use anyhow::Result;
use crossterm::event::{KeyCode, KeyEvent, KeyModifiers};
use std::collections::HashMap;
use std::path::PathBuf;
use std::sync::Arc;
use std::time::{Duration, Instant};

use std::rc::Rc;

use ratatui::style::Color;

use crate::command::cmd::CmdContext;
use crate::command::keymap::{Keymap, KeymapSet};
use crate::import::wizard::ImportWizard;
use crate::model::cell::CellValue;
use crate::model::Model;
use crate::persistence;
use crate::ui::grid::{
    compute_col_widths, compute_row_header_width, compute_visible_cols, parse_number_format,
};
use crate::view::GridLayout;

/// Drill-down state: frozen record snapshot + pending edits that have not
/// yet been applied to the model.
#[derive(Debug, Clone, Default)]
pub struct DrillState {
    /// Frozen snapshot of records shown in the drill view (Rc for cheap cloning).
    pub records: Rc<Vec<(crate::model::cell::CellKey, crate::model::cell::CellValue)>>,
    /// Pending edits keyed by (record_idx, column_name) → new string value.
    /// column_name is either "Value" or a category name.
    pub pending_edits: std::collections::HashMap<(usize, String), String>,
}

/// Display configuration for the bottom-bar minibuffer.
/// Carried structurally by text-entry `AppMode` variants.
#[derive(Debug, Clone, PartialEq)]
pub struct MinibufferConfig {
    pub buffer_key: &'static str,
    pub prompt: String,
    pub color: Color,
}

#[derive(Debug, Clone, PartialEq)]
pub enum AppMode {
    Normal,
    Editing {
        minibuf: MinibufferConfig,
    },
    FormulaEdit {
        minibuf: MinibufferConfig,
    },
    FormulaPanel,
    CategoryPanel,
    /// Quick-add a new category: Enter adds and stays open, Esc closes.
    CategoryAdd {
        minibuf: MinibufferConfig,
    },
    /// Quick-add items to `category`: Enter adds and stays open, Esc closes.
    ItemAdd {
        category: String,
        minibuf: MinibufferConfig,
    },
    ViewPanel,
    TileSelect,
    ImportWizard,
    ExportPrompt {
        minibuf: MinibufferConfig,
    },
    /// Vim-style `:` command line
    CommandMode {
        minibuf: MinibufferConfig,
    },
    Help,
    Quit,
}

impl AppMode {
    /// Extract the minibuffer config from text-entry modes, if present.
    pub fn minibuffer(&self) -> Option<&MinibufferConfig> {
        match self {
            Self::Editing { minibuf, .. }
            | Self::FormulaEdit { minibuf, .. }
            | Self::CommandMode { minibuf, .. }
            | Self::CategoryAdd { minibuf, .. }
            | Self::ItemAdd { minibuf, .. }
            | Self::ExportPrompt { minibuf, .. } => Some(minibuf),
            _ => None,
        }
    }

    pub fn editing() -> Self {
        Self::Editing {
            minibuf: MinibufferConfig {
                buffer_key: "edit",
                prompt: "edit: ".into(),
                color: Color::Green,
            },
        }
    }

    pub fn formula_edit() -> Self {
        Self::FormulaEdit {
            minibuf: MinibufferConfig {
                buffer_key: "formula",
                prompt: "formula: ".into(),
                color: Color::Cyan,
            },
        }
    }

    pub fn command_mode() -> Self {
        Self::CommandMode {
            minibuf: MinibufferConfig {
                buffer_key: "command",
                prompt: ":".into(),
                color: Color::Yellow,
            },
        }
    }

    pub fn category_add() -> Self {
        Self::CategoryAdd {
            minibuf: MinibufferConfig {
                buffer_key: "category",
                prompt: "new category: ".into(),
                color: Color::Yellow,
            },
        }
    }

    pub fn item_add(category: String) -> Self {
        let prompt = format!("add item to {category}: ");
        Self::ItemAdd {
            category,
            minibuf: MinibufferConfig {
                buffer_key: "item",
                prompt,
                color: Color::Green,
            },
        }
    }

