1 files changed, 97 insertions, 0 deletions
diff --git a/internal/builder/components.go b/internal/builder/components.go
new file mode 100644
index 0000000..54a226a
--- /dev/null
+++ b/internal/builder/components.go
@@ -0,0 +1,97 @@
+package builder
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+	"regexp"
+	"sort"
+	"strings"
+)
+
+// componentRe matches <!-- component:tag-name { ...json... } -->
+// Props JSON is optional.
+var componentRe = regexp.MustCompile(
+	`<!--\s*component:([a-z][a-z0-9-]*)\s*(\{[^}]*\})?\s*-->`)
+
+// customElementRe matches opening tags for custom elements (name must contain a hyphen).
+var customElementRe = regexp.MustCompile(`<([a-z][a-z0-9]*(?:-[a-z0-9]+)+)[\s/>]`)
+
+// ProcessComponents replaces HTML comment component directives with custom element tags.
+//
+//	<!-- component:my-counter {"start": 5, "label": "Count"} -->
+//	→ <my-counter start="5" label="Count"></my-counter>
+func ProcessComponents(html string) string {
+	return componentRe.ReplaceAllStringFunc(html, func(match string) string {
+		subs := componentRe.FindStringSubmatch(match)
+		if len(subs) < 2 {
+			return match
+		}
+		tagName := subs[1]
+		attrs := ""
+		if len(subs) > 2 && subs[2] != "" {
+			var props map[string]any
+			if err := json.Unmarshal([]byte(subs[2]), &props); err == nil {
+				attrs = propsToAttrs(props)
+			}
+		}
+		if attrs != "" {
+			return fmt.Sprintf(`<%s %s></%s>`, tagName, attrs, tagName)
+		}
+		return fmt.Sprintf(`<%s></%s>`, tagName, tagName)
+	})
+}
+
+// propsToAttrs converts a JSON props map to an HTML attribute string.
+// Keys are emitted in sorted order for deterministic output.
+func propsToAttrs(props map[string]any) string {
+	keys := make([]string, 0, len(props))
+	for k := range props {
+		keys = append(keys, k)
+	}
+	sort.Strings(keys)
+
+	var parts []string
+	for _, k := range keys {
+		v := props[k]
+		switch val := v.(type) {
+		case string:
+			parts = append(parts, fmt.Sprintf(`%s="%s"`, k, strings.ReplaceAll(val, `"`, `&quot;`)))
+		case bool:
+			if val {
+				parts = append(parts, k) // boolean attribute, no value
+			}
+		case float64:
+			if val == float64(int64(val)) {
+				parts = append(parts, fmt.Sprintf(`%s="%d"`, k, int64(val)))
+			} else {
+				parts = append(parts, fmt.Sprintf(`%s="%g"`, k, val))
+			}
+		default:
+			// Complex value → JSON-encode into single-quoted attribute.
+			b, _ := json.Marshal(v)
+			parts = append(parts, fmt.Sprintf(`%s='%s'`, k, string(b)))
+		}
+	}
+	return strings.Join(parts, " ")
+}
+
+// FindComponentScripts scans HTML for used custom elements and returns
+// /components/<name>.js paths for any that exist on disk.
+func FindComponentScripts(html, componentsDir string) []string {
+	matches := customElementRe.FindAllStringSubmatch(html, -1)
+	seen := make(map[string]bool)
+	var scripts []string
+	for _, m := range matches {
+		if len(m) < 2 || seen[m[1]] {
+			continue
+		}
+		seen[m[1]] = true
+		jsPath := filepath.Join(componentsDir, m[1]+".js")
+		if _, err := os.Stat(jsPath); err == nil {
+			scripts = append(scripts, "/components/"+m[1]+".js")
+		}
+	}
+	return scripts
+}