//! Selectable Widget - Clickable/selectable region
//!
//! A region that can be clicked and selected, with hover feedback.
//! Used for building custom interactive components.

const std = @import("std");
const Context = @import("../core/context.zig").Context;
const Command = @import("../core/command.zig");
const Layout = @import("../core/layout.zig");
const Style = @import("../core/style.zig");
const Input = @import("../core/input.zig");

/// Selection mode
pub const SelectionMode = enum {
    /// Single selection (click toggles)
    single,
    /// Multi-selection (shift+click, ctrl+click)
    multi,
    /// Required selection (always has one selected)
    required,
};

/// Selectable state
pub const State = struct {
    /// Is currently selected
    is_selected: bool = false,
    /// Is currently focused
    is_focused: bool = false,
    /// Is being pressed
    is_pressed: bool = false,

    pub fn init() State {
        return .{};
    }

    pub fn select(self: *State) void {
        self.is_selected = true;
    }

    pub fn deselect(self: *State) void {
        self.is_selected = false;
    }

    pub fn toggle(self: *State) void {
        self.is_selected = !self.is_selected;
    }
};

/// Selectable configuration
pub const Config = struct {
    /// Selection mode
    mode: SelectionMode = .single,
    /// Disabled state
    disabled: bool = false,
    /// Show selection indicator
    show_indicator: bool = true,
    /// Show focus ring
    show_focus: bool = true,
    /// Padding around content
    padding: u16 = 8,
    /// Border radius (visual hint)
    rounded: bool = true,
};

/// Selectable colors
pub const Colors = struct {
    /// Normal background
    background: Style.Color = Style.Color.rgba(0, 0, 0, 0),
    /// Hover background
    hover: Style.Color = Style.Color.rgba(255, 255, 255, 15),
    /// Pressed background
    pressed: Style.Color = Style.Color.rgba(255, 255, 255, 25),
    /// Selected background
    selected: Style.Color = Style.Color.rgba(66, 133, 244, 30),
    /// Selection indicator
    indicator: Style.Color = Style.Color.rgb(66, 133, 244),
    /// Focus ring
    focus: Style.Color = Style.Color.rgb(66, 133, 244),
    /// Disabled overlay
    disabled: Style.Color = Style.Color.rgba(128, 128, 128, 80),

    pub fn fromTheme(theme: Style.Theme) Colors {
        return .{
            .background = Style.Color.transparent,
            .hover = theme.foreground.withAlpha(15),
            .pressed = theme.foreground.withAlpha(25),
            .selected = theme.primary.withAlpha(30),
            .indicator = theme.primary,
            .focus = theme.primary,
            .disabled = Style.Color.rgba(128, 128, 128, 80),
        };
    }
};

/// Selectable result
pub const Result = struct {
    /// Was clicked this frame
    clicked: bool,
    /// Is hovered
    hovered: bool,
    /// Is selected
    selected: bool,
    /// Is focused
    focused: bool,
    /// Content area (inside padding)
    content_rect: Layout.Rect,
    /// Total bounds
    bounds: Layout.Rect,
};

/// Simple selectable region
pub fn selectable(ctx: *Context, state: *State) Result {
    return selectableEx(ctx, state, .{}, .{});
}

/// Selectable with configuration
pub fn selectableEx(ctx: *Context, state: *State, config: Config, colors: Colors) Result {
    const rect = ctx.layout.nextRect();
    return selectableRect(ctx, rect, state, config, colors);
}

/// Selectable in specific rectangle
pub fn selectableRect(
    ctx: *Context,
    bounds: Layout.Rect,
    state: *State,
    config: Config,
    colors: Colors,
) Result {
    if (bounds.isEmpty()) {
        return .{
            .clicked = false,
            .hovered = false,
            .selected = state.is_selected,
            .focused = state.is_focused,
            .content_rect = Layout.Rect{ .x = 0, .y = 0, .w = 0, .h = 0 },
            .bounds = bounds,
        };
    }

    // Mouse interaction
    const mouse = ctx.input.mousePos();
    const hovered = bounds.contains(mouse.x, mouse.y) and !config.disabled;
    const pressed = hovered and ctx.input.mousePressed(.left);
    const released = hovered and ctx.input.mouseReleased(.left);

    state.is_pressed = pressed;

    var clicked = false;

    // Handle click
    if (released and !config.disabled) {
        clicked = true;

        switch (config.mode) {
            .single => state.toggle(),
            .multi => state.toggle(), // Multi handled externally with modifiers
            .required => state.select(),
        }
    }

    // Determine background color
    var bg_color = colors.background;
    if (state.is_selected) {
        bg_color = colors.selected;
    }
    if (hovered and !state.is_pressed) {
        bg_color = if (state.is_selected)
            blendColors(colors.selected, colors.hover)
        else
            colors.hover;
    }
    if (state.is_pressed) {
        bg_color = colors.pressed;
    }

    // Draw background
    if (bg_color.a > 0) {
        ctx.pushCommand(Command.rect(bounds.x, bounds.y, bounds.w, bounds.h, bg_color));
    }

    // Draw selection indicator
    if (config.show_indicator and state.is_selected) {
        ctx.pushCommand(Command.rect(bounds.x, bounds.y, 3, bounds.h, colors.indicator));
    }

    // Draw focus ring
    if (config.show_focus and state.is_focused) {
        ctx.pushCommand(Command.rectOutline(
            bounds.x - 1,
            bounds.y - 1,
            bounds.w + 2,
            bounds.h + 2,
            colors.focus,
        ));
    }

