text: 'use strict';
  
  const color = require('color');
  const is = require('./is');
  const sharp = require('../build/Release/sharp.node');
  
  /**
   * Extract input options, if any, from an object.
   * @private
   */
  function _inputOptionsFromObject (obj) {
    const { raw, density, limitInputPixels, sequentialRead, failOnError } = obj;
    return [raw, density, limitInputPixels, sequentialRead, failOnError].some(is.defined)
      ? { raw, density, limitInputPixels, sequentialRead, failOnError }
      : undefined;
  }
  
  /**
   * Create Object containing input and input-related options.
   * @private
   */
  function _createInputDescriptor (input, inputOptions, containerOptions) {
    const inputDescriptor = {
      failOnError: true,
      limitInputPixels: Math.pow(0x3FFF, 2),
      sequentialRead: false
    };
    if (is.string(input)) {
      // filesystem
      inputDescriptor.file = input;
    } else if (is.buffer(input)) {
      // Buffer
      inputDescriptor.buffer = input;
    } else if (is.plainObject(input) && !is.defined(inputOptions)) {
      // Plain Object descriptor, e.g. create
      inputOptions = input;
      if (_inputOptionsFromObject(inputOptions)) {
        // Stream with options
        inputDescriptor.buffer = [];
      }
    } else if (!is.defined(input) && !is.defined(inputOptions) && is.object(containerOptions) && containerOptions.allowStream) {
      // Stream without options
      inputDescriptor.buffer = [];
    } else {
      throw new Error(`Unsupported input '${input}' of type ${typeof input}${
        is.defined(inputOptions) ? ` when also providing options of type ${typeof inputOptions}` : ''
      }`);
    }
    if (is.object(inputOptions)) {
      // Fail on error
      if (is.defined(inputOptions.failOnError)) {
        if (is.bool(inputOptions.failOnError)) {
          inputDescriptor.failOnError = inputOptions.failOnError;
        } else {
          throw is.invalidParameterError('failOnError', 'boolean', inputOptions.failOnError);
        }
      }
      // Density
      if (is.defined(inputOptions.density)) {
        if (is.inRange(inputOptions.density, 1, 2400)) {
          inputDescriptor.density = inputOptions.density;
        } else {
          throw is.invalidParameterError('density', 'number between 1 and 2400', inputOptions.density);
        }
      }
      // limitInputPixels
      if (is.defined(inputOptions.limitInputPixels)) {
        if (is.bool(inputOptions.limitInputPixels)) {
          inputDescriptor.limitInputPixels = inputOptions.limitInputPixels
            ? Math.pow(0x3FFF, 2)
            : 0;
        } else if (is.integer(inputOptions.limitInputPixels) && inputOptions.limitInputPixels >= 0) {
          inputDescriptor.limitInputPixels = inputOptions.limitInputPixels;
        } else {
          throw is.invalidParameterError('limitInputPixels', 'integer >= 0', inputOptions.limitInputPixels);
        }
      }
      // sequentialRead
      if (is.defined(inputOptions.sequentialRead)) {
        if (is.bool(inputOptions.sequentialRead)) {
          inputDescriptor.sequentialRead = inputOptions.sequentialRead;
        } else {
          throw is.invalidParameterError('sequentialRead', 'boolean', inputOptions.sequentialRead);
        }
      }
      // Raw pixel input
      if (is.defined(inputOptions.raw)) {
        if (
          is.object(inputOptions.raw) &&
          is.integer(inputOptions.raw.width) && inputOptions.raw.width > 0 &&
          is.integer(inputOptions.raw.height) && inputOptions.raw.height > 0 &&
          is.integer(inputOptions.raw.channels) && is.inRange(inputOptions.raw.channels, 1, 4)
        ) {
          inputDescriptor.rawWidth = inputOptions.raw.width;
          inputDescriptor.rawHeight = inputOptions.raw.height;
          inputDescriptor.rawChannels = inputOptions.raw.channels;
        } else {
          throw new Error('Expected width, height and channels for raw pixel input');
        }
      }
      // Multi-page input (GIF, TIFF, PDF)
      if (is.defined(inputOptions.pages)) {
        if (is.integer(inputOptions.pages) && is.inRange(inputOptions.pages, -1, 100000)) {
          inputDescriptor.pages = inputOptions.pages;
        } else {
          throw is.invalidParameterError('pages', 'integer between -1 and 100000', inputOptions.pages);
        }
      }
      if (is.defined(inputOptions.page)) {
        if (is.integer(inputOptions.page) && is.inRange(inputOptions.page, 0, 100000)) {
          inputDescriptor.page = inputOptions.page;
        } else {
          throw is.invalidParameterError('page', 'integer between 0 and 100000', inputOptions.page);
        }
      }
      // Multi-level input (OpenSlide)
      if (is.defined(inputOptions.level)) {
        if (is.integer(inputOptions.level) && is.inRange(inputOptions.level, 0, 256)) {
          inputDescriptor.level = inputOptions.level;
        } else {
          throw is.invalidParameterError('level', 'integer between 0 and 256', inputOptions.level);
        }
      }
      // Create new image
      if (is.defined(inputOptions.create)) {
        if (
          is.object(inputOptions.create) &&
          is.integer(inputOptions.create.width) && inputOptions.create.width > 0 &&
          is.integer(inputOptions.create.height) && inputOptions.create.height > 0 &&
          is.integer(inputOptions.create.channels) && is.inRange(inputOptions.create.channels, 3, 4) &&
          is.defined(inputOptions.create.background)
        ) {
          inputDescriptor.createWidth = inputOptions.create.width;
          inputDescriptor.createHeight = inputOptions.create.height;
          inputDescriptor.createChannels = inputOptions.create.channels;
          const background = color(inputOptions.create.background);
          inputDescriptor.createBackground = [
            background.red(),
            background.green(),
            background.blue(),
            Math.round(background.alpha() * 255)
          ];
          delete inputDescriptor.buffer;
        } else {
          throw new Error('Expected width, height, channels and background to create a new input image');
        }
      }
    } else if (is.defined(inputOptions)) {
      throw new Error('Invalid input options ' + inputOptions);
    }
    return inputDescriptor;
  }
  
