//! Select/Dropdown widget for zcatui.
//!
//! Provides dropdown selection from a list of options.
//!
//! ## Example
//!
//! ```zig
//! var select = Select.init(&.{"Option 1", "Option 2", "Option 3"})
//!     .setPlaceholder("Choose an option...")
//!     .setSelected(0);
//!
//! // Toggle dropdown
//! if (event.key.code == .enter) {
//!     select.toggle();
//! }
//!
//! select.render(area, buf);
//! ```

const std = @import("std");
const buffer_mod = @import("../buffer.zig");
const Buffer = buffer_mod.Buffer;
const Rect = buffer_mod.Rect;
const style_mod = @import("../style.zig");
const Style = style_mod.Style;
const Color = style_mod.Color;
const block_mod = @import("block.zig");
const Block = block_mod.Block;
const Borders = block_mod.Borders;

// ============================================================================
// Select
// ============================================================================

/// A dropdown select widget.
pub const Select = struct {
    /// Available options.
    options: []const []const u8,

    /// Currently selected index (null = none).
    selected: ?usize = null,

    /// Highlighted index when open.
    highlighted: usize = 0,

    /// Whether dropdown is open.
    open: bool = false,

    /// Whether focused.
    focused: bool = false,

    /// Whether disabled.
    disabled: bool = false,

    /// Placeholder text when nothing selected.
    placeholder: []const u8 = "Select...",

    /// Maximum visible items when open.
    max_visible: u16 = 8,

    /// Scroll offset when list is long.
    scroll_offset: usize = 0,

    /// Base style.
    style: Style = Style.default,

    /// Focused style.
    focused_style: Style = Style.default.fg(Color.cyan),

    /// Selected option style.
    selected_style: Style = Style.default.bg(Color.blue).fg(Color.white),

    /// Disabled style.
    disabled_style: Style = Style.default.fg(Color.indexed(8)),

    /// Dropdown arrow.
    arrow_down: []const u8 = "▼",
    arrow_up: []const u8 = "▲",

    /// Creates a new select.
    pub fn init(options: []const []const u8) Select {
        return .{
            .options = options,
        };
    }

    /// Sets placeholder text.
    pub fn setPlaceholder(self: Select, placeholder: []const u8) Select {
        var s = self;
        s.placeholder = placeholder;
        return s;
    }

    /// Sets selected index.
    pub fn setSelected(self: Select, index: ?usize) Select {
        var s = self;
        if (index) |i| {
            if (i < self.options.len) {
                s.selected = i;
            }
        } else {
            s.selected = null;
        }
        return s;
    }

    /// Sets focused state.
    pub fn setFocused(self: Select, focused: bool) Select {
        var s = self;
        s.focused = focused;
        return s;
    }

    /// Sets max visible items.
    pub fn setMaxVisible(self: Select, max: u16) Select {
        var s = self;
        s.max_visible = max;
        return s;
    }

    /// Opens the dropdown.
    pub fn openDropdown(self: *Select) void {
        if (!self.disabled and self.options.len > 0) {
            self.open = true;
            self.highlighted = self.selected orelse 0;
            self.adjustScroll();
        }
    }

    /// Closes the dropdown.
    pub fn close(self: *Select) void {
        self.open = false;
    }

    /// Toggles the dropdown.
    pub fn toggle(self: *Select) void {
        if (self.open) {
            self.close();
        } else {
            self.openDropdown();
        }
    }

    /// Moves highlight up.
    pub fn highlightPrev(self: *Select) void {
        if (!self.open or self.options.len == 0) return;

        if (self.highlighted > 0) {
            self.highlighted -= 1;
        } else {
            self.highlighted = self.options.len - 1;
        }
        self.adjustScroll();
    }

    /// Moves highlight down.
    pub fn highlightNext(self: *Select) void {
        if (!self.open or self.options.len == 0) return;

        self.highlighted = (self.highlighted + 1) % self.options.len;
        self.adjustScroll();
    }

    /// Confirms current highlight as selection.
    pub fn confirm(self: *Select) void {
        if (self.open and self.highlighted < self.options.len) {
            self.selected = self.highlighted;
            self.close();
        }
    }

    /// Gets selected option text.
    pub fn getSelectedText(self: Select) ?[]const u8 {
        if (self.selected) |i| {
            if (i < self.options.len) {
                return self.options[i];
            }
        }
        return null;
    }

    /// Adjusts scroll to keep highlighted visible.
    fn adjustScroll(self: *Select) void {
        if (self.highlighted < self.scroll_offset) {
            self.scroll_offset = self.highlighted;
        } else if (self.highlighted >= self.scroll_offset + self.max_visible) {
            self.scroll_offset = self.highlighted - self.max_visible + 1;
        }
    }

    /// Gets the dropdown area.
    pub fn getDropdownArea(self: Select, trigger_area: Rect) Rect {
        const visible_count: u16 = @intCast(@min(self.options.len, self.max_visible));
        return Rect.init(
            trigger_area.x,
            trigger_area.y + 1,
            trigger_area.width,
            visible_count + 2, // +2 for border
        );
    }

