/*
 * Copyright 2024 The OpenSSL Project Authors. All Rights Reserved.
 *
 * Licensed under the Apache License 2.0 (the "License").  You may not use
 * this file except in compliance with the License.  You can obtain a copy
 * in the file LICENSE in the source distribution or at
 * https://www.openssl.org/source/license.html
 */

#ifndef OPENSSL_HASHTABLE_H
#define OPENSSL_HASHTABLE_H
#pragma once

#include <stddef.h>
#include <stdint.h>
#include <openssl/e_os2.h>
#include <internal/rcu.h>
#include "crypto/context.h"

typedef struct ht_internal_st HT;

/*
 * Represents a key to a hashtable
 */
typedef struct ht_key_header_st {
    size_t keysize;
    uint8_t *keybuf;
} HT_KEY;

/*
 * Represents a value in the hash table
 */
typedef struct ht_value_st {
    void *value;
    uintptr_t *type_id;
    HT_KEY key;
} HT_VALUE;

/*
 * Represents a list of values filtered from a hash table
 */
typedef struct ht_value_list_st {
    size_t list_len;
    HT_VALUE **list;
} HT_VALUE_LIST;

/*
 * Hashtable configuration
 */
typedef struct ht_config_st {
    OSSL_LIB_CTX *ctx;
    void (*ht_free_fn)(HT_VALUE *obj);
    uint64_t (*ht_hash_fn)(uint8_t *key, size_t keylen);
    size_t init_neighborhoods;
    uint32_t collision_check;
    uint32_t lockless_reads;
} HT_CONFIG;

/*
 * Hashtable key rules
 * Any struct can be used to formulate a hash table key, as long as the
 * following rules
 * 1) The first element of the struct defining the key must be an HT_KEY
 * 2) All struct elements must have a compile time defined length
 * 3) Pointers can be used, but the value of the pointer, rather than
 *    the contents of the address it points to will be used to compute
 *    the hash
 * The key definition macros will assist with enforcing these rules
 */

/*
 * Starts the definition of a hash table key
 */
#define HT_START_KEY_DEFN(keyname) \
    typedef struct keyname##_st {  \
        HT_KEY key_header;         \
        struct {

/*
 * Ends a hash table key definitions
 */
#define HT_END_KEY_DEFN(keyname) \
    }                            \
    keyfields;                   \
    }                            \
    keyname;

/*
 * Defines a field in a hash table key
 */
#define HT_DEF_KEY_FIELD(name, type) type name;

/*
 * convenience macro to define a static char
 * array field in a hash table key
 */
#define HT_DEF_KEY_FIELD_CHAR_ARRAY(name, size) \
    HT_DEF_KEY_FIELD(name[size], char)

/*
 * Defines a uint8_t (blob) field in a hash table key
 */
#define HT_DEF_KEY_FIELD_UINT8T_ARRAY(name, size) \
    HT_DEF_KEY_FIELD(name[size], uint8_t)

/*
 * Initializes a key
 */
#define HT_INIT_KEY(key)                                                \
    do {                                                                \
        memset((key), 0, sizeof(*(key)));                               \
        (key)->key_header.keysize = (sizeof(*(key)) - sizeof(HT_KEY));  \
        (key)->key_header.keybuf = (((uint8_t *)key) + sizeof(HT_KEY)); \
    } while (0)

/*
 * Resets a hash table key to a known state
 */
#define HT_KEY_RESET(key) memset((key)->key_header.keybuf, 0, (key)->key_header.keysize)

/*
 * Sets a scalar field in a hash table key
 */
#define HT_SET_KEY_FIELD(key, member, value) (key)->keyfields.member = value;

/*
 * Sets a string field in a hash table key, preserving
 * null terminator
 */
#define HT_SET_KEY_STRING(key, member, value)                                             \
    do {                                                                                  \
        if ((value) != NULL)                                                              \
            strncpy((key)->keyfields.member, value, sizeof((key)->keyfields.member) - 1); \
    } while (0)

