package de.hs_mannheim.informatik.spreadsheet;

import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * A simplified spreadsheet class for the PR1 programming lab at Hochschule Mannheim.
 * One aspect worth mentioning is that it only supports long numbers, not doubles.
 *
 * @author  Oliver Hummel
 */
public class Spreadsheet {
	Cell[][] cells;

	/**
	 * Constructor that creates a Spreadsheet of size rows * cols.
	 * @param rows number of rows
	 * @param cols number of columns
	 */
	public Spreadsheet(int rows, int cols) {

		// TODO limit the maximum size on 99 (1..99) rows and 26 (A..Z) columns

		cells = new Cell[rows][cols];

		for (int r = 0; r < rows; r++)
			for (int c = 0; c < cols; c++)
				cells[r][c] = new Cell();
	}

	// -----
	// retrieve or change values of cells

	private String get(int row, int col) {
		return cells[row][col].getValue();
	}

	public String get(String cellName) {
		cellName = cellName.toUpperCase();
		return get(getRow(cellName), getCol(cellName));
	}

	private void put(int row, int col, String value) {
		if (!value.startsWith("="))
			cells[row][col].setValue(value);
		else {
			cells[row][col].setFormula(value);
			evaluateCell(row, col);
		}
	}

	public void put(String cellName, String value) {
		cellName = cellName.toUpperCase();
		put(getRow(cellName), getCol(cellName), value);
	}

	private int getCol(String cellName) {
		return cellName.charAt(0) - 'A';
	}

	private int getRow(String cellName) {
		return cellName.charAt(1) - '1';
	}

	// -----
	// business logic

	/**
	 * A method for reading in data from a CSV file.
	 * @param path The file to read.
	 * @param separator The char used to split up the input, e.g. a comma or a semicolon.
	 * @param starCellName The upper left cell where data from the CSV file should be inserted.
	 * @return Nothing.
	 * @exception IOException If path does not exist.
	 */
	public void readCsv(String path, char separator, String startCellName) throws FileNotFoundException {
		// TODO: implement this
	}

	/**
	 * A method for saving data to a CSV file.
	 * @param path The file to write.
	 * @return Nothing.
	 * @exception IOException If path does not exist.
	 */
	public void saveCsv(String path) throws FileNotFoundException {
		PrintWriter out = new PrintWriter(path);

		for (Cell[] row : cells) {
			for (Cell cell : row) {
				if (!cell.getFormula().isEmpty())
					out.print("=" + cell.getFormula());
				else
					out.print(cell.getValue());

				if (cell != row[cells.length-1])
					out.print(",");
			}
			out.println();
		}

		out.close();
	}

	/**
	 * This method does the actual evaluation/calcluation of a specific cell
	 * @param cellName the name of the cell to be evaluated
	 * @return Nothing.
	 */
	private void evaluateCell(int row, int col) {
		String formula = cells[row][col].getFormula();
		String result = "";

		if (formula.startsWith("SUMME("))  // e.g. SUMME(A3:A8)
			result = "" + sum(formula.substring(6, 8), formula.substring(9, 11));  // TODO adapt to cells with two digits
		else if (formula.startsWith("PRODUKT("))  // e.g. PRODUKT(A3:B9)
			result = "TODO"; // TODO
		else if (formula.startsWith("MITTELWERT("))  // e.g. MITTELWERT(A3:A5)
			result = "TODO"; // TODO
		else if (formula.startsWith("STABW("))  // e.g. STABW(C6:D8) -> Standardabweichung
			result = "TODO"; // TODO
		else if (formula.startsWith("MIN("))  // e.g. MIN(C13:H13) -> größter Wert
			result = "TODO"; // TODO
		else if (formula.startsWith("MAX("))  // e.g. MAX(A1:A10) -> Standardabweichung
			result = "TODO"; // TODO
		else if (!formula.isEmpty())
			result = "" + calculate(formula);

		cells[row][col].setValue("" + result);
	}

	/**
	 * Method for calculating the sum of a rectangular block of cells, such as from A1 to B3.
	 * @param startCellName The name of the cell in the upper left corner of the rectangle.
	 * @param endCellName The name of the cell in the lower right corner of the rectangle.
	 * @return The sum calculated.
	 */
	private long sum(String startCellName, String endCellName) {
		// TODO implement

		return 0;
	}

	/**
	 * This method calculates the result of a "normal" algebraic expression. It only needs to support
	 * expressions like =B4 or =2+A3-B2, i.e. only with int numbers and other cells and with plus,
	 * minus, times, split only. An expression always starts with either a number or a cell name. If it 
	 * continues, it is guaranteed that this is followed by an operator and either a number or a 
	 * cell name again. It is NOT required to implement dot before dash or parentheses in formulas.
	 * @param formula The expression to be evaluated.
	 * @return The result calculated.
	 */
	private long calculate(String formula) {
		Matcher m = Pattern.compile("([A-Z][0-9]*)|[-\\+\\*/]|[0-9]*").matcher(formula);

		long res = 0;

		// TODO implement

		// uncomment the following to see an example how the elements of a formula can be accessed
		while (m.find()) {        // m.find() must always be used before m.group()
			String s = m.group();
			if (!s.isEmpty()) {
				System.out.println(s);
			}
		}

		return res;
	}

	// -----

	public String toString() {
		StringBuilder sb = new StringBuilder();

		sb.append("    ");
		for (int i = 0; i < cells.length; i++) {
			sb.append("  " + (char)('A'+ i) + "  | ");
		}

		int rc = 1;
		for (Cell[] r : cells) {
			sb.append(System.lineSeparator());
			sb.append(String.format("%2s", rc++) + ": ");

			for (Cell c : r) {
				sb.append(c + " | ");
			}

		}
		return sb.toString();
	}

}