package ar.com.hjg.pngj;

import java.util.HashMap;

/**
 * Internal PNG predictor filter type
 * 
 * Negative values are pseudo types, actually global strategies for writing,
 * that (can) result on different real filters
 * for different rows
 */
public enum FilterType {
	/**
	 * No filter.
	 */
	FILTER_NONE(0),
	/**
	 * SUB filter (uses same row)
	 */
	FILTER_SUB(1),
	/**
	 * UP filter (uses previous row)
	 */
	FILTER_UP(2),
	/**
	 * AVERAGE filter
	 */
	FILTER_AVERAGE(3),
	/**
	 * PAETH predictor
	 */
	FILTER_PAETH(4),
	/**
	 * Default strategy: select one of the standard filters depending on global
	 * image parameters
	 */
	FILTER_DEFAULT(-1),
	/**
	 * @deprecated use #FILTER_ADAPTIVE_FAST
	 */
	FILTER_AGGRESSIVE(-2),
	/**
	 * @deprecated use #FILTER_ADAPTIVE_MEDIUM or #FILTER_ADAPTIVE_FULL
	 */
	FILTER_VERYAGGRESSIVE(-4),
	/**
	 * Adaptative strategy, sampling each row, or almost
	 */
	FILTER_ADAPTIVE_FULL(-4),
	/**
	 * Adaptive strategy, skippping some rows
	 */
	FILTER_ADAPTIVE_MEDIUM(-3), // samples about 1/4 row
	/**
	 * Adaptative strategy, skipping many rows - more speed
	 */
	FILTER_ADAPTIVE_FAST(-2), // samples each 8 or 16 rows
	/**
	 * Experimental
	 */
	FILTER_SUPER_ADAPTIVE(-10), //
	/**
	 * Preserves the filter passed in original row.
	 */
	FILTER_PRESERVE(-40),
	/**
	 * Uses all fiters, one for lines, cyciclally. Only for tests.
	 */
	FILTER_CYCLIC(-50),
	/**
	 * Not specified, placeholder for unknown or NA filters.
	 */
	FILTER_UNKNOWN(-100);

	public final int val;

	private FilterType(int val) {
		this.val = val;
	}

	private static HashMap<Integer, FilterType> byVal;

	static {
		byVal = new HashMap<Integer, FilterType>();
		for (FilterType ft : values()) {
			byVal.put(ft.val, ft);
		}
	}

	public static FilterType getByVal(int i) {
		return byVal.get(i);
	}

	/** only considers standard */
	public static boolean isValidStandard(int i) {
		return i >= 0 && i <= 4;
	}

	public static boolean isValidStandard(FilterType fy) {
		return fy != null && isValidStandard(fy.val);
	}

	public static boolean isAdaptive(FilterType fy) {
		return fy.val <= -2 && fy.val >= -4;
	}

	/**
	 * Returns all "standard" filters
	 */
	public static FilterType[] getAllStandard() {
		return new FilterType[] { FILTER_NONE, FILTER_SUB, FILTER_UP, FILTER_AVERAGE, FILTER_PAETH };
	}

	public static FilterType[] getAllStandardNoneLast() {
		return new FilterType[] { FILTER_SUB, FILTER_UP, FILTER_AVERAGE, FILTER_PAETH, FILTER_NONE };
	}

	public static FilterType[] getAllStandardExceptNone() {
		return new FilterType[] { FILTER_SUB, FILTER_UP, FILTER_AVERAGE, FILTER_PAETH };
	}

	static FilterType[] getAllStandardForFirstRow() {
		return new FilterType[] { FILTER_SUB, FILTER_NONE };
	}

}