/*-------------------------------------------------------------------------
 *
 * jsonb_gin.c
 *	 GIN support functions for jsonb
 *
 * Copyright (c) 2014-2015, PostgreSQL Global Development Group
 *
 *
 * IDENTIFICATION
 *	  src/backend/utils/adt/jsonb_gin.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/gin.h"
#include "access/hash.h"
#include "access/stratnum.h"
#include "catalog/pg_collation.h"
#include "catalog/pg_type.h"
#include "utils/builtins.h"
#include "utils/jsonb.h"

typedef struct PathHashStack
{
	uint32		hash;
	struct PathHashStack *parent;
} PathHashStack;

static Datum make_text_key(char flag, const char *str, int len);
static Datum make_scalar_key(const JsonbValue *scalarVal, bool is_key);

/*
 *
 * jsonb_ops GIN opclass support functions
 *
 */

Datum
gin_compare_jsonb(PG_FUNCTION_ARGS)
{
	text	   *arg1 = PG_GETARG_TEXT_PP(0);
	text	   *arg2 = PG_GETARG_TEXT_PP(1);
	int32		result;
	char	   *a1p,
			   *a2p;
	int			len1,
				len2;

	a1p = VARDATA_ANY(arg1);
	a2p = VARDATA_ANY(arg2);

	len1 = VARSIZE_ANY_EXHDR(arg1);
	len2 = VARSIZE_ANY_EXHDR(arg2);

	/* Compare text as bttextcmp does, but always using C collation */
	result = varstr_cmp(a1p, len1, a2p, len2, C_COLLATION_OID);

	PG_FREE_IF_COPY(arg1, 0);
	PG_FREE_IF_COPY(arg2, 1);

	PG_RETURN_INT32(result);
}

Datum
gin_extract_jsonb(PG_FUNCTION_ARGS)
{
	Jsonb	   *jb = (Jsonb *) PG_GETARG_JSONB(0);
	int32	   *nentries = (int32 *) PG_GETARG_POINTER(1);
	int			total = 2 * JB_ROOT_COUNT(jb);
	JsonbIterator *it;
	JsonbValue	v;
	JsonbIteratorToken r;
	int			i = 0;
	Datum	   *entries;

	/* If the root level is empty, we certainly have no keys */
	if (total == 0)
	{
		*nentries = 0;
		PG_RETURN_POINTER(NULL);
	}

	/* Otherwise, use 2 * root count as initial estimate of result size */
	entries = (Datum *) palloc(sizeof(Datum) * total);

	it = JsonbIteratorInit(&jb->root);

	while ((r = JsonbIteratorNext(&it, &v, false)) != WJB_DONE)
	{
		/* Since we recurse into the object, we might need more space */
		if (i >= total)
		{
			total *= 2;
			entries = (Datum *) repalloc(entries, sizeof(Datum) * total);
		}

		switch (r)
		{
			case WJB_KEY:
				entries[i++] = make_scalar_key(&v, true);
				break;
			case WJB_ELEM:
				/* Pretend string array elements are keys, see jsonb.h */
				entries[i++] = make_scalar_key(&v, (v.type == jbvString));
				break;
			case WJB_VALUE:
				entries[i++] = make_scalar_key(&v, false);
				break;
			default:
				/* we can ignore structural items */
				break;
		}
	}

	*nentries = i;

	PG_RETURN_POINTER(entries);
}

Datum
gin_extract_jsonb_query(PG_FUNCTION_ARGS)
{
	int32	   *nentries = (int32 *) PG_GETARG_POINTER(1);
	StrategyNumber strategy = PG_GETARG_UINT16(2);
	int32	   *searchMode = (int32 *) PG_GETARG_POINTER(6);
	Datum	   *entries;

	if (strategy == JsonbContainsStrategyNumber)
	{
		/* Query is a jsonb, so just apply gin_extract_jsonb... */
		entries = (Datum *)
			DatumGetPointer(DirectFunctionCall2(gin_extract_jsonb,
												PG_GETARG_DATUM(0),
												PointerGetDatum(nentries)));
		/* ...although "contains {}" requires a full index scan */
		if (*nentries == 0)
			*searchMode = GIN_SEARCH_MODE_ALL;
	}
	else if (strategy == JsonbExistsStrategyNumber)
	{
		/* Query is a text string, which we treat as a key */
		text	   *query = PG_GETARG_TEXT_PP(0);

