#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 <sys/ioctl.h>
#include "git-compat-util.h"
#include "exec_cmd.h"

#ifndef PATH_MAX
# define PATH_MAX 4096
#endif

static const char git_usage[] =
        "Usage: git [--version] [--exec-path[=GIT_EXEC_PATH]] [--help] COMMAND [ ARGS ]";

/* most gui terms set COLUMNS (although some don't export it) */
static int term_columns(void)
{
        char *col_string = getenv("COLUMNS");
        int n_cols = 0;

        if (col_string && (n_cols = atoi(col_string)) > 0)
                return n_cols;

#ifdef TIOCGWINSZ
        {
                struct winsize ws;
                if (!ioctl(1, TIOCGWINSZ, &ws)) {
                        if (ws.ws_col)
                                return ws.ws_col;
                }
        }
#endif

        return 80;
}

static void oom(void)
{
        fprintf(stderr, "git: out of memory\n");
        exit(1);
}

static inline void mput_char(char c, unsigned int num)
{
        while(num--)
                putchar(c);
}

static struct cmdname {
        size_t len;
        char name[1];
} **cmdname;
static int cmdname_alloc, cmdname_cnt;

static void add_cmdname(const char *name, int len)
{
        struct cmdname *ent;
        if (cmdname_alloc <= cmdname_cnt) {
                cmdname_alloc = cmdname_alloc + 200;
                cmdname = realloc(cmdname, cmdname_alloc * sizeof(*cmdname));
                if (!cmdname)
                        oom();
        }
        ent = malloc(sizeof(*ent) + len);
        if (!ent)
                oom();
        ent->len = len;
        memcpy(ent->name, name, len);
        ent->name[len] = 0;
        cmdname[cmdname_cnt++] = ent;
}

static int cmdname_compare(const void *a_, const void *b_)
{
        struct cmdname *a = *(struct cmdname **)a_;
        struct cmdname *b = *(struct cmdname **)b_;
        return strcmp(a->name, b->name);
}

static void pretty_print_string_list(struct cmdname **cmdname, int longest)
{
        int cols = 1, rows;
        int space = longest + 1; /* min 1 SP between words */
        int max_cols = term_columns() - 1; /* don't print *on* the edge */
        int i, j;

        if (space < max_cols)
                cols = max_cols / space;
        rows = (cmdname_cnt + cols - 1) / cols;

        qsort(cmdname, cmdname_cnt, sizeof(*cmdname), cmdname_compare);

        for (i = 0; i < rows; i++) {
                printf("  ");

                for (j = 0; j < cols; j++) {
                        int n = j * rows + i;
                        int size = space;
                        if (n >= cmdname_cnt)
                                break;
                        if (j == cols-1 || n + rows >= cmdname_cnt)
                                size = 1;
                        printf("%-*s", size, cmdname[n]->name);
                }
                putchar('\n');
        }
}

static void list_commands(const char *exec_path, const char *pattern)
{
        unsigned int longest = 0;
        char path[PATH_MAX];
        int dirlen;
        DIR *dir = opendir(exec_path);
        struct dirent *de;

        if (!dir) {
                fprintf(stderr, "git: '%s': %s\n", exec_path, strerror(errno));
                exit(1);
        }

        dirlen = strlen(exec_path);
        if (PATH_MAX - 20 < dirlen) {
                fprintf(stderr, "git: insanely long exec-path '%s'\n",
                        exec_path);
                exit(1);
        }

        memcpy(path, exec_path, dirlen);
        path[dirlen++] = '/';

        while ((de = readdir(dir)) != NULL) {
                struct stat st;
                int entlen;

                if (strncmp(de->d_name, "git-", 4))
                        continue;
                strcpy(path+dirlen, de->d_name);
                if (stat(path, &st) || /* stat, not lstat */
                    !S_ISREG(st.st_mode) ||
                    !(st.st_mode & S_IXUSR))
                        continue;

                entlen = strlen(de->d_name);
                if (4 < entlen && !strcmp(de->d_name + entlen - 4, ".exe"))
                        entlen -= 4;

                if (longest < entlen)
                        longest = entlen;

                add_cmdname(de->d_name + 4, entlen-4);
        }
        closedir(dir);

        printf("git commands available in '%s'\n", exec_path);
        printf("----------------------------");
        mput_char('-', strlen(exec_path));
        putchar('\n');
        pretty_print_string_list(cmdname, longest - 4);
        putchar('\n');
}

#ifdef __GNUC__
static void cmd_usage(const char *exec_path, const char *fmt, ...)
        __attribute__((__format__(__printf__, 2, 3), __noreturn__));
#endif
static void cmd_usage(const char *exec_path, const char *fmt, ...)
{
        if (fmt) {
                va_list ap;

                va_start(ap, fmt);
                printf("git: ");
                vprintf(fmt, ap);
                va_end(ap);
                putchar('\n');
        }
        else
                puts(git_usage);

        putchar('\n');

        if(exec_path)
                list_commands(exec_path, "git-*");

        exit(1);
}

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);
}

static void show_man_page(char *git_cmd)
{
        char *page;

        if (!strncmp(git_cmd, "git", 3))
                page = git_cmd;
        else {
                int page_len = strlen(git_cmd) + 4;

                page = malloc(page_len + 1);
                strcpy(page, "git-");
                strcpy(page + 4, git_cmd);
                page[page_len] = 0;
        }

        execlp("man", "man", page, NULL);
}

static int cmd_version(int argc, char **argv, char **envp)
{
        printf("git version %s\n", GIT_VERSION);
        return 0;
}

static int cmd_help(int argc, char **argv, char **envp)
{
        char *help_cmd = argv[1];
        if (!help_cmd)
                cmd_usage(git_exec_path(), NULL);
        show_man_page(help_cmd);
        return 0;
}

#define ARRAY_SIZE(x) (sizeof(x)/sizeof(x[0]))

static void handle_internal_command(int argc, char **argv, char **envp)
{
        const char *cmd = argv[0];
        static struct cmd_struct {
                const char *cmd;
                int (*fn)(int, char **, char **);
        } commands[] = {
                { "version", cmd_version },
                { "help", cmd_help },
        };
        int i;

        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, char **argv, char **envp)
{
        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(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(exec_path, "'%s' is not a git-command", cmd);

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

        return 1;
}