/* $Id$ */
#include "bbs.h"

/**
 * 關於本檔案的細節，請見 docs/brc.txt。
 * v3: add last modified time for comment system. double max size.
 *     original time_t as 'create'.
 */

#ifndef BRC_MAXNUM
#define BRC_STRLEN      15	/* Length of board name, for old brc */
#define BRC_MAXSIZE     49152   /* Effective size of brc rc file, 8192 * 3 * 2 */
#define BRC_MAXNUM      80      /* Upper bound of brc_num, size of brc_list  */
#endif

#define BRC_BLOCKSIZE   1024

#if MAX_BOARD > 65535 || BRC_MAXSIZE > 65535
#error Max number of boards or BRC_MAXSIZE cannot fit in unsigned short, \
please rewrite brc.c
#endif

typedef unsigned short brcbid_t;
typedef unsigned short brcnbrd_t;

typedef struct {
    time4_t create;
    time4_t modified;
} brc_rec;

/* old brc rc file form:
 * board_name     15 bytes
 * brc_num         1 byte, binary integer
 * brc_list       brc_num * sizeof(brc_rec) bytes  */

static char brc_initialized = 0;
static time4_t brc_expire_time;
 /* Will be set to the time one year before login. All the files created
  * before then will be recognized read. */

static int     brc_changed = 0;	/**< brc_list/brc_num changed */
/* The below two will be filled by read_brc_buf() and brc_update() */
static char   *brc_buf = NULL;
static int     brc_size;
static int     brc_alloc;

// read records for currbid
static int             brc_currbid;
static int             brc_num;
static brc_rec         brc_list[BRC_MAXNUM];

static char * const fn_brc2= ".brc2";
static char * const fn_brc = ".brc3";

/**
 * find read records of bid in given buffer region
 *
 * @param[in]	begin
 * @param[in]	endp
 * @param	bid
 * @param[out]	num	number of records, which could be written for \a bid
 * 			= brc_num		if found
 * 			= 0 or dangling size	if not found
 * 					
 * @return	address of record. \a begin <= addr < \a endp.
 * 		0	if not found
 */
/* Returns the address of the record strictly between begin and endp with
 * bid equal to the parameter. Returns 0 if not found.
 * brcnbrd_t *num is an output parameter which will filled with brc_num
 * if the record is found. If not found the record, *num will be the number
 * of dangling bytes. */
static char *
brc_findrecord_in(char *begin, char *endp, brcbid_t bid, brcnbrd_t *num)
{
    char     *tmpp, *ptr = begin;
    brcbid_t tbid;
    while (ptr + sizeof(brcbid_t) + sizeof(brcnbrd_t) < endp) {
	/* for each available records */
	tmpp = ptr;
	tbid = *(brcbid_t*)tmpp;
	tmpp += sizeof(brcbid_t);
	*num = *(brcnbrd_t*)tmpp;
	tmpp += sizeof(brcnbrd_t) + *num * sizeof(brc_rec); /* end of record */

	if ( tmpp > endp ){
	    /* dangling, ignore the trailing data */
	    *num = (brcnbrd_t)(endp - ptr); /* for brc_insert_record() */
	    return 0;
	}
	if ( tbid == bid )
	    return ptr;
	ptr = tmpp;
    }

    *num = 0;
    return 0;
}

static brc_rec *
brc_find_record(int bid, int *num)
{
    char *p;
    brcnbrd_t tnum;
    p = brc_findrecord_in(brc_buf, brc_buf + brc_size, bid, &tnum);
    *num = tnum;
    if (p)
	return (brc_rec*)(p + sizeof(brcbid_t) + sizeof(brcnbrd_t));
    *num = 0;
    return 0;
}

static char *
brc_putrecord(char *ptr, char *endp, brcbid_t bid,
	      brcnbrd_t num, const brc_rec *list)
{
    char * tmp;
    if (num > 0 && list[0].create > brc_expire_time &&
	    ptr + sizeof(brcbid_t) + sizeof(brcnbrd_t) < endp) {
	if (num > BRC_MAXNUM)
	    num = BRC_MAXNUM;

	if (num == 0) return ptr;

