use crate::diff_render::display_path_for;
use crate::key_hint;
use crate::line_truncation::truncate_line_with_ellipsis_if_overflow;
use crate::render::Insets;
use crate::render::RectExt as _;
use crate::selection_list::selection_option_row_with_dim;
use crate::style::accent_style;
use crate::tui::FrameRequester;
use crate::tui::Tui;
use crate::tui::TuiEvent;
use codex_app_server_protocol::ExternalAgentConfigMigrationItem;
use codex_app_server_protocol::PluginsMigration;
use crossterm::event::KeyCode;
use crossterm::event::KeyEvent;
use crossterm::event::KeyEventKind;
use crossterm::event::KeyModifiers;
use ratatui::buffer::Buffer;
use ratatui::layout::Constraint;
use ratatui::layout::Layout;
use ratatui::layout::Rect;
use ratatui::prelude::Stylize as _;
use ratatui::text::Line;
use ratatui::widgets::Clear;
use ratatui::widgets::Paragraph;
use ratatui::widgets::Widget;
use ratatui::widgets::WidgetRef;
use ratatui::widgets::Wrap;
use tokio_stream::StreamExt;

#[derive(Clone, Debug, PartialEq, Eq)]
pub(crate) enum ExternalAgentConfigMigrationOutcome {
    Proceed(Vec<ExternalAgentConfigMigrationItem>),
    Skip,
    SkipForever,
    Exit,
}

#[derive(Clone, Copy, Debug, PartialEq, Eq)]
enum FocusArea {
    Items,
    Actions,
}

#[derive(Clone, Copy, Debug, PartialEq, Eq)]
enum ActionMenuOption {
    Proceed,
    Skip,
    SkipForever,
}

impl ActionMenuOption {
    fn label(self) -> &'static str {
        match self {
            Self::Proceed => "Proceed with selected",
            Self::Skip => "Skip for now",
            Self::SkipForever => "Don't ask again",
        }
    }

    fn previous(self) -> Option<Self> {
        match self {
            Self::Proceed => None,
            Self::Skip => Some(Self::Proceed),
            Self::SkipForever => Some(Self::Skip),
        }
    }

    fn next(self) -> Option<Self> {
        match self {
            Self::Proceed => Some(Self::Skip),
            Self::Skip => Some(Self::SkipForever),
            Self::SkipForever => None,
        }
    }
}

#[derive(Clone, Debug, PartialEq, Eq)]
struct MigrationSelection {
    item: ExternalAgentConfigMigrationItem,
    enabled: bool,
}

struct RenderLineEntry {
    item_idx: Option<usize>,
    kind: RenderLineKind,
    line: Line<'static>,
}

#[derive(Clone, Copy, Debug, PartialEq, Eq)]
enum RenderLineKind {
    Section,
    Item,
    ItemDetail,
}

pub(crate) async fn run_external_agent_config_migration_prompt(
    tui: &mut Tui,
    items: &[ExternalAgentConfigMigrationItem],
    selected_items: &[ExternalAgentConfigMigrationItem],
    error: Option<&str>,
) -> ExternalAgentConfigMigrationOutcome {
    let mut screen = ExternalAgentConfigMigrationScreen::new(
        tui.frame_requester(),
        items,
        selected_items,
        error.map(str::to_owned),
    );

    let _ = tui.draw(u16::MAX, |frame| {
        frame.render_widget_ref(&screen, frame.area());
    });

    let events = tui.event_stream();
    tokio::pin!(events);

    while !screen.is_done() {
        if let Some(event) = events.next().await {
            match event {
                TuiEvent::Key(key_event) => screen.handle_key(key_event),
                TuiEvent::Paste(_) => {}
                TuiEvent::Draw | TuiEvent::Resize => {
                    let _ = tui.draw(u16::MAX, |frame| {
                        frame.render_widget_ref(&screen, frame.area());
                    });
                }
            }
        } else {
            screen.skip();
            break;
        }
    }

    screen.outcome()
}

struct ExternalAgentConfigMigrationScreen {
    request_frame: FrameRequester,
    items: Vec<MigrationSelection>,
    selected_item_idx: Option<usize>,
    scroll_top: usize,
    focus: FocusArea,
    highlighted_action: ActionMenuOption,
    done: bool,
    outcome: ExternalAgentConfigMigrationOutcome,
    error: Option<String>,
}

