#ifndef PG_DIFFIX_CONTRIBUTION_TRACKER_H
#define PG_DIFFIX_CONTRIBUTION_TRACKER_H

#include "nodes/pg_list.h"

#include "pg_diffix/aggregation/aid.h"
#include "pg_diffix/aggregation/common.h"
#include "pg_diffix/aggregation/noise.h"

typedef union contribution_t
{
  int64 integer;
  float8 real;
} contribution_t;

/* Returns whether x is "more" contribution than y. */
typedef bool (*ContributionGreaterFunc)(contribution_t x, contribution_t y);

/* Returns whether x and y are equal contributions. */
typedef bool (*ContributionEqualFunc)(contribution_t x, contribution_t y);

/* Combines x and y and to a single contribution. */
typedef contribution_t (*ContributionCombineFunc)(contribution_t x, contribution_t y);

typedef struct ContributionDescriptor
{
  ContributionGreaterFunc contribution_greater;
  ContributionEqualFunc contribution_equal;
  ContributionCombineFunc contribution_combine;
  contribution_t contribution_initial; /* Initial or "zero" value for a contribution */
} ContributionDescriptor;

typedef struct Contributor
{
  aid_t aid;
  contribution_t contribution;
} Contributor;

typedef struct Contributors
{
  uint32 length;
  uint32 capacity;
  Contributor members[FLEXIBLE_ARRAY_MEMBER];
} Contributors;

typedef struct ContributionTrackerHashEntry
{
  Contributor contributor; /* Contributor info */
  char status;             /* Required for hash table */
} ContributionTrackerHashEntry;

/*
 * Declarations for HashTable<aid_t, ContributionTrackerHashEntry>
 */
#define SH_PREFIX ContributionTracker
#define SH_ELEMENT_TYPE ContributionTrackerHashEntry
#define SH_KEY_TYPE aid_t
#define SH_SCOPE extern
#define SH_DECLARE
#include "lib/simplehash.h"

typedef struct ContributionTrackerState
{
  MapAidFunc aid_mapper;                          /* Creator of AIDs from Datums */
  ContributionDescriptor contribution_descriptor; /* Behavior for contributions */
  ContributionTracker_hash *contribution_table;   /* Hash set of all AIDs */
  seed_t aid_seed;                                /* Current AID seed */
  uint64 distinct_contributors;                   /* Count of distinct non-NULL contributors */
  contribution_t overall_contribution;            /* Combined contribution from all contributors */
  uint64 unaccounted_for;                         /* Count of NULL contributions unaccounted for */
  /* Variable size field, has to be last in the list. */
  Contributors top_contributors; /* AIDs with largest contributions */
} ContributionTrackerState;

/*
 * Updates state with a contribution from an AID. `contribution` must be greater than zero.
 */
extern void contribution_tracker_update_contribution(
    ContributionTrackerState *state,
    aid_t aid,
    contribution_t contribution);

/*
 * Creates a new state for tracking aggregation contributions.
 */
extern ContributionTrackerState *contribution_tracker_new(
    MapAidFunc aid_mapper,
    const ContributionDescriptor *contribution_descriptor);

extern void add_top_contributor(
    const ContributionDescriptor *descriptor,
    Contributors *top_contributors,
    Contributor contributor);

extern void update_or_add_top_contributor(
    const ContributionDescriptor *descriptor,
    Contributors *top_contributors,
    Contributor contributor);

#endif /* PG_DIFFIX_CONTRIBUTION_TRACKER_H */