/*
 * Copyright 2018 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 <math.h> // cos, sin, etc.
#include <assert.h>

#include <postgres.h>            // Datum, etc.
#include <fmgr.h>                // PG_FUNCTION_ARGS, etc.
#include <funcapi.h>             // Definitions for functions which return sets
#include <access/htup_details.h> // Needed to return HeapTuple
#include <utils/builtins.h>

#include <h3/h3api.h> // Main H3 include
#include "extension.h"

// should only be in ONE file
PG_MODULE_MAGIC;

static_assert(
    H3_VERSION_MAJOR == LIBH3_REQUIRED_MAJOR && H3_VERSION_MINOR >= LIBH3_REQUIRED_MINOR,
    "Installed H3 must be at least version 3.3.0"
);

/**
 * Return version number for this extension (not main h3 lib)
 */
PG_FUNCTION_INFO_V1(h3_get_extension_version);
Datum h3_get_extension_version(PG_FUNCTION_ARGS)
{
    PG_RETURN_TEXT_P(cstring_to_text(EXTVERSION));
}

/**
 * Set-Returning-Function assume user fctx contains indices
 * will skip missing (all zeros) indices
 */
Datum srf_return_h3_indexes_from_user_fctx(PG_FUNCTION_ARGS)
{
    FuncCallContext *funcctx = SRF_PERCALL_SETUP();
    int call_cntr = funcctx->call_cntr;
    int max_calls = funcctx->max_calls;

    H3Index *indices = (H3Index *)funcctx->user_fctx;

    // skip missing indices (all zeros)
    while (call_cntr < max_calls && !indices[call_cntr])
    {
        funcctx->call_cntr = ++call_cntr;
    };

    if (call_cntr < max_calls)
    {
        Datum result = PointerGetDatum(&indices[call_cntr]);
        SRF_RETURN_NEXT(funcctx, result);
    }
    else
    {
        SRF_RETURN_DONE(funcctx);
    }
}

/**
 * Returns hex/distance tuples from user_fctx
 * will skip missing (all zeros) indices
 */
Datum srf_return_h3_index_distances_from_user_fctx(PG_FUNCTION_ARGS)
{
    FuncCallContext *funcctx = SRF_PERCALL_SETUP();
    int call_cntr = funcctx->call_cntr;
    int max_calls = funcctx->max_calls;

    hexDistanceTuple *user_fctx = funcctx->user_fctx;
    H3Index *indices = user_fctx->indices;
    int *distances = user_fctx->distances;

    // skip missing indices (all zeros)
    while (!indices[call_cntr])
    {
        funcctx->call_cntr = ++call_cntr;
    };

    if (call_cntr < max_calls)
    {
        TupleDesc tuple_desc = funcctx->tuple_desc;
        Datum values[2];
        bool nulls[2] = {false};
        HeapTuple tuple;
        Datum result;

        values[0] = PointerGetDatum(&indices[call_cntr]);
        values[1] = Int32GetDatum(distances[call_cntr]);

        tuple = heap_form_tuple(tuple_desc, values, nulls);
        result = HeapTupleGetDatum(tuple);

        SRF_RETURN_NEXT(funcctx, result);
    }
    else
    {
        SRF_RETURN_DONE(funcctx);
    }
}