Merge commit 'meins/next' into next

[paraslash.git] / mood.c

/*
 * Copyright (C) 2007-2009 Andre Noll <maan@systemlinux.org>
 *
 * Licensed under the GPL v2. For licencing details see COPYING.
 */

/** \file mood.c Paraslash's mood handling functions. */

#include <time.h>
#include <regex.h>
#include <fnmatch.h>
#include <osl.h>

#include "para.h"
#include "error.h"
#include "string.h"
#include "afh.h"
#include "afs.h"
#include "list.h"
#include "ipc.h"

/**
 * Contains statistical data of the currently admissible audio files.
 *
 * It is used to assign normalized score values to each admissible audio file.
 */
struct afs_statistics {
        /** Sum of num played over all admissible files. */
        int64_t num_played_sum;
        /** Sum of last played times over all admissible files. */
        int64_t last_played_sum;
        /** Quadratic deviation of num played time. */
        int64_t num_played_qd;
        /** Quadratic deviation of last played time. */
        int64_t last_played_qd;
        /** Number of admissible files */
        unsigned num;
};
struct afs_statistics statistics;

/**
 * Assign scores according to a mood_method.
 *
 * Each mood_method has its own mood_score_function. The first three parameters
 * passed to that function are informations about the audio file whose score is
 * to be computed. The data argument depends on the mood method this function
 * is used for. It usually is the argument given at the end of a mood line.
 *
 * Mood score functions must return values between -100 and +100 inclusively.
 * Boolean score functions should always return either -100 or +100.
 *
 * \sa struct mood_method, mood_parser.
 */
typedef int mood_score_function(const char *path, const struct afs_info *afsi,
                const struct afh_info *afhi, const void *data);

/**
 * Pre-process a mood line.
 *
 * The mood_parser of a mood_method is called once at mood open time for each
 * line of the current mood definition that contains the mood_method's name as
 * a keyword. The line is passed to the mood_parser as the first argument. The
 * mood_parser must determine whether the line is syntactically correct and
 * return a positive value if so and a negative value otherwise.
 *
 * Some mood parsers pre-process the data given in the mood line to compute a
 * structure which depends of the particular mood_method and which is used
 * later in the mood_score_function of the mood_method. The mood_parser may
 * store a pointer to its structure via the void** pointer.
 *
 * \sa mood_open(), mood_cleanup_function, mood_score_function.
 */
typedef int mood_parser(int, char **, void **);

/**
 * Deallocate resources which were allocated by the mood_parser.
 *
 * This optional function of a mood_method is used to free any resources
 * allocated in mood_open() by the mood_parser. The argument passed is a
 * pointer to the mood_method specific data structure that was returned by the
 * mood_parser.
 *
 * \sa mood_parser.
 */
typedef void mood_cleanup_function(void *);

/**
 * Used for scoring and to determine whether a file is admissible.
 */
struct mood_method {
        /** The name of the method. */
        const char *name;
        /** Pointer to the mood parser. */
        mood_parser *parser;
        /** Pointer to the score function */
        mood_score_function *score_function;
        /** Optional cleanup function. */
        mood_cleanup_function *cleanup;
};

/**
 * Each line of the current mood corresponds to a mood_item.
 */
struct mood_item {
        /** The method this line is referring to. */
        const struct mood_method *method;
        /** The data structure computed by the mood parser. */
        void *parser_data;
        /** The given score value, or zero if none was given. */
        int32_t score_arg;
        /** Non-zero if random scoring was requested. */
        int random_score;
        /** Whether the "not" keyword was given in the mood line. */
        int logical_not;
        /** The position in the list of items. */
        struct list_head mood_item_node;
};

/**
 * Created from the mood definition by mood_open().
 *
 * When a mood is opened, each line of its definition is investigated, and a
 * corresponding mood item is produced. Each mood line starts with \p accept,
 * \p deny, or \p score which determines the type of the mood line.  For each
 * such type a linked list is maintained whose entries are the mood items.
 *
 * \sa mood_item, mood_open().
 */
struct mood {
        /** The name of this mood. */
        char *name;
        /** The list of mood items of type \p accept. */
        struct list_head accept_list;
        /** The list of mood items of type \p deny. */
        struct list_head deny_list;
        /** The list of mood items of type \p score. */
        struct list_head score_list;
};

static struct mood *current_mood;

