//! Dropdown selection control
//!
//! Renders as: `Label: [Selected Option ▼]`
//!
//! This module provides a complete dropdown component with:
//! - State management (`DropdownState`)
//! - Rendering (`render_dropdown`, `render_dropdown_aligned`)
//! - Input handling (`DropdownState::handle_mouse`, `handle_key`)
//! - Layout/hit testing (`DropdownLayout`)

mod input;
mod render;

use ratatui::layout::Rect;
use ratatui::style::Color;

pub use input::DropdownEvent;
pub use render::{render_dropdown, render_dropdown_aligned};

use super::FocusState;

/// State for a dropdown control
#[derive(Debug, Clone)]
pub struct DropdownState {
    /// Currently selected index
    pub selected: usize,
    /// Display names for options (shown in UI)
    pub options: Vec<String>,
    /// Actual values for options (stored in config)
    /// If empty, options are used as values
    pub values: Vec<String>,
    /// Label displayed before the dropdown
    pub label: String,
    /// Whether the dropdown is currently open
    pub open: bool,
    /// Focus state
    pub focus: FocusState,
    /// Original selection when dropdown opened (for cancel/restore)
    original_selected: Option<usize>,
    /// Scroll offset for long option lists
    pub scroll_offset: usize,
    /// Maximum visible options (set during render)
    pub max_visible: usize,
}

impl DropdownState {
    /// Create a new dropdown state where display names equal values
    pub fn new(options: Vec<String>, label: impl Into<String>) -> Self {
        Self {
            selected: 0,
            options,
            values: Vec::new(),
            label: label.into(),
            open: false,
            focus: FocusState::Normal,
            original_selected: None,
            scroll_offset: 0,
            max_visible: 5, // Conservative default to ensure visibility
        }
    }

    /// Create a dropdown with separate display names and values
    pub fn with_values(
        options: Vec<String>,
        values: Vec<String>,
        label: impl Into<String>,
    ) -> Self {
        debug_assert_eq!(options.len(), values.len());
        Self {
            selected: 0,
            options,
            values,
            label: label.into(),
            open: false,
            focus: FocusState::Normal,
            original_selected: None,
            scroll_offset: 0,
            max_visible: 5, // Conservative default to ensure visibility
        }
    }

    /// Set the initially selected index
    pub fn with_selected(mut self, index: usize) -> Self {
        if index < self.options.len() {
            self.selected = index;
        }
        self
    }

    /// Set the focus state
    pub fn with_focus(mut self, focus: FocusState) -> Self {
        self.focus = focus;
        self
    }

    /// Check if the control is enabled
    pub fn is_enabled(&self) -> bool {
        self.focus != FocusState::Disabled
    }

    /// Get the currently selected value (for storing in config)
    pub fn selected_value(&self) -> Option<&str> {
        if self.values.is_empty() {
            self.options.get(self.selected).map(|s| s.as_str())
        } else {
            self.values.get(self.selected).map(|s| s.as_str())
        }
    }

    /// Get the currently selected display name (for UI)
    pub fn selected_option(&self) -> Option<&str> {
        self.options.get(self.selected).map(|s| s.as_str())
    }

    /// Find the index of a value
    pub fn index_of_value(&self, value: &str) -> Option<usize> {
        if self.values.is_empty() {
            self.options.iter().position(|o| o == value)
        } else {
            self.values.iter().position(|v| v == value)
        }
    }

    /// Toggle the dropdown open/closed
    pub fn toggle_open(&mut self) {
        if self.is_enabled() {
            if !self.open {
                self.original_selected = Some(self.selected);
            } else {
                self.original_selected = None;
            }
            self.open = !self.open;
        }
    }

    /// Cancel the dropdown (restore original selection and close)
    pub fn cancel(&mut self) {
        if let Some(original) = self.original_selected.take() {
            self.selected = original;
        }
        self.open = false;
    }

    /// Confirm the selection and close
    pub fn confirm(&mut self) {
        self.original_selected = None;
        self.open = false;
    }

    /// Select the next option
    pub fn select_next(&mut self) {
        if self.is_enabled() && !self.options.is_empty() {
            self.selected = (self.selected + 1) % self.options.len();
            self.ensure_visible();
        }
    }

