){NULL};
            char* cmd_path = find_in_path(command, env);
            if (cmd_path) {
                execve(cmd_path, (char* const*)argv, (char* const*)env);
                free(cmd_path);
            } else {
                // Try command as-is (might be absolute path)
                execve(command, (char* const*)argv, (char* const*)env);
            }
        }
 
        // If we get here, exec failed
        perror("execve");
        _exit(127);
    }
 
    // Parent process
    *handle = (ProcessHandle*)malloc(sizeof(ProcessHandle));
    if (!*handle) {
        return PROCESS_ERROR_MEMORY;
    }
 
    (*handle)->pid = pid;
    (*handle)->detached = options->detached;
 
    return PROCESS_SUCCESS;
}
#endif
 
ProcessError process_create(ProcessHandle** handle, const char* command, const char* const argv[],
                            const ProcessOptions* options) {
    if (!handle || !command || !argv || !argv[0]) {
        return PROCESS_ERROR_INVALID_ARGUMENT;
    }
 
    // Use default options if not provided
    ProcessOptions effective_options;
    if (options) {
        effective_options = *options;
    } else {
        effective_options = DEFAULT_OPTIONS;
    }
 
#ifdef _WIN32
    return win32_create_process(handle, command, argv, &effective_options);
#else
    return unix_create_process(handle, command, argv, &effective_options);
#endif
}
 
void process_free(ProcessHandle* handle) {
    if (!handle) return;
    free(handle);
}
 
#ifndef _WIN32
static inline void set_process_result(int status, ProcessResult* result) {
    if (WIFEXITED(status)) {
        result->exit_code = WEXITSTATUS(status);
        result->exited_normally = true;
    } else if (WIFSIGNALED(status)) {
        result->exit_code = WTERMSIG(status);
        result->exited_normally = false;
        result->term_signal = WTERMSIG(status);  // only set term_signal here
    } else {
        result->exit_code = -1;  // Undefined exit reason
        result->exited_normally = false;
    }
}
#endif
 
// Cross-platform nanosleep function
void NANOSLEEP(long seconds, long nanoseconds) {
#ifdef _WIN32
    // On Windows, Sleep works in milliseconds,
    // so we convert seconds and nanoseconds to milliseconds
    unsigned long total_milliseconds = (unsigned)(seconds * 1000 + nanoseconds / 1000000);
    Sleep(total_milliseconds);
#else
    // On Linux/Unix, we can use nanosleep directly
    struct timespec req;
    req.tv_sec = seconds;
    req.tv_nsec = nanoseconds;
    nanosleep(&req, NULL);
#endif
}
 
ProcessError process_wait(ProcessHandle* handle, ProcessResult* result, int timeout_ms) {
    if (!handle) {
        return PROCESS_ERROR_INVALID_ARGUMENT;
    }
 
    if (handle->detached) {
        // Cannot wait for detached processes
        return PROCESS_ERROR_INVALID_ARGUMENT;
    }
 
#ifdef _WIN32
    // Windows-specific code
    DWORD wait_result =
        WaitForSingleObject(handle->process_info.hProcess, timeout_ms < 0 ? INFINITE : (DWORD)timeout_ms);
 
    if (wait_result == WAIT_TIMEOUT) {
        return PROCESS_ERROR_WAIT_FAILED;
    } else if (wait_result != WAIT_OBJECT_0) {
        return process_system_error();
    }
 
    if (result) {
        DWORD exit_code;
        if (!GetExitCodeProcess(handle->process_info.hProcess, &exit_code)) {
            return process_system_error();
        }
 
        result->exit_code = (int)exit_code;
        result->exited_normally = true;
        result->term_signal = 0;  // No signal on Windows
    }
#else
    // Linux/Unix-specific code
    int status = 0;
    pid_t wait_result = 0;
 
    if (timeout_ms < 0) {
        // Wait indefinitely
        wait_result = waitpid(handle->pid, &status, 0);
    } else {
        // Wait with timeout using WNOHANG and a busy-wait loop for the timeout
        int remaining_timeout_ms = timeout_ms;
 