  /**
   * Handle incoming Buffer chunk on Writable Stream.
   * @private
   * @param {Buffer} chunk
   * @param {string} encoding - unused
   * @param {Function} callback
   */
  function _write (chunk, encoding, callback) {
    /* istanbul ignore else */
    if (Array.isArray(this.options.input.buffer)) {
      /* istanbul ignore else */
      if (is.buffer(chunk)) {
        if (this.options.input.buffer.length === 0) {
          this.on('finish', () => {
            this.streamInFinished = true;
          });
        }
        this.options.input.buffer.push(chunk);
        callback();
      } else {
        callback(new Error('Non-Buffer data on Writable Stream'));
      }
    } else {
      callback(new Error('Unexpected data on Writable Stream'));
    }
  }
  
  /**
   * Flattens the array of chunks accumulated in input.buffer.
   * @private
   */
  function _flattenBufferIn () {
    if (this._isStreamInput()) {
      this.options.input.buffer = Buffer.concat(this.options.input.buffer);
    }
  }
  
  /**
   * Are we expecting Stream-based input?
   * @private
   * @returns {boolean}
   */
  function _isStreamInput () {
    return Array.isArray(this.options.input.buffer);
  }
  
  /**
   * Fast access to (uncached) image metadata without decoding any compressed image data.
   * A `Promise` is returned when `callback` is not provided.
   *
   * - `format`: Name of decoder used to decompress image data e.g. `jpeg`, `png`, `webp`, `gif`, `svg`
   * - `size`: Total size of image in bytes, for Stream and Buffer input only
   * - `width`: Number of pixels wide (EXIF orientation is not taken into consideration)
   * - `height`: Number of pixels high (EXIF orientation is not taken into consideration)
   * - `space`: Name of colour space interpretation e.g. `srgb`, `rgb`, `cmyk`, `lab`, `b-w` [...](https://libvips.github.io/libvips/API/current/VipsImage.html#VipsInterpretation)
   * - `channels`: Number of bands e.g. `3` for sRGB, `4` for CMYK
   * - `depth`: Name of pixel depth format e.g. `uchar`, `char`, `ushort`, `float` [...](https://libvips.github.io/libvips/API/current/VipsImage.html#VipsBandFormat)
   * - `density`: Number of pixels per inch (DPI), if present
   * - `chromaSubsampling`: String containing JPEG chroma subsampling, `4:2:0` or `4:4:4` for RGB, `4:2:0:4` or `4:4:4:4` for CMYK
   * - `isProgressive`: Boolean indicating whether the image is interlaced using a progressive scan
   * - `pages`: Number of pages/frames contained within the image, with support for TIFF, HEIF, PDF, animated GIF and animated WebP
   * - `pageHeight`: Number of pixels high each page in a multi-page image will be.
   * - `loop`: Number of times to loop an animated image, zero refers to a continuous loop.
   * - `delay`: Delay in ms between each page in an animated image, provided as an array of integers.
   * - `pagePrimary`: Number of the primary page in a HEIF image
   * - `levels`: Details of each level in a multi-level image provided as an array of objects, requires libvips compiled with support for OpenSlide
   * - `hasProfile`: Boolean indicating the presence of an embedded ICC profile
   * - `hasAlpha`: Boolean indicating the presence of an alpha transparency channel
   * - `orientation`: Number value of the EXIF Orientation header, if present
   * - `exif`: Buffer containing raw EXIF data, if present
   * - `icc`: Buffer containing raw [ICC](https://www.npmjs.com/package/icc) profile data, if present
   * - `iptc`: Buffer containing raw IPTC data, if present
   * - `xmp`: Buffer containing raw XMP data, if present
   * - `tifftagPhotoshop`: Buffer containing raw TIFFTAG_PHOTOSHOP data, if present
   *
   * @example
   * const image = sharp(inputJpg);
   * image
   *   .metadata()
   *   .then(function(metadata) {
   *     return image
   *       .resize(Math.round(metadata.width / 2))
   *       .webp()
   *       .toBuffer();
   *   })
   *   .then(function(data) {
   *     // data contains a WebP image half the width and height of the original JPEG
   *   });
   *
   * @param {Function} [callback] - called with the arguments `(err, metadata)`
   * @returns {Promise<Object>|Sharp}
   */
  function metadata (callback) {
    if (is.fn(callback)) {
      if (this._isStreamInput()) {
        this.on('finish', () => {
          this._flattenBufferIn();
          sharp.metadata(this.options, callback);
        });
      } else {
        sharp.metadata(this.options, callback);
      }
      return this;
    } else {
      if (this._isStreamInput()) {
        return new Promise((resolve, reject) => {
          this.on('finish', () => {
            this._flattenBufferIn();
            sharp.metadata(this.options, (err, metadata) => {
              if (err) {
                reject(err);
              } else {
                resolve(metadata);
              }
            });
          });
        });
      } else {
        return new Promise((resolve, reject) => {
          sharp.metadata(this.options, (err, metadata) => {
            if (err) {
              reject(err);
            } else {
              resolve(metadata);
            }
          });
        });
      }
    }
  }
  
