/*
 * The helpers that no single page owns, along with the process wide state
 * every page reads. Repositories are registered here as cgitrc is parsed, the
 * reference and commit records that the renderers list are built and freed
 * here, and git's diff machinery is wrapped so a caller is handed whole
 * filepairs or whole lines instead of xdiff buffers.
 */

#define USE_THE_REPOSITORY_VARIABLE

#include "cgit.h"
#include "parsing.h"
#include "shared.h"

#define MACRO_EXPANSION_BUFSIZE (1024 * 8)

// The number of context lines git itself defaults to.
#define DEFAULT_DIFF_CONTEXT 3

typedef struct {
	const char *name;
	const char *value;
} env_var;

struct cgit_repolist cgit_repolist;
struct cgit_context ctx;
char *cgit_default_repo_desc = "[no description]";

// A diff line that arrived in pieces and is still waiting for its end, see
// emit_line.
static char *fragment;
static int fragment_len;

static void free_refinfo(struct refinfo *ref)
{
	free((char *)ref->refname);
	switch (ref->object->type) {
	case OBJ_TAG:
		cgit_free_taginfo(ref->tag);
		break;
	case OBJ_COMMIT:
		cgit_free_commitinfo(ref->commit);
		break;
	}
	free(ref);
}

static struct refinfo *make_refinfo(const char *refname,
				    const struct object_id *oid)
{
	struct refinfo *ref;

	ref = xcalloc(1, sizeof(struct refinfo));
	ref->refname = xstrdup(refname);
	ref->object = parse_object(the_repository, oid);
	if (!ref->object) {
		free((char *)ref->refname);
		free(ref);
		return NULL;
	}
	switch (ref->object->type) {
	case OBJ_TAG:
		ref->tag = cgit_parse_tag((struct tag *)ref->object);
		break;
	case OBJ_COMMIT:
		ref->commit = cgit_parse_commit((struct commit *)ref->object);
		break;
	}
	return ref;
}

static int load_mmfile(mmfile_t *file, const struct object_id *oid)
{
	enum object_type type;

	// A null oid is the absent side of an add or a delete, and diffs as an
	// empty file rather than as a failure.
	if (is_null_oid(oid)) {
		file->ptr = (char *)"";
		file->size = 0;
		return 1;
	}

	file->ptr = odb_read_object(the_repository->objects, oid, &type,
				    (unsigned long *)&file->size);
	// odb_read_object leaves size untouched when it fails, so the caller
	// has to be told rather than handed a buffer with an unset length.
	return file->ptr != NULL;
}

/*
 * The test is on the oid rather than on the size, because load_mmfile uses a
 * literal only for a null oid, and a real blob that happens to be empty does
 * own its buffer.
 */
static void release_mmfile(mmfile_t *file, const struct object_id *oid)
{
	if (!is_null_oid(oid))
		free(file->ptr);
}

/*
 * Xdiff emits buffers that need not end on a line boundary, so a trailing
 * fragment is held back and joined with whatever arrives next. Git's own
 * xdiff_outf keeps that fragment in a callback struct, which is not an option
 * here because priv already carries the caller's function.
 */
static int emit_line(void *priv, mmbuffer_t *mb, int nbuf)
{
	linediff_fn emit = (linediff_fn)priv;
	int i;

	for (i = 0; i < nbuf; i++) {
		if (mb[i].ptr[mb[i].size-1] != '\n') {
			fragment = xrealloc(fragment, fragment_len + mb[i].size);
			memcpy(fragment + fragment_len, mb[i].ptr, mb[i].size);
			fragment_len += mb[i].size;
			continue;
		}

		if (!fragment) {
			emit(mb[i].ptr, mb[i].size);
			continue;
		}
		fragment = xrealloc(fragment, fragment_len + mb[i].size);
		memcpy(fragment + fragment_len, mb[i].ptr, mb[i].size);
		emit(fragment, fragment_len + mb[i].size);
		free(fragment);
		fragment = NULL;
		fragment_len = 0;
	}
	if (fragment) {
		emit(fragment, fragment_len);
		free(fragment);
		fragment = NULL;
		fragment_len = 0;
	}
	return 0;
}

