use std::{fmt::Display, sync::Arc};

use egui::{
    Align, CentralPanel, Color32, ComboBox, Context, Image, ScrollArea, Slider, TextEdit,
    TextureOptions, Ui, Vec2, ViewportBuilder, ViewportId,
};
use egui_extras::{Column, Size, StripBuilder, TableBuilder};
use serde::{Deserialize, Serialize};

use crate::{
    emulator::SimId,
    memory::{MemoryMonitor, MemoryView},
    vram::{VramImage, VramImageLoader, VramResource as _, VramTextureLoader},
    window::{utils::UiExt as _, AppWindow},
};

use super::utils::{self, CharacterGrid};

#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Serialize, Deserialize)]
pub enum VramPalette {
    Generic,
    Bg0,
    Bg1,
    Bg2,
    Bg3,
    Obj0,
    Obj1,
    Obj2,
    Obj3,
}

impl VramPalette {
    pub const fn values() -> [VramPalette; 9] {
        [
            Self::Generic,
            Self::Bg0,
            Self::Bg1,
            Self::Bg2,
            Self::Bg3,
            Self::Obj0,
            Self::Obj1,
            Self::Obj2,
            Self::Obj3,
        ]
    }

    pub const fn offset(self) -> Option<usize> {
        match self {
            Self::Generic => None,
            Self::Bg0 => Some(0),
            Self::Bg1 => Some(2),
            Self::Bg2 => Some(4),
            Self::Bg3 => Some(6),
            Self::Obj0 => Some(8),
            Self::Obj1 => Some(10),
            Self::Obj2 => Some(12),
            Self::Obj3 => Some(14),
        }
    }
}

impl Display for VramPalette {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Self::Generic => f.write_str("Generic"),
            Self::Bg0 => f.write_str("BG 0"),
            Self::Bg1 => f.write_str("BG 1"),
            Self::Bg2 => f.write_str("BG 2"),
            Self::Bg3 => f.write_str("BG 3"),
            Self::Obj0 => f.write_str("OBJ 0"),
            Self::Obj1 => f.write_str("OBJ 1"),
            Self::Obj2 => f.write_str("OBJ 2"),
            Self::Obj3 => f.write_str("OBJ 3"),
        }
    }
}

pub struct CharacterDataWindow {
    sim_id: SimId,
    loader: Arc<VramTextureLoader<CharDataLoader>>,
    brightness: MemoryView,
    palettes: MemoryView,
    palette: VramPalette,
    index: usize,
    index_str: String,
    scale: f32,
    show_grid: bool,
}

impl CharacterDataWindow {
    pub fn new(sim_id: SimId, memory: &mut MemoryMonitor) -> Self {
        Self {
            sim_id,
            loader: Arc::new(VramTextureLoader::new(CharDataLoader::new(sim_id, memory))),
            brightness: memory.view(sim_id, 0x0005f824, 8),
            palettes: memory.view(sim_id, 0x0005f860, 16),
            palette: VramPalette::Generic,
            index: 0,
            index_str: "0".into(),
            scale: 4.0,
            show_grid: true,
        }
    }

