/*
 * Copyright (c) 2018, 2019 Stefan Sperling <stsp@openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <sys/queue.h>
#include <sys/tree.h>
#include <sys/stat.h>

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sha1.h>
#include <endian.h>
#include <limits.h>

#include "got_error.h"
#include "got_object.h"

#include "got_lib_path.h"
#include "got_lib_fileindex.h"

struct got_fileindex {
	struct got_fileindex_tree entries;
	int nentries;
#define GOT_FILEIDX_MAX_ENTRIES INT_MAX
};

const struct got_error *
got_fileindex_entry_update(struct got_fileindex_entry *entry,
    const char *ondisk_path, uint8_t *blob_sha1, uint8_t *commit_sha1)
{
	struct stat sb;

	if (lstat(ondisk_path, &sb) != 0)
		return got_error_from_errno();

	entry->ctime_sec = sb.st_ctime;
	entry->ctime_nsec = sb.st_ctimensec;
	entry->mtime_sec = sb.st_mtime;
	entry->mtime_nsec = sb.st_mtimensec;
	entry->uid = sb.st_uid;
	entry->gid = sb.st_gid;
	entry->size = (sb.st_size & 0xffffffff);
	if (sb.st_mode & S_IFLNK)
		entry->mode = GOT_FILEIDX_MODE_SYMLINK;
	else
		entry->mode = GOT_FILEIDX_MODE_REGULAR_FILE;
	entry->mode |= ((sb.st_mode & (S_IRWXU | S_IRWXG | S_IRWXO)) <<
	    GOT_FILEIDX_MODE_PERMS_SHIFT);
	memcpy(entry->blob_sha1, blob_sha1, SHA1_DIGEST_LENGTH);
	memcpy(entry->commit_sha1, commit_sha1, SHA1_DIGEST_LENGTH);

	return NULL;
}

const struct got_error *
got_fileindex_entry_alloc(struct got_fileindex_entry **entry,
    const char *ondisk_path, const char *relpath, uint8_t *blob_sha1,
    uint8_t *commit_sha1)
{
	size_t len;

	*entry = calloc(1, sizeof(**entry));
	if (*entry == NULL)
		return got_error_from_errno();

	(*entry)->path = strdup(relpath);
	if ((*entry)->path == NULL) {
		const struct got_error *err = got_error_from_errno();
		free(*entry);
		*entry = NULL;
		return err;
	}

	len = strlen(relpath);
	if (len > GOT_FILEIDX_F_PATH_LEN)
		len = GOT_FILEIDX_F_PATH_LEN;
	(*entry)->flags |= len;

	return got_fileindex_entry_update(*entry, ondisk_path, blob_sha1,
	    commit_sha1);
}

void
got_fileindex_entry_free(struct got_fileindex_entry *entry)
{
	free(entry->path);
	free(entry);
}

static const struct got_error *
add_entry(struct got_fileindex *fileindex, struct got_fileindex_entry *entry)
{
	if (fileindex->nentries >= GOT_FILEIDX_MAX_ENTRIES)
		return got_error(GOT_ERR_NO_SPACE);

	RB_INSERT(got_fileindex_tree, &fileindex->entries, entry);
	fileindex->nentries++;
	return NULL;
}

const struct got_error *
got_fileindex_entry_add(struct got_fileindex *fileindex,
    struct got_fileindex_entry *entry)
{
	/* Flag this entry until it gets written out to disk. */
	entry->flags |= GOT_FILEIDX_F_INTENT_TO_ADD;

	return add_entry(fileindex, entry);
}

void
got_fileindex_entry_remove(struct got_fileindex *fileindex,
    struct got_fileindex_entry *entry)
{
	RB_REMOVE(got_fileindex_tree, &fileindex->entries, entry);
	fileindex->nentries--;
}

struct got_fileindex_entry *
got_fileindex_entry_get(struct got_fileindex *fileindex, const char *path)
{
	struct got_fileindex_entry key;
	memset(&key, 0, sizeof(key));
	key.path = (char *)path;
	return RB_FIND(got_fileindex_tree, &fileindex->entries, &key);
}

const struct got_error *
got_fileindex_for_each_entry_safe(struct got_fileindex *fileindex,
    got_fileindex_cb cb, void *cb_arg)
{
	const struct got_error *err;
	struct got_fileindex_entry *entry, *tmp;

