#include "pipeline_cache.hpp"

#include "clear.hpp"
#include "../gx/pipeline.hpp"
#include "../sqlite_utils.hpp"
#include "../webgpu/gpu.hpp"

#include <algorithm>
#include <atomic>
#include <condition_variable>
#include <deque>
#include <filesystem>
#include <mutex>
#include <thread>

#include <absl/container/flat_hash_map.h>
#include <absl/container/flat_hash_set.h>
#include <fmt/format.h>
#include <tracy/Tracy.hpp>

namespace aurora::gfx {
static Module Log("aurora::gfx::pipeline_cache");

constexpr int PipelineCacheSchema = 1;

struct CachedPipeline {
  wgpu::RenderPipeline pipeline;
  uint32_t firstFrameUsed = UINT32_MAX;
};

struct PendingPipeline {
  PipelineRef hash;
  uint32_t firstFrameUsed = UINT32_MAX;
  NewPipelineCallback create;
};

struct PipelineCacheWrite {
  ShaderType type;
  PipelineRef hash;
  uint32_t configVersion;
  ByteBuffer config;
  uint32_t firstFrameUsed = UINT32_MAX;
};

static std::mutex g_pipelineMutex;
static bool g_hasPipelineThread = false;
static bool g_pipelineFrameActive = false;
static size_t g_pipelinesPerFrame = 0;
// For synchronous pipeline fallback (OpenGL)
#ifdef NDEBUG
constexpr size_t BuildPipelinesPerFrame = 5;
#else
constexpr size_t BuildPipelinesPerFrame = 1;
#endif
static std::thread g_pipelineThread;
static std::atomic_bool g_pipelineThreadEnd = false;
static std::condition_variable g_pipelineCv;
static absl::flat_hash_map<PipelineRef, CachedPipeline> g_pipelines;
static std::deque<PendingPipeline> g_priorityPipelines;
static std::deque<PendingPipeline> g_backgroundPipelines;
static absl::flat_hash_set<PipelineRef> g_pendingPipelines;

static sqlite3* g_pipelineCacheDb = nullptr;
static sqlite3_stmt* g_pipelineCacheLoadStmt = nullptr;
static sqlite3_stmt* g_pipelineCacheUpsertStmt = nullptr;
static bool g_pipelineCacheBroken = false;
static std::thread g_pipelineCacheWriterThread;
static std::condition_variable g_pipelineCacheWriterCv;
static std::mutex g_pipelineCacheWriterMutex;
static std::deque<PipelineCacheWrite> g_pipelineCacheWriteQueue;
static bool g_pipelineCacheWriterStop = false;

static std::atomic_ref queuedPipelines{g_stats.queuedPipelines};
static std::atomic_ref createdPipelines{g_stats.createdPipelines};

template <typename PipelineConfig>
static PipelineCacheWrite make_pipeline_cache_write(ShaderType type, PipelineRef hash, const PipelineConfig& config,
                                                    uint32_t firstFrameUsed) {
  static_assert(std::has_unique_object_representations_v<PipelineConfig>);

  PipelineCacheWrite write{
      .type = type,
      .hash = hash,
      .configVersion = config.version,
      .config = ByteBuffer(sizeof(config)),
      .firstFrameUsed = firstFrameUsed,
  };
  std::memcpy(write.config.data(), &config, sizeof(config));
  return write;
}

static void enqueue_pipeline_cache_write(PipelineCacheWrite write) {
  if (g_pipelineCacheBroken || g_pipelineCacheDb == nullptr) {
    return;
  }

  {
    std::lock_guard lock{g_pipelineCacheWriterMutex};
    g_pipelineCacheWriteQueue.emplace_back(std::move(write));
  }
  g_pipelineCacheWriterCv.notify_one();
}

template <typename Queue>
static auto find_pending_pipeline(Queue& queue, PipelineRef hash) {
  return std::find_if(queue.begin(), queue.end(), [=](const PendingPipeline& pending) { return pending.hash == hash; });
}

static PendingPipeline* touch_pending_pipeline(PipelineRef hash, bool prioritize) {
  auto priorityIt = find_pending_pipeline(g_priorityPipelines, hash);
  if (priorityIt != g_priorityPipelines.end()) {
    return &*priorityIt;
  }

