use super::{filters, RenderState, Shape, SurfaceId};
use crate::{
    error::Result,
    math::Rect,
    shapes::{
        calculate_position_data, calculate_text_layout_data, set_paint_fill, ParagraphBuilderGroup,
        Stroke, StrokeKind, TextContent,
    },
    utils::{get_fallback_fonts, get_font_collection},
};
use skia_safe::{
    self as skia,
    canvas::SaveLayerRec,
    textlayout::{ParagraphBuilder, StyleMetrics, TextDecoration, TextStyle},
    Canvas, ImageFilter, Paint, Path,
};

pub fn stroke_paragraph_builder_group_from_text(
    text_content: &TextContent,
    stroke: &Stroke,
    bounds: &Rect,
    use_shadow: Option<bool>,
) -> (Vec<ParagraphBuilderGroup>, Option<f32>) {
    let fallback_fonts = get_fallback_fonts();
    let fonts = get_font_collection();
    let mut paragraph_group = Vec::new();
    let remove_stroke_alpha = use_shadow.unwrap_or(false) && !stroke.is_transparent();
    let mut group_layer_opacity: Option<f32> = None;

    for paragraph in text_content.paragraphs() {
        let mut stroke_paragraphs_map: std::collections::HashMap<usize, ParagraphBuilder> =
            std::collections::HashMap::new();

        for span in paragraph.children().iter() {
            let (stroke_paints, stroke_layer_opacity) =
                get_text_stroke_paints(stroke, bounds, remove_stroke_alpha);

            if group_layer_opacity.is_none() {
                group_layer_opacity = stroke_layer_opacity;
            }

            let text: String = span.apply_text_transform();

            for (paint_idx, stroke_paint) in stroke_paints.iter().enumerate() {
                let builder = stroke_paragraphs_map.entry(paint_idx).or_insert_with(|| {
                    let paragraph_style = paragraph.paragraph_to_style();
                    ParagraphBuilder::new(&paragraph_style, fonts)
                });
                let stroke_paint = stroke_paint.clone();
                let remove_alpha = use_shadow.unwrap_or(false) && !span.is_transparent();
                let stroke_style = span.to_stroke_style(
                    &stroke_paint,
                    fallback_fonts,
                    remove_alpha,
                    paragraph.line_height(),
                );
                builder.push_style(&stroke_style);
                builder.add_text(&text);
            }
        }

        let stroke_paragraphs: Vec<ParagraphBuilder> = (0..stroke_paragraphs_map.len())
            .filter_map(|i| stroke_paragraphs_map.remove(&i))
            .collect();

        paragraph_group.push(stroke_paragraphs);
    }

    (paragraph_group, group_layer_opacity)
}

fn get_text_stroke_paints(
    stroke: &Stroke,
    bounds: &Rect,
    remove_stroke_alpha: bool,
) -> (Vec<Paint>, Option<f32>) {
    let mut paints = Vec::new();
    let mut layer_opacity: Option<f32> = None;

    let stroke_opacity = stroke.fill.opacity();
    let needs_opacity_layer = stroke_opacity < 1.0 && !remove_stroke_alpha;

    let fill_for_paint = |paint: &mut Paint| {
        if needs_opacity_layer {
            let opaque_fill = stroke.fill.with_full_opacity();
            set_paint_fill(paint, &opaque_fill, bounds, remove_stroke_alpha);
        } else {
            set_paint_fill(paint, &stroke.fill, bounds, remove_stroke_alpha);
        }
    };

    if needs_opacity_layer {
        layer_opacity = Some(stroke_opacity);
    }

    match stroke.kind {
        StrokeKind::Inner => {
            // Just the stroke paint — mask+SrcIn+DstOver layering is handled
            // by render_inner_stroke_on_canvas.
            let mut paint = skia::Paint::default();
            paint.set_style(skia::PaintStyle::Stroke);
            paint.set_anti_alias(true);
            paint.set_stroke_width(stroke.width * 2.0);
            if remove_stroke_alpha {
                paint.set_color(skia::Color::BLACK);
                paint.set_alpha(255);
            } else {
                fill_for_paint(&mut paint);
            }
            paints.push(paint);
        }
        StrokeKind::Center => {
            let mut paint = skia::Paint::default();
            paint.set_style(skia::PaintStyle::Stroke);
            paint.set_anti_alias(true);
            paint.set_stroke_width(stroke.width);
            fill_for_paint(&mut paint);
            paints.push(paint);
        }
        StrokeKind::Outer => {
            let mut paint = skia::Paint::default();
            paint.set_style(skia::PaintStyle::Stroke);
            paint.set_blend_mode(skia::BlendMode::DstOver);
            paint.set_anti_alias(true);
            paint.set_stroke_width(stroke.width * 2.0);
            fill_for_paint(&mut paint);
            paints.push(paint);

