#include <u.h>
#include <libc.h>

#include "mdb.h"
#include "impl.h"

enum {
	MAXPOOLPAGE	= 16,
};

int
mdb_initpool(MDB *db)
{
	int i;
	Page *p;

	for(i = 0; i < MAXPOOLPAGE; i++){
		p = malloc(sizeof(*p));
		if(p == nil)
			return -1;

		mdb_putpage(db, p);
	}

	return 0;
}

/* cannot fail */
Page*
mdb_getpage(MDB *db)
{
	Page *p;

	if(db->pool == nil){
		p = mdb_calloc(db, 1, sizeof(*p));
	} else {
		p = db->pool;
		db->pool = p->next;
		db->npool--;
	}

	assert(p != nil);

	setmalloctag(p, getcallerpc(&db));
	memset(p, 0, sizeof(*p));
	p->id = NOPAGE;

	return p;
}

void
mdb_putpage(MDB *db, Page *p)
{
	if(db->npool == MAXPOOLPAGE){
		free(p);
		return;
	}

	p->next = db->pool;
	db->pool = p;
	db->npool++;
}

static Page*
mdb_getcache(MDB *db, u32int id)
{
	u32int idx;
	Page *p;

if(0){
fprint(2, "getcache: dump\n");
int i;
for(i = 0; i < nelem(db->cache); i++){
	p = db->cache[i];
	if(p != nil)
		fprint(2, "buq %d\n", i);
	for(; p != nil; p = p->next){
		fprint(2, "page=%ud type=%ud\n", p->id, p->type);
	}
}
}

	idx = id % nelem(db->cache);
	for(p = db->cache[idx]; p != nil; p = p->next){
		if(p->id == id)
			return p;
	}

	return nil;
}

/* cannot fail */
static Page*
mdb_pagedup(MDB *db, Page *p)
{
	Page *newp;

	newp = mdb_getpage(db);
	setmalloctag(newp, getcallerpc(&db));
	memmove(newp, p, sizeof(*p));

	return newp;
}

/* cannot fail */
Page*
mdb_readpage(MDB *db, u32int id, u32int type)
{
	long rv;
	u32int idx;
	uchar buf[BLOCK];
	Page *p;

	//fprint(2, "mdb_readpage: page=%ud expect type=%ud\n", id, type);

	p = mdb_getcache(db, id);
	if(p != nil)
		return mdb_pagedup(db, p);

	p = mdb_getpage(db);

	do {
		rv = pread(db->fd, buf, sizeof(buf), sizeof(buf)*id);
	} while(rv < 0 && mdb_error_io(db) == 0);

	if(rv < 0)
		abort();

	if(rv != sizeof(buf))
		abort();

	p->id = id;

	mdb_unpack(db, p, buf);

	if(type != T_ANY && p->type != type)
		mdb_error_corrupt(db);

	idx = id % nelem(db->cache);
	p->next = db->cache[idx];
	db->cache[idx] = p;
	db->ncache++;

	return mdb_pagedup(db, p);
}

/* TODO: dont blow the cache on sync */
static void
mdb_writepage_uncached(MDB *db, Page *p)
{
	long rv;
	int sz;
	uchar buf[BLOCK];

	memset(buf, 0, sizeof(buf));

	sz = mdb_pack(db, p, buf);

	assert(sz <= sizeof(buf));

	fmtinstall('H', encodefmt);
	//fprint(2, "mdb_writepage_uncached: write block %ud %d bytes\n%.*H\n", p->id, sz, sz, buf);

	do {
		rv = pwrite(db->fd, buf, sizeof(buf), sizeof(buf)*p->id);
	} while(rv < 0 && mdb_error_io(db) == 0);

	if(rv < 0)
		abort();

	mdb_putpage(db, p);
}

void
mdb_writepage(MDB *db, Page *p)
{
	u32int idx;
	Page **pp;

if(0){
fprint(2, "===== writepage: before\n");
Page *ppp;
int i;
for(i = 0; i < nelem(db->cache); i++){
	ppp = db->cache[i];
	if(ppp != nil)
		fprint(2, "buq %d\n", i);
	for(; ppp != nil; ppp = ppp->next){
		fprint(2, "page=%ud type=%ud\n", ppp->id, ppp->type);
	}
}
}

	assert(p->type > 0 && p->type < T_MAX);
	assert(p->id < db->size);

	idx = p->id % nelem(db->cache);
//fprint(2, "mdb_writepage: pid=%ud type=%ud idx=%ud\n", p->id, p->type, idx);
	for(pp = &db->cache[idx]; *pp != nil; pp = &(*pp)->next){
		if((*pp)->id == p->id){
//fprint(2, "mdb_writepage: swap %ud -> %ud\n", (*pp)->type, p->type);
//fprint(2, "page id=%ud type=%ud next=%p\n", p->id, p->type, p->next);

			/* XXX: if pages are the same do nothing */
			if(*pp == p)
				return;

			p->next = (*pp)->next;
			mdb_putpage(db, *pp);
			*pp = p;
//			goto out;
			return;
		}
	}

	p->next = db->cache[idx];
	db->cache[idx] = p;
	db->ncache++;

out:
if(0){
fprint(2, "===== writepage: after\n");
Page *ppp;
int i;
for(i = 0; i < nelem(db->cache); i++){
	ppp = db->cache[i];
	if(ppp != nil)
		fprint(2, "buq %d\n", i);
	for(; ppp != nil; ppp = ppp->next){
		fprint(2, "page=%ud type=%ud\n", ppp->id, ppp->type);
	}
}
}
}

int
mdb_sync(MDB *db)
{
	int i;
	Page *p, *next;

	fprint(2, "mdb_sync: begin %d blocks. ", db->ncache);

	for(i = 0; i < nelem(db->cache); i++){
		for(p = db->cache[i]; p != nil; p = next){
			next = p->next;
			fprint(2, "%ud.. ", p->id);
			mdb_writepage_uncached(db, p);
		}

		db->cache[i] = nil;
	}

	db->ncache = 0;

	fprint(2, "ok.\n");

	return 0;
}