  auto backgroundIt = find_pending_pipeline(g_backgroundPipelines, hash);
  if (backgroundIt == g_backgroundPipelines.end()) {
    return nullptr;
  }

  if (!prioritize) {
    return &*backgroundIt;
  }

  g_priorityPipelines.emplace_back(std::move(*backgroundIt));
  g_backgroundPipelines.erase(backgroundIt);
  return &g_priorityPipelines.back();
}

template <typename PipelineConfig>
static PipelineRef find_pipeline_impl(ShaderType type, const PipelineConfig& config, NewPipelineCallback&& cb,
                                      bool persist, std::optional<uint32_t> firstFrameUsedOverride) {
  const PipelineRef hash = xxh3_hash(config, static_cast<HashType>(type));
  const uint32_t firstFrameUsed = firstFrameUsedOverride.value_or(current_frame());
  bool notifyWorker = false;
  std::optional<PipelineCacheWrite> cacheWrite;
  {
    std::scoped_lock guard{g_pipelineMutex};
    auto pipelineIt = g_pipelines.find(hash);
    if (pipelineIt != g_pipelines.end()) {
      if (persist && firstFrameUsed < pipelineIt->second.firstFrameUsed) {
        pipelineIt->second.firstFrameUsed = firstFrameUsed;
        cacheWrite = make_pipeline_cache_write(type, hash, config, firstFrameUsed);
      }
    } else if (g_pendingPipelines.contains(hash)) {
      auto* pending = touch_pending_pipeline(hash, g_pipelineFrameActive);
      if (pending != nullptr && firstFrameUsed < pending->firstFrameUsed) {
        pending->firstFrameUsed = firstFrameUsed;
        if (persist) {
          cacheWrite = make_pipeline_cache_write(type, hash, config, firstFrameUsed);
        }
      }
    } else {
      if (!g_hasPipelineThread && g_pipelinesPerFrame < BuildPipelinesPerFrame) {
        g_pipelines.try_emplace(hash, CachedPipeline{
                                          .pipeline = cb(),
                                          .firstFrameUsed = firstFrameUsed,
                                      });
        if (persist) {
          cacheWrite = make_pipeline_cache_write(type, hash, config, firstFrameUsed);
        }
        ++g_pipelinesPerFrame;
        ++createdPipelines;
      } else {
        auto& targetQueue = g_pipelineFrameActive ? g_priorityPipelines : g_backgroundPipelines;
        targetQueue.emplace_back(PendingPipeline{
            .hash = hash,
            .firstFrameUsed = firstFrameUsed,
            .create = std::move(cb),
        });
        g_pendingPipelines.insert(hash);
        if (persist) {
          cacheWrite = make_pipeline_cache_write(type, hash, config, firstFrameUsed);
        }
        notifyWorker = true;
      }
    }
  }

  if (cacheWrite) {
    enqueue_pipeline_cache_write(std::move(*cacheWrite));
  }

  if (notifyWorker) {
    g_pipelineCv.notify_one();
    ++queuedPipelines;
  }

  return hash;
}

static void pipeline_cache_abort() {
  g_pipelineCacheBroken = true;
  if (g_pipelineCacheLoadStmt != nullptr) {
    sqlite3_finalize(g_pipelineCacheLoadStmt);
    g_pipelineCacheLoadStmt = nullptr;
  }
  if (g_pipelineCacheUpsertStmt != nullptr) {
    sqlite3_finalize(g_pipelineCacheUpsertStmt);
    g_pipelineCacheUpsertStmt = nullptr;
  }
  if (g_pipelineCacheDb != nullptr) {
    sqlite3_close(g_pipelineCacheDb);
    g_pipelineCacheDb = nullptr;
  }
}

static bool prepare_pipeline_cache_db() {
  if (g_pipelineCacheBroken) {
    return false;
  }
  if (g_pipelineCacheDb != nullptr) {
    return true;
  }

  const auto path = (std::filesystem::path{g_config.configPath} / "pipeline_cache.db").string();
  auto ret = sqlite3_open(path.c_str(), &g_pipelineCacheDb);
  if (ret != SQLITE_OK) {
    Log.error("Failed to open pipeline cache database: {}", sqlite3_errmsg(g_pipelineCacheDb));
    pipeline_cache_abort();
    return false;
  }

