Refactor frontmatter.go: Extract 4 focused modules (39% size reduction)

pkg/parser/ansi_strip.go

@@ -0,0 +1,108 @@
+package parser
+
+import (
+	"strings"
+)
+
+// StripANSI removes ANSI escape codes from a string
+func StripANSI(s string) string {
+	if s == "" {
+		return s
+	}
+
+	var result strings.Builder
+	result.Grow(len(s)) // Pre-allocate capacity for efficiency
+
+	i := 0
+	for i < len(s) {
+		if s[i] == '\x1b' {
+			if i+1 >= len(s) {
+				// ESC at end of string, skip it
+				i++
+				continue
+			}
+			// Found ESC character, determine sequence type
+			switch s[i+1] {
+			case '[':
+				// CSI sequence: \x1b[...final_char
+				// Parameters are in range 0x30-0x3F (0-?), intermediate chars 0x20-0x2F (space-/)
+				// Final characters are in range 0x40-0x7E (@-~)
+				i += 2 // Skip ESC and [
+				for i < len(s) {
+					if isFinalCSIChar(s[i]) {
+						i++ // Skip the final character
+						break
+					} else if isCSIParameterChar(s[i]) {
+						i++ // Skip parameter/intermediate character
+					} else {
+						// Invalid character in CSI sequence, stop processing this escape
+						break
+					}
+				}
+			case ']':
+				// OSC sequence: \x1b]...terminator
+				// Terminators: \x07 (BEL) or \x1b\\ (ST)
+				i += 2 // Skip ESC and ]
+				for i < len(s) {
+					if s[i] == '\x07' {
+						i++ // Skip BEL
+						break
+					} else if s[i] == '\x1b' && i+1 < len(s) && s[i+1] == '\\' {
+						i += 2 // Skip ESC and \
+						break
+					}
+					i++
+				}
+			case '(':
+				// G0 character set selection: \x1b(char
+				i += 2 // Skip ESC and (
+				if i < len(s) {
+					i++ // Skip the character
+				}
+			case ')':
+				// G1 character set selection: \x1b)char
+				i += 2 // Skip ESC and )
+				if i < len(s) {
+					i++ // Skip the character
+				}
+			case '=':
+				// Application keypad mode: \x1b=
+				i += 2
+			case '>':
+				// Normal keypad mode: \x1b>
+				i += 2
+			case 'c':
+				// Reset: \x1bc
+				i += 2
+			default:
+				// Other escape sequences (2-character)
+				// Handle common ones like \x1b7, \x1b8, \x1bD, \x1bE, \x1bH, \x1bM
+				if i+1 < len(s) && (s[i+1] >= '0' && s[i+1] <= '~') {
+					i += 2
+				} else {
+					// Invalid or incomplete escape sequence, just skip ESC
+					i++
+				}
+			}
+		} else {
+			// Regular character, keep it
+			result.WriteByte(s[i])
+			i++
+		}
+	}
+
+	return result.String()
+}
+
+// isFinalCSIChar checks if a character is a valid CSI final character
+// Final characters are in range 0x40-0x7E (@-~)
+func isFinalCSIChar(b byte) bool {
+	return b >= 0x40 && b <= 0x7E
+}
+
+// isCSIParameterChar checks if a character is a valid CSI parameter or intermediate character
+// Parameter characters are in range 0x30-0x3F (0-?)
+// Intermediate characters are in range 0x20-0x2F (space-/)
+func isCSIParameterChar(b byte) bool {
+	return (b >= 0x20 && b <= 0x2F) || (b >= 0x30 && b <= 0x3F)
+}