    /// Renders the select widget.
    pub fn render(self: *Select, area: Rect, buf: *Buffer) void {
        if (area.width < 5 or area.height == 0) return;

        // Render trigger
        self.renderTrigger(area, buf);

        // Render dropdown if open
        if (self.open) {
            self.renderDropdown(area, buf);
        }
    }

    fn renderTrigger(self: *Select, area: Rect, buf: *Buffer) void {
        // Determine style
        var trigger_style = self.style;
        if (self.disabled) {
            trigger_style = self.disabled_style;
        } else if (self.focused) {
            trigger_style = self.focused_style;
        }

        // Border
        const block = Block.init()
            .setBorders(Borders.all)
            .style(trigger_style);
        block.render(Rect.init(area.x, area.y, area.width, 3), buf);

        // Text
        const inner = block.inner(Rect.init(area.x, area.y, area.width, 3));
        const text = self.getSelectedText() orelse self.placeholder;
        const text_style = if (self.selected == null and !self.disabled)
            Style.default.fg(Color.indexed(8))
        else
            trigger_style;

        const max_text = inner.width -| 2; // Space for arrow
        const text_len = @min(text.len, max_text);
        _ = buf.setString(inner.x, inner.y, text[0..text_len], text_style);

        // Arrow
        const arrow = if (self.open) self.arrow_up else self.arrow_down;
        _ = buf.setString(inner.x + inner.width - 1, inner.y, arrow, trigger_style);
    }

    fn renderDropdown(self: *Select, trigger_area: Rect, buf: *Buffer) void {
        const dropdown_area = self.getDropdownArea(trigger_area);

        // Background
        const block = Block.init()
            .setBorders(Borders.all)
            .style(self.style);
        block.render(dropdown_area, buf);

        // Fill background
        const inner = block.inner(dropdown_area);
        var y = inner.y;
        while (y < inner.y + inner.height) : (y += 1) {
            var x = inner.x;
            while (x < inner.x + inner.width) : (x += 1) {
                if (buf.getCell(x, y)) |cell| {
                    cell.setChar(' ');
                    cell.setStyle(self.style);
                }
            }
        }

        // Render visible options
        const visible_count = @min(self.options.len - self.scroll_offset, self.max_visible);
        y = inner.y;

        for (0..visible_count) |i| {
            const option_idx = self.scroll_offset + i;
            if (option_idx >= self.options.len) break;

            const option = self.options[option_idx];
            const is_highlighted = option_idx == self.highlighted;
            const is_selected = self.selected != null and option_idx == self.selected.?;

            var option_style = self.style;
            if (is_highlighted) {
                option_style = self.selected_style;
                // Fill line background
                var x = inner.x;
                while (x < inner.x + inner.width) : (x += 1) {
                    if (buf.getCell(x, y)) |cell| {
                        cell.setStyle(option_style);
                    }
                }
            }

            // Selected indicator
            const prefix: []const u8 = if (is_selected) "● " else "  ";
            const x = buf.setString(inner.x, y, prefix, option_style);

            // Option text
            const max_text = inner.width -| 2;
            const text_len = @min(option.len, max_text);
            _ = buf.setString(x, y, option[0..text_len], option_style);

            y += 1;
        }

        // Scroll indicators
        if (self.scroll_offset > 0) {
            _ = buf.setString(inner.x + inner.width - 1, inner.y, "↑", self.style);
        }
        if (self.scroll_offset + visible_count < self.options.len) {
            _ = buf.setString(inner.x + inner.width - 1, inner.y + inner.height - 1, "↓", self.style);
        }
    }
};

// ============================================================================
// MultiSelect
// ============================================================================

/// A multi-select dropdown widget.
pub const MultiSelect = struct {
    /// Available options.
    options: []const []const u8,

    /// Selected indices (bitmask for up to 64 options).
    selected: u64 = 0,

    /// Highlighted index when open.
    highlighted: usize = 0,

    /// Whether dropdown is open.
    open: bool = false,

    /// Whether focused.
    focused: bool = false,

    /// Whether disabled.
    disabled: bool = false,

    /// Placeholder text.
    placeholder: []const u8 = "Select...",

    /// Max visible items.
    max_visible: u16 = 8,

    /// Scroll offset.
    scroll_offset: usize = 0,

    /// Styles.
    style: Style = Style.default,
    focused_style: Style = Style.default.fg(Color.cyan),
    selected_style: Style = Style.default.bg(Color.blue).fg(Color.white),

    /// Creates a new multi-select.
    pub fn init(options: []const []const u8) MultiSelect {
        return .{
            .options = options,
        };
    }

    /// Checks if option is selected.
    pub fn isSelected(self: MultiSelect, index: usize) bool {
        if (index >= 64) return false;
        return (self.selected & (@as(u64, 1) << @intCast(index))) != 0;
    }

