#include <atomic>
#include <barrier>
#include <condition_variable>
#include <filesystem>
#include <mutex>
#include <random>
#include <thread>
#include "common/test_data_generator.h"
#include <catch2/catch_test_macros.hpp>
#include <yams/api/content_store.h>
#include <yams/metadata/database.h>
#include <yams/metadata/metadata_repository.h>

using namespace yams;
using namespace yams::api;
using namespace yams::metadata;
using namespace yams::test;

struct ConcurrencyTest {
    ConcurrencyTest() {
        testDir_ = std::filesystem::temp_directory_path() / "yams_concurrency_test";
        std::filesystem::create_directories(testDir_);

        initializeYAMS();
        generator_ = std::make_unique<TestDataGenerator>();
    }

    ~ConcurrencyTest() {
        contentStore_.reset();
        metadataRepo_.reset();
        database_.reset();
        std::filesystem::remove_all(testDir_);
    }

    void initializeYAMS() {
        auto dbPath = testDir_ / "yams.db";
        database_ = std::make_shared<Database>(dbPath.string());
        database_->initialize();
        metadataRepo_ = std::make_shared<MetadataRepository>(database_);
        contentStore_ = std::make_unique<ContentStore>(testDir_.string());
    }

    std::filesystem::path testDir_;
    std::shared_ptr<Database> database_;
    std::shared_ptr<MetadataRepository> metadataRepo_;
    std::unique_ptr<ContentStore> contentStore_;
    std::unique_ptr<TestDataGenerator> generator_;
};

TEST_CASE_METHOD(ConcurrencyTest, "ConcurrentDocumentAddition", "[integration][concurrencytest]") {
    const size_t numThreads = 8;
    const size_t docsPerThread = 10;

    std::atomic<size_t> successCount{0};
    std::atomic<size_t> failCount{0};
    std::vector<std::string> allHashes;
    std::mutex hashMutex;

    std::vector<std::thread> threads;

    for (size_t t = 0; t < numThreads; ++t) {
        threads.emplace_back([&, t]() {
            TestDataGenerator localGen(t); // Thread-local generator with unique seed

            for (size_t i = 0; i < docsPerThread; ++i) {
                auto content = localGen.generateTextDocument(1024 + i * 100);
                auto file = testDir_ /
                            ("thread_" + std::to_string(t) + "_doc_" + std::to_string(i) + ".txt");

                std::ofstream outFile(file);
                outFile << content;
                outFile.close();

                auto result =
                    contentStore_->addFile(file, {"concurrent", "thread_" + std::to_string(t)});

                if (result.has_value()) {
                    successCount++;
                    std::lock_guard<std::mutex> lock(hashMutex);
                    allHashes.push_back(result->contentHash);
                } else {
                    failCount++;
                }
            }
        });
    }

    for (auto& thread : threads) {
        thread.join();
    }

    // Verify results
    INFO("Some additions failed");
    CHECK(successCount.load() == numThreads * docsPerThread);
    INFO("There were failures");
    CHECK(failCount.load() == 0);
    INFO("Hash count mismatch");
    CHECK(allHashes.size() == numThreads * docsPerThread);

    // Verify all documents are retrievable
    for (const auto& hash : allHashes) {
        auto content = contentStore_->getContent(hash);
        INFO("Failed to retrieve document: " << hash);
        CHECK(content.has_value());
    }
}

TEST_CASE_METHOD(ConcurrencyTest, "ConcurrentSearchOperations", "[integration][concurrencytest]") {
    // First, add some documents
    const size_t numDocs = 100;
    std::vector<std::string> searchTerms = {"alpha", "beta", "gamma", "delta", "epsilon"};

    for (size_t i = 0; i < numDocs; ++i) {
        auto content = generator_->generateTextDocument(512);
        content += " " + searchTerms[i % searchTerms.size()];

        auto file = testDir_ / ("search_doc_" + std::to_string(i) + ".txt");
        std::ofstream(file) << content;

        contentStore_->addFile(file, {"searchable"});
    }

    // Concurrent searches
    const size_t numSearchThreads = 10;
    const size_t searchesPerThread = 20;
    std::atomic<size_t> totalResults{0};
    std::atomic<size_t> searchFailures{0};

    std::vector<std::thread> searchThreads;

    for (size_t t = 0; t < numSearchThreads; ++t) {
        searchThreads.emplace_back([&, t]() {
            std::mt19937 rng(t);
            std::uniform_int_distribution<size_t> dist(0, searchTerms.size() - 1);

            for (size_t i = 0; i < searchesPerThread; ++i) {
                const auto& term = searchTerms[dist(rng)];

                auto results = contentStore_->search(term);
                if (results.has_value()) {
                    totalResults++;
                } else {
                    searchFailures++;
                }