impl ExternalAgentConfigMigrationScreen {
    fn proceed_enabled(&self) -> bool {
        self.selected_count() > 0
    }

    fn first_available_action(&self) -> ActionMenuOption {
        if self.proceed_enabled() {
            ActionMenuOption::Proceed
        } else {
            ActionMenuOption::Skip
        }
    }

    fn previous_available_action(&self, action: ActionMenuOption) -> Option<ActionMenuOption> {
        let mut candidate = action.previous();
        while let Some(option) = candidate {
            if option != ActionMenuOption::Proceed || self.proceed_enabled() {
                return Some(option);
            }
            candidate = option.previous();
        }
        None
    }

    fn next_available_action(&self, action: ActionMenuOption) -> Option<ActionMenuOption> {
        let mut candidate = action.next();
        while let Some(option) = candidate {
            if option != ActionMenuOption::Proceed || self.proceed_enabled() {
                return Some(option);
            }
            candidate = option.next();
        }
        None
    }

    fn normalize_highlighted_action(&mut self) {
        if self.highlighted_action == ActionMenuOption::Proceed && !self.proceed_enabled() {
            self.highlighted_action = self.first_available_action();
        }
    }

    fn display_description(item: &ExternalAgentConfigMigrationItem) -> String {
        let Some(cwd) = item.cwd.as_deref() else {
            return item.description.clone();
        };

        fn reformat_description(
            description: &str,
            prefix: &str,
            separator: &str,
            cwd: &std::path::Path,
        ) -> Option<String> {
            let remainder = description.strip_prefix(prefix)?;
            let (left, right) = remainder.split_once(separator)?;
            Some(format!(
                "{prefix}{}{}{}",
                display_path_for(std::path::Path::new(left), cwd),
                separator,
                display_path_for(std::path::Path::new(right), cwd)
            ))
        }

        if let Some(reformatted) =
            reformat_description(&item.description, "Migrate ", " into ", cwd)
        {
            return reformatted;
        }

        if let Some(reformatted) =
            reformat_description(&item.description, "Migrate skills from ", " to ", cwd)
        {
            return reformatted;
        }

        if let Some(reformatted) = reformat_description(&item.description, "Migrate ", " to ", cwd)
        {
            return reformatted;
        }

        if let Some(reformatted) = reformat_description(&item.description, "Import ", " to ", cwd) {
            return reformatted;
        }

        if let Some(source) = item
            .description
            .strip_prefix("Migrate enabled plugins from ")
        {
            let description = format!(
                "Migrate enabled plugins from {}",
                display_path_for(std::path::Path::new(source), cwd)
            );
            if let Some(details) = &item.details {
                let marketplace_count = details.plugins.len();
                let plugin_count = details
                    .plugins
                    .iter()
                    .map(|plugin_group| plugin_group.plugin_names.len())
                    .sum::<usize>();
                return format!(
                    "{description} ({marketplace_count} {}, {plugin_count} {})",
                    if marketplace_count == 1 {
                        "marketplace"
                    } else {
                        "marketplaces"
                    },
                    if plugin_count == 1 {
                        "plugin"
                    } else {
                        "plugins"
                    }
                );
            }
            return description;
        }

        item.description.clone()
    }

    fn new(
        request_frame: FrameRequester,
        items: &[ExternalAgentConfigMigrationItem],
        selected_items: &[ExternalAgentConfigMigrationItem],
        error: Option<String>,
    ) -> Self {
        let items = items
            .iter()
            .cloned()
            .map(|item| MigrationSelection {
                enabled: selected_items.contains(&item),
                item,
            })
            .collect::<Vec<_>>();
        let selected_item_idx = (!items.is_empty()).then_some(0);
        Self {
            request_frame,
            items,
            selected_item_idx,
            scroll_top: 0,
            focus: FocusArea::Items,
            highlighted_action: ActionMenuOption::Proceed,
            done: false,
            outcome: ExternalAgentConfigMigrationOutcome::Skip,
            error,
        }
    }

