package org.codehaus.jackson.map.util;

import java.text.DateFormat;
import java.text.FieldPosition;
import java.text.ParseException;
import java.text.ParsePosition;
import java.text.SimpleDateFormat;
import java.util.*;

import org.codehaus.jackson.io.NumberInput;

/**
 * Default {@link DateFormat} implementation used by standard Date
 * serializers and deserializers. For serialization defaults to using
 * an ISO-8601 compliant format (format String "yyyy-MM-dd'T'HH:mm:ss.SSSZ")
 * and for deserialization, both ISO-8601 and RFC-1123.
 */
@SuppressWarnings("serial")
public class StdDateFormat
    extends DateFormat
{
    /* TODO !!! 24-Nov-2009, tatu: Need to rewrite this class soon:
     * JDK date parsing is awfully brittle, and ISO-8601 is quite
     * permissive. The two don't mix, need to write a better one.
     */

    /**
     * Defines a commonly used date format that conforms
     * to ISO-8601 date formatting standard, when it includes basic undecorated
     * timezone definition
     */
    protected final static String DATE_FORMAT_STR_ISO8601 = "yyyy-MM-dd'T'HH:mm:ss.SSSZ";

    /**
     * Same as 'regular' 8601, but handles 'Z' as an alias for "+0000"
     * (or "GMT")
     */
    protected final static String DATE_FORMAT_STR_ISO8601_Z = "yyyy-MM-dd'T'HH:mm:ss.SSS'Z'";

    /**
     * ISO-8601 with just the Date part, no time
     *
     * @since 1.3.1
     */
    protected final static String DATE_FORMAT_STR_PLAIN = "yyyy-MM-dd";

    /**
     * This constant defines the date format specified by
     * RFC 1123.
     */
    protected final static String DATE_FORMAT_STR_RFC1123 = "EEE, dd MMM yyyy HH:mm:ss zzz";

    /**
     * For error messages we'll also need a list of all formats.
     */
    protected final static String[] ALL_FORMATS = new String[] {
        DATE_FORMAT_STR_ISO8601,
        DATE_FORMAT_STR_ISO8601_Z,
        DATE_FORMAT_STR_RFC1123,
        DATE_FORMAT_STR_PLAIN
    };

    protected final static DateFormat DATE_FORMAT_RFC1123;

    protected final static DateFormat DATE_FORMAT_ISO8601;
    protected final static DateFormat DATE_FORMAT_ISO8601_Z;

    protected final static DateFormat DATE_FORMAT_PLAIN;

    /* Let's construct "blueprint" date format instances: can not be used
     * as is, due to thread-safety issues, but can be used for constructing
     * actual instances more cheaply (avoids re-parsing).
     */
    static {
        /* Another important thing: let's force use of GMT for
         * baseline DataFormat objects
         */
        TimeZone gmt = TimeZone.getTimeZone("GMT");
        DATE_FORMAT_RFC1123 = new SimpleDateFormat(DATE_FORMAT_STR_RFC1123);
        DATE_FORMAT_RFC1123.setTimeZone(gmt);
        DATE_FORMAT_ISO8601 = new SimpleDateFormat(DATE_FORMAT_STR_ISO8601);
        DATE_FORMAT_ISO8601.setTimeZone(gmt);
        DATE_FORMAT_ISO8601_Z = new SimpleDateFormat(DATE_FORMAT_STR_ISO8601_Z);
        DATE_FORMAT_ISO8601_Z.setTimeZone(gmt);
        DATE_FORMAT_PLAIN = new SimpleDateFormat(DATE_FORMAT_STR_PLAIN);
        DATE_FORMAT_PLAIN.setTimeZone(gmt);
    }

    /**
     * A singleton instance can be used for cloning purposes.
     */
    public final static StdDateFormat instance = new StdDateFormat();

    protected transient DateFormat _formatRFC1123;
    protected transient DateFormat _formatISO8601;
    protected transient DateFormat _formatISO8601_z;
    protected transient DateFormat _formatPlain;