                // Also test with options
                search::SearchOptions options;
                options.tags = {"searchable"};
                options.limit = 10;

                auto taggedResults = contentStore_->searchWithOptions(term, options);
                totalResults += taggedResults.size();
            }
        });
    }

    for (auto& thread : searchThreads) {
        thread.join();
    }

    INFO("No search results found");
    CHECK(totalResults.load() > 0);
    INFO("Some searches failed");
    CHECK(searchFailures.load() == 0);
}

TEST_CASE_METHOD(ConcurrencyTest, "ConcurrentMetadataUpdates", "[integration][concurrencytest]") {
    // Add documents first
    const size_t numDocs = 50;
    std::vector<std::string> docIds;

    for (size_t i = 0; i < numDocs; ++i) {
        auto content = generator_->generateTextDocument(512);
        auto file = testDir_ / ("metadata_doc_" + std::to_string(i) + ".txt");
        std::ofstream(file) << content;

        auto result = contentStore_->addFile(file);
        REQUIRE(result.has_value());

        auto docResult = metadataRepo_->getDocumentByHash(result->contentHash);
        REQUIRE(docResult.has_value() && docResult->has_value());
        docIds.push_back(docResult->value()->id);
    }

    // Concurrent metadata updates
    const size_t numUpdateThreads = 8;
    std::atomic<size_t> updateSuccess{0};
    std::atomic<size_t> updateFailure{0};

    std::vector<std::thread> updateThreads;

    for (size_t t = 0; t < numUpdateThreads; ++t) {
        updateThreads.emplace_back([&, t]() {
            std::mt19937 rng(t);
            std::uniform_int_distribution<size_t> docDist(0, docIds.size() - 1);

            for (size_t i = 0; i < 20; ++i) {
                size_t docIdx = docDist(rng);
                const auto& docId = docIds[docIdx];

                std::string key = "thread_" + std::to_string(t) + "_field_" + std::to_string(i);
                std::string value = "value_" + std::to_string(i);

                auto result = metadataRepo_->setMetadata(docId, key, MetadataValue(value));

                if (result.isOk()) {
                    updateSuccess++;
                } else {
                    updateFailure++;
                }
            }
        });
    }

    for (auto& thread : updateThreads) {
        thread.join();
    }

    INFO("No successful updates");
    CHECK(updateSuccess.load() > 0);
    INFO("Some updates failed");
    CHECK(updateFailure.load() == 0);

    // Verify metadata persistence
    for (const auto& docId : docIds) {
        auto allMetadata = metadataRepo_->getAllMetadata(docId);
        INFO("Failed to get metadata for " << docId);
        CHECK(allMetadata.has_value());
    }
}

TEST_CASE_METHOD(ConcurrencyTest, "RaceConditionDetection", "[integration][concurrencytest]") {
    // Test for race conditions in critical sections

    const size_t numThreads = 10;
    std::atomic<int> sharedCounter{0};
    std::vector<int> threadResults(numThreads, 0);

    // Add a single document that all threads will try to update
    auto content = generator_->generateTextDocument(1024);
    auto file = testDir_ / "race_test.txt";
    std::ofstream(file) << content;

    auto result = contentStore_->addFile(file);
    REQUIRE(result.has_value());

    auto docResult = metadataRepo_->getDocumentByHash(result->contentHash);
    REQUIRE(docResult.has_value() && docResult->has_value());
    std::string docId = docResult->value()->id;

    // Use a barrier to ensure all threads start simultaneously
    std::barrier sync_point(numThreads);

    std::vector<std::thread> threads;

    for (size_t t = 0; t < numThreads; ++t) {
        threads.emplace_back([&, t]() {
            sync_point.arrive_and_wait();

            // Try to increment a shared counter through metadata
            for (int i = 0; i < 100; ++i) {
                // Read current value
                auto currentMeta = metadataRepo_->getMetadata(docId, "counter");
                int currentValue = 0;
                if (currentMeta.has_value()) {
                    currentValue = static_cast<int>(currentMeta->toDouble());
                }

