/*
 * Copyright 2022 Bytes & Brains
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *	   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <postgres.h>			 // Datum, etc.
#include <fmgr.h>				 // PG_FUNCTION_ARGS, etc.
#include <funcapi.h>			 // Needed to return HeapTuple
#include <access/htup_details.h> // Needed to return HeapTuple
#include <utils/geo_decls.h>	 // making native points

#include <h3api.h> // Main H3 include
#include "extension.h"

PG_FUNCTION_INFO_V1(h3_cell_to_vertex);
PG_FUNCTION_INFO_V1(h3_cell_to_vertexes);
PG_FUNCTION_INFO_V1(h3_vertex_to_lat_lng);
PG_FUNCTION_INFO_V1(h3_is_valid_vertex);

/* Returns a single vertex for a given cell, as an H3 index */
Datum
h3_cell_to_vertex(PG_FUNCTION_ARGS)
{
	H3Index		vertex;
	H3Error		error;
	H3Index		cell = PG_GETARG_H3INDEX(0);
	int			vertexNum = PG_GETARG_INT32(1);

	error = cellToVertex(cell, vertexNum, &vertex);
	H3_ERROR(error, "cellToVertex");

	PG_RETURN_H3INDEX(vertex);
}

/* Returns all vertexes for a given cell, as H3 indexes */
Datum
h3_cell_to_vertexes(PG_FUNCTION_ARGS)
{
	/* stuff done only on the first call of the function */
	if (SRF_IS_FIRSTCALL())
	{
		int			maxSize;
		int			size;
		H3Index    *vertexes;
		H3Error		error;

		/* create a function context for cross-call persistence */
		FuncCallContext *funcctx = SRF_FIRSTCALL_INIT();

		/* switch to memory context appropriate for multiple function calls */
		MemoryContext oldcontext =
		MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);

		/* BEGIN One-time setup code */

		H3Index		cell = PG_GETARG_H3INDEX(0);

		maxSize = 6;
		size = maxSize * sizeof(H3Index);

		vertexes = palloc(size);
		error = cellToVertexes(cell, vertexes);
		H3_ERROR(error, "cellToVertexes");

		funcctx->user_fctx = vertexes;
		funcctx->max_calls = maxSize;

		/* END One-time setup code */

		MemoryContextSwitchTo(oldcontext);
	}

	SRF_RETURN_H3_INDEXES_FROM_USER_FCTX();
}

/* Get the geocoordinates of an H3 vertex */
Datum
h3_vertex_to_lat_lng(PG_FUNCTION_ARGS)
{
	H3Index		vertex = PG_GETARG_H3INDEX(0);

	H3Error		error;
	Point	   *point = palloc(sizeof(Point));
	LatLng		latlng;

	error = vertexToLatLng(vertex, &latlng);
	H3_ERROR(error, "vertexToLatLng");

	point->x = radsToDegs(latlng.lng);
	point->y = radsToDegs(latlng.lat);

	PG_RETURN_POINT_P(point);
}


/* Whether the input is a valid H3 vertex */
Datum
h3_is_valid_vertex(PG_FUNCTION_ARGS)
{
	H3Index		vertex = PG_GETARG_H3INDEX(0);
	bool		is_valid = isValidVertex(vertex);

	PG_RETURN_BOOL(is_valid);
}