#include "UI.hpp"

#include "Model/Filter.hpp"
#include "Model/Project.hpp"
#include "UI/Localization.hpp"
#include "UI/States.hpp"
#include "Utils/ScopeGuard.hpp"
#include "Utils/Time.hpp"

#include <IconsFontAwesome.h>
#include <SQLiteCpp/Statement.h>
#include <imgui.h>
#include <cstdint>
#include <memory>
#include <vector>

namespace {

// TODO move to Settings
constexpr int kMaxEntriesPerPage = 20;

class SaleEntry {
public:
	std::string Customer;
	std::string Deadline;
	std::string DeliveryTime;
};

class PurchaseEntry {
public:
	std::string Factory;
	std::string OrderTime;
	std::string DeliveryTime;
};

class GenericTableView {
protected:
	// Translation entries for implementer to fill out
	const char* mEditDialogTitle;

	SQLite::Statement* mGetRowCountStatement;
	SQLite::Statement* mGetRowsStatement;

	Project* mProject;

	/// Current active filter object, or \c nullptr.
	std::unique_ptr<TableRowsFilter> mActiveFilter;

	/// Inclusive.
	/// \see mLastCachedRowId
	int64_t mFirstCachedRowId;
	/// Inclusive.
	/// \see mFirstCachedRowId
	int64_t mLastCachedRowId;

	/// A vector of row ids of entries (in \c mEntries) that are visible under the current filter. To use these indices, the elements should be mapped to
	/// index of the list of entries by adding \c mFirstCachedRowId.
	/// The list of entries is a cached, contiguous (row id of each entry is monotonically increasing, but not necessarily starts at 0) list
	/// of ready-to-be-presented entries, held by the implementer.
	std::vector<int> mActiveEntries;

	/// Number of rows in the table.
	int mRowCount;
	/// Last possible page for the current set table and filter (inclusive).
	int mLastPage;
	/// The current page the user is on.
	int mCurrentPage;

	int mSelectedEntryRowId;

public:
	static int CalcPageForRowId(int64_t rowId) {
		return rowId / kMaxEntriesPerPage;
	}

	/// Calculate range [begin, end) of index for the list of entries that are currently visible that the path-th page would show.
	/// i.e. when there is a filter, look into \c mActiveEntryIndices; when there is no filter, use directly.
	static std::pair<int64_t, int64_t> CalcRangeForPage(int page) {
		int begin = page * kMaxEntriesPerPage;
		return { begin, begin + kMaxEntriesPerPage };
	}

	Project* GetProject() const {
		return mProject;
	}

	virtual void OnProjectChanged(Project* newProject) {
		mProject = newProject;

		if (mGetRowCountStatement->executeStep()) {
			mRowCount = mGetRowCountStatement->getColumn(0).getInt();
		} else {
			// TODO report error
		}

		mFirstCachedRowId = 0;
		mLastCachedRowId = 0;

		ClearEntries();
		mActiveEntries.clear();

		UpdateLastPage();
		SetPage(0);

		mSelectedEntryRowId = -1;
	}

	TableRowsFilter* GetFilter() const {
		return mActiveFilter.get();
	}

	virtual void OnFilterChanged() {
		auto& stmt = mProject->GetTransactionsModel().GetSales().FilterRowsStatement;
		DEFER {
			stmt.reset();
		};

		// TODO lazy loading when too many results
		mActiveEntries.clear();
		int columnIdx = stmt.getColumnIndex("rowid");
		while (stmt.executeStep()) {
			mActiveEntries.push_back(stmt.getColumn(columnIdx).getInt());
		}

		UpdateLastPage();
		SetPage(0);

		mSelectedEntryRowId = -1;
	}

	void OnFilterChanged(std::unique_ptr<TableRowsFilter> filter) {
		mActiveFilter = std::move(filter);
		OnFilterChanged();
	}

	void Draw() {
		bool dummy = true;
		auto ls = LocaleStrings::Instance.get();

		if (ImGui::Button(ICON_FA_ARROW_LEFT, mCurrentPage == 0)) {
			mSelectedEntryRowId = -1;
			SetPage(mCurrentPage - 1);
		}

