/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.
 */

package org.apache.datasketches.cpc;

import static org.apache.datasketches.common.Util.INVERSE_GOLDEN_U64;
import static org.apache.datasketches.common.Util.LS;
import static org.apache.datasketches.common.Util.ceilingPowerOf2;
import static org.apache.datasketches.common.Util.log2;
import static org.apache.datasketches.common.Util.powerSeriesNextDouble;
import static org.apache.datasketches.cpc.CompressedState.importFromSegment;
import static org.apache.datasketches.cpc.RuntimeAsserts.rtAssert;

import java.lang.foreign.MemorySegment;
import java.io.PrintStream;
import java.io.PrintWriter;

import org.apache.datasketches.common.SuppressFBWarnings;
import org.apache.datasketches.common.Util;

/**
 * This code is used both by unit tests, for short running tests,
 * and by the characterization repository for longer running, more exhaustive testing. To be
 * accessible for both, this code is part of the main hierarchy. It is not used during normal
 * production runtime.
 *
 * @author Lee Rhodes
 * @author Kevin Lang
 */
public class CompressionCharacterization {
  private String hfmt;
  private String dfmt;
  private String[] hStrArr;
  private long vIn = 0;

  //inputs
  private final int lgMinK;
  private final int lgMaxK; //inclusive
  private final int lgMinT; //Trials at end
  private final int lgMaxT; //Trials at start
  private final int lgMulK; //multiplier of K to produce maxU
  private final int uPPO;
  private final int incLgK; //increment of lgK
  private final PrintStream ps;
  private final PrintWriter pw;

  //intermediates
  private CpcSketch[] streamSketches;
  private CompressedState[] compressedStates1;
  private MemorySegment[] segArr;
  private CompressedState[] compressedStates2;
  private CpcSketch[] unCompressedSketches;

  /**
   * Only used in test.
   * @param lgMinK min lgK
   * @param lgMaxK max lgK
   * @param lgMinT min lgTrials
   * @param lgMaxT max lgTrials
   * @param lgMulK lg multiple
   * @param uPPO unique axis Points Per Octave
   * @param incLgK increment lgK
   * @param pS PrintStream
   * @param pW PrintWriter
   */
  @SuppressFBWarnings(value = "EI_EXPOSE_REP2", justification = "This is OK here")
  public CompressionCharacterization(
      final int lgMinK,
      final int lgMaxK,
      final int lgMinT,
      final int lgMaxT,
      final int lgMulK,
      final int uPPO,
      final int incLgK,
      final PrintStream pS,
      final PrintWriter pW) {
    this.lgMinK = lgMinK;
    this.lgMaxK = lgMaxK;
    this.lgMinT = lgMinT;
    this.lgMaxT = lgMaxT;
    this.lgMulK = lgMulK;
    this.uPPO = Math.max(uPPO, 1);
    this.incLgK = Math.max(incLgK, 1);
    ps = pS;
    pw = pW;
    assembleFormats();
  }

  /**
   * Only used in test
   */
  public void start() {
    printf(hfmt, (Object[]) hStrArr); //print header
    doRangeOfLgK();
  }

  private void doRangeOfLgK() {
    for (int lgK = lgMinK; lgK <= lgMaxK; lgK += incLgK) {
      doRangeOfNAtLgK(lgK);
    }
  }

  private void doRangeOfNAtLgK(final int lgK) {
    long n = 1;
    final int lgMaxN = lgK + lgMulK;
    final long maxN = 1L << lgMaxN;
    final double slope = -(double)(lgMaxT - lgMinT) / lgMaxN;

    while (n <= maxN) {
      final double lgT = (slope * log2(n)) + lgMaxT;
      final int totTrials = Math.max(ceilingPowerOf2((int) Math.pow(2.0, lgT)), (1 << lgMinT));
      doTrialsAtLgKAtN(lgK, n, totTrials);
      n = Math.round(powerSeriesNextDouble(uPPO, n, true, 2.0));
    }
  }

  private void doTrialsAtLgKAtN(final int lgK, final long n, final int totalTrials) {
    final int k = 1 << lgK;
    final int minNK = (int) ((k < n) ? k : n);
    final double nOverK = (double) n / k;
    final int lgTotTrials = Integer.numberOfTrailingZeros(totalTrials);
    final int lgWaves = Math.max(lgTotTrials - 10, 0);
    final int trialsPerWave = 1 << (lgTotTrials - lgWaves);
    //printf("%d %d %d %d\n", totalTrials, lgTotTrials, 1 << lgWaves, trialsPerWave);
    streamSketches = new CpcSketch[trialsPerWave];
    compressedStates1 = new CompressedState[trialsPerWave];
    segArr = new MemorySegment[trialsPerWave];
    compressedStates2 = new CompressedState[trialsPerWave];
    unCompressedSketches = new CpcSketch[trialsPerWave];


