package eu.openaire.urls_controller.util;

import com.google.common.collect.HashMultimap;
import eu.openaire.urls_controller.models.Task;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.configurationprocessor.json.JSONException;
import org.springframework.boot.configurationprocessor.json.JSONObject;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.Resource;
import org.springframework.stereotype.Component;

import java.io.IOException;
import java.io.InputStream;
import java.util.Scanner;

@Component
public class TestFileUtils {

    private static final Logger logger = LoggerFactory.getLogger(TestFileUtils.class);

    public Resource testResource = new ClassPathResource("testInputFiles/orderedList1000.json");

    public ThreadLocal<Integer> duplicateIdUrlEntries;
    public ThreadLocal<Scanner> inputScanner;   // On each request, a new thread is spawned to handle it. So, a new inputScanner is needed.

    private final int jsonBatchSize = 3000;
    private ThreadLocal<Integer> fileIndex;
    private ThreadLocal<Integer> unretrievableInputLines;

    private final String utf8Charset = "UTF-8";


    public TestFileUtils() throws IOException {
        InputStream inputStream = testResource.getInputStream();
        inputScanner = ThreadLocal.withInitial(() -> new Scanner(inputStream, utf8Charset));
        fileIndex = ThreadLocal.withInitial(() -> 0);
        unretrievableInputLines = ThreadLocal.withInitial(() -> 0);
        duplicateIdUrlEntries = ThreadLocal.withInitial(() -> 0);
    }


    /**
     * This method parses a Json file and extracts the urls, along with the IDs.
     * @return HashMultimap<String, String>
     */
    public HashMultimap<String, String> getNextIdUrlPairBatchFromJson() {
        Task inputIdUrlTuple;
        int expectedPathsPerID = 5;
        int expectedIDsPerBatch = jsonBatchSize / expectedPathsPerID;

        HashMultimap<String, String> idAndUrlMappedInput = HashMultimap.create(expectedIDsPerBatch, expectedPathsPerID);
        int curBeginning = fileIndex.get();

        while ( inputScanner.get().hasNextLine() && (fileIndex.get() < (curBeginning + jsonBatchSize)) )
        {// While (!EOF) and inside the current url-batch, iterate through lines.

            //logger.debug("fileIndex: " + FileUtils.fileIndex.get());	// DEBUG!

            // Take each line, remove potential double quotes.
            String retrievedLineStr = inputScanner.get().nextLine();
            //logger.debug("Loaded from inputFile: " + retrievedLineStr);	// DEBUG!

            fileIndex.set(fileIndex.get() +1);

            if ( retrievedLineStr.isEmpty() ) {
                unretrievableInputLines.set(unretrievableInputLines.get() +1);
                continue;
            }

            if ( (inputIdUrlTuple = jsonDecoder(retrievedLineStr)) == null ) {	// Decode the jsonLine and take the two attributes.
                logger.warn("A problematic inputLine found: \t" + retrievedLineStr);
                unretrievableInputLines.set(unretrievableInputLines.get() +1);
                continue;
            }

            if ( !idAndUrlMappedInput.put(inputIdUrlTuple.getId(), inputIdUrlTuple.getUrl()) ) {    // We have a duplicate url in the input.. log it here as we cannot pass it through the HashMultimap. It's possible that this as well as the original might be/give a docUrl.
                duplicateIdUrlEntries.set(duplicateIdUrlEntries.get() +1);
            }
        }

        return idAndUrlMappedInput;
    }


    /**
     * This method decodes a Json String and returns its members.
     * @param jsonLine String
     * @return HashMap<String,String>
     */
    private Task jsonDecoder(String jsonLine) {
        // Get ID and url and put them in the HashMap
        String idStr = null;
        String urlStr = null;
        try {
            JSONObject jObj = new JSONObject(jsonLine); // Construct a JSONObject from the retrieved jsonLine.
            idStr = jObj.get("id").toString();
            urlStr = jObj.get("url").toString();
        } catch (JSONException je) {
            logger.warn("JSONException caught when tried to parse and extract values from jsonLine: \t" + jsonLine, je);
            return null;
        }

        if ( urlStr.isEmpty() ) {
            if ( !idStr.isEmpty() )	// If we only have the id, then go and log it.
                logger.warn("The url was not found for id: \"" + idStr + "\"");
            return null;
        }
        return new Task(idStr, urlStr, null);
    }


    /**
     * This method checks if there is no more input-data and returns true in that case.
     * Otherwise, it returns false, if there is more input-data to be loaded.
     * A "RuntimeException" is thrown if no input-urls were retrieved in general.
     * @param isEmptyOfData
     * @param isFirstRun
     * @return finished loading / not finished
     */
    public boolean isFinishedLoading(boolean isEmptyOfData, boolean isFirstRun) {
        if ( isEmptyOfData ) {
            if ( isFirstRun )
                logger.error("Could not retrieve any urls from the inputFile!");
            else
                logger.debug("Done loading " + getCurrentlyLoadedUrls() + " urls from the inputFile.");
            return true;
        }
        return false;
    }


    /**
     * This method returns the number of (non-heading, non-empty) lines we have read from the inputFile.
     * @return loadedUrls
     */
    private int getCurrentlyLoadedUrls() {	// In the end, it gives the total number of urls we have processed.
        return fileIndex.get() - unretrievableInputLines.get();
    }

}