    /// Select the previous option
    pub fn select_prev(&mut self) {
        if self.is_enabled() && !self.options.is_empty() {
            self.selected = if self.selected == 0 {
                self.options.len() - 1
            } else {
                self.selected - 1
            };
            self.ensure_visible();
        }
    }

    /// Select an option by index
    pub fn select(&mut self, index: usize) {
        if self.is_enabled() && index < self.options.len() {
            self.selected = index;
            self.original_selected = None;
            self.open = false;
        }
    }

    /// Ensure the selected item is visible within the scroll view
    pub fn ensure_visible(&mut self) {
        if self.max_visible == 0 || self.options.len() <= self.max_visible {
            self.scroll_offset = 0;
            return;
        }

        // If selected is above visible area, scroll up
        if self.selected < self.scroll_offset {
            self.scroll_offset = self.selected;
        }
        // If selected is below visible area, scroll down
        else if self.selected >= self.scroll_offset + self.max_visible {
            self.scroll_offset = self.selected.saturating_sub(self.max_visible - 1);
        }
    }

    /// Scroll the dropdown by a delta (positive = down, negative = up)
    pub fn scroll_by(&mut self, delta: i32) {
        if self.options.len() <= self.max_visible {
            return;
        }

        let max_offset = self.options.len().saturating_sub(self.max_visible);
        if delta > 0 {
            self.scroll_offset = (self.scroll_offset + delta as usize).min(max_offset);
        } else {
            self.scroll_offset = self.scroll_offset.saturating_sub((-delta) as usize);
        }
    }

    /// Check if scrollbar should be shown
    pub fn needs_scrollbar(&self) -> bool {
        self.open && self.options.len() > self.max_visible
    }

    /// Get the scroll position as a fraction (0.0 to 1.0) for scrollbar rendering
    pub fn scroll_fraction(&self) -> f32 {
        if self.options.len() <= self.max_visible {
            return 0.0;
        }
        let max_offset = self.options.len().saturating_sub(self.max_visible);
        if max_offset == 0 {
            return 0.0;
        }
        self.scroll_offset as f32 / max_offset as f32
    }
}

/// Colors for the dropdown control
#[derive(Debug, Clone, Copy)]
pub struct DropdownColors {
    /// Label color
    pub label: Color,
    /// Selected option text color
    pub selected: Color,
    /// Border/bracket color
    pub border: Color,
    /// Arrow indicator color
    pub arrow: Color,
    /// Option text in dropdown menu
    pub option: Color,
    /// Highlighted option background
    pub highlight_bg: Color,
    /// Focused highlight color
    pub focused: Color,
    /// Disabled color
    pub disabled: Color,
}

impl Default for DropdownColors {
    fn default() -> Self {
        Self {
            label: Color::White,
            selected: Color::Cyan,
            border: Color::Gray,
            arrow: Color::DarkGray,
            option: Color::White,
            highlight_bg: Color::DarkGray,
            focused: Color::Cyan,
            disabled: Color::DarkGray,
        }
    }
}

impl DropdownColors {
    /// Create colors from theme
    pub fn from_theme(theme: &crate::view::theme::Theme) -> Self {
        Self {
            label: theme.editor_fg,
            // Use editor_fg for selected value to ensure visibility
            // menu_active_fg can be hard to see against some backgrounds
            selected: theme.editor_fg,
            border: theme.line_number_fg,
            arrow: theme.line_number_fg,
            option: theme.editor_fg,
            highlight_bg: theme.selection_bg,
            // Use menu_highlight_fg for focus indicator (bright, visible color)
            focused: theme.menu_highlight_fg,
            disabled: theme.line_number_fg,
        }
    }
}

/// Layout information returned after rendering for hit testing
#[derive(Debug, Clone, Default)]
pub struct DropdownLayout {
    /// The main dropdown button area
    pub button_area: Rect,
    /// Areas for each option when open (empty if closed)
    pub option_areas: Vec<Rect>,
    /// The full control area
    pub full_area: Rect,
    /// Scroll offset used during rendering (for mapping visible to actual indices)
    pub scroll_offset: usize,
}

impl DropdownLayout {
    /// Check if a point is on the dropdown button
    pub fn is_button(&self, x: u16, y: u16) -> bool {
        x >= self.button_area.x
            && x < self.button_area.x + self.button_area.width
            && y >= self.button_area.y
            && y < self.button_area.y + self.button_area.height
    }

