OneCAD-Draft/src/io/pdf_export.rs

// PDF export — converts the paper-space wire model to a PDF file using printpdf.
//
// Each WireModel becomes a sequence of DrawLine operations.  NaN values in the
// points array act as segment separators (pen-up).
//
// Coordinate system: CAD uses mm units with origin at bottom-left and Y up.
// printpdf's Point::new(Mm, Mm) also has origin at bottom-left, so no Y-flip
// is needed — we shift the coordinates by (offset_x, offset_y) to place the
// drawing origin at the paper origin.

use crate::io::plot_style::PlotStyleTable;
use crate::scene::hatch_model::{HatchModel, HatchPattern};
use crate::scene::WireModel;
use printpdf::{
    Color, Line, LineCapStyle, LineJoinStyle, LinePoint, Mm, Op, PaintMode, PdfDocument, PdfPage,
    PdfSaveOptions, Point, Polygon, PolygonRing, Pt, Rgb, WindingOrder,
};
use std::io::Write;
use std::path::Path;

// ── Public entry point ────────────────────────────────────────────────────

/// Export `wires` to a PDF file.
///
/// - `paper_w` / `paper_h`: page dimensions in mm (already swapped for 90°/270° by caller).
/// - `offset_x` / `offset_y`: added to every wire coordinate so the drawing
///   origin maps to the bottom-left corner of the page.
/// - `rotation_deg`: 0 | 90 | 180 | 270 — rotates the entire drawing on the page.
pub fn export_pdf(
    wires: &[WireModel],
    hatches: &[HatchModel],
    wipeouts: &[HatchModel],
    paper_w: f64,
    paper_h: f64,
    offset_x: f32,
    offset_y: f32,
    rotation_deg: i32,
    path: &Path,
    plot_style: Option<&PlotStyleTable>,
) -> Result<(), String> {
    let bytes = build_pdf(
        wires,
        hatches,
        wipeouts,
        paper_w as f32,
        paper_h as f32,
        offset_x,
        offset_y,
        rotation_deg,
        plot_style,
    );
    let mut file = std::fs::File::create(path).map_err(|e| e.to_string())?;
    file.write_all(&bytes).map_err(|e| e.to_string())
}

/// Show a PDF save-file dialog and return the chosen path (or None if cancelled).
pub async fn pick_pdf_path_owned(stem: String) -> Option<std::path::PathBuf> {
    rfd::AsyncFileDialog::new()
        .set_title("Export as PDF")
        .set_file_name(&format!("{stem}.pdf"))
        .add_filter("PDF Files", &["pdf"])
        .add_filter("All Files", &["*"])
        .save_file()
        .await
        .map(|h| h.path().to_path_buf())
}

// ── PDF builder ───────────────────────────────────────────────────────────

fn build_pdf(
    wires: &[WireModel],
    hatches: &[HatchModel],
    wipeouts: &[HatchModel],
    paper_w: f32,
    paper_h: f32,
    ox: f32,
    oy: f32,
    rotation_deg: i32,
    plot_style: Option<&PlotStyleTable>,
) -> Vec<u8> {
    let mut doc = PdfDocument::new("Open CAD Studio Export");
    let mut ops: Vec<Op> = Vec::new();

    // White page background.
    ops.push(Op::SetFillColor {
        col: Color::Rgb(Rgb {
            r: 1.0,
            g: 1.0,
            b: 1.0,
            icc_profile: None,
        }),
    });
    ops.push(Op::DrawRectangle {
        rectangle: printpdf::Rect::from_wh(Mm(paper_w).into(), Mm(paper_h).into()),
    });

    // Round line caps/joins for CAD aesthetics.
    ops.push(Op::SetLineCapStyle {
        cap: LineCapStyle::Round,
    });
    ops.push(Op::SetLineJoinStyle {
        join: LineJoinStyle::Round,
    });