/*
 * This is the same as HT_SET_KEY_STRING, except that it uses
 * ossl_ht_strcase to make the value being passed case insensitive
 * This is useful for instances in which we want upper and lower case
 * key value to hash to the same entry
 */
#define HT_SET_KEY_STRING_CASE(key, member, value)                                            \
    do {                                                                                      \
        ossl_ht_strcase((key)->keyfields.member, value, sizeof((key)->keyfields.member) - 1); \
    } while (0)

/*
 * Sets a uint8_t (blob) field in a hash table key
 */
#define HT_SET_KEY_BLOB(key, member, value, len)         \
    do {                                                 \
        if (value != NULL)                               \
            memcpy((key)->keyfields.member, value, len); \
    } while (0)

/*
 * Converts a defined key type to an HT_KEY
 */
#define TO_HT_KEY(key) &(key)->key_header

/*
 * Converts an HT_KEY back to its defined
 * type
 */
#define FROM_HT_KEY(key, type) (type)(key)

/*
 * Implements the following type safe operations for a hash table
 * ossl_ht_NAME_TYPE_insert - insert a value to a hash table of type TYPE
 * ossl_ht_NAME_TYPE_get - gets a value of a specific type from the hash table
 * ossl_ht_NAME_TYPE_from_value - converts an HT_VALUE to its type
 * ossl_ht_NAME_TYPE_to_value - converts a TYPE to an HT_VALUE
 * ossl_ht_NAME_TYPE_type - boolean to detect if a value is of TYPE
 */
#define IMPLEMENT_HT_VALUE_TYPE_FNS(vtype, name, pfx)                          \
    static uintptr_t name##_##vtype##_id = 0;                                  \
    pfx ossl_unused int ossl_ht_##name##_##vtype##_insert(HT *h, HT_KEY *key,  \
        vtype *data,                                                           \
        vtype **olddata)                                                       \
    {                                                                          \
        HT_VALUE inval;                                                        \
        HT_VALUE *oval = NULL;                                                 \
        int rc;                                                                \
                                                                               \
        inval.value = data;                                                    \
        inval.type_id = &name##_##vtype##_id;                                  \
        rc = ossl_ht_insert(h, key, &inval, olddata == NULL ? NULL : &oval);   \
        if (oval != NULL)                                                      \
            *olddata = (vtype *)oval->value;                                   \
        return rc;                                                             \
    }                                                                          \
                                                                               \
    pfx ossl_unused vtype *ossl_ht_##name##_##vtype##_from_value(HT_VALUE *v)  \
    {                                                                          \
        uintptr_t *expect_type = &name##_##vtype##_id;                         \
        if (v == NULL)                                                         \
            return NULL;                                                       \
        if (v->type_id != expect_type)                                         \
            return NULL;                                                       \
        return (vtype *)v->value;                                              \
    }                                                                          \
                                                                               \
    pfx ossl_unused vtype *ossl_unused ossl_ht_##name##_##vtype##_get(HT *h,   \
        HT_KEY *key,                                                           \
        HT_VALUE **v)                                                          \
    {                                                                          \
        HT_VALUE *vv;                                                          \
        vv = ossl_ht_get(h, key);                                              \
        if (vv == NULL)                                                        \
            return NULL;                                                       \
        *v = ossl_rcu_deref(&vv);                                              \
        return ossl_ht_##name##_##vtype##_from_value(*v);                      \
    }                                                                          \
                                                                               \
    pfx ossl_unused HT_VALUE *ossl_ht_##name##_##vtype##_to_value(vtype *data, \
        HT_VALUE *v)                                                           \
    {                                                                          \
        v->type_id = &name##_##vtype##_id;                                     \
        v->value = data;                                                       \
        return v;                                                              \
    }                                                                          \
                                                                               \
    pfx ossl_unused int ossl_ht_##name##_##vtype##_type(HT_VALUE *h)           \
    {                                                                          \
        return h->type_id == &name##_##vtype##_id;                             \
    }

