feat: add README parser with entry extraction and section tree building

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/parser/parser.go

@@ -0,0 +1,128 @@
+package parser
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"regexp"
+	"strings"
+)
+
+// entryRe matches: - [Name](URL) - Description
+var entryRe = regexp.MustCompile(`^[-*]\s+\[([^\]]+)\]\(([^)]+)\)\s+-\s+(.+)$`)
+
+// headingRe matches markdown headings: # Title, ## Title, etc.
+var headingRe = regexp.MustCompile(`^(#{1,6})\s+(.+?)(?:\s*<!--.*-->)?$`)
+
+var markerMap = map[string]Marker{
+	":skull:":             MarkerAbandoned,
+	":heavy_dollar_sign:": MarkerPaid,
+	":construction:":      MarkerWIP,
+}
+
+// ParseEntry parses a single markdown list line into an Entry.
+func ParseEntry(line string, lineNum int) (Entry, error) {
+	m := entryRe.FindStringSubmatch(strings.TrimSpace(line))
+	if m == nil {
+		return Entry{}, fmt.Errorf("line %d: not a valid entry: %q", lineNum, line)
+	}
+
+	desc := m[3]
+	var markers []Marker
+
+	for text, marker := range markerMap {
+		if strings.Contains(desc, text) {
+			markers = append(markers, marker)
+			desc = strings.ReplaceAll(desc, text, "")
+		}
+	}
+	desc = strings.TrimSpace(desc)
+
+	return Entry{
+		Name:        m[1],
+		URL:         m[2],
+		Description: desc,
+		Markers:     markers,
+		Line:        lineNum,
+		Raw:         line,
+	}, nil
+}
+
+// Parse reads a full README and returns a Document.
+func Parse(r io.Reader) (Document, error) {
+	scanner := bufio.NewScanner(r)
+	var doc Document
+	var allSections []struct {
+		section Section
+		level   int
+	}
+
+	lineNum := 0
+	for scanner.Scan() {
+		lineNum++
+		line := scanner.Text()
+
+		// Check for heading
+		if hm := headingRe.FindStringSubmatch(line); hm != nil {
+			level := len(hm[1])
+			title := strings.TrimSpace(hm[2])
+			allSections = append(allSections, struct {
+				section Section
+				level   int
+			}{
+				section: Section{Title: title, Level: level, Line: lineNum},
+				level:   level,
+			})
+			continue
+		}
+
+		// Check for entry (list item with link)
+		if entry, err := ParseEntry(line, lineNum); err == nil {
+			if len(allSections) > 0 {
+				allSections[len(allSections)-1].section.Entries = append(
+					allSections[len(allSections)-1].section.Entries, entry)
+			}
+			continue
+		}
+
+		// Everything else: preamble if no sections yet
+		if len(allSections) == 0 {
+			doc.Preamble = append(doc.Preamble, line)
+		}
+	}
+
+	if err := scanner.Err(); err != nil {
+		return doc, err
+	}
+
+	// Build section tree by nesting based on heading level
+	doc.Sections = buildTree(allSections)
+	return doc, nil
+}
+
+func buildTree(flat []struct {
+	section Section
+	level   int
+}) []Section {
+	if len(flat) == 0 {
+		return nil
+	}
+
+	var result []Section
+	for i := 0; i < len(flat); i++ {
+		current := flat[i].section
+		currentLevel := flat[i].level
+
+		// Collect children: everything after this heading at a deeper level
+		j := i + 1
+		for j < len(flat) && flat[j].level > currentLevel {
+			j++
+		}
+		if j > i+1 {
+			current.Children = buildTree(flat[i+1 : j])
+		}
+		result = append(result, current)
+		i = j - 1
+	}
+	return result
+}