/*
 * Copyright 2007 ZXing authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*namespace com.google.zxing.qrcode.decoder {*/

import DecodeHintType from './../../DecodeHintType';
import BitSource from './../../common/BitSource';
import CharacterSetECI from './../../common/CharacterSetECI';
import DecoderResult from './../../common/DecoderResult';
import StringUtils from './../../common/StringUtils';
import Version from './Version';
import ErrorCorrectionLevel from './ErrorCorrectionLevel';
import Mode from './Mode';
import Exception from './../../Exception';
import StringBuilder from './../../util/StringBuilder';
import StringEncoding from './../../util/StringEncoding';

/*import java.io.UnsupportedEncodingException;*/
/*import java.util.ArrayList;*/
/*import java.util.Collection;*/
/*import java.util.List;*/
/*import java.util.Map;*/

/**
 * <p>QR Codes can encode text as bits in one of several modes, and can use multiple modes
 * in one QR Code. This class decodes the bits back into text.</p>
 *
 * <p>See ISO 18004:2006, 6.4.3 - 6.4.7</p>
 *
 * @author Sean Owen
 */
export default class DecodedBitStreamParser {

    /**
     * See ISO 18004:2006, 6.4.4 Table 5
     */
    private static ALPHANUMERIC_CHARS =
        '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ $%*+-./:';
    private static GB2312_SUBSET = 1;

    public static decode(bytes: Uint8Array,
        version: Version,
        ecLevel: ErrorCorrectionLevel,
        hints: Map<DecodeHintType, any>): DecoderResult /*throws FormatException*/ {
        const bits = new BitSource(bytes);
        let result = new StringBuilder();
        const byteSegments = new Array<Uint8Array>(); // 1
        // TYPESCRIPTPORT: I do not use constructor with size 1 as in original Java means capacity and the array length is checked below
        let symbolSequence = -1;
        let parityData = -1;

        try {
            let currentCharacterSetECI: CharacterSetECI = null;
            let fc1InEffect: boolean = false;
            let mode: Mode;
            do {
                // While still another segment to read...
                if (bits.available() < 4) {
                    // OK, assume we're done. Really, a TERMINATOR mode should have been recorded here
                    mode = Mode.TERMINATOR;
                } else {
                    const modeBits = bits.readBits(4);
                    mode = Mode.forBits(modeBits); // mode is encoded by 4 bits
                }
                switch (mode) {
                    case Mode.TERMINATOR:
                        break;
                    case Mode.FNC1_FIRST_POSITION:
                    case Mode.FNC1_SECOND_POSITION:
                        // We do little with FNC1 except alter the parsed result a bit according to the spec
                        fc1InEffect = true;
                        break;
                    case Mode.STRUCTURED_APPEND:
                        if (bits.available() < 16) {
                            throw new Exception(Exception.FormatException);
                        }
                        // sequence number and parity is added later to the result metadata
                        // Read next 8 bits (symbol sequence #) and 8 bits (data: parity), then continue
                        symbolSequence = bits.readBits(8);
                        parityData = bits.readBits(8);
                        break;
                    case Mode.ECI:
                        // Count doesn't apply to ECI
                        const value = DecodedBitStreamParser.parseECIValue(bits);
                        currentCharacterSetECI = CharacterSetECI.getCharacterSetECIByValue(value);
                        if (currentCharacterSetECI === null) {
                            throw new Exception(Exception.FormatException);
                        }
                        break;
                    case Mode.HANZI:
                        // First handle Hanzi mode which does not start with character count
                        // Chinese mode contains a sub set indicator right after mode indicator
                        const subset = bits.readBits(4);
                        const countHanzi = bits.readBits(mode.getCharacterCountBits(version));
                        if (subset === DecodedBitStreamParser.GB2312_SUBSET) {
                            DecodedBitStreamParser.decodeHanziSegment(bits, result, countHanzi);
                        }
                        break;
                    default:
                        // "Normal" QR code modes:
                        // How many characters will follow, encoded in this mode?
                        const count = bits.readBits(mode.getCharacterCountBits(version));
                        switch (mode) {
                            case Mode.NUMERIC:
                                DecodedBitStreamParser.decodeNumericSegment(bits, result, count);
                                break;
                            case Mode.ALPHANUMERIC:
                                DecodedBitStreamParser.decodeAlphanumericSegment(bits, result, count, fc1InEffect);
                                break;
                            case Mode.BYTE:
                                DecodedBitStreamParser.decodeByteSegment(bits, result, count, currentCharacterSetECI, byteSegments, hints);
                                break;
                            case Mode.KANJI:
                                DecodedBitStreamParser.decodeKanjiSegment(bits, result, count);
                                break;
                            default:
                                throw new Exception(Exception.FormatException);
                        }
                        break;
                }
            } while (mode !== Mode.TERMINATOR);
        } catch (iae/*: IllegalArgumentException*/) {
            // from readBits() calls
            throw new Exception(Exception.FormatException);
        }

        return new DecoderResult(bytes,
            result.toString(),
            byteSegments.length === 0 ? null : byteSegments,
            ecLevel === null ? null : ecLevel.toString(),
            symbolSequence,
            parityData);
    }