		*nentries = 1;
		entries = (Datum *) palloc(sizeof(Datum));
		entries[0] = make_text_key(JGINFLAG_KEY,
								   VARDATA_ANY(query),
								   VARSIZE_ANY_EXHDR(query));
	}
	else if (strategy == JsonbExistsAnyStrategyNumber ||
			 strategy == JsonbExistsAllStrategyNumber)
	{
		/* Query is a text array; each element is treated as a key */
		ArrayType  *query = PG_GETARG_ARRAYTYPE_P(0);
		Datum	   *key_datums;
		bool	   *key_nulls;
		int			key_count;
		int			i,
					j;

		deconstruct_array(query,
						  TEXTOID, -1, false, 'i',
						  &key_datums, &key_nulls, &key_count);

		entries = (Datum *) palloc(sizeof(Datum) * key_count);

		for (i = 0, j = 0; i < key_count; i++)
		{
			/* Nulls in the array are ignored */
			if (key_nulls[i])
				continue;
			entries[j++] = make_text_key(JGINFLAG_KEY,
										 VARDATA_ANY(key_datums[i]),
										 VARSIZE_ANY_EXHDR(key_datums[i]));
		}

		*nentries = j;
		/* ExistsAll with no keys should match everything */
		if (j == 0 && strategy == JsonbExistsAllStrategyNumber)
			*searchMode = GIN_SEARCH_MODE_ALL;
	}
	else
	{
		elog(ERROR, "unrecognized strategy number: %d", strategy);
		entries = NULL;			/* keep compiler quiet */
	}

	PG_RETURN_POINTER(entries);
}

Datum
gin_consistent_jsonb(PG_FUNCTION_ARGS)
{
	bool	   *check = (bool *) PG_GETARG_POINTER(0);
	StrategyNumber strategy = PG_GETARG_UINT16(1);

	/* Jsonb	   *query = PG_GETARG_JSONB(2); */
	int32		nkeys = PG_GETARG_INT32(3);

	/* Pointer	   *extra_data = (Pointer *) PG_GETARG_POINTER(4); */
	bool	   *recheck = (bool *) PG_GETARG_POINTER(5);
	bool		res = true;
	int32		i;

	if (strategy == JsonbContainsStrategyNumber)
	{
		/*
		 * We must always recheck, since we can't tell from the index whether
		 * the positions of the matched items match the structure of the query
		 * object.  (Even if we could, we'd also have to worry about hashed
		 * keys and the index's failure to distinguish keys from string array
		 * elements.)  However, the tuple certainly doesn't match unless it
		 * contains all the query keys.
		 */
		*recheck = true;
		for (i = 0; i < nkeys; i++)
		{
			if (!check[i])
			{
				res = false;
				break;
			}
		}
	}
	else if (strategy == JsonbExistsStrategyNumber)
	{
		/*
		 * Although the key is certainly present in the index, we must recheck
		 * because (1) the key might be hashed, and (2) the index match might
		 * be for a key that's not at top level of the JSON object.  For (1),
		 * we could look at the query key to see if it's hashed and not
		 * recheck if not, but the index lacks enough info to tell about (2).
		 */
		*recheck = true;
		res = true;
	}
	else if (strategy == JsonbExistsAnyStrategyNumber)
	{
		/* As for plain exists, we must recheck */
		*recheck = true;
		res = true;
	}
	else if (strategy == JsonbExistsAllStrategyNumber)
	{
		/* As for plain exists, we must recheck */
		*recheck = true;
		/* ... but unless all the keys are present, we can say "false" */
		for (i = 0; i < nkeys; i++)
		{
			if (!check[i])
			{
				res = false;
				break;
			}
		}
	}
	else
		elog(ERROR, "unrecognized strategy number: %d", strategy);