/**
 *  Rough approximation to sqrt.
 *
 *  \param x Integer of which to calculate the sqrt.
 *
 *  \return An integer res with res * res <= x.
 */
static uint64_t int_sqrt(uint64_t x)
{
        uint64_t op, res, one = 1;
        op = x;
        res = 0;

        one = one << 62;
        while (one > op)
                one >>= 2;

        while (one != 0) {
                if (op >= res + one) {
                        op = op - (res + one);
                        res = res +  2 * one;
                }
                res /= 2;
                one /= 4;
        }
//      PARA_NOTICE_LOG("sqrt(%llu) = %llu\n", x, res);
        return res;
}

#define MOOD_COMPARATORS \
        MC(LESS, <) \
        MC(LESS_OR_EQUAL, <=) \
        MC(EQUAL, =) \
        MC(EQUAL2, ==) \
        MC(NOT_EQUAL, !=) \
        MC(NOT_EQUAL2, <>) \
        MC(GREATER, >) \
        MC(GREATER_OR_EQUAL, >=) \

#define MC(a, b) MC_ ## a,
enum mood_comparator_id {MOOD_COMPARATORS NUM_MOOD_COMPARATORS};
#undef MC
#define MC(a, b) # b,
const char const *mood_comparators[] = {MOOD_COMPARATORS};
#undef MC

static int parse_mood_comparator(const char *word)
{
        int i;

        for (i = 0; i < NUM_MOOD_COMPARATORS; i++)
                if (!strcmp(word, mood_comparators[i]))
                        return i;
        return -E_MOOD_SYNTAX;
}

static int compare_int32(int32_t a, int32_t b, enum mood_comparator_id id)
{
        int res;

        switch (id) {
        case MC_LESS:
                res = a < b; break;
        case MC_LESS_OR_EQUAL:
                res = a <= b; break;
        case MC_EQUAL:
        case MC_EQUAL2:
                res = a == b; break;
        case MC_NOT_EQUAL:
        case MC_NOT_EQUAL2:
                res = a != b; break;
        case MC_GREATER:
                res = a > b; break;
        case MC_GREATER_OR_EQUAL:
                res = a >= b; break;
        default:
                PARA_EMERG_LOG("BUG: invalid mood comparator\n");
                exit(EXIT_FAILURE);
        }
        return res? 100 : -100;
}

struct mm_year_data {
        /** The year given at the mood line. */
        int32_t year;
        /** Used to detect Y2K issues. */
        int32_t current_year;
        /** <, <=, =, !=, >=, or >. */
        enum mood_comparator_id id;
};

static int mm_year_parser(int argc, char **argv, void **private)
{
        int ret = -E_MOOD_SYNTAX;
        struct mm_year_data *mmyd = para_malloc(sizeof(*mmyd));
        time_t current_time;
        struct tm *gmt;

        if (argc != 2)
                goto err;
        ret = parse_mood_comparator(argv[1]);
        mmyd->id = ret;
        if (ret < 0)
                goto err;
        ret = para_atoi32(argv[2], &mmyd->year);
        if (ret < 0)
                goto err;
        current_time = time(NULL);
        gmt = gmtime(&current_time);
        /* tm_year is the number of years since 1900 */
        mmyd->current_year = gmt->tm_year + 1900;
        *private = mmyd;
        return 1;
err:
        free(mmyd);
        return ret;
}

static int mm_year_score_function(__a_unused const char *path,
                __a_unused const struct afs_info *afsi,
                const struct afh_info *afhi,
                const void *private)
{
        const struct mm_year_data *mmyd = private;
        int32_t tag_year;
        int ret = para_atoi32(afhi->tags.year, &tag_year);

        if (ret < 0) /* year tag not present or not a number */
                return -100;
        if (tag_year < 0)
                return -100;
        /* try to work around Y2K issues */
        if (tag_year < 100) {
                tag_year += 1900;
                if (tag_year + 100 <= mmyd->current_year)
                        tag_year += 100; /* assume tag_year >= 2000 */
        }
        return compare_int32(tag_year, mmyd->year, mmyd->id);
}

static void mm_year_cleanup(void *private)
{
        free(private);
}

static int mm_no_attributes_set_parser(int argc, __a_unused char **argv,
                __a_unused void **ignored)
{
        return argc? -E_MOOD_SYNTAX : 1;
}

static int mm_no_attributes_set_score_function(__a_unused const char *path,
                const struct afs_info *afsi,
                __a_unused const struct afh_info *afhi,
                __a_unused const void *data)
{
        if (!afsi->attributes)
                return 100;
        return -100;
}

static int mm_played_rarely_score_function(__a_unused const char *path,
                const struct afs_info *afsi,
                __a_unused const struct afh_info *afhi,
                __a_unused const void *data)
{
        unsigned num;
        int ret = get_num_admissible_files(&num);