    /**
     * See specification GBT 18284-2000
     */
    private static decodeHanziSegment(bits: BitSource,
        result: StringBuilder,
        count: number /*int*/): void /*throws FormatException*/ {
        // Don't crash trying to read more bits than we have available.
        if (count * 13 > bits.available()) {
            throw new Exception(Exception.FormatException);
        }

        // Each character will require 2 bytes. Read the characters as 2-byte pairs
        // and decode as GB2312 afterwards
        const buffer = new Uint8Array(2 * count);
        let offset = 0;
        while (count > 0) {
            // Each 13 bits encodes a 2-byte character
            const twoBytes = bits.readBits(13);
            let assembledTwoBytes = (((twoBytes / 0x060) << 8) & 0xFFFFFFFF) | (twoBytes % 0x060);
            if (assembledTwoBytes < 0x003BF) {
                // In the 0xA1A1 to 0xAAFE range
                assembledTwoBytes += 0x0A1A1;
            } else {
                // In the 0xB0A1 to 0xFAFE range
                assembledTwoBytes += 0x0A6A1;
            }
            buffer[offset] = /*(byte) */((assembledTwoBytes >> 8) & 0xFF);
            buffer[offset + 1] = /*(byte) */(assembledTwoBytes & 0xFF);
            offset += 2;
            count--;
        }

        try {
            result.append(StringEncoding.decode(buffer, StringUtils.GB2312));
            // TYPESCRIPTPORT: TODO: implement GB2312 decode. StringView from MDN could be a starting point
        } catch (ignored/*: UnsupportedEncodingException*/) {
            throw new Exception(Exception.FormatException, ignored);
        }
    }

    private static decodeKanjiSegment(bits: BitSource,
        result: StringBuilder,
        count: number /*int*/): void /*throws FormatException*/ {
        // Don't crash trying to read more bits than we have available.
        if (count * 13 > bits.available()) {
            throw new Exception(Exception.FormatException);
        }

        // Each character will require 2 bytes. Read the characters as 2-byte pairs
        // and decode as Shift_JIS afterwards
        const buffer = new Uint8Array(2 * count);
        let offset = 0;
        while (count > 0) {
            // Each 13 bits encodes a 2-byte character
            const twoBytes = bits.readBits(13);
            let assembledTwoBytes = (((twoBytes / 0x0C0) << 8) & 0xFFFFFFFF) | (twoBytes % 0x0C0);
            if (assembledTwoBytes < 0x01F00) {
                // In the 0x8140 to 0x9FFC range
                assembledTwoBytes += 0x08140;
            } else {
                // In the 0xE040 to 0xEBBF range
                assembledTwoBytes += 0x0C140;
            }
            buffer[offset] = /*(byte) */(assembledTwoBytes >> 8);
            buffer[offset + 1] = /*(byte) */assembledTwoBytes;
            offset += 2;
            count--;
        }
        // Shift_JIS may not be supported in some environments:
        try {
            result.append(StringEncoding.decode(buffer, StringUtils.SHIFT_JIS));
            // TYPESCRIPTPORT: TODO: implement SHIFT_JIS decode. StringView from MDN could be a starting point
        } catch (ignored/*: UnsupportedEncodingException*/) {
            throw new Exception(Exception.FormatException, ignored);
        }
    }

    private static decodeByteSegment(bits: BitSource,
        result: StringBuilder,
        count: number /*int*/,
        currentCharacterSetECI: CharacterSetECI,
        byteSegments: Uint8Array[],
        hints: Map<DecodeHintType, any>): void /*throws FormatException*/ {
        // Don't crash trying to read more bits than we have available.
        if (8 * count > bits.available()) {
            throw new Exception(Exception.FormatException);
        }

        const readBytes = new Uint8Array(count);
        for (let i = 0; i < count; i++) {
            readBytes[i] = /*(byte) */bits.readBits(8);
        }
        let encoding: string;
        if (currentCharacterSetECI === null) {
            // The spec isn't clear on this mode; see
            // section 6.4.5: t does not say which encoding to assuming
            // upon decoding. I have seen ISO-8859-1 used as well as
            // Shift_JIS -- without anything like an ECI designator to
            // give a hint.
            encoding = StringUtils.guessEncoding(readBytes, hints);
        } else {
            encoding = currentCharacterSetECI.getName();
        }
        try {
            result.append(StringEncoding.decode(readBytes, encoding));
        } catch (ignored/*: UnsupportedEncodingException*/) {
            throw new Exception(Exception.FormatException, ignored);
        }
        byteSegments.push(readBytes);
    }

