import org.apache.commons.math3.stat.descriptive.DescriptiveStatistics

import com.drew.imaging.ImageMetadataReader
import com.drew.metadata.Metadata
import com.drew.metadata.exif.ExifIFD0Directory;
import com.drew.metadata.exif.ExifSubIFDDirectory

/**
 * Prints a bunch of stats for Exif related data
 * using metadata-extractor
 *
 * @author Frederic Schmaljohann
 */
class ExifAnalyzer {

	/**
	 * File extension of image files
	 */
	static final String REGEX_PICTURE_FILE = /.*jpg|.*cr2/

	/**
	 * Directory to be traversed (recursively)
	 */
	static final String IMAGE_DIR = 'SOME_DIR'

	static final String SEPARATOR = '==='
	
	DescriptiveStatistics focalLengths = new DescriptiveStatistics()
	DescriptiveStatistics isos = new DescriptiveStatistics()
	DescriptiveStatistics apertures = new DescriptiveStatistics()

	/**
	 * Computes descriptive stats for focal length, iso and aperture values 
	 * @return
	 */
	def computeStats() {
		new File(IMAGE_DIR).traverse {
			if (it.isFile() && it.canonicalPath.toLowerCase() ==~ REGEX_PICTURE_FILE) {
				try {
					extractData(it.canonicalPath)
				}
				catch (e) {
					println e.message
				}
			}
		}
	}

	private printStats() {
		println SEPARATOR + 'Focal length' + SEPARATOR
		printStats(focalLengths)
		println '\n' + SEPARATOR + 'ISO' + SEPARATOR
		printStats(isos)
		println '\n' + SEPARATOR + 'Apertures' + SEPARATOR
		printStats(apertures)
	}

	/**
	 * Extract the data and put it into statistics
	 * @param pictureFile
	 * @return
	 */
	private extractData(String pictureFile) {
		Metadata meta = ImageMetadataReader.readMetadata(new File(pictureFile))
		ExifSubIFDDirectory dir = meta.getDirectory(ExifSubIFDDirectory.class)
		ExifIFD0Directory dir2 = meta.getDirectory(ExifIFD0Directory.class)
		focalLengths.addValue(Double.parseDouble(dir.getString(ExifSubIFDDirectory.TAG_FOCAL_LENGTH)))
		isos.addValue(Double.parseDouble(dir.getString(ExifSubIFDDirectory.TAG_ISO_EQUIVALENT)))
		double aperture = computeAperture(dir.getString(ExifSubIFDDirectory.TAG_APERTURE))
		apertures.addValue(aperture)
	}
	
	/**
	 * Compute aperture
	 * @param apertureString
	 * @return
	 */
	def computeAperture(String apertureString) {
		Math.round(Math.pow(2, (parseFraction() / 2)) * 10) / 10
	}

	/**
	 * Print statistics
	 * @param stats
	 * @return
	 */
	def printStats(DescriptiveStatistics stats) {
		println stats
		printFrequencies(stats.sortedValues)
	}

	/**
	 * parses a double or fraction, e.g. 127/56 or 12.4
	 * @param stringToParse
	 * @return
	 */
	def double parseFraction(String stringToParse) {
		if (stringToParse.indexOf('/') == -1) {
			return Double.parseDouble(stringToParse)
		}
		double d = Double.parseDouble(stringToParse.substring(0, stringToParse.indexOf('/')))
		d /= Double.parseDouble(stringToParse.substring(stringToParse.indexOf('/')+1))
	}

	/**
	 * Print the frequencies
	 * @param sortedArray
	 */
	def printFrequencies(double[] sortedArray) {
		double currValue = sortedArray[0]
		int currCounter = 1
		for (int i=0;i < sortedArray.size(); i++) {
			if (currValue == sortedArray[i]) {
				currCounter++
			}
			else {
				println currValue + '->' + currCounter
				currValue = sortedArray[i]
			}
		}
	}
}

ExifAnalyzer ee = new ExifAnalyzer()
ee.computeStats()
ee.printStats()