using System;
using System.Collections.Generic;

/*
 * 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.detector
{

	using DecodeHintType = com.google.zxing.DecodeHintType;
	using NotFoundException = com.google.zxing.NotFoundException;
	using ResultPoint = com.google.zxing.ResultPoint;
	using ResultPointCallback = com.google.zxing.ResultPointCallback;
	using BitMatrix = com.google.zxing.common.BitMatrix;


	/// <summary>
	/// <p>This class attempts to find finder patterns in a QR Code. Finder patterns are the square
	/// markers at three corners of a QR Code.</p>
	/// 
	/// <p>This class is thread-safe but not reentrant. Each thread must allocate its own object.
	/// 
	/// @author Sean Owen
	/// </summary>
	public class FinderPatternFinder
	{

	  private const int CENTER_QUORUM = 2;
	  protected internal const int MIN_SKIP = 3; // 1 pixel/module times 3 modules/center
	  protected internal const int MAX_MODULES = 57; // support up to version 10 for mobile clients
	  private const int INTEGER_MATH_SHIFT = 8;

	  private readonly BitMatrix image;
	  private readonly List<FinderPattern> possibleCenters;
	  private bool hasSkipped;
	  private readonly int[] crossCheckStateCount;
	  private readonly ResultPointCallback resultPointCallback;

	  /// <summary>
	  /// <p>Creates a finder that will search the image for three finder patterns.</p>
	  /// </summary>
	  /// <param name="image"> image to search </param>
	  public FinderPatternFinder(BitMatrix image) : this(image, null)
	  {
	  }

	  public FinderPatternFinder(BitMatrix image, ResultPointCallback resultPointCallback)
	  {
		this.image = image;
		this.possibleCenters = new List<FinderPattern>();
		this.crossCheckStateCount = new int[5];
		this.resultPointCallback = resultPointCallback;
	  }

	  protected internal BitMatrix Image
	  {
		  get
		  {
			return image;
		  }
	  }

	  protected internal List<FinderPattern> PossibleCenters
	  {
		  get
		  {
			return possibleCenters;
		  }
	  }

//JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in .NET:
//ORIGINAL LINE: final FinderPatternInfo find(java.util.Map<com.google.zxing.DecodeHintType,?> hints) throws com.google.zxing.NotFoundException
      internal FinderPatternInfo find(IDictionary<DecodeHintType, object> hints)
	  {
		bool tryHarder = hints != null && hints.ContainsKey(DecodeHintType.TRY_HARDER);
		int maxI = image.Height;
		int maxJ = image.Width;
		// We are looking for black/white/black/white/black modules in
		// 1:1:3:1:1 ratio; this tracks the number of such modules seen so far

		// Let's assume that the maximum version QR Code we support takes up 1/4 the height of the
		// image, and then account for the center being 3 modules in size. This gives the smallest
		// number of pixels the center could be, so skip this often. When trying harder, look for all
		// QR versions regardless of how dense they are.
		int iSkip = (3 * maxI) / (4 * MAX_MODULES);
		if (iSkip < MIN_SKIP || tryHarder)
		{
		  iSkip = MIN_SKIP;
		}

		bool done = false;
		int[] stateCount = new int[5];
		for (int i = iSkip - 1; i < maxI && !done; i += iSkip)
		{
		  // Get a row of black/white values
		  stateCount[0] = 0;
		  stateCount[1] = 0;
		  stateCount[2] = 0;
		  stateCount[3] = 0;
		  stateCount[4] = 0;
		  int currentState = 0;
		  for (int j = 0; j < maxJ; j++)
		  {
			if (image.get(j, i))
			{
			  // Black pixel
			  if ((currentState & 1) == 1) // Counting white pixels
			  {
				currentState++;
			  }
			  stateCount[currentState]++;
			} // White pixel
			else
			{
			  if ((currentState & 1) == 0) // Counting black pixels
			  {
				if (currentState == 4) // A winner?
				{
				  if (foundPatternCross(stateCount)) // Yes
				  {
					bool confirmed = handlePossibleCenter(stateCount, i, j);
					if (confirmed)
					{
					  // Start examining every other line. Checking each line turned out to be too
					  // expensive and didn't improve performance.
					  iSkip = 2;
					  if (hasSkipped)
					  {
						done = haveMultiplyConfirmedCenters();
					  }
					  else
					  {
						int rowSkip = findRowSkip();
						if (rowSkip > stateCount[2])
						{
						  // Skip rows between row of lower confirmed center
						  // and top of presumed third confirmed center
						  // but back up a bit to get a full chance of detecting
						  // it, entire width of center of finder pattern

