//! After-capture review window.
//!
//! Performance design:
//! - Effects (rounded corners, drop shadow) run on a background thread so the
//!   UI never blocks. A `Receiver` is polled each frame; when the result
//!   arrives the texture is swapped out.
//! - A debounce timer (`dirty_since`) ensures we only spawn a new worker 150 ms
//!   after the last slider change, not on every incremental drag tick.
//! - The raw image is wrapped in Arc so it is shared with worker threads
//!   without cloning the pixel data.
//! - Texture uploads are guarded by MAX_TEX so we never panic on large images.

use std::path::PathBuf;
use std::sync::{Arc, mpsc};
use std::time::{Duration, Instant};

use arboard::{Clipboard, ImageData};
use eframe::egui::{self, Color32, ColorImage, Rounding, ScrollArea, Stroke, TextureHandle, TextureOptions, Vec2};
use image::RgbaImage;

use crate::{config::Config, effects::apply_effects};

const MAX_TEX: u32 = 2048;
/// How long to wait after the last setting change before spawning the worker.
const DEBOUNCE: Duration = Duration::from_millis(150);

#[derive(Debug)]
pub enum ReviewAction {
    #[allow(dead_code)] // path stored for future use (e.g. desktop notification)
    Saved(PathBuf),
    Copied,
    Discarded,
}

/// Channel message from the background effects worker.
struct EffectsResult(RgbaImage);

pub struct ReviewWindow {
    /// Full-resolution raw capture — shared with worker threads via Arc.
    raw_image: Arc<RgbaImage>,
    /// Last fully-processed preview (what gets saved/copied).
    preview_image: Arc<RgbaImage>,
    /// GPU texture (may be downscaled for display).
    preview_texture: TextureHandle,
    pub config: Config,
    save_as_path: String,
    status_message: Option<String>,
    pub action: Option<ReviewAction>,
    settings_open: bool,

    /// Set when settings change; cleared when a worker is spawned.
    dirty_since: Option<Instant>,
    /// Receives the processed image from the background worker.
    worker_rx: Option<mpsc::Receiver<EffectsResult>>,
    /// True while a worker is running.
    worker_running: bool,
}

impl ReviewWindow {
    pub fn new(cc: &eframe::CreationContext<'_>, raw_image: RgbaImage, config: Config) -> Self {
        let raw = Arc::new(raw_image);
        let preview = Arc::new(apply_effects((*raw).clone(), &config.effects));
        let texture = upload_texture(&cc.egui_ctx, &preview);
        let save_as_path = config.output_path().display().to_string();
        Self {
            raw_image: raw,
            preview_image: preview,
            preview_texture: texture,
            config,
            save_as_path,
            status_message: None,
            action: None,
            settings_open: false,
            dirty_since: None,
            worker_rx: None,
            worker_running: false,
        }
    }

    /// Mark settings as changed. A worker will be spawned after the debounce.
    fn mark_dirty(&mut self) {
        // Only reset the timer if we're not already waiting (avoids pushing
        // the debounce out indefinitely on fast slider drag).
        if self.dirty_since.is_none() {
            self.dirty_since = Some(Instant::now());
        }
    }

    /// Poll for a finished worker result and/or spawn a new one if due.
    fn tick_effects(&mut self, ctx: &egui::Context) {
        // 1. Check if the running worker is done.
        if let Some(rx) = &self.worker_rx {
            if let Ok(EffectsResult(img)) = rx.try_recv() {
                let img = Arc::new(img);
                self.preview_texture = upload_texture(ctx, &img);
                self.preview_image = img;
                self.worker_rx = None;
                self.worker_running = false;
            }
        }

