use super::api::{Api, ApiError, Skill, Specialization, Trait};
use super::bt::{BuildTemplate, TraitChoice, Traitline};
use image::{
    imageops, imageops::FilterType::CatmullRom, DynamicImage, GenericImage, GenericImageView,
    ImageBuffer, Pixel, Primitive, Rgba, RgbaImage,
};
use imageproc::{drawing, rect::Rect};
use num_traits::{Num, NumCast};
use rusttype::{Font, Scale};
use serde::{Deserialize, Serialize};
use thiserror::Error;

#[derive(Error, Debug)]
pub enum RenderError {
    #[error("Error accessing the API")]
    ApiError(#[from] ApiError),
    #[error("Image processing error")]
    ImageError(#[from] image::ImageError),
    #[error("The build template contains nothing worth rendering")]
    EmptyBuild,
}

#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, Serialize, Deserialize)]
pub enum Alignment {
    Left,
    Center,
    Right,
}

#[derive(Debug, Clone)]
pub struct RenderOptions {
    pub skill_size: u32,
    pub traitline_height: u32,
    pub traitline_width: u32,
    pub traitline_brightness: i32,
    pub traitline_use_gradient: bool,
    pub traitline_gradient_size: u32,
    pub traitline_x_offset: u32,
    pub trait_size: u32,
    pub line_color: Rgba<u8>,
    pub line_height: u32,
    pub font: Font<'static>,
    pub text_color: Rgba<u8>,
    pub text_size: u32,
    pub background_color: Rgba<u8>,
    pub render_specialization_names: bool,
    pub skill_offset: u32,
    pub skill_alignment: Alignment,
    pub specialization_name_alignment: Alignment,
}

impl Default for RenderOptions {
    fn default() -> Self {
        RenderOptions {
            skill_size: 100,
            traitline_height: 137,
            traitline_width: 647,
            traitline_brightness: 100,
            traitline_use_gradient: true,
            traitline_gradient_size: 50,
            traitline_x_offset: 200,
            trait_size: 30,
            line_color: Rgba([0, 0, 0, 255]),
            line_height: 4,
            font: Font::try_from_bytes(include_bytes!("LiberationMono.ttf"))
                .expect("Invalid font data for default font"),
            text_color: Rgba([0, 0, 0, 255]),
            text_size: 20,
            background_color: Rgba([0, 0, 0, 0]),
            render_specialization_names: true,
            skill_offset: 30,
            skill_alignment: Alignment::Center,
            specialization_name_alignment: Alignment::Left,
        }
    }
}

// These values were determined from the thief specialization background images, as those do not
// have anything fancy going on and are instead transparent. Therefore, we can use them as a
// "reference" for the intended specialization crop size.
//
// Note: Increasing those values will mean that thief build templates will end up with more
// transparency than intended.
const BG_CROP_HEIGHT: u32 = 136;
const BG_CROP_WIDTH: u32 = 647;

const TRAITS_PER_TIER: u32 = 3;
const TIER_COUNT: u32 = 3;
const TOTAL_COLUMN_COUNT: u32 = 2 * TIER_COUNT;
const MINOR_LINE_SPLIT: u32 = 4;
const MIDDLE_COL: u32 = 1;

fn half<T: Num>(input: T) -> T {
    let two = T::one() + T::one();
    input / two
}

pub struct Renderer<'r> {
    api: &'r mut Api,
    options: RenderOptions,
    minor_mask: DynamicImage,
    major_mask: DynamicImage,
    grid: Grid,
}

impl<'r> Renderer<'r> {
    /// Create a new renderer using the given API.
    pub fn new(api: &mut Api, options: RenderOptions) -> Renderer<'_> {
        let minor_mask = image::load_from_memory(include_bytes!("minor_trait_mask.png"))
            .expect("Minor mask image could not be loaded")
            .resize(options.trait_size, options.trait_size, CatmullRom);
        let major_mask = image::load_from_memory(include_bytes!("major_trait_mask.png"))
            .expect("Major mask image could not be loaded")
            .resize(options.trait_size, options.trait_size, CatmullRom);
        let grid = Grid {
            x_offset: options.traitline_x_offset,
            width: options.traitline_width - options.traitline_x_offset,
            height: options.traitline_height,
            rows: TRAITS_PER_TIER,
            cols: TOTAL_COLUMN_COUNT,
        };
        Renderer {
            api,
            options,
            minor_mask,
            major_mask,
            grid,
        }
    }

