nobuild.h

#ifndef NOBUILD_H_
#define NOBUILD_H_

#ifndef _WIN32
#    define _POSIX_C_SOURCE 200809L
#    include <sys/types.h>
#    include <sys/wait.h>
#    include <sys/stat.h>
#    include <unistd.h>
#    include <dirent.h>
#    include <fcntl.h>
#    define PATH_SEP "/"
typedef pid_t Pid;
typedef int Fd;
#else
#    define WIN32_MEAN_AND_LEAN
#    include "windows.h"
#    include <process.h>
#    define PATH_SEP "\\"
typedef HANDLE Pid;
typedef HANDLE Fd;
// minirent.h HEADER BEGIN ////////////////////////////////////////
// Copyright 2021 Alexey Kutepov <reximkut@gmail.com>
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//
// ============================================================
//
// minirent — 0.0.1 — A subset of dirent interface for Windows.
//
// https://github.com/tsoding/minirent
//
// ============================================================
//
// ChangeLog (https://semver.org/ is implied)
//
//    0.0.1 First Official Release

#ifndef MINIRENT_H_
#define MINIRENT_H_

#define WIN32_LEAN_AND_MEAN
#include "windows.h"

struct dirent {
    char d_name[MAX_PATH+1];
};

typedef struct DIR DIR;

DIR *opendir(const char *dirpath);
struct dirent *readdir(DIR *dirp);
int closedir(DIR *dirp);

#endif  // MINIRENT_H_
// minirent.h HEADER END ////////////////////////////////////////

// TODO(#28): use GetLastErrorAsString everywhere on Windows error reporting
LPSTR GetLastErrorAsString(void);

#endif  // _WIN32

#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <string.h>
#include <errno.h>

#define FOREACH_ARRAY(type, elem, array, body)  \
    for (size_t elem_##index = 0;                           \
         elem_##index < array.count;                        \
         ++elem_##index)                                    \
    {                                                       \
        type *elem = &array.elems[elem_##index];            \
        body;                                               \
    }

typedef const char * Cstr;

int cstr_ends_with(Cstr cstr, Cstr postfix);
#define ENDS_WITH(cstr, postfix) cstr_ends_with(cstr, postfix)

Cstr cstr_no_ext(Cstr path);
#define NOEXT(path) cstr_no_ext(path)

typedef struct {
    Cstr *elems;
    size_t count;
} Cstr_Array;

Cstr_Array cstr_array_make(Cstr first, ...);
Cstr_Array cstr_array_append(Cstr_Array cstrs, Cstr cstr);
Cstr cstr_array_join(Cstr sep, Cstr_Array cstrs);

#define JOIN(sep, ...) cstr_array_join(sep, cstr_array_make(__VA_ARGS__, NULL))
#define CONCAT(...) JOIN("", __VA_ARGS__)
#define PATH(...) JOIN(PATH_SEP, __VA_ARGS__)

typedef struct {
    Fd read;
    Fd write;
} Pipe;

Pipe pipe_make(void);

typedef struct {
    Cstr_Array line;
} Cmd;

Fd fd_open_for_read(Cstr path);
Fd fd_open_for_write(Cstr path);
void fd_close(Fd fd);
void pid_wait(Pid pid);
Cstr cmd_show(Cmd cmd);
Pid cmd_run_async(Cmd cmd, Fd *fdin, Fd *fdout);
void cmd_run_sync(Cmd cmd);

typedef struct {
    Cmd *elems;
    size_t count;
} Cmd_Array;

// TODO(#1): no way to disable echo in nobuild scripts
// TODO(#2): no way to ignore fails
#define CMD(...)                                        \
    do {                                                \
        Cmd cmd = {                                     \
            .line = cstr_array_make(__VA_ARGS__, NULL)  \
        };                                              \
        INFO("CMD: %s", cmd_show(cmd));                 \
        cmd_run_sync(cmd);                              \
    } while (0)

typedef enum {
    CHAIN_TOKEN_END = 0,
    CHAIN_TOKEN_IN,
    CHAIN_TOKEN_OUT,
    CHAIN_TOKEN_CMD
} Chain_Token_Type;