  ret = sqlite::exec(g_pipelineCacheDb, "PRAGMA journal_mode=WAL; PRAGMA synchronous=NORMAL;");
  if (ret != SQLITE_OK) {
    Log.error("Failed to set pipeline cache pragmas: {}", sqlite3_errmsg(g_pipelineCacheDb));
    pipeline_cache_abort();
    return false;
  }

  bool schemaFailed = false;
  {
    sqlite::Transaction tx(g_pipelineCacheDb, Log, true);
    if (!tx) {
      Log.error("Failed to begin pipeline cache schema transaction");
      schemaFailed = true;
    } else {
      ret = sqlite::exec(g_pipelineCacheDb, "CREATE TABLE IF NOT EXISTS aurora_schema(value INTEGER);");
      if (ret != SQLITE_OK) {
        Log.error("Failed to create pipeline cache schema table: {}", sqlite3_errmsg(g_pipelineCacheDb));
        schemaFailed = true;
      }
    }

    bool schemaMatch = false;
    if (!schemaFailed) {
      const auto schemaQuery = fmt::format("SELECT 1 FROM aurora_schema WHERE value = {}", PipelineCacheSchema);
      ret = sqlite::exec(g_pipelineCacheDb, schemaQuery.c_str(),
                         [&schemaMatch](int, char**, char**) { schemaMatch = true; });
      if (ret != SQLITE_OK) {
        Log.error("Failed to read pipeline cache schema version: {}", sqlite3_errmsg(g_pipelineCacheDb));
        schemaFailed = true;
      }
    }

    if (!schemaFailed && !schemaMatch) {
      const auto schemaSql = fmt::format(
          R"(DROP TABLE IF EXISTS pipeline_cache;
CREATE TABLE pipeline_cache (
  type INTEGER NOT NULL,
  hash INTEGER NOT NULL,
  config_version INTEGER NOT NULL,
  config_size INTEGER NOT NULL,
  config BLOB NOT NULL,
  first_frame_used INTEGER NOT NULL,
  PRIMARY KEY (type, hash)
);
CREATE INDEX pipeline_cache_load_order_idx
  ON pipeline_cache(type, config_version, first_frame_used);
DELETE FROM aurora_schema;
INSERT INTO aurora_schema VALUES ({});)",
          PipelineCacheSchema);
      ret = sqlite::exec(g_pipelineCacheDb, schemaSql.c_str());
      if (ret != SQLITE_OK) {
        Log.error("Failed to initialize pipeline cache schema: {}", sqlite3_errmsg(g_pipelineCacheDb));
        schemaFailed = true;
      }
    }

    if (!schemaFailed) {
      tx.commit();
    }
  }

  if (schemaFailed) {
    pipeline_cache_abort();
    return false;
  }

  ret = sqlite3_prepare_v3(g_pipelineCacheDb,
                           "SELECT config, first_frame_used FROM pipeline_cache "
                           "WHERE type = ? AND config_version = ? "
                           "ORDER BY first_frame_used ASC, rowid ASC",
                           -1, SQLITE_PREPARE_PERSISTENT, &g_pipelineCacheLoadStmt, nullptr);
  if (ret != SQLITE_OK) {
    Log.error("Failed to prepare pipeline cache load statement: {}", sqlite3_errmsg(g_pipelineCacheDb));
    pipeline_cache_abort();
    return false;
  }

  ret = sqlite3_prepare_v3(
      g_pipelineCacheDb,
      "INSERT INTO pipeline_cache (type, hash, config_version, config_size, config, first_frame_used) "
      "VALUES (?, ?, ?, ?, ?, ?) "
      "ON CONFLICT(type, hash) DO UPDATE SET "
      "config_version = excluded.config_version, "
      "config_size = excluded.config_size, "
      "config = excluded.config, "
      "first_frame_used = MIN(pipeline_cache.first_frame_used, excluded.first_frame_used)",
      -1, SQLITE_PREPARE_PERSISTENT, &g_pipelineCacheUpsertStmt, nullptr);
  if (ret != SQLITE_OK) {
    Log.error("Failed to prepare pipeline cache upsert statement: {}", sqlite3_errmsg(g_pipelineCacheDb));
    pipeline_cache_abort();
    return false;
  }