        if (ret < 0)
                return 0;
        if (statistics.num_played_sum - num * afsi->num_played
                        > int_sqrt(statistics.num_played_qd * num))
                return 100;
        return -100;
}

static int mm_played_rarely_parser(int argc, __a_unused char **argv,
                __a_unused void **ignored)
{
        return argc? -E_MOOD_SYNTAX : 1;
}

static int mm_path_matches_score_function(const char *path,
                __a_unused const struct afs_info *afsi,
                __a_unused const struct afh_info *afhi,
                const void *data)
{
        if (fnmatch(data, path, 0))
                return -100;
        return 100;
}

static int mm_path_matches_parser(int argc, char **argv, void **data)
{
        if (argc != 1)
                return -E_MOOD_SYNTAX;
        *data = para_strdup(argv[1]);
        return 1;
}

static void mm_path_matches_cleanup(void *data)
{
        free(data);
}

static int mm_is_set_parser(int argc, char **argv, void **bitnum)
{
        int ret;
        unsigned char c, *res;

        if (argc != 1)
                return -E_MOOD_SYNTAX;
        ret = get_attribute_bitnum_by_name(argv[1], &c);
        if (ret < 0)
                return ret;
        res = para_malloc(1);
        *res = c;
        *bitnum = res;
        return 1;
}

static int mm_is_set_score_function(__a_unused const char *path,
                __a_unused const struct afs_info *afsi,
                __a_unused const struct afh_info *afhi,
                const void *data)
{
        const unsigned char *bn = data;
        if (afsi->attributes & (1ULL << *bn))
                return 100;
        return -100;
}

/* returns 1 if row matches score item, negative otherwise */
static int add_item_score(const struct osl_row *row, struct mood_item *item, long *score,
                long *score_arg_sum)
{
        struct afs_info afsi;
        struct afh_info afhi;
        char *path;
        int ret;

        *score_arg_sum += item->random_score? 100 : PARA_ABS(item->score_arg);
        ret = 100;
        if (item->method) {
                ret = get_afsi_of_row(row, &afsi);
                if (ret< 0)
                        return ret;
                ret = get_afhi_of_row(row, &afhi);
                if (ret< 0)
                        return ret;
                ret = get_audio_file_path_of_row(row, &path);
                if (ret< 0)
                        return ret;
                ret = item->method->score_function(path, &afsi, &afhi,
                        item->parser_data);
                if ((ret < 0 && !item->logical_not) || (ret >= 0 && item->logical_not))
                        return -1; /* no match */
        }
        if (item->random_score)
                *score += PARA_ABS(ret) * para_random(100);
        else
                *score += PARA_ABS(ret) * item->score_arg;
        return 1;
}

static int compute_mood_score(const struct osl_row *aft_row, struct mood *m,
                long *result)
{
        struct mood_item *item;
        int match = 0;
        long score_arg_sum = 0, score = 0;

        if (!m)
                return -E_NO_MOOD;
        /* reject audio file if it matches any entry in the deny list */
        list_for_each_entry(item, &m->deny_list, mood_item_node)
                if (add_item_score(aft_row, item, &score, &score_arg_sum) > 0)
                        return -E_NOT_ADMISSIBLE;
        list_for_each_entry(item, &m->accept_list, mood_item_node)
                if (add_item_score(aft_row, item, &score, &score_arg_sum) > 0)
                        match = 1;
        /* reject if there is no matching entry in the accept list */
        if (!match && !list_empty(&m->accept_list))
                return -E_NOT_ADMISSIBLE;
        list_for_each_entry(item, &m->score_list, mood_item_node)
                add_item_score(aft_row, item, &score, &score_arg_sum);
        if (score_arg_sum)
                score /= score_arg_sum;
        *result = score;
        return 1;
}

#define DEFINE_MOOD_METHOD(_name) \
.parser = mm_ ## _name ## _parser, \
.score_function = mm_ ## _name ## _score_function, \
.name = #_name

