feat: add env decoder

internal/utils/decoders/env_decoder.go

@@ -0,0 +1,136 @@
+package decoders
+
+import (
+	"fmt"
+	"slices"
+	"sort"
+	"strings"
+	"tinyauth/internal/config"
+	"tinyauth/internal/utils"
+
+	"github.com/traefik/paerser/parser"
+)
+
+func DecodeEnv(env map[string]string) (config.Providers, error) {
+	normalized := normalizeEnv(env, "tinyauth")
+
+	node, err := decodeEnvsToNode(normalized, "tinyauth", "tinyauth_providers")
+
+	if err != nil {
+		return config.Providers{}, err
+	}
+
+	var providers config.Providers
+
+	metaOpts := parser.MetadataOpts{TagName: "env", AllowSliceAsStruct: true}
+
+	err = parser.AddMetadata(&providers, node, metaOpts)
+
+	if err != nil {
+		return config.Providers{}, err
+	}
+
+	err = parser.Fill(&providers, node, parser.FillerOpts{AllowSliceAsStruct: true})
+
+	if err != nil {
+		return config.Providers{}, err
+	}
+
+	return providers, nil
+}
+
+func decodeEnvsToNode(env map[string]string, rootName string, filters ...string) (*parser.Node, error) {
+	sorted := sortEnvKeys(env, filters)
+
+	var node *parser.Node
+
+	for i, k := range sorted {
+		split := strings.SplitN(k, "_", 4)
+
+		if split[0] != rootName {
+			return nil, fmt.Errorf("invalid env root %s", split[0])
+		}
+
+		if slices.Contains(split, "") {
+			return nil, fmt.Errorf("invalid element: %s", k)
+		}
+
+		if i == 0 {
+			node = &parser.Node{}
+		}
+
+		decodeEnvToNode(node, split, env[k])
+	}
+
+	return node, nil
+}
+
+func decodeEnvToNode(root *parser.Node, path []string, value string) {
+	if len(root.Name) == 0 {
+		root.Name = path[0]
+	}
+
+	if !(len(path) > 1) {
+		root.Value = value
+		return
+	}
+
+	if n := containsEnvNode(root.Children, path[1]); n != nil {
+		decodeEnvToNode(n, path[1:], value)
+		return
+	}
+
+	child := &parser.Node{Name: path[1]}
+	decodeEnvToNode(child, path[1:], value)
+	root.Children = append(root.Children, child)
+}
+
+func containsEnvNode(node []*parser.Node, name string) *parser.Node {
+	for _, n := range node {
+		if strings.EqualFold(n.Name, name) {
+			return n
+		}
+	}
+	return nil
+}
+
+func sortEnvKeys(env map[string]string, filters []string) []string {
+	var sorted []string
+
+	for k := range env {
+		if len(filters) == 0 {
+			sorted = append(sorted, k)
+			continue
+		}
+
+		for _, f := range filters {
+			if strings.HasPrefix(k, f) {
+				sorted = append(sorted, k)
+				break
+			}
+		}
+	}
+
+	sort.Strings(sorted)
+	return sorted
+}
+
+// normalizeEnv converts env vars from PROVIDERS_CLIENT1_CLIENT_ID to tinyauth_providers_client_clientId
+func normalizeEnv(env map[string]string, rootName string) map[string]string {
+	n := make(map[string]string)
+	for k, v := range env {
+		fk := strings.ToLower(k)
+		fks := strings.SplitN(fk, "_", 3)
+		fkb := ""
+		for i, s := range strings.Split(fks[len(fks)-1], "_") {
+			if i == 0 {
+				fkb += s
+				continue
+			}
+			fkb += utils.Capitalize(s)
+		}
+		fk = rootName + "_" + strings.Join(fks[:len(fks)-1], "_") + "_" + fkb
+		n[fk] = v
+	}
+	return n
+}