#include <XCEditor/Panels/UIEditorPanelHostLifecycle.h>

#include <unordered_map>
#include <unordered_set>
#include <utility>

namespace XCEngine::UI::Editor {

namespace {

using HostStateMap = std::unordered_map<std::string_view, const UIEditorPanelHostState*>;

HostStateMap BuildHostStateMap(const std::vector<UIEditorPanelHostState>& states) {
    HostStateMap map = {};
    map.reserve(states.size());
    for (const UIEditorPanelHostState& state : states) {
        map.emplace(state.panelId, &state);
    }
    return map;
}

const UIEditorPanelHostState* FindHostState(
    const std::vector<UIEditorPanelHostState>& states,
    std::string_view panelId) {
    for (const UIEditorPanelHostState& state : states) {
        if (state.panelId == panelId) {
            return &state;
        }
    }

    return nullptr;
}

void AppendLeaveEvents(
    std::vector<UIEditorPanelHostLifecycleEvent>& events,
    const std::vector<UIEditorPanelHostState>& previousStates,
    const HostStateMap& currentStateMap) {
    auto appendCategory = [&](auto predicate, UIEditorPanelHostLifecycleEventKind kind) {
        for (const UIEditorPanelHostState& previous : previousStates) {
            const UIEditorPanelHostState emptyState = {};
            const UIEditorPanelHostState& current =
                currentStateMap.contains(previous.panelId)
                    ? *currentStateMap.at(previous.panelId)
                    : emptyState;
            if (predicate(previous, current)) {
                events.push_back({ kind, previous.panelId });
            }
        }
    };

    appendCategory(
        [](const UIEditorPanelHostState& previous, const UIEditorPanelHostState& current) {
            return previous.focused && !current.focused;
        },
        UIEditorPanelHostLifecycleEventKind::FocusLost);
    appendCategory(
        [](const UIEditorPanelHostState& previous, const UIEditorPanelHostState& current) {
            return previous.active && !current.active;
        },
        UIEditorPanelHostLifecycleEventKind::Deactivated);
    appendCategory(
        [](const UIEditorPanelHostState& previous, const UIEditorPanelHostState& current) {
            return previous.visible && !current.visible;
        },
        UIEditorPanelHostLifecycleEventKind::Hidden);
    appendCategory(
        [](const UIEditorPanelHostState& previous, const UIEditorPanelHostState& current) {
            return previous.attached && !current.attached;
        },
        UIEditorPanelHostLifecycleEventKind::Detached);
}

void AppendEnterEvents(
    std::vector<UIEditorPanelHostLifecycleEvent>& events,
    const std::vector<UIEditorPanelHostState>& currentStates,
    const HostStateMap& previousStateMap) {
    auto appendCategory = [&](auto predicate, UIEditorPanelHostLifecycleEventKind kind) {
        for (const UIEditorPanelHostState& current : currentStates) {
            const UIEditorPanelHostState emptyState = {};
            const UIEditorPanelHostState& previous =
                previousStateMap.contains(current.panelId)
                    ? *previousStateMap.at(current.panelId)
                    : emptyState;
            if (predicate(previous, current)) {
                events.push_back({ kind, current.panelId });
            }
        }
    };

    appendCategory(
        [](const UIEditorPanelHostState& previous, const UIEditorPanelHostState& current) {
            return !previous.attached && current.attached;
        },
        UIEditorPanelHostLifecycleEventKind::Attached);
    appendCategory(
        [](const UIEditorPanelHostState& previous, const UIEditorPanelHostState& current) {
            return !previous.visible && current.visible;
        },
        UIEditorPanelHostLifecycleEventKind::Shown);
    appendCategory(
        [](const UIEditorPanelHostState& previous, const UIEditorPanelHostState& current) {
            return !previous.active && current.active;
        },
        UIEditorPanelHostLifecycleEventKind::Activated);
    appendCategory(
        [](const UIEditorPanelHostState& previous, const UIEditorPanelHostState& current) {
            return !previous.focused && current.focused;
        },
        UIEditorPanelHostLifecycleEventKind::FocusGained);
}