    // Draw disabled overlay
    if (config.disabled) {
        ctx.pushCommand(Command.rect(bounds.x, bounds.y, bounds.w, bounds.h, colors.disabled));
    }

    // Calculate content rect
    const padding = @as(i32, @intCast(config.padding));
    const content_rect = Layout.Rect{
        .x = bounds.x + padding,
        .y = bounds.y + padding,
        .w = bounds.w -| @as(u32, @intCast(config.padding * 2)),
        .h = bounds.h -| @as(u32, @intCast(config.padding * 2)),
    };

    return .{
        .clicked = clicked,
        .hovered = hovered,
        .selected = state.is_selected,
        .focused = state.is_focused,
        .content_rect = content_rect,
        .bounds = bounds,
    };
}

/// Simple color blending (overlay)
fn blendColors(base: Style.Color, overlay: Style.Color) Style.Color {
    const alpha = @as(f32, @floatFromInt(overlay.a)) / 255.0;
    const inv_alpha = 1.0 - alpha;

    return Style.Color.rgba(
        @intFromFloat(@as(f32, @floatFromInt(base.r)) * inv_alpha + @as(f32, @floatFromInt(overlay.r)) * alpha),
        @intFromFloat(@as(f32, @floatFromInt(base.g)) * inv_alpha + @as(f32, @floatFromInt(overlay.g)) * alpha),
        @intFromFloat(@as(f32, @floatFromInt(base.b)) * inv_alpha + @as(f32, @floatFromInt(overlay.b)) * alpha),
        @max(base.a, overlay.a),
    );
}

// =============================================================================
// Group selection helpers
// =============================================================================

/// Selection group for managing multiple selectables
pub const SelectionGroup = struct {
    /// Selected indices
    selected: std.ArrayListUnmanaged(usize),
    /// Selection mode
    mode: SelectionMode,
    /// Allocator
    allocator: std.mem.Allocator,

    pub fn init(allocator: std.mem.Allocator, mode: SelectionMode) SelectionGroup {
        return .{
            .selected = .{},
            .mode = mode,
            .allocator = allocator,
        };
    }

    pub fn deinit(self: *SelectionGroup) void {
        self.selected.deinit(self.allocator);
    }

    pub fn isSelected(self: *const SelectionGroup, index: usize) bool {
        for (self.selected.items) |sel| {
            if (sel == index) return true;
        }
        return false;
    }

    pub fn select(self: *SelectionGroup, index: usize) !void {
        switch (self.mode) {
            .single, .required => {
                self.selected.clearRetainingCapacity();
                try self.selected.append(self.allocator, index);
            },
            .multi => {
                if (!self.isSelected(index)) {
                    try self.selected.append(self.allocator, index);
                }
            },
        }
    }

    pub fn deselect(self: *SelectionGroup, index: usize) void {
        if (self.mode == .required and self.selected.items.len <= 1) {
            return; // Can't deselect last item in required mode
        }

        for (self.selected.items, 0..) |sel, i| {
            if (sel == index) {
                _ = self.selected.orderedRemove(i);
                break;
            }
        }
    }

    pub fn toggle(self: *SelectionGroup, index: usize) !void {
        if (self.isSelected(index)) {
            self.deselect(index);
        } else {
            try self.select(index);
        }
    }

    pub fn clear(self: *SelectionGroup) void {
        if (self.mode != .required) {
            self.selected.clearRetainingCapacity();
        }
    }
};

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

test "selectable state" {
    var state = State.init();
    try std.testing.expect(!state.is_selected);

    state.toggle();
    try std.testing.expect(state.is_selected);

    state.deselect();
    try std.testing.expect(!state.is_selected);

    state.select();
    try std.testing.expect(state.is_selected);
}

test "selectable generates commands" {
    var ctx = try Context.init(std.testing.allocator, 800, 600);
    defer ctx.deinit();

    var state = State.init();

    ctx.beginFrame();
    ctx.layout.row_height = 40;

    const result = selectable(&ctx, &state);

    try std.testing.expect(!result.clicked);
    try std.testing.expect(!result.selected);

    ctx.endFrame();
}

test "selectable selected state" {
    var ctx = try Context.init(std.testing.allocator, 800, 600);
    defer ctx.deinit();

    var state = State.init();
    state.is_selected = true;

    ctx.beginFrame();
    ctx.layout.row_height = 40;

    const result = selectableEx(&ctx, &state, .{
        .show_indicator = true,
    }, .{});

    try std.testing.expect(result.selected);
    // Should have background + indicator commands
    try std.testing.expect(ctx.commands.items.len >= 2);

    ctx.endFrame();
}

test "selection group single mode" {
    var group = SelectionGroup.init(std.testing.allocator, .single);
    defer group.deinit();

    try group.select(0);
    try std.testing.expect(group.isSelected(0));

    try group.select(1);
    try std.testing.expect(!group.isSelected(0)); // Previous deselected
    try std.testing.expect(group.isSelected(1));
}

test "selection group multi mode" {
    var group = SelectionGroup.init(std.testing.allocator, .multi);
    defer group.deinit();

    try group.select(0);
    try group.select(1);
    try group.select(2);

    try std.testing.expect(group.isSelected(0));
    try std.testing.expect(group.isSelected(1));
    try std.testing.expect(group.isSelected(2));

    group.deselect(1);
    try std.testing.expect(!group.isSelected(1));
}

test "selection group required mode" {
    var group = SelectionGroup.init(std.testing.allocator, .required);
    defer group.deinit();

    try group.select(0);
    try std.testing.expect(group.isSelected(0));

    // Can't deselect in required mode with only one selection
    group.deselect(0);
    try std.testing.expect(group.isSelected(0)); // Still selected
}