/*
Copyright 2015 The Kubernetes Authors.

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 net

import (
	"fmt"
	"strconv"
	"strings"
)

// PortRange represents a range of TCP/UDP ports.  To represent a single port,
// set Size to 1.
type PortRange struct {
	Base int
	Size int
}

// Contains tests whether a given port falls within the PortRange.
func (pr *PortRange) Contains(p int) bool {
	return (p >= pr.Base) && ((p - pr.Base) < pr.Size)
}

// String converts the PortRange to a string representation, which can be
// parsed by PortRange.Set or ParsePortRange.
func (pr PortRange) String() string {
	if pr.Size == 0 {
		return ""
	}
	return fmt.Sprintf("%d-%d", pr.Base, pr.Base+pr.Size-1)
}

// Set parses a string of the form "value", "min-max", or "min+offset", inclusive at both ends, and
// sets the PortRange from it.  This is part of the flag.Value and pflag.Value
// interfaces.
func (pr *PortRange) Set(value string) error {
	const (
		SinglePortNotation = 1 << iota
		HyphenNotation
		PlusNotation
	)

	value = strings.TrimSpace(value)
	hyphenIndex := strings.Index(value, "-")
	plusIndex := strings.Index(value, "+")

	if value == "" {
		pr.Base = 0
		pr.Size = 0
		return nil
	}

	var err error
	var low, high int
	var notation int

	if plusIndex == -1 && hyphenIndex == -1 {
		notation |= SinglePortNotation
	}
	if hyphenIndex != -1 {
		notation |= HyphenNotation
	}
	if plusIndex != -1 {
		notation |= PlusNotation
	}

	switch notation {
	case SinglePortNotation:
		var port int
		port, err = strconv.Atoi(value)
		if err != nil {
			return err
		}
		low = port
		high = port
	case HyphenNotation:
		low, err = strconv.Atoi(value[:hyphenIndex])
		if err != nil {
			return err
		}
		high, err = strconv.Atoi(value[hyphenIndex+1:])
		if err != nil {
			return err
		}
	case PlusNotation:
		var offset int
		low, err = strconv.Atoi(value[:plusIndex])
		if err != nil {
			return err
		}
		offset, err = strconv.Atoi(value[plusIndex+1:])
		if err != nil {
			return err
		}
		high = low + offset
	default:
		return fmt.Errorf("unable to parse port range: %s", value)
	}

	if low > 65535 || high > 65535 {
		return fmt.Errorf("the port range cannot be greater than 65535: %s", value)
	}

	if high < low {
		return fmt.Errorf("end port cannot be less than start port: %s", value)
	}

	pr.Base = low
	pr.Size = 1 + high - low
	return nil
}

// Type returns a descriptive string about this type.  This is part of the
// pflag.Value interface.
func (*PortRange) Type() string {
	return "portRange"
}

// ParsePortRange parses a string of the form "min-max", inclusive at both
// ends, and initializs a new PortRange from it.
func ParsePortRange(value string) (*PortRange, error) {
	pr := &PortRange{}
	err := pr.Set(value)
	if err != nil {
		return nil, err
	}
	return pr, nil
}

func ParsePortRangeOrDie(value string) *PortRange {
	pr, err := ParsePortRange(value)
	if err != nil {
		panic(fmt.Sprintf("couldn't parse port range %q: %v", value, err))
	}
	return pr
}