gridcraft/crates/xlsx/src/theme.rs

//! `theme1.xml`: colour scheme and font scheme.
//!
//! In the file the colour scheme is ordered dk1, lt1, dk2, lt2, accent1–6, hlink, folHlink,
//! while cell colour `theme` indices (and the model's `Theme.colors`) use lt1, dk1, lt2, dk2, ….

use std::fmt::Write as _;

use gridcraft_model::Theme;

use crate::xml::{El, esc_attr};

const SLOTS: [(&str, usize); 12] = [
    ("dk1", 1),
    ("lt1", 0),
    ("dk2", 3),
    ("lt2", 2),
    ("accent1", 4),
    ("accent2", 5),
    ("accent3", 6),
    ("accent4", 7),
    ("accent5", 8),
    ("accent6", 9),
    ("hlink", 10),
    ("folHlink", 11),
];

fn scheme_rgb(e: &El) -> Option<u32> {
    if let Some(c) = e.child("srgbClr").and_then(|c| c.attr("val")) {
        return u32::from_str_radix(c.trim(), 16).ok().map(|v| v & 0xFFFFFF);
    }
    if let Some(c) = e.child("sysClr") {
        if let Some(v) = c.attr("lastClr").and_then(|v| u32::from_str_radix(v.trim(), 16).ok()) {
            return Some(v & 0xFFFFFF);
        }
        return match c.attr("val") {
            Some("windowText") => Some(0x000000),
            Some("window") => Some(0xFFFFFF),
            _ => None,
        };
    }
    None
}

pub fn read_theme(root: &El) -> Theme {
    let mut t = Theme::default();
    if let Some(n) = root.attr("name") {
        t.name = n.to_string();
    }
    let Some(el) = root.child("themeElements") else { return t };
    if let Some(cs) = el.child("clrScheme") {
        for (name, idx) in SLOTS {
            if let Some(v) = cs.child(name).and_then(scheme_rgb)
                && let Some(slot) = t.colors.get_mut(idx)
            {
                *slot = v;
            }
        }
    }
    if let Some(fs) = el.child("fontScheme") {
        if let Some(f) = fs.path(&["majorFont", "latin"]).and_then(|l| l.attr("typeface")).filter(|f| !f.is_empty()) {
            t.major_font = f.to_string();
        }
        if let Some(f) = fs.path(&["minorFont", "latin"]).and_then(|l| l.attr("typeface")).filter(|f| !f.is_empty()) {
            t.minor_font = f.to_string();
        }
    }
    t
}

/// A minimal, schema-complete theme part for `t`.
pub fn write_theme(t: &Theme) -> String {
    let mut s = String::from("<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"yes\"?>\n");
    let name = if t.name.is_empty() { "Craft" } else { &t.name };
    let _ = write!(s, "<a:theme xmlns:a=\"http://schemas.openxmlformats.org/drawingml/2006/main\" name=\"{}\"><a:themeElements>", esc_attr(name));
    let _ = write!(s, "<a:clrScheme name=\"{}\">", esc_attr(name));
    for (slot, idx) in SLOTS {
        let rgb = t.colors.get(idx).copied().unwrap_or(0) & 0xFFFFFF;
        let _ = write!(s, "<a:{slot}><a:srgbClr val=\"{rgb:06X}\"/></a:{slot}>");
    }
    s.push_str("</a:clrScheme>");
    let _ = write!(
        s,
        "<a:fontScheme name=\"{}\"><a:majorFont><a:latin typeface=\"{}\"/><a:ea typeface=\"\"/><a:cs typeface=\"\"/></a:majorFont><a:minorFont><a:latin typeface=\"{}\"/><a:ea typeface=\"\"/><a:cs typeface=\"\"/></a:minorFont></a:fontScheme>",
        esc_attr(name),
        esc_attr(&t.major_font),
        esc_attr(&t.minor_font)
    );
    // Format scheme: three entries per list, as the schema requires.
    s.push_str("<a:fmtScheme name=\"Craft\"><a:fillStyleLst>");
    for _ in 0..3 {
        s.push_str("<a:solidFill><a:schemeClr val=\"phClr\"/></a:solidFill>");
    }
    s.push_str("</a:fillStyleLst><a:lnStyleLst>");
    for w in [6350, 12700, 19050] {
        let _ = write!(
            s,
            "<a:ln w=\"{w}\" cap=\"flat\" cmpd=\"sng\" algn=\"ctr\"><a:solidFill><a:schemeClr val=\"phClr\"/></a:solidFill><a:prstDash val=\"solid\"/></a:ln>"
        );
    }
    s.push_str("</a:lnStyleLst><a:effectStyleLst>");
    for _ in 0..3 {
        s.push_str("<a:effectStyle><a:effectLst/></a:effectStyle>");
    }
    s.push_str("</a:effectStyleLst><a:bgFillStyleLst>");
    for _ in 0..3 {
        s.push_str("<a:solidFill><a:schemeClr val=\"phClr\"/></a:solidFill>");
    }
    s.push_str("</a:bgFillStyleLst></a:fmtScheme></a:themeElements><a:objectDefaults/><a:extraClrSchemeLst/></a:theme>");
    s
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn roundtrip() {
        let mut t = Theme::default();
        t.colors[0] = 0xFEFEFE;
        t.colors[1] = 0x101010;
        t.colors[9] = 0x123456;
        t.major_font = "Cambria".into();
        t.name = "Mine".into();
        let x = write_theme(&t);
        let back = read_theme(&crate::xml::parse(x.as_bytes()).unwrap());
        assert_eq!(back, t);
    }
}