		ImGui::SameLine();
		// +1 to convert from 0-based indices to 1-based, for human legibility
		ImGui::Text("%d/%d", mCurrentPage + 1, mLastPage + 1);

		ImGui::SameLine();
		if (ImGui::Button(ICON_FA_ARROW_RIGHT, mCurrentPage == mLastPage)) {
			mSelectedEntryRowId = -1;
			SetPage(mCurrentPage + 1);
		}

		ImGui::SameLine();
		if (ImGui::Button(ls->Edit.Get(), mSelectedEntryRowId == -1)) {
			ImGui::OpenPopup(mEditDialogTitle);
		}
		if (ImGui::BeginPopupModal(mEditDialogTitle, &dummy, ImGuiWindowFlags_AlwaysAutoResize)) {
			EditEntry(mSelectedEntryRowId);
			ImGui::EndPopup();
		}

		if (ImGui::BeginTable("", GetTableColumnCount())) {

			SetupTableColumns();
			ImGui::TableHeadersRow();

			auto [begin, end] = CalcRangeForPage(mCurrentPage);
			if (mActiveFilter) {
				end = std::min(end, (int64_t)mActiveEntries.size() - 1);
				for (int i = begin; i < end; ++i) {
					int rowId = mActiveEntries[i];
					DisplayEntry(rowId);
				}
			} else {
				end = std::min(end, mLastCachedRowId);
				for (int rowId = begin; rowId < end; ++rowId) {
					DisplayEntry(rowId);
				}
			}

			ImGui::EndTable();
		}
	}

	void SetPage(int page) {
		mCurrentPage = page;
		EnsureCacheCoversPage(page);
	}

	int RowIdToIndex(int64_t rowId) const {
		return rowId - mFirstCachedRowId;
	}

	int64_t IndexToRowId(int index) const {
		return index + mFirstCachedRowId;
	}

protected:
	virtual int GetTableColumnCount() const = 0;
	virtual void SetupTableColumns() = 0;

	virtual void DisplayEntry(int rowId) = 0;
	virtual void EditEntry(int rowId) = 0;

	virtual void ClearEntries() = 0;

	void EnsureCacheCoversPage(int page) {
		auto [begin, end] = CalcRangeForPage(page);
		EnsureCacheCovers(begin, end - 1);
	}

	void EnsureCacheCovers(int64_t firstRow, int64_t lastRow) {
		if (firstRow > lastRow) {
			std::swap(firstRow, lastRow);
		}

		int newFirst = mFirstCachedRowId;
		int newLast = mLastCachedRowId;

		bool doRebuild = false;
		if (firstRow < mFirstCachedRowId) {
			newFirst = (CalcPageForRowId(firstRow) + 1) * kMaxEntriesPerPage;
			doRebuild = true;
		}
		if (lastRow > mLastCachedRowId) {
			newLast = (CalcPageForRowId(lastRow) + 1) * kMaxEntriesPerPage;
			doRebuild = true;
		}
		if (!doRebuild) return;

		EnsureCacheCoversImpl(newFirst, newLast);
	}

	/// To be implemented by child classes, presumable calling LoadRange() to get the front and back new contents.
	/// \param newFirst The first rowid the new cache should cover
	/// \param newLast The last rowid the new cache should cover
	virtual void EnsureCacheCoversImpl(int newFirst, int newLast) = 0;

	template <class TEntry, class TCollector>
	std::vector<TEntry> LoadRange(int64_t begin, int64_t end, TCollector&& collector) {
		std::vector<TEntry> result;

		size_t size = end - begin;
		if (size == 0) {
			return result;
		}

		result.reserve(size);

		DEFER {
			mGetRowsStatement->reset();
		};

		mGetRowsStatement->bind(1, begin);
		mGetRowsStatement->bind(2, end);

		collector(result);
		return result;
	}

	void UpdateLastPage() {
		mLastPage = mActiveEntries.empty()
			? CalcPageForRowId(mRowCount)
			: CalcPageForRowId(mActiveEntries.back());
	}
};

class SalesTableView : public GenericTableView {
private:
	/// A cached, contiguous (row id of each entry is monotonically increasing, but not necessarily starts at 0) list ready-to-be-presented entries. May be incomplete.
	std::vector<SaleEntry> mEntries;

public:
	SalesTableView() {
		auto ls = LocaleStrings::Instance.get();
		mEditDialogTitle = ls->EditSaleEntryDialogTitle.Get();
	}

	virtual void OnProjectChanged(Project* newProject) override {
		auto& sales = newProject->GetTransactionsModel().GetSales();
		mGetRowCountStatement = &sales.GetRowCountStatement;
		mGetRowsStatement = &sales.GetRowsStatement;

