use skia_safe::{self as skia, Paint, RRect};

use super::{filters, RenderState, SurfaceId};
use crate::error::Result;
use crate::get_resources;
use crate::render::get_source_rect;
use crate::shapes::{merge_fills, Fill, Frame, ImageFill, Rect, Shape, Type};

// Set the clipping area to the shape outline within the container bounds
fn clip_to_shape(
    canvas: &skia::Canvas,
    shape: &Shape,
    container: &crate::math::Rect,
    antialias: bool,
) {
    match &shape.shape_type {
        Type::Rect(Rect {
            corners: Some(corners),
        })
        | Type::Frame(Frame {
            corners: Some(corners),
            ..
        }) => {
            let rrect: RRect = RRect::new_rect_radii(container, corners);
            canvas.clip_rrect(rrect, skia::ClipOp::Intersect, antialias);
        }
        Type::Rect(_) | Type::Frame(_) => {
            canvas.clip_rect(container, skia::ClipOp::Intersect, antialias);
        }
        Type::Circle => {
            let oval_path = {
                let mut pb = skia::PathBuilder::new();
                pb.add_oval(container, None, None);
                pb.detach()
            };
            canvas.clip_path(&oval_path, skia::ClipOp::Intersect, antialias);
        }
        shape_type @ (Type::Path(_) | Type::Bool(_)) => {
            if let Some(path) = shape_type.path() {
                if let Some(path_transform) = shape.to_path_transform() {
                    canvas.clip_path(
                        &path
                            .to_skia_path(shape.svg_attrs.as_ref())
                            .make_transform(&path_transform),
                        skia::ClipOp::Intersect,
                        antialias,
                    );
                }
            }
        }
        Type::SVGRaw(_) => {
            canvas.clip_rect(container, skia::ClipOp::Intersect, antialias);
        }
        Type::Group(_) => unreachable!("A group should not have fills"),
        Type::Text(_) => unimplemented!("TODO"),
    }
}

fn draw_image_fill(
    render_state: &mut RenderState,
    shape: &Shape,
    image_fill: &ImageFill,
    paint: &Paint,
    antialias: bool,
    surface_id: SurfaceId,
) {
    if draw_svg_image_fill(
        render_state,
        shape,
        image_fill,
        paint,
        antialias,
        surface_id,
    ) {
        return;
    }

    let Some(image) = get_resources().images.get(&image_fill.id()) else {
        return;
    };

    let size = image.dimensions();
    let canvas = render_state.surfaces.canvas_and_mark_dirty(surface_id);
    let container = &shape.selrect;

    let src_rect = get_source_rect(size, container, image_fill);
    let dest_rect = container;

    let mut image_paint = skia::Paint::default();
    image_paint.set_anti_alias(antialias);
    if let Some(filter) = shape.image_filter(1.) {
        image_paint.set_image_filter(filter.clone());
    }

    let layer_rec = skia::canvas::SaveLayerRec::default().paint(&image_paint);
    // Save the current canvas state
    canvas.save_layer(&layer_rec);

    clip_to_shape(canvas, shape, container, antialias);

    // Draw the image with the calculated destination rectangle
    canvas.draw_image_rect_with_sampling_options(
        image,
        Some((&src_rect, skia::canvas::SrcRectConstraint::Strict)),
        dest_rect,
        get_resources().sampling_options,
        paint,
    );

    // Restore the canvas to remove the clipping
    canvas.restore();
}

// Draws an SVG image fill from its parsed DOM. The canvas transform carries
// the current zoom, so the SVG rasterizes at display resolution instead of
// being stretched from a fixed-size texture. Returns false when the stored
// image is not an SVG.
fn draw_svg_image_fill(
    render_state: &mut RenderState,
    shape: &Shape,
    image_fill: &ImageFill,
    paint: &Paint,
    antialias: bool,
    surface_id: SurfaceId,
) -> bool {
    let Some((dom, size)) = get_resources().images.get_svg(&image_fill.id()) else {
        return false;
    };

    let canvas = render_state.surfaces.canvas_and_mark_dirty(surface_id);
    let container = &shape.selrect;
    let size = skia::ISize::new(size.width as i32, size.height as i32);
    let src_rect = get_source_rect(size, container, image_fill);
    if src_rect.width() <= 0.0 || src_rect.height() <= 0.0 {
        return true;
    }

    let mut image_paint = skia::Paint::default();
    image_paint.set_anti_alias(antialias);
    if let Some(filter) = shape.image_filter(1.) {
        image_paint.set_image_filter(filter.clone());
    }

    let layer_rec = skia::canvas::SaveLayerRec::default().paint(&image_paint);
    canvas.save_layer(&layer_rec);

    clip_to_shape(canvas, shape, container, antialias);

    // Apply the fill paint (opacity/blend) to the whole SVG as one layer.
    let fill_layer = skia::canvas::SaveLayerRec::default().paint(paint);
    canvas.save_layer(&fill_layer);