	PG_RETURN_BOOL(res);
}

Datum
gin_triconsistent_jsonb(PG_FUNCTION_ARGS)
{
	GinTernaryValue *check = (GinTernaryValue *) PG_GETARG_POINTER(0);
	StrategyNumber strategy = PG_GETARG_UINT16(1);

	/* Jsonb	   *query = PG_GETARG_JSONB(2); */
	int32		nkeys = PG_GETARG_INT32(3);

	/* Pointer	   *extra_data = (Pointer *) PG_GETARG_POINTER(4); */
	GinTernaryValue res = GIN_MAYBE;
	int32		i;

	/*
	 * Note that we never return GIN_TRUE, only GIN_MAYBE or GIN_FALSE; this
	 * corresponds to always forcing recheck in the regular consistent
	 * function, for the reasons listed there.
	 */
	if (strategy == JsonbContainsStrategyNumber ||
		strategy == JsonbExistsAllStrategyNumber)
	{
		/* All extracted keys must be present */
		for (i = 0; i < nkeys; i++)
		{
			if (check[i] == GIN_FALSE)
			{
				res = GIN_FALSE;
				break;
			}
		}
	}
	else if (strategy == JsonbExistsStrategyNumber ||
			 strategy == JsonbExistsAnyStrategyNumber)
	{
		/* At least one extracted key must be present */
		res = GIN_FALSE;
		for (i = 0; i < nkeys; i++)
		{
			if (check[i] == GIN_TRUE ||
				check[i] == GIN_MAYBE)
			{
				res = GIN_MAYBE;
				break;
			}
		}
	}
	else
		elog(ERROR, "unrecognized strategy number: %d", strategy);

	PG_RETURN_GIN_TERNARY_VALUE(res);
}

/*
 *
 * jsonb_path_ops GIN opclass support functions
 *
 * In a jsonb_path_ops index, the GIN keys are uint32 hashes, one per JSON
 * value; but the JSON key(s) leading to each value are also included in its
 * hash computation.  This means we can only support containment queries,
 * but the index can distinguish, for example, {"foo": 42} from {"bar": 42}
 * since different hashes will be generated.
 *
 */

Datum
gin_extract_jsonb_path(PG_FUNCTION_ARGS)
{
	Jsonb	   *jb = PG_GETARG_JSONB(0);
	int32	   *nentries = (int32 *) PG_GETARG_POINTER(1);
	int			total = 2 * JB_ROOT_COUNT(jb);
	JsonbIterator *it;
	JsonbValue	v;
	JsonbIteratorToken r;
	PathHashStack tail;
	PathHashStack *stack;
	int			i = 0;
	Datum	   *entries;

	/* If the root level is empty, we certainly have no keys */
	if (total == 0)
	{
		*nentries = 0;
		PG_RETURN_POINTER(NULL);
	}

	/* Otherwise, use 2 * root count as initial estimate of result size */
	entries = (Datum *) palloc(sizeof(Datum) * total);

	/* We keep a stack of partial hashes corresponding to parent key levels */
	tail.parent = NULL;
	tail.hash = 0;
	stack = &tail;

	it = JsonbIteratorInit(&jb->root);

	while ((r = JsonbIteratorNext(&it, &v, false)) != WJB_DONE)
	{
		PathHashStack *parent;

		/* Since we recurse into the object, we might need more space */
		if (i >= total)
		{
			total *= 2;
			entries = (Datum *) repalloc(entries, sizeof(Datum) * total);
		}

		switch (r)
		{
			case WJB_BEGIN_ARRAY:
			case WJB_BEGIN_OBJECT:
				/* Push a stack level for this object */
				parent = stack;
				stack = (PathHashStack *) palloc(sizeof(PathHashStack));

