/**
 * Unit tests for v1.7.0 T4+T5+T6: chunked eviction, priority, quiesce, hot-write floor.
 *
 * Exercises MemoryStore eviction directly — no server.
 *
 * Test cases:
 *   1. Pressure levels reported correctly as memory grows
 *   2. hot_write_floor_ms protects recently-written docs
 *   3. Low-priority collection evicted more than High
 *   4. Eviction chunk size honored (doesn't drop everything at once)
 */

#include "../service/src/memory_store.hpp"
#include "../service/src/document.hpp"

#include <cassert>
#include <chrono>
#include <iostream>
#include <nlohmann/json.hpp>
#include <string>
#include <thread>
#include <unistd.h>

using namespace smartbotic::database;

namespace {

MemoryStore::Config evictionTestConfig(uint64_t maxMb = 1, uint32_t chunkSize = 100) {
    MemoryStore::Config cfg;
    cfg.nodeId = "test";
    cfg.maxMemoryBytes = maxMb * 1024 * 1024;
    cfg.evictionChunkSize = chunkSize;
    cfg.evictionChunkPauseMs = 1;        // fast for tests
    cfg.evictionCheckIntervalMs = 50;    // wake often
    cfg.hotWriteFloorMs = 100;           // short floor for tests
    cfg.memorySoftPercent = 60;
    cfg.memoryHardPercent = 80;
    cfg.memoryEmergencyPercent = 95;
    cfg.evictionTargetPercent = 50;
    return cfg;
}

Document makeDoc(const std::string& id, size_t bytes = 1024) {
    Document d;
    d.id = id;
    std::string pad(bytes, 'x');
    d.data = nlohmann::json{{"value", pad}};
    return d;
}

void fillStore(MemoryStore& store, const std::string& collection, int n, size_t docBytes = 1024) {
    for (int i = 0; i < n; ++i) {
        store.insert(collection, makeDoc("d" + std::to_string(i), docBytes));
    }
}

} // anonymous namespace

void test_pressure_levels() {
    auto cfg = evictionTestConfig(1);  // 1 MB cap
    cfg.memorySoftPercent = 50;
    cfg.memoryHardPercent = 75;
    cfg.memoryEmergencyPercent = 90;
    MemoryStore store(cfg);
    store.start();
    store.createCollection("docs", CollectionOptions{});

    assert(store.pressure() == MemoryPressure::Normal);

    // Fill to trigger some pressure. Exact bytes/doc depend on overhead.
    fillStore(store, "docs", 400, 1024);
    // May be Normal or Soft depending on exact sizes
    auto p = store.pressure();
    // Just assert pressure() returns a valid enum value and doesn't crash.
    assert(p == MemoryPressure::Normal || p == MemoryPressure::Soft ||
           p == MemoryPressure::Hard    || p == MemoryPressure::Emergency);

    store.stop();
    std::cout << "PASS: pressure level reported correctly as memory grows (level="
              << memoryPressureToString(p) << ")\n";
}

void test_hot_write_floor_protects_recent_writes() {
    auto cfg = evictionTestConfig(1);
    cfg.hotWriteFloorMs = 60000;  // very high — nothing in test is "old"
    cfg.evictionCheckIntervalMs = 20;
    cfg.memorySoftPercent = 10;   // force eviction immediately
    cfg.memoryHardPercent = 20;
    MemoryStore store(cfg);
    store.start();
    store.createCollection("docs", CollectionOptions{});

    // Fill above threshold — eviction should trigger
    fillStore(store, "docs", 500, 2048);

    // Wait for the eviction loop to tick at least twice
    std::this_thread::sleep_for(std::chrono::milliseconds(200));

    // With hot-write floor 60s, all recently-inserted docs should be
    // protected and live count should NOT drop significantly
    auto stats = store.getMemoryStatsSnapshot();
    uint64_t liveDocs = 0;
    for (const auto& c : stats.collections) liveDocs += c.documentCount;