	*(brcbid_t*)ptr  = bid;         /* write in bid */
	ptr += sizeof(brcbid_t);
	*(brcnbrd_t*)ptr = num;         /* write in brc_num */
	ptr += sizeof(brcnbrd_t);
	tmp = ptr + num * sizeof(brc_rec);
	if (tmp <= endp)
	    memcpy(ptr, list, num * sizeof(brc_rec)); /* write in brc_list */
	ptr = tmp;
    }
    return ptr;
}

static inline int
brc_enlarge_buf(void)
{
    char *buffer;
    if (brc_alloc >= BRC_MAXSIZE)
	return 0;

#ifdef CRITICAL_MEMORY
#define THE_MALLOC(X) MALLOC(X)
#define THE_FREE(X) FREE(X)
#else
#define THE_MALLOC(X) alloca(X)
#define THE_FREE(X) (void)(X)
    /* alloca get memory from stack and automatically freed when
     * function returns. */
#endif

    buffer = (char*)THE_MALLOC(brc_alloc);
    assert(buffer);

    memcpy(buffer, brc_buf, brc_alloc);
    free(brc_buf);
    brc_alloc += BRC_BLOCKSIZE;
    brc_buf = (char*)malloc(brc_alloc);
    assert(brc_buf);
    memcpy(brc_buf, buffer, brc_alloc - BRC_BLOCKSIZE);

#ifdef DEBUG
    vmsgf("brc enlarged to %d bytes", brc_alloc);
#endif

    THE_FREE(buffer);
    return 1;

#undef THE_MALLOC
#undef THE_FREE
}

static inline void
brc_get_buf(int size){
    if (!size)
	brc_alloc = BRC_BLOCKSIZE;
    else
	brc_alloc = (size + BRC_BLOCKSIZE - 1) / BRC_BLOCKSIZE * BRC_BLOCKSIZE;
    if (brc_alloc > BRC_MAXSIZE)
	brc_alloc = BRC_MAXSIZE;
    brc_buf = (char*)malloc(brc_alloc);
    assert(brc_buf);
}

static inline void
brc_insert_record(brcbid_t bid, brcnbrd_t num, const brc_rec* list)
{
    char           *ptr;
    int             new_size, end_size;
    brcnbrd_t       tnum;

    ptr = brc_findrecord_in(brc_buf, brc_buf + brc_size, bid, &tnum);

    while (num > 0 && list[num - 1].create < brc_expire_time)
	num--; /* don't write the times before brc_expire_time */

    if (!ptr) {
	brc_size -= (int)tnum;

	/* put on the beginning */
	if (num){
	    new_size = sizeof(brcbid_t) + sizeof(brcnbrd_t)
		+ num * sizeof(brc_rec);
	    brc_size += new_size;
	    if (brc_size > brc_alloc && !brc_enlarge_buf())
		brc_size = BRC_MAXSIZE;
	    if (brc_size > new_size)
		memmove(brc_buf + new_size, brc_buf, brc_size - new_size);
	    brc_putrecord(brc_buf, brc_buf + new_size, bid, num, list);
	}
    } else {
	/* ptr points to the old current brc list.
	 * tmpp is the end of it (exclusive).       */
	int len = sizeof(brcbid_t) + sizeof(brcnbrd_t) + tnum * sizeof(brc_rec);
	char *tmpp = ptr + len;
	end_size = brc_buf + brc_size - tmpp;
	if (num) {
	    int sindex = ptr - brc_buf;
	    new_size = (sizeof(brcbid_t) + sizeof(brcnbrd_t)
			+ num * sizeof(brc_rec));
	    brc_size += new_size - len;
	    if (brc_size > brc_alloc) {
		if (brc_enlarge_buf()) {
		    ptr = brc_buf + sindex;
		    tmpp = ptr + len;
		} else {
		    end_size -= brc_size - BRC_MAXSIZE;
		    brc_size = BRC_MAXSIZE;
		}
	    }
	    if (end_size > 0 && ptr + new_size != tmpp)
		memmove(ptr + new_size, tmpp, end_size);
	    brc_putrecord(ptr, brc_buf + brc_alloc, bid, num, list);
	} else { /* deleting record */
	    memmove(ptr, tmpp, end_size);
	    brc_size -= len;
	}
    }