// A single token for the CHAIN(...) DSL syntax
typedef struct {
    Chain_Token_Type type;
    Cstr_Array args;
} Chain_Token;

// TODO(#17): IN and OUT are already taken by WinAPI
#define IN(path) \
    (Chain_Token) { \
        .type = CHAIN_TOKEN_IN, \
        .args = cstr_array_make(path, NULL) \
    }

#define OUT(path) \
    (Chain_Token) { \
        .type = CHAIN_TOKEN_OUT, \
        .args = cstr_array_make(path, NULL) \
    }

#define CHAIN_CMD(...) \
    (Chain_Token) { \
        .type = CHAIN_TOKEN_CMD, \
        .args = cstr_array_make(__VA_ARGS__, NULL) \
    }

// TODO(#20): pipes do not allow redirecting stderr
typedef struct {
    Cstr input_filepath;
    Cmd_Array cmds;
    Cstr output_filepath;
} Chain;

Chain chain_build_from_tokens(Chain_Token first, ...);
void chain_run_sync(Chain chain);
void chain_echo(Chain chain);

// TODO(#15): PIPE does not report where exactly a syntactic error has happened
#define CHAIN(...)                                                      \
    do {                                                                \
        Chain chain = chain_build_from_tokens(__VA_ARGS__, (Chain_Token) {0}); \
        chain_echo(chain);                                              \
        chain_run_sync(chain);                                          \
    } while(0)

#ifndef REBUILD_URSELF
#  if _WIN32
#    if defined(__GNUC__)
#       define REBUILD_URSELF(binary_path, source_path) CMD("gcc", "-o", binary_path, source_path)
#    elif defined(__clang__)
#       define REBUILD_URSELF(binary_path, source_path) CMD("clang", "-o", binary_path, source_path)
#    elif defined(_MSC_VER)
#       define REBUILD_URSELF(binary_path, source_path) CMD("cl.exe", source_path)
#    endif
#  else
#    define REBUILD_URSELF(binary_path, source_path) CMD("cc", "-o", binary_path, source_path)
#  endif
#endif

// Go Rebuild Urself™ Technology
//
//   How to use it:
//     int main(int argc, char** argv) {
//         GO_REBUILD_URSELF(argc, argv);
//         // actual work
//         return 0;
//     }
//
//   After your added this macro every time you run ./nobuild it will detect
//   that you modified its original source code and will try to rebuild itself
//   before doing any actual work. So you only need to bootstrap your build system
//   once.
//
//   The modification is detected by comparing the last modified times of the executable
//   and its source code. The same way the make utility usually does it.
//
//   The rebuilding is done by using the REBUILD_URSELF macro which you can redefine
//   if you need a special way of bootstraping your build system. (which I personally
//   do not recommend since the whole idea of nobuild is to keep the process of bootstrapping
//   as simple as possible and doing all of the actual work inside of the nobuild)
//
#define GO_REBUILD_URSELF(argc, argv)                                  \
    do {                                                               \
        const char *source_path = __FILE__;                            \
        assert(argc >= 1);                                             \
        const char *binary_path = argv[0];                             \
                                                                       \
        if (is_path1_modified_after_path2(source_path, binary_path)) { \
            RENAME(binary_path, CONCAT(binary_path, ".old"));          \
            REBUILD_URSELF(binary_path, source_path);                  \
            Cmd cmd = {                                                \
                .line = {                                              \
                    .elems = (Cstr*) argv,                             \
                    .count = argc,                                     \
                },                                                     \
            };                                                         \
            INFO("CMD: %s", cmd_show(cmd));                            \
            cmd_run_sync(cmd);                                         \
            exit(0);                                                   \
        }                                                              \
    } while(0)
// The implementation idea is stolen from https://github.com/zhiayang/nabs

void rebuild_urself(const char *binary_path, const char *source_path);

int path_is_dir(Cstr path);
#define IS_DIR(path) path_is_dir(path)

int path_exists(Cstr path);
#define PATH_EXISTS(path) path_exists(path)

void path_mkdirs(Cstr_Array path);
#define MKDIRS(...)                                             \
    do {                                                        \
        Cstr_Array path = cstr_array_make(__VA_ARGS__, NULL);   \
        INFO("MKDIRS: %s", cstr_array_join(PATH_SEP, path));    \
        path_mkdirs(path);                                      \
    } while (0)

void path_rename(Cstr old_path, Cstr new_path);
#define RENAME(old_path, new_path)                    \
    do {                                              \
        INFO("RENAME: %s -> %s", old_path, new_path); \
        path_rename(old_path, new_path);              \
    } while (0)

void path_rm(Cstr path);
#define RM(path)                                \
    do {                                        \
        INFO("RM: %s", path);                   \
        path_rm(path);                          \
    } while(0)