    //update: fill, compress, uncompress sketches arrays in waves
    long totalC = 0;
    long totalW = 0;
    long sumCtor_nS = 0;
    long sumUpd_nS = 0;
    long sumCom_nS = 0;
    long sumSer_nS = 0;
    long sumDes_nS = 0;
    long sumUnc_nS = 0;
    long sumEqu_nS = 0;
    long nanoStart, nanoEnd;
    final long start = System.currentTimeMillis();
    //Wave Loop
    for (int w = 0; w < (1 << lgWaves); w++) {

      //Construct array with sketches loop
      nanoStart = System.nanoTime();
      for (int trial = 0; trial < trialsPerWave; trial++) {
        final CpcSketch sketch = new CpcSketch(lgK);
        streamSketches[trial] = sketch;
      }
      nanoEnd = System.nanoTime();
      sumCtor_nS += nanoEnd - nanoStart;
      nanoStart = nanoEnd;

      //Sketch Update loop
      for (int trial = 0; trial < trialsPerWave; trial++) {
        final CpcSketch sketch = streamSketches[trial];
        for (long i = 0; i < n; i++) { //increment loop
          sketch.update(vIn += INVERSE_GOLDEN_U64);
        }
      }
      nanoEnd = System.nanoTime();
      sumUpd_nS += nanoEnd - nanoStart;
      nanoStart = nanoEnd;

      //Compress loop
      for (int trial = 0; trial < trialsPerWave; trial++) {
        final CpcSketch sketch = streamSketches[trial];
        final CompressedState state = CompressedState.compress(sketch);
        compressedStates1[trial] = state;
        totalC += sketch.numCoupons;
        totalW += state.csvLengthInts + state.cwLengthInts;
      }
      nanoEnd = System.nanoTime();
      sumCom_nS += nanoEnd - nanoStart;
      nanoStart = nanoEnd;

      //State to MemorySegment loop
      for (int trial = 0; trial < trialsPerWave; trial++) {
        final CompressedState state = compressedStates1[trial];
        final long cap = state.getRequiredSerializedBytes();
        final MemorySegment wseg = MemorySegment.ofArray(new byte[(int) cap]);
        state.exportToSegment(wseg);
        segArr[trial] = wseg;
      }

      nanoEnd = System.nanoTime();
      sumSer_nS += nanoEnd - nanoStart;
      nanoStart = nanoEnd;

      //MemorySegment to State loop
      for (int trial = 0; trial < trialsPerWave; trial++) {
        final MemorySegment seg = segArr[trial];
        final CompressedState state = importFromSegment(seg);
        compressedStates2[trial] = state;
      }

      nanoEnd = System.nanoTime();
      sumDes_nS += nanoEnd - nanoStart;
      nanoStart = nanoEnd;

      //Uncompress loop
      for (int trial = 0; trial < trialsPerWave; trial++) {
        final CompressedState state = compressedStates2[trial];
        CpcSketch uncSk = null;
        uncSk = CpcSketch.uncompress(state, Util.DEFAULT_UPDATE_SEED);
        unCompressedSketches[trial] = uncSk;
      }

      nanoEnd = System.nanoTime();
      sumUnc_nS += nanoEnd - nanoStart;
      nanoStart = nanoEnd;

      //Equals check
      for (int trial = 0; trial < trialsPerWave; trial++) {
        rtAssert(TestUtil.specialEquals(streamSketches[trial], unCompressedSketches[trial], false, false));
      }

      nanoEnd = System.nanoTime();
      sumEqu_nS += nanoEnd - nanoStart;
      nanoStart = nanoEnd;