    pub fn export_prompt() -> Self {
        Self::ExportPrompt {
            minibuf: MinibufferConfig {
                buffer_key: "export",
                prompt: "export path: ".into(),
                color: Color::Yellow,
            },
        }
    }
}

pub struct App {
    pub model: Model,
    pub file_path: Option<PathBuf>,
    pub mode: AppMode,
    pub status_msg: String,
    pub wizard: Option<ImportWizard>,
    pub last_autosave: Instant,
    pub search_query: String,
    pub search_mode: bool,
    pub formula_panel_open: bool,
    pub category_panel_open: bool,
    pub view_panel_open: bool,
    pub cat_panel_cursor: usize,
    pub view_panel_cursor: usize,
    pub formula_cursor: usize,
    pub dirty: bool,
    /// Yanked cell value for `p` paste
    pub yanked: Option<CellValue>,
    /// Tile select cursor (which category index is highlighted)
    pub tile_cat_idx: usize,
    /// View navigation history: views visited before the current one.
    /// Pushed on SwitchView, popped by `<` (back).
    pub view_back_stack: Vec<String>,
    /// Views that were "back-ed" from, available for forward navigation (`>`).
    pub view_forward_stack: Vec<String>,
    /// Frozen records list for the drill view. When present, this is the
    /// snapshot that records-mode layouts iterate — records don't disappear
    /// when filters would change. Pending edits are stored alongside and
    /// applied to the model on commit/navigate-away.
    pub drill_state: Option<DrillState>,
    /// Current page index in the Help screen (0-based).
    pub help_page: usize,
    /// Terminal dimensions (updated on resize and at startup).
    pub term_width: u16,
    pub term_height: u16,
    /// Categories expanded in the category panel tree view.
    pub expanded_cats: std::collections::HashSet<String>,
    /// Named text buffers for text-entry modes
    pub buffers: HashMap<String, String>,
    /// Transient keymap for Emacs-style prefix key sequences (g→gg, y→yy, etc.)
    pub transient_keymap: Option<Arc<Keymap>>,
    /// Current grid layout, derived from model + view + drill_state.
    /// Rebuilt via `rebuild_layout()` after state changes.
    pub layout: GridLayout,
    keymap_set: KeymapSet,
}

impl App {
    pub fn new(model: Model, file_path: Option<PathBuf>) -> Self {
        let layout = {
            let view = model.active_view();
            GridLayout::with_frozen_records(&model, view, None)
        };
        Self {
            model,
            file_path,
            mode: AppMode::Normal,
            status_msg: String::new(),
            wizard: None,
            last_autosave: Instant::now(),
            search_query: String::new(),
            search_mode: false,
            formula_panel_open: false,
            category_panel_open: false,
            view_panel_open: false,
            cat_panel_cursor: 0,
            view_panel_cursor: 0,
            formula_cursor: 0,
            dirty: false,
            yanked: None,
            tile_cat_idx: 0,
            view_back_stack: Vec::new(),
            view_forward_stack: Vec::new(),
            drill_state: None,
            help_page: 0,
            term_width: crossterm::terminal::size().map(|(w, _)| w).unwrap_or(80),
            term_height: crossterm::terminal::size().map(|(_, h)| h).unwrap_or(24),
            expanded_cats: std::collections::HashSet::new(),
            buffers: HashMap::new(),
            transient_keymap: None,
            layout,
            keymap_set: KeymapSet::default_keymaps(),
        }
    }