    /*
    /**********************************************************
    /* Life cycle, accessing singleton "standard" formats
    /**********************************************************
     */

    public StdDateFormat() { }

    @Override
    public StdDateFormat clone() {
        /* Since we always delegate all work to child DateFormat instances,
         * let's NOT call super.clone(); this is bit unusual, but makes
         * sense here to avoid unnecessary work.
         */
        return new StdDateFormat();
    }

    /**
     * Method for getting the globally shared DateFormat instance
     * that uses GMT timezone and can handle simple ISO-8601
     * compliant date format.
     */
    public static DateFormat getBlueprintISO8601Format() {
        return DATE_FORMAT_ISO8601;
    }

    /**
     * Method for getting a non-shared DateFormat instance
     * that uses specified timezone and can handle simple ISO-8601
     * compliant date format.
     */
    public static DateFormat getISO8601Format(TimeZone tz) {
        DateFormat df = (DateFormat) DATE_FORMAT_ISO8601.clone();
        df.setTimeZone(tz);
        return df;
    }

    /**
     * Method for getting the globally shared DateFormat instance
     * that uses GMT timezone and can handle RFC-1123
     * compliant date format.
     */
    public static DateFormat getBlueprintRFC1123Format() {
        return DATE_FORMAT_RFC1123;
    }


    /**
     * Method for getting a non-shared DateFormat instance
     * that uses specific timezone and can handle RFC-1123
     * compliant date format.
     */
    public static DateFormat getRFC1123Format(TimeZone tz)
    {
        DateFormat df = (DateFormat) DATE_FORMAT_RFC1123.clone();
        df.setTimeZone(tz);
        return df;
    }

    /*
    /**********************************************************
    /* Public API
    /**********************************************************
     */

    @Override
    public Date parse(String dateStr) throws ParseException
    {
        dateStr = dateStr.trim();
        ParsePosition pos = new ParsePosition(0);
        Date result = parse(dateStr, pos);
        if (result != null) {
            return result;
        }

        StringBuilder sb = new StringBuilder();
        for (String f : ALL_FORMATS) {
            if (sb.length() > 0) {
                sb.append("\", \"");
            } else {
                sb.append('"');
            }
            sb.append(f);
        }
        sb.append('"');
        throw new ParseException
            (String.format("Can not parse date \"%s\": not compatible with any of standard forms (%s)",
                           dateStr, sb.toString()), pos.getErrorIndex());
    }

    @Override
    public Date parse(String dateStr, ParsePosition pos)
    {
        if (looksLikeISO8601(dateStr)) { // also includes "plain"
            return parseAsISO8601(dateStr, pos);
        }
        /* 14-Feb-2010, tatu: As per [JACKSON-236], better also
         *   consider "stringified" simple time stamp
         */
        int i = dateStr.length();
        while (--i >= 0) {
            char ch = dateStr.charAt(i);
            if (ch < '0' || ch > '9') break;
        }
        if (i < 0) { // all digits
            if (NumberInput.inLongRange(dateStr, false)) {
                return new Date(Long.parseLong(dateStr));
            }
        }
        // Otherwise, fall back to using RFC 1123
        return parseAsRFC1123(dateStr, pos);
    }

    @Override
    public StringBuffer format(Date date, StringBuffer toAppendTo,
                               FieldPosition fieldPosition)
    {
        if (_formatISO8601 == null) {
            _formatISO8601 = (DateFormat) DATE_FORMAT_ISO8601.clone();
        }
        return _formatISO8601.format(date, toAppendTo, fieldPosition);
    }

    /*
    /**********************************************************
    /* Helper methods
    /**********************************************************
     */