    brc_changed = 0;
}

/**
 * write \a brc_num and \a brc_list back to \a brc_buf.
 */
void
brc_update(){
    if (brc_currbid && brc_changed && cuser.userlevel && brc_num > 0) {
	brc_initialize();
	brc_insert_record(brc_currbid, brc_num, brc_list);
    }
}

static void 
read_brc2(void)
{
    char            brcfile[STRLEN];
    int             fd;
    size_t sz2 = 0, sz3 = 0;
    char	    *cvt = NULL, *cvthead = NULL;

    brcbid_t  bid;
    brcnbrd_t num;
    time4_t   create;
    brc_rec   rec;

    setuserfile(brcfile, fn_brc2);

    if ((fd = open(brcfile, O_RDONLY)) == -1)
	return;

    sz2 = dashs(brcfile);
    sz3 = sz2 * 2; // max double size

    cvthead = cvt = malloc (sz3);
    // now calculate real sz3

    while (read(fd, &bid, sizeof(bid)) > 0)
    {
	if (read(fd, &num, sizeof(num)) < 1)
	    break;

	*(brcbid_t*)cvt = bid; cvt += sizeof(brcbid_t);
	*(brcnbrd_t*)cvt = num;cvt += sizeof(brcnbrd_t);
	for (; num > 0; num--)
	{
	    read(fd, &create, sizeof(create));
	    rec.create = create;
	    rec.modified = create;
	    *(brc_rec*)cvt = rec; cvt += sizeof(brc_rec);
	}
    }
    close(fd);

    // now cvthead is ready for v3.
    brc_get_buf(sz3);
    brc_size = sz3;
    memcpy(brc_buf, cvthead, sz3);

    free(cvthead);
}

inline static void
read_brc_buf(void)
{
    char            brcfile[STRLEN];
    int             fd;
    struct stat     brcstat;

    if (brc_buf != NULL)
	return;

    brc_size = 0;
    setuserfile(brcfile, fn_brc);

    if ((fd = open(brcfile, O_RDONLY)) == -1)
    {
	read_brc2();
	return;
    }

    fstat(fd, &brcstat);
    brc_get_buf(brcstat.st_size);
    brc_size = read(fd, brc_buf, brc_alloc);
    close(fd);
}

/* release allocated memory
 *
 * Do not destory brc_currbid, brc_num, brc_list.
 */
void
brc_release()
{
    if (brc_buf) {
	free(brc_buf);
	brc_buf = NULL;
    }
    brc_changed = 0;
    brc_size = brc_alloc = 0;
}

void
brc_finalize(){
    char brcfile[STRLEN];
    char tmpfile[STRLEN];

    if(!brc_initialized)
	return;

    brc_update();
    setuserfile(brcfile, fn_brc);
    snprintf(tmpfile, sizeof(tmpfile), "%s.tmp.%x", brcfile, getpid());
    if (brc_buf != NULL) {
	int fd = open(tmpfile, O_WRONLY | O_CREAT | O_TRUNC, 0644);
	if (fd != -1) {
	    int ok=0;
	    if(write(fd, brc_buf, brc_size)==brc_size)
		ok=1;
	    close(fd);
	    if(ok)
		Rename(tmpfile, brcfile);
	    else
		unlink(tmpfile);
	}
    }

    brc_release();
    brc_initialized = 0;
}

int
brc_initialize(){
    if (brc_initialized)
	return 1;
    brc_initialized = 1;
    brc_expire_time = login_start_time - 365 * 86400;
    read_brc_buf();
    return 0;
}

/** 
 * get the read records for bid
 *
 * @param bid
 * @param[out] num	number of record for \a bid. 1 <= \a num <= \a BRC_MAXNUM
 * 			\a num = 1 if no records.
 * @param[out] list	the list of records, length \a num
 *
 * @return number of read record, 0 if no records
 */
static int
brc_read_record(int bid, int *num, brc_rec *list){
    char *ptr;
    brcnbrd_t tnum;
    ptr = brc_findrecord_in(brc_buf, brc_buf + brc_size, bid, &tnum);
    *num = tnum;
    if ( ptr ){
	assert(0 <= *num && *num <= BRC_MAXNUM);
	memcpy(list, ptr + sizeof(brcbid_t) + sizeof(brcnbrd_t),
	       *num * sizeof(brc_rec));
	return *num;
    }
    list[0].create = *num = 1;
    return 0;
}