            let mut paint = skia::Paint::default();
            paint.set_style(skia::PaintStyle::Fill);
            paint.set_blend_mode(skia::BlendMode::Clear);
            paint.set_color(skia::Color::TRANSPARENT);
            paint.set_anti_alias(true);
            paints.push(paint);
        }
    }

    (paints, layer_opacity)
}

#[allow(clippy::too_many_arguments)]
pub fn render_with_bounds_outset(
    render_state: Option<&mut RenderState>,
    canvas: Option<&Canvas>,
    shape: &Shape,
    paragraph_builders: &mut [Vec<ParagraphBuilder>],
    surface_id: Option<SurfaceId>,
    shadow: Option<&Paint>,
    blur: Option<&ImageFilter>,
    stroke_bounds_outset: f32,
    fill_inset: Option<f32>,
    layer_opacity: Option<f32>,
) -> Result<()> {
    if let Some(render_state) = render_state {
        let target_surface = surface_id.unwrap_or(SurfaceId::Fills);

        if let Some(blur_filter) = blur {
            let mut text_bounds = shape
                .get_text_content()
                .calculate_bounds(shape, false)
                .to_rect();
            if stroke_bounds_outset > 0.0 {
                text_bounds.inset((-stroke_bounds_outset, -stroke_bounds_outset));
            }
            let bounds = blur_filter.compute_fast_bounds(text_bounds);
            if bounds.is_finite() && bounds.width() > 0.0 && bounds.height() > 0.0 {
                let blur_filter_clone = blur_filter.clone();
                if filters::render_with_filter_surface(
                    render_state,
                    bounds,
                    target_surface,
                    |state, temp_surface| {
                        let temp_canvas = state.surfaces.canvas(temp_surface);
                        render_text_on_canvas(
                            temp_canvas,
                            shape,
                            paragraph_builders,
                            shadow,
                            Some(&blur_filter_clone),
                            fill_inset,
                            layer_opacity,
                        );
                        Ok(())
                    },
                )? {
                    return Ok(());
                }
            }
        }

        let canvas = render_state.surfaces.canvas_and_mark_dirty(target_surface);
        render_text_on_canvas(
            canvas,
            shape,
            paragraph_builders,
            shadow,
            blur,
            fill_inset,
            layer_opacity,
        );
        return Ok(());
    }

    if let Some(canvas) = canvas {
        render_text_on_canvas(
            canvas,
            shape,
            paragraph_builders,
            shadow,
            blur,
            fill_inset,
            layer_opacity,
        );
    }
    Ok(())
}

#[allow(clippy::too_many_arguments)]
pub fn render(
    render_state: Option<&mut RenderState>,
    canvas: Option<&Canvas>,
    shape: &Shape,
    paragraph_builders: &mut [Vec<ParagraphBuilder>],
    surface_id: Option<SurfaceId>,
    shadow: Option<&Paint>,
    blur: Option<&ImageFilter>,
    fill_inset: Option<f32>,
    layer_opacity: Option<f32>,
) -> Result<()> {
    render_with_bounds_outset(
        render_state,
        canvas,
        shape,
        paragraph_builders,
        surface_id,
        shadow,
        blur,
        0.0,
        fill_inset,
        layer_opacity,
    )
}

fn render_text_on_canvas(
    canvas: &Canvas,
    shape: &Shape,
    paragraph_builders: &mut [Vec<ParagraphBuilder>],
    shadow: Option<&Paint>,
    blur: Option<&ImageFilter>,
    fill_inset: Option<f32>,
    layer_opacity: Option<f32>,
) {
    if let Some(blur_filter) = blur {
        let mut blur_paint = Paint::default();
        blur_paint.set_image_filter(blur_filter.clone());
        let blur_layer = SaveLayerRec::default().paint(&blur_paint);
        canvas.save_layer(&blur_layer);
    }