    // Apply rotation transform if needed.
    // PDF uses mm-based coordinate system with origin at bottom-left.
    // We save state, apply a CTM, then restore it after drawing.
    let needs_rotation = rotation_deg != 0;
    if needs_rotation {
        let (cos_a, sin_a, tx, ty) = match rotation_deg {
            90 => (0.0_f64, 1.0_f64, 0.0, paper_h as f64),
            180 => (-1.0_f64, 0.0_f64, paper_w as f64, paper_h as f64),
            270 => (0.0_f64, -1.0_f64, paper_w as f64, 0.0),
            _ => (1.0_f64, 0.0_f64, 0.0, 0.0),
        };
        // PDF CTM: [a b c d e f] = [cos sin -sin cos tx ty]
        ops.push(Op::SaveGraphicsState);
        // Convert mm translation to points (1 mm = 2.834645 pt).
        let tx_pt = (tx * 2.834645) as f32;
        let ty_pt = (ty * 2.834645) as f32;
        ops.push(Op::SetTransformationMatrix {
            matrix: printpdf::CurTransMat::Raw([
                cos_a as f32,
                sin_a as f32,
                -(sin_a as f32),
                cos_a as f32,
                tx_pt,
                ty_pt,
            ]),
        });
    }

    // mm to PDF points (1 mm = 2.834645 pt).
    const MM_TO_PT: f32 = 2.834645;
    // Screen px to PDF points (approximate at 96 dpi).
    const PX_TO_PT: f32 = 0.35278;

    // ── Hatch / wipeout fills (rendered before wires so wires draw on top,
    //    matching paper_canvas ordering). Each `emit_hatch` sets its own
    //    fill / stroke colour, so the wire pass below starts fresh.
    for hatch in wipeouts.iter().chain(hatches.iter()) {
        emit_hatch(&mut ops, hatch, ox, oy);
    }

    let mut last_color: Option<[f32; 3]> = None;
    let mut last_lw: Option<f32> = None;

    for wire in wires {
        let [mut r, mut g, mut b, a] = wire.color;
        if a < 0.01 {
            continue;
        }
        // Skip the paper-boundary wire — the white PDF background already provides it.
        if wire.name == "__paper_boundary__" {
            continue;
        }
        // Apply CTB plot style table overrides (color + lineweight).
        let mut lw_override: Option<f32> = None;
        if let Some(ctb) = plot_style {
            if wire.aci > 0 {
                if let Some([cr, cg, cb]) = ctb.resolve_color(wire.aci) {
                    r = cr;
                    g = cg;
                    b = cb;
                }
                lw_override = ctb
                    .resolve_lineweight(wire.aci)
                    .map(|mm| (mm * MM_TO_PT).max(0.1));
            }
        }
        // Near-white and near-yellow (viewport active border) → dark grey for print
        // (only when no CTB override was applied).
        if lw_override.is_none() {
            let is_light = r > 0.80 && g > 0.80 && b > 0.80;
            let is_yellow = r > 0.80 && g > 0.70 && b < 0.30;
            let is_cyan = r < 0.30 && g > 0.70 && b > 0.70;
            if is_light || is_yellow {
                r = 0.0;
                g = 0.0;
                b = 0.0;
            } else if is_cyan {
                // Viewport border: print as dark blue.
                r = 0.0;
                g = 0.15;
                b = 0.50;
            }
        }

        if last_color
            .map(|c| (c[0] - r).abs() > 0.01 || (c[1] - g).abs() > 0.01 || (c[2] - b).abs() > 0.01)
            .unwrap_or(true)
        {
            ops.push(Op::SetOutlineColor {
                col: Color::Rgb(Rgb {
                    r,
                    g,
                    b,
                    icc_profile: None,
                }),
            });
            last_color = Some([r, g, b]);
        }

        // Line weight: CTB override (in pt) or screen px → points.
        let lw_pt = lw_override.unwrap_or_else(|| (wire.line_weight_px * PX_TO_PT).max(0.1));
        if last_lw.map(|l| (l - lw_pt).abs() > 0.01).unwrap_or(true) {
            ops.push(Op::SetOutlineThickness { pt: Pt(lw_pt) });
            last_lw = Some(lw_pt);
        }

        // Emit segments (NaN = pen-up).
        let mut segment: Vec<LinePoint> = Vec::new();
        for &[x, y, _z] in &wire.points {
            if x.is_nan() || y.is_nan() {
                flush_line(&mut ops, &segment);
                segment.clear();
            } else {
                segment.push(LinePoint {
                    p: Point::new(Mm(x + ox), Mm(y + oy)),
                    bezier: false,
                });
            }
        }
        flush_line(&mut ops, &segment);
    }

    if needs_rotation {
        ops.push(Op::RestoreGraphicsState);
    }

    let page = PdfPage::new(Mm(paper_w), Mm(paper_h), ops);
    doc.pages.push(page);

    let mut warnings = Vec::new();
    doc.save(&PdfSaveOptions::default(), &mut warnings)
}

fn flush_line(ops: &mut Vec<Op>, pts: &[LinePoint]) {
    if pts.len() < 2 {
        return;
    }
    ops.push(Op::DrawLine {
        line: Line {
            points: pts.to_vec(),
            is_closed: false,
        },
    });
}