        // 2. Spawn a new worker if debounce has elapsed and none is running.
        if let Some(since) = self.dirty_since {
            if !self.worker_running && since.elapsed() >= DEBOUNCE {
                self.dirty_since = None;
                self.worker_running = true;

                let raw = Arc::clone(&self.raw_image);
                let effects_cfg = self.config.effects.clone();
                let (tx, rx) = mpsc::channel();
                let ctx_clone = ctx.clone();

                std::thread::spawn(move || {
                    let result = apply_effects((*raw).clone(), &effects_cfg);
                    let _ = tx.send(EffectsResult(result));
                    // Wake the egui event loop so the new texture is picked up.
                    ctx_clone.request_repaint();
                });

                self.worker_rx = Some(rx);
            }

            // Keep repainting while waiting for the debounce to fire.
            if self.worker_running || self.dirty_since.is_some() {
                ctx.request_repaint_after(Duration::from_millis(50));
            }
        }
    }

    fn copy_to_clipboard(&mut self) {
        match Clipboard::new() {
            Ok(mut cb) => {
                let (w, h) = self.preview_image.dimensions();
                let bytes = self.preview_image.as_raw().clone();
                match cb.set_image(ImageData { width: w as usize, height: h as usize, bytes: bytes.into() }) {
                    Ok(_) => {
                        self.status_message = Some("Copied to clipboard.".into());
                        self.action = Some(ReviewAction::Copied);
                    }
                    Err(e) => self.status_message = Some(format!("Clipboard error: {e}")),
                }
            }
            Err(e) => self.status_message = Some(format!("Could not open clipboard: {e}")),
        }
    }

    fn save_to_path(&mut self, path: PathBuf) {
        if let Some(parent) = path.parent() {
            if let Err(e) = std::fs::create_dir_all(parent) {
                self.status_message = Some(format!("Could not create directory: {e}"));
                return;
            }
        }
        match self.preview_image.save(&path) {
            Ok(_) => {
                self.status_message = Some(format!("Saved to {}", path.display()));
                self.action = Some(ReviewAction::Saved(path));
            }
            Err(e) => self.status_message = Some(format!("Save error: {e}")),
        }
    }
}

impl eframe::App for ReviewWindow {
    fn update(&mut self, ctx: &egui::Context, _frame: &mut eframe::Frame) {
        self.tick_effects(ctx);

        // ── Global keybinds ───────────────────────────────────────────────────
        // Ctrl+C — copy to clipboard immediately.
        // Checked before any panel so it works regardless of widget focus.
        if ctx.input_mut(|i| i.consume_key(egui::Modifiers::CTRL, egui::Key::C)) {
            self.copy_to_clipboard();
        }

        // ── Top bar ───────────────────────────────────────────────────────────
        egui::TopBottomPanel::top("actions").show(ctx, |ui| {
            ui.add_space(6.0);
            ui.horizontal(|ui| {
                if ui.button("📋  Copy").clicked() {
                    self.copy_to_clipboard();
                }
                if ui.button("💾  Save").clicked() {
                    let path = self.config.output_path();
                    self.save_to_path(path);
                }
                ui.separator();
                ui.label("Save As:");
                ui.add(
                    egui::TextEdit::singleline(&mut self.save_as_path)
                        .desired_width(300.0)
                        .hint_text("/home/user/Pictures/shot.png"),
                );
                if ui.button("Save").clicked() {
                    let path = PathBuf::from(&self.save_as_path);
                    self.save_to_path(path);
                }
                ui.separator();
                let label = if self.settings_open { "▲ Effects" } else { "▼ Effects" };
                if ui.button(label).clicked() {
                    self.settings_open = !self.settings_open;
                }
                // Spinner while worker is active.
                if self.worker_running {
                    ui.spinner();
                }
                ui.separator();
                if ui.button("✖  Discard").clicked() {
                    self.action = Some(ReviewAction::Discarded);
                    ctx.send_viewport_cmd(egui::ViewportCommand::Close);
                }
            });
            ui.add_space(4.0);
        });

        // ── Effects panel ─────────────────────────────────────────────────────
        if self.settings_open {
            egui::TopBottomPanel::top("settings").show(ctx, |ui| {
                ui.add_space(6.0);
                ui.heading("Effects");
                ui.separator();

                let e = &mut self.config.effects;
                let mut changed = false;

                ui.horizontal(|ui| {
                    changed |= ui.checkbox(&mut e.rounded_corners, "Rounded corners").changed();
                    if e.rounded_corners {
                        ui.label("Radius:");
                        changed |= ui
                            .add(egui::Slider::new(&mut e.corner_radius, 1.0..=64.0).suffix(" px"))
                            .changed();
                    }
                });