    if let Some(shadow_paint) = shadow {
        let layer_rec = SaveLayerRec::default().paint(shadow_paint);
        canvas.save_layer(&layer_rec);
        draw_text(canvas, shape, paragraph_builders, layer_opacity);
        canvas.restore();
    } else if let Some(eps) = fill_inset.filter(|&e| e > 0.0) {
        if let Some(erode) = skia_safe::image_filters::erode((eps, eps), None, None) {
            let mut layer_paint = Paint::default();
            layer_paint.set_image_filter(erode);
            let layer_rec = SaveLayerRec::default().paint(&layer_paint);
            canvas.save_layer(&layer_rec);
            draw_text(canvas, shape, paragraph_builders, layer_opacity);
            canvas.restore();
        } else {
            draw_text(canvas, shape, paragraph_builders, layer_opacity);
        }
    } else {
        draw_text(canvas, shape, paragraph_builders, layer_opacity);
    }

    if blur.is_some() {
        canvas.restore();
    }

    canvas.restore();
}

/// Lays out and paints paragraph builders without any layer management.
fn paint_text(
    canvas: &Canvas,
    shape: &Shape,
    paragraph_builder_groups: &mut [Vec<ParagraphBuilder>],
) {
    let text_content = shape.get_text_content();
    let layout_info =
        calculate_text_layout_data(shape, text_content, paragraph_builder_groups, true);

    for para in &layout_info.paragraphs {
        para.paragraph.paint(canvas, (para.x, para.y));
        for deco in &para.decorations {
            draw_text_decorations(
                canvas,
                &deco.text_style,
                Some(deco.y),
                deco.thickness,
                deco.left,
                deco.width,
            );
        }
    }
}

fn draw_text(
    canvas: &Canvas,
    shape: &Shape,
    paragraph_builder_groups: &mut [Vec<ParagraphBuilder>],
    layer_opacity: Option<f32>,
) {
    if let Some(opacity) = layer_opacity {
        let mut opacity_paint = Paint::default();
        opacity_paint.set_alpha_f(opacity);
        let layer_rec = SaveLayerRec::default().paint(&opacity_paint);
        canvas.save_layer(&layer_rec);
    } else {
        canvas.save_layer(&SaveLayerRec::default());
    }

    paint_text(canvas, shape, paragraph_builder_groups);
}

/// Renders an inner stroke using mask + SrcIn + DstOver layer structure.
///
/// Layer structure:
///   saveLayer()           — outer layer
///     saveLayer()         — mask group (isolation)
///       paint mask        — opaque fill as clip mask
///       saveLayer(SrcIn)  — clips stroke to mask shape
///         paint stroke
///       restore
///     restore
///     saveLayer(DstOver)  — fill behind the stroke
///       paint fill
///     restore
///   restore
#[allow(clippy::too_many_arguments)]
fn render_inner_stroke_on_canvas(
    canvas: &Canvas,
    shape: &Shape,
    mask_builders: &mut [Vec<ParagraphBuilder>],
    stroke_builders: &mut [Vec<ParagraphBuilder>],
    fill_builders: &mut [Vec<ParagraphBuilder>],
    blur: Option<&ImageFilter>,
    layer_opacity: Option<f32>,
) {
    if let Some(blur_filter) = blur {
        let mut blur_paint = Paint::default();
        blur_paint.set_image_filter(blur_filter.clone());
        canvas.save_layer(&SaveLayerRec::default().paint(&blur_paint));
    }

    // Opacity layer wraps the entire composition
    if let Some(opacity) = layer_opacity {
        let mut opacity_paint = Paint::default();
        opacity_paint.set_alpha_f(opacity);
        canvas.save_layer(&SaveLayerRec::default().paint(&opacity_paint));
    }

    // Outer layer
    canvas.save_layer(&SaveLayerRec::default());

    // Mask group layer (isolates mask from parent surface content)
    canvas.save_layer(&SaveLayerRec::default());

    // Draw opaque mask (full alpha text shape)
    paint_text(canvas, shape, mask_builders);

    // SrcIn layer — only keeps stroke pixels where mask has alpha
    let mut src_in_paint = Paint::default();
    src_in_paint.set_blend_mode(skia::BlendMode::SrcIn);
    canvas.save_layer(&SaveLayerRec::default().paint(&src_in_paint));

