#include "UI.hpp"

#include "Model/Project.hpp"
#include "UI/Localization.hpp"
#include "UI/States.hpp"
#include "Utils/ScopeGuard.hpp"
#include "cplt_fwd.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 SalesViewTab {
private:
	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 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;

	// TODO this is very impractical (running filter in client code instead of letting SQLite doing it)
	// Maybe simply cache a list of indices produced by a sql query?

	/// A bitset of all active (should-be-displayed) entries based on current filter, updated whenever \c mActiveFilter is updated.
	/// Should have the exact same size as \c entries.
	std::vector<bool> mActiveEntries;

	/// A cached list of index to entries that should be displayed on the current page.
	std::vector<int> mCurrentPageEntries;

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

	/* UI states */

	int mSelectedEntry;

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

		mEntries.clear();
		mCurrentPage = 0;
		mLastPage = -1;

		mSelectedEntry = -1;
	}

	void OnFilterChanged(std::unique_ptr<TableRowsFilter> filter) {
		// TODO
	}

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

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

		ImGui::SameLine();
		if (ImGui::Button(ls->Edit.Get(), mSelectedEntry == -1)) {
			ImGui::OpenPopup(ls->EditSaleEntryDialogTitle.Get());
		}
		if (ImGui::BeginPopupModal(ls->EditSaleEntryDialogTitle.Get(), &dummy, ImGuiWindowFlags_AlwaysAutoResize)) {
			// TODO
			ImGui::EndPopup();
		}

		if (ImGui::BeginTable("##SalesTable", 3)) {

			ImGui::TableSetupColumn(ls->DatabaseCustomerColumn.Get());
			ImGui::TableSetupColumn(ls->DatabaseDeadlineColumn.Get());
			ImGui::TableSetupColumn(ls->DatabaseDeliveryTimeColumn.Get());
			ImGui::TableHeadersRow();

			for (int i : mCurrentPageEntries) {
				auto& entry = mEntries[i];

				ImGui::TableNextColumn();
				if (ImGui::Selectable(entry.Customer.c_str(), mSelectedEntry == i)) {
					mSelectedEntry = i;
				}

				ImGui::NextColumn();
				ImGui::Text("%s", entry.Deadline.c_str());

				ImGui::NextColumn();
				if (entry.DeliveryTime.empty()) {
					ImGui::Text("%s", ls->NotDeliveredMessage.Get());
				} else {
					ImGui::Text("%s", entry.DeliveryTime.c_str());
				}
			}

			ImGui::EndTable();
		}
	}

private:
	void SetPage(int page) {
		if (mCurrentPage != page) return;

		mCurrentPage = page;
		EnsureCacheCoversPage(page);

		auto [begin, end] = CalcRangeForPage(page);
		begin -= mFirstCachedRowId;
		end -= mFirstCachedRowId;

		mCurrentPageEntries.clear();
		for (auto i = begin; i < end; ++i) {
			if (mActiveEntries[i]) {
				mCurrentPageEntries.push_back(i);
			}
		}
	}

	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) * kMaxEntriesPerPage;
			doRebuild = true;
		}
		if (lastRow > mLastCachedRowId) {
			newLast = CalcPageForRowId(lastRow) * kMaxEntriesPerPage;
			doRebuild = true;
		}
		if (!doRebuild) return;

		auto front = LoadRange(newFirst, mFirstCachedRowId);
		auto back = LoadRange(mLastCachedRowId + 1, newLast + 1);

		mEntries.insert(mEntries.begin(), front.begin(), front.end());
		mEntries.insert(mEntries.end(), back.begin(), back.end());
		// TODO update mActiveEntries

		mFirstCachedRowId = newFirst;
		mLastCachedRowId = newLast;
	}

	std::vector<SaleEntry> LoadRange(int64_t begin, int64_t end) {
		std::vector<SaleEntry> result;

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

		result.reserve(size);

		auto& stmt = mProject->GetDatabase().GetSales().GetRowsStatement;
		DEFER {
			stmt.reset();
		};

		stmt.bind(1, begin);
		stmt.bind(2, end);

		while (true) {
			bool hasResult = stmt.executeStep();
			if (hasResult) {
				result.push_back(stmt.getColumns<SaleEntry, 3>());
			} else {
				return result;
			}
		}
	}

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

	/// Calculate range [begin, end) of row ids that the path-th page would show.
	static std::pair<int64_t, int64_t> CalcRangeForPage(int page) {
		int begin = page * kMaxEntriesPerPage;
		return { begin, begin + kMaxEntriesPerPage };
	}
};

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

class PurchasesViewTab {
private:
	std::vector<PurchaseEntry> mEntries;
	int mCurrentPage = 0;

public:
	void OnProjectChanged(Project* newProject) {
		// TODO
	}

	void Draw() {
		auto ls = LocaleStrings::Instance.get();
		if (ImGui::BeginTable("##PurcahsesTable", 4)) {
			ImGui::EndTable();
		}
	}
};
} // namespace

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

	static Project* currentProject = nullptr;
	static auto salesView = std::make_unique<SalesViewTab>();
	static auto purchasesView = std::make_unique<PurchasesViewTab>();

	if (currentProject != uis.CurrentProject.get()) {
		currentProject = uis.CurrentProject.get();
		salesView->OnProjectChanged(currentProject);
		purchasesView->OnProjectChanged(currentProject);
	}

	if (ImGui::BeginTabBar("##DatabaseViewTabs")) {
		if (ImGui::BeginTabItem(ls->SalesViewTab.Get())) {
			salesView->Draw();
			ImGui::EndTabItem();
		}
		if (ImGui::BeginTabItem(ls->PurchasesViewTab.Get())) {
			purchasesView->Draw();
			ImGui::EndTabItem();
		}
		//		if (ImGui::BeginTabItem(ls->DeliveriesTableTab.Get())) {
		//			ImGui::EndTabItem();
		//		}
	}
}