#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <dirent.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <limits.h>
#include <stdarg.h>
#include "git-compat-util.h"
#include "exec_cmd.h"

#include "builtin.h"

static void prepend_to_path(const char *dir, int len)
{
        char *path, *old_path = getenv("PATH");
        int path_len = len;

        if (!old_path)
                old_path = "/usr/local/bin:/usr/bin:/bin";

        path_len = len + strlen(old_path) + 1;

        path = malloc(path_len + 1);

        memcpy(path, dir, len);
        path[len] = ':';
        memcpy(path + len + 1, old_path, path_len - len);

        setenv("PATH", path, 1);
}

const char git_version_string[] = GIT_VERSION;

static void handle_internal_command(int argc, const char **argv, char **envp)
{
        const char *cmd = argv[0];
        static struct cmd_struct {
                const char *cmd;
                int (*fn)(int, const char **, char **);
        } commands[] = {
                { "version", cmd_version },
                { "help", cmd_help },
                { "log", cmd_log },
                { "whatchanged", cmd_whatchanged },
                { "show", cmd_show },
                { "push", cmd_push },
                { "count-objects", cmd_count_objects },
                { "diff", cmd_diff },
                { "grep", cmd_grep },
                { "rev-list", cmd_rev_list },
                { "init-db", cmd_init_db },
                { "check-ref-format", cmd_check_ref_format },
                { "ls-files", cmd_ls_files },
                { "ls-tree", cmd_ls_tree },
                { "tar-tree", cmd_tar_tree },
                { "read-tree", cmd_read_tree }
        };
        int i;

        /* Turn "git cmd --help" into "git help cmd" */
        if (argc > 1 && !strcmp(argv[1], "--help")) {
                argv[1] = argv[0];
                argv[0] = cmd = "help";
        }

        for (i = 0; i < ARRAY_SIZE(commands); i++) {
                struct cmd_struct *p = commands+i;
                if (strcmp(p->cmd, cmd))
                        continue;
                exit(p->fn(argc, argv, envp));
        }
}

int main(int argc, const char **argv, char **envp)
{
        const char *cmd = argv[0];
        char *slash = strrchr(cmd, '/');
        char git_command[PATH_MAX + 1];
        const char *exec_path = NULL;

        /*
         * Take the basename of argv[0] as the command
         * name, and the dirname as the default exec_path
         * if it's an absolute path and we don't have
         * anything better.
         */
        if (slash) {
                *slash++ = 0;
                if (*cmd == '/')
                        exec_path = cmd;
                cmd = slash;
        }

        /*
         * "git-xxxx" is the same as "git xxxx", but we obviously:
         *
         *  - cannot take flags in between the "git" and the "xxxx".
         *  - cannot execute it externally (since it would just do
         *    the same thing over again)
         *
         * So we just directly call the internal command handler, and
         * die if that one cannot handle it.
         */
        if (!strncmp(cmd, "git-", 4)) {
                cmd += 4;
                argv[0] = cmd;
                handle_internal_command(argc, argv, envp);
                die("cannot handle %s internally", cmd);
        }

        /* Default command: "help" */
        cmd = "help";

        /* Look for flags.. */
        while (argc > 1) {
                cmd = *++argv;
                argc--;

                if (strncmp(cmd, "--", 2))
                        break;

                cmd += 2;

                /*
                 * For legacy reasons, the "version" and "help"
                 * commands can be written with "--" prepended
                 * to make them look like flags.
                 */
                if (!strcmp(cmd, "help"))
                        break;
                if (!strcmp(cmd, "version"))
                        break;

                /*
                 * Check remaining flags (which by now must be
                 * "--exec-path", but maybe we will accept
                 * other arguments some day)
                 */
                if (!strncmp(cmd, "exec-path", 9)) {
                        cmd += 9;
                        if (*cmd == '=') {
                                git_set_exec_path(cmd + 1);
                                continue;
                        }
                        puts(git_exec_path());
                        exit(0);
                }
                cmd_usage(0, NULL, NULL);
        }
        argv[0] = cmd;

        /*
         * We search for git commands in the following order:
         *  - git_exec_path()
         *  - the path of the "git" command if we could find it
         *    in $0
         *  - the regular PATH.
         */
        if (exec_path)
                prepend_to_path(exec_path, strlen(exec_path));
        exec_path = git_exec_path();
        prepend_to_path(exec_path, strlen(exec_path));

        /* See if it's an internal command */
        handle_internal_command(argc, argv, envp);

        /* .. then try the external ones */
        execv_git_cmd(argv);

        if (errno == ENOENT)
                cmd_usage(0, exec_path, "'%s' is not a git-command", cmd);

        fprintf(stderr, "Failed to run command '%s': %s\n",
                git_command, strerror(errno));

        return 1;
}