#include <XCEditor/Fields/UIEditorTextFieldInteraction.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::BuildUIEditorTextFieldLayout;
using ::XCEngine::UI::Editor::Widgets::HitTestUIEditorTextField;
using ::XCEngine::UI::Editor::Widgets::IsUIEditorTextFieldPointInside;
using ::XCEngine::UI::Editor::Widgets::UIEditorTextFieldHitTarget;
using ::XCEngine::UI::Editor::Widgets::UIEditorTextFieldHitTargetKind;
using ::XCEngine::UI::Editor::Widgets::UIEditorTextFieldLayout;
using ::XCEngine::UI::Editor::Widgets::UIEditorTextFieldMetrics;
using ::XCEngine::UI::Editor::Widgets::UIEditorTextFieldSpec;

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;
    }
}

void SyncDisplayText(
    UIEditorTextFieldInteractionState& state,
    const UIEditorTextFieldSpec& spec) {
    if (!state.textFieldState.editing) {
        state.textFieldState.displayText = spec.value;
    }
}

void SyncHoverTarget(
    UIEditorTextFieldInteractionState& state,
    const UIEditorTextFieldLayout& layout) {
    if (!state.hasPointerPosition) {
        state.textFieldState.hoveredTarget = UIEditorTextFieldHitTargetKind::None;
        return;
    }

    state.textFieldState.hoveredTarget =
        HitTestUIEditorTextField(layout, state.pointerPosition).kind;
}

bool BeginEdit(
    UIEditorTextFieldInteractionState& state,
    const UIEditorTextFieldSpec& spec,
    bool clearText) {
    if (spec.readOnly) {
        return false;
    }

    const bool changed = state.editModel.BeginEdit(spec.fieldId, spec.value);
    if (!changed &&
        state.editModel.HasActiveEdit() &&
        state.editModel.GetActiveFieldId() != spec.fieldId) {
        return false;
    }
    if (!changed && state.textFieldState.editing) {
        return false;
    }

    state.textFieldState.editing = true;
    state.textInputState.value = clearText ? std::string() : spec.value;
    state.textInputState.caret = state.textInputState.value.size();
    state.editModel.UpdateStagedValue(state.textInputState.value);
    state.textFieldState.displayText = state.textInputState.value;
    return true;
}

bool CommitEdit(
    UIEditorTextFieldInteractionState& state,
    UIEditorTextFieldSpec& spec,
    UIEditorTextFieldInteractionResult& result) {
    if (!state.textFieldState.editing || !state.editModel.HasActiveEdit()) {
        return false;
    }

    result.valueBefore = spec.value;
    spec.value = state.textInputState.value;
    result.valueAfter = spec.value;
    result.valueChanged = result.valueBefore != result.valueAfter;
    result.editCommitted = true;
    result.consumed = true;
    result.committedText = spec.value;

    state.editModel.CommitEdit();
    state.textInputState = {};
    state.textFieldState.editing = false;
    state.textFieldState.displayText = spec.value;
    return true;
}

bool CancelEdit(
    UIEditorTextFieldInteractionState& state,
    const UIEditorTextFieldSpec& spec,
    UIEditorTextFieldInteractionResult& result) {
    if (!state.textFieldState.editing || !state.editModel.HasActiveEdit()) {
        return false;
    }

    state.editModel.CancelEdit();
    state.textInputState = {};
    state.textFieldState.editing = false;
    state.textFieldState.displayText = spec.value;
    result.consumed = true;
    result.editCanceled = true;
    result.valueBefore = spec.value;
    result.valueAfter = spec.value;
    return true;
}

} // namespace

UIEditorTextFieldInteractionFrame UpdateUIEditorTextFieldInteraction(
    UIEditorTextFieldInteractionState& state,
    UIEditorTextFieldSpec& spec,
    const ::XCEngine::UI::UIRect& bounds,
    const std::vector<UIInputEvent>& inputEvents,
    const UIEditorTextFieldMetrics& metrics) {
    UIEditorTextFieldLayout layout = BuildUIEditorTextFieldLayout(bounds, spec, metrics);
    SyncDisplayText(state, spec);
    SyncHoverTarget(state, layout);

