/*
 * 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 ZXing.Common;

namespace ZXing.OneD
{
    /// <summary>
    /// Encapsulates functionality and implementation that is common to all families
    /// of one-dimensional barcodes.
    /// <author>dswitkin@google.com (Daniel Switkin)</author>
    /// <author>Sean Owen</author>
    /// </summary>
    public abstract class OneDReader : Reader
    {
        /// <summary>
        /// 
        /// </summary>
        protected static int INTEGER_MATH_SHIFT = 8;
        /// <summary>
        /// 
        /// </summary>
        protected static int PATTERN_MATCH_RESULT_SCALE_FACTOR = 1 << INTEGER_MATH_SHIFT;

        /// <summary>
        /// Locates and decodes a barcode in some format within an image.
        /// </summary>
        /// <param name="image">image of barcode to decode</param>
        /// <returns>
        /// String which the barcode encodes
        /// </returns>
        public Result decode(BinaryBitmap image)
        {
            return decode(image, null);
        }

        /// <summary>
        /// Locates and decodes a barcode in some format within an image. This method also accepts
        /// hints, each possibly associated to some data, which may help the implementation decode.
        /// Note that we don't try rotation without the try harder flag, even if rotation was supported.
        /// </summary>
        /// <param name="image">image of barcode to decode</param>
        /// <param name="hints">passed as a <see cref="IDictionary{TKey, TValue}"/> from <see cref="DecodeHintType"/>
        /// to arbitrary data. The
        /// meaning of the data depends upon the hint type. The implementation may or may not do
        /// anything with these hints.</param>
        /// <returns>
        /// String which the barcode encodes
        /// </returns>
        virtual public Result decode(BinaryBitmap image, IDictionary<DecodeHintType, object> hints)
        {
            var result = doDecode(image, hints);
            if (result == null)
            {
                bool tryHarder = hints != null && hints.ContainsKey(DecodeHintType.TRY_HARDER);
                bool tryHarderWithoutRotation = hints != null && hints.ContainsKey(DecodeHintType.TRY_HARDER_WITHOUT_ROTATION);
                if (tryHarder && !tryHarderWithoutRotation && image.RotateSupported)
                {
                    BinaryBitmap rotatedImage = image.rotateCounterClockwise();
                    result = doDecode(rotatedImage, hints);
                    if (result == null)
                        return null;
                    // Record that we found it rotated 90 degrees CCW / 270 degrees CW
                    IDictionary<ResultMetadataType, object> metadata = result.ResultMetadata;
                    int orientation = 270;
                    if (metadata != null && metadata.ContainsKey(ResultMetadataType.ORIENTATION))
                    {
                        // But if we found it reversed in doDecode(), add in that result here:
                        orientation = (orientation +
                                       (int)metadata[ResultMetadataType.ORIENTATION]) % 360;
                    }
                    result.putMetadata(ResultMetadataType.ORIENTATION, orientation);
                    // Update result points
                    ResultPoint[] points = result.ResultPoints;
                    if (points != null)
                    {
                        int height = rotatedImage.Height;
                        for (int i = 0; i < points.Length; i++)
                        {
                            points[i] = new ResultPoint(height - points[i].Y - 1, points[i].X);
                        }
                    }
                }
            }
            return result;
        }

        /// <summary>
        /// Resets any internal state the implementation has after a decode, to prepare it
        /// for reuse.
        /// </summary>
        virtual public void reset()
        {
            // do nothing
        }

        /// <summary>
        /// We're going to examine rows from the middle outward, searching alternately above and below the
        /// middle, and farther out each time. rowStep is the number of rows between each successive
        /// attempt above and below the middle. So we'd scan row middle, then middle - rowStep, then
        /// middle + rowStep, then middle - (2 * rowStep), etc.
        /// rowStep is bigger as the image is taller, but is always at least 1. We've somewhat arbitrarily
        /// decided that moving up and down by about 1/16 of the image is pretty good; we try more of the
        /// image if "trying harder".
        /// </summary>
        /// <param name="image">The image to decode</param>
        /// <param name="hints">Any hints that were requested</param>
        /// <returns>The contents of the decoded barcode</returns>
        virtual protected Result doDecode(BinaryBitmap image, IDictionary<DecodeHintType, object> hints)
        {
            int width = image.Width;
            int height = image.Height;
            BitArray row = new BitArray(width);

