use eframe::egui;
use egui::{Color32, DragValue, Rect, Stroke, vec2};

use crate::font::BitmapFont;
use kiln_core::game::FontSpec;

/// State for the font-picker dialog.
///
/// Holds the in-progress edit of font path and tile dimensions, and a loaded
/// preview font so the user can see the tilesheet before applying.
pub(crate) struct FontDialogState {
    /// Path string as edited by the user (may differ from the applied font).
    pub path: String,
    /// Tile width being edited.
    pub tile_w: u32,
    /// Tile height being edited.
    pub tile_h: u32,
    /// Loaded preview of the current path+dimensions, if valid.
    pub preview: Option<BitmapFont>,
}

impl FontDialogState {
    /// Creates dialog state pre-populated from an existing [`FontSpec`], or
    /// defaults (8×8, empty path) when there is no board-level font.
    pub(crate) fn from_spec(spec: Option<&FontSpec>) -> Self {
        match spec {
            Some(s) => Self {
                path: s.path.clone(),
                tile_w: s.tile_w,
                tile_h: s.tile_h,
                preview: None,
            },
            None => Self {
                path: String::new(),
                tile_w: 8,
                tile_h: 8,
                preview: None,
            },
        }
    }
}

/// Renders the floating font-picker dialog.
///
/// Lets the user choose a PNG file, set tile dimensions, preview the tilesheet
/// with grid lines, and apply the selection. When the user clicks "Apply",
/// `font_spec` is written and `open` is set to `false`.
pub(crate) fn show(
    ctx: &egui::Context,
    open: &mut bool,
    state: &mut FontDialogState,
    font_spec: &mut Option<FontSpec>,
) {
    let mut should_close = false;

    egui::Window::new("Font")
        .collapsible(false)
        .resizable(true)
        .open(open)
        .show(ctx, |ui| {
            // --- File chooser ---
            ui.horizontal(|ui| {
                ui.label("File:");
                ui.text_edit_singleline(&mut state.path);
                if ui.button("Browse…").clicked() {
                    if let Some(path) = rfd::FileDialog::new()
                        .add_filter("PNG image", &["png"])
                        .pick_file()
                    {
                        state.path = path.to_string_lossy().into_owned();
                        state.preview = None; // reload on next reload click
                    }
                }
            });

            // --- Tile dimensions ---
            ui.horizontal(|ui| {
                ui.label("Tile W:");
                if ui
                    .add(DragValue::new(&mut state.tile_w).range(1..=64))
                    .changed()
                {
                    state.preview = None;
                }
                ui.label("Tile H:");
                if ui
                    .add(DragValue::new(&mut state.tile_h).range(1..=64))
                    .changed()
                {
                    state.preview = None;
                }
                if ui.button("Load").clicked() {
                    state.preview = None;
                    if !state.path.is_empty() {
                        match BitmapFont::load(
                            ctx,
                            std::path::Path::new(&state.path),
                            state.tile_w,
                            state.tile_h,
                        ) {
                            Ok(f) => state.preview = Some(f),
                            Err(e) => eprintln!("font load error: {e}"),
                        }
                    }
                }
            });

            ui.separator();

            // --- Preview ---
            if let Some(font) = &state.preview {
                let tw = font.tile_w as f32;
                let th = font.tile_h as f32;
                let preview_size = vec2(font.img_w() as f32, font.img_h() as f32);

                egui::ScrollArea::both()
                    .max_width(400.0)
                    .max_height(200.0)
                    .id_salt("font_preview")
                    .show(ui, |ui| {
                        let (rect, _) = ui.allocate_exact_size(preview_size, egui::Sense::hover());
                        // Draw the full font texture.
                        ui.painter().image(
                            font.texture.id(),
                            rect,
                            Rect::from_min_max(egui::pos2(0.0, 0.0), egui::pos2(1.0, 1.0)),
                            Color32::WHITE,
                        );
                        // Overlay grid lines at tile boundaries.
                        let p = ui.painter();
                        let cols = font.tile_cols();
                        let rows = font.img_h() / font.tile_h;
                        let stroke =
                            Stroke::new(0.5, Color32::from_rgba_unmultiplied(255, 255, 0, 120));
                        for c in 0..=cols {
                            let x = rect.min.x + c as f32 * tw;
                            p.line_segment(
                                [egui::pos2(x, rect.min.y), egui::pos2(x, rect.max.y)],
                                stroke,
                            );
                        }
                        for r in 0..=rows {
                            let y = rect.min.y + r as f32 * th;
                            p.line_segment(
                                [egui::pos2(rect.min.x, y), egui::pos2(rect.max.x, y)],
                                stroke,
                            );
                        }
                    });
            } else {
                ui.label("(no preview — click Load after setting path and tile size)");
            }

            ui.separator();

            // --- Apply / Clear ---
            ui.horizontal(|ui| {
                let can_apply = state.preview.is_some();
                if ui
                    .add_enabled(can_apply, egui::Button::new("Apply"))
                    .clicked()
                {
                    *font_spec = Some(FontSpec {
                        path: state.path.clone(),
                        tile_w: state.tile_w,
                        tile_h: state.tile_h,
                    });
                    should_close = true;
                }
                if ui.button("Use default").clicked() {
                    *font_spec = None;
                    should_close = true;
                }
            });
        });

    if should_close {
        *open = false;
    }
}