  /**
   * Access to pixel-derived image statistics for every channel in the image.
   * A `Promise` is returned when `callback` is not provided.
   *
   * - `channels`: Array of channel statistics for each channel in the image. Each channel statistic contains
   *     - `min` (minimum value in the channel)
   *     - `max` (maximum value in the channel)
   *     - `sum` (sum of all values in a channel)
   *     - `squaresSum` (sum of squared values in a channel)
   *     - `mean` (mean of the values in a channel)
   *     - `stdev` (standard deviation for the values in a channel)
   *     - `minX` (x-coordinate of one of the pixel where the minimum lies)
   *     - `minY` (y-coordinate of one of the pixel where the minimum lies)
   *     - `maxX` (x-coordinate of one of the pixel where the maximum lies)
   *     - `maxY` (y-coordinate of one of the pixel where the maximum lies)
   * - `isOpaque`: Is the image fully opaque? Will be `true` if the image has no alpha channel or if every pixel is fully opaque.
   * - `entropy`: Histogram-based estimation of greyscale entropy, discarding alpha channel if any (experimental)
   * - `sharpness`: Estimation of greyscale sharpness based on the standard deviation of a Laplacian convolution, discarding alpha channel if any (experimental)
   *
   * @example
   * const image = sharp(inputJpg);
   * image
   *   .stats()
   *   .then(function(stats) {
   *      // stats contains the channel-wise statistics array and the isOpaque value
   *   });
   *
   * @example
   * const { entropy, sharpness } = await sharp(input).stats();
   *
   * @param {Function} [callback] - called with the arguments `(err, stats)`
   * @returns {Promise<Object>}
   */
  function stats (callback) {
    if (is.fn(callback)) {
      if (this._isStreamInput()) {
        this.on('finish', () => {
          this._flattenBufferIn();
          sharp.stats(this.options, callback);
        });
      } else {
        sharp.stats(this.options, callback);
      }
      return this;
    } else {
      if (this._isStreamInput()) {
        return new Promise((resolve, reject) => {
          this.on('finish', function () {
            this._flattenBufferIn();
            sharp.stats(this.options, (err, stats) => {
              if (err) {
                reject(err);
              } else {
                resolve(stats);
              }
            });
          });
        });
      } else {
        return new Promise((resolve, reject) => {
          sharp.stats(this.options, (err, stats) => {
            if (err) {
              reject(err);
            } else {
              resolve(stats);
            }
          });
        });
      }
    }
  }
  
  /**
   * Decorate the Sharp prototype with input-related functions.
   * @private
   */
  module.exports = function (Sharp) {
    Object.assign(Sharp.prototype, {
      // Private
      _inputOptionsFromObject,
      _createInputDescriptor,
      _write,
      _flattenBufferIn,
      _isStreamInput,
      // Public
      metadata,
      stats
    });
  };
  