    pub fn render_skills(&mut self, skills: &[Option<Skill>]) -> Result<RgbaImage, RenderError> {
        let mut buffer = ImageBuffer::from_pixel(
            skills.len() as u32 * self.options.skill_size,
            self.options.skill_size,
            self.options.background_color,
        );
        for (i, skill) in skills.iter().enumerate() {
            if let Some(skill) = skill {
                let img = self.api.get_image(&skill.icon)?.resize(
                    self.options.skill_size,
                    self.options.skill_size,
                    CatmullRom,
                );
                buffer.copy_from(&img, i as u32 * self.options.skill_size, 0)?;
            }
        }
        Ok(buffer)
    }

    fn render_minor_trait(
        &mut self,
        buffer: &mut RgbaImage,
        minor: &Trait,
    ) -> Result<(), RenderError> {
        let trait_size = self.options.trait_size;
        let minor_img = self
            .api
            .get_image(&minor.icon)?
            .resize(trait_size, trait_size, CatmullRom);
        let minor_img = with_mask(&minor_img, &self.minor_mask);
        // Minor traits are always in the middle row, which should be 1.
        // We also need to skip the major columns, therefore we need to multiply the column number
        // by two.
        let (x, y) = self.grid.pos(MIDDLE_COL, 2 * (minor.tier - 1));
        imageops::overlay(
            buffer,
            &minor_img,
            (x - half(trait_size)).into(),
            (y - half(trait_size)).into(),
        );
        Ok(())
    }

    fn render_major_trait(
        &mut self,
        buffer: &mut RgbaImage,
        major: &Trait,
        vertical_pos: u8,
        chosen: bool,
    ) -> Result<(), RenderError> {
        let trait_size = self.options.trait_size;
        let major_img = self
            .api
            .get_image(&major.icon)?
            .resize(trait_size, trait_size, CatmullRom);
        let major_img = if !chosen {
            with_mask(&major_img.grayscale(), &major_img)
        } else {
            major_img.to_rgba8()
        };
        let major_img = with_mask(&major_img, &self.major_mask);
        let (x, y) = self.grid.pos(vertical_pos as u32, 2 * (major.tier - 1) + 1);
        imageops::overlay(
            buffer,
            &major_img,
            (x - half(trait_size)).into(),
            (y - half(trait_size)).into(),
        );
        Ok(())
    }

    fn render_line(
        &mut self,
        buffer: &mut RgbaImage,
        tier: u8,
        choice: TraitChoice,
    ) -> Result<(), RenderError> {
        if choice == TraitChoice::None {
            return Ok(());
        }

        let trait_size = self.options.trait_size;
        let (start_x, start_y) = self.grid.pos(MIDDLE_COL, 2 * tier as u32);
        let start_x = start_x + half(trait_size);
        let start_y = start_y - half(trait_size) + trait_size / MINOR_LINE_SPLIT * (choice as u32);

        let (end_x, end_y) = self.grid.pos(choice as u32 - 1, 2 * tier as u32 + 1);
        let end_x = end_x - half(trait_size);

        draw_thick_line(
            buffer,
            (start_x, start_y),
            (end_x, end_y),
            self.options.line_height,
            self.options.line_color,
        );
        if tier as u32 == TIER_COUNT - 1 {
            return Ok(());
        }

        draw_thick_line(
            buffer,
            (end_x + trait_size, end_y),
            (end_x + self.grid.x_slice(), start_y),
            self.options.line_height,
            self.options.line_color,
        );

