Add positive URL_RULES

README.md

@@ -17,5 +17,7 @@ Configuration is handled through environment variables as listed below:
     - Example: `HEADERS=Rate-Limit-Token:ABC123,X-Header:X-Value`
 - CONCURRENCY: Controls the number of concurrent requests, useful for controlling request rate.
     - Example: `CONCURRENCY=10`
+- URL_RULES: A comma-separated list of regex patterns matching URLs that the crawler should crawl. All other URLs will be avoided.
+    - Example: `URL_RULES=https://www.gov.uk/.*`
 - DISALLOWED_URL_RULES: A comma-separated list of regex patterns matching URLs that the crawler should avoid.
     - Example: `DISALLOWED_URL_RULES=/search/.*,/government/.*\.atom`

internal/client/client.go

@@ -42,6 +42,12 @@ func NewClient(c *colly.Collector, redirectHandler func(*http.Request, []*http.R
 func isRequestAllowed(c *colly.Collector, parsedURL *url.URL) bool {
 	u := []byte(parsedURL.String())
 
+	for _, r := range c.URLFilters {
+		if !r.Match(u) {
+			return false
+		}
+	}
+
 	for _, r := range c.DisallowedURLFilters {
 		if r.Match(u) {
 			return false

internal/client/client_test.go

@@ -44,6 +44,7 @@ func TestNewClient(t *testing.T) {
 func TestIsRequestAllowedTableDriven(t *testing.T) {
 	tests := []struct {
 		name            string
+		allowedURLs     []*regexp.Regexp
 		disallowedURLs  []*regexp.Regexp
 		allowedDomains  []string
 		url             string
@@ -60,6 +61,12 @@ func TestIsRequestAllowedTableDriven(t *testing.T) {
 			url:             "http://example.com",
 			expectedAllowed: false,
 		},
+		{
+			name:            "URL filter",
+			allowedURLs:     []*regexp.Regexp{regexp.MustCompile("https://www.gov.uk")},
+			url:             "http://example.com",
+			expectedAllowed: false,
+		},
 		{
 			name:            "allowed domain",
 			allowedDomains:  []string{"example.com"},
@@ -78,6 +85,7 @@ func TestIsRequestAllowedTableDriven(t *testing.T) {
 		t.Run(tt.name, func(t *testing.T) {
 			c := colly.NewCollector()
 			c.DisallowedURLFilters = tt.disallowedURLs
+			c.URLFilters = tt.allowedURLs
 			c.AllowedDomains = tt.allowedDomains
 			parsedURL, _ := url.Parse(tt.url)
 			assert.Equal(t, tt.expectedAllowed, isRequestAllowed(c, parsedURL))

internal/config/config.go

@@ -13,6 +13,7 @@ type Config struct {
 	UserAgent            string            `env:"USER_AGENT" envDefault:"govukbot"`
 	Headers              map[string]string `env:"HEADERS"`
 	Concurrency          int               `env:"CONCURRENCY" envDefault:"10"`
+	URLFilters           []*regexp.Regexp  `env:"URL_RULES" envSeparator:","`
 	DisallowedURLFilters []*regexp.Regexp  `env:"DISALLOWED_URL_RULES" envSeparator:","`
 }
 

internal/config/config_test.go

@@ -29,7 +29,8 @@ func TestNewConfig(t *testing.T) {
 				"USER_AGENT":           "custom-agent",
 				"HEADERS":              "Test-Header:Test-Value",
 				"CONCURRENCY":          "20",
-				"DISALLOWED_URL_RULES": "rule1,rule2",
+				"URL_RULES":            "rule1,rule2",
+				"DISALLOWED_URL_RULES": "rule3,rule4",
 			},
 			expected: &Config{
 				Site:           "example.com",
@@ -39,10 +40,14 @@ func TestNewConfig(t *testing.T) {
 					"Test-Header": "Test-Value",
 				},
 				Concurrency: 20,
-				DisallowedURLFilters: []*regexp.Regexp{
+				URLFilters: []*regexp.Regexp{
 					regexp.MustCompile("rule1"),
 					regexp.MustCompile("rule2"),
 				},
+				DisallowedURLFilters: []*regexp.Regexp{
+					regexp.MustCompile("rule3"),
+					regexp.MustCompile("rule4"),
+				},
 			},
 		},
 	}

internal/crawler/crawler.go

@@ -31,6 +31,7 @@ func newCollector(cfg *config.Config) (*colly.Collector, error) {
 	c := colly.NewCollector(
 		colly.UserAgent(cfg.UserAgent),
 		colly.AllowedDomains(cfg.AllowedDomains...),
+		colly.URLFilters(cfg.URLFilters...),
 		colly.DisallowedURLFilters(cfg.DisallowedURLFilters...),
 		colly.Async(true),
 	)

internal/crawler/crawler_test.go

@@ -184,6 +184,9 @@ func TestNewCrawler(t *testing.T) {
 	cfg := &config.Config{
 		UserAgent:      "custom-agent",
 		AllowedDomains: []string{"example.com"},
+		URLFilters: []*regexp.Regexp{
+			regexp.MustCompile(".*"),
+		},
 		DisallowedURLFilters: []*regexp.Regexp{
 			regexp.MustCompile(".*disallowed.*"),
 		},
@@ -196,6 +199,7 @@ func TestNewCrawler(t *testing.T) {
 	assert.IsType(t, &colly.Collector{}, cr.collector)
 	assert.Equal(t, "custom-agent", cr.collector.UserAgent)
 	assert.Equal(t, []string{"example.com"}, cr.collector.AllowedDomains)
+	assert.Equal(t, []*regexp.Regexp{regexp.MustCompile(".*")}, cr.collector.URLFilters)
 	assert.Equal(t, []*regexp.Regexp{regexp.MustCompile(".*disallowed.*")}, cr.collector.DisallowedURLFilters)
 	assert.Equal(t, true, cr.collector.Async)
 }
@@ -284,6 +288,9 @@ func TestRun(t *testing.T) {
 	cfg := &config.Config{
 		Site:           ts.URL + "/sitemap.xml",
 		AllowedDomains: []string{hostname},
+		URLFilters: []*regexp.Regexp{
+			regexp.MustCompile(".*"),
+		},
 		DisallowedURLFilters: []*regexp.Regexp{
 			regexp.MustCompile("/disallowed"),
 		},