    fn plugin_detail_lines(plugin_groups: &[PluginsMigration]) -> Vec<Line<'static>> {
        let mut lines = plugin_groups
            .iter()
            .take(3)
            .map(|plugin_group| {
                let mut plugin_names = plugin_group
                    .plugin_names
                    .iter()
                    .take(2)
                    .cloned()
                    .collect::<Vec<_>>();
                let hidden_plugin_count = plugin_group
                    .plugin_names
                    .len()
                    .saturating_sub(plugin_names.len());
                if hidden_plugin_count > 0 {
                    plugin_names.push(format!("+{hidden_plugin_count} more"));
                }
                Line::from(format!(
                    "      • {}: {}",
                    plugin_group.marketplace_name,
                    plugin_names.join(", ")
                ))
            })
            .collect::<Vec<_>>();
        let hidden_marketplace_count = plugin_groups.len().saturating_sub(lines.len());
        if hidden_marketplace_count > 0 {
            lines.push(Line::from(format!(
                "      • +{hidden_marketplace_count} more marketplaces"
            )));
        }
        lines
    }

    fn is_done(&self) -> bool {
        self.done
    }

    fn outcome(&self) -> ExternalAgentConfigMigrationOutcome {
        self.outcome.clone()
    }

    fn finish_with(&mut self, outcome: ExternalAgentConfigMigrationOutcome) {
        self.outcome = outcome;
        self.done = true;
        self.request_frame.schedule_frame();
    }

    fn proceed(&mut self) {
        let selected = self.selected_items();
        if selected.is_empty() {
            self.error = Some("Select at least one item or choose a skip option.".to_string());
            self.request_frame.schedule_frame();
            return;
        }

        self.finish_with(ExternalAgentConfigMigrationOutcome::Proceed(selected));
    }

    fn skip(&mut self) {
        self.finish_with(ExternalAgentConfigMigrationOutcome::Skip);
    }

    fn skip_forever(&mut self) {
        self.finish_with(ExternalAgentConfigMigrationOutcome::SkipForever);
    }

    fn exit(&mut self) {
        self.finish_with(ExternalAgentConfigMigrationOutcome::Exit);
    }

    fn selected_items(&self) -> Vec<ExternalAgentConfigMigrationItem> {
        self.items
            .iter()
            .filter(|item| item.enabled)
            .map(|item| item.item.clone())
            .collect()
    }

    fn selected_count(&self) -> usize {
        self.items.iter().filter(|item| item.enabled).count()
    }

    fn set_all_enabled(&mut self, enabled: bool) {
        for item in &mut self.items {
            item.enabled = enabled;
        }
        self.error = None;
        self.normalize_highlighted_action();
        self.request_frame.schedule_frame();
    }

    fn toggle_selected_item(&mut self) {
        if self.focus != FocusArea::Items {
            return;
        }
        let Some(selected_idx) = self.selected_item_idx else {
            return;
        };
        let Some(item) = self.items.get_mut(selected_idx) else {
            return;
        };

        item.enabled = !item.enabled;
        self.error = None;
        self.normalize_highlighted_action();
        self.request_frame.schedule_frame();
    }

    fn move_up(&mut self) {
        match self.focus {
            FocusArea::Items => match self.selected_item_idx {
                Some(0) => {
                    self.focus = FocusArea::Actions;
                    self.highlighted_action = ActionMenuOption::SkipForever;
                }
                Some(idx) => {
                    self.selected_item_idx = Some(idx.saturating_sub(1));
                }
                None => {
                    self.focus = FocusArea::Actions;
                    self.highlighted_action = ActionMenuOption::SkipForever;
                }
            },
            FocusArea::Actions => {
                if let Some(previous) = self.previous_available_action(self.highlighted_action) {
                    self.highlighted_action = previous;
                } else {
                    self.focus = FocusArea::Items;
                    if !self.items.is_empty() {
                        self.selected_item_idx = Some(self.items.len() - 1);
                    }
                }
            }
        }
        self.ensure_selected_item_visible();
        self.request_frame.schedule_frame();
    }

