/*-------------------------------------------------------------------------
 * Copyright (c) Microsoft Corporation.  All rights reserved.
 *
 * include/bson/bson_project.h
 *
 * Common declarations of functions for handling bson projection.
 *
 *-------------------------------------------------------------------------
 */

#ifndef BSON_PROJECT_H
#define BSON_PROJECT_H


#include "io/bson_core.h"
#include "aggregation/bson_projection_tree.h"
#include "operators/bson_expression.h"

extern PGDLLIMPORT const StringView IdFieldStringView;

/* Forward declare the pointer type ( no need to expose the struct layout) */
typedef struct BsonProjectionQueryState BsonProjectionQueryState;
typedef struct BsonProjectDocumentFunctions BsonProjectDocumentFunctions;

typedef struct ProjectDocumentState ProjectDocumentState;

typedef bool (*TryHandleIntermediateArrayNodeFunc)(const BsonIntermediatePathNode *node,
												   ProjectDocumentState *state,
												   bson_iter_t *sourceValue);

typedef void *(*InitializePendingProjectionStateFunc)(uint32_t totalPendingProjections);

typedef void (*WritePendingProjectionFunc)(pgbson_writer *writer,
										   void *pendingProjections);

typedef bool (*SkipUnresolvedIntermediateFieldsFunc)(const
													 BsonIntermediatePathNode *tree);


/*
 * Context for Projection
 */
typedef struct BsonProjectionContext
{
	/* Whether or not Id should be forcily projected */
	bool forceProjectId;

	/* Whether or not inclusion and exclusion is allowed simultaneously */
	bool allowInclusionExclusion;

	/* Iterator on path spec */
	bson_iter_t *pathSpecIter;

	/* Query spec for positional projection. It all cases this is null when `isFindProjection` is false */
	pgbson *querySpec;

	/* The variable spec for let scenarios if applicable */
	const pgbson *variableSpec;

	/* Collation string for comparison, if applicable */
	const char *collationString;
} BsonProjectionContext;

/*
 * Common function pointers hooks uses while project wrting stage
 */
typedef struct BsonProjectDocumentFunctions
{
	/*
	 * Used to handle the intermediate array fields in a projection
	 * e.g. $ projection use the first intermediate array field and applies
	 * the query to find a matching index and projects it
	 */
	TryHandleIntermediateArrayNodeFunc tryMoveArrayIteratorFunc;

	/*
	 * Used in case when some of the projection needs to be written
	 * at the end, this would initialize the state needed to meet the requirement
	 * of such cases
	 * e.g. $elemMatch Projection
	 */
	InitializePendingProjectionStateFunc initializePendingProjectionFunc;

	/*
	 * Used to write the pendingProjection to the main writer at the end
	 */
	WritePendingProjectionFunc writePendingProjectionFunc;
} BsonProjectDocumentFunctions;

/* Per document projection state */
typedef struct ProjectDocumentState
{
	/* Matched document for projection */
	pgbson *parentDocument;

	/* variable context for the current projection. */
	const ExpressionVariableContext *variableContext;

	/*
	 * Whether or not for a $ projection the query is used to evaluate the matching index
	 * This can only be used once by the outermost array for a positional path spec
	 * e.g. {a.b.c.d.$: 1} => If `b` & `d` are both array fields then positional projeciton
	 * is applied on `b`
	 */
	bool isPositionalAlreadyEvaluated;

	/* Whether the projection is exclusion projection */
	bool hasExclusion;

	/* Optional: Bson Project Document stage function hooks */
	BsonProjectDocumentFunctions projectDocumentFuncs;

	/*
	 * Pending projections (e.g. $elemMatch) that are only valid at the top-level
	 * document. Must be hidden (set to NULL) before recursing into nested documents
	 * to prevent inner calls from prematurely flushing and freeing the pending writers.
	 */
	void *topLevelPendingProjectionState;

	/* For projections that needs to avoid projecting for all elements of an intermediate array
	 * e.g. $geoNear updates the document and for a conflicting intermediate array path it just overrides
	 * the complete array and makes it a single nested object
	 *
	 * Document => {a : {b: [{c: 10}, {c: 20}]]}}
	 * Project => { a.b.c: 100 }
	 * Result => { a: {b: {c: 100} }
	 */
	bool skipIntermediateArrayFields;
} ProjectDocumentState;


/*
 * Cached state for ReplaceRoot and Redact.
 * This is an alias for BsonExpressionState which has the same structure.
 */
typedef BsonExpressionState BsonReplaceRootRedactState;


const BsonProjectionQueryState * GetProjectionStateForBsonProject(
	bson_iter_t *projectionSpecIter, bool forceProjectId,
	bool
	allowInclusionExclusion,
	const pgbson *
	variableSpec);

const BsonProjectionQueryState * GetProjectionStateForBsonAddFields(
	bson_iter_t *projectionSpecIter, const bson_value_t *variableSpec);
const BsonProjectionQueryState * GetProjectionStateForBsonUnset(const bson_value_t *
																unsetValue,
																bool forceProjectId);
void GetBsonValueForReplaceRoot(bson_iter_t *replaceRootIterator, bson_value_t *value);

void ValidateReplaceRootElement(const bson_value_t *value);
void PopulateReplaceRootExpressionDataFromSpec(BsonReplaceRootRedactState *state,
											   const bson_value_t *pathSpec,
											   pgbson *variableSpec,
											   const char *collationString);


void BuildRedactState(BsonReplaceRootRedactState *redactState, const
					  bson_value_t *redactValue, pgbson *variableSpec, const
					  char *collationString);

pgbson * ProjectDocumentWithState(pgbson *sourceDocument,
								  const BsonProjectionQueryState *state);
pgbson * ProjectReplaceRootDocument(pgbson *document,
									const AggregationExpressionData *replaceRootExpression,
									const ExpressionVariableContext *variableContext,
									bool forceProjectId);

/* projection writer functions */
void TraverseObjectAndAppendToWriter(bson_iter_t *parentIterator,
									 const BsonIntermediatePathNode *pathSpecTree,
									 pgbson_writer *writer,
									 bool projectNonMatchingFields,
									 ProjectDocumentState *projectDocState,
									 bool isInNestedArray);


bool TryInlineProjection(Node *currentExpr, Oid functionOid, const
						 bson_value_t *projectValue);
#endif
