/*
 * $Id: refresh.c,v 1.54.2.2 2001/07/12 19:41:22 wessels Exp $
 *
 * DEBUG: section 22    Refresh Calculation
 * AUTHOR: Harvest Derived
 *
 * SQUID Web Proxy Cache          http://www.squid-cache.org/
 * ----------------------------------------------------------
 *
 *  Squid is the result of efforts by numerous individuals from
 *  the Internet community; see the CONTRIBUTORS file for full
 *  details.   Many organizations have provided support for Squid's
 *  development; see the SPONSORS file for full details.  Squid is
 *  Copyrighted (C) 2001 by the Regents of the University of
 *  California; see the COPYRIGHT file for full details.  Squid
 *  incorporates software developed and/or copyrighted by other
 *  sources; see the CREDITS file for full details.
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *  
 *  This program 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; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA.
 *
 */

#ifndef USE_POSIX_REGEX
#define USE_POSIX_REGEX		/* put before includes; always use POSIX */
#endif

#include "squid.h"

typedef enum {
    rcHTTP,
    rcICP,
#if USE_HTCP
    rcHTCP,
#endif
#if USE_CACHE_DIGESTS
    rcCDigest,
#endif
    rcStore,
    rcCount
} refreshCountsEnum;

typedef struct {
    unsigned int expires:1;
    unsigned int min:1;
    unsigned int lmfactor:1;
    unsigned int max;
} stale_flags;

/*
 * This enumerated list assigns specific values, ala HTTP/FTP status
 * codes.  All Fresh codes are in the range 100-199 and all stale
 * codes are 200-299.  We might want to use these codes in logging,
 * so best to keep them consistent over time.
 */
enum {
    FRESH_REQUEST_MAX_STALE_ALL = 100,
    FRESH_REQUEST_MAX_STALE_VALUE,
    FRESH_EXPIRES,
    FRESH_LMFACTOR_RULE,
    FRESH_MIN_RULE,
    FRESH_OVERRIDE_EXPIRES,
    FRESH_OVERRIDE_LASTMOD,
    STALE_MUST_REVALIDATE = 200,
    STALE_RELOAD_INTO_IMS,
    STALE_FORCED_RELOAD,
    STALE_EXCEEDS_REQUEST_MAX_AGE_VALUE,
    STALE_EXPIRES,
    STALE_MAX_RULE,
    STALE_LMFACTOR_RULE,
    STALE_DEFAULT = 299
};

static struct RefreshCounts {
    const char *proto;
    int total;
    int status[STALE_DEFAULT + 1];
} refreshCounts[rcCount];

/*
 * Defaults:
 *      MIN     NONE
 *      PCT     20%
 *      MAX     3 days
 */
#define REFRESH_DEFAULT_MIN	(time_t)0
#define REFRESH_DEFAULT_PCT	0.20
#define REFRESH_DEFAULT_MAX	(time_t)259200

static const refresh_t *refreshLimits(const char *);
static const refresh_t *refreshUncompiledPattern(const char *);
static OBJH refreshStats;
static int refreshStaleness(const StoreEntry *, time_t, time_t, const refresh_t *, stale_flags *);

static refresh_t DefaultRefresh;

static const refresh_t *
refreshLimits(const char *url)
{
    const refresh_t *R;
    for (R = Config.Refresh; R; R = R->next) {
	if (!regexec(&(R->compiled_pattern), url, 0, 0, 0))
	    return R;
    }
    return NULL;
}

static const refresh_t *
refreshUncompiledPattern(const char *pat)
{
    const refresh_t *R;
    for (R = Config.Refresh; R; R = R->next) {
	if (0 == strcmp(R->pattern, pat))
	    return R;
    }
    return NULL;
}