    fn move_down(&mut self) {
        match self.focus {
            FocusArea::Items => match self.selected_item_idx {
                Some(idx) if idx + 1 < self.items.len() => {
                    self.selected_item_idx = Some(idx + 1);
                }
                _ => {
                    self.focus = FocusArea::Actions;
                    self.highlighted_action = self.first_available_action();
                }
            },
            FocusArea::Actions => {
                if let Some(next) = self.next_available_action(self.highlighted_action) {
                    self.highlighted_action = next;
                } else {
                    self.focus = FocusArea::Items;
                    if !self.items.is_empty() {
                        self.selected_item_idx = Some(0);
                    }
                }
            }
        }
        self.ensure_selected_item_visible();
        self.request_frame.schedule_frame();
    }

    fn confirm_selection(&mut self) {
        match self.focus {
            FocusArea::Items => self.toggle_selected_item(),
            FocusArea::Actions => match self.highlighted_action {
                ActionMenuOption::Proceed => self.proceed(),
                ActionMenuOption::Skip => self.skip(),
                ActionMenuOption::SkipForever => self.skip_forever(),
            },
        }
    }

    fn handle_key(&mut self, key_event: KeyEvent) {
        if key_event.kind == KeyEventKind::Release {
            return;
        }

        if is_ctrl_exit_combo(key_event) {
            self.exit();
            return;
        }

        match key_event.code {
            KeyCode::Up | KeyCode::Char('k') => self.move_up(),
            KeyCode::Down | KeyCode::Char('j') => self.move_down(),
            KeyCode::Char('1') => {
                self.focus = FocusArea::Actions;
                self.highlighted_action = ActionMenuOption::Proceed;
                self.proceed();
            }
            KeyCode::Char('2') => {
                self.focus = FocusArea::Actions;
                self.highlighted_action = ActionMenuOption::Skip;
                self.skip();
            }
            KeyCode::Char('3') => {
                self.focus = FocusArea::Actions;
                self.highlighted_action = ActionMenuOption::SkipForever;
                self.skip_forever();
            }
            KeyCode::Char(' ') => self.toggle_selected_item(),
            KeyCode::Char('a') => self.set_all_enabled(/*enabled*/ true),
            KeyCode::Char('n') => self.set_all_enabled(/*enabled*/ false),
            KeyCode::Enter => self.confirm_selection(),
            KeyCode::Esc => self.skip(),
            _ => {}
        }
    }

    fn ensure_selected_item_visible(&mut self) {
        let Some(selected_idx) = self.selected_item_idx else {
            self.scroll_top = 0;
            return;
        };
        let selected_render_idx = self.selected_render_line_index(selected_idx);
        let visible_rows = self.render_line_count().max(1);
        if selected_render_idx < self.scroll_top {
            self.scroll_top = selected_render_idx;
        } else {
            let bottom = self.scroll_top + visible_rows.saturating_sub(1);
            if selected_render_idx > bottom {
                self.scroll_top = selected_render_idx + 1 - visible_rows;
            }
        }
    }

    fn render_line_count(&self) -> usize {
        self.build_render_lines().len()
    }

    fn selected_render_line_index(&self, selected_item_idx: usize) -> usize {
        self.build_render_lines()
            .iter()
            .position(|entry| entry.item_idx == Some(selected_item_idx))
            .unwrap_or(selected_item_idx)
    }

    fn section_title(cwd: Option<&std::path::Path>) -> Line<'static> {
        match cwd {
            Some(cwd) => Line::from(vec!["Project: ".bold(), cwd.display().to_string().dim()]),
            None => Line::from("Home".bold()),
        }
    }