    private static toAlphaNumericChar(value: number /*int*/): string /*throws FormatException*/ {
        if (value >= DecodedBitStreamParser.ALPHANUMERIC_CHARS.length) {
            throw new Exception(Exception.FormatException);
        }
        return DecodedBitStreamParser.ALPHANUMERIC_CHARS[value];
    }

    private static decodeAlphanumericSegment(bits: BitSource,
        result: StringBuilder,
        count: number /*int*/,
        fc1InEffect: boolean): void /*throws FormatException*/ {
        // Read two characters at a time
        const start = result.length();
        while (count > 1) {
            if (bits.available() < 11) {
                throw new Exception(Exception.FormatException);
            }
            const nextTwoCharsBits = bits.readBits(11);
            result.append(DecodedBitStreamParser.toAlphaNumericChar(Math.floor(nextTwoCharsBits / 45)));
            result.append(DecodedBitStreamParser.toAlphaNumericChar(nextTwoCharsBits % 45));
            count -= 2;
        }
        if (count === 1) {
            // special case: one character left
            if (bits.available() < 6) {
                throw new Exception(Exception.FormatException);
            }
            result.append(DecodedBitStreamParser.toAlphaNumericChar(bits.readBits(6)));
        }
        // See section 6.4.8.1, 6.4.8.2
        if (fc1InEffect) {
            // We need to massage the result a bit if in an FNC1 mode:
            for (let i = start; i < result.length(); i++) {
                if (result.charAt(i) === '%') {
                    if (i < result.length() - 1 && result.charAt(i + 1) === '%') {
                        // %% is rendered as %
                        result.deleteCharAt(i + 1);
                    } else {
                        // In alpha mode, % should be converted to FNC1 separator 0x1D
                        result.setCharAt(i, String.fromCharCode(0x1D));
                    }
                }
            }
        }
    }

    private static decodeNumericSegment(bits: BitSource,
        result: StringBuilder,
        count: number /*int*/): void /*throws FormatException*/ {
        // Read three digits at a time
        while (count >= 3) {
            // Each 10 bits encodes three digits
            if (bits.available() < 10) {
                throw new Exception(Exception.FormatException);
            }
            const threeDigitsBits = bits.readBits(10);
            if (threeDigitsBits >= 1000) {
                throw new Exception(Exception.FormatException);
            }
            result.append(DecodedBitStreamParser.toAlphaNumericChar(Math.floor(threeDigitsBits / 100)));
            result.append(DecodedBitStreamParser.toAlphaNumericChar(Math.floor(threeDigitsBits / 10) % 10));
            result.append(DecodedBitStreamParser.toAlphaNumericChar(threeDigitsBits % 10));
            count -= 3;
        }
        if (count === 2) {
            // Two digits left over to read, encoded in 7 bits
            if (bits.available() < 7) {
                throw new Exception(Exception.FormatException);
            }
            const twoDigitsBits = bits.readBits(7);
            if (twoDigitsBits >= 100) {
                throw new Exception(Exception.FormatException);
            }
            result.append(DecodedBitStreamParser.toAlphaNumericChar(Math.floor(twoDigitsBits / 10)));
            result.append(DecodedBitStreamParser.toAlphaNumericChar(twoDigitsBits % 10));
        } else if (count === 1) {
            // One digit left over to read
            if (bits.available() < 4) {
                throw new Exception(Exception.FormatException);
            }
            const digitBits = bits.readBits(4);
            if (digitBits >= 10) {
                throw new Exception(Exception.FormatException);
            }
            result.append(DecodedBitStreamParser.toAlphaNumericChar(digitBits));
        }
    }

    private static parseECIValue(bits: BitSource): number /*int*/ /*throws FormatException*/ {
        const firstByte = bits.readBits(8);
        if ((firstByte & 0x80) === 0) {
            // just one byte
            return firstByte & 0x7F;
        }
        if ((firstByte & 0xC0) === 0x80) {
            // two bytes
            const secondByte = bits.readBits(8);
            return (((firstByte & 0x3F) << 8) & 0xFFFFFFFF) | secondByte;
        }
        if ((firstByte & 0xE0) === 0xC0) {
            // three bytes
            const secondThirdBytes = bits.readBits(16);
            return (((firstByte & 0x1F) << 16) & 0xFFFFFFFF) | secondThirdBytes;
        }
        throw new Exception(Exception.FormatException);
    }

}

function Uint8ArrayToString(a: Uint8Array): string {
    const CHUNK_SZ = 0x8000;
    const c = new StringBuilder();
    for (let i = 0, length = a.length; i < length; i += CHUNK_SZ) {
        c.append(String.fromCharCode.apply(null, a.subarray(i, i + CHUNK_SZ)));
    }
    return c.toString();
}