/*
 * Calculate how stale the response is (or will be at the check_time).
 * Staleness calculation is based on the following: (1) response
 * expiration time, (2) age greater than configured maximum, (3)
 * last-modified factor, and (4) age less than configured minimum.
 *
 * If the response is fresh, return -1.  Otherwise return its
 * staleness.  NOTE return value of 0 means the response is stale.
 *
 * The 'stale_flags' structure is used to tell the calling function
 * _why_ this response is fresh or stale.  Its used, for example,
 * when the admin wants to override expiration and last-modified
 * times.
 */
static int
refreshStaleness(const StoreEntry * entry, time_t check_time, time_t age, const refresh_t * R, stale_flags * sf)
{
    /*
     * Check for an explicit expiration time.
     */
    if (entry->expires > -1) {
	sf->expires = 1;
	if (entry->expires > check_time) {
	    debug(22, 3) ("FRESH: expires %d >= check_time %d \n",
		(int) entry->expires, (int) check_time);
	    return -1;
	} else {
	    debug(22, 3) ("STALE: expires %d < check_time %d \n",
		(int) entry->expires, (int) check_time);
	    return (check_time - entry->expires);
	}
    }
    assert(age >= 0);
    /*
     * Use local heuristics to determine staleness.  Start with the
     * max age from the refresh_pattern rule.
     */
    if (age > R->max) {
	debug(22, 3) ("STALE: age %d > max %d \n", (int) age, (int) R->max);
	sf->max = 1;
	return (age - R->max);
    }
    /*
     * Try the last-modified factor algorithm.
     */
    if (entry->lastmod > -1 && entry->timestamp > entry->lastmod) {
	/*
	 * stale_age is the Age of the response when it became/becomes
	 * stale according to the last-modified factor algorithm.
	 */
	time_t stale_age = (entry->timestamp - entry->lastmod) * R->pct;
	sf->lmfactor = 1;
	if (age >= stale_age) {
	    debug(22, 3) ("STALE: age %d > stale_age %d\n",
		(int) age, (int) stale_age);
	    return (age - stale_age);
	} else {
	    debug(22, 3) ("FRESH: age %d <= stale_age %d\n",
		(int) age, (int) stale_age);
	    return -1;
	}
    }
    /*
     * If we are here, staleness is determined by the refresh_pattern
     * configured minimum age.
     */
    if (age <= R->min) {
	debug(22, 3) ("FRESH: age %d <= min %d\n", (int) age, (int) R->min);
	sf->min = 1;
	return -1;
    }
    debug(22, 3) ("STALE: age %d > min %d\n", (int) age, (int) R->min);
    return (age - R->min);
}

/*  return 1 if the entry must be revalidated within delta seconds
 *         0 otherwise
 *
 *  note: request maybe null (e.g. for cache digests build)
 */
static int
refreshCheck(const StoreEntry * entry, request_t * request, time_t delta)
{
    const refresh_t *R;
    const char *uri = NULL;
    time_t age = 0;
    time_t check_time = squid_curtime + delta;
    int staleness;
    stale_flags sf;
    if (entry->mem_obj)
	uri = entry->mem_obj->url;
    else if (request)
	uri = urlCanonical(request);

    debug(22, 3) ("refreshCheck: '%s'\n", uri ? uri : "<none>");

    if (check_time > entry->timestamp)
	age = check_time - entry->timestamp;
    R = uri ? refreshLimits(uri) : refreshUncompiledPattern(".");
    if (NULL == R)
	R = &DefaultRefresh;
    memset(&sf, '\0', sizeof(sf));
    staleness = refreshStaleness(entry, check_time, age, R, &sf);
    debug(22, 3) ("Staleness = %d\n", staleness);

    debug(22, 3) ("refreshCheck: Matched '%s %d %d%% %d'\n",
	R->pattern, (int) R->min, (int) (100.0 * R->pct), (int) R->max);
    debug(22, 3) ("refreshCheck: age = %d\n", (int) age);
    debug(22, 3) ("\tcheck_time:\t%s\n", mkrfc1123(check_time));
    debug(22, 3) ("\tentry->timestamp:\t%s\n", mkrfc1123(entry->timestamp));