    /// Rebuild the grid layout from current model, view, and drill state.
    /// Note: `with_frozen_records` already handles pruning internally.
    pub fn rebuild_layout(&mut self) {
        let view = self.model.active_view();
        let frozen = self.drill_state.as_ref().map(|s| Rc::clone(&s.records));
        self.layout = GridLayout::with_frozen_records(&self.model, view, frozen);
    }

    pub fn cmd_context(&self, key: KeyCode, _mods: KeyModifiers) -> CmdContext<'_> {
        let view = self.model.active_view();
        let layout = &self.layout;
        let (sel_row, sel_col) = view.selected;
        CmdContext {
            model: &self.model,
            layout,
            registry: self.keymap_set.registry(),
            mode: &self.mode,
            selected: view.selected,
            row_offset: view.row_offset,
            col_offset: view.col_offset,
            search_query: &self.search_query,
            yanked: &self.yanked,
            dirty: self.dirty,
            search_mode: self.search_mode,
            formula_panel_open: self.formula_panel_open,
            category_panel_open: self.category_panel_open,
            view_panel_open: self.view_panel_open,
            buffers: &self.buffers,
            formula_cursor: self.formula_cursor,
            cat_panel_cursor: self.cat_panel_cursor,
            view_panel_cursor: self.view_panel_cursor,
            tile_cat_idx: self.tile_cat_idx,
            view_back_stack: &self.view_back_stack,
            view_forward_stack: &self.view_forward_stack,
            display_value: {
                let key = layout.cell_key(sel_row, sel_col);
                if let Some(k) = &key {
                    if let Some((idx, dim)) = crate::view::synthetic_record_info(k) {
                        self.drill_state
                            .as_ref()
                            .and_then(|s| s.pending_edits.get(&(idx, dim)).cloned())
                            .or_else(|| layout.resolve_display(k))
                            .unwrap_or_default()
                    } else {
                        self.model
                            .get_cell(k)
                            .map(|v| v.to_string())
                            .unwrap_or_default()
                    }
                } else {
                    String::new()
                }
            },
            visible_rows: (self.term_height as usize).saturating_sub(8),
            visible_cols: {
                let (fmt_comma, fmt_decimals) = parse_number_format(&view.number_format);
                let col_widths = compute_col_widths(&self.model, layout, fmt_comma, fmt_decimals);
                let row_header_width = compute_row_header_width(layout);
                compute_visible_cols(
                    &col_widths,
                    row_header_width,
                    self.term_width,
                    view.col_offset,
                )
            },
            expanded_cats: &self.expanded_cats,
            key_code: key,
        }
    }

    pub fn apply_effects(&mut self, effects: Vec<Box<dyn super::effect::Effect>>) {
        for effect in effects {
            effect.apply(self);
        }
        self.rebuild_layout();
    }

    /// True when the model has no user-defined categories (show welcome/help).
    /// Virtual categories (_Index, _Dim) are always present and don't count.
    pub fn is_empty_model(&self) -> bool {
        use crate::model::category::CategoryKind;
        self.model
            .categories
            .values()
            .all(|c| matches!(c.kind, CategoryKind::VirtualIndex | CategoryKind::VirtualDim))
    }

    pub fn handle_key(&mut self, key: KeyEvent) -> Result<()> {
        self.rebuild_layout();

        // Transient keymap (prefix key sequence) takes priority
        if let Some(transient) = self.transient_keymap.take() {
            let effects = {
                let ctx = self.cmd_context(key.code, key.modifiers);
                self.keymap_set
                    .dispatch_transient(&transient, &ctx, key.code, key.modifiers)
            };
            if let Some(effects) = effects {
                self.apply_effects(effects);
            }
            // Whether matched or not, transient is consumed
            return Ok(());
        }

        // Try mode keymap — if a binding matches, apply effects and return
        let effects = {
            let ctx = self.cmd_context(key.code, key.modifiers);
            self.keymap_set.dispatch(&ctx, key.code, key.modifiers)
        };
        if let Some(effects) = effects {
            self.apply_effects(effects);
        }
        Ok(())
    }

    pub fn autosave_if_needed(&mut self) {
        if self.dirty && self.last_autosave.elapsed() > Duration::from_secs(30) {
            if let Some(path) = &self.file_path.clone() {
                let ap = persistence::autosave_path(path);
                let _ = persistence::save(&self.model, &ap);
                self.last_autosave = Instant::now();
            }
        }
    }

    pub fn start_import_wizard(&mut self, json: serde_json::Value) {
        self.wizard = Some(ImportWizard::new(json));
        self.mode = AppMode::ImportWizard;
    }

