refactor: move filters out of parser

Filters are now separate structures to include a product or not based
on their own set of properties. For now, include and exclude filters
are supported. They take a regex as an argument and include a product
if the regex matches (or doesn't match) the product name. This commit
will allow us to create new filters on product like on a price range.

Signed-off-by: Julien Riou <julien@riou.xyz>

filter_exclude_test.go

@@ -0,0 +1,41 @@
+package main
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestExcludeFilter(t *testing.T) {
+	tests := []struct {
+		regex    string // exclusive regex
+		name     string // product name
+		included bool   // should be included or not
+	}{
+		{"(?i)(rtx|rx)(.*)(3060|3070|3080|3090|5700|6800|6900)( )?(xt|ti)?", "MSI GeForce RTX 3060 GAMING X", false},           // 3060 in the exclude regex
+		{"(?i)(rtx|rx)(.*)(3060|3070|3080|3090|5700|6800|6900)( )?(xt|ti)?", "ASUS AMD Radeon RX 5600 XT TUF Gaming X3", true}, // 5600 not in the exclude regex
+		{"", "MSI GeForce RTX 3060 GAMING X", true}, // do nothing when the exclude regex is empty
+	}
+
+	for i, tc := range tests {
+		t.Run(fmt.Sprintf("TestExcludeFilter#%d", i), func(t *testing.T) {
+			product := &Product{Name: tc.name}
+			filter, err := NewExcludeFilter(tc.regex)
+			if err != nil {
+				t.Errorf("cannot create filter with regex '%s': %s", tc.regex, err)
+			}
+
+			included := filter.Include(product)
+
+			if included != tc.included {
+				t.Errorf("regex '%s' for product '%s': got included=%t, want included=%t", tc.regex, tc.name, included, tc.included)
+			} else {
+				if included {
+					t.Logf("regex '%s' includes product '%s'", tc.regex, tc.name)
+				} else {
+					t.Logf("regex '%s' excludes product '%s'", tc.regex, tc.name)
+				}
+			}
+
+		})
+	}
+}