#include "UI.hpp"

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

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

namespace {

// TODO move to Settings
constexpr int kMaxEntriesPerPage = 32;
constexpr int kSummaryItemCount = 3;
constexpr int kSummaryMaxLength = 25;

std::pair<int, int> SplitEntryIndex(int entryIdx)
{
	int page = entryIdx / kMaxEntriesPerPage;
	int row = entryIdx % kMaxEntriesPerPage;
	return { page, row };
}

enum class DeliveryDirection
{
	FactoryToWarehouse,
	WarehouseToCustomer,
};

struct Item
{
	int ItemId;
	int Count;
};

struct DeliveryEntry
{
	std::vector<Item> Items;
	std::string ItemsSummary;
	std::string ShipmentTime;
	std::string ArriveTime;
	DeliveryDirection Direction;

	const char* StringifyDirection() const
	{
		switch (Direction) {
			case DeliveryDirection::FactoryToWarehouse: return "Factory to warehouse";
			case DeliveryDirection::WarehouseToCustomer: return "Warehouse to customer";
		}
	}
};

struct SaleEntry
{
	static constexpr auto kType = DeliveryDirection::WarehouseToCustomer;

	std::vector<DeliveryEntry> AssociatedDeliveries;
	std::vector<Item> Items;
	std::string ItemsSummary;
	std::string Customer;
	std::string Deadline;
	std::string DeliveryTime;
	int Id;
	bool DeliveriesCached = false;
};

struct PurchaseEntry
{
	static constexpr auto kType = DeliveryDirection::FactoryToWarehouse;

	std::vector<DeliveryEntry> AssociatedDeliveries;
	std::vector<Item> Items;
	std::string ItemsSummary;
	std::string Factory;
	std::string OrderTime;
	std::string DeliveryTime;
	int Id;
	bool DeliveriesCached;
};

template <class T>
class GenericTableView
{
public:
	// clang-format off
	static constexpr bool kHasItems = requires(T t)
	{
		t.Items;
		t.ItemsSummary;
	};
	static constexpr bool kHasCustomer = requires(T t) { t.Customer; };
	static constexpr bool kHasDeadline = requires(T t) { t.Deadline; };
	static constexpr bool kHasFactory = requires(T t) { t.Factory; };
	static constexpr bool kHasOrderTime = requires(T t) { t.OrderTime; };
	static constexpr bool kHasCompletionTime = requires(T t) { t.DeliveryTime; };
	static constexpr int kColumnCount = kHasItems + kHasCustomer + kHasDeadline + kHasFactory + kHasOrderTime + kHasCompletionTime;
	// clang-format on

	using Page = std::vector<T>;

	struct QueryStatements
	{
		SQLite::Statement* GetRowCount;
		SQLite::Statement* GetRows;
		SQLite::Statement* GetItems;
		SQLite::Statement* FilterRows;
	} Statements;

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

	Project* mProject;
	Page* mCurrentPage = nullptr;

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

	tsl::robin_map<int, Page> mPages;

	/// A vector of entry indices (in \c mEntries) that are visible under the current filter.
	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 mCurrentPageNumber;

	/// Row index of the select entry
	int mSelectRow;

public:
	/// Calculate the first visible row's entry index.
	int GetFirstVisibleRowIdx() const
	{
		return mCurrentPageNumber * kMaxEntriesPerPage;
	}

	Project* GetProject() const
	{
		return mProject;
	}

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

		auto& stmt = *Statements.GetRowCount;
		if (stmt.executeStep()) {
			mRowCount = stmt.getColumn(0).getInt();
		} else {
			std::cerr << "Failed to fetch row count from SQLite.\n";
			mRowCount = 0;
		}

		mActiveFilter = nullptr;
		mActiveEntries.clear();

		mPages.clear();
		mCurrentPage = nullptr;
		UpdateLastPage();
		SetPage(0);

		mSelectRow = -1;
	}

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

	void OnFilterChanged()
	{
		auto& stmt = *Statements.FilterRows;
		// clang-format off
		DEFER { stmt.reset(); };
		// clang-format on

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

		UpdateLastPage();
		SetPage(0);

		mSelectRow = -1;
	}

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

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

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

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

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

		ImGui::SameLine();
		if (ImGui::Button(ls->Edit.Get(), mSelectRow == -1)) {
			ImGui::OpenPopup(mEditDialogTitle);
		}
		if (ImGui::BeginPopupModal(mEditDialogTitle, &dummy, ImGuiWindowFlags_AlwaysAutoResize)) {
			auto& entry = (*mCurrentPage)[mSelectRow];
			int entryIdx = GetFirstVisibleRowIdx() + mSelectRow;
			EditEntry(entry, entryIdx, mSelectRow);
			ImGui::EndPopup();
		}

