// Copyright 2025 Dolthub, Inc.
//
// 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.

package functions

import (
	"io"

	"github.com/dolthub/go-mysql-server/sql"

	"github.com/dolthub/doltgresql/server/functions/framework"
	pgtypes "github.com/dolthub/doltgresql/server/types"
)

// initGenerateSeries registers the functions to the catalog.
func initGenerateSubscripts() {
	framework.RegisterFunction(generate_subscripts)
}

// generate_series_int32_int32 represents the PostgreSQL function of the same name, taking the same parameters.
var generate_subscripts = framework.Function2{
	Name:       "generate_subscripts",
	Return:     pgtypes.RowTypeWithReturnType(pgtypes.Int32),
	Parameters: [2]*pgtypes.DoltgresType{pgtypes.AnyArray, pgtypes.Int32},
	Strict:     true,
	SRF:        true,
	Callable: func(ctx *sql.Context, t [3]*pgtypes.DoltgresType, val1, val2 any) (any, error) {
		arr := val1.([]any)
		dimension := val2.(int32)
		if dimension != 1 {
			return nil, sql.ErrUnsupportedFeature.New("generate_subscripts only supports 1-dimensional arrays")
		}

		// Int2vector (int16vector in doltgresql) and Oidvector are old postgres types that are primarily found in pg_catalog tables.
		// Unlike other array types, they are zero-indexed.
		start := 1
		if t[0] == pgtypes.Int16vector || t[0] == pgtypes.Oidvector {
			start = 0
		}

		var i = start
		return pgtypes.NewSetReturningFunctionRowIter(func(ctx *sql.Context) (sql.Row, error) {
			if i >= len(arr)+start {
				return nil, io.EOF
			}
			idx := i
			i++
			return sql.Row{int32(idx)}, nil
		}), nil
	},
}