				if (parent->parent)
				{
					/*
					 * We pass forward hashes from previous container nesting
					 * levels so that nested arrays with an outermost nested
					 * object will have element hashes mixed with the
					 * outermost key.  It's also somewhat useful to have
					 * nested objects' innermost values have hashes that are a
					 * function of not just their own key, but outer keys too.
					 *
					 * Nesting an array within another array will not alter
					 * innermost scalar element hash values, but that seems
					 * inconsequential.
					 */
					stack->hash = parent->hash;
				}
				else
				{
					/*
					 * At the outermost level, initialize hash with container
					 * type proxy value.  Note that this makes JB_FARRAY and
					 * JB_FOBJECT part of the on-disk representation, but they
					 * are that in the base jsonb object storage already.
					 */
					stack->hash = (r == WJB_BEGIN_ARRAY) ? JB_FARRAY : JB_FOBJECT;
				}
				stack->parent = parent;
				break;
			case WJB_KEY:
				/* initialize hash from parent */
				stack->hash = stack->parent->hash;
				/* and mix in this key */
				JsonbHashScalarValue(&v, &stack->hash);
				/* hash is now ready to incorporate the value */
				break;
			case WJB_ELEM:
				/* array elements use parent hash mixed with element's hash */
				stack->hash = stack->parent->hash;
				/* FALL THRU */
			case WJB_VALUE:
				/* mix the element or value's hash into the prepared hash */
				JsonbHashScalarValue(&v, &stack->hash);
				/* and emit an index entry */
				entries[i++] = UInt32GetDatum(stack->hash);
				/* Note: we assume we'll see KEY before another VALUE */
				break;
			case WJB_END_ARRAY:
			case WJB_END_OBJECT:
				/* Pop the stack */
				parent = stack->parent;
				pfree(stack);
				stack = parent;
				break;
			default:
				elog(ERROR, "invalid JsonbIteratorNext rc: %d", (int) r);
		}
	}

	*nentries = i;

	PG_RETURN_POINTER(entries);
}

Datum
gin_extract_jsonb_query_path(PG_FUNCTION_ARGS)
{
	int32	   *nentries = (int32 *) PG_GETARG_POINTER(1);
	StrategyNumber strategy = PG_GETARG_UINT16(2);
	int32	   *searchMode = (int32 *) PG_GETARG_POINTER(6);
	Datum	   *entries;

	if (strategy != JsonbContainsStrategyNumber)
		elog(ERROR, "unrecognized strategy number: %d", strategy);

	/* Query is a jsonb, so just apply gin_extract_jsonb_path ... */
	entries = (Datum *)
		DatumGetPointer(DirectFunctionCall2(gin_extract_jsonb_path,
											PG_GETARG_DATUM(0),
											PointerGetDatum(nentries)));

	/* ... although "contains {}" requires a full index scan */
	if (*nentries == 0)
		*searchMode = GIN_SEARCH_MODE_ALL;

	PG_RETURN_POINTER(entries);
}

Datum
gin_consistent_jsonb_path(PG_FUNCTION_ARGS)
{
	bool	   *check = (bool *) PG_GETARG_POINTER(0);
	StrategyNumber strategy = PG_GETARG_UINT16(1);

	/* Jsonb	   *query = PG_GETARG_JSONB(2); */
	int32		nkeys = PG_GETARG_INT32(3);

	/* Pointer	   *extra_data = (Pointer *) PG_GETARG_POINTER(4); */
	bool	   *recheck = (bool *) PG_GETARG_POINTER(5);
	bool		res = true;
	int32		i;

	if (strategy != JsonbContainsStrategyNumber)
		elog(ERROR, "unrecognized strategy number: %d", strategy);

	/*
	 * jsonb_path_ops is necessarily lossy, not only because of hash
	 * collisions but also because it doesn't preserve complete information
	 * about the structure of the JSON object.  Besides, there are some
	 * special rules around the containment of raw scalars in arrays that are
	 * not handled here.  So we must always recheck a match.  However, if not
	 * all of the keys are present, the tuple certainly doesn't match.
	 */
	*recheck = true;
	for (i = 0; i < nkeys; i++)
	{
		if (!check[i])
		{
			res = false;
			break;
		}
	}