		ImGui::SameLine();
		if (ImGui::Button(ls->Add.Get())) {
			// TODO
		}

		ImGui::SameLine();
		if (ImGui::Button(ls->Delete.Get(), mSelectRow == -1)) {
			// TODO
		}

		ImGui::Columns(2);
		{
			DisplayMainTable();
			ImGui::NextColumn();

			if (mSelectRow == -1) {
				ImGui::TextWrapped("%s", ls->SelectOrderToShowAssociatedDeliveries.Get());
			} else {
				DisplayDeliveriesTable();
			}
			ImGui::NextColumn();
		}
		ImGui::Columns(1);
	}

	void SetPage(int page)
	{
		mCurrentPageNumber = page;
		mCurrentPage = &LoadAndGetPage(page);
		mSelectRow = -1;
	}

private:
	static int CalcPageForRowId(int64_t entryIdx)
	{
		return entryIdx / 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 };
	}

	void DisplayMainTable()
	{
		auto ls = LocaleStrings::Instance.get();
		if (ImGui::BeginTable("DataTable", kColumnCount, ImGuiTableFlags_Borders | ImGuiTableFlags_ScrollX)) {

			if constexpr (kHasCustomer) ImGui::TableSetupColumn(ls->DatabaseCustomerColumn.Get());
			if constexpr (kHasDeadline) ImGui::TableSetupColumn(ls->DatabaseDeadlineColumn.Get());
			if constexpr (kHasFactory) ImGui::TableSetupColumn(ls->DatabaseFactoryColumn.Get());
			if constexpr (kHasOrderTime) ImGui::TableSetupColumn(ls->DatabaseOrderTimeColumn.Get());
			if constexpr (kHasCompletionTime) ImGui::TableSetupColumn(ls->DatabaseCompletionTimeColumn.Get());
			if constexpr (kHasItems) ImGui::TableSetupColumn(ls->DatabaseItemsColumn.Get());
			ImGui::TableHeadersRow();

			if (mActiveFilter) {
				// TODO
				auto [begin, end] = CalcRangeForPage(mCurrentPageNumber);
				end = std::min(end, (int64_t)mActiveEntries.size() - 1);
				for (int i = begin; i < end; ++i) {
					int rowIdx = mActiveEntries[i];
					DisplayEntry(rowIdx);
				}
			} else {
				int firstRowIdx = mCurrentPageNumber * kMaxEntriesPerPage;
				auto& page = *mCurrentPage;

				int end = std::min((int)page.size(), kMaxEntriesPerPage);
				for (int i = 0; i < end; ++i) {
					DisplayEntry(page[i], i, firstRowIdx + i);
				}
			}

			ImGui::EndTable();
		}
	}

	void DisplayEntry(int rowIdx)
	{
		// TODO
		// auto [pageNumber, pageEntry] = SplitRowIndex(rowIdx);
		// auto& entry = LoadAndGetPage(pageNumber)[pageEntry];
		// DisplayEntry(entry, rowIdx);
	}

	void DisplayEntry(T& entry, int rowIdx, int entryIdx)
	{
		auto ls = LocaleStrings::Instance.get();

		ImGui::PushID(rowIdx);
		ImGui::TableNextRow();

		if constexpr (kHasCustomer) {
			ImGui::TableNextColumn();
			if (ImGui::Selectable(entry.Customer.c_str(), mSelectRow == rowIdx, ImGuiSelectableFlags_SpanAllColumns)) {
				mSelectRow = rowIdx;
			}
		}

		if constexpr (kHasDeadline) {
			ImGui::TableNextColumn();
			ImGui::TextUnformatted(entry.Deadline.c_str());
		}

		if constexpr (kHasFactory) {
			ImGui::TableNextColumn();
			if (ImGui::Selectable(entry.Factory.c_str(), mSelectRow == rowIdx, ImGuiSelectableFlags_SpanAllColumns)) {
				mSelectRow = rowIdx;
			}
		}

		if constexpr (kHasOrderTime) {
			ImGui::TableNextColumn();
			ImGui::TextUnformatted(entry.OrderTime.c_str());
		}

