add syntax highlighting and markdown rendering

src/EditorView.swift

@@ -32,7 +32,7 @@ struct EditorTextView: NSViewRepresentable {
         textView.isEditable = true
         textView.isSelectable = true
         textView.allowsUndo = true
-        textView.isRichText = false
+        textView.isRichText = true
         textView.usesFindBar = true
         textView.isIncrementalSearchingEnabled = true
         textView.font = Theme.editorFont
@@ -74,6 +74,12 @@ struct EditorTextView: NSViewRepresentable {
         context.coordinator.textView = textView
         context.coordinator.rulerView = ruler
 
+        if let ts = textView.textStorage {
+            ts.beginEditing()
+            applySyntaxHighlighting(to: ts)
+            ts.endEditing()
+        }
+
         return scrollView
     }
 
@@ -82,6 +88,11 @@ struct EditorTextView: NSViewRepresentable {
         if textView.string != text {
             let selectedRanges = textView.selectedRanges
             textView.string = text
+            if let ts = textView.textStorage {
+                ts.beginEditing()
+                applySyntaxHighlighting(to: ts)
+                ts.endEditing()
+            }
             textView.selectedRanges = selectedRanges
         }
         textView.font = Theme.editorFont
@@ -105,8 +116,13 @@ struct EditorTextView: NSViewRepresentable {
         }
 
         func textDidChange(_ notification: Notification) {
-            guard let tv = textView else { return }
+            guard let tv = textView, let ts = tv.textStorage else { return }
             parent.text = tv.string
+            let sel = tv.selectedRanges
+            ts.beginEditing()
+            applySyntaxHighlighting(to: ts)
+            ts.endEditing()
+            tv.selectedRanges = sel
             rulerView?.needsDisplay = true
         }
 