// Takes an unsigned char because a byte over 0x7f is negative in a plain
// char wherever char is signed, and a negative one is not a value the ctype
// tests are defined for.
static int is_token_char(unsigned char c)
{
	return isalnum(c) || c == '_';
}

/*
 * Replace the variable name held at name with its value from the environment,
 * writing at most room bytes including the terminator, and return where the
 * text now ends.
 */
static char *expand_macro(char *name, size_t room)
{
	char *value;
	size_t len;

	len = 0;
	value = getenv(name);
	if (value) {
		len = strlen(value) + 1;
		if (len > room)
			len = room;
		strlcpy(name, value, len);
		--len;
	}
	return name + len;
}

int cgit_die_unless_zero(int result, const char *msg)
{
	if (result != 0)
		die_errno("%s", msg);
	return result;
}

int cgit_die_unless_positive(int result, const char *msg)
{
	if (result <= 0)
		die_errno("%s", msg);
	return result;
}

int cgit_die_unless_non_negative(int result, const char *msg)
{
	if (result < 0)
		die_errno("%s", msg);
	return result;
}

struct cgit_repo *cgit_add_repo(const char *url)
{
	struct cgit_repo *repo;

	if (++cgit_repolist.count > cgit_repolist.length) {
		if (cgit_repolist.length == 0)
			cgit_repolist.length = 8;
		else
			cgit_repolist.length *= 2;
		cgit_repolist.repos = xrealloc(cgit_repolist.repos,
					       cgit_repolist.length *
					       sizeof(struct cgit_repo));
	}

	repo = &cgit_repolist.repos[cgit_repolist.count-1];
	memset(repo, 0, sizeof(struct cgit_repo));
	repo->url = cgit_trim_end(url, '/');
	if (repo->url)
		*strchrnul(repo->url, '\n') = '\0';
	repo->name = repo->url;
	repo->path = NULL;
	repo->desc = cgit_default_repo_desc;
	repo->extra_head_content = NULL;
	repo->owner = NULL;
	repo->section = ctx.cfg.section;
	repo->snapshots = ctx.cfg.snapshots;
	repo->enable_blame = ctx.cfg.enable_blame;
	repo->enable_commit_graph = ctx.cfg.enable_commit_graph;
	repo->enable_follow_links = ctx.cfg.enable_follow_links;
	repo->enable_log_filecount = ctx.cfg.enable_log_filecount;
	repo->enable_log_linecount = ctx.cfg.enable_log_linecount;
	repo->enable_remote_branches = ctx.cfg.enable_remote_branches;
	repo->enable_subject_links = ctx.cfg.enable_subject_links;
	repo->enable_html_serving = ctx.cfg.enable_html_serving;
	repo->enable_stats = ctx.cfg.enable_stats;
	repo->max_stats = ctx.cfg.max_stats;
	repo->branch_sort = ctx.cfg.branch_sort;
	repo->commit_sort = ctx.cfg.commit_sort;
	repo->module_link = ctx.cfg.module_link;
	repo->readme = ctx.cfg.readme;
	repo->mtime = -1;
	repo->about_filter = ctx.cfg.about_filter;
	repo->commit_filter = ctx.cfg.commit_filter;
	repo->source_filter = ctx.cfg.source_filter;
	repo->email_filter = ctx.cfg.email_filter;
	repo->clone_url = ctx.cfg.clone_url;
	repo->submodules.strdup_strings = 1;
	repo->hide = repo->ignore = 0;
	return repo;
}

struct cgit_repo *cgit_get_repoinfo(const char *url)
{
	int i;
	struct cgit_repo *repo;

	for (i = 0; i < cgit_repolist.count; i++) {
		repo = &cgit_repolist.repos[i];
		if (repo->ignore)
			continue;
		if (!strcmp(repo->url, url))
			return repo;
	}
	return NULL;
}

