Do a large chunk of the move to go

This commit moves a huge chunk of the code to go. The TODO.md document
indicates what is left to be done.

internal/config/config.go

@@ -0,0 +1,153 @@
+// Package config implements reading and validating a WissKIDistillery configuration file.
+package config
+
+import (
+	"fmt"
+	"io"
+	"net/url"
+	"reflect"
+	"strings"
+
+	"github.com/pkg/errors"
+)
+
+// Config represents the configuration of a distillery instance
+type Config struct {
+	// Several docker-compose files are created to manage global services and the system itself.
+	// On top of this all real-system space will be created under this directory.
+	DeployRoot string `env:"DEPLOY_ROOT" default:"/var/www/deploy" validator:"is_valid_abspath"`
+
+	// Each created Drupal Instance corresponds to a single domain name.
+	// These domain names should either be a complete domain name or a sub-domain of a default domain.
+	// This setting configures the default domain-name to create subdomains of.
+	DefaultDomain string `env:"DEFAULT_DOMAIN" default:"localhost.kwarc.info" validator:"is_valid_domain"`
+
+	// By default, the default domain redirects to the distillery repository.
+	// If you want to change this, set an alternate domain name here.
+	SelfRedirect *url.URL `env:"SELF_REDIRECT" default:"" validator:"is_valid_https_url"`
+
+	// By default, only the 'self' domain above is caught.
+	// To catch additional domains, add them here (comma seperated)
+	SelfExtraDomains []string `env:"SELF_EXTRA_DOMAINS" default:"" validator:"is_valid_domains"`
+
+	// You can override individual URLS in the homepage
+	// Do this by adding URLs (without trailing '/'s) into a JSON file
+	SelfOverridesFile string `env:"SELF_OVERRIDES_FILE" default:"" validator:"is_valid_file"`
+
+	// The system can support setting up certificate(s) automatically.
+	// It can be enabled by setting an email for certbot certificates.
+	// This email address can be configured here.
+	CertbotEmail string `env:"CERTBOT_EMAIL" default:"" validator:"is_valid_email"`
+
+	// Maximum age for backup
+	MaxBackupAge int `env:"MAX_BACKUP_AGE" default:"" validator:"is_valid_number"`
+
+	// Each Drupal instance requires a corresponding system user, database users and databases.
+	// These are also set by the appropriate domain name.
+	// To differentiate them from other users of the system, these names can be prefixed.
+	// The prefix to use can be configured here.
+	// When changing these please consider that no system user may exist that has the same name as a mysql user.
+	// This is a MariaDB restriction.
+	MysqlUserPrefix     string `env:"MYSQL_USER_PREFIX" default:"mysql-factory-" validator:"is_valid_slug"`
+	MysqlDatabasePrefix string `env:"MYSQL_DATABASE_PREFIX" default:"mysql-factory-" validator:"is_valid_slug"`
+	GraphDBUserPrefix   string `env:"GRAPHDB_USER_PREFIX" default:"mysql-factory-" validator:"is_valid_slug"`
+	GraphDBRepoPrefix   string `env:"GRAPHDB_REPO_PREFIX" default:"mysql-factory-" validator:"is_valid_slug"`
+
+	// In addition to the filesystem the WissKI distillery requires a single SQL table.
+	// It uses this database to store a list of installed things.
+	DistilleryBookkeepingDatabase string `env:"DISTILLERY_BOOKKEEPING_DATABASE" default:"distillery" validator:"is_valid_slug"`
+	DistilleryBookkeepingTable    string `env:"DISTILLERY_BOOKKEEPING_TABLE" default:"distillery" validator:"is_valid_slug"`
+
+	// Various components use password-based-authentication.
+	// These passwords are generated automatically.
+	// This variable can be used to determine their length.
+	PasswordLength int `env:"PASSWORD_LENGTH" default:"64" validator:"is_valid_number"`
+
+	// A file to be used for global authorized_keys for the ssh server.
+	GlobalAuthorizedKeysFile string `env:"GLOBAL_AUTHORIZED_KEYS_FILE" default:"/distillery/authorized_keys" validator:"is_valid_file"`
+
+	// admin credentials for graphdb
+	TriplestoreAdminUser     string `env:"GRAPHDB_ADMIN_USER" default:"admin" validator:"is_nonempty"`
+	TriplestoreAdminPassword string `env:"GRAPHDB_ADMIN_PASSWORD" default:"" validator:"is_nonempty"`
+
+	// admin credentials for the Mysql database
+	MysqlAdminUser     string `env:"MYSQL_ADMIN_USER" default:"admin" validator:"is_nonempty"`
+	MysqlAdminPassword string `env:"MYSQL_ADMIN_PASSWORD" default:"admin" validator:"is_nonempty"`
+}
+
+func (config Config) String() string {
+	values := &strings.Builder{}
+
+	vConfig := reflect.ValueOf(config)
+	tConfig := vConfig.Type()
+
+	// iterate over the types
+	numValues := tConfig.NumField()
+	for i := 0; i < numValues; i++ {
+		tField := tConfig.Field(i)
+		vField := vConfig.FieldByName(tField.Name)
+
+		fmt.Fprintf(values, "%s=%v\n", tField.Tag.Get("env"), vField.Interface())
+	}
+
+	return values.String()
+}
+
+func (config *Config) Unmarshal(src io.Reader) error {
+	// read all the values!
+	values, err := ReadAll(src)
+	if err != nil {
+		return err
+	}
+
+	vConfig := reflect.ValueOf(config).Elem()
+	tConfig := vConfig.Type()
+
+	// iterate over the types
+	numValues := tConfig.NumField()
+	for i := 0; i < numValues; i++ {
+		tField := tConfig.Field(i)
+		vField := vConfig.FieldByName(tField.Name)
+
+		env := tField.Tag.Get("env")
+		dflt := tField.Tag.Get("default")
+		validator := tField.Tag.Get("validator")
+
+		// read the value with a default
+		value, ok := values[env]
+		if !ok || value == "" {
+			if dflt == "" {
+				continue
+			}
+			value = dflt
+		}
+
+		// use the validator
+		vFunc, ok := knownValidators[validator]
+		if vFunc == nil || !ok {
+			return errors.Errorf("Unable to read %q refers to unknown validator %s", env, validator)
+		}
+
+		// get the parsed value
+		checked, err := vFunc(value)
+		if err != nil {
+			return errors.Wrapf(err, "Unable to read %q: Validator %s", env, validator)
+		}
+
+		// set the value of the field
+		var errSet interface{}
+		func() {
+			defer func() {
+				errSet = recover()
+			}()
+			vField.Set(reflect.ValueOf(checked))
+		}()
+
+		// capture any error
+		if errSet != nil {
+			return errors.Errorf("Unable to parse %q: validator %s returned %q", tField.Name, validator, errSet)
+		}
+	}
+
+	return nil
+}