    // Draw stroke
    paint_text(canvas, shape, stroke_builders);

    canvas.restore(); // SrcIn layer
    canvas.restore(); // mask group layer

    // Fill with DstOver (behind the stroke result)
    let mut dst_over_paint = Paint::default();
    dst_over_paint.set_blend_mode(skia::BlendMode::DstOver);
    canvas.save_layer(&SaveLayerRec::default().paint(&dst_over_paint));

    paint_text(canvas, shape, fill_builders);

    canvas.restore(); // DstOver layer
    canvas.restore(); // outer layer

    if layer_opacity.is_some() {
        canvas.restore(); // opacity layer
    }

    if blur.is_some() {
        canvas.restore(); // blur layer
    }
}

/// Public API for rendering inner strokes with mask+SrcIn+DstOver approach.
#[allow(clippy::too_many_arguments)]
pub fn render_inner_stroke(
    render_state: Option<&mut RenderState>,
    canvas: Option<&Canvas>,
    shape: &Shape,
    mask_builders: &mut [Vec<ParagraphBuilder>],
    stroke_builders: &mut [Vec<ParagraphBuilder>],
    fill_builders: &mut [Vec<ParagraphBuilder>],
    surface_id: Option<SurfaceId>,
    blur: Option<&ImageFilter>,
    stroke_bounds_outset: f32,
    layer_opacity: Option<f32>,
) -> Result<()> {
    if let Some(render_state) = render_state {
        let target_surface = surface_id.unwrap_or(SurfaceId::Fills);

        if let Some(blur_filter) = blur {
            let mut text_bounds = shape
                .get_text_content()
                .calculate_bounds(shape, false)
                .to_rect();
            if stroke_bounds_outset > 0.0 {
                text_bounds.inset((-stroke_bounds_outset, -stroke_bounds_outset));
            }
            let bounds = blur_filter.compute_fast_bounds(text_bounds);
            if bounds.is_finite() && bounds.width() > 0.0 && bounds.height() > 0.0 {
                let blur_filter_clone = blur_filter.clone();
                if filters::render_with_filter_surface(
                    render_state,
                    bounds,
                    target_surface,
                    |state, temp_surface| {
                        let temp_canvas = state.surfaces.canvas(temp_surface);
                        render_inner_stroke_on_canvas(
                            temp_canvas,
                            shape,
                            mask_builders,
                            stroke_builders,
                            fill_builders,
                            Some(&blur_filter_clone),
                            layer_opacity,
                        );
                        Ok(())
                    },
                )? {
                    return Ok(());
                }
            }
        }

        let canvas = render_state.surfaces.canvas_and_mark_dirty(target_surface);
        render_inner_stroke_on_canvas(
            canvas,
            shape,
            mask_builders,
            stroke_builders,
            fill_builders,
            blur,
            layer_opacity,
        );
        return Ok(());
    }

    if let Some(canvas) = canvas {
        render_inner_stroke_on_canvas(
            canvas,
            shape,
            mask_builders,
            stroke_builders,
            fill_builders,
            blur,
            layer_opacity,
        );
    }
    Ok(())
}

fn draw_text_decorations(
    canvas: &Canvas,
    text_style: &TextStyle,
    y: Option<f32>,
    thickness: f32,
    text_left: f32,
    text_width: f32,
) {
    if let Some(y) = y {
        let r = skia_safe::Rect::new(
            text_left,
            y - thickness / 2.0,
            text_left + text_width,
            y + thickness / 2.0,
        );
        let mut decoration_paint = text_style.foreground();
        decoration_paint.set_anti_alias(true);
        canvas.draw_rect(r, &decoration_paint);
    }
}

pub fn calculate_decoration_metrics(
    style_metrics: &Vec<(usize, &StyleMetrics)>,
    line_baseline: f32,
) -> (f32, Option<f32>, f32, Option<f32>) {
    let mut max_underline_thickness: f32 = 0.0;
    let mut underline_y = None;
    let mut max_strike_thickness: f32 = 0.0;
    let mut strike_y = None;
    for (_style_start, style_metric) in style_metrics.iter() {
        let font_metrics = style_metric.font_metrics;
        let font_size = font_metrics
            .cap_height
            .abs()
            .max(font_metrics.x_height.abs());
        let min_thickness = (font_size * 0.06).max(1.0);

