grokking simplicity and refactoring

packages/lab-tool/utils/config/loader.scm

@@ -0,0 +1,60 @@
+;; utils/config/loader.scm - Configuration loading (file I/O operations)
+
+(define-module (utils config loader)
+  #:use-module (ice-9 textual-ports)
+  #:use-module (utils logging)
+  #:use-module (utils json)
+  #:use-module (utils config defaults)
+  #:export (load-config-from-file
+            load-config))
+
+;; Pure function: Parse configuration from JSON string
+;; Input: json-string
+;; Output: parsed configuration alist or #f if invalid
+(define (parse-config-json json-string)
+  "Pure function to parse configuration from JSON string"
+  (catch #t
+    (lambda () (json-string->scm-safe json-string))
+    (lambda (key . args) #f)))
+
+;; Pure function: Validate configuration structure
+;; Input: config alist
+;; Output: #t if valid, #f otherwise
+(define (validate-config config)
+  "Pure function to validate configuration structure"
+  (and (list? config)
+       (assoc-ref config 'homelab-root)
+       (assoc-ref config 'machines)))
+
+;; Impure function: Load configuration from file
+;; Input: file-path string
+;; Output: configuration alist or default-config if file doesn't exist/invalid
+(define (load-config-from-file file-path)
+  "Load configuration from file (with side effects: file I/O, logging)"
+  (if (file-exists? file-path)
+      (catch #t
+        (lambda ()
+          (log-debug "Loading configuration from ~a" file-path)
+          (let* ((json-data (call-with-input-file file-path get-string-all))
+                 (parsed-config (parse-config-json json-data)))
+            (if (and parsed-config (validate-config parsed-config))
+                (begin
+                  (log-info "Configuration loaded successfully")
+                  parsed-config)
+                (begin
+                  (log-warn "Invalid configuration file, using defaults")
+                  default-config))))
+        (lambda (key . args)
+          (log-warn "Failed to load config file, using defaults: ~a" key)
+          default-config))
+      (begin
+        (log-debug "No config file found at ~a, using defaults" file-path)
+        default-config)))
+
+;; Impure function: Load configuration with default path
+(define (load-config . args)
+  "Load configuration with optional file path"
+  (let ((config-file (if (null? args) 
+                         (string-append (getenv "HOME") "/.config/homelab/config.json")
+                         (car args))))
+    (load-config-from-file config-file)))