/*
 * Copyright 2008 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.
 */

using System;
using System.Collections.Generic;
using System.Text;

using ZXing.Common;

namespace ZXing.OneD
{
    /// <summary>
    ///   <p>Encapsulates functionality and implementation that is common to UPC and EAN families
    /// of one-dimensional barcodes.</p>
    ///   <author>dswitkin@google.com (Daniel Switkin)</author>
    ///   <author>Sean Owen</author>
    ///   <author>alasdair@google.com (Alasdair Mackintosh)</author>
    /// </summary>
    public abstract class UPCEANReader : OneDReader
    {

        // These two values are critical for determining how permissive the decoding will be.
        // We've arrived at these values through a lot of trial and error. Setting them any higher
        // lets false positives creep in quickly.
        private static readonly int MAX_AVG_VARIANCE = (int)(PATTERN_MATCH_RESULT_SCALE_FACTOR * 0.48f);
        private static readonly int MAX_INDIVIDUAL_VARIANCE = (int)(PATTERN_MATCH_RESULT_SCALE_FACTOR * 0.7f);

        /// <summary>
        /// Start/end guard pattern.
        /// </summary>
        internal static int[] START_END_PATTERN = { 1, 1, 1, };

        /// <summary>
        /// Pattern marking the middle of a UPC/EAN pattern, separating the two halves.
        /// </summary>
        internal static int[] MIDDLE_PATTERN = { 1, 1, 1, 1, 1 };

        /// <summary>
        /// end guard pattern.
        /// </summary>
        internal static int[] END_PATTERN = { 1, 1, 1, 1, 1, 1 };

        /// <summary>
        /// "Odd", or "L" patterns used to encode UPC/EAN digits.
        /// </summary>
        internal static int[][] L_PATTERNS = {
                                              new[] {3, 2, 1, 1}, // 0
                                              new[] {2, 2, 2, 1}, // 1
                                              new[] {2, 1, 2, 2}, // 2
                                              new[] {1, 4, 1, 1}, // 3
                                              new[] {1, 1, 3, 2}, // 4
                                              new[] {1, 2, 3, 1}, // 5
                                              new[] {1, 1, 1, 4}, // 6
                                              new[] {1, 3, 1, 2}, // 7
                                              new[] {1, 2, 1, 3}, // 8
                                              new[] {3, 1, 1, 2} // 9
                                           };

        /// <summary>
        /// As above but also including the "even", or "G" patterns used to encode UPC/EAN digits.
        /// </summary>
        internal static int[][] L_AND_G_PATTERNS;

        static UPCEANReader()
        {
            L_AND_G_PATTERNS = new int[20][];
            Array.Copy(L_PATTERNS, 0, L_AND_G_PATTERNS, 0, 10);
            for (int i = 10; i < 20; i++)
            {
                int[] widths = L_PATTERNS[i - 10];
                int[] reversedWidths = new int[widths.Length];
                for (int j = 0; j < widths.Length; j++)
                {
                    reversedWidths[j] = widths[widths.Length - j - 1];
                }
                L_AND_G_PATTERNS[i] = reversedWidths;
            }
        }

        private readonly StringBuilder decodeRowStringBuffer;
        private readonly UPCEANExtensionSupport extensionReader;
        private readonly EANManufacturerOrgSupport eanManSupport;

        /// <summary>
        /// Initializes a new instance of the <see cref="UPCEANReader"/> class.
        /// </summary>
        protected UPCEANReader()
        {
            decodeRowStringBuffer = new StringBuilder(20);
            extensionReader = new UPCEANExtensionSupport();
            eanManSupport = new EANManufacturerOrgSupport();
        }