    /// Get the option index at a point, if any
    /// Returns the actual option index (accounting for scroll offset)
    pub fn option_at(&self, x: u16, y: u16) -> Option<usize> {
        for (i, area) in self.option_areas.iter().enumerate() {
            if x >= area.x && x < area.x + area.width && y >= area.y && y < area.y + area.height {
                return Some(self.scroll_offset + i);
            }
        }
        None
    }

    /// Check if a point is within the full control area
    pub fn contains(&self, x: u16, y: u16) -> bool {
        x >= self.full_area.x
            && x < self.full_area.x + self.full_area.width
            && y >= self.full_area.y
            && y < self.full_area.y + self.full_area.height
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use ratatui::backend::TestBackend;
    use ratatui::Terminal;

    fn test_frame<F>(width: u16, height: u16, f: F)
    where
        F: FnOnce(&mut ratatui::Frame, Rect),
    {
        let backend = TestBackend::new(width, height);
        let mut terminal = Terminal::new(backend).unwrap();
        terminal
            .draw(|frame| {
                let area = Rect::new(0, 0, width, height);
                f(frame, area);
            })
            .unwrap();
    }

    #[test]
    fn test_dropdown_renders() {
        test_frame(40, 1, |frame, area| {
            let state = DropdownState::new(
                vec!["Option A".to_string(), "Option B".to_string()],
                "Choice",
            );
            let colors = DropdownColors::default();
            let layout = render_dropdown(frame, area, &state, &colors);

            assert!(layout.button_area.width > 0);
            assert!(layout.option_areas.is_empty());
        });
    }

    #[test]
    fn test_dropdown_open() {
        test_frame(40, 5, |frame, area| {
            let mut state = DropdownState::new(
                vec!["Option A".to_string(), "Option B".to_string()],
                "Choice",
            );
            state.open = true;
            let colors = DropdownColors::default();
            let layout = render_dropdown(frame, area, &state, &colors);

            assert_eq!(layout.option_areas.len(), 2);
        });
    }

    #[test]
    fn test_dropdown_selection() {
        let mut state = DropdownState::new(
            vec!["A".to_string(), "B".to_string(), "C".to_string()],
            "Test",
        );

        assert_eq!(state.selected, 0);
        state.select_next();
        assert_eq!(state.selected, 1);
        state.select_next();
        assert_eq!(state.selected, 2);
        state.select_next();
        assert_eq!(state.selected, 0);

        state.select_prev();
        assert_eq!(state.selected, 2);
    }

    #[test]
    fn test_dropdown_select_by_index() {
        let mut state = DropdownState::new(
            vec!["A".to_string(), "B".to_string(), "C".to_string()],
            "Test",
        );
        state.open = true;
        state.select(2);
        assert_eq!(state.selected, 2);
        assert!(!state.open);
    }

    #[test]
    fn test_dropdown_disabled() {
        let mut state = DropdownState::new(vec!["A".to_string(), "B".to_string()], "Test")
            .with_focus(FocusState::Disabled);

        state.toggle_open();
        assert!(!state.open);

        state.select_next();
        assert_eq!(state.selected, 0);
    }

    #[test]
    fn test_dropdown_cancel_restores_original() {
        let mut state = DropdownState::new(
            vec!["A".to_string(), "B".to_string(), "C".to_string()],
            "Test",
        )
        .with_selected(1);

        state.toggle_open();
        assert!(state.open);
        assert_eq!(state.selected, 1);

        state.select_next();
        assert_eq!(state.selected, 2);

        state.cancel();
        assert!(!state.open);
        assert_eq!(state.selected, 1);
    }

    #[test]
    fn test_dropdown_confirm_commits_selection() {
        let mut state = DropdownState::new(
            vec!["A".to_string(), "B".to_string(), "C".to_string()],
            "Test",
        )
        .with_selected(0);

        state.toggle_open();
        assert!(state.open);

        state.select_next();
        assert_eq!(state.selected, 1);

        state.confirm();
        assert!(!state.open);
        assert_eq!(state.selected, 1);
    }

    #[test]
    fn test_dropdown_toggle_close_confirms() {
        let mut state = DropdownState::new(
            vec!["A".to_string(), "B".to_string(), "C".to_string()],
            "Test",
        )
        .with_selected(0);

        state.toggle_open();
        assert!(state.open);

        state.select_next();
        assert_eq!(state.selected, 1);

        state.toggle_open();
        assert!(!state.open);
        assert_eq!(state.selected, 1);
    }