#define FOREACH_FILE_IN_DIR(file, dirpath, body)        \
    do {                                                \
        struct dirent *dp = NULL;                       \
        DIR *dir = opendir(dirpath);                    \
        if (dir == NULL) {                              \
            PANIC("could not open directory %s: %s",    \
                  dirpath, strerror(errno));            \
        }                                               \
        errno = 0;                                      \
        while ((dp = readdir(dir))) {                   \
            const char *file = dp->d_name;              \
            body;                                       \
        }                                               \
                                                        \
        if (errno > 0) {                                \
            PANIC("could not read directory %s: %s",    \
                  dirpath, strerror(errno));            \
        }                                               \
                                                        \
        closedir(dir);                                  \
    } while(0)

#if defined(__GNUC__) || defined(__clang__)
// https://gcc.gnu.org/onlinedocs/gcc-4.7.2/gcc/Function-Attributes.html
#define NOBUILD_PRINTF_FORMAT(STRING_INDEX, FIRST_TO_CHECK) __attribute__ ((format (printf, STRING_INDEX, FIRST_TO_CHECK)))
#else
#define NOBUILD_PRINTF_FORMAT(STRING_INDEX, FIRST_TO_CHECK)
#endif

void VLOG(FILE *stream, Cstr tag, Cstr fmt, va_list args);
void INFO(Cstr fmt, ...) NOBUILD_PRINTF_FORMAT(1, 2);
void WARN(Cstr fmt, ...) NOBUILD_PRINTF_FORMAT(1, 2);
void ERRO(Cstr fmt, ...) NOBUILD_PRINTF_FORMAT(1, 2);
void PANIC(Cstr fmt, ...) NOBUILD_PRINTF_FORMAT(1, 2);

char *shift_args(int *argc, char ***argv);

#endif  // NOBUILD_H_

////////////////////////////////////////////////////////////////////////////////

#ifdef NOBUILD_IMPLEMENTATION

#ifdef _WIN32
LPSTR GetLastErrorAsString(void)
{
    // https://stackoverflow.com/questions/1387064/how-to-get-the-error-message-from-the-error-code-returned-by-getlasterror

    DWORD errorMessageId = GetLastError();
    assert(errorMessageId != 0);

    LPSTR messageBuffer = NULL;

    DWORD size =
        FormatMessage(
            FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS, // DWORD   dwFlags,
            NULL, // LPCVOID lpSource,
            errorMessageId, // DWORD   dwMessageId,
            MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), // DWORD   dwLanguageId,
            (LPSTR) &messageBuffer, // LPTSTR  lpBuffer,
            0, // DWORD   nSize,
            NULL // va_list *Arguments
        );

    return messageBuffer;
}

// minirent.h IMPLEMENTATION BEGIN ////////////////////////////////////////
struct DIR {
    HANDLE hFind;
    WIN32_FIND_DATA data;
    struct dirent *dirent;
};

DIR *opendir(const char *dirpath)
{
    assert(dirpath);

    char buffer[MAX_PATH];
    snprintf(buffer, MAX_PATH, "%s\\*", dirpath);

