/*
 * Copyright (C) 2013-2016 Adrian Ulrich <adrian@blinkenlights.ch>
 * Copyright (C) 2017-2018 Google Inc.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */

package github.daneren2005.dsub.util.tags;

import java.io.IOException;
import java.io.RandomAccessFile;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Enumeration;



public class ID3v2File extends Common {
	private static final int ID3_ENC_LATIN   = 0x00;
	private static final int ID3_ENC_UTF16   = 0x01;
	private static final int ID3_ENC_UTF16BE = 0x02;
	private static final int ID3_ENC_UTF8    = 0x03;
	private static final HashMap<String, String> sOggNames;
	static {
		// ID3v2.3 -> ogg mapping
		sOggNames = new HashMap<String, String>();
		sOggNames.put("TIT2", "TITLE");
		sOggNames.put("TALB", "ALBUM");
		sOggNames.put("TPE1", "ARTIST");
		sOggNames.put("TPE2", "ALBUMARTIST");
		sOggNames.put("TYER", "YEAR");
		sOggNames.put("TPOS", "DISCNUMBER");
		sOggNames.put("TRCK", "TRACKNUMBER");
		sOggNames.put("TCON", "GENRE");
		sOggNames.put("TCOM", "COMPOSER");
		// ID3v2.2 3-character names
		sOggNames.put("TT2", "TITLE");
		sOggNames.put("TAL", "ALBUM");
		sOggNames.put("TP1", "ARTIST");
		sOggNames.put("TP2", "ALBUMARTIST");
		sOggNames.put("TYE", "YEAR");
		sOggNames.put("TRK", "TRACKNUMBER");
		sOggNames.put("TCO", "GENRE");
		sOggNames.put("TCM", "COMPOSER");
	}

	// Holds a key-value pair
	private class TagItem {
		String key;
		String value;
		public TagItem(String key, String value) {
			this.key = key;
			this.value = value;
		}
	}

	public ID3v2File() {
	}

	public HashMap getTags(RandomAccessFile s) throws IOException {
		HashMap tags = new HashMap();

		final int v2hdr_len = 10;
		byte[] v2hdr = new byte[v2hdr_len];

		// read the whole 10 byte header into memory
		s.seek(0);
		s.read(v2hdr);

		int v3major = (b2be32(v2hdr, 0)) & 0xFF;   // swapped ID3\04 -> ver. ist the first byte
		int v3minor = (b2be32(v2hdr, 1)) & 0xFF;   // minor version, not used by us.
		int v3flags = (b2be32(v2hdr, 2)) & 0xFF;   // flags such as extended headers.
		int v3len   = (b2be32(v2hdr, 6));          // total size EXCLUDING the this 10 byte header
		v3len       = unsyncsafe(v3len);

		// In 2.4, bit #6 indicates whether or not this file has an extended header
		boolean flag_ext_hdr = v3major >= 4 && (v3flags & (1 << 6)) != 0;

		if (flag_ext_hdr) {
			// The extended header is at least 6 bytes:
			// * 4 byts of size
			// * 1 byte numflags
			// * 1 byte extended flags
			byte[] exthdr = new byte[6];
			long pos = s.getFilePointer();
			s.read(exthdr);

			// we got the length, so we can seek to the header end.
			int extlen = (b2be32(exthdr, 0));
			s.seek(pos + extlen);
		}

		// we should already be at the first frame
		// so we can start the parsing right now
		tags = parse_v3_frames(s, v3len, v3major);
		tags.put("_hdrlen", v3len+v2hdr_len);
		return tags;
	}

	/*
	**  converts syncsafe integer to Java integer
	*/
	private int unsyncsafe(int x) {
		x     = ((x & 0x7f000000) >> 3) |
				((x & 0x007f0000) >> 2) |
				((x & 0x00007f00) >> 1) |
				((x & 0x0000007f) >> 0) ;
		return x;
	}

	/**
	 * Calculates the frame length baased on the frame size and the
	 */
	private int calculateFrameLength(byte[] frame, int offset, int v3major) {
		// ID3v2 (aka ID3v2.2) had a 3-byte unencoded length field.
		if (v3major < 3) {
			return (frame[offset] << 16) + (frame[offset+1] << 8) + frame[offset+2];
		}
		int rawlen = b2be32(frame, offset);
		// Encoders prior ID3v2.4 did not encode the frame length
		if (v3major < 4) {
			return rawlen;
		}
		return unsyncsafe(rawlen);
	}