    #[test]
    fn test_dropdown_scrolling() {
        // Create dropdown with many options
        let options: Vec<String> = (0..20).map(|i| format!("Option {}", i)).collect();
        let mut state = DropdownState::new(options, "Long List");
        state.max_visible = 5; // Only show 5 options at a time

        assert_eq!(state.scroll_offset, 0);

        // Select option beyond visible area
        state.selected = 10;
        state.ensure_visible();

        // Should have scrolled down
        assert!(state.scroll_offset > 0);
        assert!(state.selected >= state.scroll_offset);
        assert!(state.selected < state.scroll_offset + state.max_visible);
    }

    #[test]
    fn test_dropdown_scroll_by() {
        let options: Vec<String> = (0..20).map(|i| format!("Option {}", i)).collect();
        let mut state = DropdownState::new(options, "Long List");
        state.max_visible = 5;

        // Scroll down
        state.scroll_by(3);
        assert_eq!(state.scroll_offset, 3);

        // Scroll up
        state.scroll_by(-2);
        assert_eq!(state.scroll_offset, 1);

        // Scroll up past beginning
        state.scroll_by(-10);
        assert_eq!(state.scroll_offset, 0);

        // Scroll down past end
        state.scroll_by(100);
        assert_eq!(state.scroll_offset, 15); // 20 - 5 = 15 max
    }

    #[test]
    fn test_dropdown_needs_scrollbar() {
        let options: Vec<String> = (0..10).map(|i| format!("Option {}", i)).collect();
        let mut state = DropdownState::new(options, "Test");

        // When closed, no scrollbar needed
        state.max_visible = 5;
        assert!(!state.needs_scrollbar());

        // When open with more options than visible, scrollbar needed
        state.open = true;
        assert!(state.needs_scrollbar());

        // When all options fit, no scrollbar needed
        state.max_visible = 20;
        assert!(!state.needs_scrollbar());
    }

    #[test]
    fn test_dropdown_keyboard_nav_scrolls() {
        let options: Vec<String> = (0..10).map(|i| format!("Option {}", i)).collect();
        let mut state = DropdownState::new(options, "Test");
        state.max_visible = 3;
        state.open = true;

        // Navigate down past visible area
        for _ in 0..5 {
            state.select_next();
        }

        assert_eq!(state.selected, 5);
        // Selected should be visible
        assert!(state.selected >= state.scroll_offset);
        assert!(state.selected < state.scroll_offset + state.max_visible);
    }

    #[test]
    fn test_dropdown_selection_always_visible() {
        // Simulate locale dropdown with 13 options and small viewport
        let options: Vec<String> = vec![
            "Auto-detect",
            "Czech",
            "German",
            "English",
            "Spanish",
            "French",
            "Japanese",
            "Korean",
            "Portuguese",
            "Russian",
            "Thai",
            "Ukrainian",
            "Chinese",
        ]
        .into_iter()
        .map(String::from)
        .collect();

        let mut state = DropdownState::new(options, "Locale");
        state.max_visible = 5; // Small viewport like in settings
        state.open = true;

        // Helper to check visibility invariant
        let check_visible = |state: &DropdownState| {
            assert!(
                state.selected >= state.scroll_offset,
                "selected {} below scroll_offset {}",
                state.selected,
                state.scroll_offset
            );
            assert!(
                state.selected < state.scroll_offset + state.max_visible,
                "selected {} above visible area (scroll_offset={}, max_visible={})",
                state.selected,
                state.scroll_offset,
                state.max_visible
            );
        };

        // Navigate all the way down
        for i in 0..12 {
            state.select_next();
            check_visible(&state);
            assert_eq!(state.selected, i + 1);
        }

        // Should be at last item
        assert_eq!(state.selected, 12);
        check_visible(&state);

        // Navigate all the way back up
        for i in (0..12).rev() {
            state.select_prev();
            check_visible(&state);
            assert_eq!(state.selected, i);
        }

        // Should be at first item
        assert_eq!(state.selected, 0);
        check_visible(&state);

        // Test Home key behavior
        state.selected = 8;
        state.ensure_visible();
        state.selected = 0;
        state.ensure_visible();
        check_visible(&state);

        // Test End key behavior
        state.selected = 12;
        state.ensure_visible();
        check_visible(&state);
    }
}