    /// Hint text for the status bar (context-sensitive)
    pub fn hint_text(&self) -> &'static str {
        match &self.mode {
            AppMode::Normal => "hjkl:nav  i:edit  R:records  P:prune  F/C/V:panels  T:tiles  [:]:page  >:drill  ::cmd",
            AppMode::Editing { .. } => "Enter:commit  Tab:commit+right  Esc:cancel",
            AppMode::FormulaPanel => "n:new  d:delete  jk:nav  Esc:back",
            AppMode::FormulaEdit { .. } => "Enter:save  Esc:cancel  — type: Name = expression",
            AppMode::CategoryPanel => "jk:nav  Space:cycle-axis  n:new-cat  a:add-items  d:delete  Esc:back",
            AppMode::CategoryAdd { .. } => "Enter:add & continue  Tab:same  Esc:done — type a category name",
            AppMode::ItemAdd { .. } => "Enter:add & continue  Tab:same  Esc:done — type an item name",
            AppMode::ViewPanel => "jk:nav  Enter:switch  n:new  d:delete  Esc:back",
            AppMode::TileSelect => "hl:select  Enter:cycle  r/c/p/n:set-axis  Esc:back",
            AppMode::CommandMode { .. } => ":q quit  :w save  :import  :add-cat  :formula  :show-item  :help",
            AppMode::ImportWizard => "Space:toggle  c:cycle  Enter:next  Esc:cancel",
            AppMode::Help => "h/l:pages  q/Esc:close",
            _ => "",
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::model::Model;

    fn two_col_model() -> App {
        let mut m = Model::new("T");
        m.add_category("Row").unwrap(); // → Row axis
        m.add_category("Col").unwrap(); // → Column axis
        m.category_mut("Row").unwrap().add_item("A");
        m.category_mut("Row").unwrap().add_item("B");
        m.category_mut("Row").unwrap().add_item("C");
        m.category_mut("Col").unwrap().add_item("X");
        m.category_mut("Col").unwrap().add_item("Y");
        App::new(m, None)
    }

    fn run_cmd(app: &mut App, cmd: &dyn crate::command::cmd::Cmd) {
        let ctx = app.cmd_context(KeyCode::Null, KeyModifiers::NONE);
        let effects = cmd.execute(&ctx);
        drop(ctx);
        app.apply_effects(effects);
    }

    fn enter_advance_cmd(app: &App) -> crate::command::cmd::EnterAdvance {
        use crate::command::cmd::CursorState;
        let view = app.model.active_view();
        let cursor = CursorState {
            row: view.selected.0,
            col: view.selected.1,
            row_count: 3,
            col_count: 2,
            row_offset: 0,
            col_offset: 0,
            visible_rows: 20,
            visible_cols: 8,
        };
        crate::command::cmd::EnterAdvance { cursor }
    }

    #[test]
    fn enter_advance_moves_down_within_column() {
        let mut app = two_col_model();
        app.model.active_view_mut().selected = (0, 0);
        let cmd = enter_advance_cmd(&app);
        run_cmd(&mut app, &cmd);
        assert_eq!(app.model.active_view().selected, (1, 0));
    }

    #[test]
    fn enter_advance_wraps_to_top_of_next_column() {
        let mut app = two_col_model();
        // row_max = 2 (A,B,C), col 0 → should wrap to (0, 1)
        app.model.active_view_mut().selected = (2, 0);
        let cmd = enter_advance_cmd(&app);
        run_cmd(&mut app, &cmd);
        assert_eq!(app.model.active_view().selected, (0, 1));
    }

    #[test]
    fn enter_advance_stays_at_bottom_right() {
        let mut app = two_col_model();
        app.model.active_view_mut().selected = (2, 1);
        let cmd = enter_advance_cmd(&app);
        run_cmd(&mut app, &cmd);
        assert_eq!(app.model.active_view().selected, (2, 1));
    }