  return true;
}

static void prune_old_pipeline_cache_versions() {
  if (!prepare_pipeline_cache_db()) {
    return;
  }

  const auto clearDelete = fmt::format("DELETE FROM pipeline_cache WHERE type = {} AND config_version < {}",
                                       underlying(ShaderType::Clear), clear::ClearPipelineConfigVersion);
  auto ret = sqlite::exec(g_pipelineCacheDb, clearDelete.c_str());
  if (ret != SQLITE_OK) {
    Log.error("Failed to prune clear pipeline cache rows: {}", sqlite3_errmsg(g_pipelineCacheDb));
    pipeline_cache_abort();
    return;
  }

  const auto gxDelete = fmt::format("DELETE FROM pipeline_cache WHERE type = {} AND config_version < {}",
                                    underlying(ShaderType::GX), gx::GXPipelineConfigVersion);
  ret = sqlite::exec(g_pipelineCacheDb, gxDelete.c_str());
  if (ret != SQLITE_OK) {
    Log.error("Failed to prune GX pipeline cache rows: {}", sqlite3_errmsg(g_pipelineCacheDb));
    pipeline_cache_abort();
  }
}

static bool write_pipeline_cache_record(const PipelineCacheWrite& write) {
  const auto fail = [&]() {
    sqlite3_reset(g_pipelineCacheUpsertStmt);
    sqlite3_clear_bindings(g_pipelineCacheUpsertStmt);
    return false;
  };

  auto ret = sqlite3_bind_int(g_pipelineCacheUpsertStmt, 1, underlying(write.type));
  if (ret != SQLITE_OK) {
    Log.error("Failed to bind pipeline cache type: {}", sqlite3_errmsg(g_pipelineCacheDb));
    return fail();
  }
  ret = sqlite3_bind_int64(g_pipelineCacheUpsertStmt, 2, static_cast<sqlite3_int64>(write.hash));
  if (ret != SQLITE_OK) {
    Log.error("Failed to bind pipeline cache hash: {}", sqlite3_errmsg(g_pipelineCacheDb));
    return fail();
  }
  ret = sqlite3_bind_int(g_pipelineCacheUpsertStmt, 3, static_cast<int>(write.configVersion));
  if (ret != SQLITE_OK) {
    Log.error("Failed to bind pipeline cache config version: {}", sqlite3_errmsg(g_pipelineCacheDb));
    return fail();
  }
  ret = sqlite3_bind_int(g_pipelineCacheUpsertStmt, 4, static_cast<int>(write.config.size()));
  if (ret != SQLITE_OK) {
    Log.error("Failed to bind pipeline cache config size: {}", sqlite3_errmsg(g_pipelineCacheDb));
    return fail();
  }
  ret = sqlite3_bind_blob64(g_pipelineCacheUpsertStmt, 5, write.config.data(), write.config.size(), SQLITE_TRANSIENT);
  if (ret != SQLITE_OK) {
    Log.error("Failed to bind pipeline cache config blob: {}", sqlite3_errmsg(g_pipelineCacheDb));
    return fail();
  }
  ret = sqlite3_bind_int64(g_pipelineCacheUpsertStmt, 6, static_cast<sqlite3_int64>(write.firstFrameUsed));
  if (ret != SQLITE_OK) {
    Log.error("Failed to bind pipeline cache first-frame-used: {}", sqlite3_errmsg(g_pipelineCacheDb));
    return fail();
  }

  ret = sqlite3_step(g_pipelineCacheUpsertStmt);
  if (ret != SQLITE_DONE) {
    Log.error("Failed to upsert pipeline cache row: {}", sqlite3_errmsg(g_pipelineCacheDb));
    return fail();
  }

  sqlite3_reset(g_pipelineCacheUpsertStmt);
  sqlite3_clear_bindings(g_pipelineCacheUpsertStmt);
  return true;
}

static void pipeline_cache_writer() {
#ifdef TRACY_ENABLE
  tracy::SetThreadName("Pipeline cache writer thread");
#endif

