// SPDX-FileCopyrightText: 2015-2025 Alexey Rochev
//
// SPDX-License-Identifier: GPL-3.0-or-later

#include <algorithm>
#include <optional>
#include <set>

#define QTEST_THROW_ON_FAIL

#include <QTest>

#include <fmt/ranges.h>

#include "log/log.h"
#include "itemlistupdater.h"
#include "stdutils.h"

struct Item {
    int id;
    QString data;

    bool operator==(const Item& other) const = default;
    bool operator<(const Item& other) const { return id < other.id; }
    bool operator<=(const Item& other) const { return id <= other.id; }
    bool operator>(const Item& other) const { return id > other.id; }
    bool operator>=(const Item& other) const { return id > other.id; }
};

namespace fmt {
    template<>
    struct formatter<Item> : tremotesf::SimpleFormatter {
        format_context::iterator format(const Item& item, format_context& ctx) const {
            return fmt::format_to(ctx.out(), "Item(id={}, data={})", item.id, item.data);
        }
    };
}

namespace tremotesf {
    class Updater final : public tremotesf::ItemListUpdater<Item> {
    public:
        std::vector<std::pair<size_t, size_t>> aboutToRemoveIndexRanges;
        std::vector<std::pair<size_t, size_t>> removedIndexRanges;
        std::vector<std::pair<size_t, size_t>> changedIndexRanges;
        std::optional<size_t> aboutToAddCount;
        std::optional<size_t> addedCount;

    protected:
        typename std::vector<Item>::iterator
        findNewItemForItem(std::vector<Item>& container, const Item& item) override {
            return std::ranges::find(container, item.id, &Item::id);
        };

        void onAboutToRemoveItems(size_t first, size_t last) override {
            aboutToRemoveIndexRanges.emplace_back(first, last);
        }

        void onRemovedItems(size_t first, size_t last) override { removedIndexRanges.emplace_back(first, last); }

        // NOLINTNEXTLINE(cppcoreguidelines-rvalue-reference-param-not-moved)
        bool updateItem(Item& item, Item&& newItem) override {
            if (item != newItem) {
                item = newItem;
                return true;
            }
            return false;
        }

        void onChangedItems(size_t first, size_t last) override { changedIndexRanges.emplace_back(first, last); }

        Item createItemFromNewItem(Item&& newItem) override { return std::move(newItem); }

        void onAboutToAddItems(size_t count) override {
            if (aboutToAddCount) {
                QFAIL("onAboutToAddItems() must be called only once");
            }
            aboutToAddCount = count;
        }

        void onAddedItems(size_t count) override {
            if (addedCount) {
                QFAIL("onAddedItems() must be called only once");
            }
            addedCount = count;
        }
    };

    class ItemListUpdaterTest final : public QObject {
        Q_OBJECT

    private slots:
        void emptyListDidNotChange() { checkUpdate({}, {}); }

        void singleItemListDidNotChange() { checkUpdate({{42, "666"}}, {{42, "666"}}); }

        void multipleItemsListDidNotChange() {
            checkUpdate({{42, "666"}, {1, "Foo"}, {11, "Bar"}}, {{42, "666"}, {1, "Foo"}, {11, "Bar"}});
        }

        void addedSingleItemToEmptyList() { checkUpdate({}, {{42, "666"}}); }

        void addedMultipleItemsToEmptyList() { checkUpdate({}, {{42, "666"}, {1, "Foo"}}); }

        void addedSingleItemToNonEmptyList() { checkUpdate({{42, "666"}}, {{42, "666"}, {1, "Foo"}}); }

        void addedMultipleItemsToNonEmptyList() { checkUpdate({{42, "666"}}, {{42, "666"}, {1, "Foo"}, {11, "Bar"}}); }

        void removedItemFromSingleItemList() { checkUpdate({{42, "666"}}, {}); }

        void removedLastItemFromMultipleItemsList() { checkUpdate({{42, "666"}, {666, ""}}, {{42, "666"}}); }

        void removedFirstItemFromMultipleItemsList() { checkUpdate({{42, "666"}, {666, ""}}, {{666, ""}}); }

