#include "cache.h"
#include "builtin.h"
#include "exec_cmd.h"
#include "levenshtein.h"
#include "help.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;
}

void add_cmdname(struct cmdnames *cmds, const char *name, int len)
{
        struct cmdname *ent = xmalloc(sizeof(*ent) + len + 1);

        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 void clean_cmdnames(struct cmdnames *cmds)
{
        int i;
        for (i = 0; i < cmds->cnt; ++i)
                free(cmds->names[i]);
        free(cmds->names);
        cmds->cnt = 0;
        cmds->alloc = 0;
}

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;
}

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 = DIV_ROUND_UP(cmds->cnt, 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 int is_executable(const char *name)
{
        struct stat st;

        if (stat(name, &st) || /* stat, not lstat */
            !S_ISREG(st.st_mode))
                return 0;

#ifdef WIN32
{       /* cannot trust the executable bit, peek into the file instead */
        char buf[3] = { 0 };
        int n;
        int fd = open(name, O_RDONLY);
        st.st_mode &= ~S_IXUSR;
        if (fd >= 0) {
                n = read(fd, buf, 2);
                if (n == 2)
                        /* DOS executables start with "MZ" */
                        if (!strcmp(buf, "#!") || !strcmp(buf, "MZ"))
                                st.st_mode |= S_IXUSR;
                close(fd);
        }
}
#endif
        return st.st_mode & S_IXUSR;
}

static void list_commands_in_dir(struct cmdnames *cmds,
                                         const char *path,
                                         const char *prefix)
{
        int prefix_len;
        DIR *dir = opendir(path);
        struct dirent *de;
        struct strbuf buf = STRBUF_INIT;
        int len;

        if (!dir)
                return;
        if (!prefix)
                prefix = "git-";
        prefix_len = strlen(prefix);

        strbuf_addf(&buf, "%s/", path);
        len = buf.len;

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

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

                strbuf_setlen(&buf, len);
                strbuf_addstr(&buf, de->d_name);
                if (!is_executable(buf.buf))
                        continue;

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

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

void load_command_list(const char *prefix,
                struct cmdnames *main_cmds,
                struct cmdnames *other_cmds)
{
        const char *env_path = getenv("PATH");
        const char *exec_path = git_exec_path();

        if (exec_path) {
                list_commands_in_dir(main_cmds, exec_path, prefix);
                qsort(main_cmds->names, main_cmds->cnt,
                      sizeof(*main_cmds->names), cmdname_compare);
                uniq(main_cmds);
        }

        if (env_path) {
                char *paths, *path, *colon;
                path = paths = xstrdup(env_path);
                while (1) {
                        if ((colon = strchr(path, PATH_SEP)))
                                *colon = 0;
                        if (!exec_path || strcmp(path, exec_path))
                                list_commands_in_dir(other_cmds, path, prefix);

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

                qsort(other_cmds->names, other_cmds->cnt,
                      sizeof(*other_cmds->names), cmdname_compare);
                uniq(other_cmds);
        }
        exclude_cmds(other_cmds, main_cmds);
}

void list_commands(const char *title, struct cmdnames *main_cmds,
                   struct cmdnames *other_cmds)
{
        int i, longest = 0;

        for (i = 0; i < main_cmds->cnt; i++)
                if (longest < main_cmds->names[i]->len)
                        longest = main_cmds->names[i]->len;
        for (i = 0; i < other_cmds->cnt; i++)
                if (longest < other_cmds->names[i]->len)
                        longest = other_cmds->names[i]->len;

        if (main_cmds->cnt) {
                const char *exec_path = git_exec_path();
                printf("available %s in '%s'\n", title, exec_path);
                printf("----------------");
                mput_char('-', strlen(title) + strlen(exec_path));
                putchar('\n');
                pretty_print_string_list(main_cmds, longest);
                putchar('\n');
        }

        if (other_cmds->cnt) {
                printf("%s available from elsewhere on your $PATH\n", title);
                printf("---------------------------------------");
                mput_char('-', strlen(title));
                putchar('\n');
                pretty_print_string_list(other_cmds, longest);
                putchar('\n');
        }
}

int is_in_cmdlist(struct cmdnames *c, const char *s)
{
        int i;
        for (i = 0; i < c->cnt; i++)
                if (!strcmp(s, c->names[i]->name))
                        return 1;
        return 0;
}

static int autocorrect;
static struct cmdnames aliases;

static int git_unknown_cmd_config(const char *var, const char *value, void *cb)
{
        if (!strcmp(var, "help.autocorrect"))
                autocorrect = git_config_int(var,value);
        /* Also use aliases for command lookup */
        if (!prefixcmp(var, "alias."))
                add_cmdname(&aliases, var + 6, strlen(var + 6));

        return git_default_config(var, value, cb);
}

static int levenshtein_compare(const void *p1, const void *p2)
{
        const struct cmdname *const *c1 = p1, *const *c2 = p2;
        const char *s1 = (*c1)->name, *s2 = (*c2)->name;
        int l1 = (*c1)->len;
        int l2 = (*c2)->len;
        return l1 != l2 ? l1 - l2 : strcmp(s1, s2);
}

static void add_cmd_list(struct cmdnames *cmds, struct cmdnames *old)
{
        int i;
        ALLOC_GROW(cmds->names, cmds->cnt + old->cnt, cmds->alloc);

        for (i = 0; i < old->cnt; i++)
                cmds->names[cmds->cnt++] = old->names[i];
        free(old->names);
        old->cnt = 0;
        old->names = NULL;
}