						  // Skip by rowSkip, but back off by stateCount[2] (size of last center
						  // of pattern we saw) to be conservative, and also back off by iSkip which
						  // is about to be re-added
						  i += rowSkip - stateCount[2] - iSkip;
						  j = maxJ - 1;
						}
					  }
					}
					else
					{
					  stateCount[0] = stateCount[2];
					  stateCount[1] = stateCount[3];
					  stateCount[2] = stateCount[4];
					  stateCount[3] = 1;
					  stateCount[4] = 0;
					  currentState = 3;
					  continue;
					}
					// Clear state to start looking again
					currentState = 0;
					stateCount[0] = 0;
					stateCount[1] = 0;
					stateCount[2] = 0;
					stateCount[3] = 0;
					stateCount[4] = 0;
				  } // No, shift counts back by two
				  else
				  {
					stateCount[0] = stateCount[2];
					stateCount[1] = stateCount[3];
					stateCount[2] = stateCount[4];
					stateCount[3] = 1;
					stateCount[4] = 0;
					currentState = 3;
				  }
				}
				else
				{
				  stateCount[++currentState]++;
				}
			  } // Counting white pixels
			  else
			  {
				stateCount[currentState]++;
			  }
			}
		  }
		  if (foundPatternCross(stateCount))
		  {
			bool confirmed = handlePossibleCenter(stateCount, i, maxJ);
			if (confirmed)
			{
			  iSkip = stateCount[0];
			  if (hasSkipped)
			  {
				// Found a third one
				done = haveMultiplyConfirmedCenters();
			  }
			}
		  }
		}

		FinderPattern[] patternInfo = selectBestPatterns();
		ResultPoint.orderBestPatterns(patternInfo);

		return new FinderPatternInfo(patternInfo);
	  }

	  /// <summary>
	  /// Given a count of black/white/black/white/black pixels just seen and an end position,
	  /// figures the location of the center of this run.
	  /// </summary>
	  private static float centerFromEnd(int[] stateCount, int end)
	  {
		return (float)(end - stateCount[4] - stateCount[3]) - stateCount[2] / 2.0f;
	  }

	  /// <param name="stateCount"> count of black/white/black/white/black pixels just read </param>
	  /// <returns> true iff the proportions of the counts is close enough to the 1/1/3/1/1 ratios
	  ///         used by finder patterns to be considered a match </returns>
	  protected internal static bool foundPatternCross(int[] stateCount)
	  {
		int totalModuleSize = 0;
		for (int i = 0; i < 5; i++)
		{
		  int count = stateCount[i];
		  if (count == 0)
		  {
			return false;
		  }
		  totalModuleSize += count;
		}
		if (totalModuleSize < 7)
		{
		  return false;
		}
		int moduleSize = (totalModuleSize << INTEGER_MATH_SHIFT) / 7;
		int maxVariance = moduleSize / 2;
		// Allow less than 50% variance from 1-1-3-1-1 proportions
		return Math.Abs(moduleSize - (stateCount[0] << INTEGER_MATH_SHIFT)) < maxVariance && Math.Abs(moduleSize - (stateCount[1] << INTEGER_MATH_SHIFT)) < maxVariance && Math.Abs(3 * moduleSize - (stateCount[2] << INTEGER_MATH_SHIFT)) < 3 * maxVariance && Math.Abs(moduleSize - (stateCount[3] << INTEGER_MATH_SHIFT)) < maxVariance && Math.Abs(moduleSize - (stateCount[4] << INTEGER_MATH_SHIFT)) < maxVariance;
	  }

	  private int[] CrossCheckStateCount
	  {
		  get
		  {
			crossCheckStateCount[0] = 0;
			crossCheckStateCount[1] = 0;
			crossCheckStateCount[2] = 0;
			crossCheckStateCount[3] = 0;
			crossCheckStateCount[4] = 0;
			return crossCheckStateCount;
		  }
	  }

	  /// <summary>
	  /// <p>After a horizontal scan finds a potential finder pattern, this method
	  /// "cross-checks" by scanning down vertically through the center of the possible
	  /// finder pattern to see if the same proportion is detected.</p>
	  /// </summary>
	  /// <param name="startI"> row where a finder pattern was detected </param>
	  /// <param name="centerJ"> center of the section that appears to cross a finder pattern </param>
	  /// <param name="maxCount"> maximum reasonable number of modules that should be
	  /// observed in any reading state, based on the results of the horizontal scan </param>
	  /// <returns> vertical center of finder pattern, or <seealso cref="Float#NaN"/> if not found </returns>
	  private float crossCheckVertical(int startI, int centerJ, int maxCount, int originalStateCountTotal)
	  {
		BitMatrix image = this.image;

		int maxI = image.Height;
		int[] stateCount = CrossCheckStateCount;

