use crate::aes::Aesthetic;
use crate::coord::Coord;
use crate::data::DataFrame;
use crate::position::identity::PositionIdentity;
use crate::position::Position;
use crate::render::backend::{DrawBackend, LineStyle, Linetype, RectStyle};
use crate::render::RenderError;
use crate::scale::ScaleSet;
use crate::stat::smooth::{SmoothMethod, StatSmooth};
use crate::stat::Stat;
use crate::theme::Theme;

use super::{Geom, GeomParams};

/// Smooth line with optional confidence ribbon.
pub struct GeomSmooth {
    pub color: (u8, u8, u8),
    pub fill: (u8, u8, u8),
    pub line_width: f64,
    pub alpha: f64,
    pub se: bool,
    pub n_points: usize,
    pub method: SmoothMethod,
}

impl Default for GeomSmooth {
    fn default() -> Self {
        GeomSmooth {
            color: (51, 102, 204),
            fill: (51, 102, 204),
            line_width: 1.5,
            alpha: 0.2,
            se: true,
            n_points: 80,
            method: SmoothMethod::Lm,
        }
    }
}

impl GeomSmooth {
    /// Use LOESS smoothing with the given span.
    pub fn loess(mut self, span: f64) -> Self {
        self.method = SmoothMethod::Loess { span };
        self
    }
}

impl Geom for GeomSmooth {
    fn draw(
        &self,
        data: &DataFrame,
        coord: &dyn Coord,
        scales: &ScaleSet,
        _theme: &Theme,
        backend: &mut dyn DrawBackend,
    ) -> Result<(), RenderError> {
        let x_col = data
            .column("x")
            .ok_or(RenderError::MissingAesthetic("x".into()))?;
        let y_col = data
            .column("y")
            .ok_or(RenderError::MissingAesthetic("y".into()))?;
        let ymin_col = data.column("ymin");
        let ymax_col = data.column("ymax");
        let color_col = data.column("color");
        let fill_col = data.column("fill");

        let plot_area = backend.plot_area();
        let x_scale = scales.get(&Aesthetic::X);
        let y_scale = scales.get(&Aesthetic::Y);

        // If there's a color/fill aesthetic, draw separate smooths per group
        if let Some(cc) = color_col.or(fill_col) {
            let mut groups: Vec<(String, Vec<usize>)> = Vec::new();
            for (i, v) in cc.iter().enumerate() {
                let key = v.to_group_key();
                if let Some(entry) = groups.iter_mut().find(|(k, _)| k == &key) {
                    entry.1.push(i);
                } else {
                    groups.push((key, vec![i]));
                }
            }

            for (_, indices) in &groups {
                let first_idx = indices[0];

                // Determine colors from mapped aesthetics
                let line_color = color_col
                    .and_then(|c| scales.map_color(&Aesthetic::Color, &c[first_idx]))
                    .unwrap_or(self.color);
                let ribbon_fill = fill_col
                    .and_then(|f| scales.map_color(&Aesthetic::Fill, &f[first_idx]))
                    .or_else(|| {
                        color_col.and_then(|c| scales.map_color(&Aesthetic::Color, &c[first_idx]))
                    })
                    .unwrap_or(self.fill);

                // Draw confidence ribbon
                if self.se {
                    if let (Some(ymin), Some(ymax)) = (ymin_col, ymax_col) {
                        let mut upper_points: Vec<(f64, f64)> = Vec::new();
                        let mut lower_points: Vec<(f64, f64)> = Vec::new();

                        for &i in indices {
                            let nx = x_scale.map(|s| s.map(&x_col[i])).unwrap_or(0.0);
                            let ny_max = y_scale.map(|s| s.map(&ymax[i])).unwrap_or(0.0);
                            let ny_min = y_scale.map(|s| s.map(&ymin[i])).unwrap_or(0.0);

                            upper_points.push(coord.transform((nx, ny_max), &plot_area));
                            lower_points.push(coord.transform((nx, ny_min), &plot_area));
                        }

