Add src/main/java/dev/sillyangel/calc/CalculatorHistory.java

src/main/java/dev/sillyangel/calc/CalculatorHistory.java

@@ -0,0 +1,138 @@
+package dev.sillyangel.calc;
+
+import java.io.*;
+import java.nio.file.*;
+import java.time.LocalDateTime;
+import java.time.format.DateTimeFormatter;
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Manages calculation history for the calculator application.
+ * Stores calculations in a file and provides methods to retrieve and manage history.
+ */
+public class CalculatorHistory {
+    private final List<String> calculationHistory = new ArrayList<>();
+    private final Path historyFilePath;
+    private static final String HISTORY_DIR = System.getProperty("user.home") + File.separator + ".calculator";
+    private static final String HISTORY_FILE = "calc_history.txt";
+    private final DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
+
+    public CalculatorHistory() {
+        historyFilePath = Paths.get(HISTORY_DIR, HISTORY_FILE);
+        initializeHistoryFile();
+    }
+
+    /**
+     * Initializes the history file and directory structure.
+     * Creates the directory and file if they don't exist, and loads existing history.
+     */
+    private void initializeHistoryFile() {
+        try {
+            // Create directory if it doesn't exist
+            Path dir = Paths.get(HISTORY_DIR);
+            if (!Files.exists(dir)) {
+                Files.createDirectories(dir);
+                System.out.println("Created history directory: " + HISTORY_DIR);
+            }
+
+            // Create file if it doesn't exist
+            if (!Files.exists(historyFilePath)) {
+                Files.createFile(historyFilePath);
+                System.out.println("Created history file: " + historyFilePath);
+            }
+
+            // Load existing history
+            loadHistory();
+        } catch (IOException e) {
+            System.err.println("Error initializing history file: " + e.getMessage());
+        }
+    }
+
+    /**
+     * Saves a calculation to the history file.
+     * @param calculation The calculation string to save (e.g., "5 + 3 = 8")
+     */
+    public void saveToHistory(String calculation) {
+        try {
+            String timestamp = LocalDateTime.now().format(formatter);
+            String entry = "[" + timestamp + "] " + calculation;
+
+            // Add to memory list
+            calculationHistory.add(entry);
+
+            // Append to file
+            Files.write(historyFilePath,
+                    (entry + System.lineSeparator()).getBytes(),
+                    StandardOpenOption.APPEND);
+
+            System.out.println("Saved to history: " + entry);
+        } catch (IOException e) {
+            System.err.println("Error saving to history: " + e.getMessage());
+        }
+    }
+
+    /**
+     * Loads history from the file into memory.
+     */
+    private void loadHistory() {
+        try {
+            if (Files.exists(historyFilePath)) {
+                List<String> lines = Files.readAllLines(historyFilePath);
+                calculationHistory.addAll(lines);
+                System.out.println("Loaded " + lines.size() + " history entries");
+            }
+        } catch (IOException e) {
+            System.err.println("Error loading history: " + e.getMessage());
+        }
+    }
+
+    /**
+     * Returns a copy of all calculation history entries.
+     * @return A list of history entries with timestamps
+     */
+    public List<String> getCalculationHistory() {
+        return new ArrayList<>(calculationHistory);
+    }
+
+    /**
+     * Returns the most recent N history entries.
+     * @param count The number of entries to return
+     * @return A list of the most recent history entries
+     */
+    public List<String> getRecentHistory(int count) {
+        int size = calculationHistory.size();
+        int fromIndex = Math.max(0, size - count);
+        return new ArrayList<>(calculationHistory.subList(fromIndex, size));
+    }
+
+    /**
+     * Clears all history entries from memory and file.
+     */
+    public void clearHistory() {
+        try {
+            calculationHistory.clear();
+            Files.write(historyFilePath, new byte[0], StandardOpenOption.TRUNCATE_EXISTING);
+            System.out.println("History cleared");
+        } catch (IOException e) {
+            System.err.println("Error clearing history: " + e.getMessage());
+        }
+    }
+
+    /**
+     * Returns the number of history entries.
+     * @return The count of history entries
+     */
+    public int getHistoryCount() {
+        return calculationHistory.size();
+    }
+
+    /**
+     * Returns the path to the history file.
+     * @return The file path as a string
+     */
+    public String getHistoryFilePath() {
+        return historyFilePath.toString();
+    }
+}
+