    fn build_render_lines(&self) -> Vec<RenderLineEntry> {
        let mut lines = Vec::new();
        let mut current_scope: Option<Option<&std::path::Path>> = None;
        for (idx, item) in self.items.iter().enumerate() {
            let scope = item.item.cwd.as_deref();
            if current_scope != Some(scope) {
                if current_scope.is_some() {
                    lines.push(RenderLineEntry {
                        item_idx: None,
                        kind: RenderLineKind::Section,
                        line: Line::from(""),
                    });
                }
                lines.push(RenderLineEntry {
                    item_idx: None,
                    kind: RenderLineKind::Section,
                    line: Self::section_title(scope),
                });
                current_scope = Some(scope);
            }
            lines.push(RenderLineEntry {
                item_idx: Some(idx),
                kind: RenderLineKind::Item,
                line: Line::from(format!(
                    "  [{}] {}",
                    if item.enabled { "x" } else { " " },
                    Self::display_description(&item.item)
                )),
            });
            if let Some(details) = &item.item.details {
                for line in Self::plugin_detail_lines(&details.plugins) {
                    lines.push(RenderLineEntry {
                        item_idx: None,
                        kind: RenderLineKind::ItemDetail,
                        line,
                    });
                }
            }
        }
        lines
    }

    fn render_items(&self, area: Rect, buf: &mut Buffer) {
        if area.height == 0 || area.width == 0 {
            return;
        }
        let rows = self.build_render_lines();
        let visible_rows = area.height as usize;
        let mut start_idx = self.scroll_top.min(rows.len().saturating_sub(1));
        if let Some(selected_item_idx) = self.selected_item_idx {
            let selected_render_idx = self.selected_render_line_index(selected_item_idx);
            if selected_render_idx < start_idx {
                start_idx = selected_render_idx;
            } else if visible_rows > 0 {
                let bottom = start_idx + visible_rows - 1;
                if selected_render_idx > bottom {
                    start_idx = selected_render_idx + 1 - visible_rows;
                }
            }
        }

        let mut y = area.y;
        for entry in rows.iter().skip(start_idx).take(visible_rows) {
            if y >= area.y + area.height {
                break;
            }

            let selected =
                self.focus == FocusArea::Items && self.selected_item_idx == entry.item_idx;
            let mut line = entry.line.clone();
            if selected {
                line.spans.iter_mut().for_each(|span| {
                    span.style = span.style.patch(accent_style());
                });
            } else if entry.kind != RenderLineKind::Item && !line.spans.is_empty() {
                line.spans.iter_mut().for_each(|span| {
                    span.style = span.style.dim();
                });
            }
            let line = truncate_line_with_ellipsis_if_overflow(line, area.width as usize);
            line.render(
                Rect {
                    x: area.x,
                    y,
                    width: area.width,
                    height: 1,
                },
                buf,
            );
            y = y.saturating_add(1);
        }
    }
}

impl WidgetRef for &ExternalAgentConfigMigrationScreen {
    fn render_ref(&self, area: Rect, buf: &mut Buffer) {
        Clear.render(area, buf);

        let inner_area = area.inset(Insets::vh(/*v*/ 1, /*h*/ 2));
        let error_height = u16::from(self.error.is_some());
        let fixed_height = 1u16 + 2u16 + error_height + 1u16 + 4u16 + 1u16;
        let list_height =
            self.render_line_count()
                .max(1)
                .min(inner_area.height.saturating_sub(fixed_height) as usize) as u16;
        let [
            header_area,
            intro_area,
            error_area,
            list_area,
            list_gap_area,
            actions_area,
            footer_area,
            _spacer_area,
        ] = Layout::vertical([
            Constraint::Length(1),
            Constraint::Length(2),
            Constraint::Length(error_height),
            Constraint::Length(list_height),
            Constraint::Length(1),
            Constraint::Length(4),
            Constraint::Length(1),
            Constraint::Fill(1),
        ])
        .areas(inner_area);

        let heading = Line::from(vec!["> ".into(), "External agent config detected".bold()]);
        heading.render(header_area, buf);

        Paragraph::new(vec![
            Line::from("We found settings from another agent that you can add to this project."),
            Line::from("Select what to import"),
        ])
        .wrap(Wrap { trim: false })
        .render(intro_area, buf);

        if let Some(error) = &self.error {
            Paragraph::new(error.clone().red().to_string())
                .wrap(Wrap { trim: false })
                .render(error_area, buf);
        }

        self.render_items(list_area, buf);
        Clear.render(list_gap_area, buf);

