/*-
 * Copyright (c) 2019, 2023 Kyle Evans <kevans@FreeBSD.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <sys/stat.h>
#include <sys/utsname.h>
#include <sys/wait.h>

#include <assert.h>
#include <errno.h>
#include <fnmatch.h>
#include <grp.h>
#include <libgen.h>
#include <pwd.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <lua.h>
#include "lauxlib.h"
#include "lposix.h"

static void
enforce_max_args(lua_State *L, int max)
{
        int narg;

        narg = lua_gettop(L);
        luaL_argcheck(L, narg <= max, max + 1, "too many arguments");
}

/*
 * Minimal implementation of luaposix needed for internal FreeBSD bits.
 */
static int
lua__exit(lua_State *L)
{
        int code;

        enforce_max_args(L, 1);
        code = luaL_checkinteger(L, 1);

        _exit(code);
}

static int
lua_basename(lua_State *L)
{
        char *inpath, *outpath;

        enforce_max_args(L, 1);
        inpath = strdup(luaL_checkstring(L, 1));
        if (inpath == NULL) {
                lua_pushnil(L);
                lua_pushstring(L, strerror(ENOMEM));
                lua_pushinteger(L, ENOMEM);
                return (3);
        }

        outpath = basename(inpath);
        lua_pushstring(L, outpath);
        free(inpath);
        return (1);
}

static int
lua_chmod(lua_State *L)
{
        const char *path;
        mode_t mode;

        enforce_max_args(L, 2);
        path = luaL_checkstring(L, 1);
        mode = (mode_t)luaL_checkinteger(L, 2);

        if (chmod(path, mode) == -1) {
                lua_pushnil(L);
                lua_pushstring(L, strerror(errno));
                lua_pushinteger(L, errno);
                return (3);
        }
        lua_pushinteger(L, 0);
        return (1);
}

static int
lua_chown(lua_State *L)
{
        const char *path;
        uid_t owner = (uid_t)-1;
        gid_t group = (gid_t)-1;
        int error;

        enforce_max_args(L, 3);

        path = luaL_checkstring(L, 1);
        if (lua_isinteger(L, 2))
                owner = (uid_t)lua_tointeger(L, 2);
        else if (lua_isstring(L, 2)) {
                char buf[4096];
                struct passwd passwd, *pwd = NULL;

                error = getpwnam_r(lua_tostring(L, 2), &passwd,
                    buf, sizeof(buf), &pwd);
                if (pwd != NULL && error == 0)
                        owner = pwd->pw_uid;
                else
                        return (luaL_argerror(L, 2,
                            lua_pushfstring(L, "unknown user %s",
                            lua_tostring(L, 2))));
        } else if (!lua_isnoneornil(L, 2)) {
                const char *type = luaL_typename(L, 2);
                return (luaL_argerror(L, 2,
                    lua_pushfstring(L, "integer or string expected, got %s",
                    type)));
        }

        if (lua_isinteger(L, 3))
                group = (gid_t)lua_tointeger(L, 3);
        else if (lua_isstring(L, 3)) {
                char buf[4096];
                struct group gr, *grp = NULL;

                error = getgrnam_r(lua_tostring(L, 3), &gr, buf, sizeof(buf),
                    &grp);
                if (grp != NULL && error == 0)
                        group = grp->gr_gid;
                else
                        return (luaL_argerror(L, 3,
                            lua_pushfstring(L, "unknown group %s",
                            lua_tostring(L, 3))));
        } else if (!lua_isnoneornil(L, 3)) {
                const char *type = luaL_typename(L, 3);
                return (luaL_argerror(L, 3,
                    lua_pushfstring(L, "integer or string expected, got %s",
                    type)));
        }

        if (chown(path, owner, group) == -1) {
                lua_pushnil(L);
                lua_pushstring(L, strerror(errno));
                lua_pushinteger(L, errno);
                return (3);
        }
        lua_pushinteger(L, 0);
        return (1);
}

static int
lua_pclose(lua_State *L)
{
        int error, fd;

        enforce_max_args(L, 1);

        fd = luaL_checkinteger(L, 1);
        if (fd < 0) {
                error = EBADF;
                goto err;
        }

        if (close(fd) == 0) {
                lua_pushinteger(L, 0);
                return (1);
        }

        error = errno;
err:
        lua_pushnil(L);
        lua_pushstring(L, strerror(error));
        lua_pushinteger(L, error);
        return (3);