    DIR *dir = (DIR*)calloc(1, sizeof(DIR));

    dir->hFind = FindFirstFile(buffer, &dir->data);
    if (dir->hFind == INVALID_HANDLE_VALUE) {
        errno = ENOSYS;
        goto fail;
    }

    return dir;

fail:
    if (dir) {
        free(dir);
    }

    return NULL;
}

struct dirent *readdir(DIR *dirp)
{
    assert(dirp);

    if (dirp->dirent == NULL) {
        dirp->dirent = (struct dirent*)calloc(1, sizeof(struct dirent));
    } else {
        if(!FindNextFile(dirp->hFind, &dirp->data)) {
            if (GetLastError() != ERROR_NO_MORE_FILES) {
                errno = ENOSYS;
            }

            return NULL;
        }
    }

    memset(dirp->dirent->d_name, 0, sizeof(dirp->dirent->d_name));

    strncpy(
        dirp->dirent->d_name,
        dirp->data.cFileName,
        sizeof(dirp->dirent->d_name) - 1);

    return dirp->dirent;
}

int closedir(DIR *dirp)
{
    assert(dirp);

    if(!FindClose(dirp->hFind)) {
        errno = ENOSYS;
        return -1;
    }

    if (dirp->dirent) {
        free(dirp->dirent);
    }
    free(dirp);

    return 0;
}
// minirent.h IMPLEMENTATION END ////////////////////////////////////////
#endif // _WIN32

Cstr_Array cstr_array_append(Cstr_Array cstrs, Cstr cstr)
{
    Cstr_Array result = {
        .count = cstrs.count + 1
    };
    result.elems = malloc(sizeof(result.elems[0]) * result.count);
    memcpy(result.elems, cstrs.elems, cstrs.count * sizeof(result.elems[0]));
    result.elems[cstrs.count] = cstr;
    return result;
}

int cstr_ends_with(Cstr cstr, Cstr postfix)
{
    const size_t cstr_len = strlen(cstr);
    const size_t postfix_len = strlen(postfix);
    return postfix_len <= cstr_len
           && strcmp(cstr + cstr_len - postfix_len, postfix) == 0;
}

Cstr cstr_no_ext(Cstr path)
{
    size_t n = strlen(path);
    while (n > 0 && path[n - 1] != '.') {
        n -= 1;
    }

    if (n > 0) {
        char *result = malloc(n);
        memcpy(result, path, n);
        result[n - 1] = '\0';

        return result;
    } else {
        return path;
    }
}

Cstr_Array cstr_array_make(Cstr first, ...)
{
    Cstr_Array result = {0};

    if (first == NULL) {
        return result;
    }

    result.count += 1;

    va_list args;
    va_start(args, first);
    for (Cstr next = va_arg(args, Cstr);
            next != NULL;
            next = va_arg(args, Cstr)) {
        result.count += 1;
    }
    va_end(args);

    result.elems = malloc(sizeof(result.elems[0]) * result.count);
    if (result.elems == NULL) {
        PANIC("could not allocate memory: %s", strerror(errno));
    }
    result.count = 0;

    result.elems[result.count++] = first;

    va_start(args, first);
    for (Cstr next = va_arg(args, Cstr);
            next != NULL;
            next = va_arg(args, Cstr)) {
        result.elems[result.count++] = next;
    }
    va_end(args);

    return result;
}

Cstr cstr_array_join(Cstr sep, Cstr_Array cstrs)
{
    if (cstrs.count == 0) {
        return "";
    }

    const size_t sep_len = strlen(sep);
    size_t len = 0;
    for (size_t i = 0; i < cstrs.count; ++i) {
        len += strlen(cstrs.elems[i]);
    }

    const size_t result_len = (cstrs.count - 1) * sep_len + len + 1;
    char *result = malloc(sizeof(char) * result_len);
    if (result == NULL) {
        PANIC("could not allocate memory: %s", strerror(errno));
    }

    len = 0;
    for (size_t i = 0; i < cstrs.count; ++i) {
        if (i > 0) {
            memcpy(result + len, sep, sep_len);
            len += sep_len;
        }

        size_t elem_len = strlen(cstrs.elems[i]);
        memcpy(result + len, cstrs.elems[i], elem_len);
        len += elem_len;
    }
    result[len] = '\0';

    return result;
}

Pipe pipe_make(void)
{
    Pipe pip = {0};

#ifdef _WIN32
    // https://docs.microsoft.com/en-us/windows/win32/ProcThread/creating-a-child-process-with-redirected-input-and-output

