//! 首屏骨架（**不做业务**）：自绘标题栏 + 左侧导航轨 + 内容区（页头 + 一张卡片）。
//!
//! ## 与参考判据的对应（`research/12b-component-fidelity.md`）
//!
//! | 部件 | 参考 | 令牌落点 |
//! |---|---|---|
//! | 标题栏高度 | 16.2 桌面标题栏 **40**（登记偏离） | `LM.titlebar_height = 48`（M63 §1.4/R13 桌面档，令牌优先） |
//! | 标题栏按钮 | 16.5 图标 **24** | `IconSize::Toolbar` + `LM.titlebar_button_width = 46` |
//! | 页头 | 16.1 官方 AppBar **64**；本项目 **56** | `LM.page_header_height = 56`（已有偏离登记） |
//! | 卡片 | 3.x Outlined：**Medium(12)**、L0、`OutlineVariant` 1px、`SurfaceContainerLow` | `Component::OutlinedCard.spec()` + `STROKE_PX` |
//! | 字级 | 16.4 标题 `TitleLarge`；卡片 `TitleMedium` / `BodySmall` | `Ui::style` / `Ui::emphasized` |
//!
//! 导航轨在 [`nav`] 子模块里（12b §5 的判据表也在那边）。
//!
//! 一屏只出现 4 档字号（22 / 16 / 14 / 12），且**没有实心 accent**（rubric K2：一屏最多一个实心
//! Primary，骨架期一个都不要）。阴影只给浮层，骨架里没有浮层，所以**全屏零阴影**（rubric K3）。

mod nav;

pub use nav::NavItem;

use iced::widget::text::LineHeight;
use iced::widget::{button, column, container, mouse_area, row, space, text};
use iced::{mouse, Alignment, Background, Border, Color, Element, Length, Padding, Pixels, Shadow};
use iced::{window::Direction, Theme as IcedTheme};

use unlucky_design::color::{Role, StateLayer};
use unlucky_design::component_map::Component;
use unlucky_design::elevation::MaterialLayer;
use unlucky_design::icons::IconKind;
use unlucky_design::spacing::Space;
use unlucky_design::typography::TypeRole;

use crate::app::Message;
use crate::icons;
use crate::theme::Ui;

/// 整棵树。
pub fn view<'a>(
    ui: &'a Ui,
    selected: NavItem,
    app_title: &'a str,
    page_title: &'a str,
    body: &'a str,
) -> Element<'a, Message> {
    let work_area = column![
        titlebar(ui, app_title),
        row![nav::rail(ui, selected), content(ui, page_title, body)]
            .width(Length::Fill)
            .height(Length::Fill),
    ]
    .width(Length::Fill)
    .height(Length::Fill);

    // 无边框窗口没有系统缩放边框 → 自己给两条热区（东/南）。西/北边见模块文档的已知缺口。
    let thickness = Length::Fixed(ui.space(Space::X1));

    let shell = column![
        row![
            work_area,
            resize_edge(
                Direction::East,
                (thickness, Length::Fill),
                mouse::Interaction::ResizingHorizontally,
            ),
        ]
        .width(Length::Fill)
        .height(Length::Fill),
        resize_edge(
            Direction::South,
            (Length::Fill, thickness),
            mouse::Interaction::ResizingVertically,
        ),
    ]
    .width(Length::Fill)
    .height(Length::Fill);

    container(shell)
        .width(Length::Fill)
        .height(Length::Fill)
        .style(|_theme| filled(ui.layer(MaterialLayer::Canvas)))
        .into()
}

/// 窗口缩放热区（透明；玻璃/底色由根容器提供）。
///
/// 拖动时调 `window::drag_resize(id, direction)`——Windows/X11 走 winit 原生实现，
/// **macOS 返回 `NotSupported`**（M60 Q4），如实登记在交接文档里。
fn resize_edge<'a>(
    direction: Direction,
    size: (Length, Length),
    interaction: mouse::Interaction,
) -> Element<'a, Message> {
    let (width, height) = size;

    mouse_area(container(space::horizontal()).width(width).height(height))
        .interaction(interaction)
        .on_press(Message::ResizeStart(direction))
        .into()
}

// ---------------------------------------------------------------- 标题栏

fn titlebar<'a>(ui: &'a Ui, title: &'a str) -> Element<'a, Message> {
    let metrics = ui.metrics();

    // 拖动热区：从窗口左缘到第一个按钮（按钮自己不能被拖区吞掉，所以只包左侧一段）
    let drag_area = mouse_area(
        container(label(
            ui,
            TypeRole::LabelLarge,
            true,
            title,
            ui.color(Role::OnSurface),
        ))
        .width(Length::Fill)
        .height(Length::Fill)
        .align_y(Alignment::Center)
        .padding(Padding::from([0.0, ui.space(Space::X4)])),
    )
    .on_press(Message::DragWindow);

    let bar = row![
        drag_area,
        caption(ui, IconKind::Minimize, Message::Minimize),
        caption(ui, IconKind::Maximize, Message::ToggleMaximize),
        caption(ui, IconKind::Close, Message::Close),
    ]
    .width(Length::Fill)
    .height(metrics.titlebar_height)
    .align_y(Alignment::Center);

    container(bar)
        .width(Length::Fill)
        .height(metrics.titlebar_height)
        .style(|_theme| filled(ui.layer(MaterialLayer::Canvas)))
        .into()
}

