add sorting; implement sort criteria in default repo ; adding html header

internal/data/DefaultRepository.go

@@ -3,6 +3,7 @@ package data
 import (
 	"encoding/json"
 	"errors"
+	"slices"
 	"strings"
 )
 
@@ -111,7 +112,24 @@ func (repo *DefaultRepository[T]) GetById(id string) (T, error) {
     return obj, nil
 }
 
-func (repo *DefaultRepository[T]) GetByCriteria(c ISearchCriteria[T]) ([]T, error) {
-    // TODO
-    return nil, nil
+// Returns a slice of all elememts in the repo sort by the given an
+// ISearchCriteria. Throws an error when the elememts cannot be retrieved from
+// the repo.
+func (repo *DefaultRepository[T]) GetByCriteria(c ISortCriteria[T]) ([]T, error) {
+    all, err := repo.GetAll()
+    if err != nil { return nil, err }
+
+    slices.SortFunc(all, func(a, b T) int {
+        wa, wb := c.Weight(a), c.Weight(b)
+        switch {
+            case wa > wb:
+                return 1
+            case wa < wb:
+                return -1
+            default:
+                return 0
+        }
+    })
+
+    return all, nil
 }