#define DEFINE_MOOD_METHOD_WITH_CLEANUP(_name) \
        DEFINE_MOOD_METHOD(_name), \
        .cleanup = mm_ ## _name ## _cleanup

static const struct mood_method mood_methods[] = {
        {DEFINE_MOOD_METHOD(no_attributes_set)},
        {DEFINE_MOOD_METHOD(played_rarely)},
        {DEFINE_MOOD_METHOD(is_set)},
        {DEFINE_MOOD_METHOD_WITH_CLEANUP(path_matches)},
        {DEFINE_MOOD_METHOD_WITH_CLEANUP(year)},
        {.parser = NULL}
};

static void cleanup_list_entry(struct mood_item *item)
{
        if (item->method && item->method->cleanup)
                item->method->cleanup(item->parser_data);
        else
                free(item->parser_data);
        list_del(&item->mood_item_node);
        free(item);
}

static void destroy_mood(struct mood *m)
{
        struct mood_item *tmp, *item;

        if (!m)
                return;
        list_for_each_entry_safe(item, tmp, &m->accept_list, mood_item_node)
                cleanup_list_entry(item);
        list_for_each_entry_safe(item, tmp, &m->deny_list, mood_item_node)
                cleanup_list_entry(item);
        list_for_each_entry_safe(item, tmp, &m->score_list, mood_item_node)
                cleanup_list_entry(item);
        free(m->name);
        free(m);
}

static struct mood *alloc_new_mood(const char *name)
{
        struct mood *m = para_calloc(sizeof(struct mood));
        m->name = para_strdup(name);
        INIT_LIST_HEAD(&m->accept_list);
        INIT_LIST_HEAD(&m->deny_list);
        INIT_LIST_HEAD(&m->score_list);
        return m;
}

/** The different types of a mood line. */
enum mood_line_type {
        /** Invalid. */
        ML_INVALID,
        /** Accept line. */
        ML_ACCEPT,
        /** Deny line. */
        ML_DENY,
        /** Score line. */
        ML_SCORE
};

/** Data passed to the parser of a mood line. */
struct mood_line_parser_data {
        /** The mood this mood line belongs to. */
        struct mood *m;
        /** The line number in the mood definition. */
        unsigned line_num;
};

/*
 * <accept [with score <score>] | deny [with score <score>]  | score <score>>
 *      [if] [not] <mood_method> [options]
 * <score> is either an integer or "random" which assigns a random score to
 * all matching files
 */

static int parse_mood_line(char *mood_line, void *data)
{
        struct mood_line_parser_data *mlpd = data;
        char **argv;
        unsigned num_words;
        char **w;
        int i, ret;
        enum mood_line_type mlt = ML_INVALID;
        struct mood_item *mi = NULL;

        mlpd->line_num++;
        ret = create_argv(mood_line, " \t", &argv);
        if (ret < 0)
                return ret;
        num_words = ret;
        if (!num_words) /* empty line */
                goto out;
        w = argv;
        if (**w == '#') /* comment */
                goto out;
        if (!strcmp(*w, "accept"))
                mlt = ML_ACCEPT;
        else if (!strcmp(*w, "deny"))
                mlt = ML_DENY;
        else if (!strcmp(*w, "score"))
                mlt = ML_SCORE;
        ret = -E_MOOD_SYNTAX;
        if (mlt == ML_INVALID)
                goto out;
        mi = para_calloc(sizeof(struct mood_item));
        if (mlt != ML_SCORE) {
                ret = -E_MOOD_SYNTAX;
                w++;
                if (!*w)
                        goto out;
                if (strcmp(*w, "with"))
                        goto check_for_if;
                w++;
                if (!*w)
                        goto out;
                if (strcmp(*w, "score"))
                        goto out;
        }
        if (mlt == ML_SCORE || !strcmp(*w, "score")) {
                ret = -E_MOOD_SYNTAX;
                w++;
                if (!*w)
                        goto out;
                if (strcmp(*w, "random")) {
                        mi->random_score = 0;
                        ret = para_atoi32(*w, &mi->score_arg);
                        if (ret < 0)
                                goto out;
                } else {
                        mi->random_score = 1;
                        if (!*(w + 1))
                        goto success; /* the line "score random" is valid */
                }
        } else
                mi->score_arg = 0;
        ret = -E_MOOD_SYNTAX;
        w++;
        if (!*w)
                goto out;
check_for_if:
        if (!strcmp(*w, "if")) {
                ret = -E_MOOD_SYNTAX;
                w++;
                if (!*w)
                        goto out;
        }
        if (!strcmp(*w, "not")) {
                ret = -E_MOOD_SYNTAX;
                w++;
                if (!*w)
                        goto out;
                mi->logical_not = 1;
        } else
                mi->logical_not = 0;
        for (i = 0; mood_methods[i].parser; i++) {
                if (strcmp(*w, mood_methods[i].name))
                        continue;
                break;
        }
        ret = -E_MOOD_SYNTAX;
        if (!mood_methods[i].parser)
                goto out;
        ret = mood_methods[i].parser(num_words - 1 - (w - argv), w,
                &mi->parser_data);
        if (ret < 0)
                goto out;
        mi->method = &mood_methods[i];
success:
        if (mlpd->m) {
                if (mlt == ML_ACCEPT)
                        para_list_add(&mi->mood_item_node, &mlpd->m->accept_list);
                else if (mlt == ML_DENY)
                        para_list_add(&mi->mood_item_node, &mlpd->m->deny_list);
                else
                        para_list_add(&mi->mood_item_node, &mlpd->m->score_list);
        }
        PARA_DEBUG_LOG("%s entry added, method: %p\n", mlt == ML_ACCEPT? "accept" :
                (mlt == ML_DENY? "deny" : "score"), mi->method);
        ret = 1;
out:
        free_argv(argv);
        if (ret >= 0)
                return ret;
        if (mi) {
                free(mi->parser_data);
                free(mi);
        }
        return ret;
}