    if (EBIT_TEST(entry->flags, ENTRY_REVALIDATE) && staleness > -1) {
	debug(22, 3) ("refreshCheck: YES: Must revalidate stale response\n");
	return STALE_MUST_REVALIDATE;
    }
    /* request-specific checks */
    if (request) {
	HttpHdrCc *cc = request->cache_control;
#if HTTP_VIOLATIONS
	if (!request->flags.nocache_hack) {
	    (void) 0;
	} else if (R->flags.ignore_reload) {
	    /* The clients no-cache header is ignored */
	    debug(22, 3) ("refreshCheck: MAYBE: ignore-reload\n");
	} else if (R->flags.reload_into_ims || Config.onoff.reload_into_ims) {
	    /* The clients no-cache header is changed into a IMS query */
	    debug(22, 3) ("refreshCheck: YES: reload-into-ims\n");
	    return STALE_RELOAD_INTO_IMS;
	} else {
	    /* The clients no-cache header is not overridden on this request */
	    debug(22, 3) ("refreshCheck: YES: client reload\n");
	    request->flags.nocache = 1;
	    return STALE_FORCED_RELOAD;
	}
#endif
	if (NULL != cc) {
	    if (cc->max_age > -1) {
		if (age > cc->max_age) {
		    debug(22, 3) ("refreshCheck: YES: age > client-max-age\n");
		    return STALE_EXCEEDS_REQUEST_MAX_AGE_VALUE;
		}
	    }
	    if (EBIT_TEST(cc->mask, CC_MAX_STALE) && staleness > -1) {
		if (cc->max_stale < 0) {
		    /* max-stale directive without a value */
		    debug(22, 3) ("refreshCheck: NO: max-stale wildcard\n");
		    return FRESH_REQUEST_MAX_STALE_ALL;
		} else if (staleness < cc->max_stale) {
		    debug(22, 3) ("refreshCheck: NO: staleness < max-stale\n");
		    return FRESH_REQUEST_MAX_STALE_VALUE;
		}
	    }
	}
    }
    if (-1 == staleness) {
	if (sf.expires)
	    return FRESH_EXPIRES;
	assert(!sf.max);
	if (sf.lmfactor)
	    return FRESH_LMFACTOR_RULE;
	assert(sf.min);
	return FRESH_MIN_RULE;
    }
    /*
     * At this point the response is stale, unless one of
     * the override options kicks in.
     */
    if (sf.expires) {
#if HTTP_VIOLATIONS
	if (R->flags.override_expire && age < R->min) {
	    debug(22, 3) ("refreshCheck: NO: age < min && override-expire\n");
	    return FRESH_OVERRIDE_EXPIRES;
	}
#endif
	return STALE_EXPIRES;
    }
    if (sf.max)
	return STALE_MAX_RULE;
    if (sf.lmfactor) {
#if HTTP_VIOLATIONS
	if (R->flags.override_lastmod && age < R->min) {
	    debug(22, 3) ("refreshCheck: NO: age < min && override-lastmod\n");
	    return FRESH_OVERRIDE_LASTMOD;
	}
#endif
	return STALE_LMFACTOR_RULE;
    }
    return STALE_DEFAULT;
}

int
refreshIsCachable(const StoreEntry * entry)
{
    /*
     * Don't look at the request to avoid no-cache and other nuisances.
     * the object should have a mem_obj so the URL will be found there.
     * 60 seconds delta, to avoid objects which expire almost
     * immediately, and which can't be refreshed.
     */
    int reason = refreshCheck(entry, NULL, 60);
    refreshCounts[rcStore].total++;
    refreshCounts[rcStore].status[reason]++;
    if (reason < 200)
	/* Does not need refresh. This is certainly cachable */
	return 1;
    if (entry->lastmod < 0)
	/* Last modified is needed to do a refresh */
	return 0;
    if (entry->mem_obj == NULL)
	/* no mem_obj? */
	return 1;
    if (entry->mem_obj->reply == NULL)
	/* no reply? */
	return 1;
    if (entry->mem_obj->reply->content_length == 0)
	/* No use refreshing (caching?) 0 byte objects */
	return 0;
    /* This seems to be refreshable. Cache it */
    return 1;
}

/* refreshCheck... functions below are protocol-specific wrappers around
 * refreshCheck() function above */

int
refreshCheckHTTP(const StoreEntry * entry, request_t * request)
{
    int reason = refreshCheck(entry, request, 0);
    refreshCounts[rcHTTP].total++;
    refreshCounts[rcHTTP].status[reason]++;
    return (reason < 200) ? 0 : 1;
}

int
refreshCheckICP(const StoreEntry * entry, request_t * request)
{
    int reason = refreshCheck(entry, request, 30);
    refreshCounts[rcICP].total++;
    refreshCounts[rcICP].status[reason]++;
    return (reason < 200) ? 0 : 1;
}

#if USE_HTCP
int
refreshCheckHTCP(const StoreEntry * entry, request_t * request)
{
    int reason = refreshCheck(entry, request, 10);
    refreshCounts[rcHTCP].total++;
    refreshCounts[rcHTCP].status[reason]++;
    return (reason < 200) ? 0 : 1;
}
#endif

#if USE_CACHE_DIGESTS
int
refreshCheckDigest(const StoreEntry * entry, time_t delta)
{
    int reason = refreshCheck(entry,
	entry->mem_obj ? entry->mem_obj->request : NULL,
	delta);
    refreshCounts[rcCDigest].total++;
    refreshCounts[rcCDigest].status[reason]++;
    return (reason < 200) ? 0 : 1;
}
#endif

time_t
getMaxAge(const char *url)
{
    const refresh_t *R;
    debug(22, 3) ("getMaxAge: '%s'\n", url);
    if ((R = refreshLimits(url)))
	return R->max;
    else
	return REFRESH_DEFAULT_MAX;
}

static void
refreshCountsStats(StoreEntry * sentry, struct RefreshCounts *rc)
{
    int sum = 0;
    int tot = rc->total;

    storeAppendPrintf(sentry, "\n\n%s histogram:\n", rc->proto);
    storeAppendPrintf(sentry, "Count\t%%Total\tCategory\n");