                ui.horizontal(|ui| {
                    changed |= ui.checkbox(&mut e.drop_shadow, "Drop shadow").changed();
                    if e.drop_shadow {
                        ui.label("Blur:");
                        changed |= ui
                            .add(egui::Slider::new(&mut e.shadow_blur_radius, 0.0..=60.0).suffix(" px"))
                            .changed();
                        ui.label("X:");
                        changed |= ui
                            .add(egui::Slider::new(&mut e.shadow_offset_x, -40.0..=40.0).suffix(" px"))
                            .changed();
                        ui.label("Y:");
                        changed |= ui
                            .add(egui::Slider::new(&mut e.shadow_offset_y, -40.0..=40.0).suffix(" px"))
                            .changed();
                    }
                });

                if changed {
                    self.mark_dirty();
                    let _ = self.config.save();
                }
                ui.add_space(4.0);
            });
        }

        // ── Status bar ────────────────────────────────────────────────────────
        if let Some(msg) = self.status_message.clone() {
            egui::TopBottomPanel::bottom("status").show(ctx, |ui| {
                ui.add_space(4.0);
                ui.horizontal(|ui| {
                    ui.label(egui::RichText::new(&msg).color(Color32::LIGHT_GREEN));
                    if ui.small_button("✖").clicked() {
                        self.status_message = None;
                    }
                });
                ui.add_space(4.0);
            });
        }

        // ── Preview ───────────────────────────────────────────────────────────
        egui::CentralPanel::default().show(ctx, |ui| {
            ScrollArea::both().show(ui, |ui| {
                let tex_size = self.preview_texture.size_vec2();
                let available = ui.available_size();
                let scale = (available.x / tex_size.x)
                    .min(available.y / tex_size.y)
                    .min(1.0);
                let display_size = tex_size * scale;
                let img_rect = ui.allocate_space(display_size).1;

                draw_checkerboard(ui.painter(), img_rect);
                ui.painter().image(
                    self.preview_texture.id(),
                    img_rect,
                    egui::Rect::from_min_max(egui::Pos2::ZERO, egui::Pos2::new(1.0, 1.0)),
                    Color32::WHITE,
                );
                ui.painter().rect_stroke(
                    img_rect,
                    Rounding::ZERO,
                    Stroke::new(1.0, Color32::from_gray(80)),
                );
            });
        });

        // Close after save/copy — give one extra frame so the status message
        // is visible for a moment.
        if let Some(ReviewAction::Saved(_) | ReviewAction::Copied) = &self.action {
            ctx.send_viewport_cmd(egui::ViewportCommand::Close);
        }
    }
}

// ─── Helpers ─────────────────────────────────────────────────────────────────

fn upload_texture(ctx: &egui::Context, img: &RgbaImage) -> TextureHandle {
    let (w, h) = img.dimensions();
    let scaled;
    let src: &RgbaImage = if w > MAX_TEX || h > MAX_TEX {
        let s = (MAX_TEX as f32 / w as f32).min(MAX_TEX as f32 / h as f32);
        scaled = image::imageops::resize(
            img,
            (w as f32 * s) as u32,
            (h as f32 * s) as u32,
            image::imageops::FilterType::Triangle,
        );
        &scaled
    } else {
        img
    };
    let (uw, uh) = src.dimensions();
    let ci = ColorImage::from_rgba_unmultiplied([uw as usize, uh as usize], src.as_raw());
    ctx.load_texture("preview", ci, TextureOptions::LINEAR)
}

fn draw_checkerboard(painter: &egui::Painter, rect: egui::Rect) {
    let tile = 8.0_f32;
    let c0 = Color32::from_gray(200);
    let c1 = Color32::from_gray(160);
    let cols = (rect.width() / tile).ceil() as u32;
    let rows = (rect.height() / tile).ceil() as u32;
    for row in 0..rows {
        for col in 0..cols {
            let color = if (row + col) % 2 == 0 { c0 } else { c1 };
            let min = rect.min + Vec2::new(col as f32 * tile, row as f32 * tile);
            let max = (min + Vec2::splat(tile)).min(rect.max);
            painter.rect_filled(egui::Rect::from_min_max(min, max), Rounding::ZERO, color);
        }
    }
}