                        let mut polygon = upper_points;
                        lower_points.reverse();
                        polygon.extend(lower_points);

                        if polygon.len() >= 3 {
                            backend.draw_polygon(
                                &polygon,
                                &RectStyle {
                                    fill: Some(ribbon_fill),
                                    stroke: None,
                                    stroke_width: 0.0,
                                    alpha: self.alpha,
                                    clip: true,
                                },
                            )?;
                        }
                    }
                }

                // Draw fitted line
                let points: Vec<(f64, f64)> = indices
                    .iter()
                    .map(|&i| {
                        let nx = x_scale.map(|s| s.map(&x_col[i])).unwrap_or(0.0);
                        let ny = y_scale.map(|s| s.map(&y_col[i])).unwrap_or(0.0);
                        coord.transform((nx, ny), &plot_area)
                    })
                    .collect();

                if points.len() >= 2 {
                    backend.draw_line(
                        &points,
                        &LineStyle {
                            color: line_color,
                            alpha: 1.0,
                            width: self.line_width,
                            linetype: Linetype::Solid,
                        },
                    )?;
                }
            }
        } else {
            // No grouping — original behavior with fixed colors

            // Draw confidence ribbon first (behind line)
            if self.se {
                if let (Some(ymin), Some(ymax)) = (ymin_col, ymax_col) {
                    let mut upper_points: Vec<(f64, f64)> = Vec::new();
                    let mut lower_points: Vec<(f64, f64)> = Vec::new();

                    for i in 0..data.nrows() {
                        let nx = x_scale.map(|s| s.map(&x_col[i])).unwrap_or(0.0);
                        let ny_max = y_scale.map(|s| s.map(&ymax[i])).unwrap_or(0.0);
                        let ny_min = y_scale.map(|s| s.map(&ymin[i])).unwrap_or(0.0);

                        upper_points.push(coord.transform((nx, ny_max), &plot_area));
                        lower_points.push(coord.transform((nx, ny_min), &plot_area));
                    }

                    // Build polygon: upper left-to-right, then lower right-to-left
                    let mut polygon = upper_points;
                    lower_points.reverse();
                    polygon.extend(lower_points);

                    if polygon.len() >= 3 {
                        backend.draw_polygon(
                            &polygon,
                            &RectStyle {
                                fill: Some(self.fill),
                                stroke: None,
                                stroke_width: 0.0,
                                alpha: self.alpha,
                                clip: true,
                            },
                        )?;
                    }
                }
            }

            // Draw fitted line
            let points: Vec<(f64, f64)> = (0..data.nrows())
                .map(|i| {
                    let nx = x_scale.map(|s| s.map(&x_col[i])).unwrap_or(0.0);
                    let ny = y_scale.map(|s| s.map(&y_col[i])).unwrap_or(0.0);
                    coord.transform((nx, ny), &plot_area)
                })
                .collect();

            if points.len() >= 2 {
                backend.draw_line(
                    &points,
                    &LineStyle {
                        color: self.color,
                        alpha: 1.0,
                        width: self.line_width,
                        linetype: Linetype::Solid,
                    },
                )?;
            }
        }

        Ok(())
    }

    fn required_aes(&self) -> Vec<Aesthetic> {
        vec![Aesthetic::X, Aesthetic::Y]
    }

    fn default_stat(&self) -> Box<dyn Stat> {
        Box::new(StatSmooth {
            n_points: self.n_points,
            se: self.se,
            method: self.method.clone(),
        })
    }

    fn default_position(&self) -> Box<dyn Position> {
        Box::new(PositionIdentity)
    }

    fn default_params(&self) -> GeomParams {
        GeomParams::default()
    }

    fn name(&self) -> &str {
        "smooth"
    }

    fn set_series_color(&mut self, color: (u8, u8, u8)) {
        self.color = color;
        self.fill = color;
    }
}
