package com.htopweb.system;

import org.junit.jupiter.api.Test;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import static org.junit.jupiter.api.Assertions.*;

class SystemProcessesServiceTest {

    @Test
    void parseProcessStat_lineWithParentheses() throws IOException {
        // Simulate a /proc/[pid]/stat line
        // pid (comm) state ppid pgrp session tty_nr tpgid flags minflt cminflt majflt cmajflt
        // utime stime cutime cstime priority nice num_threads itrealvalue starttime vsize rss ...
        String stat = "1234 (myprocess) S 1 1234 1234 0 -1 4194304 100 0 0 0 500 300 0 0 20 0 1 0 50 1048576 256 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0";

        int open = stat.indexOf('(');
        int close = stat.lastIndexOf(')');
        assertTrue(open >= 0);
        assertTrue(close > open);

        String name = stat.substring(open + 1, close);
        assertEquals("myprocess", name);

        String[] fields = stat.substring(close + 2).trim().split("\\s+");
        // fields[0] = state (field 3)
        // fields[11] = utime (field 14)
        // fields[12] = stime (field 15)
        // fields[19] = starttime (field 22)
        // fields[20] = vsize (field 23)
        // fields[21] = rss (field 24)
        assertTrue(fields.length >= 22);
        assertEquals("S", fields[0]);
        assertEquals(500, Long.parseLong(fields[11]));
        assertEquals(300, Long.parseLong(fields[12]));
    }

    @Test
    void calculateCpuUsage_deltaTicks() {
        long prevTicks = 1000L;
        long currTicks = 1500L;
        long clockTicksPerSecond = 100L;
        double elapsedSeconds = 5.0;
        int logicalProcessorCount = 4;

        long deltaTicks = currTicks - prevTicks;
        double cpuUsage = deltaTicks
                / (double) clockTicksPerSecond
                / elapsedSeconds
                * 100.0
                / logicalProcessorCount;

        // 500 ticks / 100 Hz / 5s * 100 / 4 cores = 25%
        assertEquals(25.0, cpuUsage, 0.01);
    }

    @Test
    void calculateCpuUsage_clampedTo100() {
        double rawUsage = 150.0;
        double clamped = Math.max(0.0, Math.min(100.0, rawUsage));
        assertEquals(100.0, clamped, 0.01);
    }

    @Test
    void calculateCpuUsage_negativeDeltaIgnored() {
        long prevTicks = 2000L;
        long currTicks = 1500L;
        long deltaTicks = currTicks - prevTicks;
        // Negative delta should be ignored
        if (deltaTicks >= 0) {
            fail("Delta should be negative");
        }
    }

    @Test
    void parseBootTime_fromStatFile() throws IOException {
        Path tempDir = Files.createTempDirectory("test");
        String stat = "btime 1700000000\n"
                + "procs 245\n";
        Files.writeString(tempDir.resolve("stat"), stat);

        long bootTime = 0L;
        for (String line : Files.readAllLines(tempDir.resolve("stat"))) {
            if (line.startsWith("btime ")) {
                bootTime = Long.parseLong(line.substring(6).trim());
            }
        }
        assertEquals(1700000000L, bootTime);

        // Cleanup
        Files.delete(tempDir.resolve("stat"));
        Files.delete(tempDir);
    }

    @Test
    void parseThreadCount_fromStatusFile() throws IOException {
        Path tempDir = Files.createTempDirectory("test");
        String status = "Name:\tmyprocess\n"
                + "Umask:\t0022\n"
                + "State:\tS (sleeping)\n"
                + "Tgid:\t1234\n"
                + "Ngid:\t0\n"
                + "Pid:\t1234\n"
                + "PPid:\t1\n"
                + "Threads:\t8\n";
        Files.writeString(tempDir.resolve("status"), status);

        int threadCount = 0;
        for (String line : Files.readAllLines(tempDir.resolve("status"))) {
            if (line.startsWith("Threads:")) {
                threadCount = Integer.parseInt(
                        line.substring("Threads:".length()).trim()
                );
            }
        }
        assertEquals(8, threadCount);

        // Cleanup
        Files.delete(tempDir.resolve("status"));
        Files.delete(tempDir);
    }

    @Test
    void processSnapshot_calculatesUptime() {
        long bootTimeSeconds = 1700000000L;
        long startTicks = 50000L;
        long clockTicksPerSecond = 100L;
        long currentTimeSeconds = 1700010000L; // 10000 seconds after epoch

        long processStartSeconds = bootTimeSeconds + startTicks / clockTicksPerSecond;
        long uptimeSeconds = Math.max(0L, currentTimeSeconds - processStartSeconds);

        // 1700000000 + 500 = 1700000500
        // 1700010000 - 1700000500 = 9500
        assertEquals(9500L, uptimeSeconds);
    }

    @Test
    void processSnapshot_residentMemoryInBytes() {
        long residentPages = 256L;
        long pageSizeBytes = 4096L;
        long residentBytes = residentPages * pageSizeBytes;
        assertEquals(1048576L, residentBytes); // 1 MB
    }
}