		GenericTableView::OnProjectChanged(newProject);
	}

protected:
	virtual int GetTableColumnCount() const override {
		return 3;
	}

	virtual void SetupTableColumns() override {
		auto ls = LocaleStrings::Instance.get();
		ImGui::TableSetupColumn(ls->DatabaseCustomerColumn.Get());
		ImGui::TableSetupColumn(ls->DatabaseDeadlineColumn.Get());
		ImGui::TableSetupColumn(ls->DatabaseDeliveryTimeColumn.Get());
	}

	virtual void DisplayEntry(int rowId) override {
		auto& entry = GetEntry(rowId);
		auto ls = LocaleStrings::Instance.get();

		ImGui::PushID(rowId);
		ImGui::TableNextRow();

		ImGui::TableNextColumn();
		if (ImGui::Selectable(entry.Customer.c_str(), mSelectedEntryRowId == rowId, ImGuiSelectableFlags_SpanAllColumns)) {
			mSelectedEntryRowId = rowId;
		}

		ImGui::TableNextColumn();
		ImGui::TextUnformatted(entry.Deadline.c_str());

		ImGui::TableNextColumn();
		if (entry.DeliveryTime.empty()) {
			ImGui::TextUnformatted(ls->NotDelievered.Get());
		} else {
			ImGui::TextUnformatted(entry.DeliveryTime.c_str());
		}

		ImGui::PopID();
	}

	virtual void EditEntry(int rowId) override {
		// TODO
	}

	virtual void ClearEntries() override {
		mEntries.clear();
	}

	virtual void EnsureCacheCoversImpl(int newFirst, int newLast) override {
		auto CollectRows = [&](std::vector<SaleEntry>& result) {
			auto& stmt = *mGetRowsStatement;
			int customerCol = stmt.getColumnIndex("Customer");
			int deadlineCol = stmt.getColumnIndex("Deadline");
			int deliveryTimeCol = stmt.getColumnIndex("DeliveryTime");

			while (stmt.executeStep()) {
				auto customer = stmt.getColumn(customerCol).getInt();
				auto deadline = stmt.getColumn(deadlineCol).getInt64();
				auto deliveryTime = stmt.getColumn(deliveryTimeCol).getInt64();
				result.push_back(SaleEntry{
					.Customer = mProject->Customers.Find(customer)->GetName(),
					.Deadline = StringifyTimeStamp(deadline),
					.DeliveryTime = StringifyTimeStamp(deliveryTime),
				});
			}
		};

		auto front = LoadRange<SaleEntry>(newFirst, mFirstCachedRowId, CollectRows);
		auto back = LoadRange<SaleEntry>(mLastCachedRowId + 1, newLast + 1, CollectRows);

		mFirstCachedRowId -= front.size();
		mLastCachedRowId += back.size();

		mEntries.insert(mEntries.begin(), std::make_move_iterator(front.begin()), std::make_move_iterator(front.end()));
		mEntries.insert(mEntries.end(), std::make_move_iterator(back.begin()), std::make_move_iterator(back.end()));
	}

	SaleEntry& GetEntry(int rowId) {
		return mEntries[RowIdToIndex(rowId)];
	}
};

class PurchasesTableView : public GenericTableView {
private:
	std::vector<PurchaseEntry> mEntries;

public:
	PurchasesTableView() {
		auto ls = LocaleStrings::Instance.get();
		mEditDialogTitle = ls->EditPurchaseEntryDialogTitle.Get();
	}

	virtual void OnProjectChanged(Project* newProject) override {
		auto& purchases = newProject->GetTransactionsModel().GetPurchases();
		mGetRowCountStatement = &purchases.GetRowCountStatement;
		mGetRowsStatement = &purchases.GetRowsStatement;