#define DECLARE_HT_VALUE_TYPE_FNS(vtype, name)                               \
    int ossl_ht_##name##_##vtype##_insert(HT *h, HT_KEY *key, vtype *data,   \
        vtype **olddata);                                                    \
    vtype *ossl_ht_##name##_##vtype##_from_value(HT_VALUE *v);               \
    vtype *ossl_unused ossl_ht_##name##_##vtype##_get(HT *h,                 \
        HT_KEY *key,                                                         \
        HT_VALUE **v);                                                       \
    HT_VALUE *ossl_ht_##name##_##vtype##_to_value(vtype *data, HT_VALUE *v); \
    int ossl_ht_##name##_##vtype##_type(HT_VALUE *h);

/*
 * Helper function to construct case insensitive keys
 */
static void ossl_unused ossl_ht_strcase(char *tgt, const char *src, int len)
{
    int i;
#if defined(CHARSET_EBCDIC) && !defined(CHARSET_EBCDIC_TEST)
    const long int case_adjust = ~0x40;
#else
    const long int case_adjust = ~0x20;
#endif

    if (src == NULL)
        return;

    for (i = 0; i < len && src[i] != '\0'; i++)
        tgt[i] = case_adjust & src[i];
}

/*
 * Create a new hashtable
 */
HT *ossl_ht_new(const HT_CONFIG *conf);

/*
 * Frees a hash table, potentially freeing all elements
 */
void ossl_ht_free(HT *htable);

/*
 * Lock the table for reading
 */
void ossl_ht_read_lock(HT *htable);

/*
 * Lock the table for writing
 */
void ossl_ht_write_lock(HT *htable);

/*
 * Read unlock
 */
void ossl_ht_read_unlock(HT *htable);

/*
 * Write unlock
 */
void ossl_ht_write_unlock(HT *htable);

/*
 * Empties a hash table, potentially freeing all elements
 */
int ossl_ht_flush(HT *htable);

/*
 * Inserts an element to a hash table, optionally returning
 * replaced data to caller
 * Returns 1 if the insert was successful, 0 on error
 */
int ossl_ht_insert(HT *htable, HT_KEY *key, HT_VALUE *data,
    HT_VALUE **olddata);

/*
 * Deletes a value from a hash table, based on key
 * Returns 1 if the key was removed, 0 if they key was not found
 */
int ossl_ht_delete(HT *htable, HT_KEY *key);

/*
 * Returns number of elements in the hash table
 */
size_t ossl_ht_count(HT *htable);

/*
 * Iterates over each element in the table.
 * aborts the loop when cb returns 0
 * Contents of elements in the list may be modified during
 * this traversal, assuming proper thread safety is observed while doing
 * so (holding the table write lock is sufficient).  However, elements of the
 * table may not be inserted or removed while iterating.
 */
void ossl_ht_foreach_until(HT *htable, int (*cb)(HT_VALUE *obj, void *arg),
    void *arg);
/*
 * Returns a list of elements in a hash table based on
 * filter function return value.  Returns NULL on error,
 * or an HT_VALUE_LIST object on success.  Note it is possible
 * That a list will be returned with 0 entries, if none were found.
 * The zero length list must still be freed via ossl_ht_value_list_free
 */
HT_VALUE_LIST *ossl_ht_filter(HT *htable, size_t max_len,
    int (*filter)(HT_VALUE *obj, void *arg),
    void *arg);
/*
 * Frees the list returned from ossl_ht_filter
 */
void ossl_ht_value_list_free(HT_VALUE_LIST *list);

/*
 * Fetches a value from the hash table, based
 * on key.  Returns NULL if the element was not found.
 */
HT_VALUE *ossl_ht_get(HT *htable, HT_KEY *key);

#endif