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

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

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

static struct cmdnames {
        int alloc;
        int cnt;
        struct cmdname {
                size_t len;
                char name[1];
        } **names;
} main_cmds, other_cmds;

static void add_cmdname(struct cmdnames *cmds, const char *name, int len)
{
        struct cmdname *ent = xmalloc(sizeof(*ent) + len);

        ent->len = len;
        memcpy(ent->name, name, len);
        ent->name[len] = 0;

        ALLOC_GROW(cmds->names, cmds->cnt + 1, cmds->alloc);
        cmds->names[cmds->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 uniq(struct cmdnames *cmds)
{
        int i, j;

        if (!cmds->cnt)
                return;

        for (i = j = 1; i < cmds->cnt; i++)
                if (strcmp(cmds->names[i]->name, cmds->names[i-1]->name))
                        cmds->names[j++] = cmds->names[i];

        cmds->cnt = j;
}

static void exclude_cmds(struct cmdnames *cmds, struct cmdnames *excludes)
{
        int ci, cj, ei;
        int cmp;

        ci = cj = ei = 0;
        while (ci < cmds->cnt && ei < excludes->cnt) {
                cmp = strcmp(cmds->names[ci]->name, excludes->names[ei]->name);
                if (cmp < 0)
                        cmds->names[cj++] = cmds->names[ci++];
                else if (cmp == 0)
                        ci++, ei++;
                else if (cmp > 0)
                        ei++;
        }

        while (ci < cmds->cnt)
                cmds->names[cj++] = cmds->names[ci++];

        cmds->cnt = cj;
}

static void pretty_print_string_list(struct cmdnames *cmds, 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 = (cmds->cnt + cols - 1) / cols;

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

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

static unsigned int list_commands_in_dir(struct cmdnames *cmds,
                                         const char *path)
{
        unsigned int longest = 0;
        const char *prefix = "git-";
        int prefix_len = strlen(prefix);
        DIR *dir = opendir(path);
        struct dirent *de;

        if (!dir || chdir(path))
                return 0;

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

                if (prefixcmp(de->d_name, prefix))
                        continue;

                if (stat(de->d_name, &st) || /* stat, not lstat */
                    !S_ISREG(st.st_mode) ||
                    !(st.st_mode & S_IXUSR))
                        continue;

                entlen = strlen(de->d_name) - prefix_len;
                if (has_extension(de->d_name, ".exe"))
                        entlen -= 4;

                if (longest < entlen)
                        longest = entlen;

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

        return longest;
}

static void list_commands(void)
{
        unsigned int longest = 0;
        unsigned int len;
        const char *env_path = getenv("PATH");
        char *paths, *path, *colon;
        const char *exec_path = git_exec_path();

        if (exec_path)
                longest = list_commands_in_dir(&main_cmds, exec_path);

        if (!env_path) {
                fprintf(stderr, "PATH not set\n");
                exit(1);
        }

        path = paths = xstrdup(env_path);
        while (1) {
                if ((colon = strchr(path, ':')))
                        *colon = 0;

                len = list_commands_in_dir(&other_cmds, path);
                if (len > longest)
                        longest = len;

                if (!colon)
                        break;
                path = colon + 1;
        }
        free(paths);

        qsort(main_cmds.names, main_cmds.cnt,
              sizeof(*main_cmds.names), cmdname_compare);
        uniq(&main_cmds);

        qsort(other_cmds.names, other_cmds.cnt,
              sizeof(*other_cmds.names), cmdname_compare);
        uniq(&other_cmds);
        exclude_cmds(&other_cmds, &main_cmds);

        if (main_cmds.cnt) {
                printf("available git commands in '%s'\n", exec_path);
                printf("----------------------------");
                mput_char('-', strlen(exec_path));
                putchar('\n');
                pretty_print_string_list(&main_cmds, longest);
                putchar('\n');
        }

        if (other_cmds.cnt) {
                printf("git commands available from elsewhere on your $PATH\n");
                printf("---------------------------------------------------\n");
                pretty_print_string_list(&other_cmds, longest);
                putchar('\n');
        }
}

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));
                puts(common_cmds[i].help);
        }
}

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

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

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

void help_unknown_cmd(const char *cmd)
{
        fprintf(stderr, "git: '%s' is not a git-command. See 'git --help'.\n", cmd);
        exit(1);
}

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

int cmd_help(int argc, const char **argv, const char *prefix)
{
        const char *help_cmd = argc > 1 ? argv[1] : NULL;

        if (!help_cmd) {
                printf("usage: %s\n\n", git_usage_string);
                list_common_cmds_help();
                exit(0);
        }

        else if (!strcmp(help_cmd, "--all") || !strcmp(help_cmd, "-a")) {
                printf("usage: %s\n\n", git_usage_string);
                list_commands();
                exit(0);
        }

        else
                show_man_page(help_cmd);

        return 0;
}