        void removedMiddleItemFromMultipleItemsList() {
            checkUpdate({{42, "666"}, {666, ""}, {1, ""}}, {{42, "666"}, {1, ""}});
        }

        void removedTwoConsecutiveItemsFromEnd() {
            checkUpdate({{42, "666"}, {666, ""}, {1, ""}, {18, "Nope"}}, {{42, "666"}, {666, ""}});
        }

        void removedTwoConsecutiveItemsFromBeginning() {
            checkUpdate({{42, "666"}, {666, ""}, {1, ""}, {18, "Nope"}}, {{1, ""}, {18, "Nope"}});
        }

        void removedTwoConsecutiveItemsFromMiddle() {
            checkUpdate({{42, "666"}, {666, ""}, {1, ""}, {18, "Nope"}}, {{42, "666"}, {18, "Nope"}});
        }

        void removedTwoSeparateItems1() {
            checkUpdate(
                {{42, "666"}, {666, ""}, {1, ""}, {18, "Nope"}, {77, "Foo"}},
                {{42, "666"}, {666, ""}, {18, "Nope"}}
            );
        }

        void removedTwoSeparateItems2() {
            checkUpdate(
                {{42, "666"}, {666, ""}, {1, ""}, {18, "Nope"}, {77, "Foo"}},
                {{666, ""}, {18, "Nope"}, {77, "Foo"}}
            );
        }

        void removedTwoSeparateItems3() {
            checkUpdate(
                {{42, "666"}, {666, ""}, {1, ""}, {18, "Nope"}, {77, "Foo"}},
                {{666, ""}, {1, ""}, {18, "Nope"}}
            );
        }

        void changedSingleItemList() { checkUpdate({{42, "666"}}, {{42, "42"}}); }

        void changedFirstItemInMultipleItemList() {
            checkUpdate({{42, "666"}, {666, ""}, {1, ""}}, {{42, "42"}, {666, ""}, {1, ""}});
        }

        void changedMiddleItemInMultipleItemList() {
            checkUpdate({{42, "666"}, {666, ""}, {1, ""}}, {{42, "666"}, {666, "666"}, {1, ""}});
        }

        void changedLastItemInMultipleItemList() {
            checkUpdate({{42, "666"}, {666, ""}, {1, ""}}, {{42, "666"}, {666, ""}, {1, "nnn"}});
        }

        void changedTwoConsecutiveItemsFromBeginning() {
            checkUpdate(
                {{42, "666"}, {666, ""}, {1, ""}, {18, "Nope"}, {77, "Foo"}},
                {{42, "AAAA"}, {666, "ok"}, {1, ""}, {18, "Nope"}, {77, "Foo"}}
            );
        }

        void changedTwoConsecutiveItemsFromMiddle() {
            checkUpdate(
                {{42, "666"}, {666, ""}, {1, ""}, {18, "Nope"}, {77, "Foo"}},
                {{42, "666"}, {666, ""}, {1, "uhh"}, {18, ""}, {77, "Foo"}}
            );
        }

        void changedTwoConsecutiveItemsFromEnd() {
            checkUpdate(
                {{42, "666"}, {666, ""}, {1, ""}, {18, "Nope"}, {77, "Foo"}},
                {{42, "666"}, {666, ""}, {1, ""}, {18, "arr"}, {77, "qr"}}
            );
        }

        void changedTwoSeparateItems1() {
            checkUpdate(
                {{42, "666"}, {666, ""}, {1, ""}, {18, "Nope"}, {77, "Foo"}},
                {{42, "667"}, {666, ""}, {1, ""}, {18, "Nope"}, {77, "Fooo"}}
            );
        }

        void changedTwoSeparateItems2() {
            checkUpdate(
                {{42, "666"}, {666, ""}, {1, ""}, {18, "Nope"}, {77, "Foo"}},
                {{42, "666"}, {666, "sure"}, {1, ""}, {18, "aoa"}, {77, "Foo"}}
            );
        }