                // Increment and write back
                currentValue++;
                auto updateResult = metadataRepo_->setMetadata(
                    docId, "counter", MetadataValue(static_cast<double>(currentValue)));

                if (updateResult.isOk()) {
                    threadResults[t]++;
                }

                sharedCounter++;
            }
        });
    }

    for (auto& thread : threads) {
        thread.join();
    }

    // Check final counter value
    auto finalMeta = metadataRepo_->getMetadata(docId, "counter");
    REQUIRE(finalMeta.has_value());
    int finalValue = static_cast<int>(finalMeta->toDouble());

    // Due to race conditions, final value may be less than total operations
    // This is expected and demonstrates the need for proper synchronization
    INFO("Counter exceeded maximum possible value");
    CHECK(finalValue <= numThreads * 100);
    INFO("Counter was not updated at all");
    CHECK(finalValue > 0);

    // Verify shared counter
    INFO("Shared counter mismatch");
    CHECK(sharedCounter.load() == numThreads * 100);
}

TEST_CASE_METHOD(ConcurrencyTest, "DataIntegrityUnderLoad", "[integration][concurrencytest]") {
    // Test data integrity with mixed concurrent operations

    const size_t numOperations = 200;
    std::atomic<size_t> addCount{0};
    std::atomic<size_t> searchCount{0};
    std::atomic<size_t> updateCount{0};
    std::atomic<size_t> getCount{0};

    std::vector<std::string> documentHashes;
    std::mutex hashesMutex;

    // Mixed operation threads
    std::vector<std::thread> threads;

    for (int t = 0; t < 8; ++t) {
        threads.emplace_back([&, t]() {
            std::mt19937 rng(t);
            std::uniform_int_distribution<int> opDist(0, 3);
            TestDataGenerator localGen(t);

            for (size_t i = 0; i < numOperations / 8; ++i) {
                int operation = opDist(rng);

                switch (operation) {
                    case 0: { // Add
                        auto content = localGen.generateTextDocument(512);
                        auto file = testDir_ / ("integrity_" + std::to_string(t) + "_" +
                                                std::to_string(i) + ".txt");
                        std::ofstream(file) << content;

                        auto result = contentStore_->addFile(file);
                        if (result.has_value()) {
                            addCount++;
                            std::lock_guard<std::mutex> lock(hashesMutex);
                            documentHashes.push_back(result->contentHash);
                        }
                        break;
                    }

                    case 1: { // Search
                        auto results = contentStore_->search("test");
                        searchCount++;
                        break;
                    }

                    case 2: { // Update metadata
                        std::lock_guard<std::mutex> lock(hashesMutex);
                        if (!documentHashes.empty()) {
                            std::uniform_int_distribution<size_t> hashDist(
                                0, documentHashes.size() - 1);
                            const auto& hash = documentHashes[hashDist(rng)];

                            auto docResult = metadataRepo_->getDocumentByHash(hash);
                            if (docResult.has_value() && docResult->has_value()) {
                                auto updateResult = metadataRepo_->setMetadata(
                                    docResult->value()->id, "thread_" + std::to_string(t),
                                    MetadataValue("update_" + std::to_string(i)));
                                if (updateResult.isOk()) {
                                    updateCount++;
                                }
                            }
                        }
                        break;
                    }

                    case 3: { // Get
                        std::lock_guard<std::mutex> lock(hashesMutex);
                        if (!documentHashes.empty()) {
                            std::uniform_int_distribution<size_t> hashDist(
                                0, documentHashes.size() - 1);
                            const auto& hash = documentHashes[hashDist(rng)];

                            auto content = contentStore_->getContent(hash);
                            if (content.has_value()) {
                                getCount++;
                                // Verify content is not corrupted
                                INFO("Empty content retrieved");
                                CHECK(content->size() > 0);
                            }
                        }
                        break;
                    }
                }
            }
        });
    }

    for (auto& thread : threads) {
        thread.join();
    }

    // Verify operation counts
    std::cout << "Operations completed - Add: " << addCount.load()
              << ", Search: " << searchCount.load() << ", Update: " << updateCount.load()
              << ", Get: " << getCount.load() << std::endl;

