feat(embed): make authelia embedable (#8841)

This adds a highly experimental option for developers looking to embed Authelia within another go binary.

Closes #5803

Signed-off-by: James Elliott <james-d-elliott@users.noreply.github.com>

1 files changed, 71 insertions, 0 deletions

diff --git a/experimental/embed/config.go b/experimental/embed/config.go
new file mode 100644
index 000000000..81d21463b
--- /dev/null
+++ b/experimental/embed/config.go
@@ -0,0 +1,71 @@
+package embed
+
+import (
+	"fmt"
+
+	"github.com/authelia/authelia/v4/internal/configuration"
+	"github.com/authelia/authelia/v4/internal/configuration/schema"
+	"github.com/authelia/authelia/v4/internal/configuration/validator"
+)
+
+// NewConfiguration builds a new configuration given a list of paths and filters. The filters can either be nil or
+// generated using NewNamedConfigFileFilters. This function essentially operates the same as Authelia does normally in
+// configuration steps.
+func NewConfiguration(paths []string, filters []configuration.BytesFilter) (keys []string, config *schema.Configuration, val *schema.StructValidator, err error) {
+	sources := configuration.NewDefaultSourcesWithDefaults(
+		paths,
+		filters,
+		configuration.DefaultEnvPrefix,
+		configuration.DefaultEnvDelimiter,
+		[]configuration.Source{configuration.NewMapSource(configuration.Defaults())})
+
+	val = schema.NewStructValidator()
+
+	var definitions *schema.Definitions
+
+	if definitions, err = configuration.LoadDefinitions(val, sources...); err != nil {
+		return nil, nil, nil, err
+	}
+
+	config = &schema.Configuration{}
+
+	if keys, err = configuration.LoadAdvanced(
+		val,
+		"",
+		config,
+		definitions,
+		sources...); err != nil {
+		return nil, nil, nil, err
+	}
+
+	return keys, config, val, nil
+}
+
+// ValidateConfigurationAndKeys performs all configuration validation steps. The provided *schema.StructValidator should
+// at minimum be checked for errors before continuing.
+func ValidateConfigurationAndKeys(config *schema.Configuration, keys []string, val *schema.StructValidator) {
+	ValidateConfigurationKeys(keys, val)
+	ValidateConfiguration(config, val)
+}
+
+// ValidateConfigurationKeys just the keys validation steps. The provided *schema.StructValidator should
+// at minimum be checked for errors before continuing. This should be used prior to using ValidateConfiguration.
+func ValidateConfigurationKeys(keys []string, val *schema.StructValidator) {
+	validator.ValidateKeys(keys, configuration.GetMultiKeyMappedDeprecationKeys(), configuration.DefaultEnvPrefix, val)
+}
+
+// ValidateConfiguration just the configuration validation steps. The provided *schema.StructValidator should
+// at minimum be checked for errors before continuing. This should be used after using ValidateConfigurationKeys.
+func ValidateConfiguration(config *schema.Configuration, val *schema.StructValidator) {
+	validator.ValidateConfiguration(config, val)
+}
+
+// NewNamedConfigFileFilters allows configuring a set of file filters. The officially supported filter has the name
+// 'template'. The only other one at this stage is 'expand-env' which is deprecated.
+func NewNamedConfigFileFilters(names ...string) (filters []configuration.BytesFilter, err error) {
+	if filters, err = configuration.NewFileFilters(names); err != nil {
+		return nil, fmt.Errorf("error occurred loading filters: %w", err)
+	}
+
+	return filters, nil
+}