        // Here, we wait in a loop until the process exits or the timeout is reached
        while ((wait_result = waitpid(handle->pid, &status, WNOHANG)) == 0 && remaining_timeout_ms > 0) {
            struct timespec ts;
            ts.tv_sec = remaining_timeout_ms / 1000;
            ts.tv_nsec = (remaining_timeout_ms % 1000) * 1000000L;
 
            // Sleep for the remaining timeout duration
            NANOSLEEP(ts.tv_sec, ts.tv_nsec);
 
            // Adjust remaining timeout
            remaining_timeout_ms -= (int)((ts.tv_sec * 1000) + (ts.tv_nsec / 1000000));
        }
    }
 
    if (wait_result < 0) {
        return process_system_error();
    }
 
    if (wait_result == 0) {
        // Process is still running
        return PROCESS_ERROR_WAIT_FAILED;
    }
 
    if (result) {
        set_process_result(status, result);
    }
 
#endif
    return PROCESS_SUCCESS;
}
 
ProcessError process_terminate(ProcessHandle* handle, bool force) {
    if (!handle) {
        return PROCESS_ERROR_INVALID_ARGUMENT;
    }
#ifdef _WIN32
    if (force) {
        // Force termination using TerminateProcess (like SIGKILL)
        if (!TerminateProcess(handle->process_info.hProcess, 1)) {
            return PROCESS_ERROR_TERMINATE_FAILED;
        }
    } else {
        // Graceful termination using GenerateConsoleCtrlEvent or other method
        // GenerateCtrlEvent is typically used for console processes
        if (!GenerateConsoleCtrlEvent(CTRL_C_EVENT, 0)) {
            return PROCESS_ERROR_TERMINATE_FAILED;
        }
    }
#else
    if (handle->pid <= 0) {
        return PROCESS_ERROR_INVALID_ARGUMENT;
    }
 
    if (force) {
        // Force termination using SIGKILL (immediate termination)
        if (kill(handle->pid, SIGKILL) != 0) {
            return PROCESS_ERROR_KILL_FAILED;
        }
    } else {
        // Graceful termination using SIGTERM (request termination)
        if (kill(handle->pid, SIGTERM) != 0) {
            return PROCESS_ERROR_KILL_FAILED;
        }
    }
#endif
    return PROCESS_SUCCESS;
}
 
ProcessError process_run_and_capture(const char* command, const char* const argv[], ProcessOptions* options,
                                     int* exit_code) {
    ProcessHandle* proc = NULL;
    ProcessError err = {0};
    err = process_create(&proc, command, argv, options);
    if (err != PROCESS_SUCCESS) {
        return err;
    }
 
    ProcessResult res = {0};
    err = process_wait(proc, &res, -1);
    process_free(proc);
 
    if (exit_code) {
        *exit_code = res.exit_code;
    }
 
    if (err != PROCESS_SUCCESS) {
        return err;
    }
 
    if (res.exit_code != 0) {
        return PROCESS_ERROR_EXEC_FAILED;
    }
    return PROCESS_SUCCESS;
}
 
#ifndef _WIN32
// ======== Redirection ==================
ProcessError process_redirect_to_file(FileRedirection** redirection, const char* filepath, int flags,
                                      unsigned int mode) {
    if (!redirection || !filepath) {
        return PROCESS_ERROR_INVALID_ARGUMENT;
    }
 
    *redirection = (FileRedirection*)malloc(sizeof(FileRedirection));
    if (!*redirection) {
        return PROCESS_ERROR_MEMORY;
    }
 
    // Open the file with the specified flags and mode
    int fd = open(filepath, flags, mode);
    if (fd < 0) {
        free(*redirection);
        *redirection = NULL;
        return process_system_error();
    }
 