	RB_FOREACH_SAFE(entry, got_fileindex_tree, &fileindex->entries, tmp) {
		err = (*cb)(cb_arg, entry);
		if (err)
			return err;
	}
	return NULL;
}

struct got_fileindex *
got_fileindex_alloc(void)
{
	struct got_fileindex *fileindex;

	fileindex = calloc(1, sizeof(*fileindex));
	if (fileindex == NULL)
		return NULL;

	RB_INIT(&fileindex->entries);
	return fileindex;
}

void
got_fileindex_free(struct got_fileindex *fileindex)
{
	struct got_fileindex_entry *entry;

	while ((entry = RB_MIN(got_fileindex_tree, &fileindex->entries))) {
		RB_REMOVE(got_fileindex_tree, &fileindex->entries, entry);
		got_fileindex_entry_free(entry);
	}
	free(fileindex);
}

static const struct got_error *
write_fileindex_val64(SHA1_CTX *ctx, uint64_t val, FILE *outfile)
{
	size_t n;

	val = htobe64(val);
	SHA1Update(ctx, (uint8_t *)&val, sizeof(val));
	n = fwrite(&val, 1, sizeof(val), outfile);
	if (n != sizeof(val))
		return got_ferror(outfile, GOT_ERR_IO);
	return NULL;
}

static const struct got_error *
write_fileindex_val32(SHA1_CTX *ctx, uint32_t val, FILE *outfile)
{
	size_t n;

	val = htobe32(val);
	SHA1Update(ctx, (uint8_t *)&val, sizeof(val));
	n = fwrite(&val, 1, sizeof(val), outfile);
	if (n != sizeof(val))
		return got_ferror(outfile, GOT_ERR_IO);
	return NULL;
}

static const struct got_error *
write_fileindex_val16(SHA1_CTX *ctx, uint16_t val, FILE *outfile)
{
	size_t n;

	val = htobe16(val);
	SHA1Update(ctx, (uint8_t *)&val, sizeof(val));
	n = fwrite(&val, 1, sizeof(val), outfile);
	if (n != sizeof(val))
		return got_ferror(outfile, GOT_ERR_IO);
	return NULL;
}

static const struct got_error *
write_fileindex_path(SHA1_CTX *ctx, const char *path, FILE *outfile)
{
	size_t n, len, pad = 0;
	static const uint8_t zero[8] = { 0 };

	len = strlen(path);
	while ((len + pad) % 8 != 0)
		pad++;
	if (pad == 0)
		pad = 8; /* NUL-terminate */

	SHA1Update(ctx, path, len);
	n = fwrite(path, 1, len, outfile);
	if (n != len)
		return got_ferror(outfile, GOT_ERR_IO);
	SHA1Update(ctx, zero, pad);
	n = fwrite(zero, 1, pad, outfile);
	if (n != pad)
		return got_ferror(outfile, GOT_ERR_IO);
	return NULL;
}

static const struct got_error *
write_fileindex_entry(SHA1_CTX *ctx, struct got_fileindex_entry *entry,
    FILE *outfile)
{
	const struct got_error *err;
	size_t n;

	err = write_fileindex_val64(ctx, entry->ctime_sec, outfile);
	if (err)
		return err;
	err = write_fileindex_val64(ctx, entry->ctime_nsec, outfile);
	if (err)
		return err;
	err = write_fileindex_val64(ctx, entry->mtime_sec, outfile);
	if (err)
		return err;
	err = write_fileindex_val64(ctx, entry->mtime_nsec, outfile);
	if (err)
		return err;

	err = write_fileindex_val32(ctx, entry->uid, outfile);
	if (err)
		return err;
	err = write_fileindex_val32(ctx, entry->gid, outfile);
	if (err)
		return err;
	err = write_fileindex_val32(ctx, entry->size, outfile);
	if (err)
		return err;

	err = write_fileindex_val16(ctx, entry->mode, outfile);
	if (err)
		return err;