    SECURITY_ATTRIBUTES saAttr = {0};
    saAttr.nLength = sizeof(SECURITY_ATTRIBUTES);
    saAttr.bInheritHandle = TRUE;

    if (!CreatePipe(&pip.read, &pip.write, &saAttr, 0)) {
        PANIC("Could not create pipe: %s", GetLastErrorAsString());
    }
#else
    Fd pipefd[2];
    if (pipe(pipefd) < 0) {
        PANIC("Could not create pipe: %s", strerror(errno));
    }

    pip.read = pipefd[0];
    pip.write = pipefd[1];
#endif // _WIN32

    return pip;
}

Fd fd_open_for_read(Cstr path)
{
#ifndef _WIN32
    Fd result = open(path, O_RDONLY);
    if (result < 0) {
        PANIC("Could not open file %s: %s", path, strerror(errno));
    }
    return result;
#else
    // https://docs.microsoft.com/en-us/windows/win32/fileio/opening-a-file-for-reading-or-writing
    SECURITY_ATTRIBUTES saAttr = {0};
    saAttr.nLength = sizeof(SECURITY_ATTRIBUTES);
    saAttr.bInheritHandle = TRUE;

    Fd result = CreateFile(
                    path,
                    GENERIC_READ,
                    0,
                    &saAttr,
                    OPEN_EXISTING,
                    FILE_ATTRIBUTE_READONLY,
                    NULL);

    if (result == INVALID_HANDLE_VALUE) {
        PANIC("Could not open file %s", path);
    }

    return result;
#endif // _WIN32
}

Fd fd_open_for_write(Cstr path)
{
#ifndef _WIN32
    Fd result = open(path,
                     O_WRONLY | O_CREAT | O_TRUNC,
                     S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
    if (result < 0) {
        PANIC("could not open file %s: %s", path, strerror(errno));
    }
    return result;
#else
    SECURITY_ATTRIBUTES saAttr = {0};
    saAttr.nLength = sizeof(SECURITY_ATTRIBUTES);
    saAttr.bInheritHandle = TRUE;

    Fd result = CreateFile(
                    path,                  // name of the write
                    GENERIC_WRITE,         // open for writing
                    0,                     // do not share
                    &saAttr,               // default security
                    CREATE_NEW,            // create new file only
                    FILE_ATTRIBUTE_NORMAL, // normal file
                    NULL                   // no attr. template
                );

    if (result == INVALID_HANDLE_VALUE) {
        PANIC("Could not open file %s: %s", path, GetLastErrorAsString());
    }

    return result;
#endif // _WIN32
}

void fd_close(Fd fd)
{
#ifdef _WIN32
    CloseHandle(fd);
#else
    close(fd);
#endif // _WIN32
}

void pid_wait(Pid pid)
{
#ifdef _WIN32
    DWORD result = WaitForSingleObject(
                       pid,     // HANDLE hHandle,
                       INFINITE // DWORD  dwMilliseconds
                   );

    if (result == WAIT_FAILED) {
        PANIC("could not wait on child process: %s", GetLastErrorAsString());
    }

    DWORD exit_status;
    if (GetExitCodeProcess(pid, &exit_status) == 0) {
        PANIC("could not get process exit code: %lu", GetLastError());
    }

    if (exit_status != 0) {
        PANIC("command exited with exit code %lu", exit_status);
    }

    CloseHandle(pid);
#else
    for (;;) {
        int wstatus = 0;
        if (waitpid(pid, &wstatus, 0) < 0) {
            PANIC("could not wait on command (pid %d): %s", pid, strerror(errno));
        }

        if (WIFEXITED(wstatus)) {
            int exit_status = WEXITSTATUS(wstatus);
            if (exit_status != 0) {
                PANIC("command exited with exit code %d", exit_status);
            }

            break;
        }

        if (WIFSIGNALED(wstatus)) {
            PANIC("command process was terminated by %s", strsignal(WTERMSIG(wstatus)));
        }
    }

#endif // _WIN32
}

Cstr cmd_show(Cmd cmd)
{
    // TODO(#31): cmd_show does not render the command line properly
    // - No string literals when arguments contains space
    // - No escaping of special characters
    // - Etc.
    return cstr_array_join(" ", cmd.line);
}

Pid cmd_run_async(Cmd cmd, Fd *fdin, Fd *fdout)
{
#ifdef _WIN32
    // https://docs.microsoft.com/en-us/windows/win32/procthread/creating-a-child-process-with-redirected-input-and-output

