#ifndef PURE_MODULE_LIST_H
#define PURE_MODULE_LIST_H
#include "result.h"
#include "state.h"
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>

/* Executor paths that run once per module or app (loading, verifying,
 * starting, replacing, reading stored states) are built for size; events
 * stay built for speed. */
#if defined(__GNUC__) || defined(__clang__)
#define PURE_COLD __attribute__((cold))
#else
#define PURE_COLD
#endif

/* Runtime-owned lists of records for the module executor. An item is one
 * cell per field: a number, an integer, or text bytes the list owns. Every
 * change made during an event is logged; a failed event undoes the log in
 * reverse and a successful one frees what it replaced. */
typedef struct { union { double num; int64_t i64; }; unsigned char *text; size_t size; } PureCell;
typedef struct PureList PureList;
/* An event's list changes; a removed item's cells wait in cells. */
typedef struct {
    void *entries;
    size_t count, capacity;
    PureCell *cells;
    size_t cell_count, cell_capacity;
} PureUndo;
/* Nodes and texts a list let go while a shared copy may still read them. */
typedef struct { void *entries; size_t count, capacity; } PureRetired;
/* Items one after another, as a leaf of the list keeps them: positions start
 * to start + count - 1, each field's cells side by side (a number field's as
 * numbers, a text field's as spans). */
typedef struct {
    size_t start;
    unsigned count;
    union { const double *numbers; const int64_t *integers; const PureSpan *texts; } column[16];
    /* Where the run is in the list's tree, for the next one (path[depth]
     * its leaf); pathless: its leaf alone is known (the next is found from
     * the root). */
    const void *path[16];
    uint8_t taken[16];
    unsigned depth;
    bool pathless;
    double cells[16][32]; /* an array's narrow cells as numbers (docs/design/022) */
} PureRun;

/* A list holds up to PURE_LIST_ITEMS items, a run up to PURE_LIST_RUN. */
enum { PURE_LIST_ITEMS = 1 << 24, PURE_LIST_RUN = 32 };