static int load_mood(const struct osl_row *mood_row, struct mood **m)
{
        char *mood_name;
        struct osl_object mood_def;
        struct mood_line_parser_data mlpd = {.line_num = 0};
        int ret = mood_get_name_and_def_by_row(mood_row, &mood_name, &mood_def);

        if (ret < 0)
                return ret;
        if (!*mood_name)
                return -E_DUMMY_ROW;
        mlpd.m = alloc_new_mood(mood_name);
        ret = for_each_line_ro(mood_def.data, mood_def.size,
                parse_mood_line, &mlpd);
        osl_close_disk_object(&mood_def);
        if (ret < 0) {
                PARA_ERROR_LOG("unable to load mood %s: %s\n", mlpd.m->name,
                        para_strerror(-ret));
                destroy_mood(mlpd.m);
                return ret;
        }
        *m = mlpd.m;
        return 1;
}

static int check_mood(struct osl_row *mood_row, void *data)
{
        struct para_buffer *pb = data;
        char *mood_name;
        struct osl_object mood_def;
        struct mood_line_parser_data mlpd = {.line_num = 0};

        int ret = mood_get_name_and_def_by_row(mood_row, &mood_name, &mood_def);

        if (ret < 0) {
                para_printf(pb, "failed to get mood definition: %s\n",
                        para_strerror(-ret));
                return ret;
        }
        if (!*mood_name) /* ignore dummy row */
                goto out;
        ret = para_printf(pb, "checking mood %s...\n", mood_name);
        if (ret < 0)
                goto out;
        ret = for_each_line_ro(mood_def.data, mood_def.size,
                parse_mood_line, &mlpd);
        if (ret < 0)
                para_printf(pb, "%s line %u: %s\n", mood_name, mlpd.line_num,
                        para_strerror(-ret));
out:
        osl_close_disk_object(&mood_def);
        return ret;
}

/**
 * Check all moods for syntax errors.
 *
 * \param fd The afs socket.
 * \param query Unused.
 */
void mood_check_callback(int fd, __a_unused const struct osl_object *query)
{
        struct para_buffer pb = {
                .max_size = SHMMAX,
                .private_data = &fd,
                .max_size_handler = pass_buffer_as_shm
        };

        int ret = para_printf(&pb, "checking moods...\n");
        if (ret < 0)
                return;
        osl_rbtree_loop(moods_table, BLOBCOL_ID, &pb,
                check_mood);
        if (pb.offset)
                pass_buffer_as_shm(pb.buf, pb.offset, &fd);
        free(pb.buf);
}

#if 0
static unsigned int_log2(uint64_t x)
{
        unsigned res = 0;

        while (x) {
                x /= 2;
                res++;
        }
        return res;
}
#endif

static int64_t normalized_value(int64_t x, int64_t n, int64_t sum, int64_t qd)
{
        if (!n || !qd)
                return 0;
        return 100 * (n * x - sum) / (int64_t)int_sqrt(n * qd);
}

static long compute_num_played_score(struct afs_info *afsi)
{
        return -normalized_value(afsi->num_played, statistics.num,
                statistics.num_played_sum, statistics.num_played_qd);
}

static long compute_last_played_score(struct afs_info *afsi)
{
        return -normalized_value(afsi->last_played, statistics.num,
                statistics.last_played_sum, statistics.last_played_qd);
}

static long compute_dynamic_score(const struct osl_row *aft_row)
{
        struct afs_info afsi;
        int64_t score, nscore = 0, lscore = 0;
        int ret;

        ret = get_afsi_of_row(aft_row, &afsi);
        if (ret < 0)
                return -100;
        nscore = compute_num_played_score(&afsi);
        lscore = compute_last_played_score(&afsi);
        score = nscore + lscore;
        return score;
}

static int add_afs_statistics(const struct osl_row *row)
{
        uint64_t n, x, s;
        struct afs_info afsi;
        int ret;

