/*
 * 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.
 */

using System;
using System.Collections.Generic;

using ZXing.Common;
using ZXing.QrCode.Internal;

namespace ZXing.QrCode
{
    /// <summary>
    /// This implementation can detect and decode QR Codes in an image.
    /// <author>Sean Owen</author>
    /// </summary>
    public class QRCodeReader : Reader
    {
        private static readonly ResultPoint[] NO_POINTS = new ResultPoint[0];

        private readonly Decoder decoder = new Decoder();

        /// <summary>
        /// Gets the decoder.
        /// </summary>
        /// <returns></returns>
        protected Decoder getDecoder()
        {
            return decoder;
        }

        /// <summary>
        /// Locates and decodes a QR code in an image.
        ///
        /// <returns>a String representing the content encoded by the QR code</returns>
        /// </summary>
        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.
        /// </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>
        public Result decode(BinaryBitmap image, IDictionary<DecodeHintType, object> hints)
        {
            DecoderResult decoderResult;
            ResultPoint[] points;
            if (image == null || image.BlackMatrix == null)
            {
                // something is wrong with the image
                return null;
            }
            if (hints != null && hints.ContainsKey(DecodeHintType.PURE_BARCODE))
            {
                var bits = extractPureBits(image.BlackMatrix);
                if (bits == null)
                    return null;
                decoderResult = decoder.decode(bits, hints);
                points = NO_POINTS;
            }
            else
            {
                var detectorResult = new Detector(image.BlackMatrix).detect(hints);
                if (detectorResult == null)
                    return null;
                decoderResult = decoder.decode(detectorResult.Bits, hints);
                points = detectorResult.Points;
            }
            if (decoderResult == null)
                return null;

            // If the code was mirrored: swap the bottom-left and the top-right points.
            var data = decoderResult.Other as QRCodeDecoderMetaData;
            if (data != null)
            {
                data.applyMirroredCorrection(points);
            }

            var result = new Result(decoderResult.Text, decoderResult.RawBytes, points, BarcodeFormat.QR_CODE);
            var byteSegments = decoderResult.ByteSegments;
            if (byteSegments != null)
            {
                result.putMetadata(ResultMetadataType.BYTE_SEGMENTS, byteSegments);
            }
            var ecLevel = decoderResult.ECLevel;
            if (ecLevel != null)
            {
                result.putMetadata(ResultMetadataType.ERROR_CORRECTION_LEVEL, ecLevel);
            }
            if (decoderResult.StructuredAppend)
            {
                result.putMetadata(ResultMetadataType.STRUCTURED_APPEND_SEQUENCE, decoderResult.StructuredAppendSequenceNumber);
                result.putMetadata(ResultMetadataType.STRUCTURED_APPEND_PARITY, decoderResult.StructuredAppendParity);
            }
            return result;
        }

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

        /// <summary>
        /// This method detects a code in a "pure" image -- that is, pure monochrome image
        /// which contains only an unrotated, unskewed, image of a code, with some white border
        /// around it. This is a specialized method that works exceptionally fast in this special
        /// case.
        /// 
        /// <seealso cref="ZXing.Datamatrix.DataMatrixReader.extractPureBits(BitMatrix)" />
        /// </summary>
        private static BitMatrix extractPureBits(BitMatrix image)
        {
            int[] leftTopBlack = image.getTopLeftOnBit();
            int[] rightBottomBlack = image.getBottomRightOnBit();
            if (leftTopBlack == null || rightBottomBlack == null)
            {
                return null;
            }

            float moduleSize;
            if (!QRCodeReader.moduleSize(leftTopBlack, image, out moduleSize))
                return null;

            int top = leftTopBlack[1];
            int bottom = rightBottomBlack[1];
            int left = leftTopBlack[0];
            int right = rightBottomBlack[0];

            // Sanity check!
            if (left >= right || top >= bottom)
            {
                return null;
            }

            if (bottom - top != right - left)
            {
                // Special case, where bottom-right module wasn't black so we found something else in the last row
                // Assume it's a square, so use height as the width
                right = left + (bottom - top);
                if (right >= image.Width)
                {
                    // Abort if that would not make sense -- off image
                    return null;
                }
            }

            int matrixWidth = (int)Math.Round((right - left + 1) / moduleSize);
            int matrixHeight = (int)Math.Round((bottom - top + 1) / moduleSize);
            if (matrixWidth <= 0 || matrixHeight <= 0)
            {
                return null;
            }
            if (matrixHeight != matrixWidth)
            {
                // Only possibly decode square regions
                return null;
            }

            // Push in the "border" by half the module width so that we start
            // sampling in the middle of the module. Just in case the image is a
            // little off, this will help recover.
            int nudge = (int)(moduleSize / 2.0f);
            top += nudge;
            left += nudge;

            // But careful that this does not sample off the edge
            // "right" is the farthest-right valid pixel location -- right+1 is not necessarily
            // This is positive by how much the inner x loop below would be too large
            int nudgedTooFarRight = left + (int)((matrixWidth - 1) * moduleSize) - right;
            if (nudgedTooFarRight > 0)
            {
                if (nudgedTooFarRight > nudge)
                {
                    // Neither way fits; abort
                    return null;
                }
                left -= nudgedTooFarRight;
            }
            // See logic above
            int nudgedTooFarDown = top + (int)((matrixHeight - 1) * moduleSize) - bottom;
            if (nudgedTooFarDown > 0)
            {
                if (nudgedTooFarDown > nudge)
                {
                    // Neither way fits; abort
                    return null;
                }
                top -= nudgedTooFarDown;
            }

            // Now just read off the bits
            BitMatrix bits = new BitMatrix(matrixWidth, matrixHeight);
            for (int y = 0; y < matrixHeight; y++)
            {
                int iOffset = top + (int)(y * moduleSize);
                for (int x = 0; x < matrixWidth; x++)
                {
                    if (image[left + (int)(x * moduleSize), iOffset])
                    {
                        bits[x, y] = true;
                    }
                }
            }
            return bits;
        }

        private static bool moduleSize(int[] leftTopBlack, BitMatrix image, out float msize)
        {
            int height = image.Height;
            int width = image.Width;
            int x = leftTopBlack[0];
            int y = leftTopBlack[1];
            bool inBlack = true;
            int transitions = 0;
            while (x < width && y < height)
            {
                if (inBlack != image[x, y])
                {
                    if (++transitions == 5)
                    {
                        break;
                    }
                    inBlack = !inBlack;
                }
                x++;
                y++;
            }
            if (x == width || y == height)
            {
                msize = 0.0f;
                return false;
            }
            msize = (x - leftTopBlack[0]) / 7.0f;
            return true;
        }
    }
}