		GenericTableView::OnProjectChanged(newProject);
	}

protected:
	virtual int GetTableColumnCount() const override {
		return 3;
	}

	virtual void SetupTableColumns() override {
		auto ls = LocaleStrings::Instance.get();
		ImGui::TableSetupColumn(ls->DatabaseFactoryColumn.Get());
		ImGui::TableSetupColumn(ls->DatabaseOrderTimeColumn.Get());
		ImGui::TableSetupColumn(ls->DatabaseDeliveryTimeColumn.Get());
	}

	virtual void DisplayEntry(int rowId) override {
		auto& entry = GetEntry(rowId);
		auto ls = LocaleStrings::Instance.get();

		ImGui::PushID(rowId);
		ImGui::TableNextRow();

		ImGui::TableNextColumn();
		if (ImGui::Selectable(entry.Factory.c_str(), mSelectedEntryRowId == rowId, ImGuiSelectableFlags_SpanAllColumns)) {
			mSelectedEntryRowId = rowId;
		}

		ImGui::TableNextColumn();
		if (entry.OrderTime.empty()) {
			ImGui::TextUnformatted(ls->NotDelievered.Get());
		} else {
			ImGui::TextUnformatted(entry.OrderTime.c_str());
		}

		ImGui::TableNextColumn();
		if (entry.DeliveryTime.empty()) {
			ImGui::TextUnformatted(ls->NotDelievered.Get());
		} else {
			ImGui::TextUnformatted(entry.DeliveryTime.c_str());
		}

		ImGui::PopID();
	}

	virtual void EditEntry(int rowId) override {
		// TODO
	}

	virtual void ClearEntries() override {
		mEntries.clear();
	}

	virtual void EnsureCacheCoversImpl(int newFirst, int newLast) override {
		auto CollectRows = [&](std::vector<PurchaseEntry>& result) {
			auto& stmt = *mGetRowsStatement;
			int factoryCol = stmt.getColumnIndex("Factory");
			int orderTimeCol = stmt.getColumnIndex("OrderTime");
			int deliveryTimeCol = stmt.getColumnIndex("DeliveryTime");

			while (stmt.executeStep()) {
				auto factory = stmt.getColumn(factoryCol).getInt();
				auto orderTime = stmt.getColumn(orderTimeCol).getInt64();
				auto deliveryTime = stmt.getColumn(deliveryTimeCol).getInt64();
				result.push_back(PurchaseEntry{
					.Factory = mProject->Factories.Find(factory)->GetName(),
					.OrderTime = StringifyTimeStamp(orderTime),
					.DeliveryTime = StringifyTimeStamp(deliveryTime),
				});
			}
		};

		auto front = LoadRange<PurchaseEntry>(newFirst, mFirstCachedRowId, CollectRows);
		auto back = LoadRange<PurchaseEntry>(mLastCachedRowId + 1, newLast + 1, CollectRows);

		mFirstCachedRowId -= front.size();
		mLastCachedRowId += back.size();

		mEntries.insert(mEntries.begin(), std::make_move_iterator(front.begin()), std::make_move_iterator(front.end()));
		mEntries.insert(mEntries.end(), std::make_move_iterator(back.begin()), std::make_move_iterator(back.end()));
	}

	PurchaseEntry& GetEntry(int rowId) {
		return mEntries[RowIdToIndex(rowId)];
	}
};
} // namespace

void UI::DatabaseViewTab() {
	auto ls = LocaleStrings::Instance.get();
	auto& uis = UIState::GetInstance();

	static Project* currentProject = nullptr;
	static SalesTableView sales;
	static PurchasesTableView purchases;

	if (currentProject != uis.CurrentProject.get()) {
		currentProject = uis.CurrentProject.get();
		sales.OnProjectChanged(currentProject);
		purchases.OnProjectChanged(currentProject);
	}

	if (ImGui::BeginTabBar("##DatabaseViewTabs")) {
		if (ImGui::BeginTabItem(ls->SalesViewTab.Get())) {
			sales.Draw();
			ImGui::EndTabItem();
		}
		if (ImGui::BeginTabItem(ls->PurchasesViewTab.Get())) {
			purchases.Draw();
			ImGui::EndTabItem();
		}
		ImGui::EndTabBar();
	}
}