        // Magic numbers for line thickness partially based on Chromium
        // (see https://source.chromium.org/chromium/chromium/src/+/main:ui/gfx/render_text.cc
        let raw_font_size = style_metric.text_style.font_size();
        let thickness_factor = raw_font_size.powf(0.4) * 6.0 / 18.0;

        let thickness = (font_metrics.underline_thickness().unwrap_or(1.0) * thickness_factor)
            .max(min_thickness);

        if style_metric.text_style.decoration().ty == TextDecoration::UNDERLINE {
            // Same gap from baseline to underline as in Chromium
            // (see https://source.chromium.org/chromium/chromium/src/+/main:ui/gfx/render_text.cc
            let gap_scaling = raw_font_size * 1.0 / 9.0;
            let y = line_baseline + gap_scaling;

            max_underline_thickness = max_underline_thickness.max(thickness);
            underline_y = Some(y);
        }
        if style_metric.text_style.decoration().ty == TextDecoration::LINE_THROUGH {
            let y = line_baseline
                + font_metrics
                    .strikeout_position()
                    .unwrap_or(-font_metrics.cap_height / 2.0);
            max_strike_thickness = max_strike_thickness.max(thickness);
            strike_y = Some(y);
        }
    }
    (
        max_underline_thickness,
        underline_y,
        max_strike_thickness,
        strike_y,
    )
}

#[allow(dead_code)]
fn calculate_total_paragraphs_height(paragraphs: &mut [ParagraphBuilder], width: f32) -> f32 {
    paragraphs
        .iter_mut()
        .map(|p| {
            let mut paragraph = p.build();
            paragraph.layout(width);
            paragraph.height()
        })
        .sum()
}

#[allow(dead_code)]
fn calculate_all_paragraphs_height(
    paragraph_groups: &mut [Vec<ParagraphBuilder>],
    width: f32,
) -> f32 {
    paragraph_groups
        .iter_mut()
        .map(|group| {
            // For stroke groups, only count the first paragraph to avoid double-counting
            if group.len() > 1 {
                let mut paragraph = group[0].build();
                paragraph.layout(width);
                paragraph.height()
            } else {
                calculate_total_paragraphs_height(group, width)
            }
        })
        .sum()
}

// Render text paths (unused)
#[allow(dead_code)]
pub fn render_as_path(
    render_state: &mut RenderState,
    paths: &Vec<(Path, Paint)>,
    surface_id: Option<SurfaceId>,
) {
    let canvas = render_state
        .surfaces
        .canvas_and_mark_dirty(surface_id.unwrap_or(SurfaceId::Fills));

    for (path, paint) in paths {
        // Note: path can be empty
        canvas.draw_path(path, paint);
    }
}

#[allow(dead_code)]
pub fn render_position_data(
    render_state: &mut RenderState,
    surface_id: SurfaceId,
    shape: &Shape,
    text_content: &TextContent,
) {
    let position_data = calculate_position_data(shape, text_content, false);

    let mut paint = skia::Paint::default();
    paint.set_style(skia::PaintStyle::Stroke);
    paint.set_color(skia::Color::from_argb(255, 255, 0, 0));
    paint.set_stroke_width(2.);

    for pd in position_data {
        let rect = Rect::from_xywh(pd.x, pd.y, pd.width, pd.height);
        render_state
            .surfaces
            .canvas_and_mark_dirty(surface_id)
            .draw_rect(rect, &paint);
    }
}

// How to use it?
// Type::Text(text_content) => {
//     self.surfaces
//         .apply_mut(&[SurfaceId::Fills, SurfaceId::Strokes], |s| {
//             s.canvas().concat(&matrix);
//         });

//     let text_content = text_content.new_bounds(shape.selrect());
//     let paths = text_content.get_paths(antialias);

//     shadows::render_text_shadows(self, &shape, &paths, antialias);
//     text::render(self, &paths, None, None);

//     for stroke in shape.visible_strokes().rev() {
//         shadows::render_text_path_stroke_shadows(
//             self, &shape, &paths, stroke, antialias,
//         );
//         strokes::render_text_paths(self, &shape, stroke, &paths, None, None, antialias);
//         shadows::render_text_path_stroke_inner_shadows(
//             self, &shape, &paths, stroke, antialias,
//         );
//     }

//     shadows::render_text_inner_shadows(self, &shape, &paths, antialias);
// }