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

		if constexpr (kHasItems) {
			ImGui::TableNextColumn();
			if (ImGui::TreeNode(entry.ItemsSummary.c_str())) {
				DrawItems(entry.Items);
				ImGui::TreePop();
			}
		}

		ImGui::PopID();
	}

	void EditEntry(T& entry, int rowIdx, int entryIdx)
	{
		// TODO
	}

	void DisplayDeliveriesTable()
	{
		auto ls = LocaleStrings::Instance.get();
		if (ImGui::BeginTable("DeliveriesTable", 3, ImGuiTableFlags_Borders | ImGuiTableFlags_ScrollX)) {

			ImGui::TableSetupColumn(ls->DatabaseShipmentTimeColumn.Get());
			ImGui::TableSetupColumn(ls->DatabaseArrivalTimeColumn.Get());
			ImGui::TableSetupColumn(ls->DatabaseItemsColumn.Get());
			ImGui::TableHeadersRow();

			auto& entry = (*mCurrentPage)[mSelectRow];
			auto& deliveries = entry.AssociatedDeliveries;
			for (auto& delivery : deliveries) {
				ImGui::TableNextRow();

				ImGui::TableNextColumn();
				ImGui::TextUnformatted(delivery.ShipmentTime.c_str());

				ImGui::TableNextColumn();
				ImGui::TextUnformatted(delivery.ArriveTime.c_str());

				ImGui::TableNextColumn();
				if (ImGui::TreeNode(delivery.ItemsSummary.c_str())) {
					DrawItems(delivery.Items);
					ImGui::TreePop();
				}
			}

			ImGui::EndTable();
		}
	}

	std::vector<Item> LoadItems(SQLite::Statement& stmt, int64_t id)
	{
		// clang-format off
		DEFER { stmt.reset(); };
		// clang-format on

		stmt.bind(1, id);

		std::vector<Item> entries;
		int itemIdCol = stmt.getColumnIndex("ItemId");
		int countCol = stmt.getColumnIndex("Count");
		while (stmt.executeStep()) {
			entries.push_back(Item{
				.ItemId = stmt.getColumn(itemIdCol).getInt(),
				.Count = stmt.getColumn(countCol).getInt(),
			});
		}

		return entries;
	}

	std::string CreateItemsSummary(const std::vector<Item>& items)
	{
		if (items.empty()) {
			return "<empty>";
		}

		std::string result;
		for (int i = 0, max = std::min((int)items.size(), kSummaryItemCount); i < max; ++i) {
			auto& name = mProject->Products.Find(items[i].ItemId)->GetName();
			if (result.length() + name.length() > kSummaryMaxLength) {
				break;
			}

			result += name;
			result += ", ";
		}

		// Remove ", "
		result.pop_back();
		result.pop_back();

		result += "...";

		return result;
	}

	std::vector<DeliveryEntry> LoadDeliveriesEntries(int64_t orderId, DeliveryDirection type)
	{
		bool outgoingFlag;
		switch (type) {
			case DeliveryDirection::FactoryToWarehouse: outgoingFlag = false; break;
			case DeliveryDirection::WarehouseToCustomer: outgoingFlag = true; break;
		}

		auto& stmt = mProject->Database.GetDeliveries().FilterByTypeAndId;
		// clang-format off
		DEFER { stmt.reset(); };
		// clang-format on

		stmt.bind(1, orderId);
		stmt.bind(2, outgoingFlag);

		std::vector<DeliveryEntry> entries;
		int rowIdCol = stmt.getColumnIndex("Id");
		int sendTimeCol = stmt.getColumnIndex("ShipmentTime");
		int arrivalTimeCol = stmt.getColumnIndex("ArrivalTime");
		while (stmt.executeStep()) {
			auto items = LoadItems(
				mProject->Database.GetDeliveries().GetItems,
				stmt.getColumn(rowIdCol).getInt64());
			auto summary = CreateItemsSummary(items);

			entries.push_back(DeliveryEntry{
				.Items = std::move(items),
				.ItemsSummary = std::move(summary),
				.ShipmentTime = TimeUtils::StringifyTimeStamp(stmt.getColumn(arrivalTimeCol).getInt64()),
				.ArriveTime = TimeUtils::StringifyTimeStamp(stmt.getColumn(sendTimeCol).getInt64()),
				.Direction = type,
			});
		}

		return entries;
	}

	Page& LoadAndGetPage(int page)
	{
		auto iter = mPages.find(page);
		if (iter != mPages.end()) {
			return iter.value();
		}

		auto& stmt = *Statements.GetRows;
		// clang-format off
		DEFER { stmt.reset(); };
		// clang-format on

		stmt.bind(1, kMaxEntriesPerPage);
		stmt.bind(2, page * kMaxEntriesPerPage);