    /**
     * Overridable helper method used to figure out which of supported
     * formats is the likeliest match.
     */
    protected boolean looksLikeISO8601(String dateStr)
    {
        if (dateStr.length() >= 5
            && Character.isDigit(dateStr.charAt(0))
            && Character.isDigit(dateStr.charAt(3))
            && dateStr.charAt(4) == '-'
            ) {
            return true;
        }
        return false;
    }

    protected Date parseAsISO8601(String dateStr, ParsePosition pos)
    {
        /* 21-May-2009, tatu: DateFormat has very strict handling of
         * timezone  modifiers for ISO-8601. So we need to do some scrubbing.
         */

        /* First: do we have "zulu" format ('Z' == "GMT")? If yes, that's
         * quite simple because we already set date format timezone to be
         * GMT, and hence can just strip out 'Z' altogether
         */
        int len = dateStr.length();
        char c = dateStr.charAt(len-1);
        DateFormat df;

        // [JACKSON-200]: need to support "plain" date...
        if (len <= 10 && Character.isDigit(c)) {
           df = _formatPlain;
            if (df == null) {
                df = _formatPlain = (DateFormat) DATE_FORMAT_PLAIN.clone();
            }
        } else if (c == 'Z') {
            df = _formatISO8601_z;
            if (df == null) {
                df = _formatISO8601_z = (DateFormat) DATE_FORMAT_ISO8601_Z.clone();
            }
            // [JACKSON-334]: may be missing milliseconds... if so, add
            if (dateStr.charAt(len-4) == ':') {
                StringBuilder sb = new StringBuilder(dateStr);
                sb.insert(len-1, ".000");
                dateStr = sb.toString();
            }
        } else {
            // Let's see if we have timezone indicator or not...
            if (hasTimeZone(dateStr)) {
                c = dateStr.charAt(len-3);
                if (c == ':') { // remove optional colon
                    // remove colon
                    StringBuilder sb = new StringBuilder(dateStr);
                    sb.delete(len-3, len-2);
                    dateStr = sb.toString();
                } else if (c == '+' || c == '-') { // missing minutes
                    // let's just append '00'
                    dateStr += "00";
                }
                // [JACKSON-334]: may be missing milliseconds... if so, add
                len = dateStr.length();
                // '+0000' (5 chars); should come after '.000' (4 chars) of milliseconds, so:
                c = dateStr.charAt(len-9);
                if (Character.isDigit(c)) {
                    StringBuilder sb = new StringBuilder(dateStr);
                    sb.insert(len-5, ".000");
                    dateStr = sb.toString();
                }
                
                df = _formatISO8601;
                if (_formatISO8601 == null) {
                    df = _formatISO8601 = (DateFormat) DATE_FORMAT_ISO8601.clone();
                }
            } else {
                /* 24-Nov-2009, tatu: Ugh. This is getting pretty
                 *   ugly. Need to rewrite soon!
                 */

                // If not, plain date. Easiest to just patch 'Z' in the end?
                StringBuilder sb = new StringBuilder(dateStr);
                // And possible also millisecond part if missing
                int timeLen = len - dateStr.lastIndexOf('T') - 1;
                if (timeLen <= 8) {
                    sb.append(".000");
                }
                sb.append('Z');
                dateStr = sb.toString();
                df = _formatISO8601_z;
                if (df == null) {
                    df = _formatISO8601_z = (DateFormat) DATE_FORMAT_ISO8601_Z.clone();
                }
            }
        }
        return df.parse(dateStr, pos);
    }

    protected Date parseAsRFC1123(String dateStr, ParsePosition pos)
    {
        if (_formatRFC1123 == null) {
            _formatRFC1123 = (DateFormat) DATE_FORMAT_RFC1123.clone();
        }
        return _formatRFC1123.parse(dateStr, pos);
    }

    private final static boolean hasTimeZone(String str)
    {
        // Only accept "+hh", "+hhmm" and "+hh:mm" (and with minus), so
        int len = str.length();
        if (len >= 6) {
            char c = str.charAt(len-6);
            if (c == '+' || c == '-') return true;
            c = str.charAt(len-5);
            if (c == '+' || c == '-') return true;
            c = str.charAt(len-3);
            if (c == '+' || c == '-') return true;
        }
        return false;
    }
}