        let [
            actions_intro_area,
            proceed_area,
            skip_area,
            skip_forever_area,
        ] = Layout::vertical([
            Constraint::Length(1),
            Constraint::Length(1),
            Constraint::Length(1),
            Constraint::Length(1),
        ])
        .areas(actions_area);
        let actions_intro = format!(
            "Selected {} of {} item(s).",
            self.selected_count(),
            self.items.len()
        );
        Paragraph::new(actions_intro)
            .wrap(Wrap { trim: false })
            .render(actions_intro_area, buf);
        selection_option_row_with_dim(
            /*index*/ 0,
            ActionMenuOption::Proceed.label().to_string(),
            self.focus == FocusArea::Actions
                && self.highlighted_action == ActionMenuOption::Proceed,
            /*dim*/ self.focus != FocusArea::Actions || !self.proceed_enabled(),
        )
        .render(proceed_area, buf);
        selection_option_row_with_dim(
            /*index*/ 1,
            ActionMenuOption::Skip.label().to_string(),
            self.focus == FocusArea::Actions && self.highlighted_action == ActionMenuOption::Skip,
            /*dim*/ self.focus != FocusArea::Actions,
        )
        .render(skip_area, buf);
        selection_option_row_with_dim(
            /*index*/ 2,
            ActionMenuOption::SkipForever.label().to_string(),
            self.focus == FocusArea::Actions
                && self.highlighted_action == ActionMenuOption::SkipForever,
            /*dim*/ self.focus != FocusArea::Actions,
        )
        .render(skip_forever_area, buf);

        Line::from(vec![
            "Use ".dim(),
            key_hint::plain(KeyCode::Up).into(),
            "/".dim(),
            key_hint::plain(KeyCode::Down).into(),
            " to move, ".dim(),
            key_hint::plain(KeyCode::Char(' ')).into(),
            " to toggle, ".dim(),
            "1".cyan(),
            "/".dim(),
            "2".cyan(),
            "/".dim(),
            "3".cyan(),
            " to choose, ".dim(),
            "a".cyan(),
            "/".dim(),
            "n".cyan(),
            " for all/none".dim(),
        ])
        .render(footer_area, buf);
    }
}

fn is_ctrl_exit_combo(key_event: KeyEvent) -> bool {
    key_event.modifiers.contains(KeyModifiers::CONTROL)
        && matches!(key_event.code, KeyCode::Char('c') | KeyCode::Char('d'))
}

#[cfg(test)]
mod tests {
    use super::ActionMenuOption;
    use super::ExternalAgentConfigMigrationOutcome;
    use super::ExternalAgentConfigMigrationScreen;
    use super::FocusArea;
    use crate::custom_terminal::Terminal;
    use crate::test_backend::VT100Backend;
    use crate::tui::FrameRequester;
    use codex_app_server_protocol::ExternalAgentConfigMigrationItem;
    use codex_app_server_protocol::ExternalAgentConfigMigrationItemType;
    use codex_app_server_protocol::PluginsMigration;
    use crossterm::event::KeyCode;
    use crossterm::event::KeyEvent;
    use crossterm::event::KeyModifiers;
    use insta::assert_snapshot;
    use pretty_assertions::assert_eq;
    use ratatui::layout::Rect;
    use std::path::PathBuf;

    fn sample_plugin_details() -> codex_app_server_protocol::MigrationDetails {
        codex_app_server_protocol::MigrationDetails {
            plugins: vec![
                PluginsMigration {
                    marketplace_name: "acme-tools".to_string(),
                    plugin_names: vec![
                        "deployer".to_string(),
                        "formatter".to_string(),
                        "lint".to_string(),
                    ],
                },
                PluginsMigration {
                    marketplace_name: "team-marketplace".to_string(),
                    plugin_names: vec!["asana".to_string()],
                },
                PluginsMigration {
                    marketplace_name: "debug".to_string(),
                    plugin_names: vec!["sample".to_string()],
                },
                PluginsMigration {
                    marketplace_name: "data-tools".to_string(),
                    plugin_names: vec!["warehouse".to_string()],
                },
            ],
            ..Default::default()
        }
    }

    #[cfg(windows)]
    fn sample_project_root() -> PathBuf {
        PathBuf::from(r"C:\workspace\project")
    }