        internal static int[] findStartGuardPattern(BitArray row)
        {
            bool foundStart = false;
            int[] startRange = null;
            int nextStart = 0;
            int[] counters = new int[START_END_PATTERN.Length];
            while (!foundStart)
            {
                for (int idx = 0; idx < START_END_PATTERN.Length; idx++)
                    counters[idx] = 0;
                startRange = findGuardPattern(row, nextStart, false, START_END_PATTERN, counters);
                if (startRange == null)
                    return null;
                int start = startRange[0];
                nextStart = startRange[1];
                // Make sure there is a quiet zone at least as big as the start pattern before the barcode.
                // If this check would run off the left edge of the image, do not accept this barcode,
                // as it is very likely to be a false positive.
                int quietStart = start - (nextStart - start);
                if (quietStart >= 0)
                {
                    foundStart = row.isRange(quietStart, start, false);
                }
            }
            return startRange;
        }

        /// <summary>
        ///   <p>Attempts to decode a one-dimensional barcode format given a single row of
        /// an image.</p>
        /// </summary>
        /// <param name="rowNumber">row number from top of the row</param>
        /// <param name="row">the black/white pixel data of the row</param>
        /// <param name="hints">decode hints</param>
        /// <returns>
        ///   <see cref="Result"/>containing encoded string and start/end of barcode or null, if an error occurs or barcode cannot be found
        /// </returns>
        public override Result decodeRow(int rowNumber, BitArray row, IDictionary<DecodeHintType, object> hints)
        {
            return decodeRow(rowNumber, row, findStartGuardPattern(row), hints);
        }

        /// <summary>
        ///   <p>Like <see cref="decodeRow(int,ZXing.Common.BitArray,System.Collections.Generic.IDictionary{ZXing.DecodeHintType,object})"/>, but
        /// allows caller to inform method about where the UPC/EAN start pattern is
        /// found. This allows this to be computed once and reused across many implementations.</p>
        /// </summary>
        /// <param name="rowNumber">row index into the image</param>
        /// <param name="row">encoding of the row of the barcode image</param>
        /// <param name="startGuardRange">start/end column where the opening start pattern was found</param>
        /// <param name="hints">optional hints that influence decoding</param>
        /// <returns><see cref="Result"/> encapsulating the result of decoding a barcode in the row</returns>
        public virtual Result decodeRow(int rowNumber,
                                BitArray row,
                                int[] startGuardRange,
                                IDictionary<DecodeHintType, object> hints)
        {
            var resultPointCallback = hints == null || !hints.ContainsKey(DecodeHintType.NEED_RESULT_POINT_CALLBACK) ? null :
                (ResultPointCallback)hints[DecodeHintType.NEED_RESULT_POINT_CALLBACK];

            if (resultPointCallback != null)
            {
                resultPointCallback(new ResultPoint(
                    (startGuardRange[0] + startGuardRange[1]) / 2.0f, rowNumber
                ));
            }

            var result = decodeRowStringBuffer;
            result.Length = 0;
            var endStart = decodeMiddle(row, startGuardRange, result);
            if (endStart < 0)
                return null;

            if (resultPointCallback != null)
            {
                resultPointCallback(new ResultPoint(
                    endStart, rowNumber
                ));
            }

            var endRange = decodeEnd(row, endStart);
            if (endRange == null)
                return null;

            if (resultPointCallback != null)
            {
                resultPointCallback(new ResultPoint(
                    (endRange[0] + endRange[1]) / 2.0f, rowNumber
                ));
            }


            // Make sure there is a quiet zone at least as big as the end pattern after the barcode. The
            // spec might want more whitespace, but in practice this is the maximum we can count on.
            var end = endRange[1];
            var quietEnd = end + (end - endRange[0]);
            if (quietEnd >= row.Size || !row.isRange(end, quietEnd, false))
            {
                return null;
            }

            var resultString = result.ToString();
            // UPC/EAN should never be less than 8 chars anyway
            if (resultString.Length < 8)
            {
                return null;
            }
            if (!checkChecksum(resultString))
            {
                return null;
            }