		// If a field flag is false, the column index won't be used (controlled by other if constexpr's downstream)
		// so there is no UB here

		// This column is always necessary (and present) because the deliveries table require it
		int idCol = stmt.getColumnIndex("Id");

		int customerCol;
		if constexpr (kHasCustomer) customerCol = stmt.getColumnIndex("Customer");

		int deadlineCol;
		if constexpr (kHasDeadline) deadlineCol = stmt.getColumnIndex("Deadline");

		int factoryCol;
		if constexpr (kHasFactory) factoryCol = stmt.getColumnIndex("Factory");

		int orderTimeCol;
		if constexpr (kHasOrderTime) orderTimeCol = stmt.getColumnIndex("OrderTime");

		int deliveryTimeCol;
		if constexpr (kHasCompletionTime) deliveryTimeCol = stmt.getColumnIndex("DeliveryTime");

		Page entries;
		while (stmt.executeStep()) {
			auto& entry = entries.emplace_back();

			auto id = stmt.getColumn(idCol).getInt64();
			entry.AssociatedDeliveries = LoadDeliveriesEntries(id, T::kType);

			if constexpr (kHasItems) {
				auto items = LoadItems(
					*Statements.GetItems,
					id);
				auto itemsSummary = CreateItemsSummary(items);
				entry.Items = std::move(items);
				entry.ItemsSummary = std::move(itemsSummary);
			}

			if constexpr (kHasCustomer) {
				auto customerId = stmt.getColumn(customerCol).getInt();
				entry.Customer = mProject->Customers.Find(customerId)->GetName();
			}

			if constexpr (kHasDeadline) {
				auto timeStamp = stmt.getColumn(deadlineCol).getInt64();
				entry.Deadline = TimeUtils::StringifyTimeStamp(timeStamp);
			}

			if constexpr (kHasFactory) {
				auto factoryId = stmt.getColumn(factoryCol).getInt();
				entry.Factory = mProject->Factories.Find(factoryId)->GetName();
			}

			if constexpr (kHasOrderTime) {
				auto timeStamp = stmt.getColumn(orderTimeCol).getInt64();
				entry.OrderTime = TimeUtils::StringifyTimeStamp(timeStamp);
			}

			if constexpr (kHasCompletionTime) {
				auto timeStamp = stmt.getColumn(deliveryTimeCol).getInt64();
				entry.DeliveryTime = TimeUtils::StringifyTimeStamp(timeStamp);
			}
		}

		auto [res, _] = mPages.try_emplace(page, std::move(entries));
		return res.value();
	}

	void DrawItems(const std::vector<Item>& items)
	{
		for (auto& item : items) {
			auto& name = mProject->Products.Find(item.ItemId)->GetName();
			ImGui::Text("%s × %d", name.c_str(), item.Count);
		}
	}

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

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

#pragma clang diagnostic push
#pragma ide diagnostic ignored "HidingNonVirtualFunction"
	void OnProjectChanged(Project* newProject)
	{
		auto& table = newProject->Database.GetSales();
		Statements.GetRowCount = &table.GetRowCount;
		Statements.GetRows = &table.GetRows;
		Statements.GetItems = &table.GetItems;
		// TODO
		// stmts.FilterRowsStatement = ;

		GenericTableView<SaleEntry>::OnProjectChanged(newProject);
	}
#pragma clang diagnostic pop
};

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

#pragma clang diagnostic push
#pragma ide diagnostic ignored "HidingNonVirtualFunction"
	void OnProjectChanged(Project* newProject)
	{
		auto& table = newProject->Database.GetPurchases();
		Statements.GetRowCount = &table.GetRowCount;
		Statements.GetRows = &table.GetRows;
		Statements.GetItems = &table.GetItems;
		// TODO
		// stmts.FilterRowsStatement = ;

		GenericTableView<PurchaseEntry>::OnProjectChanged(newProject);
	}
#pragma clang diagnostic pop
};
} // namespace

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

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

	if (currentProject != gs.GetCurrentProject()) {
		currentProject = gs.GetCurrentProject();
		sales.OnProjectChanged(currentProject);
		purchases.OnProjectChanged(currentProject);
	}

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