	PG_RETURN_BOOL(res);
}

Datum
gin_triconsistent_jsonb_path(PG_FUNCTION_ARGS)
{
	GinTernaryValue *check = (GinTernaryValue *) PG_GETARG_POINTER(0);
	StrategyNumber strategy = PG_GETARG_UINT16(1);

	/* Jsonb	   *query = PG_GETARG_JSONB(2); */
	int32		nkeys = PG_GETARG_INT32(3);

	/* Pointer	   *extra_data = (Pointer *) PG_GETARG_POINTER(4); */
	GinTernaryValue res = GIN_MAYBE;
	int32		i;

	if (strategy != JsonbContainsStrategyNumber)
		elog(ERROR, "unrecognized strategy number: %d", strategy);

	/*
	 * Note that we never return GIN_TRUE, only GIN_MAYBE or GIN_FALSE; this
	 * corresponds to always forcing recheck in the regular consistent
	 * function, for the reasons listed there.
	 */
	for (i = 0; i < nkeys; i++)
	{
		if (check[i] == GIN_FALSE)
		{
			res = GIN_FALSE;
			break;
		}
	}

	PG_RETURN_GIN_TERNARY_VALUE(res);
}

/*
 * Construct a jsonb_ops GIN key from a flag byte and a textual representation
 * (which need not be null-terminated).  This function is responsible
 * for hashing overlength text representations; it will add the
 * JGINFLAG_HASHED bit to the flag value if it does that.
 */
static Datum
make_text_key(char flag, const char *str, int len)
{
	text	   *item;
	char		hashbuf[10];

	if (len > JGIN_MAXLENGTH)
	{
		uint32		hashval;

		hashval = DatumGetUInt32(hash_any((const unsigned char *) str, len));
		snprintf(hashbuf, sizeof(hashbuf), "%08x", hashval);
		str = hashbuf;
		len = 8;
		flag |= JGINFLAG_HASHED;
	}

	/*
	 * Now build the text Datum.  For simplicity we build a 4-byte-header
	 * varlena text Datum here, but we expect it will get converted to short
	 * header format when stored in the index.
	 */
	item = (text *) palloc(VARHDRSZ + len + 1);
	SET_VARSIZE(item, VARHDRSZ + len + 1);

	*VARDATA(item) = flag;

	memcpy(VARDATA(item) + 1, str, len);

	return PointerGetDatum(item);
}

/*
 * Create a textual representation of a JsonbValue that will serve as a GIN
 * key in a jsonb_ops index.  is_key is true if the JsonbValue is a key,
 * or if it is a string array element (since we pretend those are keys,
 * see jsonb.h).
 */
static Datum
make_scalar_key(const JsonbValue *scalarVal, bool is_key)
{
	Datum		item;
	char	   *cstr;

	switch (scalarVal->type)
	{
		case jbvNull:
			Assert(!is_key);
			item = make_text_key(JGINFLAG_NULL, "", 0);
			break;
		case jbvBool:
			Assert(!is_key);
			item = make_text_key(JGINFLAG_BOOL,
								 scalarVal->val.boolean ? "t" : "f", 1);
			break;
		case jbvNumeric:
			Assert(!is_key);

			/*
			 * A normalized textual representation, free of trailing zeroes,
			 * is required so that numerically equal values will produce equal
			 * strings.
			 *
			 * It isn't ideal that numerics are stored in a relatively bulky
			 * textual format.  However, it's a notationally convenient way of
			 * storing a "union" type in the GIN B-Tree, and indexing Jsonb
			 * strings takes precedence.
			 */
			cstr = numeric_normalize(scalarVal->val.numeric);
			item = make_text_key(JGINFLAG_NUM, cstr, strlen(cstr));
			pfree(cstr);
			break;
		case jbvString:
			item = make_text_key(is_key ? JGINFLAG_KEY : JGINFLAG_STR,
								 scalarVal->val.string.val,
								 scalarVal->val.string.len);
			break;
		default:
			elog(ERROR, "unrecognized jsonb scalar type: %d", scalarVal->type);
			item = 0;			/* keep compiler quiet */
			break;
	}

	return item;
}