/**
 * @return number of records in \a boardname
 */
int
brc_initial_board(const char *boardname)
{
    brc_initialize();

    if (strcmp(currboard, boardname) == 0) {
	assert(currbid == brc_currbid);
	return brc_num;
    }

    brc_update(); /* write back first */
    currbid = getbnum(boardname);
    if( currbid == 0 )
	currbid = getbnum(DEFAULT_BOARD);
    assert(0<=currbid-1 && currbid-1<MAX_BOARD);
    brc_currbid = currbid;
    currboard = bcache[currbid - 1].brdname;
    currbrdattr = bcache[currbid - 1].brdattr;

    return brc_read_record(brc_currbid, &brc_num, brc_list);
}

static void
brc_trunc(int bid, time4_t ftime){
    brc_rec r;

    r.create = ftime;
    r.modified = ftime;
    brc_insert_record(bid, 1, &r);
    if ( bid == brc_currbid ){
	brc_num = 1;
	brc_list[0] = r;
	brc_changed = 0;
    }
}

void
brc_toggle_all_read(int bid, int is_all_read)
{
    brc_initialize();
    if (is_all_read)
        brc_trunc(bid, now);
    else
        brc_trunc(bid, 1);
}

void
brc_addlist(const char *fname, time4_t modified)
{
    int             n, i;
    brc_rec         frec;

    assert(currbid == brc_currbid);
    if (!cuser.userlevel)
	return;
    brc_initialize();

    frec.create = atoi(&fname[2]);
    frec.modified = modified;

    if (frec.create <= brc_expire_time /* too old, don't do any thing  */
	 /* || fname[0] != 'M' || fname[1] != '.' */ ) {
	return;
    }
    if (brc_num <= 0) { /* uninitialized */
	brc_list[0] = frec;
	brc_num = 1;
	brc_changed = 1;
	return;
    }
    if ((brc_num == 1) && (frec.create < brc_list[0].create)) /* most when after 'v' */
	return;
    for (n = 0; n < brc_num; n++) { /* using linear search */
	if (frec.create == brc_list[n].create) {
	    if (brc_list[n].modified < modified)
	    {
		brc_list[n].modified = modified;
		brc_changed = 1;
	    }
	    return;
	} else if (frec.create > brc_list[n].create) {
	    if (brc_num < BRC_MAXNUM)
		brc_num++;
	    /* insert frec into brc_list */
	    for (i = brc_num - 1; --i >= n; brc_list[i + 1] = brc_list[i]);
	    brc_list[n] = frec;
	    brc_changed = 1;
	    return;
	}
    }
}

// return:
//   0 - read
//   1 - unread (by create)
//   2 - unread (by modified)
int
brc_unread_time(int bid, time4_t ftime, time4_t modified)
{
    int             i;
    int	bnum;
    const brc_rec *blist;

    brc_initialize();
    if (ftime <= brc_expire_time) /* too old */
	return 0;

    if (brc_currbid && bid == brc_currbid) {
	blist = brc_list;
	bnum = brc_num;
    } else {
	blist = brc_find_record(bid, &bnum);
    }

    if (bnum <= 0)
	return 1;

    for (i = 0; i < bnum; i++) { /* using linear search */
	if (ftime > blist[i].create)
	    return 1;
	else if (ftime == blist[i].create)
	{
	    time4_t brcm = blist[i].modified;
	    if (modified == 0 || brcm == 0)
		return 0;
	    // bad  case... seems like that someone is making -1.
	    if (modified == (time4_t)-1 || brcm == (time4_t)-1)
		return 0;
	    return modified > brcm ? 2 : 0;
	}
    }
    return 0;
}

int
brc_unread(int bid, const char *fname, time4_t modified)
{
    int             ftime;

    ftime = atoi(&fname[2]); /* this will get the time of the file created */

    return brc_unread_time(bid, ftime, modified);
}