#include <XCEditor/Fields/UIEditorVector2FieldInteraction.h>

#include <XCEngine/Input/InputTypes.h>

#include <utility>

namespace XCEngine::UI::Editor {

namespace {

using ::XCEngine::Input::KeyCode;
using ::XCEngine::UI::UIInputEvent;
using ::XCEngine::UI::UIInputEventType;
using ::XCEngine::UI::UIPointerButton;
using ::XCEngine::UI::Text::HandleKeyDown;
using ::XCEngine::UI::Text::InsertCharacter;
using ::XCEngine::UI::Editor::Widgets::BuildUIEditorVector2FieldLayout;
using ::XCEngine::UI::Editor::Widgets::FormatUIEditorVector2FieldComponentValue;
using ::XCEngine::UI::Editor::Widgets::HitTestUIEditorVector2Field;
using ::XCEngine::UI::Editor::Widgets::IsUIEditorVector2FieldPointInside;
using ::XCEngine::UI::Editor::Widgets::NormalizeUIEditorVector2FieldComponentValue;
using ::XCEngine::UI::Editor::Widgets::TryParseUIEditorVector2FieldComponentValue;
using ::XCEngine::UI::Editor::Widgets::UIEditorVector2FieldHitTarget;
using ::XCEngine::UI::Editor::Widgets::UIEditorVector2FieldHitTargetKind;
using ::XCEngine::UI::Editor::Widgets::UIEditorVector2FieldInvalidComponentIndex;
using ::XCEngine::UI::Editor::Widgets::UIEditorVector2FieldLayout;
using ::XCEngine::UI::Editor::Widgets::UIEditorVector2FieldMetrics;
using ::XCEngine::UI::Editor::Widgets::UIEditorVector2FieldSpec;

bool ShouldUsePointerPosition(const UIInputEvent& event) {
    switch (event.type) {
    case UIInputEventType::PointerMove:
    case UIInputEventType::PointerEnter:
    case UIInputEventType::PointerButtonDown:
    case UIInputEventType::PointerButtonUp:
    case UIInputEventType::PointerWheel:
        return true;
    default:
        return false;
    }
}

std::size_t ResolveFallbackSelectedComponentIndex(
    const UIEditorVector2FieldInteractionState& state) {
    return state.vector2FieldState.selectedComponentIndex ==
            UIEditorVector2FieldInvalidComponentIndex
        ? 0u
        : state.vector2FieldState.selectedComponentIndex;
}

std::string BuildComponentEditFieldId(
    const UIEditorVector2FieldSpec& spec,
    std::size_t componentIndex) {
    return spec.fieldId + "." + std::to_string(componentIndex);
}

bool IsPermittedCharacter(
    const UIEditorVector2FieldSpec& spec,
    std::uint32_t character) {
    if (character >= static_cast<std::uint32_t>('0') &&
        character <= static_cast<std::uint32_t>('9')) {
        return true;
    }

    if (character == static_cast<std::uint32_t>('-') ||
        character == static_cast<std::uint32_t>('+')) {
        return true;
    }

    return !spec.integerMode && character == static_cast<std::uint32_t>('.');
}

void SyncDisplayTexts(
    UIEditorVector2FieldInteractionState& state,
    const UIEditorVector2FieldSpec& spec) {
    for (std::size_t componentIndex = 0u;
         componentIndex < state.vector2FieldState.displayTexts.size();
         ++componentIndex) {
        if (state.vector2FieldState.editing &&
            state.vector2FieldState.selectedComponentIndex == componentIndex) {
            continue;
        }

        state.vector2FieldState.displayTexts[componentIndex] =
            FormatUIEditorVector2FieldComponentValue(spec, componentIndex);
    }
}

void SyncHoverTarget(
    UIEditorVector2FieldInteractionState& state,
    const UIEditorVector2FieldLayout& layout) {
    if (!state.hasPointerPosition) {
        state.vector2FieldState.hoveredTarget = UIEditorVector2FieldHitTargetKind::None;
        state.vector2FieldState.hoveredComponentIndex = UIEditorVector2FieldInvalidComponentIndex;
        return;
    }

    const UIEditorVector2FieldHitTarget hitTarget =
        HitTestUIEditorVector2Field(layout, state.pointerPosition);
    state.vector2FieldState.hoveredTarget = hitTarget.kind;
    state.vector2FieldState.hoveredComponentIndex = hitTarget.componentIndex;
}

