/*
 * Copyright (C) the libgit2 contributors. All rights reserved.
 *
 * This file is part of libgit2, distributed under the GNU GPL v2 with
 * a Linking Exception. For full terms see the included COPYING file.
 */

#include "fetch.h"

#include "git2/oid.h"
#include "git2/refs.h"
#include "git2/revwalk.h"
#include "git2/transport.h"
#include "git2/sys/remote.h"

#include "oid.h"
#include "remote.h"
#include "refspec.h"
#include "pack.h"
#include "netops.h"
#include "repository.h"
#include "refs.h"
#include "transports/smart.h"

static int maybe_want(git_remote *remote, git_remote_head *head, git_refspec *tagspec, git_remote_autotag_option_t tagopt)
{
	int match = 0, valid;

	if (git_reference_name_is_valid(&valid, head->name) < 0)
		return -1;

	if (!valid)
		return 0;

	if (tagopt == GIT_REMOTE_DOWNLOAD_TAGS_ALL) {
		/*
		 * If tagopt is --tags, always request tags
		 * in addition to the remote's refspecs
		 */
		if (git_refspec_src_matches(tagspec, head->name))
			match = 1;
	}

	if (!match && git_remote__matching_refspec(remote, head->name))
		match = 1;

	if (!match)
		return 0;

	return git_vector_insert(&remote->refs, head);
}

static int mark_local(git_remote *remote)
{
	git_remote_head *head;
	git_odb *odb;
	size_t i;

	if (git_repository_odb__weakptr(&odb, remote->repo) < 0)
		return -1;

	git_vector_foreach(&remote->refs, i, head) {
		/* If we have the object, mark it so we don't ask for it */
		if (git_odb_exists(odb, &head->oid))
			head->local = 1;
		else
			remote->need_pack = 1;
	}

	return 0;
}

static int maybe_want_oid(git_remote *remote, git_refspec *spec)
{
	git_remote_head *oid_head;

	oid_head = git__calloc(1, sizeof(git_remote_head));
	GIT_ERROR_CHECK_ALLOC(oid_head);

	git_oid__fromstr(&oid_head->oid, spec->src, GIT_OID_SHA1);

	if (spec->dst) {
		oid_head->name = git__strdup(spec->dst);
		GIT_ERROR_CHECK_ALLOC(oid_head->name);
	}

	if (git_vector_insert(&remote->local_heads, oid_head) < 0 ||
	    git_vector_insert(&remote->refs, oid_head) < 0)
		return -1;

	return 0;
}

static int filter_wants(git_remote *remote, const git_fetch_options *opts)
{
	git_remote_head **heads;
	git_refspec tagspec, head, *spec;
	int error = 0;
	git_odb *odb;
	size_t i, heads_len;
	unsigned int remote_caps;
	unsigned int oid_mask = GIT_REMOTE_CAPABILITY_TIP_OID |
	                        GIT_REMOTE_CAPABILITY_REACHABLE_OID;
	git_remote_autotag_option_t tagopt = remote->download_tags;

	if (opts && opts->download_tags != GIT_REMOTE_DOWNLOAD_TAGS_UNSPECIFIED)
		tagopt = opts->download_tags;

	git_vector_clear(&remote->refs);
	if ((error = git_refspec__parse(&tagspec, GIT_REFSPEC_TAGS, true)) < 0)
		return error;

	/*
	 * The fetch refspec can be NULL, and what this means is that the
	 * user didn't specify one. This is fine, as it means that we're
	 * not interested in any particular branch but just the remote's
	 * HEAD, which will be stored in FETCH_HEAD after the fetch.
	 */
	if (remote->active_refspecs.length == 0) {
		if ((error = git_refspec__parse(&head, "HEAD", true)) < 0)
			goto cleanup;

		error = git_refspec__dwim_one(&remote->active_refspecs, &head, &remote->refs);
		git_refspec__dispose(&head);

		if (error < 0)
			goto cleanup;
	}

	if ((error = git_repository_odb__weakptr(&odb, remote->repo)) < 0)
		goto cleanup;

	if ((error = git_remote_ls((const git_remote_head ***)&heads, &heads_len, remote)) < 0 ||
	    (error = git_remote_capabilities(&remote_caps, remote)) < 0)
		goto cleanup;

	/* Handle remote heads */
	for (i = 0; i < heads_len; i++) {
		if ((error = maybe_want(remote, heads[i], &tagspec, tagopt)) < 0)
			goto cleanup;
	}

	/* Handle explicitly specified OID specs */
	git_vector_foreach(&remote->active_refspecs, i, spec) {
		if (!git_oid__is_hexstr(spec->src, GIT_OID_SHA1))
			continue;

		if (!(remote_caps & oid_mask)) {
			git_error_set(GIT_ERROR_INVALID, "cannot fetch a specific object from the remote repository");
			error = -1;
			goto cleanup;
		}

		if ((error = maybe_want_oid(remote, spec)) < 0)
			goto cleanup;
	}

	error = mark_local(remote);

cleanup:
	git_refspec__dispose(&tagspec);

	return error;
}

/*
 * In this first version, we push all our refs in and start sending
 * them out. When we get an ACK we hide that commit and continue
 * traversing until we're done
 */
int git_fetch_negotiate(git_remote *remote, const git_fetch_options *opts)
{
	git_transport *t = remote->transport;

	remote->need_pack = 0;

	if (filter_wants(remote, opts) < 0)
		return -1;

	/* Don't try to negotiate when we don't want anything */
	if (!remote->need_pack)
		return 0;

	/*
	 * Now we have everything set up so we can start tell the
	 * server what we want and what we have.
	 */
	remote->nego.refs = (const git_remote_head * const *)remote->refs.contents;
	remote->nego.count = remote->refs.length;
	remote->nego.depth = opts->depth;
	remote->nego.shallow_roots = git__malloc(sizeof(git_shallowarray));

	git_array_init(remote->nego.shallow_roots->array);

	git_repository__shallow_roots(&remote->nego.shallow_roots->array, remote->repo);

	return t->negotiate_fetch(t,
		remote->repo,
		&remote->nego);
}

int git_fetch_download_pack(git_remote *remote)
{
	git_transport *t = remote->transport;
	int error;

	if (!remote->need_pack)
		return 0;

	if ((error = t->download_pack(t, remote->repo, &remote->stats)) < 0)
		return error;

	if ((error = git_repository__shallow_roots_write(remote->repo, remote->nego.shallow_roots->array)) < 0)
		return error;

	return 0;
}

int git_fetch_options_init(git_fetch_options *opts, unsigned int version)
{
	GIT_INIT_STRUCTURE_FROM_TEMPLATE(
		opts, version, git_fetch_options, GIT_FETCH_OPTIONS_INIT);
	return 0;
}

#ifndef GIT_DEPRECATE_HARD
int git_fetch_init_options(git_fetch_options *opts, unsigned int version)
{
	return git_fetch_options_init(opts, version);
}
#endif
