/*
 * This file is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License, version 2,
 * as published by the Free Software Foundation.
 *
 * In addition to the permissions in the GNU General Public License,
 * the authors give you unlimited permission to link the compiled
 * version of this file into combinations with other programs,
 * and to distribute those combinations without any restriction
 * coming from the use of this file.  (The General Public License
 * restrictions do apply in other respects; for example, they cover
 * modification of the file, and distribution when not linked into
 * a combined executable.)
 *
 * This file is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; see the file COPYING.  If not, write to
 * the Free Software Foundation, 51 Franklin Street, Fifth Floor,
 * Boston, MA 02110-1301, USA.
 */

#include <time.h>

#include "common.h"
#include "commit.h"
#include "revwalk.h"
#include "git/odb.h"

#define COMMIT_PRINT(commit) {\
    char oid[41]; oid[40] = 0;\
    git_oid_fmt(oid, &commit->object.id);\
    printf("Oid: %s | In degree: %d | Time: %u\n", oid, commit->in_degree, commit->commit_time);\
}

const git_oid *git_commit_id(git_commit *c)
{
	return &c->object.id;
}

void git_commit__mark_uninteresting(git_commit *commit)
{
	if (commit == NULL)
		return;

	git_commit_node *parents = commit->parents.head;

	commit->uninteresting = 1;

	while (parents) {
		parents->commit->uninteresting = 1;
		parents = parents->next;
	}
}

git_commit *git_commit_parse(git_revpool *pool, const git_oid *id)
{
	git_commit *commit = NULL;

	if ((commit = git_commit_lookup(pool, id)) == NULL)
		return NULL;

	if (git_commit_parse_existing(commit) < 0)
		goto error_cleanup;

	return commit;

error_cleanup:
	free(commit);
	return NULL;
}

int git_commit_parse_existing(git_commit *commit)
{
	git_obj commit_obj;

	if (commit->parsed)
		return 0;

	if (git_odb_read(&commit_obj, commit->object.pool->db, &commit->object.id) < 0)
		return GIT_ENOTFOUND;

	if (commit_obj.type != GIT_OBJ_COMMIT)
		goto error_cleanup;

	if (git_commit__parse_buffer(commit, commit_obj.data, commit_obj.len) < 0)
		goto error_cleanup;

	git_obj_close(&commit_obj);

	return 0;

error_cleanup:
	git_obj_close(&commit_obj);
	return -1;
}

git_commit *git_commit_lookup(git_revpool *pool, const git_oid *id)
{
	git_commit *commit = NULL;

	if (pool == NULL)
		return NULL;

	commit = (git_commit *)git_revpool_table_lookup(pool->commits, id);
	if (commit != NULL)
		return commit;

	commit = git__malloc(sizeof(git_commit));

	if (commit == NULL)
		return NULL;

	memset(commit, 0x0, sizeof(git_commit));

	// Initialize parent object
	git_oid_cpy(&commit->object.id, id);
	commit->object.pool = pool;

	git_revpool_table_insert(pool->commits, (git_revpool_object *)commit);

	return commit;
}

int git_commit__parse_time(time_t *commit_time, char *buffer, const char *buffer_end)
{
	if (memcmp(buffer, "author ", 7) != 0)
		return GIT_EOBJCORRUPTED;

	buffer = memchr(buffer, '\n', buffer_end - buffer);
	if (buffer == 0 || ++buffer >= buffer_end)
		return GIT_EOBJCORRUPTED;

	if (memcmp(buffer, "committer ", 10) != 0)
		return GIT_EOBJCORRUPTED;

	buffer = memchr(buffer, '>', buffer_end - buffer);
	if (buffer == 0 || ++buffer >= buffer_end)
		return GIT_EOBJCORRUPTED;

	*commit_time = strtol(buffer, &buffer, 10);

	if (*commit_time == 0)
		return GIT_EOBJCORRUPTED;

	buffer = memchr(buffer, '\n', buffer_end - buffer);
	if (buffer == 0 || ++buffer >= buffer_end)
		return GIT_EOBJCORRUPTED;

	return (buffer < buffer_end) ? 0 : -1;
}

int git_commit__parse_oid(git_oid *oid, char **buffer_out, const char *buffer_end, const char *header)
{
	const size_t sha_len = GIT_OID_HEXSZ;
	const size_t header_len = strlen(header);

	char *buffer = *buffer_out;

	if (buffer + (header_len + sha_len + 1) > buffer_end)
		return GIT_EOBJCORRUPTED;

	if (memcmp(buffer, header, header_len) != 0)
		return GIT_EOBJCORRUPTED;

	if (buffer[header_len + sha_len] != '\n')
		return GIT_EOBJCORRUPTED;

	if (git_oid_mkstr(oid, buffer + header_len) < 0)
		return GIT_EOBJCORRUPTED;