		// Start counting up from center
		int i = startI;
		while (i >= 0 && image.get(centerJ, i))
		{
		  stateCount[2]++;
		  i--;
		}
		if (i < 0)
		{
		  return float.NaN;
		}
		while (i >= 0 && !image.get(centerJ, i) && stateCount[1] <= maxCount)
		{
		  stateCount[1]++;
		  i--;
		}
		// If already too many modules in this state or ran off the edge:
		if (i < 0 || stateCount[1] > maxCount)
		{
		  return float.NaN;
		}
		while (i >= 0 && image.get(centerJ, i) && stateCount[0] <= maxCount)
		{
		  stateCount[0]++;
		  i--;
		}
		if (stateCount[0] > maxCount)
		{
		  return float.NaN;
		}

		// Now also count down from center
		i = startI + 1;
		while (i < maxI && image.get(centerJ, i))
		{
		  stateCount[2]++;
		  i++;
		}
		if (i == maxI)
		{
		  return float.NaN;
		}
		while (i < maxI && !image.get(centerJ, i) && stateCount[3] < maxCount)
		{
		  stateCount[3]++;
		  i++;
		}
		if (i == maxI || stateCount[3] >= maxCount)
		{
		  return float.NaN;
		}
		while (i < maxI && image.get(centerJ, i) && stateCount[4] < maxCount)
		{
		  stateCount[4]++;
		  i++;
		}
		if (stateCount[4] >= maxCount)
		{
		  return float.NaN;
		}

		// If we found a finder-pattern-like section, but its size is more than 40% different than
		// the original, assume it's a false positive
		int stateCountTotal = stateCount[0] + stateCount[1] + stateCount[2] + stateCount[3] + stateCount[4];
		if (5 * Math.Abs(stateCountTotal - originalStateCountTotal) >= 2 * originalStateCountTotal)
		{
		  return float.NaN;
		}

		return foundPatternCross(stateCount) ? centerFromEnd(stateCount, i) : float.NaN;
	  }

	  /// <summary>
	  /// <p>Like <seealso cref="#crossCheckVertical(int, int, int, int)"/>, and in fact is basically identical,
	  /// except it reads horizontally instead of vertically. This is used to cross-cross
	  /// check a vertical cross check and locate the real center of the alignment pattern.</p>
	  /// </summary>
	  private float crossCheckHorizontal(int startJ, int centerI, int maxCount, int originalStateCountTotal)
	  {
		BitMatrix image = this.image;

		int maxJ = image.Width;
		int[] stateCount = CrossCheckStateCount;

		int j = startJ;
		while (j >= 0 && image.get(j, centerI))
		{
		  stateCount[2]++;
		  j--;
		}
		if (j < 0)
		{
		  return float.NaN;
		}
		while (j >= 0 && !image.get(j, centerI) && stateCount[1] <= maxCount)
		{
		  stateCount[1]++;
		  j--;
		}
		if (j < 0 || stateCount[1] > maxCount)
		{
		  return float.NaN;
		}
		while (j >= 0 && image.get(j, centerI) && stateCount[0] <= maxCount)
		{
		  stateCount[0]++;
		  j--;
		}
		if (stateCount[0] > maxCount)
		{
		  return float.NaN;
		}

		j = startJ + 1;
		while (j < maxJ && image.get(j, centerI))
		{
		  stateCount[2]++;
		  j++;
		}
		if (j == maxJ)
		{
		  return float.NaN;
		}
		while (j < maxJ && !image.get(j, centerI) && stateCount[3] < maxCount)
		{
		  stateCount[3]++;
		  j++;
		}
		if (j == maxJ || stateCount[3] >= maxCount)
		{
		  return float.NaN;
		}
		while (j < maxJ && image.get(j, centerI) && stateCount[4] < maxCount)
		{
		  stateCount[4]++;
		  j++;
		}
		if (stateCount[4] >= maxCount)
		{
		  return float.NaN;
		}