        ret = get_afsi_of_row(row, &afsi);
        if (ret < 0)
                return ret;
        n = statistics.num;
        x = afsi.last_played;
        s = statistics.last_played_sum;
        if (n > 0)
                statistics.last_played_qd += (x - s / n) * (x - s / n) * n / (n + 1);
        statistics.last_played_sum += x;

        x = afsi.num_played;
        s = statistics.num_played_sum;
        if (n > 0)
                statistics.num_played_qd += (x - s / n) * (x - s / n) * n / (n + 1);
        statistics.num_played_sum += x;
        statistics.num++;
        return 1;
}

static int del_afs_statistics(const struct osl_row *row)
{
        uint64_t n, s, q, a, new_s;
        struct afs_info afsi;
        int ret;
        ret = get_afsi_of_row(row, &afsi);
        if (ret < 0)
                return ret;
        n = statistics.num;
        assert(n);
        if (n == 1) {
                memset(&statistics, 0, sizeof(statistics));
                return 1;
        }

        s = statistics.last_played_sum;
        q = statistics.last_played_qd;
        a = afsi.last_played;
        new_s = s - a;
        statistics.last_played_sum = new_s;
        statistics.last_played_qd = q + s * s / n - a * a
                - new_s * new_s / (n - 1);

        s = statistics.num_played_sum;
        q = statistics.num_played_qd;
        a = afsi.num_played;
        new_s = s - a;
        statistics.num_played_sum = new_s;
        statistics.num_played_qd = q + s * s / n - a * a
                - new_s * new_s / (n - 1);

        statistics.num--;
        return 1;
}

/**
 * Structure used during mood_open().
 *
 * At mood open time, we look at each file in the audio file table in order to
 * determine whether it is admissible. If a file happens to be admissible, its
 * mood score is computed by calling each relevant mood_score_function. Next,
 * we update the afs_statistics and add a struct admissible_file_info to a
 * temporary array.
 *
 * If all files have been processed that way, the final score of each
 * admissible file is computed by adding the dynamic score (which depends on
 * the afs_statistics) to the mood score.  Finally, all audio files in the
 * array are added to the score table and the admissible array is freed.
 *
 * \sa mood_method, admissible_array.
 */
struct admissible_file_info
{
        /** The admissible audio file. */
        struct osl_row *aft_row;
        /** Its score. */
        long score;
};

/** The temporary array of admissible files. */
struct admissible_array {
        /** Files are admissible wrt. this mood. */
        struct mood *m;
        /** The size of the array */
        unsigned size;
        /** Pointer to the array of admissible files. */
        struct admissible_file_info *array;
};

/**
 * Add an entry to the array of admissible files.
 *
 * \param aft_row The audio file to be added.
 * \param private_data Pointer to a struct admissible_file_info.
 *
 * \return Negative on errors, positive on success.
 */
static int add_if_admissible(struct osl_row *aft_row, void *data)
{
        struct admissible_array *aa = data;
        int ret;
        long score = 0;

        ret = compute_mood_score(aft_row, aa->m, &score);
        if (ret < 0)
                return (ret == -E_NOT_ADMISSIBLE)? 1 : ret;
        if (statistics.num >= aa->size) {
                aa->size *= 2;
                aa->size += 100;
                aa->array = para_realloc(aa->array,
                        aa->size * sizeof(struct admissible_file_info));
        }
        aa->array[statistics.num].aft_row = aft_row;
        aa->array[statistics.num].score = score;
        ret = add_afs_statistics(aft_row);
        if (ret < 0)
                return ret;
        return 1;
}

/**
 * Compute the new quadratic deviation in case one element changes.
 *
 * \param n Number of elements.
 * \param old_qd The quadratic deviation before the change.
 * \param old_val The value that was replaced.
 * \param new_val The replacement value.
 * \param old_sum The sum of all elements before the update.
 *
 * \return The new quadratic deviation resulting from replacing old_val
 * by new_val.
 *
 * Given n real numbers a_1, ..., a_n, their sum S = a_1 + ... + a_n,
 * their quadratic deviation
 *
 * q = (a_1 - S/n)^2 + ... + (a_n - S/n)^2,
 *
 * and a real number b, the quadratic deviation q' of a_1,...a_{n-1}, b (ie.
 * the last number a_n was replaced by b) may be computed in O(1) time in terms
 * of n, q, a_n, b, and S as
 *
 *      q' = q + d * s - (2 * S + d) * d / n,
 *
 * where d = b - a_n, and s = b + a_n.
 *
 * Example: n = 3, a_1 = 3, a_2 = 5, a_3 = 7, b = 10. Then S = 15, q = 8, d = 3,
 * s = 17, so
 *
 *      q + d * s - (2 * S + d) * d / n = 8 + 51 - 33 = 26,
 *
 * which equals q' = (3 - 6)^2 + (5 - 6)^2 + (10 - 6)^2.
 *
 */
_static_inline_ int64_t update_quadratic_deviation(int64_t n, int64_t old_qd,
                int64_t old_val, int64_t new_val, int64_t old_sum)
{
        int64_t delta = new_val - old_val;
        int64_t sigma = new_val + old_val;
        return old_qd + delta * sigma - (2 * old_sum + delta) * delta / n;
}