bool MoveSelection(
    UIEditorVector2FieldInteractionState& state,
    int direction,
    UIEditorVector2FieldInteractionResult& result) {
    const std::size_t before = ResolveFallbackSelectedComponentIndex(state);
    const std::size_t after =
        direction < 0
            ? (before == 0u ? 0u : before - 1u)
            : (before >= 1u ? 1u : before + 1u);
    state.vector2FieldState.selectedComponentIndex = after;
    result.selectionChanged = before != after;
    result.selectedComponentIndex = after;
    result.consumed = true;
    return true;
}

bool SelectComponent(
    UIEditorVector2FieldInteractionState& state,
    std::size_t componentIndex,
    UIEditorVector2FieldInteractionResult& result) {
    if (componentIndex >= 2u) {
        return false;
    }

    const std::size_t before = ResolveFallbackSelectedComponentIndex(state);
    state.vector2FieldState.selectedComponentIndex = componentIndex;
    result.selectionChanged = before != componentIndex;
    result.selectedComponentIndex = componentIndex;
    return true;
}

bool BeginEdit(
    UIEditorVector2FieldInteractionState& state,
    const UIEditorVector2FieldSpec& spec,
    std::size_t componentIndex,
    bool clearText) {
    if (spec.readOnly || componentIndex >= spec.values.size()) {
        return false;
    }

    const std::string baseline =
        FormatUIEditorVector2FieldComponentValue(spec, componentIndex);
    const std::string editFieldId =
        BuildComponentEditFieldId(spec, componentIndex);
    const bool changed = state.editModel.BeginEdit(editFieldId, baseline);
    if (!changed &&
        state.editModel.HasActiveEdit() &&
        state.editModel.GetActiveFieldId() != editFieldId) {
        return false;
    }
    if (!changed &&
        state.vector2FieldState.editing &&
        state.vector2FieldState.selectedComponentIndex == componentIndex) {
        return false;
    }

    state.vector2FieldState.selectedComponentIndex = componentIndex;
    state.vector2FieldState.editing = true;
    state.textInputState.value = clearText ? std::string() : baseline;
    state.textInputState.caret = state.textInputState.value.size();
    state.editModel.UpdateStagedValue(state.textInputState.value);
    state.vector2FieldState.displayTexts[componentIndex] = state.textInputState.value;
    return true;
}

bool CommitEdit(
    UIEditorVector2FieldInteractionState& state,
    UIEditorVector2FieldSpec& spec,
    UIEditorVector2FieldInteractionResult& result) {
    if (!state.vector2FieldState.editing ||
        !state.editModel.HasActiveEdit() ||
        state.vector2FieldState.selectedComponentIndex >= spec.values.size()) {
        return false;
    }

    const std::size_t componentIndex = state.vector2FieldState.selectedComponentIndex;
    double parsedValue = spec.values[componentIndex];
    if (!TryParseUIEditorVector2FieldComponentValue(
            spec,
            state.textInputState.value,
            parsedValue)) {
        result.consumed = true;
        result.editCommitRejected = true;
        return false;
    }

    result.valuesBefore = spec.values;
    spec.values[componentIndex] = NormalizeUIEditorVector2FieldComponentValue(spec, parsedValue);
    result.valuesAfter = spec.values;
    result.valueChanged = result.valuesBefore != result.valuesAfter;
    result.editCommitted = true;
    result.consumed = true;
    result.changedComponentIndex = componentIndex;
    result.selectedComponentIndex = componentIndex;
    result.committedText =
        FormatUIEditorVector2FieldComponentValue(spec, componentIndex);

    state.editModel.CommitEdit();
    state.textInputState = {};
    state.vector2FieldState.editing = false;
    state.vector2FieldState.displayTexts[componentIndex] = result.committedText;
    return true;
}

bool CancelEdit(
    UIEditorVector2FieldInteractionState& state,
    const UIEditorVector2FieldSpec& spec,
    UIEditorVector2FieldInteractionResult& result) {
    if (!state.vector2FieldState.editing ||
        !state.editModel.HasActiveEdit() ||
        state.vector2FieldState.selectedComponentIndex >= spec.values.size()) {
        return false;
    }

    const std::size_t componentIndex = state.vector2FieldState.selectedComponentIndex;
    state.editModel.CancelEdit();
    state.textInputState = {};
    state.vector2FieldState.editing = false;
    state.vector2FieldState.displayTexts[componentIndex] =
        FormatUIEditorVector2FieldComponentValue(spec, componentIndex);
    result.consumed = true;
    result.editCanceled = true;
    result.valuesBefore = spec.values;
    result.valuesAfter = spec.values;
    result.selectedComponentIndex = componentIndex;
    return true;
}