    // Map the cropped source rect onto the container: cover semantics when
    // keep-aspect-ratio is set, stretch otherwise (same math as the raster
    // path, expressed as a canvas transform).
    let scale_x = container.width() / src_rect.width();
    let scale_y = container.height() / src_rect.height();
    canvas.translate((
        container.left - src_rect.left * scale_x,
        container.top - src_rect.top * scale_y,
    ));
    canvas.scale((scale_x, scale_y));
    dom.render(canvas);

    canvas.restore();
    canvas.restore();

    true
}

/**
 * This SHOULD be the only public function in this module.
 */
pub fn render(
    render_state: &mut RenderState,
    shape: &Shape,
    fills: &[Fill],
    antialias: bool,
    surface_id: SurfaceId,
    outset: Option<f32>,
) -> Result<()> {
    if fills.is_empty() {
        return Ok(());
    }

    let scale = render_state.get_scale().max(1e-6);
    let inset = if shape.has_inner_stroke() {
        Some(1.0 / scale)
    } else {
        None
    };

    // Image fills use draw_image_fill which needs render_state for GPU images
    // and sampling options that get_fill_shader (used by merge_fills) lacks.
    let has_image_fills = fills.iter().any(|f| matches!(f, Fill::Image(_)));
    if has_image_fills {
        for fill in fills.iter().rev() {
            render_single_fill(
                render_state,
                shape,
                fill,
                antialias,
                surface_id,
                outset,
                inset,
            )?;
        }
        return Ok(());
    }

    let mut paint = merge_fills(fills, shape.selrect);
    paint.set_anti_alias(antialias);

    if let Some(image_filter) = shape.image_filter(1.) {
        let bounds = image_filter.compute_fast_bounds(shape.selrect);
        if filters::render_with_filter_surface(
            render_state,
            bounds,
            surface_id,
            |state, temp_surface| {
                let mut filtered_paint = paint.clone();
                filtered_paint.set_image_filter(image_filter.clone());
                draw_fill_to_surface(state, shape, temp_surface, &filtered_paint, outset, inset);
                Ok(())
            },
        )? {
            return Ok(());
        } else {
            paint.set_image_filter(image_filter);
        }
    }

    draw_fill_to_surface(render_state, shape, surface_id, &paint, outset, inset);
    Ok(())
}

/// Draws a single paint (with a merged shader) to the appropriate surface
/// based on the shape type.
/// When `inset` is Some(eps), the fill is inset by eps (e.g. to avoid seam with inner strokes).
fn draw_fill_to_surface(
    render_state: &mut RenderState,
    shape: &Shape,
    surface_id: SurfaceId,
    paint: &Paint,
    outset: Option<f32>,
    inset: Option<f32>,
) {
    match &shape.shape_type {
        Type::Rect(_) | Type::Frame(_) => {
            render_state
                .surfaces
                .draw_rect_to(surface_id, shape, paint, outset, inset);
        }
        Type::Circle => {
            render_state
                .surfaces
                .draw_circle_to(surface_id, shape, paint, outset, inset);
        }
        Type::Path(_) | Type::Bool(_) => {
            render_state
                .surfaces
                .draw_path_to(surface_id, shape, paint, outset, inset);
        }
        Type::Group(_) => {}
        _ => unreachable!("This shape should not have fills"),
    }
}

fn render_single_fill(
    render_state: &mut RenderState,
    shape: &Shape,
    fill: &Fill,
    antialias: bool,
    surface_id: SurfaceId,
    outset: Option<f32>,
    inset: Option<f32>,
) -> Result<()> {
    let mut paint = fill.to_paint(&shape.selrect, antialias);
    if let Some(image_filter) = shape.image_filter(1.) {
        let bounds = image_filter.compute_fast_bounds(shape.selrect);
        if filters::render_with_filter_surface(
            render_state,
            bounds,
            surface_id,
            |state, temp_surface| {
                let mut filtered_paint = paint.clone();
                filtered_paint.set_image_filter(image_filter.clone());
                draw_single_fill_to_surface(
                    state,
                    shape,
                    fill,
                    antialias,
                    temp_surface,
                    &filtered_paint,
                    outset,
                    inset,
                );
                Ok(())
            },
        )? {
            return Ok(());
        } else {
            paint.set_image_filter(image_filter);
        }
    }

    draw_single_fill_to_surface(
        render_state,
        shape,
        fill,
        antialias,
        surface_id,
        &paint,
        outset,
        inset,
    );
    Ok(())
}

#[allow(clippy::too_many_arguments)]
fn draw_single_fill_to_surface(
    render_state: &mut RenderState,
    shape: &Shape,
    fill: &Fill,
    antialias: bool,
    surface_id: SurfaceId,
    paint: &Paint,
    outset: Option<f32>,
    inset: Option<f32>,
) {
    match (fill, &shape.shape_type) {
        (Fill::Image(image_fill), _) => {
            draw_image_fill(
                render_state,
                shape,
                image_fill,
                paint,
                antialias,
                surface_id,
            );
        }
        (_, Type::Rect(_) | Type::Frame(_)) => {
            render_state
                .surfaces
                .draw_rect_to(surface_id, shape, paint, outset, inset);
        }
        (_, Type::Circle) => {
            render_state
                .surfaces
                .draw_circle_to(surface_id, shape, paint, outset, inset);
        }
        (_, Type::Path(_)) | (_, Type::Bool(_)) => {
            render_state
                .surfaces
                .draw_path_to(surface_id, shape, paint, outset, inset);
        }
        (_, Type::Group(_)) => {
            // Groups can have fills but they propagate them to their children
        }
        _ => unreachable!("This shape should not have fills"),
    }
}