    #[cfg(not(windows))]
    fn sample_project_root() -> PathBuf {
        PathBuf::from("/workspace/project")
    }

    fn sample_project_path(path: &str) -> String {
        sample_project_root().join(path).display().to_string()
    }

    fn sample_items() -> Vec<ExternalAgentConfigMigrationItem> {
        let project_root = sample_project_root();
        vec![
            ExternalAgentConfigMigrationItem {
                item_type: ExternalAgentConfigMigrationItemType::Config,
                description:
                    "Migrate /Users/alex/.claude/settings.json into /Users/alex/.codex/config.toml"
                        .to_string(),
                cwd: None,
                details: None,
            },
            ExternalAgentConfigMigrationItem {
                item_type: ExternalAgentConfigMigrationItemType::Plugins,
                description: format!(
                    "Migrate enabled plugins from {}",
                    sample_project_path(".claude/settings.json")
                ),
                cwd: Some(project_root.clone()),
                details: Some(sample_plugin_details()),
            },
            ExternalAgentConfigMigrationItem {
                item_type: ExternalAgentConfigMigrationItemType::AgentsMd,
                description: format!(
                    "Migrate {} to {}",
                    sample_project_path("CLAUDE.md"),
                    sample_project_path("AGENTS.md")
                ),
                cwd: Some(project_root),
                details: None,
            },
        ]
    }

    fn render_screen(
        screen: &ExternalAgentConfigMigrationScreen,
        width: u16,
        height: u16,
    ) -> String {
        let backend = VT100Backend::new(width, height);
        let mut terminal = Terminal::with_options(backend).expect("terminal");
        terminal.set_viewport_area(Rect::new(0, 0, width, height));
        {
            let mut frame = terminal.get_frame();
            frame.render_widget_ref(screen, frame.area());
        }
        terminal.flush().expect("flush");
        terminal.backend().to_string()
    }

    #[test]
    fn prompt_snapshot() {
        let items = sample_items();
        let screen = ExternalAgentConfigMigrationScreen::new(
            FrameRequester::test_dummy(),
            &items,
            &items,
            /*error*/ None,
        );

        let rendered = render_screen(&screen, /*width*/ 80, /*height*/ 21);
        #[cfg(windows)]
        assert_snapshot!("external_agent_config_migration_prompt_windows", rendered);
        #[cfg(not(windows))]
        assert_snapshot!("external_agent_config_migration_prompt", rendered);
    }

    #[test]
    fn proceed_returns_selected_items() {
        let items = sample_items();
        let mut screen = ExternalAgentConfigMigrationScreen::new(
            FrameRequester::test_dummy(),
            &items,
            &items,
            /*error*/ None,
        );

        screen.handle_key(KeyEvent::new(KeyCode::Down, KeyModifiers::NONE));
        screen.handle_key(KeyEvent::new(KeyCode::Down, KeyModifiers::NONE));
        screen.handle_key(KeyEvent::new(KeyCode::Down, KeyModifiers::NONE));
        screen.handle_key(KeyEvent::new(KeyCode::Enter, KeyModifiers::NONE));

        assert!(screen.is_done());
        assert_eq!(
            screen.outcome(),
            ExternalAgentConfigMigrationOutcome::Proceed(items)
        );
    }

    #[test]
    fn toggle_item_then_proceed_keeps_remaining_selection() {
        let items = sample_items();
        let mut screen = ExternalAgentConfigMigrationScreen::new(
            FrameRequester::test_dummy(),
            &items,
            &items,
            /*error*/ None,
        );

        screen.handle_key(KeyEvent::new(KeyCode::Char(' '), KeyModifiers::NONE));
        screen.handle_key(KeyEvent::new(KeyCode::Down, KeyModifiers::NONE));
        screen.handle_key(KeyEvent::new(KeyCode::Down, KeyModifiers::NONE));
        screen.handle_key(KeyEvent::new(KeyCode::Down, KeyModifiers::NONE));
        screen.handle_key(KeyEvent::new(KeyCode::Enter, KeyModifiers::NONE));

        assert!(screen.is_done());
        assert_eq!(
            screen.outcome(),
            ExternalAgentConfigMigrationOutcome::Proceed(vec![items[1].clone(), items[2].clone(),])
        );
    }