    STARTUPINFO siStartInfo;
    ZeroMemory(&siStartInfo, sizeof(siStartInfo));
    siStartInfo.cb = sizeof(STARTUPINFO);
    // NOTE: theoretically setting NULL to std handles should not be a problem
    // https://docs.microsoft.com/en-us/windows/console/getstdhandle?redirectedfrom=MSDN#attachdetach-behavior
    siStartInfo.hStdError = GetStdHandle(STD_ERROR_HANDLE);
    // TODO(#32): check for errors in GetStdHandle
    siStartInfo.hStdOutput = fdout ? *fdout : GetStdHandle(STD_OUTPUT_HANDLE);
    siStartInfo.hStdInput = fdin ? *fdin : GetStdHandle(STD_INPUT_HANDLE);
    siStartInfo.dwFlags |= STARTF_USESTDHANDLES;

    PROCESS_INFORMATION piProcInfo;
    ZeroMemory(&piProcInfo, sizeof(PROCESS_INFORMATION));

    BOOL bSuccess =
        CreateProcess(
            NULL,
            // TODO(#33): cmd_run_async on Windows does not render command line properly
            // It may require wrapping some arguments with double-quotes if they contains spaces, etc.
            cstr_array_join(" ", cmd.line),
            NULL,
            NULL,
            TRUE,
            0,
            NULL,
            NULL,
            &siStartInfo,
            &piProcInfo
        );

    if (!bSuccess) {
        PANIC("Could not create child process %s: %s\n",
              cmd_show(cmd), GetLastErrorAsString());
    }

    CloseHandle(piProcInfo.hThread);

    return piProcInfo.hProcess;
#else
    pid_t cpid = fork();
    if (cpid < 0) {
        PANIC("Could not fork child process: %s: %s",
              cmd_show(cmd), strerror(errno));
    }

    if (cpid == 0) {
        Cstr_Array args = cstr_array_append(cmd.line, NULL);

        if (fdin) {
            if (dup2(*fdin, STDIN_FILENO) < 0) {
                PANIC("Could not setup stdin for child process: %s", strerror(errno));
            }
        }

        if (fdout) {
            if (dup2(*fdout, STDOUT_FILENO) < 0) {
                PANIC("Could not setup stdout for child process: %s", strerror(errno));
            }
        }

        if (execvp(args.elems[0], (char * const*) args.elems) < 0) {
            PANIC("Could not exec child process: %s: %s",
                  cmd_show(cmd), strerror(errno));
        }
    }

    return cpid;
#endif // _WIN32
}

void cmd_run_sync(Cmd cmd)
{
    pid_wait(cmd_run_async(cmd, NULL, NULL));
}

static void chain_set_input_output_files_or_count_cmds(Chain *chain, Chain_Token token)
{
    switch (token.type) {
    case CHAIN_TOKEN_CMD: {
        chain->cmds.count += 1;
    }
    break;

    case CHAIN_TOKEN_IN: {
        if (chain->input_filepath) {
            PANIC("Input file path was already set");
        }

        chain->input_filepath = token.args.elems[0];
    }
    break;

    case CHAIN_TOKEN_OUT: {
        if (chain->output_filepath) {
            PANIC("Output file path was already set");
        }

        chain->output_filepath = token.args.elems[0];
    }
    break;

    case CHAIN_TOKEN_END:
    default: {
        assert(0 && "unreachable");
        exit(1);
    }
    }
}

static void chain_push_cmd(Chain *chain, Chain_Token token)
{
    if (token.type == CHAIN_TOKEN_CMD) {
        chain->cmds.elems[chain->cmds.count++] = (Cmd) {
            .line = token.args
        };
    }
}