	/* Parses all ID3v2 frames at the current position up until payload_len
	** bytes were read
	*/
	public HashMap parse_v3_frames(RandomAccessFile s, long payload_len, int v3major) throws IOException {
		HashMap tags = new HashMap();
		// ID3v2 (aka ID3v2.2) had a 6-byte header of a 3-byte name and a 3-byte length.
		// ID3v2.3 increased the header size to 10 bytes, with a 4-byte name and a 4-byte length
		int namelen = (v3major >= 3 ? 4 : 3);
		int headerlen = (v3major >= 3 ? 10 : 6);
		byte[] frame   = new byte[headerlen];
		long bread     = 0;                      // total amount of read bytes

		while(bread < payload_len) {
			bread += s.read(frame);
			String framename = new String(frame, 0, namelen);
			int slen = calculateFrameLength(frame, namelen, v3major);
			/* Abort on silly sizes */
			long bytesRemaining = payload_len - bread;
			if(slen < 1 || slen > bytesRemaining)
				break;

			byte[] xpl = new byte[slen];
			bread += s.read(xpl);

			if(framename.substring(0,1).equals("T")) {
				TagItem nti = normalizeTaginfo(framename, xpl);
				if (nti.key.length() > 0) {
					for (TagItem ti : splitTagPayload(nti)) {
						addTagEntry(tags, ti.key, ti.value);
					}
				}
			}
			else if(framename.equals("RVA2")) {
				//
			}

		}
		return tags;
	}

	/* Split null-separated tags into individual elements */
	private ArrayList<TagItem> splitTagPayload(TagItem in) {
		ArrayList res = new ArrayList<TagItem>();
		int i = 0;

		if (sOggNames.containsValue(in.key)) {
			// Only try to split if there are more than two chars and the string does NOT look UTF16 encoded.
			if (in.value.length() >= 2 && in.value.charAt(0) != 0 && in.value.charAt(1) != 0) {
				for (String item : in.value.split("\0")) {
					if (item.length() > 0) { // do not add empty items, avoids thrashing if the string is zero padded.
						res.add(new TagItem(in.key, item));
					}
					i++;
				}
			}
		}

		if (i == 0) {
			res.add(in);
		}
		return res;
	}

	/* Converts ID3v2 sillyframes to OggNames */
	private TagItem normalizeTaginfo(String k, byte[] v) {
		TagItem ti = new TagItem("", "");
		if(sOggNames.containsKey(k)) {
			/* A normal, known key: translate into Ogg-Frame name */
			ti.key = (String)sOggNames.get(k);
			ti.value = getDecodedString(v);
		}
		else if(k.equals("TXXX")) {
			/* A freestyle field, ieks! */
			String txData[] = getDecodedString(v).split(Character.toString('\0'), 2);
			/* Check if we got replaygain info in key\0value style */
			if(txData.length == 2 && txData[0].matches("^(?i)REPLAYGAIN_(ALBUM|TRACK)_GAIN$")) {
				ti.key = txData[0].toUpperCase(); /* some tagwriters use lowercase for this */
				ti.value = txData[1];
			}
		}

		return ti;
	}

	/* Converts a raw byte-stream text into a java String */
	private String getDecodedString(byte[] raw) {
		int encid = raw[0] & 0xFF;
		int skip  = 1;
		String cs = "ISO-8859-1";
		String rv  = "";
		try {
			switch (encid) {
				case ID3_ENC_UTF8:
					cs = "UTF-8";
					break;
				case ID3_ENC_UTF16BE:
					cs = "UTF-16BE";
					skip = 3;
					break;
				case ID3_ENC_UTF16:
					cs = "UTF-16";
					if (raw.length > 4) {
						if ((raw[1]&0xFF) == 0xFE && (raw[2]&0XFF) == 0xFF && (raw[3]&0xFF) == 0x00 && (raw[4]&0xFF) == 0x00) {
							// buggy tag written by lame?!
							raw[3] = raw[2];
							raw[4] = raw[1];
							skip = 3;
						} else if((raw[1]&0xFF) == 0xFF && (raw[2]&0XFF) == 0x00 && (raw[3]&0xFF) == 0xFE) {
							// ?!, but seen in the wild
							raw[2] = raw[1];
							skip = 2;
						}
					}
					break;
				case ID3_ENC_LATIN:
				default:
					// uses defaults
			}

			rv = new String(raw, skip, raw.length-skip, cs);

			if (rv.length() > 0 && rv.substring(rv.length()-1).equals("\0")) {
				// SOME tag writers seem to null terminate strings, some don't...
				rv = rv.substring(0, rv.length()-1);
			}
		} catch(Exception e) {}
		return rv;
	}

}