}

static int
lua_dup2(lua_State *L)
{
        int error, oldd, newd;

        enforce_max_args(L, 2);

        oldd = luaL_checkinteger(L, 1);
        if (oldd < 0) {
                error = EBADF;
                goto err;
        }

        newd = luaL_checkinteger(L, 2);
        if (newd < 0) {
                error = EBADF;
                goto err;
        }

        error = dup2(oldd, newd);
        if (error >= 0) {
                lua_pushinteger(L, error);
                return (1);
        }

        error = errno;
err:
        lua_pushnil(L);
        lua_pushstring(L, strerror(error));
        lua_pushinteger(L, error);
        return (3);
}

static int
lua_execp(lua_State *L)
{
        int argc, error;
        const char *file;
        const char **argv;

        enforce_max_args(L, 2);

        file = luaL_checkstring(L, 1);
        luaL_checktype(L, 2, LUA_TTABLE);

        lua_len(L, 2);
        argc = lua_tointeger(L, -1);

        /*
         * Use lua_newuserdatauv() to allocate a scratch buffer that is tracked
         * and freed by lua's GC. This avoid any chance of a leak if a lua error
         * is raised later in this function (e.g. by luaL_argerror()).
         * The (argc + 2) size gives enough space in the buffer for argv[0] and
         * the terminating NULL.
         */
        argv = lua_newuserdatauv(L, (argc + 2) * sizeof(char *), 0);

        /*
         * Sequential tables in lua start at index 1 by convention.
         * If there happens to be a string at index 0, use that to
         * override the default argv[0]. This matches the lposix API.
         */
        lua_pushinteger(L, 0);
        lua_gettable(L, 2);
        argv[0] = lua_tostring(L, -1);
        if (argv[0] == NULL) {
                argv[0] = file;
        }

        for (int i = 1; i <= argc; i++) {
                lua_pushinteger(L, i);
                lua_gettable(L, 2);
                argv[i] = lua_tostring(L, -1);
                if (argv[i] == NULL) {
                        luaL_argerror(L, 2,
                            "argv table must contain only strings");
                }
        }
        argv[argc + 1] = NULL;

        execvp(file, __DECONST(char **, argv));
        error = errno;

        lua_pushnil(L);
        lua_pushstring(L, strerror(error));
        lua_pushinteger(L, error);
        return (3);
}

static int
lua_fnmatch(lua_State *L)
{
        const char *pattern, *string;
        int flags;

        enforce_max_args(L, 3);
        pattern = luaL_checkstring(L, 1);
        string = luaL_checkstring(L, 2);
        flags = luaL_optinteger(L, 3, 0);

        lua_pushinteger(L, fnmatch(pattern, string, flags));

        return (1);
}

static int
lua_uname(lua_State *L)
{
        struct utsname name;
        int error;

        enforce_max_args(L, 0);

        error = uname(&name);
        if (error != 0) {
                error = errno;
                lua_pushnil(L);
                lua_pushstring(L, strerror(error));
                lua_pushinteger(L, error);
                return (3);
        }

        lua_newtable(L);
#define setkv(f) do {                   \
        lua_pushstring(L, name.f);      \
        lua_setfield(L, -2, #f);        \
} while (0)
        setkv(sysname);
        setkv(nodename);
        setkv(release);
        setkv(version);
        setkv(machine);
#undef setkv

        return (1);
}

static int
lua_dirname(lua_State *L)
{
        char *inpath, *outpath;

        enforce_max_args(L, 1);

        inpath = strdup(luaL_checkstring(L, 1));
        if (inpath == NULL) {
                lua_pushnil(L);
                lua_pushstring(L, strerror(ENOMEM));
                lua_pushinteger(L, ENOMEM);
                return (3);
        }

        outpath = dirname(inpath);
        lua_pushstring(L, outpath);
        free(inpath);
        return (1);
}

static int
lua_fork(lua_State *L)
{
        pid_t pid;

        enforce_max_args(L, 0);

        pid = fork();
        if (pid < 0) {
                lua_pushnil(L);
                lua_pushstring(L, strerror(errno));
                lua_pushinteger(L, errno);
                return (3);
        }

        lua_pushinteger(L, pid);
        return (1);
}

static int
lua_getpid(lua_State *L)
{
        enforce_max_args(L, 0);

        lua_pushinteger(L, getpid());
        return (1);
}

static int
lua_pipe(lua_State *L)
{
        int error, fd[2];

