/*
 * builtin-help.c
 *
 * Builtin help-related commands (help, usage, version)
 */
#include <sys/ioctl.h>
#include "cache.h"
#include "builtin.h"
#include "exec_cmd.h"
#include "common-cmds.h"

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

/* most GUI terminals 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');
}

static void list_common_cmds_help(void)
{
        int i, longest = 0;

        for (i = 0; i < ARRAY_SIZE(common_cmds); i++) {
                if (longest < strlen(common_cmds[i].name))
                        longest = strlen(common_cmds[i].name);
        }

        puts("The most commonly used git commands are:");
        for (i = 0; i < ARRAY_SIZE(common_cmds); i++) {
                printf("    %s", common_cmds[i].name);
                mput_char(' ', longest - strlen(common_cmds[i].name) + 4);
                puts(common_cmds[i].help);
        }
        puts("(use 'git help -a' to get a list of all installed git commands)");
}

void cmd_usage(int show_all, 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);

        if (exec_path) {
                putchar('\n');
                if (show_all)
                        list_commands(exec_path, "git-*");
                else
                        list_common_cmds_help();
        }

        exit(1);
}

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

        if (!strncmp(git_cmd, "git", 3))
                page = git_cmd;
        else {
                int page_len = strlen(git_cmd) + 4;
                char *p = malloc(page_len + 1);
                strcpy(p, "git-");
                strcpy(p + 4, git_cmd);
                p[page_len] = 0;
                page = p;
        }

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

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

int cmd_help(int argc, const char **argv, char **envp)
{
        const char *help_cmd = argv[1];
        if (!help_cmd)
                cmd_usage(0, git_exec_path(), NULL);
        else if (!strcmp(help_cmd, "--all") || !strcmp(help_cmd, "-a"))
                cmd_usage(1, git_exec_path(), NULL);
        else
                show_man_page(help_cmd);
        return 0;
}