package org.sysmon.agent.beans;

import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.List;

import org.apache.camel.spi.Configurer;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.sysmon.shared.MetricBean;
import org.sysmon.shared.MetricMeasurement;
import org.sysmon.shared.MetricResult;

@Configurer
public class DiskBean implements MetricBean {

    private final static Logger log = LoggerFactory.getLogger(DiskBean.class);

    private List<LinuxDiskStat> currentDiskStats;
    private List<LinuxDiskStat> previousDiskStats;


    @Override
    public MetricResult getMetrics() {

        MetricResult result = new MetricResult("disk");
        try {
            copyCurrentValues();
            readProcFile();
            result.setMeasurementList(calculate());
        } catch (IOException e) {
            e.printStackTrace();
        }

        return result;
    }



    private void readProcFile() throws IOException {

        currentDiskStats = new ArrayList<>();
        List<String> allLines = Files.readAllLines(Paths.get("/proc/diskstats"), StandardCharsets.UTF_8);
        for(String line : allLines) {
            currentDiskStats.add(new LinuxDiskStat(line));
        }

    }


    private void copyCurrentValues() {

        if(currentDiskStats != null && currentDiskStats.size() > 0) {
            previousDiskStats = new ArrayList<>(currentDiskStats);
        }

    }


    private List<MetricMeasurement> calculate() {

        List<MetricMeasurement> measurementList = new ArrayList<>();

        if(previousDiskStats == null || previousDiskStats.size() != currentDiskStats.size()) {
            return measurementList;
        }


        for(int i = 0; i < currentDiskStats.size(); i++) {

            LinuxDiskStat curStat = currentDiskStats.get(i);
            LinuxDiskStat preStat = previousDiskStats.get(i);

            if(curStat.device.startsWith("loop")) {
                continue;
            }

            // TODO: Calculate differences for wanted disk io stats
            measurementList.add(new MetricMeasurement(curStat.getDevice(), 0));

        }

        return measurementList;
    }


    public static class LinuxDiskStat {
    /*
        ==  ===================================
         1  major number
		 2  minor mumber
		 3  device name
		 4  reads completed successfully
		 5  reads merged
		 6  sectors read
		 7  time spent reading (ms)
		 8  writes completed
		 9  writes merged
		10  sectors written
		11  time spent writing (ms)
		12  I/Os currently in progress
		13  time spent doing I/Os (ms)
		14  weighted time spent doing I/Os (ms)
		==  ===================================

    Kernel 4.18+ appends four more fields for discard
    tracking putting the total at 18:

        ==  ===================================
        15  discards completed successfully
		16  discards merged
		17  sectors discarded
		18  time spent discarding
		==  ===================================

    Kernel 5.5+ appends two more fields for flush requests:

        ==  =====================================
        19  flush requests completed successfully
		20  time spent flushing
		==  =====================================
    */

        private final int major;
        private final int minor;
        private final String device;                // device name
        private final Long readsCompleted;          // successfully
        private final Long readsMerged;
        private final Long sectorsRead;             // 512 bytes pr. sector
        private final Long timeSpentReading;        // ms
        private final Long writesCompleted;         // successfully
        private final Long writesMerged;
        private final Long sectorsWritten;          // 512 bytes pr. sector
        private final Long timeSpentWriting;        // ms
        private final Long ioInProgress;
        private final Long timeSpentOnIo;           // ms
        private final Long timeSpentOnIoWeighted;

        private final Long discardsCompleted;       // successfully
        private final Long discardsMerged;
        private final Long sectorsDiscarded;        // 512 bytes pr. sector
        private final Long timeSpentDiscarding;     // ms

        private final Long flushRequestsCompleted;
        private final Long timeSpentFlushing;       // ms


        LinuxDiskStat(String procString) {

            String[] splitStr = procString.trim().split("\\s+");
            if(splitStr.length < 14) {
                throw new UnsupportedOperationException("Linux proc DISK string error: " + procString);
            }

            this.major = Integer.parseInt(splitStr[0]);
            this.minor = Integer.parseInt(splitStr[1]);
            this.device = splitStr[2];
            this.readsCompleted = Long.parseLong(splitStr[3]);
            this.readsMerged = Long.parseLong(splitStr[4]);
            this.sectorsRead = Long.parseLong(splitStr[5]);
            this.timeSpentReading = Long.parseLong(splitStr[6]);
            this.writesCompleted = Long.parseLong(splitStr[7]);
            this.writesMerged = Long.parseLong(splitStr[8]);
            this.sectorsWritten = Long.parseLong(splitStr[9]);
            this.timeSpentWriting = Long.parseLong(splitStr[10]);
            this.ioInProgress = Long.parseLong(splitStr[11]);
            this.timeSpentOnIo = Long.parseLong(splitStr[12]);
            this.timeSpentOnIoWeighted = Long.parseLong(splitStr[13]);

            if(splitStr.length >= 18) {
                this.discardsCompleted = Long.parseLong(splitStr[10]);
                this.discardsMerged = Long.parseLong(splitStr[11]);
                this.sectorsDiscarded = Long.parseLong(splitStr[12]);
                this.timeSpentDiscarding = Long.parseLong(splitStr[13]);
            } else {
                this.discardsCompleted = null;
                this.discardsMerged = null;
                this.sectorsDiscarded = null;
                this.timeSpentDiscarding = null;
            }

            if(splitStr.length == 20) {
                this.flushRequestsCompleted = Long.parseLong(splitStr[14]);
                this.timeSpentFlushing = Long.parseLong(splitStr[15]);
            } else {
                this.flushRequestsCompleted = null;
                this.timeSpentFlushing = null;
            }

        }

        public String getDevice() {
            return device;
        }


    }

}