		// If we found a finder-pattern-like section, but its size is significantly different than
		// the original, assume it's a false positive
		int stateCountTotal = stateCount[0] + stateCount[1] + stateCount[2] + stateCount[3] + stateCount[4];
		if (5 * Math.Abs(stateCountTotal - originalStateCountTotal) >= originalStateCountTotal)
		{
		  return float.NaN;
		}

		return foundPatternCross(stateCount) ? centerFromEnd(stateCount, j) : float.NaN;
	  }

	  /// <summary>
	  /// <p>This is called when a horizontal scan finds a possible alignment pattern. It will
	  /// cross check with a vertical scan, and if successful, will, ah, cross-cross-check
	  /// with another horizontal scan. This is needed primarily to locate the real horizontal
	  /// center of the pattern in cases of extreme skew.</p>
	  /// 
	  /// <p>If that succeeds the finder pattern location is added to a list that tracks
	  /// the number of times each location has been nearly-matched as a finder pattern.
	  /// Each additional find is more evidence that the location is in fact a finder
	  /// pattern center
	  /// </summary>
	  /// <param name="stateCount"> reading state module counts from horizontal scan </param>
	  /// <param name="i"> row where finder pattern may be found </param>
	  /// <param name="j"> end of possible finder pattern in row </param>
	  /// <returns> true if a finder pattern candidate was found this time </returns>
	  protected internal bool handlePossibleCenter(int[] stateCount, int i, int j)
	  {
		int stateCountTotal = stateCount[0] + stateCount[1] + stateCount[2] + stateCount[3] + stateCount[4];
		float centerJ = centerFromEnd(stateCount, j);
		float centerI = crossCheckVertical(i, (int) centerJ, stateCount[2], stateCountTotal);
		if (!float.IsNaN(centerI))
		{
		  // Re-cross check
		  centerJ = crossCheckHorizontal((int) centerJ, (int) centerI, stateCount[2], stateCountTotal);
		  if (!float.IsNaN(centerJ))
		  {
			float estimatedModuleSize = (float) stateCountTotal / 7.0f;
			bool found = false;
			for (int index = 0; index < possibleCenters.Count; index++)
			{
			  FinderPattern center = possibleCenters[index];
			  // Look for about the same center and module size:
			  if (center.aboutEquals(estimatedModuleSize, centerI, centerJ))
			  {
				possibleCenters[index] = center.combineEstimate(centerI, centerJ, estimatedModuleSize);
				found = true;
				break;
			  }
			}
			if (!found)
			{
			  FinderPattern point = new FinderPattern(centerJ, centerI, estimatedModuleSize);
			  possibleCenters.Add(point);
			  if (resultPointCallback != null)
			  {
				resultPointCallback.foundPossibleResultPoint(point);
			  }
			}
			return true;
		  }
		}
		return false;
	  }

	  /// <returns> number of rows we could safely skip during scanning, based on the first
	  ///         two finder patterns that have been located. In some cases their position will
	  ///         allow us to infer that the third pattern must lie below a certain point farther
	  ///         down in the image. </returns>
	  private int findRowSkip()
	  {
		int max = possibleCenters.Count;
		if (max <= 1)
		{
		  return 0;
		}
		FinderPattern firstConfirmedCenter = null;
		foreach (FinderPattern center in possibleCenters)
		{
		  if (center.Count >= CENTER_QUORUM)
		  {
			if (firstConfirmedCenter == null)
			{
			  firstConfirmedCenter = center;
			}
			else
			{
			  // We have two confirmed centers
			  // How far down can we skip before resuming looking for the next
			  // pattern? In the worst case, only the difference between the
			  // difference in the x / y coordinates of the two centers.
			  // This is the case where you find top left last.
			  hasSkipped = true;
			  return (int)(Math.Abs(firstConfirmedCenter.X - center.X) - Math.Abs(firstConfirmedCenter.Y - center.Y)) / 2;
			}
		  }
		}
		return 0;
	  }

	  /// <returns> true iff we have found at least 3 finder patterns that have been detected
	  ///         at least <seealso cref="#CENTER_QUORUM"/> times each, and, the estimated module size of the
	  ///         candidates is "pretty similar" </returns>
	  private bool haveMultiplyConfirmedCenters()
	  {
		int confirmedCount = 0;
		float totalModuleSize = 0.0f;
		int max = possibleCenters.Count;
		foreach (FinderPattern pattern in possibleCenters)
		{
		  if (pattern.Count >= CENTER_QUORUM)
		  {
			confirmedCount++;
			totalModuleSize += pattern.EstimatedModuleSize;
		  }
		}
		if (confirmedCount < 3)
		{
		  return false;
		}
		// OK, we have at least 3 confirmed centers, but, it's possible that one is a "false positive"
		// and that we need to keep looking. We detect this by asking if the estimated module sizes
		// vary too much. We arbitrarily say that when the total deviation from average exceeds
		// 5% of the total module size estimates, it's too much.
		float average = totalModuleSize / (float) max;
		float totalDeviation = 0.0f;
		foreach (FinderPattern pattern in possibleCenters)
		{
		  totalDeviation += Math.Abs(pattern.EstimatedModuleSize - average);
		}
		return totalDeviation <= 0.05f * totalModuleSize;
	  }