/* An empirically derived magic number */
#define SIMILARITY_FLOOR 7
#define SIMILAR_ENOUGH(x) ((x) < SIMILARITY_FLOOR)

static const char bad_interpreter_advice[] =
        N_("'%s' appears to be a git command, but we were not\n"
        "able to execute it. Maybe git-%s is broken?");

const char *help_unknown_cmd(const char *cmd)
{
        int i, n, best_similarity = 0;
        struct cmdnames main_cmds, other_cmds;

        memset(&main_cmds, 0, sizeof(main_cmds));
        memset(&other_cmds, 0, sizeof(other_cmds));
        memset(&aliases, 0, sizeof(aliases));

        git_config(git_unknown_cmd_config, NULL);

        load_command_list("git-", &main_cmds, &other_cmds);

        add_cmd_list(&main_cmds, &aliases);
        add_cmd_list(&main_cmds, &other_cmds);
        qsort(main_cmds.names, main_cmds.cnt,
              sizeof(main_cmds.names), cmdname_compare);
        uniq(&main_cmds);

        /* This abuses cmdname->len for levenshtein distance */
        for (i = 0, n = 0; i < main_cmds.cnt; i++) {
                int cmp = 0; /* avoid compiler stupidity */
                const char *candidate = main_cmds.names[i]->name;

                /*
                 * An exact match means we have the command, but
                 * for some reason exec'ing it gave us ENOENT; probably
                 * it's a bad interpreter in the #! line.
                 */
                if (!strcmp(candidate, cmd))
                        die(_(bad_interpreter_advice), cmd, cmd);

                /* Does the candidate appear in common_cmds list? */
                while (n < ARRAY_SIZE(common_cmds) &&
                       (cmp = strcmp(common_cmds[n].name, candidate)) < 0)
                        n++;
                if ((n < ARRAY_SIZE(common_cmds)) && !cmp) {
                        /* Yes, this is one of the common commands */
                        n++; /* use the entry from common_cmds[] */
                        if (!prefixcmp(candidate, cmd)) {
                                /* Give prefix match a very good score */
                                main_cmds.names[i]->len = 0;
                                continue;
                        }
                }

                main_cmds.names[i]->len =
                        levenshtein(cmd, candidate, 0, 2, 1, 4) + 1;
        }

        qsort(main_cmds.names, main_cmds.cnt,
              sizeof(*main_cmds.names), levenshtein_compare);

        if (!main_cmds.cnt)
                die ("Uh oh. Your system reports no Git commands at all.");

        /* skip and count prefix matches */
        for (n = 0; n < main_cmds.cnt && !main_cmds.names[n]->len; n++)
                ; /* still counting */

        if (main_cmds.cnt <= n) {
                /* prefix matches with everything? that is too ambiguous */
                best_similarity = SIMILARITY_FLOOR + 1;
        } else {
                /* count all the most similar ones */
                for (best_similarity = main_cmds.names[n++]->len;
                     (n < main_cmds.cnt &&
                      best_similarity == main_cmds.names[n]->len);
                     n++)
                        ; /* still counting */
        }
        if (autocorrect && n == 1 && SIMILAR_ENOUGH(best_similarity)) {
                const char *assumed = main_cmds.names[0]->name;
                main_cmds.names[0] = NULL;
                clean_cmdnames(&main_cmds);
                fprintf(stderr, "WARNING: You called a Git command named '%s', "
                        "which does not exist.\n"
                        "Continuing under the assumption that you meant '%s'\n",
                        cmd, assumed);
                if (autocorrect > 0) {
                        fprintf(stderr, "in %0.1f seconds automatically...\n",
                                (float)autocorrect/10.0);
                        poll(NULL, 0, autocorrect * 100);
                }
                return assumed;
        }

        fprintf(stderr, "git: '%s' is not a git command. See 'git --help'.\n", cmd);

        if (SIMILAR_ENOUGH(best_similarity)) {
                fprintf(stderr, "\nDid you mean %s?\n",
                        n < 2 ? "this": "one of these");

                for (i = 0; i < n; i++)
                        fprintf(stderr, "\t%s\n", main_cmds.names[i]->name);
        }

        exit(1);
}

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