    fn show_form(&mut self, ui: &mut Ui) {
        let row_height = ui.spacing().interact_size.y;
        ui.vertical(|ui| {
            TableBuilder::new(ui)
                .column(Column::auto())
                .column(Column::remainder())
                .body(|mut body| {
                    body.row(row_height, |mut row| {
                        row.col(|ui| {
                            ui.label("Index");
                        });
                        row.col(|ui| {
                            ui.number_picker(&mut self.index_str, &mut self.index, 0..2048);
                        });
                    });
                    body.row(row_height, |mut row| {
                        row.col(|ui| {
                            ui.label("Address");
                        });
                        row.col(|ui| {
                            let address = match self.index {
                                0x000..0x200 => 0x00060000 + self.index * 16,
                                0x200..0x400 => 0x000e0000 + (self.index - 0x200) * 16,
                                0x400..0x600 => 0x00160000 + (self.index - 0x400) * 16,
                                0x600..0x800 => 0x001e0000 + (self.index - 0x600) * 16,
                                _ => unreachable!("can't happen"),
                            };
                            let mut address_str = format!("{address:08x}");
                            ui.add_enabled(
                                false,
                                TextEdit::singleline(&mut address_str).horizontal_align(Align::Max),
                            );
                        });
                    });
                    body.row(row_height, |mut row| {
                        row.col(|ui| {
                            ui.label("Mirror");
                        });
                        row.col(|ui| {
                            let mirror = 0x00078000 + (self.index * 16);
                            let mut mirror_str = format!("{mirror:08x}");
                            ui.add_enabled(
                                false,
                                TextEdit::singleline(&mut mirror_str).horizontal_align(Align::Max),
                            );
                        });
                    });
                });
            let resource = CharDataResource::Character {
                palette: self.palette,
                index: self.index,
            };
            let image = Image::new(resource.to_uri())
                .maintain_aspect_ratio(true)
                .tint(Color32::RED)
                .texture_options(TextureOptions::NEAREST);
            ui.add(image);
            ui.section("Colors", |ui| {
                ui.horizontal(|ui| {
                    ui.label("Palette");
                    ComboBox::from_id_salt("palette")
                        .selected_text(self.palette.to_string())
                        .width(ui.available_width())
                        .show_ui(ui, |ui| {
                            for palette in VramPalette::values() {
                                ui.selectable_value(
                                    &mut self.palette,
                                    palette,
                                    palette.to_string(),
                                );
                            }
                        });
                });
                TableBuilder::new(ui)
                    .columns(Column::remainder(), 4)
                    .body(|mut body| {
                        let palette = self.load_palette_colors();
                        body.row(30.0, |mut row| {
                            for color in palette {
                                row.col(|ui| {
                                    let rect = ui.available_rect_before_wrap();
                                    let scale = rect.height() / rect.width();
                                    let rect = rect.scale_from_center2(Vec2::new(scale, 1.0));
                                    ui.painter().rect_filled(
                                        rect,
                                        0.0,
                                        Color32::RED * Color32::from_gray(color),
                                    );
                                });
                            }
                        });
                    });
            });
            ui.section("Display", |ui| {
                ui.horizontal(|ui| {
                    ui.label("Scale");
                    ui.spacing_mut().slider_width = ui.available_width();
                    let slider = Slider::new(&mut self.scale, 1.0..=10.0)
                        .step_by(1.0)
                        .show_value(false);
                    ui.add(slider);
                });
                ui.checkbox(&mut self.show_grid, "Show grid");
            });
        });
    }

    fn load_palette_colors(&self) -> [u8; 4] {
        let Some(offset) = self.palette.offset() else {
            return utils::GENERIC_PALETTE;
        };
        let palette = self.palettes.borrow().read(offset);
        let brightnesses = self.brightness.borrow();
        let brts = brightnesses.range(0, 8);
        utils::parse_palette(palette, brts)
    }

    fn show_chardata(&mut self, ui: &mut Ui) {
        let resource = CharDataResource::CharacterData {
            palette: self.palette,
        };
        let grid = CharacterGrid::new(resource.to_uri())
            .with_scale(self.scale)
            .with_grid(self.show_grid)
            .with_selected(self.index);
        if let Some(selected) = grid.show(ui) {
            self.index = selected;
            self.index_str = selected.to_string();
        }
    }
}

impl AppWindow for CharacterDataWindow {
    fn viewport_id(&self) -> ViewportId {
        ViewportId::from_hash_of(format!("chardata-{}", self.sim_id))
    }

    fn sim_id(&self) -> SimId {
        self.sim_id
    }

    fn initial_viewport(&self) -> ViewportBuilder {
        ViewportBuilder::default()
            .with_title(format!("Character Data ({})", self.sim_id))
            .with_inner_size((640.0, 480.0))
    }