        void changedTwoSeparateItems3() {
            checkUpdate(
                {{42, "666"}, {666, ""}, {1, ""}, {18, "Nope"}, {77, "Foo"}},
                {{42, "666"}, {666, ""}, {1, "uwu"}, {18, "Nope"}, {77, "www"}}
            );
        }

        void removedAndAdded() {
            checkUpdate(
                {{42, "666"}, {666, ""}, {1, ""}, {18, "Nope"}, {77, "Foo"}},
                {{666, ""}, {1, ""}, {18, "Nope"}, {33, "fffu"}, {-2, "ew"}}
            );
        }

        void changedAndAdded() {
            checkUpdate(
                {{42, "666"}, {666, ""}, {1, ""}, {18, "Nope"}, {77, "Foo"}},
                {{42, "666"}, {666, "yeeee"}, {1, "what"}, {18, "Nope"}, {77, "now"}, {999, "big"}}
            );
        }

        void removedChangedAndAdded() {
            checkUpdate(
                {{42, "666"}, {666, ""}, {1, ""}, {18, "Nope"}, {77, "Foo"}},
                {{42, "sad"}, {1, "small"}, {33, "fffu"}, {-2, "ew"}}
            );
        }

        void removedChangedAndAdded2() {
            checkUpdate(
                {{42, "666"}, {666, ""}, {1, ""}, {18, "Nope"}, {77, "Foo"}},
                {{42, "666"}, {666, "333"}, {18, "Nope"}, {77, "Foo"}}
            );
        }

    private:
        void checkUpdate(const std::vector<Item>& oldList, std::vector<Item> newList) {
            checkThatItemsAreUnique(oldList);
            checkThatItemsAreUnique(newList);

            info().log("Checking update from {}", oldList);
            std::ranges::sort(newList);
            do {
                info().log(" - to {}", newList);
                checkUpdateInner(oldList, newList);
            } while (std::ranges::next_permutation(newList).found);
        }

        void checkUpdateInner(const std::vector<Item>& oldList, const std::vector<Item>& newList) {
            auto directlyUpdatedList = oldList;
            Updater updater;
            updater.update(directlyUpdatedList, std::vector(newList));

            QVERIFY(updater.aboutToRemoveIndexRanges == updater.removedIndexRanges);
            QVERIFY(updater.aboutToAddCount == updater.addedCount);

            QCOMPARE(directlyUpdatedList.size(), newList.size());
            checkThatItemsAreUnique(directlyUpdatedList);
            QCOMPARE(
                std::set(directlyUpdatedList.begin(), directlyUpdatedList.end()),
                std::set(newList.begin(), newList.end())
            );

            auto indirectlyUpdatedList = oldList;

            for (const auto& [first, last] : updater.removedIndexRanges) {
                indirectlyUpdatedList.erase(
                    indirectlyUpdatedList.begin() + static_cast<ptrdiff_t>(first),
                    indirectlyUpdatedList.begin() + static_cast<ptrdiff_t>(last)
                );
            }

            for (const auto& [first, last] : updater.changedIndexRanges) {
                std::ranges::copy(
                    slice(directlyUpdatedList, first, last),
                    indirectlyUpdatedList.begin() + static_cast<ptrdiff_t>(first)
                );
                std::ranges::copy(
                    slice(directlyUpdatedList, first, last),
                    indirectlyUpdatedList.begin() + static_cast<ptrdiff_t>(first)
                );
            }

            if (updater.addedCount) {
                indirectlyUpdatedList.reserve(indirectlyUpdatedList.size() + *updater.addedCount);
                std::ranges::copy(
                    std::views::drop(
                        directlyUpdatedList,
                        static_cast<ptrdiff_t>(directlyUpdatedList.size() - *updater.addedCount)
                    ),
                    std::back_insert_iterator(indirectlyUpdatedList)
                );
            }

            QCOMPARE(indirectlyUpdatedList, directlyUpdatedList);
        }

        void checkThatItemsAreUnique(const std::vector<Item>& list) {
            const auto set = std::set(list.begin(), list.end());
            QCOMPARE(set.size(), list.size());
        }
    };
}

QTEST_GUILESS_MAIN(tremotesf::ItemListUpdaterTest)

#include "itemlistupdater_test.moc"