	SHA1Update(ctx, entry->blob_sha1, SHA1_DIGEST_LENGTH);
	n = fwrite(entry->blob_sha1, 1, SHA1_DIGEST_LENGTH, outfile);
	if (n != SHA1_DIGEST_LENGTH)
		return got_ferror(outfile, GOT_ERR_IO);

	SHA1Update(ctx, entry->commit_sha1, SHA1_DIGEST_LENGTH);
	n = fwrite(entry->commit_sha1, 1, SHA1_DIGEST_LENGTH, outfile);
	if (n != SHA1_DIGEST_LENGTH)
		return got_ferror(outfile, GOT_ERR_IO);

	err = write_fileindex_val32(ctx, entry->flags, outfile);
	if (err)
		return err;

	err = write_fileindex_path(ctx, entry->path, outfile);
	return err;
}

const struct got_error *
got_fileindex_write(struct got_fileindex *fileindex, FILE *outfile)
{
	const struct got_error *err = NULL;
	struct got_fileindex_hdr hdr;
	SHA1_CTX ctx;
	uint8_t sha1[SHA1_DIGEST_LENGTH];
	size_t n;
	struct got_fileindex_entry *entry;

	SHA1Init(&ctx);

	hdr.signature = htobe32(GOT_FILE_INDEX_SIGNATURE);
	hdr.version = htobe32(GOT_FILE_INDEX_VERSION);
	hdr.nentries = htobe32(fileindex->nentries);

	SHA1Update(&ctx, (uint8_t *)&hdr.signature, sizeof(hdr.signature));
	SHA1Update(&ctx, (uint8_t *)&hdr.version, sizeof(hdr.version));
	SHA1Update(&ctx, (uint8_t *)&hdr.nentries, sizeof(hdr.nentries));
	n = fwrite(&hdr.signature, 1, sizeof(hdr.signature), outfile);
	if (n != sizeof(hdr.signature))
		return got_ferror(outfile, GOT_ERR_IO);
	n = fwrite(&hdr.version, 1, sizeof(hdr.version), outfile);
	if (n != sizeof(hdr.version))
		return got_ferror(outfile, GOT_ERR_IO);
	n = fwrite(&hdr.nentries, 1, sizeof(hdr.nentries), outfile);
	if (n != sizeof(hdr.nentries))
		return got_ferror(outfile, GOT_ERR_IO);

	RB_FOREACH(entry, got_fileindex_tree, &fileindex->entries) {
		entry->flags &= ~GOT_FILEIDX_F_INTENT_TO_ADD;
		err = write_fileindex_entry(&ctx, entry, outfile);
		if (err)
			return err;
	}

	SHA1Final(sha1, &ctx);
	n = fwrite(sha1, 1, sizeof(sha1), outfile);
	if (n != sizeof(sha1))
		return got_ferror(outfile, GOT_ERR_IO);

	if (fflush(outfile) != 0)
		return got_error_from_errno();

	return NULL;
}

static const struct got_error *
read_fileindex_val64(uint64_t *val, SHA1_CTX *ctx, FILE *infile)
{
	size_t n;

	n = fread(val, 1, sizeof(*val), infile);
	if (n != sizeof(*val))
		return got_ferror(infile, GOT_ERR_FILEIDX_BAD);
	SHA1Update(ctx, (uint8_t *)val, sizeof(*val));
	*val = be64toh(*val);
	return NULL;
}

static const struct got_error *
read_fileindex_val32(uint32_t *val, SHA1_CTX *ctx, FILE *infile)
{
	size_t n;

	n = fread(val, 1, sizeof(*val), infile);
	if (n != sizeof(*val))
		return got_ferror(infile, GOT_ERR_FILEIDX_BAD);
	SHA1Update(ctx, (uint8_t *)val, sizeof(*val));
	*val = be32toh(*val);
	return NULL;
}