bool ApplyStep(
    UIEditorVector2FieldInteractionState& state,
    UIEditorVector2FieldSpec& spec,
    double direction,
    bool snapToEdge,
    UIEditorVector2FieldInteractionResult& result) {
    if (spec.readOnly) {
        return false;
    }

    const std::size_t componentIndex = ResolveFallbackSelectedComponentIndex(state);
    state.vector2FieldState.selectedComponentIndex = componentIndex;

    if (state.vector2FieldState.editing &&
        !CommitEdit(state, spec, result)) {
        return result.editCommitRejected;
    }

    result.valuesBefore = spec.values;
    if (snapToEdge) {
        spec.values[componentIndex] =
            direction < 0.0
                ? NormalizeUIEditorVector2FieldComponentValue(spec, spec.minValue)
                : NormalizeUIEditorVector2FieldComponentValue(spec, spec.maxValue);
    } else {
        const double step = spec.step == 0.0 ? 1.0 : spec.step;
        spec.values[componentIndex] = NormalizeUIEditorVector2FieldComponentValue(
            spec,
            spec.values[componentIndex] + step * direction);
        result.stepDelta = step * direction;
    }

    result.valuesAfter = spec.values;
    result.stepApplied = true;
    result.valueChanged = result.valuesBefore != result.valuesAfter || result.valueChanged;
    result.changedComponentIndex = componentIndex;
    result.selectedComponentIndex = componentIndex;
    result.consumed = true;
    state.vector2FieldState.displayTexts[componentIndex] =
        FormatUIEditorVector2FieldComponentValue(spec, componentIndex);
    return true;
}

} // namespace

UIEditorVector2FieldInteractionFrame UpdateUIEditorVector2FieldInteraction(
    UIEditorVector2FieldInteractionState& state,
    UIEditorVector2FieldSpec& spec,
    const ::XCEngine::UI::UIRect& bounds,
    const std::vector<UIInputEvent>& inputEvents,
    const UIEditorVector2FieldMetrics& metrics) {
    UIEditorVector2FieldLayout layout = BuildUIEditorVector2FieldLayout(bounds, spec, metrics);
    SyncDisplayTexts(state, spec);
    SyncHoverTarget(state, layout);

    UIEditorVector2FieldInteractionResult interactionResult = {};
    interactionResult.selectedComponentIndex = state.vector2FieldState.selectedComponentIndex;
    for (const UIInputEvent& event : inputEvents) {
        if (ShouldUsePointerPosition(event)) {
            state.pointerPosition = event.position;
            state.hasPointerPosition = true;
        } else if (event.type == UIInputEventType::PointerLeave) {
            state.hasPointerPosition = false;
        }

        UIEditorVector2FieldInteractionResult eventResult = {};
        eventResult.selectedComponentIndex = state.vector2FieldState.selectedComponentIndex;
        switch (event.type) {
        case UIInputEventType::FocusGained:
            eventResult.focusChanged = !state.vector2FieldState.focused;
            state.vector2FieldState.focused = true;
            if (state.vector2FieldState.selectedComponentIndex ==
                UIEditorVector2FieldInvalidComponentIndex) {
                state.vector2FieldState.selectedComponentIndex = 0u;
            }
            eventResult.selectedComponentIndex = state.vector2FieldState.selectedComponentIndex;
            break;

        case UIInputEventType::FocusLost:
            eventResult.focusChanged = state.vector2FieldState.focused;
            state.vector2FieldState.focused = false;
            state.vector2FieldState.activeTarget = UIEditorVector2FieldHitTargetKind::None;
            state.vector2FieldState.activeComponentIndex = UIEditorVector2FieldInvalidComponentIndex;
            state.hasPointerPosition = false;
            if (state.vector2FieldState.editing) {
                CommitEdit(state, spec, eventResult);
                if (eventResult.editCommitRejected) {
                    CancelEdit(state, spec, eventResult);
                }
            }
            break;

        case UIInputEventType::PointerMove:
        case UIInputEventType::PointerEnter:
        case UIInputEventType::PointerLeave:
            break;