            bool tryHarder = hints != null && hints.ContainsKey(DecodeHintType.TRY_HARDER);
            int rowStep = Math.Max(1, height >> (tryHarder ? 8 : 5));
            int maxLines;
            if (tryHarder)
            {
                maxLines = height; // Look at the whole image, not just the center
            }
            else
            {
                maxLines = 15; // 15 rows spaced 1/32 apart is roughly the middle half of the image
            }

            int middle = height >> 1;
            for (int x = 0; x < maxLines; x++)
            {

                // Scanning from the middle out. Determine which row we're looking at next:
                int rowStepsAboveOrBelow = (x + 1) >> 1;
                bool isAbove = (x & 0x01) == 0; // i.e. is x even?
                int rowNumber = middle + rowStep * (isAbove ? rowStepsAboveOrBelow : -rowStepsAboveOrBelow);
                if (rowNumber < 0 || rowNumber >= height)
                {
                    // Oops, if we run off the top or bottom, stop
                    break;
                }

                // Estimate black point for this row and load it:
                row = image.getBlackRow(rowNumber, row);
                if (row == null)
                    continue;

                // While we have the image data in a BitArray, it's fairly cheap to reverse it in place to
                // handle decoding upside down barcodes.
                for (int attempt = 0; attempt < 2; attempt++)
                {
                    if (attempt == 1)
                    {
                        // trying again?
                        row.reverse(); // reverse the row and continue
                                       // This means we will only ever draw result points *once* in the life of this method
                                       // since we want to avoid drawing the wrong points after flipping the row, and,
                                       // don't want to clutter with noise from every single row scan -- just the scans
                                       // that start on the center line.
                        if (hints != null && hints.ContainsKey(DecodeHintType.NEED_RESULT_POINT_CALLBACK))
                        {
                            IDictionary<DecodeHintType, Object> newHints = new Dictionary<DecodeHintType, Object>();
                            foreach (var hint in hints)
                            {
                                if (hint.Key != DecodeHintType.NEED_RESULT_POINT_CALLBACK)
                                    newHints.Add(hint.Key, hint.Value);
                            }
                            hints = newHints;
                        }
                    }
                    // Look for a barcode
                    Result result = decodeRow(rowNumber, row, hints);
                    if (result == null)
                        continue;

                    // We found our barcode
                    if (attempt == 1)
                    {
                        // But it was upside down, so note that
                        result.putMetadata(ResultMetadataType.ORIENTATION, 180);
                        // And remember to flip the result points horizontally.
                        ResultPoint[] points = result.ResultPoints;
                        if (points != null)
                        {
                            points[0] = new ResultPoint(width - points[0].X - 1, points[0].Y);
                            points[1] = new ResultPoint(width - points[1].X - 1, points[1].Y);
                        }
                    }
                    return result;
                }
            }

            return null;
        }

        /// <summary>
        /// Records the size of successive runs of white and black pixels in a row, starting at a given point.
        /// The values are recorded in the given array, and the number of runs recorded is equal to the size
        /// of the array. If the row starts on a white pixel at the given start point, then the first count
        /// recorded is the run of white pixels starting from that point; likewise it is the count of a run
        /// of black pixels if the row begin on a black pixels at that point.
        /// </summary>
        /// <param name="row">row to count from</param>
        /// <param name="start">offset into row to start at</param>
        /// <param name="counters">array into which to record counts</param>
        protected static bool recordPattern(BitArray row,
                                            int start,
                                            int[] counters)
        {
            return recordPattern(row, start, counters, counters.Length);
        }

