#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 "cache.h"
#include "quote.h"

#include "builtin.h"

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

static int handle_options(const char*** argv, int* argc)
{
        int handled = 0;

        while (*argc > 0) {
                const char *cmd = (*argv)[0];
                if (cmd[0] != '-')
                        break;

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

                /*
                 * Check remaining flags.
                 */
                if (!strncmp(cmd, "--exec-path", 11)) {
                        cmd += 11;
                        if (*cmd == '=')
                                git_set_exec_path(cmd + 1);
                        else {
                                puts(git_exec_path());
                                exit(0);
                        }
                } else if (!strcmp(cmd, "-p") || !strcmp(cmd, "--paginate")) {
                        setup_pager();
                } else if (!strcmp(cmd, "--git-dir")) {
                        if (*argc < 1)
                                return -1;
                        setenv("GIT_DIR", (*argv)[1], 1);
                        (*argv)++;
                        (*argc)--;
                } else if (!strncmp(cmd, "--git-dir=", 10)) {
                        setenv("GIT_DIR", cmd + 10, 1);
                } else if (!strcmp(cmd, "--bare")) {
                        static char git_dir[1024];
                        setenv("GIT_DIR", getcwd(git_dir, 1024), 1);
                } else {
                        fprintf(stderr, "Unknown option: %s\n", cmd);
                        cmd_usage(0, NULL, NULL);
                }

                (*argv)++;
                (*argc)--;
                handled++;
        }
        return handled;
}

static const char *alias_command;
static char *alias_string = NULL;

static int git_alias_config(const char *var, const char *value)
{
        if (!strncmp(var, "alias.", 6) && !strcmp(var + 6, alias_command)) {
                alias_string = strdup(value);
        }
        return 0;
}

static int split_cmdline(char *cmdline, const char ***argv)
{
        int src, dst, count = 0, size = 16;
        char quoted = 0;

        *argv = malloc(sizeof(char*) * size);

        /* split alias_string */
        (*argv)[count++] = cmdline;
        for (src = dst = 0; cmdline[src];) {
                char c = cmdline[src];
                if (!quoted && isspace(c)) {
                        cmdline[dst++] = 0;
                        while (cmdline[++src]
                                        && isspace(cmdline[src]))
                                ; /* skip */
                        if (count >= size) {
                                size += 16;
                                *argv = realloc(*argv, sizeof(char*) * size);
                        }
                        (*argv)[count++] = cmdline + dst;
                } else if(!quoted && (c == '\'' || c == '"')) {
                        quoted = c;
                        src++;
                } else if (c == quoted) {
                        quoted = 0;
                        src++;
                } else {
                        if (c == '\\' && quoted != '\'') {
                                src++;
                                c = cmdline[src];
                                if (!c) {
                                        free(*argv);
                                        *argv = NULL;
                                        return error("cmdline ends with \\");
                                }
                        }
                        cmdline[dst++] = c;
                        src++;
                }
        }

        cmdline[dst] = 0;

        if (quoted) {
                free(*argv);
                *argv = NULL;
                return error("unclosed quote");
        }

        return count;
}

static int handle_alias(int *argcp, const char ***argv)
{
        int nongit = 0, ret = 0, saved_errno = errno;
        const char *subdir;

        subdir = setup_git_directory_gently(&nongit);
        if (!nongit) {
                int count, option_count;
                const char** new_argv;

                alias_command = (*argv)[0];
                git_config(git_alias_config);
                if (alias_string) {

                        count = split_cmdline(alias_string, &new_argv);
                        option_count = handle_options(&new_argv, &count);
                        memmove(new_argv - option_count, new_argv,
                                        count * sizeof(char *));
                        new_argv -= option_count;

                        if (count < 1)
                                die("empty alias for %s", alias_command);

                        if (!strcmp(alias_command, new_argv[0]))
                                die("recursive alias: %s", alias_command);

                        if (getenv("GIT_TRACE")) {
                                int i;
                                fprintf(stderr, "trace: alias expansion: %s =>",
                                        alias_command);
                                for (i = 0; i < count; ++i) {
                                        fputc(' ', stderr);
                                        sq_quote_print(stderr, new_argv[i]);
                                }
                                fputc('\n', stderr);
                                fflush(stderr);
                        }

                        new_argv = realloc(new_argv, sizeof(char*) *
                                           (count + *argcp + 1));
                        /* insert after command name */
                        memcpy(new_argv + count, *argv + 1,
                               sizeof(char*) * *argcp);
                        new_argv[count+*argcp] = NULL;

                        *argv = new_argv;
                        *argcp += count - 1;

                        ret = 1;
                }
        }

        if (subdir)
                chdir(subdir);

        errno = saved_errno;

        return ret;
}

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 },
                { "format-patch", cmd_format_patch },
                { "count-objects", cmd_count_objects },
                { "diff", cmd_diff },
                { "grep", cmd_grep },
                { "rm", cmd_rm },
                { "add", cmd_add },
                { "rev-list", cmd_rev_list },
                { "init-db", cmd_init_db },
                { "get-tar-commit-id", cmd_get_tar_commit_id },
                { "upload-tar", cmd_upload_tar },
                { "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 },
                { "commit-tree", cmd_commit_tree },
                { "apply", cmd_apply },
                { "show-branch", cmd_show_branch },
                { "diff-files", cmd_diff_files },
                { "diff-index", cmd_diff_index },
                { "diff-stages", cmd_diff_stages },
                { "diff-tree", cmd_diff_tree },
                { "cat-file", cmd_cat_file },
                { "rev-parse", cmd_rev_parse },
                { "write-tree", cmd_write_tree },
                { "mailsplit", cmd_mailsplit },
                { "mailinfo", cmd_mailinfo },
                { "stripspace", cmd_stripspace },
                { "update-index", cmd_update_index },
                { "update-ref", cmd_update_ref },
                { "fmt-merge-msg", cmd_fmt_merge_msg },
                { "prune", cmd_prune },
                { "mv", cmd_mv },
        };
        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;

                if (getenv("GIT_TRACE")) {
                        int i;
                        fprintf(stderr, "trace: built-in: git");
                        for (i = 0; i < argc; ++i) {
                                fputc(' ', stderr);
                                sq_quote_print(stderr, argv[i]);
                        }
                        putc('\n', stderr);
                        fflush(stderr);
                }

                exit(p->fn(argc, argv, envp));
        }
}

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

        /*
         * 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);
        }

        /* Look for flags.. */
        argv++;
        argc--;
        handle_options(&argv, &argc);
        if (argc > 0) {
                if (!strncmp(argv[0], "--", 2))
                        argv[0] += 2;
        } else {
                /* Default command: "help" */
                argv[0] = "help";
                argc = 1;
        }
        cmd = argv[0];

        /*
         * 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));

        while (1) {
                /* See if it's an internal command */
                handle_internal_command(argc, argv, envp);

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

                /* It could be an alias -- this works around the insanity
                 * of overriding "git log" with "git show" by having
                 * alias.log = show
                 */
                if (done_alias || !handle_alias(&argc, &argv))
                        break;
                done_alias = 1;
        }

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

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

        return 1;
}