sprechstunden-go/config/config.go

package config

import (
	"encoding/json"
	"fmt"
	"html/template"
	"io/ioutil"
	"log"
)

type Config struct {
	Server struct {
		ListenAddress string
		ListenPort    int
		Protocol      string
		Domain        string
	}
	Date struct {
		MinuteGranularity int
	}
	Request struct {
		SecretLength int
	}
	Mailer struct {
		Type         string
		FromAddress  string
		FromName     template.HTML
		SmtpHost     string
		SmtpPort     int
		SmtpUseAuth  bool
		SmtpIdentity string
		SmtpPassword string
	}
	SQL struct {
		Type          string
		SQLiteFile    string
		MysqlUser     string
		MysqlPassword string
		MysqlHost     string
		MysqlPort     int
		MysqlDatabase string
	}
	Tutor struct {
		MailSuffix string
	}
}

// ReadConfigFile takes a file path as an argument and attempts to
// unmarshal the content of the file into a struct containing a
// configuration.
func ReadConfigFile(filename string, conf *Config) error {
	configData, err := ioutil.ReadFile(filename)
	if err != nil {
		err = fmt.Errorf("Error reading config file: %w", err)
		log.Println(err.Error())
		return err
	}
	err = json.Unmarshal(configData, conf)
	if err != nil {
		err = fmt.Errorf("Error parsing config file as json: %w", err)
		log.Println(err.Error())
		return err
	}
	return validateConfig(conf)
}

// Checks config for sane values (e.g. correct port range or database type).
func validateConfig(conf *Config) error {
	var err error
	if !(conf.Server.ListenPort >= 1 && conf.Server.ListenPort <= 65535) {
		err = fmt.Errorf("Validating config: Server port must be between 1 and 65535, but is %d.", conf.Server.ListenPort)
		log.Println(err.Error())
	}
	if !(conf.Server.Protocol == "http" || conf.Server.Protocol == "https") {
		err = fmt.Errorf("Validating config: Server protocol must be 'http' or 'https', but is '%s'.", conf.Server.Protocol)
		log.Println(err.Error())
	}
	if !(conf.Date.MinuteGranularity >= 1 && conf.Date.MinuteGranularity <= 60) {
		err = fmt.Errorf("Validating config: Minute granularity must be between 1 and 60, but is %d.", conf.Date.MinuteGranularity)
		log.Println(err.Error())
	}
	if !(conf.Request.SecretLength >= 5 && conf.Request.SecretLength <= 50) {
		err = fmt.Errorf("Validating config: Requests' secret length must be between 5 and 50, but is %d.", conf.Request.SecretLength)
		log.Println(err.Error())
	}
	if !(conf.Mailer.Type == "Stdout" || conf.Mailer.Type == "Smtp") {
		err = fmt.Errorf("Validating config: Mailer type must be 'Stdout' or 'Smtp', but is '%s'.", conf.Mailer.Type)
		log.Println(err.Error())
	}
	if !(conf.SQL.Type == "SQLite" || conf.SQL.Type == "Mysql") {
		err = fmt.Errorf("Validating config: SQL type must be 'SQLite' or 'Mysql', but is '%s'.", conf.SQL.Type)
		log.Println(err.Error())
	}
	return err

}