void cgit_free_commitinfo(struct commitinfo *info)
{
	free(info->author);
	free(info->author_email);
	free(info->committer);
	free(info->committer_email);
	free(info->subject);
	free(info->msg);
	free(info->msg_encoding);
	free(info);
}

char *cgit_trim_end(const char *str, char c)
{
	size_t len;

	if (str == NULL)
		return NULL;
	len = strlen(str);
	while (len > 0 && str[len - 1] == c)
		len--;
	if (len == 0)
		return NULL;
	return xstrndup(str, len);
}

char *cgit_ensure_end(const char *str, char c)
{
	size_t len = strlen(str);
	char *result;

	if (len && str[len - 1] == c)
		return xstrndup(str, len);

	result = xmalloc(len + 2);
	memcpy(result, str, len);
	result[len] = '/';
	result[len + 1] = '\0';
	return result;
}

void strbuf_ensure_end(struct strbuf *sb, char c)
{
	if (!sb->len || sb->buf[sb->len - 1] != c)
		strbuf_addch(sb, c);
}

static void add_ref(struct reflist *list, struct refinfo *ref)
{
	size_t size;

	if (list->count >= list->alloc) {
		list->alloc += (list->alloc ? list->alloc : 4);
		size = list->alloc * sizeof(struct refinfo *);
		list->refs = xrealloc(list->refs, size);
	}
	list->refs[list->count++] = ref;
}

void cgit_free_taginfo(struct taginfo *info)
{
	// NULL is accepted because cgit_parse_tag returns it for a tag object
	// that cannot be read, and a ref left holding that still gets freed
	// along with the rest of its list.
	if (!info)
		return;
	free(info->tagger);
	free(info->tagger_email);
	free(info->msg);
	free(info);
}

void cgit_free_reflist_inner(struct reflist *list)
{
	int i;

	for (i = 0; i < list->count; i++)
		free_refinfo(list->refs[i]);
	free(list->refs);
}

int cgit_refs_cb(const struct reference *ref, void *cb_data)
{
	struct reflist *list = (struct reflist *)cb_data;
	struct refinfo *info = make_refinfo(ref->name, ref->oid);

	if (info)
		add_ref(list, info);
	return 0;
}

void cgit_diff_tree_cb(struct diff_queue_struct *q,
		       struct diff_options *options, void *data)
{
	filepair_fn fn = (filepair_fn)data;
	int i;

	for (i = 0; i < q->nr; i++) {
		// An unmerged path has no single pair of blobs to show.
		if (q->queue[i]->status == 'U')
			continue;
		fn(q->queue[i]);
	}
}

int cgit_diff_files(const struct object_id *old_oid,
		    const struct object_id *new_oid, unsigned long *old_size,
		    unsigned long *new_size, int *binary, int context,
		    int ignorews, linediff_fn fn)
{
	mmfile_t old_file, new_file;
	xpparam_t diff_params;
	xdemitconf_t emit_params;
	xdemitcb_t emit_cb;
	unsigned long old_bytes = 0, new_bytes = 0;

	// Read the object headers first so an oversized blob is never inflated
	// into memory just to be diffed. Reporting it as binary suppresses
	// inlining the same way max-blob-size does in the other views.
	if (!is_null_oid(old_oid) &&
	    odb_read_object_info(the_repository->objects, old_oid, &old_bytes) < 0)
		return 1;
	if (!is_null_oid(new_oid) &&
	    odb_read_object_info(the_repository->objects, new_oid, &new_bytes) < 0)
		return 1;

