#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;

#if defined(WIN32) || defined(__CYGWIN__)
#if defined(__CYGWIN__)
if ((st.st_mode & S_IXUSR) == 0)
#endif
{	/* 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;
}