    #[test]
    fn escape_skips_prompt() {
        let items = sample_items();
        let mut screen = ExternalAgentConfigMigrationScreen::new(
            FrameRequester::test_dummy(),
            &items,
            &items,
            /*error*/ None,
        );

        screen.handle_key(KeyEvent::new(KeyCode::Esc, KeyModifiers::NONE));

        assert!(screen.is_done());
        assert_eq!(screen.outcome(), ExternalAgentConfigMigrationOutcome::Skip);
    }

    #[test]
    fn skip_forever_returns_skip_forever_outcome() {
        let items = sample_items();
        let mut screen = ExternalAgentConfigMigrationScreen::new(
            FrameRequester::test_dummy(),
            &items,
            &items,
            /*error*/ None,
        );

        screen.move_down();
        screen.move_down();
        screen.move_down();
        screen.move_down();
        screen.move_down();
        screen.confirm_selection();

        assert_eq!(
            screen.outcome(),
            ExternalAgentConfigMigrationOutcome::SkipForever
        );
    }

    #[test]
    fn proceed_requires_at_least_one_selected_item() {
        let items = sample_items();
        let mut screen = ExternalAgentConfigMigrationScreen::new(
            FrameRequester::test_dummy(),
            &items,
            &items,
            /*error*/ None,
        );

        screen.handle_key(KeyEvent::new(KeyCode::Char('n'), KeyModifiers::NONE));
        screen.handle_key(KeyEvent::new(KeyCode::Char('1'), KeyModifiers::NONE));

        assert!(!screen.is_done());
        assert_eq!(screen.highlighted_action, ActionMenuOption::Proceed);
        let rendered = render_screen(&screen, /*width*/ 80, /*height*/ 20);
        assert!(
            rendered.contains("Select at least one item or choose a skip option."),
            "expected inline validation error, got:\n{rendered}"
        );
    }

    #[test]
    fn proceed_action_is_skipped_when_no_items_are_selected() {
        let items = sample_items();
        let mut screen = ExternalAgentConfigMigrationScreen::new(
            FrameRequester::test_dummy(),
            &items,
            &items,
            /*error*/ None,
        );

        screen.handle_key(KeyEvent::new(KeyCode::Char('n'), KeyModifiers::NONE));
        screen.handle_key(KeyEvent::new(KeyCode::Down, KeyModifiers::NONE));
        screen.handle_key(KeyEvent::new(KeyCode::Down, KeyModifiers::NONE));
        screen.handle_key(KeyEvent::new(KeyCode::Down, KeyModifiers::NONE));

        assert_eq!(screen.focus, FocusArea::Actions);
        assert_eq!(screen.highlighted_action, ActionMenuOption::Skip);
    }

    #[test]
    fn numeric_shortcuts_choose_actions() {
        let items = sample_items();

        let mut proceed_screen = ExternalAgentConfigMigrationScreen::new(
            FrameRequester::test_dummy(),
            &items,
            &items,
            /*error*/ None,
        );
        proceed_screen.handle_key(KeyEvent::new(KeyCode::Char('1'), KeyModifiers::NONE));
        assert_eq!(
            proceed_screen.outcome(),
            ExternalAgentConfigMigrationOutcome::Proceed(items.clone())
        );

        let mut skip_screen = ExternalAgentConfigMigrationScreen::new(
            FrameRequester::test_dummy(),
            &items,
            &items,
            /*error*/ None,
        );
        skip_screen.handle_key(KeyEvent::new(KeyCode::Char('2'), KeyModifiers::NONE));
        assert_eq!(
            skip_screen.outcome(),
            ExternalAgentConfigMigrationOutcome::Skip
        );

        let mut skip_forever_screen = ExternalAgentConfigMigrationScreen::new(
            FrameRequester::test_dummy(),
            &items,
            &items,
            /*error*/ None,
        );
        skip_forever_screen.handle_key(KeyEvent::new(KeyCode::Char('3'), KeyModifiers::NONE));
        assert_eq!(
            skip_forever_screen.outcome(),
            ExternalAgentConfigMigrationOutcome::SkipForever
        );
    }
}