            var left = (startGuardRange[1] + startGuardRange[0]) / 2.0f;
            var right = (endRange[1] + endRange[0]) / 2.0f;
            var format = BarcodeFormat;
            var decodeResult = new Result(resultString,
                                             null, // no natural byte representation for these barcodes
                                             new ResultPoint[]
                                                {
                                                new ResultPoint(left, rowNumber),
                                                new ResultPoint(right, rowNumber)
                                                },
                                             format);

            var extensionResult = extensionReader.decodeRow(rowNumber, row, endRange[1]);
            if (extensionResult != null)
            {
                decodeResult.putMetadata(ResultMetadataType.UPC_EAN_EXTENSION, extensionResult.Text);
                decodeResult.putAllMetadata(extensionResult.ResultMetadata);
                decodeResult.addResultPoints(extensionResult.ResultPoints);
                int extensionLength = extensionResult.Text.Length;
                int[] allowedExtensions = hints != null && hints.ContainsKey(DecodeHintType.ALLOWED_EAN_EXTENSIONS) ?
                   (int[])hints[DecodeHintType.ALLOWED_EAN_EXTENSIONS] : null;
                if (allowedExtensions != null)
                {
                    bool valid = false;
                    foreach (int length in allowedExtensions)
                    {
                        if (extensionLength == length)
                        {
                            valid = true;
                            break;
                        }
                    }
                    if (!valid)
                    {
                        return null;
                    }
                }
            }

            if (format == BarcodeFormat.EAN_13 || format == BarcodeFormat.UPC_A)
            {
                String countryID = eanManSupport.lookupCountryIdentifier(resultString);
                if (countryID != null)
                {
                    decodeResult.putMetadata(ResultMetadataType.POSSIBLE_COUNTRY, countryID);
                }
            }

            return decodeResult;
        }

        /// <summary>
        /// </summary>
        /// <param name="s">string of digits to check</param>
        /// <returns>see <see cref="checkStandardUPCEANChecksum(String)"/></returns>
        protected virtual bool checkChecksum(String s)
        {
            return checkStandardUPCEANChecksum(s);
        }

        /// <summary>
        /// Computes the UPC/EAN checksum on a string of digits, and reports
        /// whether the checksum is correct or not.
        /// </summary>
        /// <param name="s">string of digits to check</param>
        /// <returns>true iff string of digits passes the UPC/EAN checksum algorithm</returns>
        internal static bool checkStandardUPCEANChecksum(String s)
        {
            int length = s.Length;
            if (length == 0)
            {
                return false;
            }

            int check = s[length - 1] - '0';
            return getStandardUPCEANChecksum(s.Substring(0, length - 1)) == check;
        }

        internal static int? getStandardUPCEANChecksum(String s)
        {
            int length = s.Length;
            int sum = 0;
            for (int i = length - 1; i >= 0; i -= 2)
            {
                int digit = s[i] - '0';
                if (digit < 0 || digit > 9)
                {
                    throw new ArgumentException("Contents should only contain digits, but got '" + s[i] + "'");
                }
                sum += digit;
            }
            sum *= 3;
            for (int i = length - 2; i >= 0; i -= 2)
            {
                int digit = s[i] - '0';
                if (digit < 0 || digit > 9)
                {
                    throw new ArgumentException("Contents should only contain digits, but got '" + s[i] + "'");
                }
                sum += digit;
            }
            return (1000 - sum) % 10;
        }

        /// <summary>
        /// Decodes the end.
        /// </summary>
        /// <param name="row">The row.</param>
        /// <param name="endStart">The end start.</param>
        /// <returns></returns>
        protected virtual int[] decodeEnd(BitArray row, int endStart)
        {
            return findGuardPattern(row, endStart, false, START_END_PATTERN);
        }

        internal static int[] findGuardPattern(BitArray row,
                                      int rowOffset,
                                      bool whiteFirst,
                                      int[] pattern)
        {
            return findGuardPattern(row, rowOffset, whiteFirst, pattern, new int[pattern.Length]);
        }