        case UIInputEventType::PointerButtonDown: {
            const UIEditorVector2FieldHitTarget hitTarget =
                state.hasPointerPosition
                    ? HitTestUIEditorVector2Field(layout, state.pointerPosition)
                    : UIEditorVector2FieldHitTarget {};
            eventResult.hitTarget = hitTarget;

            if (event.pointerButton != UIPointerButton::Left) {
                break;
            }

            const bool insideField =
                state.hasPointerPosition &&
                IsUIEditorVector2FieldPointInside(layout.bounds, state.pointerPosition);
            if (insideField) {
                eventResult.focusChanged = !state.vector2FieldState.focused;
                state.vector2FieldState.focused = true;
                state.vector2FieldState.activeTarget = hitTarget.kind == UIEditorVector2FieldHitTargetKind::None
                    ? UIEditorVector2FieldHitTargetKind::Row
                    : hitTarget.kind;
                state.vector2FieldState.activeComponentIndex = hitTarget.componentIndex;
                if (hitTarget.kind == UIEditorVector2FieldHitTargetKind::Component) {
                    SelectComponent(state, hitTarget.componentIndex, eventResult);
                } else if (state.vector2FieldState.selectedComponentIndex ==
                           UIEditorVector2FieldInvalidComponentIndex) {
                    state.vector2FieldState.selectedComponentIndex = 0u;
                    eventResult.selectedComponentIndex = 0u;
                }
                eventResult.consumed = true;
            } else {
                if (state.vector2FieldState.editing) {
                    CommitEdit(state, spec, eventResult);
                    if (!eventResult.editCommitRejected) {
                        eventResult.focusChanged = state.vector2FieldState.focused;
                        state.vector2FieldState.focused = false;
                    }
                } else if (state.vector2FieldState.focused) {
                    eventResult.focusChanged = true;
                    state.vector2FieldState.focused = false;
                }
                state.vector2FieldState.activeTarget = UIEditorVector2FieldHitTargetKind::None;
                state.vector2FieldState.activeComponentIndex = UIEditorVector2FieldInvalidComponentIndex;
            }
            break;
        }

        case UIInputEventType::PointerButtonUp: {
            const UIEditorVector2FieldHitTarget hitTarget =
                state.hasPointerPosition
                    ? HitTestUIEditorVector2Field(layout, state.pointerPosition)
                    : UIEditorVector2FieldHitTarget {};
            eventResult.hitTarget = hitTarget;

            if (event.pointerButton == UIPointerButton::Left) {
                const UIEditorVector2FieldHitTargetKind activeTarget = state.vector2FieldState.activeTarget;
                const std::size_t activeComponentIndex = state.vector2FieldState.activeComponentIndex;
                state.vector2FieldState.activeTarget = UIEditorVector2FieldHitTargetKind::None;
                state.vector2FieldState.activeComponentIndex = UIEditorVector2FieldInvalidComponentIndex;

                if (activeTarget == UIEditorVector2FieldHitTargetKind::Component &&
                    hitTarget.kind == UIEditorVector2FieldHitTargetKind::Component &&
                    activeComponentIndex == hitTarget.componentIndex) {
                    SelectComponent(state, hitTarget.componentIndex, eventResult);
                    if (!state.vector2FieldState.editing) {
                        eventResult.editStarted =
                            BeginEdit(state, spec, hitTarget.componentIndex, false);
                    }
                    eventResult.consumed = true;
                } else if (hitTarget.kind == UIEditorVector2FieldHitTargetKind::Row) {
                    eventResult.consumed = true;
                }
            }
            break;
        }

        case UIInputEventType::KeyDown:
            if (!state.vector2FieldState.focused) {
                break;
            }

            if (state.vector2FieldState.editing) {
                if (event.keyCode == static_cast<std::int32_t>(KeyCode::Escape)) {
                    CancelEdit(state, spec, eventResult);
                    break;
                }

                if (event.keyCode == static_cast<std::int32_t>(KeyCode::Tab)) {
                    if (CommitEdit(state, spec, eventResult)) {
                        MoveSelection(
                            state,
                            event.modifiers.shift ? -1 : 1,
                            eventResult);
                    }
                    eventResult.consumed = true;
                    break;
                }