std::vector<UIEditorPanelHostState> BuildResolvedPanelHostStates(
    const UIEditorPanelRegistry& panelRegistry,
    const UIEditorWorkspaceModel& workspace,
    const UIEditorWorkspaceSession& session,
    const UIEditorPanelHostLifecycleRequest& request) {
    const std::vector<UIEditorWorkspaceVisiblePanel> visiblePanels =
        CollectUIEditorWorkspaceVisiblePanels(workspace, session);
    std::unordered_set<std::string_view> visiblePanelIds = {};
    visiblePanelIds.reserve(visiblePanels.size());
    for (const UIEditorWorkspaceVisiblePanel& panel : visiblePanels) {
        visiblePanelIds.insert(panel.panelId);
    }

    std::vector<UIEditorPanelHostState> states = {};
    states.reserve(panelRegistry.panels.size());
    for (const UIEditorPanelDescriptor& descriptor : panelRegistry.panels) {
        if (!ContainsUIEditorWorkspacePanel(workspace, descriptor.panelId)) {
            continue;
        }

        const UIEditorPanelSessionState* sessionState =
            FindUIEditorPanelSessionState(session, descriptor.panelId);
        if (sessionState == nullptr) {
            continue;
        }

        UIEditorPanelHostState state = {};
        state.panelId = descriptor.panelId;
        state.attached = sessionState->open;
        state.visible = state.attached && visiblePanelIds.contains(state.panelId);
        state.active = state.visible && workspace.activePanelId == state.panelId;
        state.focused = state.active && request.focusedPanelId == state.panelId;
        states.push_back(std::move(state));
    }

    return states;
}

} // namespace

std::string_view GetUIEditorPanelHostLifecycleEventKindName(
    UIEditorPanelHostLifecycleEventKind kind) {
    switch (kind) {
    case UIEditorPanelHostLifecycleEventKind::Attached:
        return "Attached";
    case UIEditorPanelHostLifecycleEventKind::Detached:
        return "Detached";
    case UIEditorPanelHostLifecycleEventKind::Shown:
        return "Shown";
    case UIEditorPanelHostLifecycleEventKind::Hidden:
        return "Hidden";
    case UIEditorPanelHostLifecycleEventKind::Activated:
        return "Activated";
    case UIEditorPanelHostLifecycleEventKind::Deactivated:
        return "Deactivated";
    case UIEditorPanelHostLifecycleEventKind::FocusGained:
        return "FocusGained";
    case UIEditorPanelHostLifecycleEventKind::FocusLost:
        return "FocusLost";
    }

    return "Unknown";
}

const UIEditorPanelHostState* FindUIEditorPanelHostState(
    const UIEditorPanelHostLifecycleState& state,
    std::string_view panelId) {
    return FindHostState(state.panelStates, panelId);
}

const UIEditorPanelHostState* FindUIEditorPanelHostState(
    const UIEditorPanelHostLifecycleFrame& frame,
    std::string_view panelId) {
    return FindHostState(frame.panelStates, panelId);
}

UIEditorPanelHostLifecycleFrame UpdateUIEditorPanelHostLifecycle(
    UIEditorPanelHostLifecycleState& state,
    const UIEditorPanelRegistry& panelRegistry,
    const UIEditorWorkspaceModel& workspace,
    const UIEditorWorkspaceSession& session,
    const UIEditorPanelHostLifecycleRequest& request) {
    UIEditorPanelHostLifecycleFrame frame = {};
    frame.panelStates =
        BuildResolvedPanelHostStates(panelRegistry, workspace, session, request);

    const HostStateMap previousStateMap = BuildHostStateMap(state.panelStates);
    const HostStateMap currentStateMap = BuildHostStateMap(frame.panelStates);
    AppendLeaveEvents(frame.events, state.panelStates, currentStateMap);
    AppendEnterEvents(frame.events, frame.panelStates, previousStateMap);

    state.panelStates = frame.panelStates;
    return frame;
}

} // namespace XCEngine::UI::Editor