@@ -123,6 +139,241 @@ struct EditorTextView: NSViewRepresentable {
     }
 }
 
+// MARK: - Syntax Highlighting
+
+private let syntaxKeywords: Set<String> = [
+    "let", "fn", "if", "else", "for", "map", "cast", "plot", "sch"
+]
+
+private let syntaxOperatorChars = CharacterSet(charactersIn: "+-*/=^<>!(){}[]:,")
+
+func applySyntaxHighlighting(to textStorage: NSTextStorage) {
+    let text = textStorage.string
+    let fullRange = NSRange(location: 0, length: (text as NSString).length)
+    let palette = Theme.current
+    let syn = Theme.syntax
+
+    let baseFont = Theme.editorFont
+    let baseAttrs: [NSAttributedString.Key: Any] = [
+        .font: baseFont,
+        .foregroundColor: palette.text
+    ]
+    textStorage.setAttributes(baseAttrs, range: fullRange)
+
+    let nsText = text as NSString
+    var lineStart = 0
+
+    while lineStart < nsText.length {
+        let lineRange = nsText.lineRange(for: NSRange(location: lineStart, length: 0))
+        let line = nsText.substring(with: lineRange)
+        let trimmed = line.trimmingCharacters(in: .whitespaces)
+
+        if highlightMarkdownLine(trimmed, lineRange: lineRange, textStorage: textStorage, baseFont: baseFont, palette: palette) {
+            lineStart = NSMaxRange(lineRange)
+            continue
+        }
+
+        highlightCodeLine(line, lineRange: lineRange, textStorage: textStorage, syn: syn)
+
+        lineStart = NSMaxRange(lineRange)
+    }
+
+    highlightBlockComments(textStorage: textStorage, syn: syn, baseFont: baseFont)
+}
+
+private func highlightMarkdownLine(_ trimmed: String, lineRange: NSRange, textStorage: NSTextStorage, baseFont: NSFont, palette: CatppuccinPalette) -> Bool {
+    if trimmed.hasPrefix("## ") {
+        let hashRange = (textStorage.string as NSString).range(of: "##", range: lineRange)
+        if hashRange.location != NSNotFound {
+            textStorage.addAttribute(.foregroundColor, value: palette.overlay0, range: hashRange)
+            let contentStart = hashRange.location + hashRange.length
+            let contentRange = NSRange(location: contentStart, length: NSMaxRange(lineRange) - contentStart)
+            if contentRange.length > 0 {
+                let h2Font = NSFont.systemFont(ofSize: 18, weight: .bold)
+                textStorage.addAttribute(.font, value: h2Font, range: contentRange)
+            }
+        }
+        return true
+    }
+
+    if trimmed.hasPrefix("# ") {
+        let hashRange = (textStorage.string as NSString).range(of: "#", range: lineRange)
+        if hashRange.location != NSNotFound {
+            textStorage.addAttribute(.foregroundColor, value: palette.overlay0, range: hashRange)
+            let contentStart = hashRange.location + hashRange.length
+            let contentRange = NSRange(location: contentStart, length: NSMaxRange(lineRange) - contentStart)
+            if contentRange.length > 0 {
+                let h1Font = NSFont.systemFont(ofSize: 22, weight: .bold)
+                textStorage.addAttribute(.font, value: h1Font, range: contentRange)
+            }
+        }
+        return true
+    }
+
+    if trimmed.hasPrefix("> ") {
+        textStorage.addAttribute(.foregroundColor, value: palette.overlay2, range: lineRange)
+        let indent = NSMutableParagraphStyle()
+        indent.headIndent = 20
+        indent.firstLineHeadIndent = 20
+        textStorage.addAttribute(.paragraphStyle, value: indent, range: lineRange)
+        return true
+    }
+
+    return false
+}
+
+private func highlightCodeLine(_ line: String, lineRange: NSRange, textStorage: NSTextStorage, syn: Theme.SyntaxColors) {
+    let nsLine = line as NSString
+    let baseFont = Theme.editorFont
+    let italicFont = NSFontManager.shared.convert(baseFont, toHaveTrait: .italicTrait)
+    let boldFont = NSFontManager.shared.convert(baseFont, toHaveTrait: .boldTrait)
+
+    let trimmed = line.trimmingCharacters(in: .whitespaces)
+
+    // Line comment
+    if let commentRange = findLineComment(nsLine) {
+        let absRange = NSRange(location: lineRange.location + commentRange.location, length: commentRange.length)
+        textStorage.addAttributes([
+            .foregroundColor: syn.comment,
+            .font: italicFont
+        ], range: absRange)
+        highlightCodeTokens(nsLine, inRange: NSRange(location: 0, length: commentRange.location), lineOffset: lineRange.location, textStorage: textStorage, syn: syn)
+        return
+    }
+
+    // Eval prefix
+    if trimmed.hasPrefix("/=") {
+        let prefixRange = (textStorage.string as NSString).range(of: "/=", range: lineRange)
+        if prefixRange.location != NSNotFound {
+            textStorage.addAttribute(.foregroundColor, value: syn.operator, range: prefixRange)
+        }
+    }
+
+    highlightCodeTokens(nsLine, inRange: NSRange(location: 0, length: nsLine.length), lineOffset: lineRange.location, textStorage: textStorage, syn: syn)
+
+    // Bold markers **text**
+    highlightInlineMarkdown(textStorage: textStorage, lineRange: lineRange, pattern: "\\*\\*(.+?)\\*\\*", markerLen: 2, trait: .boldTrait, font: boldFont)
+
+    // Italic markers *text*
+    highlightInlineMarkdown(textStorage: textStorage, lineRange: lineRange, pattern: "(?<!\\*)\\*(?!\\*)(.+?)(?<!\\*)\\*(?!\\*)", markerLen: 1, trait: .italicTrait, font: italicFont)
+}
+
+private func highlightInlineMarkdown(textStorage: NSTextStorage, lineRange: NSRange, pattern: String, markerLen: Int, trait: NSFontTraitMask, font: NSFont) {
