// Copyright 2019 The Prometheus 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.

//go:build linux
// +build linux

package sysfs

import (
	"os"
	"path/filepath"
	"strings"
)

const (
	notAffected = "not affected" // based on: https://www.kernel.org/doc/Documentation/ABI/testing/sysfs-devices-system-cpu
	vulnerable  = "vulnerable"
	mitigation  = "mitigation"
	unknown     = "unknown"
)

const (
	VulnerabilityStateNotAffected = iota
	VulnerabilityStateVulnerable
	VulnerabilityStateMitigation
	VulnerabilityStateUnknown
)

var (
	// VulnerabilityHumanEncoding allows mapping the vulnerability state (encoded as an int) onto a human friendly
	// string. It can be used by consumers of this library to expose to the user the state of the vulnerability.
	VulnerabilityHumanEncoding = map[int]string{
		VulnerabilityStateNotAffected: notAffected,
		VulnerabilityStateVulnerable:  vulnerable,
		VulnerabilityStateMitigation:  mitigation,
		VulnerabilityStateUnknown:     unknown,
	}
)

// CPUVulnerabilities retrieves a map of vulnerability names to their mitigations.
func (fs FS) CPUVulnerabilities() (map[string]*Vulnerability, error) {
	matchingFilepaths, err := filepath.Glob(fs.sys.Path("devices/system/cpu/vulnerabilities/*"))
	if err != nil {
		return nil, err
	}

	vulnerabilities := make(map[string]*Vulnerability, len(matchingFilepaths))
	for _, path := range matchingFilepaths {
		filename := filepath.Base(path)

		rawContent, err := os.ReadFile(path)
		if err != nil {
			return nil, err
		}

		v, err := parseVulnerability(filename, string(rawContent))
		if err != nil {
			return nil, err
		}

		vulnerabilities[filename] = v
	}

	return vulnerabilities, nil
}

// Vulnerability represents a single vulnerability extracted from /sys/devices/system/cpu/vulnerabilities/.
type Vulnerability struct {
	CodeName   string
	State      int
	Mitigation string
}

func parseVulnerability(name, rawContent string) (*Vulnerability, error) {
	v := &Vulnerability{CodeName: name}
	rawContent = strings.TrimSpace(rawContent)
	rawContentLower := strings.ToLower(rawContent)
	switch {
	case strings.HasPrefix(rawContentLower, notAffected):
		v.State = VulnerabilityStateNotAffected
	case strings.HasPrefix(rawContentLower, vulnerable):
		v.State = VulnerabilityStateVulnerable
		m := strings.Fields(rawContent)
		if len(m) > 1 {
			v.Mitigation = strings.Join(m[1:], " ")
		}
	case strings.HasPrefix(rawContentLower, mitigation):
		v.State = VulnerabilityStateMitigation
		m := strings.Fields(rawContent)
		if len(m) > 1 {
			v.Mitigation = strings.Join(m[1:], " ")
		}
	case strings.HasPrefix(rawContentLower, unknown):
		v.State = VulnerabilityStateUnknown
		m := strings.Fields(rawContent)
		if len(m) > 1 {
			v.Mitigation = strings.Join(m[1:], " ")
		}
	default:
		// Output the raw data obtained from the vulnerability, with state
		// unknown, rather than erroring out
		v.State = VulnerabilityStateUnknown
		v.Mitigation = rawContent
	}
	return v, nil
}