static int update_afs_statistics(struct afs_info *old_afsi, struct afs_info *new_afsi)
{
        unsigned n;
        int ret = get_num_admissible_files(&n);

        if (ret < 0)
                return ret;
        assert(n);

        statistics.last_played_qd = update_quadratic_deviation(n,
                statistics.last_played_qd, old_afsi->last_played,
                new_afsi->last_played, statistics.last_played_sum);
        statistics.last_played_sum += new_afsi->last_played - old_afsi->last_played;

        statistics.num_played_qd = update_quadratic_deviation(n,
                statistics.num_played_qd, old_afsi->num_played,
                new_afsi->num_played, statistics.num_played_sum);
        statistics.num_played_sum += new_afsi->num_played - old_afsi->num_played;
        return 1;
}

static int add_to_score_table(const struct osl_row *aft_row, long mood_score)
{
        long score = (compute_dynamic_score(aft_row) + mood_score) / 3;
        return score_add(aft_row, score);
}

static int delete_from_statistics_and_score_table(const struct osl_row *aft_row)
{
        int ret = del_afs_statistics(aft_row);
        if (ret < 0)
                return ret;
        return score_delete(aft_row);
}

/**
 * Delete one entry from the statistics and from the score table.
 *
 * \param aft_row The audio file which is no longer admissible.
 *
 * \return Positive on success, negative on errors.
 *
 * \sa score_delete().
 */
static int mood_delete_audio_file(const struct osl_row *aft_row)
{
        int ret;

        ret = row_belongs_to_score_table(aft_row, NULL);
        if (ret < 0)
                return ret;
        if (!ret) /* not admissible, nothing to do */
                return 1;
        return delete_from_statistics_and_score_table(aft_row);
}

/**
 * Compute the new score of an audio file wrt. the current mood.
 *
 * \param aft_row Determines the audio file.
 * \param old_afsi The audio file selector info before updating.
 *
 * The \a old_afsi argument may be \p NULL which indicates that no changes to
 * the audio file info were made.
 *
 * \return Positive on success, negative on errors.
 */
static int mood_update_audio_file(const struct osl_row *aft_row,
                struct afs_info *old_afsi)
{
        long score, percent;
        int ret, is_admissible, was_admissible = 0;
        struct afs_info afsi;
        unsigned rank;

        if (!current_mood)
                return 1; /* nothing to do */
        ret = row_belongs_to_score_table(aft_row, &rank);
        if (ret < 0)
                return ret;
        was_admissible = ret;
        ret = compute_mood_score(aft_row, current_mood, &score);
        is_admissible = (ret > 0);
        if (!was_admissible && !is_admissible)
                return 1;
        if (was_admissible && !is_admissible)
                return delete_from_statistics_and_score_table(aft_row);
        if (!was_admissible && is_admissible) {
                ret = add_afs_statistics(aft_row);
                if (ret < 0)
                        return ret;
                return add_to_score_table(aft_row, score);
        }
        /* update score */
        ret = get_afsi_of_row(aft_row, &afsi);
        if (ret < 0)
                return ret;
        if (old_afsi) {
                ret = update_afs_statistics(old_afsi, &afsi);
                if (ret < 0)
                        return ret;
        }
        score += compute_num_played_score(&afsi);
        score += compute_last_played_score(&afsi);
        score /= 3;
        PARA_DEBUG_LOG("score: %li\n", score);
        percent = (score + 100) / 3;
        if (percent > 100)
                percent = 100;
        else if (percent < 0)
                percent = 0;
        PARA_DEBUG_LOG("moving from rank %u to %lu%%\n", rank, percent);
        return score_update(aft_row, percent);
}

static void log_statistics(void)
{
        unsigned n = statistics.num;

        if (!n) {
                PARA_NOTICE_LOG("no admissible files\n");
                return;
        }
        PARA_INFO_LOG("last_played mean: %lli, last_played sigma: %llu\n",
                (long long int)(statistics.last_played_sum / n),
                (long long unsigned)int_sqrt(statistics.last_played_qd / n));
        PARA_INFO_LOG("num_played mean: %lli, num_played sigma: %llu\n",
                (long long int)statistics.num_played_sum / n,
                (long long unsigned)int_sqrt(statistics.num_played_qd / n));
}