                const auto textResult =
                    HandleKeyDown(state.textInputState, event.keyCode, event.modifiers);
                if (textResult.handled) {
                    state.editModel.UpdateStagedValue(state.textInputState.value);
                    state.vector2FieldState.displayTexts[state.vector2FieldState.selectedComponentIndex] =
                        state.textInputState.value;
                    eventResult.consumed = true;
                    eventResult.selectedComponentIndex = state.vector2FieldState.selectedComponentIndex;
                    if (textResult.submitRequested) {
                        CommitEdit(state, spec, eventResult);
                    }
                    break;
                }
            } else {
                switch (static_cast<KeyCode>(event.keyCode)) {
                case KeyCode::Left:
                    MoveSelection(state, -1, eventResult);
                    break;

                case KeyCode::Right:
                case KeyCode::Tab:
                    MoveSelection(
                        state,
                        static_cast<KeyCode>(event.keyCode) == KeyCode::Tab && event.modifiers.shift ? -1 : 1,
                        eventResult);
                    break;

                case KeyCode::Up:
                    ApplyStep(state, spec, 1.0, false, eventResult);
                    break;

                case KeyCode::Down:
                    ApplyStep(state, spec, -1.0, false, eventResult);
                    break;

                case KeyCode::Home:
                    ApplyStep(state, spec, -1.0, true, eventResult);
                    break;

                case KeyCode::End:
                    ApplyStep(state, spec, 1.0, true, eventResult);
                    break;

                case KeyCode::Enter:
                    eventResult.selectedComponentIndex = ResolveFallbackSelectedComponentIndex(state);
                    eventResult.editStarted = BeginEdit(
                        state,
                        spec,
                        eventResult.selectedComponentIndex,
                        false);
                    eventResult.consumed = eventResult.editStarted;
                    break;

                default:
                    break;
                }
            }
            break;

        case UIInputEventType::Character:
            if (!state.vector2FieldState.focused ||
                spec.readOnly ||
                event.modifiers.control ||
                event.modifiers.alt ||
                event.modifiers.super ||
                !IsPermittedCharacter(spec, event.character)) {
                break;
            }

            if (state.vector2FieldState.selectedComponentIndex ==
                UIEditorVector2FieldInvalidComponentIndex) {
                state.vector2FieldState.selectedComponentIndex = 0u;
            }
            eventResult.selectedComponentIndex = state.vector2FieldState.selectedComponentIndex;

            if (!state.vector2FieldState.editing) {
                eventResult.editStarted = BeginEdit(
                    state,
                    spec,
                    state.vector2FieldState.selectedComponentIndex,
                    true);
            }

            if (InsertCharacter(state.textInputState, event.character)) {
                state.editModel.UpdateStagedValue(state.textInputState.value);
                state.vector2FieldState.displayTexts[state.vector2FieldState.selectedComponentIndex] =
                    state.textInputState.value;
                eventResult.consumed = true;
            }
            break;

        default:
            break;
        }

        layout = BuildUIEditorVector2FieldLayout(bounds, spec, metrics);
        SyncDisplayTexts(state, spec);
        SyncHoverTarget(state, layout);
        if (eventResult.hitTarget.kind == UIEditorVector2FieldHitTargetKind::None &&
            state.hasPointerPosition) {
            eventResult.hitTarget = HitTestUIEditorVector2Field(layout, state.pointerPosition);
        }
        if (eventResult.selectedComponentIndex == UIEditorVector2FieldInvalidComponentIndex) {
            eventResult.selectedComponentIndex = state.vector2FieldState.selectedComponentIndex;
        }

        if (eventResult.consumed ||
            eventResult.focusChanged ||
            eventResult.valueChanged ||
            eventResult.stepApplied ||
            eventResult.selectionChanged ||
            eventResult.editStarted ||
            eventResult.editCommitted ||
            eventResult.editCommitRejected ||
            eventResult.editCanceled ||
            eventResult.hitTarget.kind != UIEditorVector2FieldHitTargetKind::None) {
            interactionResult = std::move(eventResult);
        }
    }

    layout = BuildUIEditorVector2FieldLayout(bounds, spec, metrics);
    SyncDisplayTexts(state, spec);
    SyncHoverTarget(state, layout);
    if (interactionResult.hitTarget.kind == UIEditorVector2FieldHitTargetKind::None &&
        state.hasPointerPosition) {
        interactionResult.hitTarget = HitTestUIEditorVector2Field(layout, state.pointerPosition);
    }
    if (interactionResult.selectedComponentIndex == UIEditorVector2FieldInvalidComponentIndex) {
        interactionResult.selectedComponentIndex = state.vector2FieldState.selectedComponentIndex;
    }

    return {
        std::move(layout),
        std::move(interactionResult)
    };
}

} // namespace XCEngine::UI::Editor