    fn on_init(&mut self, ctx: &Context, _render_state: &egui_wgpu::RenderState) {
        ctx.add_texture_loader(self.loader.clone());
    }

    fn show(&mut self, ctx: &Context) {
        self.loader.begin_pass();
        CentralPanel::default().show(ctx, |ui| {
            ui.horizontal_top(|ui| {
                StripBuilder::new(ui)
                    .size(Size::relative(0.3))
                    .size(Size::remainder())
                    .horizontal(|mut strip| {
                        strip.cell(|ui| {
                            ScrollArea::vertical().show(ui, |ui| self.show_form(ui));
                        });
                        strip.cell(|ui| {
                            ScrollArea::both().show(ui, |ui| self.show_chardata(ui));
                        });
                    });
            });
        });
    }
}

#[derive(Serialize, Deserialize, Clone, PartialEq, Eq, Hash)]
enum CharDataResource {
    Character { palette: VramPalette, index: usize },
    CharacterData { palette: VramPalette },
}

struct CharDataLoader {
    chardata: MemoryView,
    brightness: MemoryView,
    palettes: MemoryView,
}

impl CharDataLoader {
    pub fn new(sim_id: SimId, memory: &mut MemoryMonitor) -> Self {
        Self {
            chardata: memory.view(sim_id, 0x00078000, 0x8000),
            brightness: memory.view(sim_id, 0x0005f824, 8),
            palettes: memory.view(sim_id, 0x0005f860, 16),
        }
    }

    fn update_character(&self, image: &mut VramImage, palette: VramPalette, index: usize) {
        if index >= 2048 {
            return;
        }
        let palette = self.load_palette(palette);
        let chardata = self.chardata.borrow();
        let character = chardata.range::<u16>(index * 8, 8);
        for (row, pixels) in character.iter().enumerate() {
            for col in 0..8 {
                let char = (pixels >> (col * 2)) & 0x03;
                image.write((col, row), palette[char as usize]);
            }
        }
    }

    fn update_character_data(&self, image: &mut VramImage, palette: VramPalette) {
        let palette = self.load_palette(palette);
        let chardata = self.chardata.borrow();
        for (row, pixels) in chardata.range::<u16>(0, 8 * 2048).iter().enumerate() {
            let char_index = row / 8;
            let row_index = row % 8;
            let x = (char_index % 16) * 8;
            let y = (char_index / 16) * 8 + row_index;
            for col in 0..8 {
                let char = (pixels >> (col * 2)) & 0x03;
                image.write((x + col, y), palette[char as usize]);
            }
        }
    }

    fn load_palette(&self, palette: VramPalette) -> [u8; 4] {
        let Some(offset) = palette.offset() else {
            return utils::GENERIC_PALETTE;
        };
        let palette = self.palettes.borrow().read(offset);
        let brightnesses = self.brightness.borrow();
        let brts = brightnesses.range(0, 8);
        utils::parse_palette(palette, brts)
    }
}

impl VramImageLoader for CharDataLoader {
    type Resource = CharDataResource;

    fn id(&self) -> &str {
        concat!(module_path!(), "::CharDataLoader")
    }

    fn add(&self, resource: &Self::Resource) -> Option<VramImage> {
        match resource {
            CharDataResource::Character { palette, index } => {
                let mut image = VramImage::new(8, 8);
                self.update_character(&mut image, *palette, *index);
                Some(image)
            }
            CharDataResource::CharacterData { palette } => {
                let mut image = VramImage::new(8 * 16, 8 * 128);
                self.update_character_data(&mut image, *palette);
                Some(image)
            }
        }
    }

    fn update<'a>(
        &'a self,
        resources: impl Iterator<Item = (&'a Self::Resource, &'a mut VramImage)>,
    ) {
        for (resource, image) in resources {
            match resource {
                CharDataResource::Character { palette, index } => {
                    self.update_character(image, *palette, *index)
                }
                CharDataResource::CharacterData { palette } => {
                    self.update_character_data(image, *palette)
                }
            }
        }
    }
}