    #[test]
    fn import_command_switches_to_import_wizard_mode() {
        // Regression: execute_command was resetting mode to Normal after
        // :import set it to ImportWizard, so the wizard never appeared.
        let mut app = two_col_model();
        let json: serde_json::Value = serde_json::json!([{"cat": "A", "val": 1}]);
        app.start_import_wizard(json);
        assert!(
            matches!(app.mode, AppMode::ImportWizard),
            "mode should be ImportWizard after start_import_wizard"
        );
    }

    #[test]
    fn execute_import_command_leaves_mode_as_import_wizard() {
        let mut app = two_col_model();
        // Inject JSON via start_import_wizard to simulate what :import does
        app.start_import_wizard(serde_json::json!([{"x": 1}]));
        // After the command the mode must NOT be reset to Normal
        assert!(
            !matches!(app.mode, AppMode::Normal),
            "mode must not be Normal after import wizard is opened"
        );
    }

    #[test]
    fn command_mode_typing_appends_to_buffer() {
        use crossterm::event::KeyEvent;
        let mut app = two_col_model();
        // Enter command mode with ':'
        app.handle_key(KeyEvent::new(KeyCode::Char(':'), KeyModifiers::NONE))
            .unwrap();
        assert!(matches!(app.mode, AppMode::CommandMode { .. }));
        assert_eq!(app.buffers.get("command").map(|s| s.as_str()), Some(""));

        // Type 'q'
        app.handle_key(KeyEvent::new(KeyCode::Char('q'), KeyModifiers::NONE))
            .unwrap();
        assert_eq!(app.buffers.get("command").map(|s| s.as_str()), Some("q"));
    }

    #[test]
    fn col_offset_scrolls_when_cursor_moves_past_visible_columns() {
        use crate::model::cell::{CellKey, CellValue};
        // Create a model with 8 wide columns. Column item names are 30 chars
        // each → column widths ~31 chars. With term_width=80, row header ~4,
        // data area ~76 → only ~2 columns actually fit. But the rough estimate
        // (80−30)/12 = 4 over-counts, so viewport_effects never scrolls.
        let mut m = Model::new("T");
        m.add_category("Row").unwrap();
        m.add_category("Col").unwrap();
        m.category_mut("Row").unwrap().add_item("R1");
        for i in 0..8 {
            let name = format!("VeryLongColumnItemName_{i:03}");
            m.category_mut("Col").unwrap().add_item(&name);
        }
        // Populate a value so the model isn't empty
        let key = CellKey::new(vec![
            ("Row".to_string(), "R1".to_string()),
            ("Col".to_string(), "VeryLongColumnItemName_000".to_string()),
        ]);
        m.set_cell(key, CellValue::Number(1.0));

        let mut app = App::new(m, None);
        app.term_width = 80;

        // Press 'l' (right) 3 times to move cursor to column 3.
        // Only ~2 columns fit in 76 chars of data area (each col ~26 chars wide),
        // so column 3 is well off-screen. The buggy estimate (80−30)/12 = 4
        // thinks 4 columns fit, so it won't scroll until col 4.
        for _ in 0..3 {
            app.handle_key(KeyEvent::new(KeyCode::Char('l'), KeyModifiers::NONE))
                .unwrap();
        }

        assert_eq!(
            app.model.active_view().selected.1,
            3,
            "cursor should be at column 3"
        );
        assert!(
            app.model.active_view().col_offset > 0,
            "col_offset should scroll when cursor moves past visible area (only ~2 cols fit \
             in 80-char terminal with 26-char-wide columns), but col_offset is {}",
            app.model.active_view().col_offset
        );
    }

    #[test]
    fn home_jumps_to_first_col() {
        let mut app = two_col_model();
        app.model.active_view_mut().selected = (1, 1);
        app.handle_key(KeyEvent::new(KeyCode::Home, KeyModifiers::NONE))
            .unwrap();
        assert_eq!(app.model.active_view().selected, (1, 0));
    }

    #[test]
    fn end_jumps_to_last_col() {
        let mut app = two_col_model();
        app.model.active_view_mut().selected = (1, 0);
        app.handle_key(KeyEvent::new(KeyCode::End, KeyModifiers::NONE))
            .unwrap();
        assert_eq!(app.model.active_view().selected, (1, 1));
    }