/* A field's kind: a number, a text (UTF-8, checked when read), bytes (any: a
 * runtime list's), a bool (a number 0 or 1, kept as a number is) or an
 * integer (an int64_t, ordered as one). A stored list's header names its
 * fields by these kinds. */
enum { PURE_CELL_NUMBER = 0, PURE_CELL_TEXT = 1, PURE_CELL_BYTES = 2, PURE_CELL_BOOL = 3, PURE_CELL_INTEGER = 4 };
static inline bool pure_cell_text(uint8_t kind) { return kind == PURE_CELL_TEXT || kind == PURE_CELL_BYTES; }
/* Whether a number, bool or integer cell holds what its kind may: a finite
 * number, a bool 0 or 1 (either zero), any integer. */
bool pure_cell_fits(uint8_t kind, PureCell cell);
/* A number, a bool or an integer as another of them holds it (a module
 * replaced, a stored value read by another module, a waiting send recast):
 * true with *cell made the other when it fits (a bool from 0 or 1, either
 * zero false; a number from an integer within 2^53; an integer from a
 * whole number in its range), else false. Texts only as themselves. */
bool pure_cell_as(uint8_t from, uint8_t to, PureCell *cell);
PureList *pure_list_new(unsigned fields, const uint8_t *kinds);
void pure_list_free(PureList *);
/* Let every item go (retired where a shared copy may read it). */
void pure_list_clear(PureList *);
size_t pure_list_count(const PureList *);
/* Share the items as they are with a read-only copy (for readers on other
 * threads), without copying them: from then on the list copies the nodes it
 * changes, and nodes and texts it lets go go to retired instead of being
 * freed, since the copy may still read them. The copy is freed with
 * pure_list_free, on any thread, when its last reference goes
 * (pure_list_hold takes one more). Only between events (no change waits to
 * be committed or undone). epoch numbers the copy (as a snapshot of an app
 * numbers its lists' copies, one number for all of them): a node or text
 * the list makes after it has the epoch, and a copy of epoch e reads only
 * what was made before e. */
PureList *pure_list_share(PureList *, PureRetired *retired, uint64_t epoch);
/* A copy made before and still current (the list unchanged since) is read
 * as of epoch too: what the list lets go from now on is retired. */
void pure_list_mark(PureList *, uint64_t epoch);
/* Of what was retired, what a copy of epoch may still read (made before
 * it) goes to kept (none when kept is NULL), and the rest to gone, for
 * pure_retired_reuse or pure_retired_free (later, and where it pleases):
 * from is left empty, with its room (pure_retired_free lets that go). */
void pure_retired_pass(PureRetired *from, uint64_t epoch, PureRetired *kept, PureRetired *gone);
/* What was retired and no copy reads any more, on the lists' thread: each
 * node goes back to a list of its size, to be made again, as many as the
 * list made lately (at least a few: what it made counts half again at each
 * return); the rest and the texts are freed. returned is left empty, with
 * its room. */
void pure_retired_reuse(PureRetired *returned, PureList *const *lists, unsigned count);
void pure_list_hold(PureList *copy);
/* Whether copy shares list's items as they are now. */
bool pure_list_current(const PureList *copy, const PureList *list);
/* Which list, and its version: the same pair means the same items. */
void pure_list_stamp(const PureList *, uint64_t *id, uint64_t *version);
/* Free what was retired while no copy that shared it remains. */
void pure_retired_free(PureRetired *);
/* Insert a copy of cells (text bytes are copied) before position at. A NULL
 * log means the change is not undone. */
PureResult pure_list_insert(PureList *, size_t at, const PureCell *cells, PureUndo *);
/* An item into a list kept in order of a number field, where its key goes,
 * found and placed in one descent (docs/design/020): at says where (NULL:
 * not asked, so a DENSE list need not count it), exists whether an item had
 * the key (then nothing changes). Its change is logged and journaled as
 * pure_list_insert's. PURE_INVALID when the list is not such a one (search
 * it and insert then). */
PureResult pure_list_add(PureList *, const PureCell *cells, PureUndo *, size_t *at, bool *exists);
PureResult pure_list_remove(PureList *, size_t at, PureUndo *);
PureResult pure_list_set(PureList *, size_t at, unsigned field, PureCell value, PureUndo *);
PureCell pure_list_get(const PureList *, size_t at, unsigned field);
/* The run holding position at (false past the end), and the run after
 * run (false at the end): for reading item after item without finding each.
 * Valid until the list changes. */
bool pure_list_run(const PureList *, size_t at, PureRun *);
bool pure_list_next(const PureList *, PureRun *);
/* In a list ordered by field (a keyed list): the first position whose item's
 * field does not order below key (numbers and integers by value, texts by
 * bytes), and whether that item's field is key. */
size_t pure_list_seek(const PureList *, unsigned field, PureCell key, bool *found);
/* The first position whose item's field does not order below key, as
 * pure_list_seek's but without whether it is key (a slice's bound: a packed
 * list then reads its index alone). */
size_t pure_list_bound(const PureList *, unsigned field, PureCell key);
/* A stored list keyed by a number and searched by key at least an eighth of
 * its items' times since it last changed (4,096 items or more) is packed
 * (docs/design/022): its items in arrays, each field's in order, with an
 * index of its keys in buckets, which its copies share; a change makes it a
 * tree again first. Answers are the tree's. Called between events (no run of
 * the list is open): true when it packed the list. */
bool pure_list_settle(PureList *);
bool pure_list_packed(const PureList *);
/* The field a keyed list keeps its items in order of: when it is a number
 * field, seek by it reads each level's keys from one node (field -1, or a
 * text field: none). ALLOCATION leaves the list searched as if it had none. */
PureResult pure_list_keyed(PureList *, int field);
/* A list keyed by a number keeps its keys as a set too, beside its tree
 * (docs/design/020): pure_list_contains answers whether a key is there
 * without a search. Its changes and their undoing keep the set; a share of
 * it has none. For the lists an event searches most (its own). False when
 * it is not keyed by a number, is a copy, or memory runs out (it is
 * searched as before). */
bool pure_list_hashed(PureList *);
/* Whether key is there, by the set: false when the list keeps none (search it then). */
bool pure_list_contains(const PureList *, double key, bool *found);
/* The bytes it keeps beside its items for that. */
size_t pure_list_extra(const PureList *);
/* An event's list (empty, never shared, journaled or undone) may keep its
 * items in arrays rather than a tree (docs/design/021): in order (FLAT), or
 * at their keys when keyed by small whole numbers (DENSE), as the changes it
 * gets allow; a clear makes it FLAT again. Answers are the tree's. False
 * when the list cannot (it stays a tree). */
bool pure_list_arrays(PureList *);
/* What it keeps its items in now: 0 a tree, 1 FLAT arrays, 2 DENSE (for tests and counts). */
unsigned pure_list_form(const PureList *);
/* Field of the item whose key_field is key, in a list ordered by key_field
 * (seek, then get, as one: a DENSE list reads it at its key); false when no
 * item has key. */
bool pure_list_lookup(const PureList *, unsigned key_field, PureCell key, unsigned field, PureCell *cell);
/* The list's items ordered by field, as a keyed list keeps them: *out is NULL
 * when they already are, or a new list in that order with moved[position
 * before] = position after for every item. CONFLICT when two items have the
 * same key (nothing is made). */
PureResult pure_list_sorted(const PureList *, unsigned field, PureList **out, size_t *moved);
/* The stored form of items: each item's fields in order, a number as its
 * binary64 bits and an integer as its two's complement (8 bytes,
 * little-endian), a text as a u32le length and its bytes.
 * pure_list_size is the bytes of all the items so stored, and
 * pure_list_encode writes them to out. */
size_t pure_list_size(const PureList *);
void pure_list_encode(const PureList *, unsigned char *out);
/* The items from position *at on, as many whole ones as capacity holds,
 * into out: their bytes (0 at the end, or with *needed the bytes of the one
 * item that does not fit), *at moved past them. */
size_t pure_list_encode_part(const PureList *, size_t *at, unsigned char *out, size_t capacity, size_t *needed);
/* Append the items stored in bytes; each field is checked. */
PureResult pure_list_read(PureList *, const unsigned char *bytes, size_t size);
/* A stored list journals its changes (from pure_list_journal(list, true)
 * on): every insert, remove and set adds a record, a u8 kind (1 insert, 2
 * remove, 3 set) and the u32le position, then an insert's item or a set's
 * u8 field and cell in stored form. A change there is no room to record does
 * not happen. pure_list_changes are the records since pure_list_forget last
 * kept none; forgetting down to a length taken earlier drops the records of
 * changes undone since (an undo does not journal). pure_list_replay makes
 * the changes of records again, in order: a list read from its stored items
 * and given its journal is the list that wrote them. */
void pure_list_journal(PureList *, bool journaled);
PureSpan pure_list_changes(const PureList *);
void pure_list_forget(PureList *, size_t size);
PureResult pure_list_replay(PureList *, const unsigned char *bytes, size_t size);
/* Undo the changes logged after mark (a count taken earlier), newest first. */
void pure_undo_rollback(PureUndo *, size_t mark);
void pure_undo_commit(PureUndo *);
/* What the changes logged hold, in bytes (their entries and the cells kept). */
size_t pure_undo_size(const PureUndo *);
void pure_undo_free(PureUndo *);
#endif