// Copyright 2017 Baliance. All rights reserved.
//
// Use of this source code is governed by the terms of the Affero GNU General
// Public License version 3.0 as published by the Free Software Foundation and
// appearing in the file LICENSE included in the packaging of this file. A
// commercial license can be purchased by contacting sales@baliance.com.

package formula

import (
	"fmt"
	"math"
)

// BinOpType is the binary operation operator type
//go:generate stringer -type=BinOpType
type BinOpType byte

// Operator type constants
const (
	BinOpTypeUnknown BinOpType = iota
	BinOpTypePlus
	BinOpTypeMinus
	BinOpTypeMult
	BinOpTypeDiv
	BinOpTypeExp
	BinOpTypeLT
	BinOpTypeGT
	BinOpTypeEQ
	BinOpTypeLEQ
	BinOpTypeGEQ
	BinOpTypeNE
	BinOpTypeConcat // '&' in Excel
)

// BinaryExpr is a binary expression.
type BinaryExpr struct {
	lhs, rhs Expression
	op       BinOpType
}

// NewBinaryExpr constructs a new binary expression with a given operator.
func NewBinaryExpr(lhs Expression, op BinOpType, rhs Expression) Expression {
	return BinaryExpr{lhs, rhs, op}
}

// Eval evaluates the binary expression using the context given.
func (b BinaryExpr) Eval(ctx Context, ev Evaluator) Result {
	lhs := b.lhs.Eval(ctx, ev)
	rhs := b.rhs.Eval(ctx, ev)

	// peel off array/list ops first
	if lhs.Type == rhs.Type {
		if lhs.Type == ResultTypeArray {
			if !sameDim(lhs.ValueArray, rhs.ValueArray) {
				return MakeErrorResult("lhs/rhs should have same dimensions")
			}
			return arrayOp(b.op, lhs.ValueArray, rhs.ValueArray)
		} else if lhs.Type == ResultTypeList {
			if len(lhs.ValueList) != len(rhs.ValueList) {
				return MakeErrorResult("lhs/rhs should have same dimensions")
			}
			return listOp(b.op, lhs.ValueList, rhs.ValueList)
		}

	}

	// TODO: check for and add support for binary operators on boolean values
	switch b.op {
	case BinOpTypePlus:
		if lhs.Type == rhs.Type {
			if lhs.Type == ResultTypeNumber {
				return MakeNumberResult(lhs.ValueNumber + rhs.ValueNumber)
			}
		}
	case BinOpTypeMinus:
		if lhs.Type == rhs.Type {
			if lhs.Type == ResultTypeNumber {
				return MakeNumberResult(lhs.ValueNumber - rhs.ValueNumber)
			}
		}
	case BinOpTypeMult:
		if lhs.Type == rhs.Type {
			if lhs.Type == ResultTypeNumber {
				return MakeNumberResult(lhs.ValueNumber * rhs.ValueNumber)
			}
		}
	case BinOpTypeDiv:
		if lhs.Type == rhs.Type {
			if lhs.Type == ResultTypeNumber {
				if rhs.ValueNumber == 0 {
					return MakeErrorResultType(ErrorTypeDivideByZero, "divide by zero")
				}
				return MakeNumberResult(lhs.ValueNumber / rhs.ValueNumber)
			}
		}
	case BinOpTypeExp:
		if lhs.Type == rhs.Type {
			if lhs.Type == ResultTypeNumber {
				return MakeNumberResult(math.Pow(lhs.ValueNumber, rhs.ValueNumber))
			}
		}
	case BinOpTypeLT:
		if lhs.Type == rhs.Type {
			if lhs.Type == ResultTypeNumber {
				return MakeBoolResult(lhs.ValueNumber < rhs.ValueNumber)
			}
		}
	case BinOpTypeGT:
		if lhs.Type == rhs.Type {
			if lhs.Type == ResultTypeNumber {
				return MakeBoolResult(lhs.ValueNumber > rhs.ValueNumber)
			}
		}
	case BinOpTypeEQ:
		if lhs.Type == rhs.Type {
			if lhs.Type == ResultTypeNumber {
				// TODO: see what Excel does regarding floating point comparison
				return MakeBoolResult(lhs.ValueNumber == rhs.ValueNumber)
			}
		}
	case BinOpTypeNE:
		if lhs.Type == rhs.Type {
			if lhs.Type == ResultTypeNumber {
				return MakeBoolResult(lhs.ValueNumber != rhs.ValueNumber)
			}
		}
	case BinOpTypeLEQ:
		if lhs.Type == rhs.Type {
			if lhs.Type == ResultTypeNumber {
				return MakeBoolResult(lhs.ValueNumber <= rhs.ValueNumber)
			}
		}
	case BinOpTypeGEQ:
		if lhs.Type == rhs.Type {
			if lhs.Type == ResultTypeNumber {
				return MakeBoolResult(lhs.ValueNumber >= rhs.ValueNumber)
			}
		}
	case BinOpTypeConcat:
		return MakeStringResult(lhs.Value() + rhs.Value())
	}