/// Emit a single hatch / wipeout as a filled (or stroked, for pattern fills)
/// polygon. NaN sentinels in `hatch.boundary` split the path into multiple
/// rings so islands and holes render correctly under the even-odd rule.
/// Mirrors `scene::paper_canvas::draw_hatch`: solid → fill, pattern → outline,
/// gradient → solid fill of the averaged colour.
fn emit_hatch(ops: &mut Vec<Op>, hatch: &HatchModel, ox: f32, oy: f32) {
    if hatch.boundary.is_empty() {
        return;
    }
    let [r, g, b, a] = hatch.color;
    if a < 0.01 {
        return;
    }
    let world_ox = hatch.world_origin[0] as f32;
    let world_oy = hatch.world_origin[1] as f32;

    // Split the boundary into rings on every NaN-NaN separator.
    let mut rings: Vec<PolygonRing> = Vec::new();
    let mut current: Vec<LinePoint> = Vec::new();
    for &[bx, by] in hatch.boundary.iter() {
        if bx.is_nan() || by.is_nan() {
            if current.len() >= 3 {
                rings.push(PolygonRing { points: std::mem::take(&mut current) });
            } else {
                current.clear();
            }
            continue;
        }
        current.push(LinePoint {
            p: Point::new(Mm(bx + world_ox + ox), Mm(by + world_oy + oy)),
            bezier: false,
        });
    }
    if current.len() >= 3 {
        rings.push(PolygonRing { points: current });
    }
    if rings.is_empty() {
        return;
    }

    let (paint_mode, fill_color) = match &hatch.pattern {
        HatchPattern::Solid => (PaintMode::Fill, [r, g, b]),
        HatchPattern::Pattern(_) => {
            // Pattern fills are emitted as raster line segments below; the
            // outline polygon path itself is skipped because pattern
            // hatches in real DXF do not draw their boundary as part of
            // the fill.
            (PaintMode::Clip, [r, g, b]) // sentinel — handled below
        }
        HatchPattern::Gradient { color2, .. } => {
            // PDF gradients are stored in resource dictionaries; for the
            // fast path we average the two colours, matching paper_canvas.
            let avg = [
                (r + color2[0]) * 0.5,
                (g + color2[1]) * 0.5,
                (b + color2[2]) * 0.5,
            ];
            (PaintMode::Fill, avg)
        }
    };

    // Pattern hatches: rasterise the family lines clipped to the boundary
    // and emit each as a stroked line. Skips the polygon outline entirely.
    if matches!(hatch.pattern, HatchPattern::Pattern(_)) {
        let segments = hatch.pattern_segments();
        if segments.is_empty() {
            return;
        }
        ops.push(Op::SetOutlineColor {
            col: Color::Rgb(Rgb {
                r,
                g,
                b,
                icc_profile: None,
            }),
        });
        for [a, b_pt] in segments {
            ops.push(Op::DrawLine {
                line: Line {
                    points: vec![
                        LinePoint {
                            p: Point::new(Mm(a[0] + ox), Mm(a[1] + oy)),
                            bezier: false,
                        },
                        LinePoint {
                            p: Point::new(Mm(b_pt[0] + ox), Mm(b_pt[1] + oy)),
                            bezier: false,
                        },
                    ],
                    is_closed: false,
                },
            });
        }
        return;
    }

    // Solid / gradient: filled polygon path.
    if matches!(paint_mode, PaintMode::Fill | PaintMode::FillStroke) {
        ops.push(Op::SetFillColor {
            col: Color::Rgb(Rgb {
                r: fill_color[0],
                g: fill_color[1],
                b: fill_color[2],
                icc_profile: None,
            }),
        });
    }
    ops.push(Op::DrawPolygon {
        polygon: Polygon {
            rings,
            mode: paint_mode,
            winding_order: WindingOrder::EvenOdd,
        },
    });
}