    /// Toggles option selection.
    pub fn toggleOption(self: *MultiSelect, index: usize) void {
        if (index >= 64 or self.disabled) return;
        const mask = @as(u64, 1) << @intCast(index);
        self.selected ^= mask;
    }

    /// Toggles highlighted option.
    pub fn toggleHighlighted(self: *MultiSelect) void {
        self.toggleOption(self.highlighted);
    }

    /// Opens dropdown.
    pub fn openDropdown(self: *MultiSelect) void {
        if (!self.disabled and self.options.len > 0) {
            self.open = true;
        }
    }

    /// Closes dropdown.
    pub fn close(self: *MultiSelect) void {
        self.open = false;
    }

    /// Toggles dropdown.
    pub fn toggle(self: *MultiSelect) void {
        if (self.open) {
            self.close();
        } else {
            self.openDropdown();
        }
    }

    /// Moves highlight up.
    pub fn highlightPrev(self: *MultiSelect) void {
        if (!self.open or self.options.len == 0) return;
        if (self.highlighted > 0) {
            self.highlighted -= 1;
        } else {
            self.highlighted = self.options.len - 1;
        }
    }

    /// Moves highlight down.
    pub fn highlightNext(self: *MultiSelect) void {
        if (!self.open or self.options.len == 0) return;
        self.highlighted = (self.highlighted + 1) % self.options.len;
    }

    /// Gets count of selected options.
    pub fn getSelectedCount(self: MultiSelect) usize {
        return @popCount(self.selected);
    }

    /// Renders the multi-select.
    pub fn render(self: *MultiSelect, area: Rect, buf: *Buffer) void {
        if (area.width < 5 or area.height == 0) return;

        // Render trigger
        var trigger_style = self.style;
        if (self.focused) trigger_style = self.focused_style;

        const block = Block.init()
            .setBorders(Borders.all)
            .style(trigger_style);
        block.render(Rect.init(area.x, area.y, area.width, 3), buf);

        const inner = block.inner(Rect.init(area.x, area.y, area.width, 3));

        // Display text
        const count = self.getSelectedCount();
        var text_buf: [64]u8 = undefined;
        const text = if (count == 0)
            self.placeholder
        else blk: {
            const result = std.fmt.bufPrint(&text_buf, "{d} selected", .{count}) catch self.placeholder;
            break :blk result;
        };

        _ = buf.setString(inner.x, inner.y, text, trigger_style);
        _ = buf.setString(inner.x + inner.width - 1, inner.y, if (self.open) "▲" else "▼", trigger_style);

        // Dropdown
        if (self.open) {
            const dropdown_y = area.y + 3;
            const visible: u16 = @intCast(@min(self.options.len, self.max_visible));
            const dropdown_area = Rect.init(area.x, dropdown_y, area.width, visible + 2);

            const dd_block = Block.init().setBorders(Borders.all).style(self.style);
            dd_block.render(dropdown_area, buf);

            const dd_inner = dd_block.inner(dropdown_area);
            var y = dd_inner.y;

            for (self.options, 0..) |option, i| {
                if (y >= dd_inner.y + dd_inner.height) break;

                const is_sel = self.isSelected(i);
                const is_hl = i == self.highlighted;

                var opt_style = self.style;
                if (is_hl) {
                    opt_style = self.selected_style;
                    var x = dd_inner.x;
                    while (x < dd_inner.x + dd_inner.width) : (x += 1) {
                        if (buf.getCell(x, y)) |cell| {
                            cell.setStyle(opt_style);
                        }
                    }
                }

                const check: []const u8 = if (is_sel) "[x] " else "[ ] ";
                const x = buf.setString(dd_inner.x, y, check, opt_style);

                const max_text = dd_inner.width -| 4;
                const text_len = @min(option.len, max_text);
                _ = buf.setString(x, y, option[0..text_len], opt_style);

                y += 1;
            }
        }
    }
};

// ============================================================================
// Tests
// ============================================================================

test "Select basic" {
    var sel = Select.init(&.{ "A", "B", "C" });

    try std.testing.expectEqual(@as(?usize, null), sel.selected);
    try std.testing.expect(!sel.open);

    sel.openDropdown();
    try std.testing.expect(sel.open);

    sel.highlightNext();
    sel.confirm();
    try std.testing.expectEqual(@as(?usize, 1), sel.selected);
    try std.testing.expect(!sel.open);
}

test "Select getSelectedText" {
    var sel = Select.init(&.{ "Apple", "Banana", "Cherry" }).setSelected(1);

    try std.testing.expectEqualStrings("Banana", sel.getSelectedText().?);
}

test "MultiSelect" {
    var ms = MultiSelect.init(&.{ "A", "B", "C", "D" });

    try std.testing.expectEqual(@as(usize, 0), ms.getSelectedCount());

    ms.toggleOption(0);
    ms.toggleOption(2);

    try std.testing.expect(ms.isSelected(0));
    try std.testing.expect(!ms.isSelected(1));
    try std.testing.expect(ms.isSelected(2));
    try std.testing.expectEqual(@as(usize, 2), ms.getSelectedCount());
}