        Ok(())
    }

    pub fn render_traitline(&mut self, traitline: &Traitline) -> Result<RgbaImage, RenderError> {
        let (spec, choices) = traitline;
        let mut background = self.api.get_image(&spec.background)?;
        let mut buffer = background
            .crop(
                0,
                background.height() - BG_CROP_HEIGHT,
                BG_CROP_WIDTH,
                BG_CROP_HEIGHT,
            )
            .resize(
                self.options.traitline_width,
                self.options.traitline_height,
                imageops::FilterType::CatmullRom,
            )
            .to_rgba8();

        if self.options.traitline_use_gradient {
            buffer = brighten_gradient(
                &buffer,
                self.options.traitline_x_offset - self.options.traitline_gradient_size,
                self.options.traitline_x_offset,
                self.options.traitline_brightness,
            );
        } else {
            buffer = imageops::colorops::brighten(&buffer, self.options.traitline_brightness);
        }

        let minor_traits = self.api.get_traits(&spec.minor_traits)?;
        for minor in &minor_traits {
            self.render_minor_trait(&mut buffer, minor)?;
        }

        let major_traits = self.api.get_traits(&spec.major_traits)?;
        for (i, major) in major_traits.iter().enumerate() {
            let choice = choices[major.tier as usize - 1];
            let vert_pos = (i as u32 % TRAITS_PER_TIER) as u8;
            let chosen = choice as u8 == vert_pos + 1;
            self.render_major_trait(&mut buffer, major, vert_pos, chosen)?;
        }

        for (tier, choice) in choices.iter().enumerate() {
            self.render_line(&mut buffer, tier as u8, *choice)?;
        }
        Ok(buffer)
    }

    pub fn render_specialization_name(
        &mut self,
        specialization: &Specialization,
    ) -> Result<RgbaImage, RenderError> {
        let text = &specialization.name;
        let scale = Scale {
            x: self.options.text_size as f32,
            y: self.options.text_size as f32,
        };
        let width = text_width(text, &self.options.font, scale);
        let mut buffer =
            ImageBuffer::from_pixel(width, self.options.text_size, self.options.background_color);
        drawing::draw_text_mut(
            &mut buffer,
            self.options.text_color,
            0,
            0,
            scale,
            &self.options.font,
            text,
        );
        Ok(buffer)
    }

    pub fn render_buildtemplate(
        &mut self,
        build: &BuildTemplate,
    ) -> Result<RgbaImage, RenderError> {
        let images = self.construct_parts(build)?;
        if images.is_empty() {
            return Err(RenderError::EmptyBuild);
        }
        self.merge_parts(&images)
    }

    fn construct_parts(
        &mut self,
        build: &BuildTemplate,
    ) -> Result<Vec<(Alignment, RgbaImage)>, RenderError> {
        let mut images: Vec<(Alignment, RgbaImage)> = Vec::new();

        for traitline in build.traitlines().iter().filter(|x| x.is_some()) {
            let traitline = traitline.as_ref().unwrap();
            if self.options.render_specialization_names {
                let header = self.render_specialization_name(&traitline.0)?;
                images.push((self.options.specialization_name_alignment, header));
            }
            let inner = self.render_traitline(traitline)?;
            images.push((Alignment::Left, inner));
        }

        let needs_space = build.skill_count() > 0 && build.traitline_count() > 0;
        if needs_space {
            let separator = ImageBuffer::from_pixel(
                self.options.traitline_width,
                self.options.skill_offset,
                self.options.background_color,
            );
            images.push((Alignment::Left, separator));
        }

        if build.skill_count() > 0 {
            let skills = self.render_skills(build.skills())?;
            images.push((self.options.skill_alignment, skills));
        }

        Ok(images)
    }

    fn merge_parts(&mut self, images: &[(Alignment, RgbaImage)]) -> Result<RgbaImage, RenderError> {
        let width = images.iter().map(snd).map(RgbaImage::width).max().unwrap();
        let height = images.iter().map(snd).map(RgbaImage::height).sum();
        let mut buffer = ImageBuffer::from_pixel(width, height, self.options.background_color);
        let mut pos_y = 0;

        for (alignment, image) in images {
            let pos_x = match alignment {
                Alignment::Left => 0,
                Alignment::Center => half(width - image.width()),
                Alignment::Right => width - image.width(),
            };
            buffer.copy_from(image, pos_x, pos_y)?;
            pos_y += image.height();
        }