    } // end wave loop

    final double total_S = (System.currentTimeMillis() - start) / 1E3;
    final double avgC = (1.0 * totalC) / totalTrials;
    final double avgCoK = avgC / k;
    final double avgWords = (1.0 * totalW) / totalTrials;
    final double avgBytes = (4.0 * totalW) / totalTrials;

    final double avgCtor_nS = Math.round((double) sumCtor_nS / totalTrials);

    final double avgUpd_nS = Math.round((double) sumUpd_nS / totalTrials);
    final double avgUpd_nSperN = avgUpd_nS / n;

    final double avgCom_nS = Math.round((double) sumCom_nS / totalTrials);
    final double avgCom_nSper2C = avgCom_nS / (2.0 * avgC);
    final double avgCom_nSperK = avgCom_nS / k;

    final double avgSer_nS = Math.round((double) sumSer_nS / totalTrials);
    final double avgSer_nSperW = avgSer_nS / avgWords;

    final double avgDes_nS = Math.round((double) sumDes_nS / totalTrials);
    final double avgDes_nSperW = avgDes_nS / avgWords;


    final double avgUnc_nS = Math.round((double) sumUnc_nS / totalTrials);
    final double avgUnc_nSper2C = avgUnc_nS / (2.0 * avgC);
    final double avgUnc_nSperK = avgUnc_nS / k;

    final double avgEqu_nS = Math.round((double) sumEqu_nS / totalTrials);
    final double avgEqu_nSperMinNK = avgEqu_nS / minNK;


    final int len = unCompressedSketches.length;
    final Flavor finFlavor = unCompressedSketches[len - 1].getFlavor();
    final String offStr = Integer.toString(unCompressedSketches[len - 1].windowOffset);
    final String flavorOff = finFlavor.toString() + String.format("%2s", offStr);
    printf(dfmt,
        lgK,
        totalTrials,
        n,
        minNK,
        avgCoK,
        flavorOff,
        nOverK,
        avgBytes,
        avgCtor_nS,
        avgUpd_nS,
        avgCom_nS,
        avgSer_nS,
        avgDes_nS,
        avgUnc_nS,
        avgEqu_nS,
        avgUpd_nSperN,
        avgCom_nSper2C,
        avgCom_nSperK,
        avgSer_nSperW,
        avgDes_nSperW,
        avgUnc_nSper2C,
        avgUnc_nSperK,
        avgEqu_nSperMinNK,
        total_S);
  }

  private void printf(final String format, final Object ... args) {
    if (ps != null) { ps.printf(format, args); }
    if (pw != null) { pw.printf(format, args); }
  }

  private void assembleFormats() {
    final String[][] assy = {
        {"lgK",        "%3s",  "%3d"},
        {"Trials",     "%9s",  "%9d"},
        {"n",          "%12s", "%12d"},
        {"MinKN",      "%9s",  "%9d"},
        {"AvgC/K",     "%9s",  "%9.4g"},
        {"FinFlavor",  "%11s",  "%11s"},
        {"N/K",        "%9s",  "%9.4g"},
        {"AvgBytes",   "%9s",  "%9.0f"},
        {"AvgCtor_nS", "%11s", "%11.0f"},
        {"AvgUpd_nS",  "%10s", "%10.4e"},
        {"AvgCom_nS",  "%10s", "%10.0f"},
        {"AvgSer_nS",  "%10s", "%10.2f"},
        {"AvgDes_nS",  "%10s", "%10.2f"},
        {"AvgUnc_nS",  "%10s", "%10.0f"},
        {"AvgEqu_nS",  "%10s", "%10.0f"},
        {"AvgUpd_nSperN",     "%14s", "%14.2f"},
        {"AvgCom_nSper2C",    "%15s", "%15.4g"},
        {"AvgCom_nSperK",     "%14s", "%14.4g"},
        {"AvgSer_nSperW",     "%14s", "%14.2f"},
        {"AvgDes_nSperW",     "%14s", "%14.2f"},
        {"AvgUnc_nSper2C",    "%15s", "%15.4g"},
        {"AvgUnc_nSperK",     "%14s", "%14.4g"},
        {"AvgEqu_nSperMinNK", "%18s", "%18.4g"},
        {"Total_S",           "%8s",  "%8.3f"}
    };
    final int cols = assy.length;
    hStrArr = new String[cols];
    final StringBuilder headerFmt = new StringBuilder();
    final StringBuilder dataFmt = new StringBuilder();
    headerFmt.append(LS + "Compression Characterization" + LS);
    for (int i = 0; i < cols; i++) {
      hStrArr[i] = assy[i][0];
      headerFmt.append(assy[i][1]);
      headerFmt.append((i < (cols - 1)) ? "\t" : LS);
      dataFmt.append(assy[i][2]);
      dataFmt.append((i < (cols - 1)) ? "\t" : LS);
    }
    hfmt = headerFmt.toString();
    dfmt = dataFmt.toString();
  }
}
