package unit;

import support.Moad0009Algorithm;
import support.Moad0009Algorithm.Event;
import support.Moad0009Algorithm.Result;

import java.util.List;

/**
 * Unit tests for MOAD-0009: A Metered Heart.
 *
 * Proves from first principles:
 *   1. Defective scheduler fires on every timer tick (N firings for N ticks)
 *      even when only M events occur — N - M firings are wasted.
 *   2. Fixed event-driven handler fires exactly once per event (M firings for M events).
 *   3. Both correctly process the same set of events (same events handled).
 *   4. Defective wastes fire count grows with poll interval; fixed stays constant.
 *   5. Zero-event scenario: defective fires N times on empty queue; fixed fires 0.
 *
 * No build tool required. Compile and run:
 *
 *   cd tests
 *   java -m jdk.compiler/com.sun.tools.javac.Main -cp . \
 *        support/Moad0009Algorithm.java unit/Moad0009UnitTest.java
 *   java -cp . unit.Moad0009UnitTest
 */
public class Moad0009UnitTest {

    private static int passed = 0;
    private static int failed = 0;

    public static void main(String[] args) {
        System.out.println("=== Moad0009UnitTest (A Metered Heart) ===\n");

        System.out.println("-- Correctness: both process the same events --");
        testBothProcessSameEvents();
        testBothHandleNoEvents();

        System.out.println("\n-- Defect: timer fires N times regardless of M events --");
        testDefectiveFiresEveryTick();
        testDefectiveWastedFiresN100M3();
        testDefectiveZeroEventsStillFiresN();

        System.out.println("\n-- Fix: fires exactly once per event --");
        testFixedFiresExactlyMTimes();
        testFixedZeroEventsZeroFirings();
        testFixedFireCountEqualsEventCount();

        System.out.println("\n-- Comparison: defective wastes grow with poll count; fixed stays M --");
        testWastedFiresGrowWithPollCount();

        System.out.printf("\n%d passed, %d failed%n", passed, failed);
        if (failed > 0) System.exit(1);
    }

    // ── Correctness ───────────────────────────────────────────────────────────

    static void testBothProcessSameEvents() {
        List<Event> events = Moad0009Algorithm.buildEvents(3, 10);
        Result def = Moad0009Algorithm.runDefectiveScheduler(20, events);
        Result fix = Moad0009Algorithm.runFixedEventDriven(events);

        assertEqual("correctness: both process same event count", def.eventsProcessed, fix.eventsProcessed);
        assertEqual("correctness: both process all 3 events",     3, def.eventsProcessed);
    }

    static void testBothHandleNoEvents() {
        List<Event> events = List.of();
        Result def = Moad0009Algorithm.runDefectiveScheduler(10, events);
        Result fix = Moad0009Algorithm.runFixedEventDriven(events);

        assertEqual("correctness: both process 0 events from empty list", 0, def.eventsProcessed);
        assertEqual("correctness: fixed: 0 events processed",             0, fix.eventsProcessed);
    }

    // ── Defect ────────────────────────────────────────────────────────────────

    static void testDefectiveFiresEveryTick() {
        int ticks = 50;
        List<Event> events = Moad0009Algorithm.buildEvents(2, ticks);
        Result result = Moad0009Algorithm.runDefectiveScheduler(ticks, events);
        // DEFECT: fires every tick regardless of events
        assertEqual("defective: fires exactly N=" + ticks + " times", ticks, result.firings);
    }

    static void testDefectiveWastedFiresN100M3() {
        int ticks = 100;
        int eventCount = 3;
        List<Event> events = Moad0009Algorithm.buildEvents(eventCount, ticks);
        Result result = Moad0009Algorithm.runDefectiveScheduler(ticks, events);

        // DEFECT: 100 firings for 3 events = 97 wasted firings (97% waste)
        int wasted = result.firings - result.eventsProcessed;
        assertEqual("defective: 97 wasted firings (100 ticks, 3 events)", 97, wasted);
        assertTrue("defective: waste ratio > 95%",
            (double) wasted / result.firings > 0.95,
            "wasted=" + wasted + " total=" + result.firings);
    }

    static void testDefectiveZeroEventsStillFiresN() {
        int ticks = 60;
        List<Event> events = List.of();
        Result result = Moad0009Algorithm.runDefectiveScheduler(ticks, events);
        // DEFECT: no events exist, but timer still fires 60 times — pure waste
        assertEqual("defective: 0 events, fires N=" + ticks + " times (100% waste)", ticks, result.firings);
        assertEqual("defective: 0 events processed",                                  0, result.eventsProcessed);
    }

    // ── Fix ───────────────────────────────────────────────────────────────────

    static void testFixedFiresExactlyMTimes() {
        List<Event> events = Moad0009Algorithm.buildEvents(5, 100);
        Result result = Moad0009Algorithm.runFixedEventDriven(events);
        assertEqual("fixed: fires exactly M=5 times (one per event)", 5, result.firings);
    }

    static void testFixedZeroEventsZeroFirings() {
        List<Event> events = List.of();
        Result result = Moad0009Algorithm.runFixedEventDriven(events);
        assertEqual("fixed: 0 events → 0 firings (no wasted work)", 0, result.firings);
    }

    static void testFixedFireCountEqualsEventCount() {
        for (int m : new int[]{1, 7, 23, 100}) {
            List<Event> events = Moad0009Algorithm.buildEvents(m, 200);
            Result result = Moad0009Algorithm.runFixedEventDriven(events);
            assertEqual("fixed: M=" + m + " events → exactly M=" + m + " firings",
                m, result.firings);
        }
    }

    // ── Comparison ────────────────────────────────────────────────────────────

    static void testWastedFiresGrowWithPollCount() {
        List<Event> events = Moad0009Algorithm.buildEvents(2, 200);

        // More ticks = more waste in defective; fixed stays at M=2
        Result def50  = Moad0009Algorithm.runDefectiveScheduler(50,  events);
        Result def200 = Moad0009Algorithm.runDefectiveScheduler(200, events);
        Result fix    = Moad0009Algorithm.runFixedEventDriven(events);

        assertTrue("defective: 50 ticks → 50 firings",  def50.firings  == 50,  "got " + def50.firings);
        assertTrue("defective: 200 ticks → 200 firings", def200.firings == 200, "got " + def200.firings);
        assertTrue("fixed: always 2 firings regardless of tick count", fix.firings == 2, "got " + fix.firings);

        // Wasted = defective.firings - events processed
        int waste50  = def50.firings  - def50.eventsProcessed;
        int waste200 = def200.firings - def200.eventsProcessed;
        assertTrue("defective: waste grows with tick count (200 > 50)",
            waste200 > waste50, "waste50=" + waste50 + " waste200=" + waste200);
    }

    // ── Helpers ───────────────────────────────────────────────────────────────

    static void assertEqual(String label, int expected, int actual) {
        if (expected == actual) {
            System.out.printf("  PASS: %s%n", label);
            passed++;
        } else {
            System.out.printf("  FAIL: %s — expected %d, got %d%n", label, expected, actual);
            failed++;
        }
    }

    static void assertTrue(String label, boolean condition, String detail) {
        if (condition) {
            System.out.printf("  PASS: %s%n", label);
            passed++;
        } else {
            System.out.printf("  FAIL: %s — %s%n", label, detail);
            failed++;
        }
    }
}