  while (true) {
    std::deque<PipelineCacheWrite> batch;
    {
      std::unique_lock lock{g_pipelineCacheWriterMutex};
      g_pipelineCacheWriterCv.wait(lock,
                                   [] { return g_pipelineCacheWriterStop || !g_pipelineCacheWriteQueue.empty(); });
      if (g_pipelineCacheWriterStop && g_pipelineCacheWriteQueue.empty()) {
        return;
      }
      batch.swap(g_pipelineCacheWriteQueue);
    }

    bool writeFailed = false;
    {
      sqlite::Transaction tx(g_pipelineCacheDb, Log, true);
      if (!tx) {
        Log.error("Failed to begin pipeline cache write transaction");
        writeFailed = true;
      } else {
        for (const auto& write : batch) {
          if (!write_pipeline_cache_record(write)) {
            writeFailed = true;
            break;
          }
        }

        if (!writeFailed) {
          tx.commit();
        }
      }
    }

    if (writeFailed) {
      pipeline_cache_abort();
      return;
    }
  }
}

static void pipeline_worker() {
#ifdef TRACY_ENABLE
  tracy::SetThreadName("Pipeline compilation thread");
#endif

  bool hasMore = false;
  while (g_hasPipelineThread || g_pipelinesPerFrame < BuildPipelinesPerFrame) {
    PendingPipeline pending;
    {
      std::unique_lock lock{g_pipelineMutex};
      if (g_hasPipelineThread) {
        if (!hasMore) {
          g_pipelineCv.wait(lock, [] {
            return !g_priorityPipelines.empty() || !g_backgroundPipelines.empty() || g_pipelineThreadEnd;
          });
        }
      } else if (g_priorityPipelines.empty() && g_backgroundPipelines.empty()) {
        return;
      }
      if (g_pipelineThreadEnd) {
        break;
      }
      auto& source = !g_priorityPipelines.empty() ? g_priorityPipelines : g_backgroundPipelines;
      pending = std::move(source.front());
      source.pop_front();
    }
    auto result = pending.create();
    {
      std::lock_guard lock{g_pipelineMutex};
      g_pipelines.try_emplace(pending.hash, CachedPipeline{
                                                .pipeline = std::move(result),
                                                .firstFrameUsed = pending.firstFrameUsed,
                                            });
      g_pendingPipelines.erase(pending.hash);
      hasMore = !g_priorityPipelines.empty() || !g_backgroundPipelines.empty();
    }
    if (!g_hasPipelineThread) {
      ++g_pipelinesPerFrame;
    }
    ++createdPipelines;
    --queuedPipelines;
  }
}

template <typename PipelineConfig, typename CreateFn>
static void load_pipeline_cache_entries(ShaderType type, uint32_t configVersion, CreateFn&& create) {
  if (!prepare_pipeline_cache_db()) {
    return;
  }

  auto ret = sqlite3_bind_int(g_pipelineCacheLoadStmt, 1, underlying(type));
  if (ret != SQLITE_OK) {
    Log.error("Failed to bind pipeline cache load type: {}", sqlite3_errmsg(g_pipelineCacheDb));
    pipeline_cache_abort();
    return;
  }
  ret = sqlite3_bind_int(g_pipelineCacheLoadStmt, 2, static_cast<int>(configVersion));
  if (ret != SQLITE_OK) {
    Log.error("Failed to bind pipeline cache load config version: {}", sqlite3_errmsg(g_pipelineCacheDb));
    pipeline_cache_abort();
    return;
  }

  while ((ret = sqlite3_step(g_pipelineCacheLoadStmt)) == SQLITE_ROW) {
    const auto* configBlob = static_cast<const uint8_t*>(sqlite3_column_blob(g_pipelineCacheLoadStmt, 0));
    const auto configSize = sqlite3_column_bytes(g_pipelineCacheLoadStmt, 0);
    const auto firstFrameUsed = static_cast<uint32_t>(sqlite3_column_int64(g_pipelineCacheLoadStmt, 1));
    if (configSize != static_cast<int>(sizeof(PipelineConfig)) || (configSize != 0 && configBlob == nullptr)) {
      continue;
    }