    #[test]
    fn page_down_scrolls_by_three_quarters_visible() {
        let mut app = two_col_model();
        // Add enough rows
        for i in 0..30 {
            app.model
                .category_mut("Row")
                .unwrap()
                .add_item(&format!("R{i}"));
        }
        app.term_height = 28; // ~20 visible rows → delta = 15
        app.model.active_view_mut().selected = (0, 0);
        app.handle_key(KeyEvent::new(KeyCode::PageDown, KeyModifiers::NONE))
            .unwrap();
        assert_eq!(app.model.active_view().selected.1, 0, "column preserved");
        assert!(
            app.model.active_view().selected.0 > 0,
            "row should advance on PageDown"
        );
        // 3/4 of ~20 = 15
        assert_eq!(app.model.active_view().selected.0, 15);
    }

    #[test]
    fn page_up_scrolls_backward() {
        let mut app = two_col_model();
        for i in 0..30 {
            app.model
                .category_mut("Row")
                .unwrap()
                .add_item(&format!("R{i}"));
        }
        app.term_height = 28;
        app.model.active_view_mut().selected = (20, 0);
        app.handle_key(KeyEvent::new(KeyCode::PageUp, KeyModifiers::NONE))
            .unwrap();
        assert_eq!(app.model.active_view().selected.0, 5);
    }

    #[test]
    fn jump_last_row_scrolls_with_small_terminal() {
        let mut app = two_col_model();
        // Total rows: A, B, C + R0..R9 = 13 rows. Last row = 12.
        for i in 0..10 {
            app.model
                .category_mut("Row")
                .unwrap()
                .add_item(&format!("R{i}"));
        }
        app.term_height = 13; // ~5 visible rows
        app.model.active_view_mut().selected = (0, 0);
        // G jumps to last row (row 12)
        app.handle_key(KeyEvent::new(KeyCode::Char('G'), KeyModifiers::NONE))
            .unwrap();
        let last = app.model.active_view().selected.0;
        assert_eq!(last, 12, "should be at last row");
        // With only ~5 visible rows and 13 rows, offset should scroll.
        // Bug: hardcoded 20 means `12 >= 0 + 20` is false → no scroll.
        let offset = app.model.active_view().row_offset;
        assert!(
            offset > 0,
            "row_offset should scroll when last row is beyond visible area, but is {offset}"
        );
    }

    #[test]
    fn ctrl_d_scrolls_viewport_with_small_terminal() {
        let mut app = two_col_model();
        for i in 0..30 {
            app.model
                .category_mut("Row")
                .unwrap()
                .add_item(&format!("R{i}"));
        }
        app.term_height = 13; // ~5 visible rows
        app.model.active_view_mut().selected = (0, 0);
        // Ctrl+d scrolls by 5 rows
        app.handle_key(KeyEvent::new(KeyCode::Char('d'), KeyModifiers::CONTROL))
            .unwrap();
        assert_eq!(app.model.active_view().selected.0, 5);
        // Press Ctrl+d again — now at row 10 with only 5 visible rows,
        // row_offset should have scrolled (not stay at 0 due to hardcoded 20)
        app.handle_key(KeyEvent::new(KeyCode::Char('d'), KeyModifiers::CONTROL))
            .unwrap();
        assert_eq!(app.model.active_view().selected.0, 10);
        assert!(
            app.model.active_view().row_offset > 0,
            "row_offset should scroll with small terminal, but is {}",
            app.model.active_view().row_offset
        );
    }

    #[test]
    fn tab_in_edit_mode_commits_and_moves_right() {
        let mut app = two_col_model();
        app.model.active_view_mut().selected = (0, 0);
        // Enter edit mode
        app.handle_key(KeyEvent::new(KeyCode::Char('i'), KeyModifiers::NONE))
            .unwrap();
        assert!(matches!(app.mode, AppMode::Editing { .. }));
        // Type a digit
        app.handle_key(KeyEvent::new(KeyCode::Char('5'), KeyModifiers::NONE))
            .unwrap();
        // Press Tab — should commit, move right, re-enter edit mode
        app.handle_key(KeyEvent::new(KeyCode::Tab, KeyModifiers::NONE))
            .unwrap();
        // Should be in edit mode on column 1
        assert!(
            matches!(app.mode, AppMode::Editing { .. }),
            "should be in edit mode after Tab, but mode is {:?}",
            app.mode
        );
        assert_eq!(
            app.model.active_view().selected.1,
            1,
            "should have moved to column 1"
        );
    }