static const struct got_error *
read_fileindex_val16(uint16_t *val, SHA1_CTX *ctx, FILE *infile)
{
	size_t n;

	n = fread(val, 1, sizeof(*val), infile);
	if (n != sizeof(*val))
		return got_ferror(infile, GOT_ERR_FILEIDX_BAD);
	SHA1Update(ctx, (uint8_t *)val, sizeof(*val));
	*val = be16toh(*val);
	return NULL;
}

static const struct got_error *
read_fileindex_path(char **path, SHA1_CTX *ctx, FILE *infile)
{
	const struct got_error *err = NULL;
	uint8_t buf[8];
	size_t n, len = 0, totlen = sizeof(buf);

	*path = malloc(totlen);
	if (*path == NULL)
		return got_error_from_errno();

	do {
		n = fread(buf, 1, sizeof(buf), infile);
		if (n != sizeof(buf))
			return got_ferror(infile, GOT_ERR_FILEIDX_BAD);
		if (len + sizeof(buf) > totlen) {
			char *p = reallocarray(*path, totlen + sizeof(buf), 1);
			if (p == NULL) {
				err = got_error_from_errno();
				break;
			}
			totlen += sizeof(buf);
			*path = p;
		}
		SHA1Update(ctx, buf, sizeof(buf));
		memcpy(*path + len, buf, sizeof(buf));
		len += sizeof(buf);
	} while (memchr(buf, '\0', sizeof(buf)) == NULL);

	if (err) {
		free(*path);
		*path = NULL;
	}
	return err;
}

static const struct got_error *
read_fileindex_entry(struct got_fileindex_entry **entryp, SHA1_CTX *ctx,
    FILE *infile)
{
	const struct got_error *err;
	struct got_fileindex_entry *entry;
	size_t n;

	*entryp = NULL;

	entry = calloc(1, sizeof(*entry));
	if (entry == NULL)
		return got_error_from_errno();

	err = read_fileindex_val64(&entry->ctime_sec, ctx, infile);
	if (err)
		goto done;
	err = read_fileindex_val64(&entry->ctime_nsec, ctx, infile);
	if (err)
		goto done;
	err = read_fileindex_val64(&entry->mtime_sec, ctx, infile);
	if (err)
		goto done;
	err = read_fileindex_val64(&entry->mtime_nsec, ctx, infile);
	if (err)
		goto done;

	err = read_fileindex_val32(&entry->uid, ctx, infile);
	if (err)
		goto done;
	err = read_fileindex_val32(&entry->gid, ctx, infile);
	if (err)
		goto done;
	err = read_fileindex_val32(&entry->size, ctx, infile);
	if (err)
		goto done;

	err = read_fileindex_val16(&entry->mode, ctx, infile);
	if (err)
		goto done;

	n = fread(entry->blob_sha1, 1, SHA1_DIGEST_LENGTH, infile);
	if (n != SHA1_DIGEST_LENGTH) {
		err = got_ferror(infile, GOT_ERR_FILEIDX_BAD);
		goto done;
	}
	SHA1Update(ctx, entry->blob_sha1, SHA1_DIGEST_LENGTH);

	n = fread(entry->commit_sha1, 1, SHA1_DIGEST_LENGTH, infile);
	if (n != SHA1_DIGEST_LENGTH) {
		err = got_ferror(infile, GOT_ERR_FILEIDX_BAD);
		goto done;
	}
	SHA1Update(ctx, entry->commit_sha1, SHA1_DIGEST_LENGTH);

	err = read_fileindex_val32(&entry->flags, ctx, infile);
	if (err)
		goto done;

	err = read_fileindex_path(&entry->path, ctx, infile);
done:
	if (err)
		free(entry);
	else
		*entryp = entry;
	return err;
}

const struct got_error *
got_fileindex_read(struct got_fileindex *fileindex, FILE *infile)
{
	const struct got_error *err = NULL;
	struct got_fileindex_hdr hdr;
	SHA1_CTX ctx;
	struct got_fileindex_entry *entry;
	uint8_t sha1_expected[SHA1_DIGEST_LENGTH];
	uint8_t sha1[SHA1_DIGEST_LENGTH];
	size_t n;
	int i;