        /// <summary>
        /// Records the size of successive runs of white and black pixels in a row, starting at a given point.
        /// The values are recorded in the given array, and the number of runs recorded is equal to the size
        /// of the array. If the row starts on a white pixel at the given start point, then the first count
        /// recorded is the run of white pixels starting from that point; likewise it is the count of a run
        /// of black pixels if the row begin on a black pixels at that point.
        /// </summary>
        /// <param name="row">row to count from</param>
        /// <param name="start">offset into row to start at</param>
        /// <param name="counters">array into which to record counts</param>
        /// <param name="numCounters"></param>
        protected static bool recordPattern(BitArray row,
                                            int start,
                                            int[] counters,
                                            int numCounters)
        {
            for (int idx = 0; idx < numCounters; idx++)
            {
                counters[idx] = 0;
            }
            int end = row.Size;
            if (start >= end)
            {
                return false;
            }
            bool isWhite = !row[start];
            int counterPosition = 0;
            int i = start;
            while (i < end)
            {
                if (row[i] != isWhite)
                {
                    counters[counterPosition]++;
                }
                else
                {
                    counterPosition++;
                    if (counterPosition == numCounters)
                    {
                        break;
                    }
                    else
                    {
                        counters[counterPosition] = 1;
                        isWhite = !isWhite;
                    }
                }
                i++;
            }
            // If we read fully the last section of pixels and filled up our counters -- or filled
            // the last counter but ran off the side of the image, OK. Otherwise, a problem.
            return (counterPosition == numCounters || (counterPosition == numCounters - 1 && i == end));
        }

        /// <summary>
        /// Records the pattern in reverse.
        /// </summary>
        /// <param name="row">The row.</param>
        /// <param name="start">The start.</param>
        /// <param name="counters">The counters.</param>
        /// <returns></returns>
        protected static bool recordPatternInReverse(BitArray row, int start, int[] counters)
        {
            // This could be more efficient I guess
            int numTransitionsLeft = counters.Length;
            bool last = row[start];
            while (start > 0 && numTransitionsLeft >= 0)
            {
                if (row[--start] != last)
                {
                    numTransitionsLeft--;
                    last = !last;
                }
            }
            if (numTransitionsLeft >= 0)
            {
                return false;
            }
            return recordPattern(row, start + 1, counters);
        }

        /// <summary>
        /// Determines how closely a set of observed counts of runs of black/white values matches a given
        /// target pattern. This is reported as the ratio of the total variance from the expected pattern
        /// proportions across all pattern elements, to the length of the pattern.
        /// </summary>
        /// <param name="counters">observed counters</param>
        /// <param name="pattern">expected pattern</param>
        /// <param name="maxIndividualVariance">The most any counter can differ before we give up</param>
        /// <returns>ratio of total variance between counters and pattern compared to total pattern size,
        ///  where the ratio has been multiplied by 256. So, 0 means no variance (perfect match); 256 means
        ///  the total variance between counters and patterns equals the pattern length, higher values mean
        ///  even more variance</returns>
        protected static int patternMatchVariance(int[] counters,
                                                  int[] pattern,
                                                  int maxIndividualVariance)
        {
            int numCounters = counters.Length;
            int total = 0;
            int patternLength = 0;
            for (int i = 0; i < numCounters; i++)
            {
                total += counters[i];
                patternLength += pattern[i];
            }
            if (total < patternLength)
            {
                // If we don't even have one pixel per unit of bar width, assume this is too small
                // to reliably match, so fail:
                return Int32.MaxValue;
            }
            // We're going to fake floating-point math in integers. We just need to use more bits.
            // Scale up patternLength so that intermediate values below like scaledCounter will have
            // more "significant digits"
            int unitBarWidth = (total << INTEGER_MATH_SHIFT) / patternLength;
            maxIndividualVariance = (maxIndividualVariance * unitBarWidth) >> INTEGER_MATH_SHIFT;

            int totalVariance = 0;
            for (int x = 0; x < numCounters; x++)
            {
                int counter = counters[x] << INTEGER_MATH_SHIFT;
                int scaledPattern = pattern[x] * unitBarWidth;
                int variance = counter > scaledPattern ? counter - scaledPattern : scaledPattern - counter;
                if (variance > maxIndividualVariance)
                {
                    return Int32.MaxValue;
                }
                totalVariance += variance;
            }
            return totalVariance / total;
        }

        /// <summary>
        /// Attempts to decode a one-dimensional barcode format given a single row of
        /// an image.
        /// </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
        /// </returns>
        public abstract Result decodeRow(int rowNumber, BitArray row, IDictionary<DecodeHintType, object> hints);
    }
}