/**
 * Close the current mood.
 *
 * Free all resources of the current mood which were allocated during
 * mood_open().
 */
void close_current_mood(void)
{
        destroy_mood(current_mood);
        current_mood = NULL;
        memset(&statistics, 0, sizeof(statistics));
}


/**
 * Change the current mood.
 *
 * \param mood_name The name of the mood to open.
 *
 * If \a mood_name is \a NULL, load the dummy mood that accepts every audio file
 * and uses a scoring method based only on the \a last_played information.
 *
 * If there is already an open mood, it will be closed first.
 *
 * \return Positive on success, negative on errors. Loading the dummy mood
 * always succeeds.
 *
 * \sa struct admissible_file_info, struct admissible_array, struct
 * afs_info::last_played, mood_close().
 */
int change_current_mood(char *mood_name)
{
        int i, ret;
        struct admissible_array aa = {
                .size = 0,
                .array = NULL
        };

        if (mood_name) {
                struct mood *m;
                struct osl_row *row;
                struct osl_object obj = {
                        .data = mood_name,
                        .size = strlen(mood_name) + 1
                };
                ret = osl(osl_get_row(moods_table, BLOBCOL_NAME, &obj, &row));
                if (ret < 0) {
                        PARA_NOTICE_LOG("no such mood: %s\n", mood_name);
                        return ret;
                }
                ret = load_mood(row, &m);
                if (ret < 0)
                        return ret;
                close_current_mood();
                current_mood = m;
        } else {
                close_current_mood();
                current_mood = alloc_new_mood("dummy");
        }
        aa.m = current_mood;
        PARA_NOTICE_LOG("computing statistics of admissible files\n");
        ret = audio_file_loop(&aa, add_if_admissible);
        if (ret < 0)
                return ret;
        log_statistics();
        PARA_INFO_LOG("%d admissible files \n", statistics.num);
        for (i = 0; i < statistics.num; i++) {
                struct admissible_file_info *a = aa.array + i;
                ret = add_to_score_table(a->aft_row, a->score);
                if (ret < 0)
                        goto out;
        }
        PARA_NOTICE_LOG("loaded mood %s\n", current_mood->name);
        ret = statistics.num;
out:
        free(aa.array);
        return ret;
}
/**
 * Close and re-open the current mood.
 *
 * This function is used if changes to the audio file table or the
 * attribute table were made that render the current list of admissible
 * files useless. For example, if an attribute is removed from the
 * attribute table, this function is called.
 *
 * \return Positive on success, negative on errors. If no mood is currently
 * open, the function returns success.
 *
 * \sa mood_open(), mood_close().
 */
int reload_current_mood(void)
{
        int ret;
        char *mood_name = NULL;

        if (!current_mood)
                return 1;
        PARA_NOTICE_LOG("reloading %s\n", current_mood->name?
                current_mood->name : "(dummy)");
        if (current_mood->name)
                mood_name = para_strdup(current_mood->name);
        close_current_mood();
        ret = change_current_mood(mood_name);
        free(mood_name);
        return ret;
}

int moods_event_handler(enum afs_events event, __a_unused struct para_buffer *pb,
                void *data)
{
        switch(event) {
        /*
         * The three blob events might change the set of admissible files,
         * so we must reload the score list.
         */
        case BLOB_RENAME:
        case BLOB_REMOVE:
        case BLOB_ADD:
                if (data == moods_table || data == playlists_table)
                        return 1; /* no reload necessary for these */
                return reload_current_mood();
        /* these also require reload of the score table */
        case ATTRIBUTE_ADD:
        case ATTRIBUTE_REMOVE:
        case ATTRIBUTE_RENAME:
                return reload_current_mood();
        /* changes to the aft only require to re-examine the audio file */
        case AFSI_CHANGE: {
                struct afsi_change_event_data *aced = data;
                return mood_update_audio_file(aced->aft_row, aced->old_afsi);
                }
        case AFHI_CHANGE:
        case AUDIO_FILE_RENAME:
        case AUDIO_FILE_ADD:
                return mood_update_audio_file(data, NULL);
        case AUDIO_FILE_REMOVE:
                return mood_delete_audio_file(data);
        default:
                return 1;
        }
}