	SHA1Init(&ctx);

	n = fread(&hdr.signature, 1, sizeof(hdr.signature), infile);
	if (n != sizeof(hdr.signature)) {
		if (n == 0) /* EOF */
			return NULL;
		return got_ferror(infile, GOT_ERR_FILEIDX_BAD);
	}
	n = fread(&hdr.version, 1, sizeof(hdr.version), infile);
	if (n != sizeof(hdr.version)) {
		if (n == 0) /* EOF */
			return NULL;
		return got_ferror(infile, GOT_ERR_FILEIDX_BAD);
	}
	n = fread(&hdr.nentries, 1, sizeof(hdr.nentries), infile);
	if (n != sizeof(hdr.nentries)) {
		if (n == 0) /* EOF */
			return NULL;
		return got_ferror(infile, GOT_ERR_FILEIDX_BAD);
	}

	SHA1Update(&ctx, (uint8_t *)&hdr.signature, sizeof(hdr.signature));
	SHA1Update(&ctx, (uint8_t *)&hdr.version, sizeof(hdr.version));
	SHA1Update(&ctx, (uint8_t *)&hdr.nentries, sizeof(hdr.nentries));

	hdr.signature = be32toh(hdr.signature);
	hdr.version = be32toh(hdr.version);
	hdr.nentries = be32toh(hdr.nentries);

	if (hdr.signature != GOT_FILE_INDEX_SIGNATURE)
		return got_error(GOT_ERR_FILEIDX_SIG);
	if (hdr.version != GOT_FILE_INDEX_VERSION)
		return got_error(GOT_ERR_FILEIDX_VER);

	for (i = 0; i < hdr.nentries; i++) {
		err = read_fileindex_entry(&entry, &ctx, infile);
		if (err)
			return err;
		err = add_entry(fileindex, entry);
		if (err)
			return err;
	}

	n = fread(sha1_expected, 1, sizeof(sha1_expected), infile);
	if (n != sizeof(sha1_expected))
		return got_ferror(infile, GOT_ERR_FILEIDX_BAD);
	SHA1Final(sha1, &ctx);
	if (memcmp(sha1, sha1_expected, SHA1_DIGEST_LENGTH) != 0)
		return got_error(GOT_ERR_FILEIDX_CSUM);

	return NULL;
}

static int
in_same_subdir(struct got_fileindex_entry *ie, const char *parent_path,
    struct got_tree_entry *te)
{
	size_t parent_len = strlen(parent_path);
	char *ie_name;

	if (!got_path_is_child(ie->path, parent_path, parent_len))
		return 0;

	ie_name = ie->path + parent_len;
	while (ie_name[0] == '/')
		ie_name++;

	return strchr(ie_name, '/') == NULL;
}

/*
 * Decide whether ie or te are equivalent, and if they aren't,
 * then decide which should be processed first.
 */
static int
cmp_entries(struct got_fileindex_entry *ie, const char *parent_path,
    struct got_tree_entry *te)
{
	size_t parent_len = strlen(parent_path);
	int cmp;

	if (!in_same_subdir(ie, parent_path, te)) {
		cmp = strncmp(ie->path, parent_path, parent_len);
		if (cmp == 0) {
			char *ie_name = ie->path + parent_len;
			while (ie_name[0] == '/')
				ie_name++;
			cmp = strcmp(ie_name, te->name);
		}
	} else {
		char *ie_name = ie->path + parent_len;
		while (ie_name[0] == '/')
			ie_name++;
		cmp = strcmp(ie_name, te->name);
	}
	return cmp;