        enforce_max_args(L, 0);

        error = pipe(fd);
        if (error != 0) {
                lua_pushnil(L);
                lua_pushstring(L, strerror(errno));
                lua_pushinteger(L, errno);
                return (1);
        }

        lua_pushinteger(L, fd[0]);
        lua_pushinteger(L, fd[1]);
        return (2);
}

static int
lua_read(lua_State *L)
{
        char *buf;
        ssize_t ret;
        size_t sz;
        int error = 0, fd;

        enforce_max_args(L, 2);
        fd = luaL_checkinteger(L, 1);
        sz = luaL_checkinteger(L, 2);

        if (fd < 0) {
                error = EBADF;
                goto err;
        }

        buf = malloc(sz);
        if (buf == NULL) {
                error = errno;
                goto err;
        }

        /*
         * For 0-byte reads, we'll still push the empty string and let the
         * caller deal with EOF to match lposix semantics.
         */
        ret = read(fd, buf, sz);
        if (ret >= 0)
                lua_pushlstring(L, buf, ret);
        else if (ret < 0)
                error = errno; /* Save to avoid clobber by free() */

        free(buf);
        if (ret < 0)
                goto err;

        /* Just the string pushed. */
        return (1);
err:
        assert(error != 0);
        lua_pushnil(L);
        lua_pushstring(L, strerror(error));
        lua_pushinteger(L, error);
        return (3);
}

static int
lua_realpath(lua_State *L)
{
        const char *inpath;
        char *outpath;

        enforce_max_args(L, 1);
        inpath = luaL_checkstring(L, 1);

        outpath = realpath(inpath, NULL);
        if (outpath == NULL) {
                lua_pushnil(L);
                lua_pushstring(L, strerror(errno));
                lua_pushinteger(L, errno);
                return (3);
        }

        lua_pushstring(L, outpath);
        free(outpath);
        return (1);
}

static int
lua_wait(lua_State *L)
{
        pid_t pid;
        int options, status;

        enforce_max_args(L, 2);
        pid = luaL_optinteger(L, 1, -1);
        options = luaL_optinteger(L, 2, 0);

        status = 0;
        pid = waitpid(pid, &status, options);
        if (pid < 0) {
                lua_pushnil(L);
                lua_pushstring(L, strerror(errno));
                lua_pushinteger(L, errno);
                return (3);
        }

        lua_pushinteger(L, pid);
        if (pid == 0) {
                lua_pushliteral(L, "running");
                return (2);
        }

        if (WIFCONTINUED(status)) {
                lua_pushliteral(L, "continued");
                return (2);
        } else if(WIFSTOPPED(status)) {
                lua_pushliteral(L, "stopped");
                lua_pushinteger(L, WSTOPSIG(status));
                return (3);
        } else if (WIFEXITED(status)) {
                lua_pushliteral(L, "exited");
                lua_pushinteger(L, WEXITSTATUS(status));
                return (3);
        } else if (WIFSIGNALED(status)) {
                lua_pushliteral(L, "killed");
                lua_pushinteger(L, WTERMSIG(status));
                return (3);
        }

        return (1);
}

static int
lua_write(lua_State *L)
{
        const char *buf;
        size_t bufsz, sz;
        ssize_t ret;
        off_t offset;
        int error, fd;

        enforce_max_args(L, 4);

        fd = luaL_checkinteger(L, 1);
        if (fd < 0) {
                error = EBADF;
                goto err;
        }

        buf = luaL_checkstring(L, 2);

        bufsz = lua_rawlen(L, 2);
        sz = luaL_optinteger(L, 3, bufsz);

        offset = luaL_optinteger(L, 4, 0);


        if ((size_t)offset > bufsz || offset + sz > bufsz) {
                lua_pushnil(L);
                lua_pushfstring(L,
                    "write: invalid access offset %zu, size %zu in a buffer size %zu",
                    offset, sz, bufsz);
                lua_pushinteger(L, EINVAL);
                return (3);
        }

        ret = write(fd, buf + offset, sz);
        if (ret < 0) {
                error = errno;
                goto err;
        }

        lua_pushinteger(L, ret);
        return (1);
err:
        lua_pushnil(L);
        lua_pushstring(L, strerror(error));
        lua_pushinteger(L, error);
        return (3);
}