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

        UIEditorTextFieldInteractionResult eventResult = {};
        switch (event.type) {
        case UIInputEventType::FocusGained:
            eventResult.focusChanged = !state.textFieldState.focused;
            state.textFieldState.focused = true;
            break;

        case UIInputEventType::FocusLost:
            eventResult.focusChanged = state.textFieldState.focused;
            state.textFieldState.focused = false;
            state.textFieldState.activeTarget = UIEditorTextFieldHitTargetKind::None;
            state.hasPointerPosition = false;
            if (state.textFieldState.editing) {
                CommitEdit(state, spec, eventResult);
            }
            break;

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

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

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

            const bool insideField =
                state.hasPointerPosition &&
                IsUIEditorTextFieldPointInside(layout.bounds, state.pointerPosition);
            if (insideField) {
                eventResult.focusChanged = !state.textFieldState.focused;
                state.textFieldState.focused = true;
                state.textFieldState.activeTarget =
                    hitTarget.kind == UIEditorTextFieldHitTargetKind::None
                        ? UIEditorTextFieldHitTargetKind::Row
                        : hitTarget.kind;
                eventResult.consumed = true;
            } else {
                if (state.textFieldState.editing) {
                    CommitEdit(state, spec, eventResult);
                    eventResult.focusChanged = state.textFieldState.focused;
                    state.textFieldState.focused = false;
                } else if (state.textFieldState.focused) {
                    eventResult.focusChanged = true;
                    state.textFieldState.focused = false;
                }
                state.textFieldState.activeTarget = UIEditorTextFieldHitTargetKind::None;
            }
            break;
        }

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

            if (event.pointerButton == UIPointerButton::Left) {
                const UIEditorTextFieldHitTargetKind activeTarget = state.textFieldState.activeTarget;
                state.textFieldState.activeTarget = UIEditorTextFieldHitTargetKind::None;

                if (activeTarget == UIEditorTextFieldHitTargetKind::ValueBox &&
                    hitTarget.kind == UIEditorTextFieldHitTargetKind::ValueBox) {
                    if (!state.textFieldState.editing) {
                        eventResult.editStarted = BeginEdit(state, spec, false);
                    }
                    eventResult.consumed = true;
                } else if (hitTarget.kind == UIEditorTextFieldHitTargetKind::Row) {
                    eventResult.consumed = true;
                }
            }
            break;
        }

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

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

                const auto textResult =
                    HandleKeyDown(state.textInputState, event.keyCode, event.modifiers);
                if (textResult.handled) {
                    state.editModel.UpdateStagedValue(state.textInputState.value);
                    state.textFieldState.displayText = state.textInputState.value;
                    eventResult.consumed = true;
                    eventResult.valueBefore = spec.value;
                    eventResult.valueAfter = spec.value;
                    if (textResult.submitRequested) {
                        CommitEdit(state, spec, eventResult);
                    }
                }
            } else if (event.keyCode == static_cast<std::int32_t>(KeyCode::Enter)) {
                eventResult.editStarted = BeginEdit(state, spec, false);
                eventResult.consumed = eventResult.editStarted;
            }
            break;

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

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

            if (InsertCharacter(state.textInputState, event.character)) {
                state.editModel.UpdateStagedValue(state.textInputState.value);
                state.textFieldState.displayText = state.textInputState.value;
                eventResult.consumed = true;
            }
            break;

        default:
            break;
        }

        layout = BuildUIEditorTextFieldLayout(bounds, spec, metrics);
        SyncDisplayText(state, spec);
        SyncHoverTarget(state, layout);
        if (eventResult.hitTarget.kind == UIEditorTextFieldHitTargetKind::None &&
            state.hasPointerPosition) {
            eventResult.hitTarget = HitTestUIEditorTextField(layout, state.pointerPosition);
        }

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

    layout = BuildUIEditorTextFieldLayout(bounds, spec, metrics);
    SyncDisplayText(state, spec);
    SyncHoverTarget(state, layout);
    if (interactionResult.hitTarget.kind == UIEditorTextFieldHitTargetKind::None &&
        state.hasPointerPosition) {
        interactionResult.hitTarget = HitTestUIEditorTextField(layout, state.pointerPosition);
    }

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

} // namespace XCEngine::UI::Editor