    PipelineConfig config;
    std::memcpy(&config, configBlob, sizeof(config));
    if (config.version != configVersion) {
      continue;
    }

    find_pipeline_impl(type, config, [=] { return create(config); }, false, firstFrameUsed);
  }

  if (ret != SQLITE_DONE) {
    Log.error("Failed to read pipeline cache rows: {}", sqlite3_errmsg(g_pipelineCacheDb));
    pipeline_cache_abort();
  }

  sqlite3_reset(g_pipelineCacheLoadStmt);
  sqlite3_clear_bindings(g_pipelineCacheLoadStmt);
}

static void load_pipeline_cache() {
  if (!prepare_pipeline_cache_db()) {
    return;
  }
  prune_old_pipeline_cache_versions();
  if (g_pipelineCacheBroken) {
    return;
  }

  load_pipeline_cache_entries<clear::PipelineConfig>(ShaderType::Clear, clear::ClearPipelineConfigVersion,
                                                     clear::create_pipeline);
  if (g_pipelineCacheBroken) {
    return;
  }
  load_pipeline_cache_entries<gx::PipelineConfig>(ShaderType::GX, gx::GXPipelineConfigVersion, gx::create_pipeline);
}

static void start_pipeline_cache_writer() {
  if (!prepare_pipeline_cache_db()) {
    return;
  }

  g_pipelineCacheWriterStop = false;
  g_pipelineCacheWriterThread = std::thread(pipeline_cache_writer);
}

static void stop_pipeline_cache_writer() {
  if (g_pipelineCacheWriterThread.joinable()) {
    {
      std::lock_guard lock{g_pipelineCacheWriterMutex};
      g_pipelineCacheWriterStop = true;
    }
    g_pipelineCacheWriterCv.notify_one();
    g_pipelineCacheWriterThread.join();
  } else {
    g_pipelineCacheWriterStop = false;
  }

  g_pipelineCacheWriteQueue.clear();
}

template <>
PipelineRef find_pipeline(ShaderType type, const clear::PipelineConfig& config, NewPipelineCallback&& cb) {
  return find_pipeline_impl(type, config, std::move(cb), true, std::nullopt);
}

template <>
PipelineRef find_pipeline(ShaderType type, const gx::PipelineConfig& config, NewPipelineCallback&& cb) {
  return find_pipeline_impl(type, config, std::move(cb), true, std::nullopt);
}

void initialize_pipeline_cache() {
  g_pipelineCacheBroken = false;
  g_pipelineCacheWriterStop = false;
  g_pipelineFrameActive = false;
  g_pipelineThreadEnd = false;

  if (webgpu::g_backendType == wgpu::BackendType::OpenGL || webgpu::g_backendType == wgpu::BackendType::OpenGLES ||
      webgpu::g_backendType == wgpu::BackendType::WebGPU) {
    g_hasPipelineThread = false;
  } else {
    g_hasPipelineThread = true;
    g_pipelineThread = std::thread(pipeline_worker);
  }

  load_pipeline_cache();
  if (!g_pipelineCacheBroken) {
    start_pipeline_cache_writer();
  }
}

void shutdown_pipeline_cache() {
  if (g_hasPipelineThread) {
    g_pipelineThreadEnd = true;
    g_pipelineCv.notify_all();
    g_pipelineThread.join();
  }
  g_hasPipelineThread = false;

  stop_pipeline_cache_writer();
  pipeline_cache_abort();
  g_pipelineCacheBroken = false;
  g_pipelineFrameActive = false;
  g_pipelinesPerFrame = 0;
  g_pipelines.clear();
  g_priorityPipelines.clear();
  g_backgroundPipelines.clear();
  g_pendingPipelines.clear();

  queuedPipelines = 0;
  createdPipelines = 0;
}

void begin_pipeline_frame() {
  g_pipelineFrameActive = true;
  if (!g_hasPipelineThread) {
    g_pipelinesPerFrame = 0;
  }
}

void end_pipeline_frame() {
  g_pipelineFrameActive = false;
  if (!g_hasPipelineThread) {
    pipeline_worker();
  }
}

bool get_pipeline(PipelineRef ref, wgpu::RenderPipeline& pipeline) {
  std::lock_guard guard{g_pipelineMutex};
  const auto it = g_pipelines.find(ref);
  if (it == g_pipelines.end()) {
    return false;
  }
  pipeline = it->second.pipeline;
  return true;
}

} // namespace aurora::gfx