Chain chain_build_from_tokens(Chain_Token first, ...)
{
    Chain result = {0};

    chain_set_input_output_files_or_count_cmds(&result, first);
    va_list args;
    va_start(args, first);
    Chain_Token next = va_arg(args, Chain_Token);
    while (next.type != CHAIN_TOKEN_END) {
        chain_set_input_output_files_or_count_cmds(&result, next);
        next = va_arg(args, Chain_Token);
    }
    va_end(args);

    result.cmds.elems = malloc(sizeof(result.cmds.elems[0]) * result.cmds.count);
    if (result.cmds.elems == NULL) {
        PANIC("could not allocate memory: %s", strerror(errno));
    }
    result.cmds.count = 0;

    chain_push_cmd(&result, first);

    va_start(args, first);
    next = va_arg(args, Chain_Token);
    while (next.type != CHAIN_TOKEN_END) {
        chain_push_cmd(&result, next);
        next = va_arg(args, Chain_Token);
    }
    va_end(args);

    return result;
}

void chain_run_sync(Chain chain)
{
    if (chain.cmds.count == 0) {
        return;
    }

    Pid *cpids = malloc(sizeof(Pid) * chain.cmds.count);

    Pipe pip = {0};
    Fd fdin = 0;
    Fd *fdprev = NULL;

    if (chain.input_filepath) {
        fdin = fd_open_for_read(chain.input_filepath);
        if (fdin < 0) {
            PANIC("could not open file %s: %s", chain.input_filepath, strerror(errno));
        }
        fdprev = &fdin;
    }

    for (size_t i = 0; i < chain.cmds.count - 1; ++i) {
        pip = pipe_make();

        cpids[i] = cmd_run_async(
                       chain.cmds.elems[i],
                       fdprev,
                       &pip.write);

        if (fdprev) fd_close(*fdprev);
        fd_close(pip.write);
        fdprev = &fdin;
        fdin = pip.read;
    }

    {
        Fd fdout = 0;
        Fd *fdnext = NULL;

        if (chain.output_filepath) {
            fdout = fd_open_for_write(chain.output_filepath);
            if (fdout < 0) {
                PANIC("could not open file %s: %s",
                      chain.output_filepath,
                      strerror(errno));
            }
            fdnext = &fdout;
        }

        const size_t last = chain.cmds.count - 1;
        cpids[last] =
            cmd_run_async(
                chain.cmds.elems[last],
                fdprev,
                fdnext);

        if (fdprev) fd_close(*fdprev);
        if (fdnext) fd_close(*fdnext);
    }

    for (size_t i = 0; i < chain.cmds.count; ++i) {
        pid_wait(cpids[i]);
    }
}

void chain_echo(Chain chain)
{
    printf("[INFO] CHAIN:");
    if (chain.input_filepath) {
        printf(" %s", chain.input_filepath);
    }

    FOREACH_ARRAY(Cmd, cmd, chain.cmds, {
        printf(" |> %s", cmd_show(*cmd));
    });

    if (chain.output_filepath) {
        printf(" |> %s", chain.output_filepath);
    }

    printf("\n");
}

int path_exists(Cstr path)
{
#ifdef _WIN32
    DWORD dwAttrib = GetFileAttributes(path);
    return (dwAttrib != INVALID_FILE_ATTRIBUTES);
#else
    struct stat statbuf = {0};
    if (stat(path, &statbuf) < 0) {
        if (errno == ENOENT) {
            errno = 0;
            return 0;
        }

        PANIC("could not retrieve information about file %s: %s",
              path, strerror(errno));
    }

    return 1;
#endif
}

int path_is_dir(Cstr path)
{
#ifdef _WIN32
    DWORD dwAttrib = GetFileAttributes(path);

    return (dwAttrib != INVALID_FILE_ATTRIBUTES &&
            (dwAttrib & FILE_ATTRIBUTE_DIRECTORY));
#else
    struct stat statbuf = {0};
    if (stat(path, &statbuf) < 0) {
        if (errno == ENOENT) {
            errno = 0;
            return 0;
        }

        PANIC("could not retrieve information about file %s: %s",
              path, strerror(errno));
    }

    return S_ISDIR(statbuf.st_mode);
#endif // _WIN32
}

void path_rename(const char *old_path, const char *new_path)
{
#ifdef _WIN32
    if (!MoveFileEx(old_path, new_path, MOVEFILE_REPLACE_EXISTING)) {
        PANIC("could not rename %s to %s: %s", old_path, new_path,
              GetLastErrorAsString());
    }
#else
    if (rename(old_path, new_path) < 0) {
        PANIC("could not rename %s to %s: %s", old_path, new_path,
              strerror(errno));
    }
#endif // _WIN32
}

