#include <linux/compiler.h>
#include <linux/string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include "subcmd-util.h"
#include "exec-cmd.h"
#include "subcmd-config.h"

#define MAX_ARGS        32
#define PATH_MAX        4096

static const char *argv_exec_path;
static const char *argv0_path;

void exec_cmd_init(const char *exec_name, const char *prefix,
                   const char *exec_path, const char *exec_path_env)
{
        subcmd_config.exec_name         = exec_name;
        subcmd_config.prefix            = prefix;
        subcmd_config.exec_path         = exec_path;
        subcmd_config.exec_path_env     = exec_path_env;
}

#define is_dir_sep(c) ((c) == '/')

static int is_absolute_path(const char *path)
{
        return path[0] == '/';
}

static const char *get_pwd_cwd(void)
{
        static char cwd[PATH_MAX + 1];
        char *pwd;
        struct stat cwd_stat, pwd_stat;
        if (getcwd(cwd, PATH_MAX) == NULL)
                return NULL;
        pwd = getenv("PWD");
        if (pwd && strcmp(pwd, cwd)) {
                stat(cwd, &cwd_stat);
                if (!stat(pwd, &pwd_stat) &&
                    pwd_stat.st_dev == cwd_stat.st_dev &&
                    pwd_stat.st_ino == cwd_stat.st_ino) {
                        strlcpy(cwd, pwd, PATH_MAX);
                }
        }
        return cwd;
}

static const char *make_nonrelative_path(const char *path)
{
        static char buf[PATH_MAX + 1];

        if (is_absolute_path(path)) {
                if (strlcpy(buf, path, PATH_MAX) >= PATH_MAX)
                        die("Too long path: %.*s", 60, path);
        } else {
                const char *cwd = get_pwd_cwd();
                if (!cwd)
                        die("Cannot determine the current working directory");
                if (snprintf(buf, PATH_MAX, "%s/%s", cwd, path) >= PATH_MAX)
                        die("Too long path: %.*s", 60, path);
        }
        return buf;
}

char *system_path(const char *path)
{
        char *buf = NULL;

        if (is_absolute_path(path))
                return strdup(path);

        astrcatf(&buf, "%s/%s", subcmd_config.prefix, path);

        return buf;
}

const char *extract_argv0_path(const char *argv0)
{
        const char *slash;

        if (!argv0 || !*argv0)
                return NULL;
        slash = argv0 + strlen(argv0);

        while (argv0 <= slash && !is_dir_sep(*slash))
                slash--;

        if (slash >= argv0) {
                argv0_path = strndup(argv0, slash - argv0);
                return argv0_path ? slash + 1 : NULL;
        }

        return argv0;
}

void set_argv_exec_path(const char *exec_path)
{
        argv_exec_path = exec_path;
        /*
         * Propagate this setting to external programs.
         */
        setenv(subcmd_config.exec_path_env, exec_path, 1);
}


/* Returns the highest-priority location to look for subprograms. */
char *get_argv_exec_path(void)
{
        char *env;

        if (argv_exec_path)
                return strdup(argv_exec_path);

        env = getenv(subcmd_config.exec_path_env);
        if (env && *env)
                return strdup(env);

        return system_path(subcmd_config.exec_path);
}

static void add_path(char **out, const char *path)
{
        if (path && *path) {
                if (is_absolute_path(path))
                        astrcat(out, path);
                else
                        astrcat(out, make_nonrelative_path(path));

                astrcat(out, ":");
        }
}

void setup_path(void)
{
        const char *old_path = getenv("PATH");
        char *new_path = NULL;
        char *tmp = get_argv_exec_path();

        add_path(&new_path, tmp);
        add_path(&new_path, argv0_path);
        free(tmp);

        if (old_path)
                astrcat(&new_path, old_path);
        else
                astrcat(&new_path, "/usr/local/bin:/usr/bin:/bin");

        setenv("PATH", new_path, 1);

        free(new_path);
}

static const char **prepare_exec_cmd(const char **argv)
{
        int argc;
        const char **nargv;

        for (argc = 0; argv[argc]; argc++)
                ; /* just counting */
        nargv = malloc(sizeof(*nargv) * (argc + 2));

        nargv[0] = subcmd_config.exec_name;
        for (argc = 0; argv[argc]; argc++)
                nargv[argc + 1] = argv[argc];
        nargv[argc + 1] = NULL;
        return nargv;
}

int execv_cmd(const char **argv) {
        const char **nargv = prepare_exec_cmd(argv);

        /* execvp() can only ever return if it fails */
        execvp(subcmd_config.exec_name, (char **)nargv);

        free(nargv);
        return -1;
}


int execl_cmd(const char *cmd,...)
{
        int argc;
        const char *argv[MAX_ARGS + 1];
        const char *arg;
        va_list param;

        va_start(param, cmd);
        argv[0] = cmd;
        argc = 1;
        while (argc < MAX_ARGS) {
                arg = argv[argc++] = va_arg(param, char *);
                if (!arg)
                        break;
        }
        va_end(param);
        if (MAX_ARGS <= argc) {
                fprintf(stderr, " Error: too many args to run %s\n", cmd);
                return -1;
        }

        argv[argc] = NULL;
        return execv_cmd(argv);
}