//! 下载页：**单列**版面的用例（列宽 ≤504，水平居中）。
//!
//! 这一页永远单列，理由不是「简单」，而是官方对「一次只做一件事」的入口（下载队列）的口径：
//! 内容是一串线性进度项，分栏没有第二个阅读对象。窗口变宽时**正文列不变宽**（撞行宽上限），
//! 多出来的宽度留白——这就是 M68「全宽单卡」的反面。
//!
//! 页头 1 个操作 + 空态 3 个快捷入口（12b §15.5：≤3）。

use iced::widget::{column, container, row};
use iced::{Alignment, Element, Length};

use unlucky_design::color::Role;
use unlucky_design::icons::IconKind;
use unlucky_design::spacing::Space;
use unlucky_design::typography::TypeRole;

use crate::theme::Ui;

use super::frame::{self, Header};
use super::layout::FrameMetrics;
use super::{Action, Message};

/// 整页。
pub fn view<'a>(ui: &'a Ui, metrics: FrameMetrics) -> Element<'a, Message> {
    let header = Header::new("Download")
        .subtitle("Versions, mod loaders and modpacks")
        .action(frame::text_action(
            ui,
            "Refresh sources",
            Action::RefreshSources,
        ));

    let empty = frame::empty_state(
        ui,
        IconKind::Download,
        "No downloads in progress",
        "Pick a version or drop a modpack file here. Sources are probed per region and can be pinned \
         in Settings → Downloads.",
        vec![
            frame::text_action(ui, "Browse versions", Action::BrowseVersions),
            frame::text_action(ui, "Import modpack", Action::ImportModpack),
            frame::text_action(ui, "Check sources", Action::CheckSources),
        ],
    );

    let body = frame::single_column(
        metrics,
        column![source_status(ui), empty]
            .spacing(ui.space(Space::X4))
            .width(Length::Fill)
            .height(Length::Fill),
    );

    frame::page(ui, metrics, header, body)
}

/// 来源状态行（12pt，`OnSurfaceVariant`）：说明这一页的数据从哪来，不是业务数据。
fn source_status<'a>(ui: &'a Ui) -> Element<'a, Message> {
    container(
        row![
            frame::glyph(
                IconKind::Check,
                ui.color(Role::Secondary),
                frame::ICON_SMALL_PX
            ),
            frame::text_role(
                ui,
                TypeRole::BodySmall,
                false,
                "3 sources healthy · BMCLAPI pinned by region · 2 min ago",
                ui.color(Role::OnSurfaceVariant),
            ),
        ]
        .spacing(ui.space(Space::X2))
        .align_y(Alignment::Center),
    )
    .width(Length::Fill)
    .into()
}

#[cfg(test)]
mod tests {
    use super::super::layout::{content_column_width, frame_metrics, measure_cap_px, PaneKit};

    /// 单列页：任何窗口宽度都不许出现第二列，正文列不许超过行宽上限。
    #[test]
    fn download_is_single_column_at_every_width() {
        for width in [600.0, 840.0, 900.0, 1180.0, 2400.0] {
            let metrics = frame_metrics(PaneKit::Single, width);
            assert!(metrics.secondary.is_none(), "{width} 宽下载页出现了第二列");
            assert!(metrics.column <= measure_cap_px() + f32::EPSILON);
            assert_eq!(metrics.column, content_column_width(width));
        }
    }

    /// 宽窗下多出来的宽度必须留白（不是把卡片拉宽）——1180 的正文列 < 可用宽度。
    #[test]
    fn extra_width_goes_to_margin_not_to_the_column() {
        let metrics = frame_metrics(PaneKit::Single, 1180.0);
        assert_eq!(metrics.column, measure_cap_px());
        assert!(
            metrics.available - metrics.column >= 400.0,
            "1180 宽下应留出大片留白（M68 的全宽卡就是没有这段留白）"
        );
    }
}