feat: some experiments

template/compile.go

@@ -1,13 +1,9 @@
 package template
 
-import (
-	"fmt"
-)
-
 // CompileTemplate scans once, emitting:
 // - data blocks: inner content between a line that's exactly "{" and a line that's exactly "}"
 // - matching blocks: gaps between data blocks (excluding the brace lines themselves)
-func CompileTemplate(template string) ([]Block, error) {
+func CompileTemplate(templateSource string) ([]Block, error) {
 	var out []Block
 	var curlyIndex int
 
@@ -16,14 +12,15 @@ func CompileTemplate(template string) ([]Block, error) {
 
 	var start int
 	var blockType BlockType
+	template := NewSlice(templateSource)
 
-	if len(template) > 0 && template[0] == OPENING {
+	if template.Len() > 0 && template.At(0) == OPENING {
 		blockType = DataBlock
 	} else {
 		blockType = MatchingBlock
 	}
 
-	for i, r := range template {
+	for i, r := range template.Chars() {
 
 		nextCurlyIndex := curlyIndex
 
@@ -36,27 +33,26 @@ func CompileTemplate(template string) ([]Block, error) {
 
 		if curlyIndex == 0 && nextCurlyIndex == 1 {
 			if i > start {
-				block, err := ParseTemplateBlock(template[start:i], blockType)
+				block, err := ParseTemplateBlock(template.Slice(start, i), blockType)
 				if err != nil {
-					return nil, fmt.Errorf("cannot parse block: %w", err)
+					return nil, NewErrorf("cannot parse block @pos -> %w", err).WithPosition(start, i)
 				}
 				out = append(out, block)
 			}
 			start = i
 			blockType = DataBlock
 		} else if curlyIndex == 1 && nextCurlyIndex == 0 {
-
 			if i > start {
-				block, err := ParseTemplateBlock(template[start:i+1], blockType)
+				block, err := ParseTemplateBlock(template.Slice(start, i), blockType)
 				if err != nil {
-					return nil, fmt.Errorf("cannot parse block: %w", err)
+					return nil, NewErrorf("cannot parse block @pos -> %w", err).WithPosition(start, i)
 				}
 				out = append(out, block)
 			}
 
 			nextChar := ' '
-			if i+1 < len(template) {
-				nextChar = rune(template[i+1])
+			if i+1 < template.Len() {
+				nextChar = rune(template.At(i + 1))
 			}
 
 			if nextChar == OPENING {