    (*redirection)->fd = fd;
    (*redirection)->close_on_exec = true;
 
    return PROCESS_SUCCESS;
}
 
ProcessError process_redirect_to_fd(FileRedirection** redirection, int fd, bool close_on_exec) {
    if (!redirection || fd < 0) {
        return PROCESS_ERROR_INVALID_ARGUMENT;
    }
 
    *redirection = (FileRedirection*)malloc(sizeof(FileRedirection));
    if (!*redirection) {
        return PROCESS_ERROR_MEMORY;
    }
 
    (*redirection)->fd = fd;
    (*redirection)->close_on_exec = close_on_exec;
 
    return PROCESS_SUCCESS;
}
 
void process_close_redirection(FileRedirection* redirection) {
    if (!redirection) {
        return;
    }
 
    if (redirection->close_on_exec && redirection->fd >= 0) {
        close(redirection->fd);
    }
 
    free(redirection);
    redirection = NULL;
}
 
ProcessError process_create_with_redirection(ProcessHandle** handle, const char* command, const char* const argv[],
                                             const ExtProcessOptions* options) {
    if (!handle || !command || !argv || !argv[0]) {
        return PROCESS_ERROR_INVALID_ARGUMENT;
    }
    // Fork the process
    pid_t pid = fork();
 
    if (pid < 0) {
        return PROCESS_ERROR_FORK_FAILED;
    }
 
    if (pid == 0) {
        // Child process
 
        // Handle working directory
        if (options->working_directory) {
            if (chdir(options->working_directory) != 0) {
                _exit(127);
            }
        }
 
        // Handle standard input
        if (options->io.stdin_pipe) {
            if (dup2(options->io.stdin_pipe->read_fd, STDIN_FILENO) == -1) {
                perror("dup2");
                return PROCESS_ERROR_IO;
            };
 
            // Close pipe handles that aren't needed in child
            close(options->io.stdin_pipe->read_fd);
            close(options->io.stdin_pipe->write_fd);
        }
 
        // Handle standard output
        if (options->io.stdout_pipe) {
            if (dup2(options->io.stdout_pipe->write_fd, STDOUT_FILENO) == -1) {
                perror("dup2");
                return PROCESS_ERROR_IO;
            };
            close(options->io.stdout_pipe->read_fd);
            close(options->io.stdout_pipe->write_fd);
        } else if (options->io.stdout_file) {
            // Redirect stdout to file
            if (dup2(options->io.stdout_file->fd, STDOUT_FILENO) == -1) {
                perror("dup2");
                return PROCESS_ERROR_IO;
            };
            if (options->io.stdout_file->close_on_exec) {
                close(options->io.stdout_file->fd);
            }
        }
 
        // Handle standard error
        if (options->io.stderr_pipe) {
            if (dup2(options->io.stderr_pipe->write_fd, STDERR_FILENO) == -1) {
                perror("dup2");
                return PROCESS_ERROR_IO;
            };
            close(options->io.stderr_pipe->read_fd);
            close(options->io.stderr_pipe->write_fd);
        } else if (options->io.stderr_file) {
            // Redirect stderr to file
            if (dup2(options->io.stderr_file->fd, STDERR_FILENO) == -1) {
                perror("dup2");
                return PROCESS_ERROR_IO;
            };
            if (options->io.stderr_file->close_on_exec) {
                close(options->io.stderr_file->fd);
            }
        } else if (options->io.merge_stderr) {
            if (dup2(STDOUT_FILENO, STDERR_FILENO) == -1) {
                perror("dup2");
                return PROCESS_ERROR_IO;
            };
        }
 
        // Detach from parent if requested
        if (options->detached) {
            if (setsid() < 0) {
                _exit(127);
            }
        }
 
