// Copyright 2023 EMQ Technologies Co., Ltd.
//
// 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 operator

import (
	"fmt"

	"github.com/lf-edge/ekuiper/internal/xsql"
	"github.com/lf-edge/ekuiper/pkg/api"
	"github.com/lf-edge/ekuiper/pkg/ast"
)

type WindowFuncOperator struct {
	WindowFuncFields ast.Fields
}

type windowFuncHandle interface {
	handleTuple(input xsql.TupleRow)
	handleCollection(input xsql.Collection)
}

type rowNumberFuncHandle struct {
	name string
}

func (rh *rowNumberFuncHandle) handleTuple(input xsql.TupleRow) {
	input.Set(rh.name, 1)
}

func (rh *rowNumberFuncHandle) handleCollection(input xsql.Collection) {
	index := 1
	input.RangeSet(func(i int, r xsql.Row) (bool, error) {
		r.Set(rh.name, index)
		index++
		return true, nil
	})
}

func (wf *WindowFuncOperator) Apply(_ api.StreamContext, data interface{}, _ *xsql.FunctionValuer, _ *xsql.AggregateFunctionValuer) interface{} {
	for _, windowFuncField := range wf.WindowFuncFields {
		name := windowFuncField.Name
		if windowFuncField.AName != "" {
			name = windowFuncField.AName
		}
		var funcName string
		switch c := windowFuncField.Expr.(type) {
		case *ast.Call:
			funcName = c.Name
		case *ast.FieldRef:
			funcName = c.AliasRef.Expression.(*ast.Call).Name
		}
		wh, err := getWindowFuncHandle(funcName, name)
		if err != nil {
			return err
		}
		switch input := data.(type) {
		case xsql.TupleRow:
			wh.handleTuple(input)
		case xsql.Collection:
			wh.handleCollection(input)
		}
	}
	return data
}

func getWindowFuncHandle(funcName, colName string) (windowFuncHandle, error) {
	switch funcName {
	case "row_number":
		return &rowNumberFuncHandle{name: colName}, nil
	}
	return nil, fmt.Errorf("")
}