void path_mkdirs(Cstr_Array path)
{
    if (path.count == 0) {
        return;
    }

    size_t len = 0;
    for (size_t i = 0; i < path.count; ++i) {
        len += strlen(path.elems[i]);
    }

    size_t seps_count = path.count - 1;
    const size_t sep_len = strlen(PATH_SEP);

    char *result = malloc(len + seps_count * sep_len + 1);

    len = 0;
    for (size_t i = 0; i < path.count; ++i) {
        size_t n = strlen(path.elems[i]);
        memcpy(result + len, path.elems[i], n);
        len += n;

        if (seps_count > 0) {
            memcpy(result + len, PATH_SEP, sep_len);
            len += sep_len;
            seps_count -= 1;
        }

        result[len] = '\0';

        if (mkdir(result, 0755) < 0) {
            if (errno == EEXIST) {
                errno = 0;
                WARN("directory %s already exists", result);
            } else {
                PANIC("could not create directory %s: %s", result, strerror(errno));
            }
        }
    }
}

void path_rm(Cstr path)
{
    if (IS_DIR(path)) {
        FOREACH_FILE_IN_DIR(file, path, {
            if (strcmp(file, ".") != 0 && strcmp(file, "..") != 0)
            {
                path_rm(PATH(path, file));
            }
        });

        if (rmdir(path) < 0) {
            if (errno == ENOENT) {
                errno = 0;
                WARN("directory %s does not exist", path);
            } else {
                PANIC("could not remove directory %s: %s", path, strerror(errno));
            }
        }
    } else {
        if (unlink(path) < 0) {
            if (errno == ENOENT) {
                errno = 0;
                WARN("file %s does not exist", path);
            } else {
                PANIC("could not remove file %s: %s", path, strerror(errno));
            }
        }
    }
}

int is_path1_modified_after_path2(const char *path1, const char *path2)
{
#ifdef _WIN32
    FILETIME path1_time, path2_time;

    Fd path1_fd = fd_open_for_read(path1);
    if (!GetFileTime(path1_fd, NULL, NULL, &path1_time)) {
        PANIC("could not get time of %s: %s", path1, GetLastErrorAsString());
    }
    fd_close(path1_fd);

    Fd path2_fd = fd_open_for_read(path2);
    if (!GetFileTime(path2_fd, NULL, NULL, &path2_time)) {
        PANIC("could not get time of %s: %s", path2, GetLastErrorAsString());
    }
    fd_close(path2_fd);

    return CompareFileTime(&path1_time, &path2_time) == 1;
#else
    struct stat statbuf = {0};

    if (stat(path1, &statbuf) < 0) {
        PANIC("could not stat %s: %s\n", path1, strerror(errno));
    }
    int path1_time = statbuf.st_mtime;

    if (stat(path2, &statbuf) < 0) {
        PANIC("could not stat %s: %s\n", path2, strerror(errno));
    }
    int path2_time = statbuf.st_mtime;

    return path1_time > path2_time;
#endif
}

void VLOG(FILE *stream, Cstr tag, Cstr fmt, va_list args)
{
    fprintf(stream, "[%s] ", tag);
    vfprintf(stream, fmt, args);
    fprintf(stream, "\n");
}

void INFO(Cstr fmt, ...)
{
    va_list args;
    va_start(args, fmt);
    VLOG(stderr, "INFO", fmt, args);
    va_end(args);
}

void WARN(Cstr fmt, ...)
{
    va_list args;
    va_start(args, fmt);
    VLOG(stderr, "WARN", fmt, args);
    va_end(args);
}

void ERRO(Cstr fmt, ...)
{
    va_list args;
    va_start(args, fmt);
    VLOG(stderr, "ERRO", fmt, args);
    va_end(args);
}

void PANIC(Cstr fmt, ...)
{
    va_list args;
    va_start(args, fmt);
    VLOG(stderr, "ERRO", fmt, args);
    va_end(args);
    exit(1);
}

char *shift_args(int *argc, char ***argv)
{
    assert(*argc > 0);
    char *result = **argv;
    *argc -= 1;
    *argv += 1;
    return result;
}

#endif // NOBUILD_IMPLEMENTATION