Break up Gemtext link parsing code and improve tests.

gemini/geminiLinks.go

@@ -0,0 +1,88 @@
+package gemini
+
+import (
+	"fmt"
+	"net/url"
+	"regexp"
+
+	"gemini-grc/common"
+	"gemini-grc/logging"
+	"gemini-grc/util"
+)
+
+func GetPageLinks(currentURL common.URL, gemtext string) common.LinkList {
+	linkLines := util.GetLinesMatchingRegex(gemtext, `(?m)^=>[ \t]+.*`)
+	if len(linkLines) == 0 {
+		return nil
+	}
+	var linkURLs common.LinkList
+	// Normalize URLs in links
+	for _, line := range linkLines {
+		linkUrl, err := ParseGeminiLinkLine(line, currentURL.String())
+		if err != nil {
+			logging.LogDebug("%s: %s", common.ErrGeminiLinkLineParse, err)
+			continue
+		}
+		linkURLs = append(linkURLs, *linkUrl)
+	}
+	return linkURLs
+}
+
+// ParseGeminiLinkLine takes a single link line and the current URL,
+// return the URL converted to an absolute URL
+// and its description.
+func ParseGeminiLinkLine(linkLine string, currentURL string) (*common.URL, error) {
+	// Check: currentURL is parseable
+	baseURL, err := url.Parse(currentURL)
+	if err != nil {
+		return nil, fmt.Errorf("%w: %w", common.ErrURLParse, err)
+	}
+
+	// Extract the actual URL and the description
+	re := regexp.MustCompile(`^=>[ \t]+(\S+)([ \t]+.*)?`)
+	matches := re.FindStringSubmatch(linkLine)
+	if len(matches) == 0 {
+		// If the line doesn't match the expected format, return it unchanged
+		return nil, fmt.Errorf("%w could not parse gemini link %s", common.ErrGeminiLinkLineParse, linkLine)
+	}
+
+	originalURLStr := matches[1]
+
+	// Check: Unescape the URL if escaped
+	_, err = url.QueryUnescape(originalURLStr)
+	if err != nil {
+		return nil, fmt.Errorf("%w: %w", common.ErrURLDecode, err)
+	}
+
+	description := ""
+	if len(matches) > 2 {
+		description = matches[2]
+	}
+
+	// Parse the URL from the link line
+	parsedURL, err := url.Parse(originalURLStr)
+	if err != nil {
+		// If URL parsing fails, return an error
+		return nil, fmt.Errorf("%w: %w", common.ErrURLParse, err)
+	}
+
+	// If link URL is relative, resolve full URL
+	if !parsedURL.IsAbs() {
+		parsedURL = baseURL.ResolveReference(parsedURL)
+	}
+
+	// Remove usual first space from URL description:
+	// => URL description
+	//       ^^^^^^^^^^^^
+	if len(description) > 0 && description[0] == ' ' {
+		description = description[1:]
+	}
+	
+	finalURL, err := common.ParseURL(parsedURL.String(), description)
+	if err != nil {
+		// If URL parsing fails, return an error
+		return nil, fmt.Errorf("%w: %w", common.ErrURLParse, err)
+	}
+
+	return finalURL, nil
+}