	*buffer_out = buffer + (header_len + sha_len + 1);

	return 0;
}

int git_commit__parse_buffer(git_commit *commit, void *data, size_t len)
{
	char *buffer = (char *)data;
	const char *buffer_end = (char *)data + len;

	git_oid oid;

	if (commit->parsed)
		return 0;

	if (git_commit__parse_oid(&oid, &buffer, buffer_end, "tree ") < 0)
		return GIT_EOBJCORRUPTED;

	/*
	 * TODO: load tree into commit object
	 * TODO: commit grafts!
	 */

	while (git_commit__parse_oid(&oid, &buffer, buffer_end, "parent ") == 0) {
		git_commit *parent;

		if ((parent = git_commit_lookup(commit->object.pool, &oid)) == NULL)
			return GIT_ENOTFOUND;

		// Inherit uninteresting flag
		if (commit->uninteresting)
			parent->uninteresting = 1;

		git_commit_list_push_back(&commit->parents, parent);
	}

	if (git_commit__parse_time(&commit->commit_time, buffer, buffer_end) < 0)
		return GIT_EOBJCORRUPTED;

	commit->parsed = 1;

	return 0;
}

int git_commit_list_push_back(git_commit_list *list, git_commit *commit)
{
	git_commit_node *node = NULL;

	node = git__malloc(sizeof(git_commit_list));

	if (node == NULL)
		return GIT_ENOMEM;

	node->commit = commit;
	node->next = NULL;
	node->prev = list->tail;

	if (list->tail == NULL) {
		list->head = list->tail = node;
	} else {
		list->tail->next = node;
		list->tail = node;
	}

	list->size++;
	return 0;
}

int git_commit_list_push_front(git_commit_list *list, git_commit *commit)
{
	git_commit_node *node = NULL;

	node = git__malloc(sizeof(git_commit_list));

	if (node == NULL)
		return GIT_ENOMEM;

	node->commit = commit;
	node->next = list->head;
	node->prev = NULL;

	if (list->head == NULL) {
		list->head = list->tail = node;
	} else {
		list->head->prev = node;
		list->head = node;
	}

	list->size++;
	return 0;
}


git_commit *git_commit_list_pop_back(git_commit_list *list)
{
	git_commit_node *node;
	git_commit *commit;

	if (list->tail == NULL)
		return NULL;

	node = list->tail;
	list->tail = list->tail->prev;
	if (list->tail == NULL)
		list->head = NULL;

	commit = node->commit;
	free(node);

	list->size--;

	return commit;
}

git_commit *git_commit_list_pop_front(git_commit_list *list)
{
	git_commit_node *node;
	git_commit *commit;

	if (list->head == NULL)
		return NULL;

	node = list->head;
	list->head = list->head->next;
	if (list->head == NULL)
		list->tail = NULL;

	commit = node->commit;
	free(node);

	list->size--;

	return commit;
}

void git_commit_list_clear(git_commit_list *list, int free_commits)
{
	git_commit_node *node, *next_node;

	node = list->head;
	while (node) {
		if (free_commits)
			free(node->commit);

		next_node = node->next;
		free(node);
		node = next_node;
	}

	list->head = list->tail = NULL;
	list->size = 0;
}

void git_commit_list_timesort(git_commit_list *list)
{
	git_commit_node *p, *q, *e;
	int in_size, p_size, q_size, merge_count, i;

	if (list->head == NULL)
		return;

	in_size = 1;

	do {
		p = list->head;
		list->tail = NULL;
		merge_count = 0;

		while (p != NULL) {
			merge_count++;
			q = p;
			p_size = 0;
			q_size = in_size;

			for (i = 0; i < in_size && q; ++i, q = q->next)
				p_size++;

			while (p_size > 0 || (q_size > 0 && q)) {

				if (p_size == 0)
					e = q, q = q->next, q_size--;

				else if (q_size == 0 || q == NULL ||
						p->commit->commit_time >= q->commit->commit_time)
					e = p, p = p->next, p_size--;

				else
					e = q, q = q->next, q_size--;

				if (list->tail != NULL)
					list->tail->next = e;
				else
					list->head = e;

				e->prev = list->tail;
				list->tail = e;
			}

			p = q;
		}

		list->tail->next = NULL;
		in_size *= 2;

	} while (merge_count > 1);
}

void git_commit_list_toposort(git_commit_list *list)
{
	git_commit *commit;
	git_commit_list topo;
	memset(&topo, 0x0, sizeof(git_commit_list));

	while ((commit = git_commit_list_pop_back(list)) != NULL) {
		git_commit_node *p;

		if (commit->in_degree > 0) {
			commit->topo_delay = 1;
			continue;
		}

		for (p = commit->parents.head; p != NULL; p = p->next) {
			p->commit->in_degree--;

			if (p->commit->in_degree == 0 && p->commit->topo_delay) {
				p->commit->topo_delay = 0;
				git_commit_list_push_back(list, p->commit);
			}
		}

		git_commit_list_push_back(&topo, commit);
	}

	list->head = topo.head;
	list->tail = topo.tail;
	list->size = topo.size;
}