    #[test]
    fn command_mode_buffer_cleared_on_reentry() {
        use crossterm::event::KeyEvent;
        let mut app = two_col_model();
        // Enter command mode, type something, escape
        app.handle_key(KeyEvent::new(KeyCode::Char(':'), KeyModifiers::NONE))
            .unwrap();
        app.handle_key(KeyEvent::new(KeyCode::Char('x'), KeyModifiers::NONE))
            .unwrap();
        assert_eq!(app.buffers.get("command").map(|s| s.as_str()), Some("x"));
        app.handle_key(KeyEvent::new(KeyCode::Esc, KeyModifiers::NONE))
            .unwrap();

        // Re-enter command mode — buffer should be cleared
        app.handle_key(KeyEvent::new(KeyCode::Char(':'), KeyModifiers::NONE))
            .unwrap();
        assert_eq!(app.buffers.get("command").map(|s| s.as_str()), Some(""));
    }

    // ── is_empty_model ──────────────────────────────────────────────────

    #[test]
    fn fresh_model_is_empty() {
        let app = App::new(Model::new("T"), None);
        assert!(
            app.is_empty_model(),
            "a brand-new model with only virtual categories should be empty"
        );
    }

    #[test]
    fn model_with_user_category_is_not_empty() {
        let mut m = Model::new("T");
        m.add_category("Sales").unwrap();
        let app = App::new(m, None);
        assert!(
            !app.is_empty_model(),
            "a model with a user-defined category should not be empty"
        );
    }

    // ── Help mode navigation ────────────────────────────────────────────

    #[test]
    fn help_page_next_advances_page() {
        let mut app = App::new(Model::new("T"), None);
        app.mode = AppMode::Help;
        app.help_page = 0;

        app.handle_key(KeyEvent::new(KeyCode::Char('l'), KeyModifiers::NONE))
            .unwrap();
        assert_eq!(app.help_page, 1, "l should advance to page 1");
    }

    #[test]
    fn help_page_prev_goes_back() {
        let mut app = App::new(Model::new("T"), None);
        app.mode = AppMode::Help;
        app.help_page = 2;

        app.handle_key(KeyEvent::new(KeyCode::Char('h'), KeyModifiers::NONE))
            .unwrap();
        assert_eq!(app.help_page, 1, "h should go back to page 1");
    }

    #[test]
    fn help_page_clamps_at_zero() {
        let mut app = App::new(Model::new("T"), None);
        app.mode = AppMode::Help;
        app.help_page = 0;

        app.handle_key(KeyEvent::new(KeyCode::Char('h'), KeyModifiers::NONE))
            .unwrap();
        assert_eq!(app.help_page, 0, "page should not go below 0");
    }

    #[test]
    fn help_page_clamps_at_max() {
        use crate::ui::help::HELP_PAGE_COUNT;

        let mut app = App::new(Model::new("T"), None);
        app.mode = AppMode::Help;
        app.help_page = HELP_PAGE_COUNT - 1;

        app.handle_key(KeyEvent::new(KeyCode::Char('l'), KeyModifiers::NONE))
            .unwrap();
        assert_eq!(
            app.help_page,
            HELP_PAGE_COUNT - 1,
            "page should not exceed the last page"
        );
    }

    // ── Help mode exits ─────────────────────────────────────────────────

    #[test]
    fn help_q_returns_to_normal() {
        let mut app = App::new(Model::new("T"), None);
        app.mode = AppMode::Help;

        app.handle_key(KeyEvent::new(KeyCode::Char('q'), KeyModifiers::NONE))
            .unwrap();
        assert!(
            matches!(app.mode, AppMode::Normal),
            "q should return to Normal mode"
        );
    }