/// 标题栏按钮（自绘最小化/最大化/关闭）。
fn caption<'a>(ui: &'a Ui, kind: IconKind, message: Message) -> Element<'a, Message> {
    let metrics = ui.metrics();

    button(icons::view::<Message>(
        kind,
        ui.color(Role::OnSurfaceVariant),
    ))
    .width(metrics.titlebar_button_width)
    .height(metrics.titlebar_height)
    .padding(0)
    .style(move |_theme: &IcedTheme, status| {
        let background = match status {
            button::Status::Hovered => Some(Background::Color(ui.state_over(
                StateLayer::Hover,
                Role::OnSurface,
                Role::Surface,
            ))),
            button::Status::Pressed => Some(Background::Color(ui.state_over(
                StateLayer::Pressed,
                Role::OnSurface,
                Role::Surface,
            ))),
            button::Status::Active | button::Status::Disabled => None,
        };

        button::Style {
            background,
            text_color: ui.color(Role::OnSurfaceVariant),
            border: Border::default(),
            shadow: Shadow::default(),
            snap: true,
        }
    })
    .on_press(message)
    .into()
}

// ---------------------------------------------------------------- 内容区

fn content<'a>(ui: &'a Ui, title: &'a str, body: &'a str) -> Element<'a, Message> {
    let metrics = ui.metrics();
    // 卡片档位由组件表决定（圆角/字级），组件层不自己挑
    let card_spec = Component::OutlinedCard.spec();
    let body_role = card_spec.support.unwrap_or(card_spec.text);

    let header = container(label(
        ui,
        TypeRole::TitleLarge,
        true,
        title,
        ui.color(Role::OnSurface),
    ))
    .width(Length::Fill)
    .height(metrics.page_header_height)
    .align_y(Alignment::Center)
    .padding(Padding::from([0.0, ui.space(Space::X6)]));

    let card = container(
        column![
            label(
                ui,
                card_spec.text,
                true,
                "Shell ready",
                ui.color(Role::OnSurface),
            ),
            label(ui, body_role, false, body, ui.color(Role::OnSurfaceVariant)),
        ]
        .spacing(ui.space(Space::X2)),
    )
    .width(Length::Fill)
    .padding(metrics.card_padding)
    .style(move |_theme| container::Style {
        background: Some(Background::Color(ui.layer(MaterialLayer::Card))),
        border: ui.outlined(card_spec.shape),
        ..container::Style::default()
    });

    let body_area = container(card)
        .width(Length::Fill)
        .height(Length::Fill)
        .padding(ui.space(Space::X6))
        .align_y(Alignment::Start);

    column![header, body_area]
        .width(Length::Fill)
        .height(Length::Fill)
        .into()
}

// ---------------------------------------------------------------- 小工具

/// 一个文字元素：字号/行高/字重全部来自令牌排版档。
pub(super) fn label<'a>(
    ui: &'a Ui,
    role: TypeRole,
    emphasized: bool,
    content: &'a str,
    color: Color,
) -> Element<'a, Message> {
    let style = if emphasized {
        ui.emphasized(role)
    } else {
        ui.style(role)
    };

    text(content)
        .size(style.size_px)
        .line_height(LineHeight::Absolute(Pixels(style.line_height_px)))
        .font(ui.font_of(style))
        .color(color)
        .into()
}

pub(super) fn filled(color: Color) -> container::Style {
    container::Style {
        background: Some(Background::Color(color)),
        ..container::Style::default()
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use unlucky_design::color::SchemeFlavor;
    use unlucky_design::typography::Platform;

    use crate::theme::Families;

    fn ui(flavor: SchemeFlavor) -> Ui {
        Ui::with_platform(
            flavor,
            Platform::Windows,
            Families {
                text: "Segoe UI",
                display: "Segoe UI",
                mono: "Consolas",
            },
        )
    }

    #[test]
    fn a_screen_only_uses_four_text_sizes_at_most() {
        let ui = ui(SchemeFlavor::Dark);
        let card = Component::OutlinedCard.spec();
        let sizes = [
            ui.emphasized(TypeRole::TitleLarge).size_px,
            ui.emphasized(TypeRole::LabelLarge).size_px,
            ui.emphasized(card.text).size_px,
            ui.style(card.support.unwrap_or(card.text)).size_px,
            ui.style(TypeRole::LabelMedium).size_px,
        ];
        let mut unique = sizes.to_vec();
        unique.sort_by(f32::total_cmp);
        unique.dedup();
        assert!(
            unique.len() <= 4,
            "rubric D4：一屏字号档 ≤4（实际 {} 档 {unique:?}）",
            unique.len()
        );
        assert!(unique[0] >= 12.0, "最小档不下 12px（caption ≥11）");
        assert!(unique[unique.len() - 1] <= 28.0, "列表页标题不得 >28px");
    }

    #[test]
    fn flavor_slug_is_stable_for_filenames() {
        assert_eq!(crate::shot::flavor_slug(&ui(SchemeFlavor::Light)), "light");
        assert_eq!(crate::shot::flavor_slug(&ui(SchemeFlavor::Dark)), "dark");
    }
}