#include "cache.h"
#include "quote.h"
#include "exec_cmd.h"
#include "strbuf.h"
#include "run-command.h"

#define COMMAND_DIR "git-shell-commands"
#define HELP_COMMAND COMMAND_DIR "/help"

static int do_generic_cmd(const char *me, char *arg)
{
        const char *my_argv[4];

        setup_path();
        if (!arg || !(arg = sq_dequote(arg)))
                die("bad argument");
        if (prefixcmp(me, "git-"))
                die("bad command");

        my_argv[0] = me + 4;
        my_argv[1] = arg;
        my_argv[2] = NULL;

        return execv_git_cmd(my_argv);
}

static int do_cvs_cmd(const char *me, char *arg)
{
        const char *cvsserver_argv[3] = {
                "cvsserver", "server", NULL
        };

        if (!arg || strcmp(arg, "server"))
                die("git-cvsserver only handles server: %s", arg);

        setup_path();
        return execv_git_cmd(cvsserver_argv);
}

static int is_valid_cmd_name(const char *cmd)
{
        /* Test command contains no . or / characters */
        return cmd[strcspn(cmd, "./")] == '\0';
}

static char *make_cmd(const char *prog)
{
        char *prefix = xmalloc((strlen(prog) + strlen(COMMAND_DIR) + 2));
        strcpy(prefix, COMMAND_DIR);
        strcat(prefix, "/");
        strcat(prefix, prog);
        return prefix;
}

static void cd_to_homedir(void)
{
        const char *home = getenv("HOME");
        if (!home)
                die("could not determine user's home directory; HOME is unset");
        if (chdir(home) == -1)
                die("could not chdir to user's home directory");
}

static void run_shell(void)
{
        int done = 0;
        static const char *help_argv[] = { HELP_COMMAND, NULL };
        /* Print help if enabled */
        run_command_v_opt(help_argv, RUN_SILENT_EXEC_FAILURE);

        do {
                struct strbuf line = STRBUF_INIT;
                const char *prog;
                char *full_cmd;
                char *rawargs;
                const char **argv;
                int code;

                fprintf(stderr, "git> ");
                if (strbuf_getline(&line, stdin, '\n') == EOF) {
                        fprintf(stderr, "\n");
                        strbuf_release(&line);
                        break;
                }
                strbuf_trim(&line);
                rawargs = strbuf_detach(&line, NULL);
                if (split_cmdline(rawargs, &argv) == -1) {
                        free(rawargs);
                        continue;
                }

                prog = argv[0];
                if (!strcmp(prog, "")) {
                } else if (!strcmp(prog, "quit") || !strcmp(prog, "logout") ||
                           !strcmp(prog, "exit") || !strcmp(prog, "bye")) {
                        done = 1;
                } else if (is_valid_cmd_name(prog)) {
                        full_cmd = make_cmd(prog);
                        argv[0] = full_cmd;
                        code = run_command_v_opt(argv, RUN_SILENT_EXEC_FAILURE);
                        if (code == -1 && errno == ENOENT) {
                                fprintf(stderr, "unrecognized command '%s'\n", prog);
                        }
                        free(full_cmd);
                } else {
                        fprintf(stderr, "invalid command format '%s'\n", prog);
                }

                free(argv);
                free(rawargs);
        } while (!done);
}

static struct commands {
        const char *name;
        int (*exec)(const char *me, char *arg);
} cmd_list[] = {
        { "git-receive-pack", do_generic_cmd },
        { "git-upload-pack", do_generic_cmd },
        { "git-upload-archive", do_generic_cmd },
        { "cvs", do_cvs_cmd },
        { NULL },
};

int main(int argc, char **argv)
{
        char *prog;
        const char **user_argv;
        struct commands *cmd;
        int devnull_fd;

        /*
         * Always open file descriptors 0/1/2 to avoid clobbering files
         * in die().  It also avoids not messing up when the pipes are
         * dup'ed onto stdin/stdout/stderr in the child processes we spawn.
         */
        devnull_fd = open("/dev/null", O_RDWR);
        while (devnull_fd >= 0 && devnull_fd <= 2)
                devnull_fd = dup(devnull_fd);
        if (devnull_fd == -1)
                die_errno("opening /dev/null failed");
        close (devnull_fd);

        /*
         * Special hack to pretend to be a CVS server
         */
        if (argc == 2 && !strcmp(argv[1], "cvs server")) {
                argv--;
        } else if (argc == 1) {
                /* Allow the user to run an interactive shell */
                cd_to_homedir();
                if (access(COMMAND_DIR, R_OK | X_OK) == -1) {
                        die("Interactive git shell is not enabled.\n"
                            "hint: ~/" COMMAND_DIR " should exist "
                            "and have read and execute access.");
                }
                run_shell();
                exit(0);
        } else if (argc != 3 || strcmp(argv[1], "-c")) {
                /*
                 * We do not accept any other modes except "-c" followed by
                 * "cmd arg", where "cmd" is a very limited subset of git
                 * commands or a command in the COMMAND_DIR
                 */
                die("Run with no arguments or with -c cmd");
        }

        prog = xstrdup(argv[2]);
        if (!strncmp(prog, "git", 3) && isspace(prog[3]))
                /* Accept "git foo" as if the caller said "git-foo". */
                prog[3] = '-';

        for (cmd = cmd_list ; cmd->name ; cmd++) {
                int len = strlen(cmd->name);
                char *arg;
                if (strncmp(cmd->name, prog, len))
                        continue;
                arg = NULL;
                switch (prog[len]) {
                case '\0':
                        arg = NULL;
                        break;
                case ' ':
                        arg = prog + len + 1;
                        break;
                default:
                        continue;
                }
                exit(cmd->exec(cmd->name, arg));
        }

        cd_to_homedir();
        if (split_cmdline(prog, &user_argv) != -1) {
                if (is_valid_cmd_name(user_argv[0])) {
                        prog = make_cmd(user_argv[0]);
                        user_argv[0] = prog;
                        execv(user_argv[0], (char *const *) user_argv);
                }
                free(prog);
                free(user_argv);
                die("unrecognized command '%s'", argv[2]);
        } else {
                free(prog);
                die("invalid command format '%s'", argv[2]);
        }
}