+    let palette = Theme.current
+    guard let regex = try? NSRegularExpression(pattern: pattern) else { return }
+    let matches = regex.matches(in: textStorage.string, range: lineRange)
+    for match in matches {
+        let fullRange = match.range
+        let openMarker = NSRange(location: fullRange.location, length: markerLen)
+        let closeMarker = NSRange(location: fullRange.location + fullRange.length - markerLen, length: markerLen)
+        let contentRange = NSRange(location: fullRange.location + markerLen, length: fullRange.length - markerLen * 2)
+        textStorage.addAttribute(.foregroundColor, value: palette.overlay0, range: openMarker)
+        textStorage.addAttribute(.foregroundColor, value: palette.overlay0, range: closeMarker)
+        if contentRange.length > 0 {
+            textStorage.addAttribute(.font, value: font, range: contentRange)
+        }
+    }
+}
+
+private func findLineComment(_ line: NSString) -> NSRange? {
+    guard line.length >= 2 else { return nil }
+    var i = 0
+    var inString = false
+    while i < line.length - 1 {
+        let ch = line.character(at: i)
+        if ch == UInt16(UnicodeScalar("\"").value) {
+            inString = !inString
+        } else if !inString && ch == UInt16(UnicodeScalar("/").value) && line.character(at: i + 1) == UInt16(UnicodeScalar("/").value) {
+            return NSRange(location: i, length: line.length - i)
+        }
+        i += 1
+    }
+    return nil
+}
+
+private func highlightCodeTokens(_ line: NSString, inRange range: NSRange, lineOffset: Int, textStorage: NSTextStorage, syn: Theme.SyntaxColors) {
+    let sub = line.substring(with: range)
+    let scanner = Scanner(string: sub)
+    scanner.charactersToBeSkipped = nil
+    let digitChars = CharacterSet.decimalDigits.union(CharacterSet(charactersIn: "."))
+    let identStart = CharacterSet.letters.union(CharacterSet(charactersIn: "_"))
+    let identChars = identStart.union(.decimalDigits)
+
+    while !scanner.isAtEnd {
+        let pos = scanner.currentIndex
+
+        // String literal
+        if scanner.scanString("\"") != nil {
+            let startIdx = sub.distance(from: sub.startIndex, to: pos)
+            var strContent = "\""
+            var escaped = false
+            while !scanner.isAtEnd {
+                let ch = sub[scanner.currentIndex]
+                strContent.append(ch)
+                scanner.currentIndex = sub.index(after: scanner.currentIndex)
+                if escaped {
+                    escaped = false
+                    continue
+                }
+                if ch == "\\" { escaped = true; continue }
+                if ch == "\"" { break }
+            }
+            let absRange = NSRange(location: lineOffset + range.location + startIdx, length: strContent.count)
+            textStorage.addAttribute(.foregroundColor, value: syn.string, range: absRange)
+            continue
+        }
+
+        // Number
+        if let numStr = scanner.scanCharacters(from: digitChars) {
+            let startIdx = sub.distance(from: sub.startIndex, to: pos)
+            let absRange = NSRange(location: lineOffset + range.location + startIdx, length: numStr.count)
+            textStorage.addAttribute(.foregroundColor, value: syn.number, range: absRange)
+            continue
+        }
+
+        // Identifier / keyword
+        if let ident = scanner.scanCharacters(from: identChars) {
+            if let first = ident.unicodeScalars.first, identStart.contains(first) {
+                let startIdx = sub.distance(from: sub.startIndex, to: pos)
+                let absRange = NSRange(location: lineOffset + range.location + startIdx, length: ident.count)
+                if syntaxKeywords.contains(ident) {
+                    textStorage.addAttribute(.foregroundColor, value: syn.keyword, range: absRange)
+                }
+            }
+            continue
+        }
+
+        // Operator
+        if let op = scanner.scanCharacters(from: syntaxOperatorChars) {
+            let startIdx = sub.distance(from: sub.startIndex, to: pos)
+            let absRange = NSRange(location: lineOffset + range.location + startIdx, length: op.count)
+            textStorage.addAttribute(.foregroundColor, value: syn.operator, range: absRange)
+            continue
+        }
+
+        // Skip unrecognized character
+        scanner.currentIndex = sub.index(after: scanner.currentIndex)
+    }
+}
+
+private func highlightBlockComments(textStorage: NSTextStorage, syn: Theme.SyntaxColors, baseFont: NSFont) {
+    let text = textStorage.string
+    let nsText = text as NSString
+    let italicFont = NSFontManager.shared.convert(baseFont, toHaveTrait: .italicTrait)
+
+    guard let regex = try? NSRegularExpression(pattern: "/\\*.*?\\*/", options: .dotMatchesLineSeparators) else { return }
+    let fullRange = NSRange(location: 0, length: nsText.length)
+    let matches = regex.matches(in: text, range: fullRange)
+    for match in matches {
+        textStorage.addAttributes([
+            .foregroundColor: syn.comment,
+            .font: italicFont
+        ], range: match.range)
+    }
+}
+
+// MARK: - LineNumberTextView
+
 class LineNumberTextView: NSTextView {
     override func drawInsertionPoint(in rect: NSRect, color: NSColor, turnedOn flag: Bool) {
         var widened = rect