CSV files load as editable markdown tables, save converts back to CSV

src/AppState.swift

@@ -241,9 +241,15 @@ class AppState: ObservableObject {
     }
 
     func saveNote() {
-        bridge.setText(currentNoteID, text: documentText)
+        let textToSave: String
+        if currentFileFormat.isCSV {
+            textToSave = markdownTableToCSV(documentText)
+        } else {
+            textToSave = documentText
+        }
+        bridge.setText(currentNoteID, text: textToSave)
         if let url = currentFileURL {
-            let _ = bridge.saveNote(currentNoteID, path: url.path)
+            try? textToSave.write(to: url, atomically: true, encoding: .utf8)
         }
         let _ = bridge.cacheSave(currentNoteID)
         modified = false
@@ -251,18 +257,30 @@ class AppState: ObservableObject {
     }
 
     func saveNoteToFile(_ url: URL) {
-        let _ = bridge.saveNote(currentNoteID, path: url.path)
+        let format = FileFormat.from(filename: url.lastPathComponent)
+        let textToSave: String
+        if format.isCSV {
+            textToSave = markdownTableToCSV(documentText)
+        } else {
+            textToSave = documentText
+        }
+        try? textToSave.write(to: url, atomically: true, encoding: .utf8)
         currentFileURL = url
-        currentFileFormat = FileFormat.from(filename: url.lastPathComponent)
+        currentFileFormat = format
         modified = false
     }
 
     func loadNoteFromFile(_ url: URL) {
+        let format = FileFormat.from(filename: url.lastPathComponent)
         if let (id, text) = bridge.loadNote(path: url.path) {
             currentNoteID = id
-            documentText = text
             currentFileURL = url
-            currentFileFormat = FileFormat.from(filename: url.lastPathComponent)
+            currentFileFormat = format
+            if format.isCSV {
+                documentText = csvToMarkdownTable(text)
+            } else {
+                documentText = text
+            }
             modified = false
             let _ = bridge.cacheSave(id)
             evaluate()
@@ -270,6 +288,109 @@ class AppState: ObservableObject {
         }
     }
 
+    // MARK: - CSV conversion
+
+    private func csvToMarkdownTable(_ csv: String) -> String {
+        let rows = parseCSVRows(csv)
+        guard let header = rows.first, !header.isEmpty else { return csv }
+
+        var lines: [String] = []
+        lines.append("| " + header.joined(separator: " | ") + " |")
+        lines.append("| " + header.map { _ in "---" }.joined(separator: " | ") + " |")
+        for row in rows.dropFirst() {
+            var cells = row
+            while cells.count < header.count { cells.append("") }
+            lines.append("| " + cells.prefix(header.count).joined(separator: " | ") + " |")
+        }
+        return lines.joined(separator: "\n")
+    }
+
+    private func markdownTableToCSV(_ markdown: String) -> String {
+        let lines = markdown.components(separatedBy: "\n").filter { !$0.isEmpty }
+        var csvRows: [String] = []
+
+        for line in lines {
+            let trimmed = line.trimmingCharacters(in: .whitespaces)
+            guard trimmed.hasPrefix("|") else { continue }
+            if isTableSeparatorLine(trimmed) { continue }
+            let cells = extractTableCells(trimmed)
+            csvRows.append(cells.map { escapeCSVField($0) }.joined(separator: ","))
+        }
+
+        return csvRows.joined(separator: "\n") + "\n"
+    }
+
+    private func parseCSVRows(_ csv: String) -> [[String]] {
+        var rows: [[String]] = []
+        var current: [String] = []
+        var field = ""
+        var inQuotes = false
+        let chars = Array(csv)
+        var i = 0
+
+        while i < chars.count {
+            let ch = chars[i]
+            if inQuotes {
+                if ch == "\"" {
+                    if i + 1 < chars.count && chars[i + 1] == "\"" {
+                        field.append("\"")
+                        i += 2
+                        continue
+                    }
+                    inQuotes = false
+                } else {
+                    field.append(ch)
+                }
+            } else {
+                if ch == "\"" {
+                    inQuotes = true
+                } else if ch == "," {
+                    current.append(field.trimmingCharacters(in: .whitespaces))
+                    field = ""
+                } else if ch == "\n" || ch == "\r" {
+                    current.append(field.trimmingCharacters(in: .whitespaces))
+                    field = ""
+                    if !current.isEmpty {
+                        rows.append(current)
+                    }
+                    current = []
+                    if ch == "\r" && i + 1 < chars.count && chars[i + 1] == "\n" {
+                        i += 1
+                    }
+                } else {
+                    field.append(ch)
+                }
+            }
+            i += 1
+        }
+
+        if !field.isEmpty || !current.isEmpty {
+            current.append(field.trimmingCharacters(in: .whitespaces))
+            rows.append(current)
+        }
+
+        return rows
+    }
+
+    private func isTableSeparatorLine(_ line: String) -> Bool {
+        let stripped = line.replacingOccurrences(of: " ", with: "")
+        return stripped.allSatisfy { "|:-".contains($0) } && stripped.contains("-")
+    }
+
+    private func extractTableCells(_ line: String) -> [String] {
+        var trimmed = line.trimmingCharacters(in: .whitespaces)
+        if trimmed.hasPrefix("|") { trimmed = String(trimmed.dropFirst()) }
+        if trimmed.hasSuffix("|") { trimmed = String(trimmed.dropLast()) }
+        return trimmed.components(separatedBy: "|").map { $0.trimmingCharacters(in: .whitespaces) }
+    }
+
+    private func escapeCSVField(_ field: String) -> String {
+        if field.contains(",") || field.contains("\"") || field.contains("\n") {
+            return "\"" + field.replacingOccurrences(of: "\"", with: "\"\"") + "\""
+        }
+        return field
+    }
+
     func deleteNote(_ id: UUID) {
         bridge.deleteNote(id)
         if id == currentNoteID {