        // Execute the command
        if (options->environment) {
            if (execve(command, (char* const*)argv, (char* const*)options->environment) == -1) {
                perror("execve");
            };
        } else if (options->inherit_environment) {
            if (execvp(command, (char* const*)argv) == -1) {
                perror("execvp");
            };
        } else {
            char* empty_env[] = {NULL};
            if (execve(command, (char* const*)argv, empty_env) == -1) {
                perror("execve");
            };
        }
 
        // If we get here, exec failed
        _exit(127);
    }
 
    // Parent process
    *handle = (ProcessHandle*)malloc(sizeof(ProcessHandle));
    if (!*handle) {
        return PROCESS_ERROR_MEMORY;
    }
 
    (*handle)->pid = pid;
    (*handle)->detached = options->detached;
 
    return PROCESS_SUCCESS;
}
 
ProcessError process_run_with_multiwriter(ProcessResult* result, const char* cmd, const char* args[], int output_fds[],
                                          int error_fds[]) {
    // Create pipes for stdout and stderr
    int stdout_pipe[2];
    int stderr_pipe[2];
 
    // Create a pipe for stdout
    if (pipe(stdout_pipe) < 0) {
        perror("pipe (stdout)");
        return PROCESS_ERROR_PIPE_FAILED;
    }
 
    // Create a pipe for stderr
    if (pipe(stderr_pipe) < 0) {
        perror("pipe (stderr)");
        // Clean up stdout pipe if stderr pipe creation fails
        close(stdout_pipe[0]);
        close(stdout_pipe[1]);
        return PROCESS_ERROR_PIPE_FAILED;
    }
 
    // Fork the child process that will execute the command
    pid_t cmd_pid = fork();
    if (cmd_pid < 0) {
        perror("fork");
        // Clean up pipes if fork fails
        close(stdout_pipe[0]);
        close(stdout_pipe[1]);
        close(stderr_pipe[0]);
        close(stderr_pipe[1]);
        return PROCESS_ERROR_FORK_FAILED;
    }
 
    if (cmd_pid == 0) {  // Command process
        // Close read ends of the pipes (not needed in the command process)
        close(stdout_pipe[0]);
        close(stderr_pipe[0]);
 
        // Redirect stdout to the write end of the stdout pipe
        if (dup2(stdout_pipe[1], STDOUT_FILENO) < 0) {
            perror("dup2 (stdout)");
            exit(EXIT_FAILURE);
        }
 
        // Redirect stderr to the write end of the stderr pipe
        if (dup2(stderr_pipe[1], STDERR_FILENO) < 0) {
            perror("dup2 (stderr)");
            exit(EXIT_FAILURE);
        }
 
        // Close the write ends of the pipes (they are now duplicated to
        // stdout/stderr)
        close(stdout_pipe[1]);
        close(stderr_pipe[1]);
 
        // Execute the command
        execv(cmd, (char* const*)args);
        // If execv fails, print an error and exit
        perror("execv");
        exit(EXIT_FAILURE);
    }
 
    // Parent process
    // Close write ends of the pipes (not needed in the parent process)
    close(stdout_pipe[1]);
    close(stderr_pipe[1]);
 
    int child_count = 1;  // Start with 1 for the command process
 
    // Fork a single tee process for stdout that writes to all output_fds
    pid_t stdout_tee_pid = fork();
    if (stdout_tee_pid < 0) {
        perror("fork tee (stdout)");
        // Clean up pipes and wait for the command process if fork fails
        close(stdout_pipe[0]);
        close(stderr_pipe[0]);
        waitpid(cmd_pid, NULL, 0);  // Wait for the command process to avoid zombies
        return PROCESS_ERROR_FORK_FAILED;
    }
 
    if (stdout_tee_pid == 0) {  // Tee child process for stdout
        char buffer[4096];
        ssize_t n = 0;
 
        // Read from the stdout pipe and write to all output_fds
        while ((n = read(stdout_pipe[0], buffer, sizeof(buffer))) > 0) {
            for (int i = 0; output_fds[i] != -1; i++) {
                if (write(output_fds[i], buffer, (size_t)n) < 0) {
                    perror("write (stdout tee)");
                    exit(EXIT_FAILURE);
                }
            }
        }
 
