package org.simantics.maps.sg;

import java.util.Locale;

/**
 * @author Tuukka Lehtonen
 */
class Formatting {

    private static final transient double EPSILON = 0.01;

    private static final transient double TRIM_THRESHOLD_MAX_VALUE = Math.pow(10, 4);

    private static final transient String[] SI_UNIT_LARGE_PREFIXES = {
        "k", "M", "G", "T", "P", "E", "Z", "Y"
    };

    public static enum FormatMode {
        LIMIT_DIGITS,
        LIMIT_DECIMALS,
    }

    public static String formatValue(double value, int max, boolean removeTrailingZeros, FormatMode formatMode) {
        return formatValue(value, max, removeTrailingZeros, formatMode, TRIM_THRESHOLD_MAX_VALUE);
    }

    public static String formatValue(double value, int max, boolean removeTrailingZeros, FormatMode formatMode, double trimThresholdMaxValue) {
        return formatValue(value, max, removeTrailingZeros, formatMode, trimThresholdMaxValue, true);
    }

    public static String formatValue(double value, int max, boolean removeTrailingZeros, FormatMode formatMode, double trimThresholdMaxValue, boolean trimLargeValues) {
        //System.out.println("formatValue(" + value + ", " + max + ", " + removeTrailingZeros + ", " + formatMode + ", " + trimThresholdMaxValue + ", " + trimLargeValues + ")");
        int allowedDecimals = max;
        if (formatMode == FormatMode.LIMIT_DIGITS) {
            int magnitude = (int) Math.ceil(Math.log10(Math.abs(value)));
            //System.out.println("magnitude(" + value + "): " + magnitude);
            allowedDecimals -= Math.abs(magnitude);
            if (allowedDecimals < 0)
                allowedDecimals = 0;
            //System.out.println("allowedDecimals: " + allowedDecimals);
        }

        String valueStr = String.format(Locale.US, "%." + allowedDecimals + "f", value);
        if (allowedDecimals > 0) {
            if (removeTrailingZeros) {
                for (int trunc = valueStr.length() - 1; trunc > 0; --trunc) {
                    char ch = valueStr.charAt(trunc);
                    if (ch == '.') {
                        valueStr = valueStr.substring(0, trunc);
                        break;
                    }
                    if (ch != '0') {
                        valueStr = valueStr.substring(0, trunc + 1);
                        break;
                    }
                }
            }
            if (Math.abs(value) + EPSILON > trimThresholdMaxValue) {
                // Cut anything beyond a possible decimal dot out since they
                // should not show anyway. This is a complete hack that tries to
                // circumvent floating-point inaccuracy problems.
                int dotIndex = valueStr.lastIndexOf('.');
                if (dotIndex > -1) {
                    valueStr = valueStr.substring(0, dotIndex);
                }
            }
        }

        if (valueStr.equals("-0"))
            valueStr = "0";

        if (trimLargeValues) {
            double trimValue = value;
            if (Math.abs(value) + EPSILON >= trimThresholdMaxValue) {
                for (int i = 0; Math.abs(trimValue) + EPSILON >= trimThresholdMaxValue; ++i) {
                    double trim = trimValue / 1000;
                    if (Math.abs(trim) - EPSILON < trimThresholdMaxValue) {
                        valueStr = valueStr.substring(0, valueStr.length() - (i + 1) * 3);
                        valueStr += SI_UNIT_LARGE_PREFIXES[i];
                        break;
                    }
                    trimValue = trim;
                }
            }
        }

        //System.out.println("formatted result: " + valueStr);

        return valueStr;
    }

}