#define REG_DEF(n, func)        { #n, func }
#define REG_SIMPLE(n)           REG_DEF(n, lua_ ## n)
static const struct luaL_Reg libgenlib[] = {
        REG_SIMPLE(basename),
        REG_SIMPLE(dirname),
        { NULL, NULL },
};

static const struct luaL_Reg stdliblib[] = {
        REG_SIMPLE(realpath),
        { NULL, NULL },
};

static const struct luaL_Reg fnmatchlib[] = {
        REG_SIMPLE(fnmatch),
        { NULL, NULL },
};

static const struct luaL_Reg sys_statlib[] = {
        REG_SIMPLE(chmod),
        { NULL, NULL },
};

static const struct luaL_Reg sys_utsnamelib[] = {
        REG_SIMPLE(uname),
        { NULL, NULL },
};

static const struct luaL_Reg sys_waitlib[] = {
        REG_SIMPLE(wait),
        {NULL, NULL},
};

static const struct luaL_Reg unistdlib[] = {
        REG_SIMPLE(_exit),
        REG_SIMPLE(chown),
        REG_DEF(close, lua_pclose),
        REG_SIMPLE(dup2),
        REG_SIMPLE(execp),
        REG_SIMPLE(fork),
        REG_SIMPLE(getpid),
        REG_SIMPLE(pipe),
        REG_SIMPLE(read),
        REG_SIMPLE(write),
        { NULL, NULL },
};

#undef REG_SIMPLE
#undef REG_DEF

static int
luaopen_posix_libgen(lua_State *L)
{
        luaL_newlib(L, libgenlib);
        return (1);
}

static int
luaopen_posix_stdlib(lua_State *L)
{
        luaL_newlib(L, stdliblib);
        return (1);
}

static int
luaopen_posix_fnmatch(lua_State *L)
{
        luaL_newlib(L, fnmatchlib);

#define setkv(f) do {                   \
        lua_pushinteger(L, f);          \
        lua_setfield(L, -2, #f);        \
} while (0)
        setkv(FNM_PATHNAME);
        setkv(FNM_NOESCAPE);
        setkv(FNM_NOMATCH);
        setkv(FNM_PERIOD);
#undef setkv

        return 1;
}

static int
luaopen_posix_sys_stat(lua_State *L)
{
        luaL_newlib(L, sys_statlib);
        return (1);
}

static int
luaopen_posix_sys_utsname(lua_State *L)
{
        luaL_newlib(L, sys_utsnamelib);
        return 1;
}

static int
luaopen_posix_sys_wait(lua_State *L)
{
        luaL_newlib(L, sys_waitlib);

#define lua_pushflag(L, flag) do {      \
        lua_pushinteger(L, flag);       \
        lua_setfield(L, -2, #flag);     \
} while(0)

        /* Only these two exported by lposix */
        lua_pushflag(L, WNOHANG);
        lua_pushflag(L, WUNTRACED);

        lua_pushflag(L, WCONTINUED);
        lua_pushflag(L, WSTOPPED);
#ifdef WTRAPPED
        lua_pushflag(L, WTRAPPED);
#endif
        lua_pushflag(L, WEXITED);
        lua_pushflag(L, WNOWAIT);
#undef lua_pushflag

        return (1);
}

static int
luaopen_posix_unistd(lua_State *L)
{
        luaL_newlib(L, unistdlib);
        return (1);
}

int
luaopen_posix(lua_State *L)
{
        lua_newtable(L); /* posix */

        luaL_requiref(L, "posix.fnmatch", luaopen_posix_fnmatch, 0);
        lua_setfield(L, -2, "fnmatch");

        luaL_requiref(L, "posix.libgen", luaopen_posix_libgen, 0);
        lua_setfield(L, -2, "libgen");

        luaL_requiref(L, "posix.stdlib", luaopen_posix_stdlib, 0);
        lua_setfield(L, -2, "stdlib");

        lua_newtable(L); /* posix.sys */
        luaL_requiref(L, "posix.sys.stat", luaopen_posix_sys_stat, 0);
        lua_setfield(L, -2, "stat");
        luaL_requiref(L, "posix.sys.utsname", luaopen_posix_sys_utsname, 0);
        lua_setfield(L, -2, "utsname");
        luaL_requiref(L, "posix.sys.wait", luaopen_posix_sys_wait, 0);
        lua_setfield(L, -2, "wait");
        lua_setfield(L, -2, "sys");

        luaL_requiref(L, "posix.unistd", luaopen_posix_unistd, 0);
        lua_setfield(L, -2, "unistd");

        return (1);
}