        // Check for read errors
        if (n < 0) {
            perror("read (stdout tee)");
            exit(EXIT_FAILURE);
        }
 
        exit(EXIT_SUCCESS);
    }
 
    child_count++;
 
    // Fork a single tee process for stderr that writes to all error_fds
    pid_t stderr_tee_pid = fork();
    if (stderr_tee_pid < 0) {
        perror("fork tee (stderr)");
        // Clean up pipes and wait for the command and stdout tee processes if fork
        // fails
        close(stdout_pipe[0]);
        close(stderr_pipe[0]);
        waitpid(cmd_pid, NULL, 0);         // Wait for the command process
        waitpid(stdout_tee_pid, NULL, 0);  // Wait for the stdout tee process
        return PROCESS_ERROR_FORK_FAILED;
    }
 
    if (stderr_tee_pid == 0) {  // Tee child process for stderr
        char buffer[4096];
        ssize_t n = 0;
 
        // Read from the stderr pipe and write to all error_fds
        while ((n = read(stderr_pipe[0], buffer, sizeof(buffer))) > 0) {
            for (int i = 0; error_fds[i] != -1; i++) {
                if (write(error_fds[i], buffer, (size_t)n) < 0) {
                    perror("write (stderr tee)");
                    exit(EXIT_FAILURE);
                }
            }
        }
 
        // Check for read errors
        if (n < 0) {
            perror("read (stderr tee)");
            exit(EXIT_FAILURE);
        }
 
        exit(EXIT_SUCCESS);
    }
 
    child_count++;
 
    // Close read ends of the pipes after all tee processes are started
    close(stdout_pipe[0]);
    close(stderr_pipe[0]);
 
    // Wait for the command process specifically to get its status
    int cmd_status = 0;
    waitpid(cmd_pid, &cmd_status, 0);
    set_process_result(cmd_status, result);
 
    // Wait for all remaining child processes (stdout and stderr tee processes)
    while (child_count > 1) {
        wait(NULL);
        child_count--;
    }
 
    // Check if the command process exited successfully
    if (WIFEXITED(cmd_status)) {
        return PROCESS_SUCCESS;
    } else {
        return PROCESS_ERROR_EXEC_FAILED;
    }
}
 
ProcessError process_run_with_file_redirection(ProcessHandle** handle, const char* command, const char* const argv[],
                                               const char* stdout_file, const char* stderr_file, bool append) {
    ExtProcessOptions options;
    memset(&options, 0, sizeof(options));
    options.inherit_environment = true;
 
    FileRedirection* stdout_redir = NULL;
    FileRedirection* stderr_redir = NULL;
    ProcessError err = PROCESS_SUCCESS;
 
    if (stdout_file) {
        int flags = O_WRONLY | O_CREAT;
        flags |= (append ? O_APPEND : O_TRUNC);
 
        err = process_redirect_to_file(&stdout_redir, stdout_file, flags, 0644);
        if (err != PROCESS_SUCCESS) {
            return err;
        }
        options.io.stdout_file = stdout_redir;
    }
 
    if (stderr_file) {
        int flags = O_WRONLY | O_CREAT;
        flags |= (append ? O_APPEND : O_TRUNC);
 
        err = process_redirect_to_file(&stderr_redir, stderr_file, flags, 0644);
        if (err != PROCESS_SUCCESS) {
            if (stdout_redir) {
                process_close_redirection(stdout_redir);
            }
            return err;
        }
        options.io.stderr_file = stderr_redir;
    }
 
    // Create the process with redirection
    err = process_create_with_redirection(handle, command, argv, &options);
 
    // Clean up redirections
    if (stdout_redir) {
        process_close_redirection(stdout_redir);
    }
 
    if (stderr_redir) {
        process_close_redirection(stderr_redir);
    }
 
    return err;
}
 
#endif  // Linux only