package convert

import (
	"regexp"
	"strings"

	"github.com/compose-spec/compose-go/types"
	"github.com/pkg/errors"
	apiv1 "k8s.io/api/core/v1"
)

var constraintEquals = regexp.MustCompile(`([\w\.]*)\W*(==|!=)\W*([\w\.]*)`)

const (
	kubernetesOs       = "beta.kubernetes.io/os"
	kubernetesArch     = "beta.kubernetes.io/arch"
	kubernetesHostname = "kubernetes.io/hostname"
)

// node.id	Node ID	node.id == 2ivku8v2gvtg4
// node.hostname	Node hostname	node.hostname != node-2
// node.role	Node role	node.role == manager
// node.labels	user defined node labels	node.labels.security == high
// engine.labels	Docker Engine's labels	engine.labels.operatingsystem == ubuntu 14.04
func toNodeAffinity(deploy *types.DeployConfig) (*apiv1.Affinity, error) {
	constraints := []string{}
	if deploy != nil && deploy.Placement.Constraints != nil {
		constraints = deploy.Placement.Constraints
	}
	requirements := []apiv1.NodeSelectorRequirement{}
	for _, constraint := range constraints {
		matches := constraintEquals.FindStringSubmatch(constraint)
		if len(matches) == 4 {
			key := matches[1]
			operator, err := toRequirementOperator(matches[2])
			if err != nil {
				return nil, err
			}
			value := matches[3]

			switch {
			case key == constraintOs:
				requirements = append(requirements, apiv1.NodeSelectorRequirement{
					Key:      kubernetesOs,
					Operator: operator,
					Values:   []string{value},
				})
			case key == constraintArch:
				requirements = append(requirements, apiv1.NodeSelectorRequirement{
					Key:      kubernetesArch,
					Operator: operator,
					Values:   []string{value},
				})
			case key == constraintHostname:
				requirements = append(requirements, apiv1.NodeSelectorRequirement{
					Key:      kubernetesHostname,
					Operator: operator,
					Values:   []string{value},
				})
			case strings.HasPrefix(key, constraintLabelPrefix):
				requirements = append(requirements, apiv1.NodeSelectorRequirement{
					Key:      strings.TrimPrefix(key, constraintLabelPrefix),
					Operator: operator,
					Values:   []string{value},
				})
			}
		}
	}

	if !hasRequirement(requirements, kubernetesOs) {
		requirements = append(requirements, apiv1.NodeSelectorRequirement{
			Key:      kubernetesOs,
			Operator: apiv1.NodeSelectorOpIn,
			Values:   []string{"linux"},
		})
	}
	if !hasRequirement(requirements, kubernetesArch) {
		requirements = append(requirements, apiv1.NodeSelectorRequirement{
			Key:      kubernetesArch,
			Operator: apiv1.NodeSelectorOpIn,
			Values:   []string{"amd64"},
		})
	}
	return &apiv1.Affinity{
		NodeAffinity: &apiv1.NodeAffinity{
			RequiredDuringSchedulingIgnoredDuringExecution: &apiv1.NodeSelector{
				NodeSelectorTerms: []apiv1.NodeSelectorTerm{
					{
						MatchExpressions: requirements,
					},
				},
			},
		},
	}, nil
}

const (
	constraintOs          = "node.platform.os"
	constraintArch        = "node.platform.arch"
	constraintHostname    = "node.hostname"
	constraintLabelPrefix = "node.labels."
)

func hasRequirement(requirements []apiv1.NodeSelectorRequirement, key string) bool {
	for _, r := range requirements {
		if r.Key == key {
			return true
		}
	}
	return false
}

func toRequirementOperator(sign string) (apiv1.NodeSelectorOperator, error) {
	switch sign {
	case "==":
		return apiv1.NodeSelectorOpIn, nil
	case "!=":
		return apiv1.NodeSelectorOpNotIn, nil
	case ">":
		return apiv1.NodeSelectorOpGt, nil
	case "<":
		return apiv1.NodeSelectorOpLt, nil
	default:
		return "", errors.Errorf("operator %s not supported", sign)
	}
}