	*old_size = old_bytes;
	*new_size = new_bytes;

	if (ctx.cfg.max_blob_size &&
	    (old_bytes / 1024 > (unsigned long)ctx.cfg.max_blob_size ||
	     new_bytes / 1024 > (unsigned long)ctx.cfg.max_blob_size)) {
		*binary = 1;
		return 0;
	}

	if (!load_mmfile(&old_file, old_oid))
		return 1;
	if (!load_mmfile(&new_file, new_oid)) {
		release_mmfile(&old_file, old_oid);
		return 1;
	}

	if (buffer_is_binary(old_file.ptr, old_file.size) ||
	    buffer_is_binary(new_file.ptr, new_file.size)) {
		*binary = 1;
		release_mmfile(&old_file, old_oid);
		release_mmfile(&new_file, new_oid);
		return 0;
	}

	memset(&diff_params, 0, sizeof(diff_params));
	memset(&emit_params, 0, sizeof(emit_params));
	memset(&emit_cb, 0, sizeof(emit_cb));
	diff_params.flags = XDF_NEED_MINIMAL;
	if (ignorews)
		diff_params.flags |= XDF_IGNORE_WHITESPACE;
	emit_params.ctxlen = context > 0 ? context : DEFAULT_DIFF_CONTEXT;
	emit_params.flags = XDL_EMIT_FUNCNAMES;
	emit_cb.out_line = emit_line;
	emit_cb.priv = fn;
	xdl_diff(&old_file, &new_file, &diff_params, &emit_params, &emit_cb);
	release_mmfile(&old_file, old_oid);
	release_mmfile(&new_file, new_oid);
	return 0;
}

void cgit_diff_tree(const struct object_id *old_oid,
		    const struct object_id *new_oid,
		    filepair_fn fn, const char *prefix, int ignorews)
{
	struct diff_options opt;
	struct pathspec_item *item;

	repo_diff_setup(the_repository, &opt);
	opt.output_format = DIFF_FORMAT_CALLBACK;
	opt.detect_rename = 1;
	opt.rename_limit = ctx.cfg.renamelimit;
	opt.flags.recursive = 1;
	if (ignorews)
		DIFF_XDL_SET(&opt, IGNORE_WHITESPACE);
	opt.format_callback = cgit_diff_tree_cb;
	opt.format_callback_data = fn;
	if (prefix) {
		item = xcalloc(1, sizeof(*item));
		item->match = xstrdup(prefix);
		item->len = strlen(prefix);
		opt.pathspec.nr = 1;
		opt.pathspec.items = item;
	}
	diff_setup_done(&opt);

	if (old_oid && !is_null_oid(old_oid))
		diff_tree_oid(old_oid, new_oid, "", &opt);
	else
		diff_root_tree_oid(new_oid, "", &opt);
	diffcore_std(&opt);
	diff_flush(&opt);
}

void cgit_diff_commit(struct commit *commit, filepair_fn fn, const char *prefix)
{
	const struct object_id *old_oid = NULL;

	if (commit->parents)
		old_oid = &commit->parents->item->object.oid;
	cgit_diff_tree(old_oid, &commit->object.oid, fn, prefix,
		       ctx.qry.ignorews);
}

/*
 * Git's parse_date_format dies on anything it does not recognize, which would
 * turn a typo in cgitrc into a failed request, so only the formats cgit
 * documents reach it.
 */
void cgit_parse_date_format(const char *format, struct date_mode *mode)
{
	static const char * const names[] = {
		"default", "human", "iso", "iso-strict", "iso8601",
		"iso8601-strict", "local", "raw", "relative", "rfc",
		"rfc2822", "short", "unix",
	};
	const char *rest;
	size_t i;

	if (skip_prefix(format, "format:", &rest)) {
		// An empty strftime format would render every date blank.
		if (*rest)
			parse_date_format(format, mode);
		return;
	}

	for (i = 0; i < ARRAY_SIZE(names); i++) {
		if (!skip_prefix(format, names[i], &rest))
			continue;
		// "iso" also prefixes "iso8601", so a partial hit is skipped.
		if (*rest && strcmp(rest, "-local"))
			continue;
		parse_date_format(format, mode);
		return;
	}
}

