// Copyright 2018 clair 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 nvd

import (
	"fmt"
	"strings"

	log "github.com/sirupsen/logrus"
)

type nvd struct {
	Entries []nvdEntry `json:"CVE_Items"`
}

type nvdEntry struct {
	CVE               nvdCVE    `json:"cve"`
	Impact            nvdImpact `json:"impact"`
	PublishedDateTime string    `json:"publishedDate"`
}

type nvdCVE struct {
	Metadata nvdCVEMetadata `json:"CVE_data_meta"`
}

type nvdCVEMetadata struct {
	CVEID string `json:"ID"`
}

type nvdImpact struct {
	BaseMetricV2 nvdBaseMetricV2 `json:"baseMetricV2"`
	BaseMetricV3 nvdBaseMetricV3 `json:"baseMetricV3"`
}

type nvdBaseMetricV2 struct {
	CVSSv2 nvdCVSSv2 `json:"cvssV2"`
}

type nvdCVSSv2 struct {
	Score            float64 `json:"baseScore"`
	AccessVector     string  `json:"accessVector"`
	AccessComplexity string  `json:"accessComplexity"`
	Authentication   string  `json:"authentication"`
	ConfImpact       string  `json:"confidentialityImpact"`
	IntegImpact      string  `json:"integrityImpact"`
	AvailImpact      string  `json:"availabilityImpact"`
}

type nvdBaseMetricV3 struct {
	CVSSv3              nvdCVSSv3 `json:"cvssV3"`
	ExploitabilityScore float64   `json:"exploitabilityScore"`
	ImpactScore         float64   `json:"impactScore"`
}

type nvdCVSSv3 struct {
	Score              float64 `json:"baseScore"`
	AttackVector       string  `json:"attackVector"`
	AttackComplexity   string  `json:"attackComplexity"`
	PrivilegesRequired string  `json:"privilegesRequired"`
	UserInteraction    string  `json:"userInteraction"`
	Scope              string  `json:"scope"`
	ConfImpact         string  `json:"confidentialityImpact"`
	IntegImpact        string  `json:"integrityImpact"`
	AvailImpact        string  `json:"availabilityImpact"`
}

var vectorValuesToLetters = map[string]string{
	"NETWORK":          "N",
	"ADJACENT_NETWORK": "A",
	"LOCAL":            "L",
	"HIGH":             "H",
	"MEDIUM":           "M",
	"LOW":              "L",
	"NONE":             "N",
	"SINGLE":           "S",
	"MULTIPLE":         "M",
	"PARTIAL":          "P",
	"COMPLETE":         "C",

	// CVSSv3 only
	"PHYSICAL":  "P",
	"REQUIRED":  "R",
	"CHANGED":   "C",
	"UNCHANGED": "U",
}

func (n nvdEntry) Metadata() *NVDMetadata {
	metadata := &NVDMetadata{
		CVSSv2: NVDmetadataCVSSv2{
			PublishedDateTime: n.PublishedDateTime,
			Vectors:           n.Impact.BaseMetricV2.CVSSv2.String(),
			Score:             n.Impact.BaseMetricV2.CVSSv2.Score,
		},
		CVSSv3: NVDmetadataCVSSv3{
			Vectors:             n.Impact.BaseMetricV3.CVSSv3.String(),
			Score:               n.Impact.BaseMetricV3.CVSSv3.Score,
			ExploitabilityScore: n.Impact.BaseMetricV3.ExploitabilityScore,
			ImpactScore:         n.Impact.BaseMetricV3.ImpactScore,
		},
	}

	if metadata.CVSSv2.Vectors == "" {
		return nil
	}

	return metadata
}

func (n nvdEntry) Name() string {
	return n.CVE.Metadata.CVEID
}

func (n nvdCVSSv2) String() string {
	var str string
	addVec(&str, "AV", n.AccessVector)
	addVec(&str, "AC", n.AccessComplexity)
	addVec(&str, "Au", n.Authentication)
	addVec(&str, "C", n.ConfImpact)
	addVec(&str, "I", n.IntegImpact)
	addVec(&str, "A", n.AvailImpact)
	str = strings.TrimSuffix(str, "/")
	return str
}

func (n nvdCVSSv3) String() string {
	var str string
	addVec(&str, "AV", n.AttackVector)
	addVec(&str, "AC", n.AttackComplexity)
	addVec(&str, "PR", n.PrivilegesRequired)
	addVec(&str, "UI", n.UserInteraction)
	addVec(&str, "S", n.Scope)
	addVec(&str, "C", n.ConfImpact)
	addVec(&str, "I", n.IntegImpact)
	addVec(&str, "A", n.AvailImpact)
	str = strings.TrimSuffix(str, "/")

	if len(str) > 0 {
		return fmt.Sprintf("CVSS:3.0/%s", str)
	}
	return str
}

func addVec(str *string, vec, val string) {
	if val != "" {
		if let, ok := vectorValuesToLetters[val]; ok {
			*str = fmt.Sprintf("%s%s:%s/", *str, vec, let)
		} else {
			log.WithFields(log.Fields{"value": val, "vector": vec}).Warning("unknown value for CVSS vector")
		}
	}
}