        /// <summary>
        /// </summary>
        /// <param name="row">row of black/white values to search</param>
        /// <param name="rowOffset">position to start search</param>
        /// <param name="whiteFirst">if true, indicates that the pattern specifies white/black/white/...</param>
        /// pixel counts, otherwise, it is interpreted as black/white/black/...
        /// <param name="pattern">pattern of counts of number of black and white pixels that are being</param>
        /// searched for as a pattern
        /// <param name="counters">array of counters, as long as pattern, to re-use</param>
        /// <returns>start/end horizontal offset of guard pattern, as an array of two ints</returns>
        internal static int[] findGuardPattern(BitArray row,
                                      int rowOffset,
                                      bool whiteFirst,
                                      int[] pattern,
                                      int[] counters)
        {
            int patternLength = pattern.Length;
            int width = row.Size;
            bool isWhite = whiteFirst;
            rowOffset = whiteFirst ? row.getNextUnset(rowOffset) : row.getNextSet(rowOffset);
            int counterPosition = 0;
            int patternStart = rowOffset;
            for (int x = rowOffset; x < width; x++)
            {
                if (row[x] != isWhite)
                {
                    counters[counterPosition]++;
                }
                else
                {
                    if (counterPosition == patternLength - 1)
                    {
                        if (patternMatchVariance(counters, pattern, MAX_INDIVIDUAL_VARIANCE) < MAX_AVG_VARIANCE)
                        {
                            return new int[] { patternStart, x };
                        }
                        patternStart += counters[0] + counters[1];
                        Array.Copy(counters, 2, counters, 0, counterPosition - 1);
                        counters[counterPosition - 1] = 0;
                        counters[counterPosition] = 0;
                        counterPosition--;
                    }
                    else
                    {
                        counterPosition++;
                    }
                    counters[counterPosition] = 1;
                    isWhite = !isWhite;
                }
            }
            return null;
        }

        /// <summary>
        /// Attempts to decode a single UPC/EAN-encoded digit.
        /// </summary>
        /// <param name="row">row of black/white values to decode</param>
        /// <param name="counters">the counts of runs of observed black/white/black/... values</param>
        /// <param name="rowOffset">horizontal offset to start decoding from</param>
        /// <param name="patterns">the set of patterns to use to decode -- sometimes different encodings</param>
        /// for the digits 0-9 are used, and this indicates the encodings for 0 to 9 that should
        /// be used
        /// <param name="digit">horizontal offset of first pixel beyond the decoded digit</param>
        /// <returns></returns>
        internal static bool decodeDigit(BitArray row, int[] counters, int rowOffset, int[][] patterns, out int digit)
        {
            digit = -1;

            if (!recordPattern(row, rowOffset, counters))
                return false;

            int bestVariance = MAX_AVG_VARIANCE; // worst variance we'll accept
            int max = patterns.Length;
            for (int i = 0; i < max; i++)
            {
                int[] pattern = patterns[i];
                int variance = patternMatchVariance(counters, pattern, MAX_INDIVIDUAL_VARIANCE);
                if (variance < bestVariance)
                {
                    bestVariance = variance;
                    digit = i;
                }
            }
            return digit >= 0;
        }

        /// <summary>
        /// Get the format of this decoder.
        /// </summary>
        /// <returns>The 1D format.</returns>
        internal abstract BarcodeFormat BarcodeFormat { get; }

        /// <summary>
        /// Subclasses override this to decode the portion of a barcode between the start
        /// and end guard patterns.
        /// </summary>
        /// <param name="row">row of black/white values to search</param>
        /// <param name="startRange">start/end offset of start guard pattern</param>
        /// <param name="resultString"><see cref="StringBuilder" />to append decoded chars to</param>
        /// <returns>horizontal offset of first pixel after the "middle" that was decoded or -1 if decoding could not complete successfully</returns>
        protected internal abstract int decodeMiddle(BitArray row,
                                                     int[] startRange,
                                                     StringBuilder resultString);
    }
}