http-boot-server/bootserver/config/config.go

package config

import (
	"encoding/json"
	"errors"
	"fmt"
	"io/fs"
	"os"

	"github.com/sirupsen/logrus"
)

type ListeningMode int64

func (lm ListeningMode) String() string {
	mapping := map[ListeningMode]string{
		ModeNet:  "net",
		ModeUnix: "unix",
	}
	val := mapping[lm]
	return val
}

func listeningModeFromString(rawVal string) (ListeningMode, error) {
	mapping := map[string]ListeningMode{
		"unix": ModeUnix,
		"net":  ModeNet,
	}
	if typedVal, ok := mapping[rawVal]; !ok {
		return ModeNet, fmt.Errorf("invalid listening mode %s", rawVal)
	} else {
		return typedVal, nil
	}
}

const (
	ModeUnix ListeningMode = iota
	ModeNet
)

type jsonConf struct {
	Log struct {
		Level string `json:"level"`
	} `json:"log"`
	Storage struct {
		Path        string `json:"path"`
		TemplateDir string `json:"templatePath"`
		StaticDir   string `json:"staticPath"`
	} `json:"storage"`
	Server struct {
		Host     string `json:"host"`
		Port     int    `json:"port"`
		Mode     string `json:"mode"`
		SockPath string `json:"sock"`
	} `json:"server"`
	BootProvider struct {
		Iface      string `json:"interface"`
		Port       int    `json:"port"`
		McastGroup string `json:"multicast_group"`
		SrcAddr    string `json:"src_addr"`
	} `json:"boot_provider"`
}

type AppConfig struct {
	LogLevel      logrus.Level
	ServerMode    ListeningMode
	DataFilepath  string
	StaticDir     string
	Host          string
	Port          int
	SockPath      string
	UPDMcastGroup string
	UDPPort       int
	UDPIface      string
	UDPSrcAddr    string
}

func parseLevel(lvlStr string) logrus.Level {
	for _, lvl := range logrus.AllLevels {
		if lvl.String() == lvlStr {
			return lvl
		}
	}
	return logrus.InfoLevel
}

func (ac *AppConfig) UnmarshalJSON(data []byte) error {
	var jsonConf jsonConf
	if err := json.Unmarshal(data, &jsonConf); err != nil {
		return fmt.Errorf("failed to read JSON: %w", err)
	}
	ac.LogLevel = parseLevel(jsonConf.Log.Level)

	lm, err := listeningModeFromString(jsonConf.Server.Mode)
	if err != nil {
		return fmt.Errorf("failed to parse server listening mode: %w", err)
	}
	ac.ServerMode = lm
	ac.SockPath = jsonConf.Server.SockPath
	ac.Host = jsonConf.Server.Host
	ac.Port = jsonConf.Server.Port
	ac.UPDMcastGroup = jsonConf.BootProvider.McastGroup
	ac.UDPIface = jsonConf.BootProvider.Iface
	ac.UDPPort = jsonConf.BootProvider.Port
	ac.UDPSrcAddr = jsonConf.BootProvider.SrcAddr
	ac.DataFilepath = jsonConf.Storage.Path
	ac.StaticDir = jsonConf.Storage.StaticDir
	return nil
}

var defaultConfig AppConfig = AppConfig{
	LogLevel:      logrus.InfoLevel,
	ServerMode:    ModeNet,
	DataFilepath:  "boot_options.json",
	Host:          "0.0.0.0",
	Port:          5000,
	UPDMcastGroup: "ff02::abcd:1234",
	UDPPort:       42,
	UDPIface:      "eth0",
	StaticDir:     "./static",
}

func New(filepath string) (*AppConfig, error) {
	content, err := os.ReadFile(filepath)
	if err != nil {
		if errors.Is(err, fs.ErrNotExist) {
			conf := defaultConfig
			return &conf, nil
		}
		return nil, fmt.Errorf("failed to read config file %q: %w", filepath, err)
	}
	var conf AppConfig
	if err := json.Unmarshal(content, &conf); err != nil {
		return nil, fmt.Errorf("failed to parse config file: %w", err)
	}
	return &conf, nil
}