	  /// <returns> the 3 best <seealso cref="FinderPattern"/>s from our list of candidates. The "best" are
	  ///         those that have been detected at least <seealso cref="#CENTER_QUORUM"/> times, and whose module
	  ///         size differs from the average among those patterns the least </returns>
	  /// <exception cref="NotFoundException"> if 3 such finder patterns do not exist </exception>
//JAVA TO C# CONVERTER WARNING: Method 'throws' clauses are not available in .NET:
//ORIGINAL LINE: private FinderPattern[] selectBestPatterns() throws com.google.zxing.NotFoundException
	  private FinderPattern[] selectBestPatterns()
	  {

		int startSize = possibleCenters.Count;
		if (startSize < 3)
		{
		  // Couldn't find enough finder patterns
		  throw NotFoundException.NotFoundInstance;
		}

		// Filter outlier possibilities whose module size is too different
		if (startSize > 3)
		{
		  // But we can only afford to do so if we have at least 4 possibilities to choose from
		  float totalModuleSize = 0.0f;
		  float square = 0.0f;
		  foreach (FinderPattern center in possibleCenters)
		  {
			float size = center.EstimatedModuleSize;
			totalModuleSize += size;
			square += size * size;
		  }
		  float average = totalModuleSize / (float) startSize;
		  float stdDev = (float) Math.Sqrt(square / startSize - average * average);

		  possibleCenters.Sort(new FurthestFromAverageComparator(average));

		  float limit = Math.Max(0.2f * average, stdDev);

		  for (int i = 0; i < possibleCenters.Count && possibleCenters.Count > 3; i++)
		  {
			FinderPattern pattern = possibleCenters[i];
			if (Math.Abs(pattern.EstimatedModuleSize - average) > limit)
			{
			  possibleCenters.RemoveAt(i);
			  i--;
			}
		  }
		}

		if (possibleCenters.Count > 3)
		{
		  // Throw away all but those first size candidate points we found.

		  float totalModuleSize = 0.0f;
		  foreach (FinderPattern possibleCenter in possibleCenters)
		  {
			totalModuleSize += possibleCenter.EstimatedModuleSize;
		  }

		  float average = totalModuleSize / (float) possibleCenters.Count;

		  possibleCenters.Sort(new CenterComparator(average));

          //possibleCenters.subList(3, possibleCenters.Count).clear();
            possibleCenters.RemoveRange(3,possibleCenters.Count-3);
		}

		return new FinderPattern[]{possibleCenters[0], possibleCenters[1], possibleCenters[2]};
	  }

	  /// <summary>
	  /// <p>Orders by furthest from average</p>
	  /// </summary>
	  [Serializable]
	  private sealed class FurthestFromAverageComparator : IComparer<FinderPattern>
	  {
		private readonly float average;
		internal FurthestFromAverageComparator(float f)
		{
		  average = f;
		}
		public int Compare(FinderPattern center1, FinderPattern center2)
		{
		  float dA = Math.Abs(center2.EstimatedModuleSize - average);
		  float dB = Math.Abs(center1.EstimatedModuleSize - average);
		  return dA < dB ? - 1 : dA == dB ? 0 : 1;
		}
	  }

	  /// <summary>
	  /// <p>Orders by <seealso cref="FinderPattern#getCount()"/>, descending.</p>
	  /// </summary>
	  [Serializable]
	  private sealed class CenterComparator : IComparer<FinderPattern>
	  {
		private readonly float average;
		internal CenterComparator(float f)
		{
		  average = f;
		}
		public int Compare(FinderPattern center1, FinderPattern center2)
		{
		  if (center2.Count == center1.Count)
		  {
			float dA = Math.Abs(center2.EstimatedModuleSize - average);
			float dB = Math.Abs(center1.EstimatedModuleSize - average);
			return dA < dB ? 1 : dA == dB ? 0 : -1;
		  }
		  else
		  {
			return center2.Count - center1.Count;
		  }
		}
	  }

	}

}