#define refreshCountsStatsEntry(code,desc) { \
	storeAppendPrintf(sentry, "%6d\t%6.2f\t%s\n", \
	    rc->status[code], xpercent(rc->status[code], tot), desc); \
    sum += rc->status[code]; \
}

    refreshCountsStatsEntry(FRESH_REQUEST_MAX_STALE_ALL,
	"Fresh: request max-stale wildcard");
    refreshCountsStatsEntry(FRESH_REQUEST_MAX_STALE_VALUE,
	"Fresh: request max-stale value");
    refreshCountsStatsEntry(FRESH_EXPIRES,
	"Fresh: expires time not reached");
    refreshCountsStatsEntry(FRESH_LMFACTOR_RULE,
	"Fresh: refresh_pattern last-mod factor percentage");
    refreshCountsStatsEntry(FRESH_MIN_RULE,
	"Fresh: refresh_pattern min value");
    refreshCountsStatsEntry(FRESH_OVERRIDE_EXPIRES,
	"Fresh: refresh_pattern override expires");
    refreshCountsStatsEntry(FRESH_OVERRIDE_LASTMOD,
	"Fresh: refresh_pattern override lastmod");
    refreshCountsStatsEntry(STALE_MUST_REVALIDATE,
	"Stale: response has must-revalidate");
    refreshCountsStatsEntry(STALE_RELOAD_INTO_IMS,
	"Stale: changed reload into IMS");
    refreshCountsStatsEntry(STALE_FORCED_RELOAD,
	"Stale: request has no-cache directive");
    refreshCountsStatsEntry(STALE_EXCEEDS_REQUEST_MAX_AGE_VALUE,
	"Stale: age exceeds request max-age value");
    refreshCountsStatsEntry(STALE_EXPIRES,
	"Stale: expires time reached");
    refreshCountsStatsEntry(STALE_MAX_RULE,
	"Stale: refresh_pattern max age rule");
    refreshCountsStatsEntry(STALE_LMFACTOR_RULE,
	"Stale: refresh_pattern last-mod factor percentage");
    refreshCountsStatsEntry(STALE_DEFAULT,
	"Stale: by default");

    tot = sum;			/* paranoid: "total" line shows 100% if we forgot nothing */
    storeAppendPrintf(sentry, "%6d\t%6.2f\tTOTAL\n",
	rc->total, xpercent(rc->total, tot));
    \
	storeAppendPrintf(sentry, "\n");
}

static void
refreshStats(StoreEntry * sentry)
{
    int i;
    int total = 0;

    /* get total usage count */
    for (i = 0; i < rcCount; ++i)
	total += refreshCounts[i].total;

    /* protocol usage histogram */
    storeAppendPrintf(sentry, "\nRefreshCheck calls per protocol\n\n");
    storeAppendPrintf(sentry, "Protocol\t#Calls\t%%Calls\n");
    for (i = 0; i < rcCount; ++i)
	storeAppendPrintf(sentry, "%10s\t%6d\t%6.2f\n",
	    refreshCounts[i].proto,
	    refreshCounts[i].total,
	    xpercent(refreshCounts[i].total, total));

    /* per protocol histograms */
    storeAppendPrintf(sentry, "\n\nRefreshCheck histograms for various protocols\n");
    for (i = 0; i < rcCount; ++i)
	refreshCountsStats(sentry, &refreshCounts[i]);
}

void
refreshInit(void)
{
    memset(refreshCounts, 0, sizeof(refreshCounts));
    refreshCounts[rcHTTP].proto = "HTTP";
    refreshCounts[rcICP].proto = "ICP";
#if USE_HTCP
    refreshCounts[rcHTCP].proto = "HTCP";
#endif
    refreshCounts[rcStore].proto = "On Store";
#if USE_CACHE_DIGESTS
    refreshCounts[rcCDigest].proto = "Cache Digests";
#endif
    cachemgrRegister("refresh",
	"Refresh Algorithm Statistics",
	refreshStats,
	0,
	1);
    memset(&DefaultRefresh, '\0', sizeof(DefaultRefresh));
    DefaultRefresh.pattern = "<none>";
    DefaultRefresh.min = REFRESH_DEFAULT_MIN;
    DefaultRefresh.pct = REFRESH_DEFAULT_PCT;
    DefaultRefresh.max = REFRESH_DEFAULT_MAX;
}