	return MakeErrorResult("unsupported binary op")
}

func (b BinaryExpr) Reference(ctx Context, ev Evaluator) Reference {
	return ReferenceInvalid
}

// sameDim returns true if the arrays have the same dimensions.
func sameDim(lhs, rhs [][]Result) bool {
	if len(lhs) != len(rhs) {
		return false
	}
	for i := range lhs {
		if len(lhs[i]) != len(rhs[i]) {
			return false
		}
	}
	return true
}

func arrayOp(op BinOpType, lhs, rhs [][]Result) Result {
	// we can assume the arrays are the same size here
	res := [][]Result{}
	for i := range lhs {
		lst := listOp(op, lhs[i], rhs[i])
		if lst.Type == ResultTypeError {
			return lst
		}
		res = append(res, lst.ValueList)
	}
	return MakeArrayResult(res)
}

func listOp(op BinOpType, lhs, rhs []Result) Result {
	res := []Result{}
	// we can assume the arrays are the same size here
	for i := range lhs {
		l := lhs[i].AsNumber()
		r := rhs[i].AsNumber()
		if l.Type != ResultTypeNumber || r.Type != ResultTypeNumber {
			return MakeErrorResult("non-nunmeric value in binary operation")
		}
		switch op {
		case BinOpTypePlus:
			res = append(res, MakeNumberResult(l.ValueNumber+r.ValueNumber))
		case BinOpTypeMinus:
			res = append(res, MakeNumberResult(l.ValueNumber-r.ValueNumber))
		case BinOpTypeMult:
			res = append(res, MakeNumberResult(l.ValueNumber*r.ValueNumber))
		case BinOpTypeDiv:
			if r.ValueNumber == 0 {
				return MakeErrorResultType(ErrorTypeDivideByZero, "")
			}
			res = append(res, MakeNumberResult(l.ValueNumber/r.ValueNumber))
		case BinOpTypeExp:
			res = append(res, MakeNumberResult(math.Pow(l.ValueNumber, r.ValueNumber)))
		case BinOpTypeLT:
			res = append(res, MakeBoolResult(l.ValueNumber < r.ValueNumber))
		case BinOpTypeGT:
			res = append(res, MakeBoolResult(l.ValueNumber > r.ValueNumber))
		case BinOpTypeEQ:
			res = append(res, MakeBoolResult(l.ValueNumber == r.ValueNumber))
		case BinOpTypeLEQ:
			res = append(res, MakeBoolResult(l.ValueNumber <= r.ValueNumber))
		case BinOpTypeGEQ:
			res = append(res, MakeBoolResult(l.ValueNumber >= r.ValueNumber))
		case BinOpTypeNE:
			res = append(res, MakeBoolResult(l.ValueNumber != r.ValueNumber))
		// TODO: support concat here
		// case BinOpTypeConcat:
		default:
			return MakeErrorResult(fmt.Sprintf("unsupported list binary op %s", op))
		}
	}
	return MakeListResult(res)
}