}

static const struct got_error *
diff_fileindex_tree(struct got_fileindex *, struct got_fileindex_entry **,
    struct got_tree_object *, const char *, struct got_repository *,
    struct got_fileindex_diff_cb *, void *);

struct got_fileindex_entry *
walk_fileindex(struct got_fileindex *fileindex, struct got_fileindex_entry *ie)
{
	struct got_fileindex_entry *next;

	next = RB_NEXT(got_fileindex_tree, &fileindex->entries, ie);

	/* Skip entries which were newly added by diff callbacks. */
	while (next && (next->flags & GOT_FILEIDX_F_INTENT_TO_ADD))
		next = RB_NEXT(got_fileindex_tree, &fileindex->entries, next);

	return next;
}

static const struct got_error *
walk_tree(struct got_tree_entry **next, struct got_fileindex *fileindex,
    struct got_fileindex_entry **ie, struct got_tree_entry *te,
    const char *path, struct got_repository *repo,
    struct got_fileindex_diff_cb *cb, void *cb_arg)
{
	const struct got_error *err = NULL;

	if (S_ISDIR(te->mode)) {
		char *subpath;
		struct got_tree_object *subtree;

		if (asprintf(&subpath, "%s%s%s", path,
		    path[0] == '\0' ? "" : "/", te->name) == -1)
			return got_error_from_errno();

		err = got_object_open_as_tree(&subtree, repo, te->id);
		if (err) {
			free(subpath);
			return err;
		}

		err = diff_fileindex_tree(fileindex, ie, subtree,
		    subpath, repo, cb, cb_arg);
		free(subpath);
		got_object_tree_close(subtree);
		if (err)
			return err;
	}

	*next = SIMPLEQ_NEXT(te, entry);
	return NULL;
}

static const struct got_error *
diff_fileindex_tree(struct got_fileindex *fileindex,
    struct got_fileindex_entry **ie, struct got_tree_object *tree,
    const char *path, struct got_repository *repo,
    struct got_fileindex_diff_cb *cb, void *cb_arg)
{
	const struct got_error *err = NULL;
	struct got_tree_entry *te = NULL;
	size_t path_len = strlen(path);
	const struct got_tree_entries *entries;
	struct got_fileindex_entry *next;

	entries = got_object_tree_get_entries(tree);
	te = SIMPLEQ_FIRST(&entries->head);
	do {
		if (te && *ie) {
			int cmp = cmp_entries(*ie, path, te);
			if (cmp == 0) {
				err = cb->diff_old_new(cb_arg, *ie, te,
				    path);
				if (err)
					break;
				*ie = walk_fileindex(fileindex, *ie);
				err = walk_tree(&te, fileindex, ie, te,
				    path, repo, cb, cb_arg);
			} else if (cmp < 0 ) {
				next = walk_fileindex(fileindex, *ie);
				err = cb->diff_old(cb_arg, *ie, path);
				if (err)
					break;
				*ie = next;
			} else {
				err = cb->diff_new(cb_arg, te, path);
				if (err)
					break;
				err = walk_tree(&te, fileindex, ie, te,
				    path, repo, cb, cb_arg);
			}
			if (err)
				break;
		} else if (*ie) {
			next = walk_fileindex(fileindex, *ie);
			err = cb->diff_old(cb_arg, *ie, path);
			if (err)
				break;
			*ie = next;
		} else if (te) {
			err = cb->diff_new(cb_arg, te, path);
			if (err)
				break;
			err = walk_tree(&te, fileindex, ie, te, path, repo, cb,
			    cb_arg);
			if (err)
				break;
		}
	} while ((*ie && got_path_is_child((*ie)->path, path, path_len)) || te);

	return err;
}

const struct got_error *
got_fileindex_diff_tree(struct got_fileindex *fileindex,
    struct got_tree_object *tree, struct got_repository *repo,
    struct got_fileindex_diff_cb *cb, void *cb_arg)
{
	struct got_fileindex_entry *min;
	min = RB_MIN(got_fileindex_tree, &fileindex->entries);
	return diff_fileindex_tree(fileindex, &min, tree, "", repo, cb, cb_arg);
}

RB_GENERATE(got_fileindex_tree, got_fileindex_entry, entry, got_fileindex_cmp);