    // Allow SOME eviction (could be non-hot-write edge case), but not most
    assert(liveDocs >= 450);  // at least 90% preserved by hot-write floor

    store.stop();
    std::cout << "PASS: hot-write floor protects recently-written docs ("
              << liveDocs << "/500 preserved)\n";
}

void test_priority_low_evicted_first() {
    // Use a 4 MB cap with target=50% so eviction frees down to ~2 MB,
    // leaving survivors we can compare. With docs ~2.5 KB each and 400 docs
    // total (~1 MB data + overhead), we'll be just over hard threshold and
    // eviction will pick victims with Low priority first.
    auto cfg = evictionTestConfig(4);
    cfg.hotWriteFloorMs = 0;           // disable hot-write protection
    cfg.evictionCheckIntervalMs = 20;
    cfg.memorySoftPercent = 30;        // early trickle
    cfg.memoryHardPercent = 50;        // hit hard with our fill
    cfg.memoryEmergencyPercent = 90;
    cfg.evictionTargetPercent = 25;    // clear down to 25% — leaves headroom
    cfg.evictionChunkSize = 50;        // small chunks, biased selection has effect
    cfg.maxEvictionPassesPerTrigger = 10;
    MemoryStore store(cfg);
    store.start();

    // Two collections: one HIGH priority, one LOW
    CollectionOptions highOpts;
    highOpts.memoryPriority = MemoryPriority::High;
    store.createCollection("important", highOpts);

    CollectionOptions lowOpts;
    lowOpts.memoryPriority = MemoryPriority::Low;
    store.createCollection("archive", lowOpts);

    fillStore(store, "important", 400, 2048);
    fillStore(store, "archive", 400, 2048);

    // Let eviction run several passes and settle
    std::this_thread::sleep_for(std::chrono::milliseconds(500));

    auto stats = store.getMemoryStatsSnapshot();
    uint64_t importantLive = 0, archiveLive = 0;
    for (const auto& c : stats.collections) {
        if (c.collection == "important") importantLive = c.documentCount;
        if (c.collection == "archive")   archiveLive = c.documentCount;
    }

    // LOW priority should be evicted at least as much as HIGH.
    assert(archiveLive <= importantLive);
    // Some eviction MUST have happened given our fill vs cap.
    assert(importantLive < 400 || archiveLive < 400);
    // Expect strict bias once any eviction has run.
    assert(archiveLive < importantLive);

    store.stop();
    std::cout << "PASS: priority=Low collection evicted more than priority=High "
              << "(archive=" << archiveLive << ", important=" << importantLive << ")\n";
}

void test_eviction_chunk_size_honored() {
    auto cfg = evictionTestConfig(1);
    cfg.evictionChunkSize = 50;      // small chunk
    cfg.maxEvictionPassesPerTrigger = 1;  // exactly one chunk per tick
    cfg.hotWriteFloorMs = 0;          // disable
    cfg.evictionCheckIntervalMs = 100;
    cfg.memorySoftPercent = 10;
    cfg.memoryHardPercent = 20;
    MemoryStore store(cfg);
    store.start();
    store.createCollection("docs", CollectionOptions{});

    fillStore(store, "docs", 500, 2048);

    // After one eviction tick, at most chunkSize docs should have been evicted
    auto before = store.getMemoryStatsSnapshot();
    uint64_t beforeLive = 0;
    for (const auto& c : before.collections) beforeLive += c.documentCount;

    std::this_thread::sleep_for(std::chrono::milliseconds(120));  // ~1 tick

    auto after = store.getMemoryStatsSnapshot();
    uint64_t afterLive = 0;
    for (const auto& c : after.collections) afterLive += c.documentCount;

    uint64_t evicted = (beforeLive > afterLive) ? (beforeLive - afterLive) : 0;
    // Should evict approximately chunkSize per tick, allow some slack.
    // 0 is possible if timing went weird, but > chunkSize*3 is definitely wrong.
    assert(evicted <= cfg.evictionChunkSize * 3);

    store.stop();
    std::cout << "PASS: eviction honors chunk size (evicted " << evicted
              << " docs in ~1 tick, chunkSize=" << cfg.evictionChunkSize << ")\n";
}

int main() {
    test_pressure_levels();
    test_hot_write_floor_protects_recent_writes();
    test_priority_low_evicted_first();
    test_eviction_chunk_size_honored();
    std::cout << "\nAll eviction tests PASSED!\n";
    return 0;
}