    #[test]
    fn help_esc_returns_to_normal() {
        let mut app = App::new(Model::new("T"), None);
        app.mode = AppMode::Help;

        app.handle_key(KeyEvent::new(KeyCode::Esc, KeyModifiers::NONE))
            .unwrap();
        assert!(
            matches!(app.mode, AppMode::Normal),
            "Esc should return to Normal mode"
        );
    }

    #[test]
    fn help_colon_enters_command_mode() {
        let mut app = App::new(Model::new("T"), None);
        app.mode = AppMode::Help;

        app.handle_key(KeyEvent::new(KeyCode::Char(':'), KeyModifiers::NONE))
            .unwrap();
        assert!(
            matches!(app.mode, AppMode::CommandMode { .. }),
            "colon in Help mode should enter CommandMode, got {:?}",
            app.mode
        );
    }

    // ── Effect error feedback ───────────────────────────────────────────

    #[test]
    fn add_item_to_nonexistent_category_sets_status() {
        use crate::ui::effect::Effect;
        let mut app = App::new(Model::new("T"), None);
        let effect = crate::ui::effect::AddItem {
            category: "Nonexistent".to_string(),
            item: "x".to_string(),
        };
        effect.apply(&mut app);
        assert!(
            app.status_msg.contains("Unknown category"),
            "should report unknown category, got: {:?}",
            app.status_msg
        );
    }

    #[test]
    fn add_formula_with_bad_syntax_sets_status() {
        use crate::ui::effect::Effect;
        let mut app = App::new(Model::new("T"), None);
        let effect = crate::ui::effect::AddFormula {
            raw: "!!!invalid".to_string(),
            target_category: "X".to_string(),
        };
        effect.apply(&mut app);
        assert!(
            app.status_msg.contains("Formula error"),
            "should report formula error, got: {:?}",
            app.status_msg
        );
    }

    // ── Tile select stays in mode ───────────────────────────────────────

    #[test]
    fn tile_axis_change_stays_in_tile_select() {
        let mut app = two_col_model();
        app.mode = AppMode::TileSelect;
        app.tile_cat_idx = 0;

        // Press 'r' to set axis to Row — should stay in TileSelect
        app.handle_key(KeyEvent::new(KeyCode::Char('r'), KeyModifiers::NONE))
            .unwrap();
        assert!(
            matches!(app.mode, AppMode::TileSelect),
            "should stay in TileSelect after axis change, got {:?}",
            app.mode
        );
        assert!(
            !app.status_msg.is_empty(),
            "should show status feedback after axis change"
        );
    }

    // ── Panel colon bindings ────────────────────────────────────────────

    #[test]
    fn category_panel_colon_enters_command_mode() {
        let mut app = two_col_model();
        app.mode = AppMode::CategoryPanel;

        app.handle_key(KeyEvent::new(KeyCode::Char(':'), KeyModifiers::NONE))
            .unwrap();
        assert!(
            matches!(app.mode, AppMode::CommandMode { .. }),
            "colon in CategoryPanel should enter CommandMode, got {:?}",
            app.mode
        );
    }

    #[test]
    fn view_panel_colon_enters_command_mode() {
        let mut app = two_col_model();
        app.mode = AppMode::ViewPanel;

        app.handle_key(KeyEvent::new(KeyCode::Char(':'), KeyModifiers::NONE))
            .unwrap();
        assert!(
            matches!(app.mode, AppMode::CommandMode { .. }),
            "colon in ViewPanel should enter CommandMode, got {:?}",
            app.mode
        );
    }

    #[test]
    fn tile_select_colon_enters_command_mode() {
        let mut app = two_col_model();
        app.mode = AppMode::TileSelect;

        app.handle_key(KeyEvent::new(KeyCode::Char(':'), KeyModifiers::NONE))
            .unwrap();
        assert!(
            matches!(app.mode, AppMode::CommandMode { .. }),
            "colon in TileSelect should enter CommandMode, got {:?}",
            app.mode
        );
    }
}