        Ok(buffer)
    }
}

fn snd<A, B>(input: &(A, B)) -> &B {
    &input.1
}

fn with_mask<I, J>(input: &I, mask: &J) -> RgbaImage
where
    I: GenericImage<Pixel = Rgba<u8>>,
    J: GenericImage<Pixel = Rgba<u8>>,
{
    imageproc::map::map_pixels(input, |x, y, p| {
        let alpha = mask.get_pixel(x, y)[3];
        Rgba([p[0], p[1], p[2], alpha])
    })
}

fn clamp<T: PartialOrd>(value: T, lower: T, upper: T) -> T {
    if value < lower {
        lower
    } else if value > upper {
        upper
    } else {
        value
    }
}

fn brighten_gradient<I, P, S>(
    image: &I,
    start_x: u32,
    end_x: u32,
    value: i32,
) -> ImageBuffer<P, Vec<S>>
where
    I: GenericImageView<Pixel = P>,
    P: Pixel<Subpixel = S> + 'static,
    S: Primitive + 'static,
{
    let (width, height) = image.dimensions();
    let mut out = ImageBuffer::new(width, height);

    let max = S::max_value();
    let max: i32 = NumCast::from(max).unwrap();

    for y in 0..height {
        for x in 0..width {
            let e = image.get_pixel(x, y).map_with_alpha(
                |b| {
                    let interpol_value = if x < start_x {
                        0
                    } else if x > end_x {
                        value
                    } else {
                        let frac = (x - start_x) as f32 / (end_x - start_x) as f32;
                        (frac * value as f32).round() as i32
                    };
                    let c: i32 = NumCast::from(b).unwrap();
                    let d = clamp(c + interpol_value, 0, max);

                    NumCast::from(d).unwrap()
                },
                |alpha| alpha,
            );

            out.put_pixel(x, y, e);
        }
    }

    out
}

fn draw_thick_line<I>(
    image: &mut I,
    start: (u32, u32),
    end: (u32, u32),
    thickness: u32,
    color: I::Pixel,
) where
    I: GenericImage<Pixel = Rgba<u8>>,
{
    let delta_x = end.0 as i32 - start.0 as i32;
    let delta_y = end.1 as i32 - start.1 as i32;
    let line_length = ((delta_x * delta_x + delta_y * delta_y) as f32)
        .sqrt()
        .round() as u32;

    let mut line_buffer: RgbaImage = ImageBuffer::new(line_length, line_length);
    let halfway = half(line_length - thickness);

    let rect = Rect::at(0, halfway as i32).of_size(line_length, thickness);
    drawing::draw_filled_rect_mut(&mut line_buffer, rect, color);

    line_buffer = imageproc::geometric_transformations::rotate_about_center(
        &line_buffer,
        (delta_y as f32 / delta_x as f32).atan(),
        imageproc::geometric_transformations::Interpolation::Bicubic,
        Rgba([0, 0, 0, 0]),
    );

    let half_x = (start.0 as i32 + half(delta_x)) as u32;
    let half_y = (start.1 as i32 + half(delta_y)) as u32;

    imageops::overlay(
        image,
        &line_buffer,
        (half_x - half(line_length)).into(),
        (half_y - half(line_length)).into(),
    );
}

fn text_width(text: &str, font: &Font, scale: Scale) -> u32 {
    font.glyphs_for(text.chars())
        .map(|glyph| glyph.scaled(scale).h_metrics().advance_width)
        .sum::<f32>() as u32
}

/// A helper structure representing a grid of squares.
///
/// This can be used to calculate the centers of the traits that should be placed on the
/// traitlines.
struct Grid {
    x_offset: u32,
    width: u32,
    height: u32,
    rows: u32,
    cols: u32,
}

impl Grid {
    /// Return the coordinates of the center of the given square.
    #[inline(always)]
    fn pos(&self, row: u32, col: u32) -> (u32, u32) {
        assert!(
            row < self.rows,
            "row {} is outside the bounds ({})",
            row,
            self.rows
        );
        assert!(
            col < self.cols,
            "col {} is outside the bounds ({})",
            col,
            self.cols
        );

        let x_slice = self.x_slice();
        let y_slice = self.y_slice();

        let x_pos = x_slice * col + self.x_offset + half(x_slice);
        let y_pos = y_slice * row + half(y_slice);
        (x_pos, y_pos)
    }

    /// Returns the width of a x slice.
    #[inline(always)]
    fn x_slice(&self) -> u32 {
        self.width / self.cols
    }

    /// Returns the height of an y slice.
    #[inline(always)]
    fn y_slice(&self) -> u32 {
        self.height / self.rows
    }
}