    INFO("No documents added");
    CHECK(addCount.load() > 0);
    INFO("No searches performed");
    CHECK(searchCount.load() > 0);
    INFO("No updates performed");
    CHECK(updateCount.load() > 0);
    INFO("No gets performed");
    CHECK(getCount.load() > 0);

    // Final integrity check - all documents should be retrievable
    for (const auto& hash : documentHashes) {
        auto content = contentStore_->getContent(hash);
        INFO("Document lost: " << hash);
        CHECK(content.has_value());
        if (content.has_value()) {
            INFO("Document corrupted: " << hash);
            CHECK(content->size() > 0);
        }
    }
}

TEST_CASE_METHOD(ConcurrencyTest, "DeadlockPrevention", "[integration][concurrencytest]") {
    // Test that operations don't deadlock

    const size_t numThreads = 4;
    std::atomic<bool> deadlockDetected{false};

    // Add some initial documents
    std::vector<std::string> hashes;
    for (int i = 0; i < 10; ++i) {
        auto content = generator_->generateTextDocument(512);
        auto file = testDir_ / ("deadlock_test_" + std::to_string(i) + ".txt");
        std::ofstream(file) << content;

        auto result = contentStore_->addFile(file);
        REQUIRE(result.has_value());
        hashes.push_back(result->contentHash);
    }

    // Threads that perform operations in different orders
    std::vector<std::thread> threads;

    // Thread pattern 1: Add -> Search -> Update
    threads.emplace_back([&]() {
        for (int i = 0; i < 50; ++i) {
            auto content = generator_->generateTextDocument(256);
            auto file = testDir_ / ("pattern1_" + std::to_string(i) + ".txt");
            std::ofstream(file) << content;

            contentStore_->addFile(file);
            contentStore_->search("test");

            if (!hashes.empty()) {
                auto docResult = metadataRepo_->getDocumentByHash(hashes[0]);
                if (docResult.has_value() && docResult->has_value()) {
                    metadataRepo_->setMetadata(docResult->value()->id, "pattern1",
                                               MetadataValue(i));
                }
            }
        }
    });

    // Thread pattern 2: Update -> Add -> Search
    threads.emplace_back([&]() {
        for (int i = 0; i < 50; ++i) {
            if (!hashes.empty()) {
                auto docResult = metadataRepo_->getDocumentByHash(hashes[0]);
                if (docResult.has_value() && docResult->has_value()) {
                    metadataRepo_->setMetadata(docResult->value()->id, "pattern2",
                                               MetadataValue(i));
                }
            }

            auto content = generator_->generateTextDocument(256);
            auto file = testDir_ / ("pattern2_" + std::to_string(i) + ".txt");
            std::ofstream(file) << content;

            contentStore_->addFile(file);
            contentStore_->search("test");
        }
    });

    // Thread pattern 3: Search -> Update -> Add
    threads.emplace_back([&]() {
        for (int i = 0; i < 50; ++i) {
            contentStore_->search("test");

            if (!hashes.empty()) {
                auto docResult = metadataRepo_->getDocumentByHash(hashes[0]);
                if (docResult.has_value() && docResult->has_value()) {
                    metadataRepo_->setMetadata(docResult->value()->id, "pattern3",
                                               MetadataValue(i));
                }
            }

            auto content = generator_->generateTextDocument(256);
            auto file = testDir_ / ("pattern3_" + std::to_string(i) + ".txt");
            std::ofstream(file) << content;

            contentStore_->addFile(file);
        }
    });

    // Deadlock detection thread
    threads.emplace_back([&]() {
        auto startTime = std::chrono::steady_clock::now();
        const auto timeout = std::chrono::seconds(30);

        while (true) {
            std::this_thread::sleep_for(std::chrono::milliseconds(100));

            auto now = std::chrono::steady_clock::now();
            if (now - startTime > timeout) {
                deadlockDetected = true;
                break;
            }

            // Check if other threads are done
            bool allDone = true;
            for (size_t i = 0; i < threads.size() - 1; ++i) {
                if (threads[i].joinable()) {
                    allDone = false;
                    break;
                }
            }

            if (allDone)
                break;
        }
    });

    // Join all threads
    for (auto& thread : threads) {
        if (thread.joinable()) {
            thread.join();
        }
    }

    INFO("Potential deadlock detected (timeout)");
    CHECK_FALSE(deadlockDetected.load());
}