void cgit_prepare_repo_env(struct cgit_repo *repo)
{
	const env_var vars[] = {
		{ .name = "CGIT_REPO_URL", .value = repo->url },
		{ .name = "CGIT_REPO_NAME", .value = repo->name },
		{ .name = "CGIT_REPO_PATH", .value = repo->path },
		{ .name = "CGIT_REPO_OWNER", .value = repo->owner },
		{ .name = "CGIT_REPO_DEFBRANCH", .value = repo->defbranch },
		{ .name = "CGIT_REPO_SECTION", .value = repo->section },
		{ .name = "CGIT_REPO_CLONE_URL", .value = repo->clone_url }
	};
	size_t i;

	for (i = 0; i < ARRAY_SIZE(vars); i++)
		if (vars[i].value && setenv(vars[i].name, vars[i].value, 1))
			fprintf(stderr,
				"cgit warning: failed to set env: %s=%s\n",
				vars[i].name, vars[i].value);
}

int cgit_read_first_line(const char *path, char **buf, size_t *size)
{
	int fd, err;
	ssize_t got;
	struct stat st;

	fd = open(path, O_RDONLY);
	if (fd == -1)
		return errno;
	if (fstat(fd, &st)) {
		err = errno;
		close(fd);
		return err;
	}
	if (!S_ISREG(st.st_mode)) {
		close(fd);
		return EISDIR;
	}
	*buf = xmalloc(st.st_size + 1);
	got = read_in_full(fd, *buf, st.st_size);
	err = errno;
	if (got < 0) {
		free(*buf);
		*buf = NULL;
		*size = 0;
		close(fd);
		return err;
	}
	*size = got;
	(*buf)[*size] = '\0';
	*strchrnul(*buf, '\n') = '\0';
	close(fd);
	return (*size == (size_t)st.st_size ? 0 : err);
}

char *cgit_strdup_first_line(const char *text)
{
	char *line = xstrdup(text);
	*strchrnul(line, '\n') = '\0';
	return line;
}

char *cgit_expand_macros(const char *text)
{
	static char result[MACRO_EXPANSION_BUFSIZE];
	char *limit = result + MACRO_EXPANSION_BUFSIZE - 1;
	char *out, *start;

	out = result;
	start = NULL;
	while (out < limit && text && *text) {
		*out = *text;
		if (start) {
			if (!is_token_char(*text)) {
				if (out - start > 0) {
					*out = '\0';
					out = expand_macro(start, limit - start) - 1;
				}
				start = NULL;
				// Step back so the character that ended the
				// token is written again past the expansion,
				// where it may open a token of its own.
				text--;
			}
			out++;
			text++;
			continue;
		}
		if (*text == '$') {
			start = out;
			text++;
			continue;
		}
		out++;
		text++;
	}
	*out = '\0';
	if (start && out - start > 0) {
		out = expand_macro(start, limit - start);
		*out = '\0';
	}
	return result;
}

char *cgit_get_mimetype_for_filename(const char *filename)
{
	const char *ext;
	char *type, line[1024];
	struct string_list fields = STRING_LIST_INIT_NODUP;
	size_t i;
	FILE *file;
	struct string_list_item *entry;

	if (!filename)
		return NULL;

	ext = strrchr(filename, '.');
	if (!ext)
		return NULL;
	++ext;
	if (!ext[0])
		return NULL;
	entry = string_list_lookup(&ctx.cfg.mimetypes, ext);
	if (entry)
		return xstrdup(entry->util);

	if (!ctx.cfg.mimetype_file)
		return NULL;
	file = fopen(ctx.cfg.mimetype_file, "r");
	if (!file)
		return NULL;
	while (fgets(line, sizeof(line), file)) {
		if (!line[0] || line[0] == '#')
			continue;
		// A line of a mime.types file is one type followed by every
		// extension that maps to it.
		string_list_split_in_place(&fields, line, " \t\r\n", -1);
		string_list_remove_empty_items(&fields, 0);
		type = fields.items[0].string;
		for (i = 1; i < fields.nr; i++) {
			if (!strcasecmp(ext, fields.items[i].string)) {
				fclose(file);
				return xstrdup(type);
			}
		}
		string_list_clear(&fields, 0);
	}
	fclose(file);
	return NULL;
}