Right-to-left text

use bidi.qweruse bidi_direction, bidi_visual from bidi      // Quillo 0.6: only these

unicode-bidi = "=0.3.18"serde_json = { version = "1", features = ["preserve_order"] }

// A marketplace with sellers writing in Arabic and Hebrew: the page direction of each listing, names isolated in English sentences, receipts for a printer with no bidi, and usernames checked for hidden direction tricks.////   quillo run bidi.qwe      then open http://localhost:8080/bidiuse "bidi.qwer"route GET /bidi {    {        arabic: bidi_direction("مرحبا بالعالم"),        english: bidi_direction("Hello, world").direction,        mixed: bidi_direction("שלום world"),        digits: bidi_direction("123-456").direction,        // "Order 15 for עלמה": in memory the Hebrew letters come first to last; a printer must get them reversed.        receipt: bidi_visual("Order 15 for עלמה", "ltr")?,        hebrew_line: bidi_visual("abc שלום", "rtl")?,        isolated: replace(replace(bidi_isolate("עלמה"), "\u{2068}", "[FSI]"), "\u{2069}", "[PDI]"),        // A file name that shows as "invoice‮fdp.exe" reads "invoiceexe.pdf" on screen.        trick: bidi_check("invoice\u{202E}fdp.exe"),        cleaned: bidi_strip("invoice\u{202E}fdp.exe"),        plain: bidi_check("Plain name").safe,    }}route GET /listing ? { title: str = "שולחן עץ" } {    let dir = bidi_direction(title).direction    <html><body>        <h1 dir={dir == "rtl" ? "rtl" : "ltr"}>{title}</h1>        <p>Sold by <bdi>{title}</bdi> in 3 days.</p>    </body></html>}

//! Right-to-left text done right: a text's direction (Arabic, Hebrew, Persian, Urdu...), mixed text put in display order for places with no bidi support (receipt printers, terminals, images, PDFs), user text isolated so it cannot flip a page's layout, and the invisible direction controls of "Trojan Source" attacks found and removed.//! version: 1.0.0//!//! [dependencies]//! unicode-bidi = "=0.3.18"//! serde_json = { version = "1", features = ["preserve_order"] }use serde_json::{json, Value};use unicode_bidi::{bidi_class, BidiClass, BidiInfo, Level};const CONTROLS: [(char, &str); 12] = [    ('\u{202A}', "LEFT-TO-RIGHT EMBEDDING"), ('\u{202B}', "RIGHT-TO-LEFT EMBEDDING"), ('\u{202C}', "POP DIRECTIONAL FORMATTING"),    ('\u{202D}', "LEFT-TO-RIGHT OVERRIDE"), ('\u{202E}', "RIGHT-TO-LEFT OVERRIDE"), ('\u{2066}', "LEFT-TO-RIGHT ISOLATE"),    ('\u{2067}', "RIGHT-TO-LEFT ISOLATE"), ('\u{2068}', "FIRST STRONG ISOLATE"), ('\u{2069}', "POP DIRECTIONAL ISOLATE"),    ('\u{200E}', "LEFT-TO-RIGHT MARK"), ('\u{200F}', "RIGHT-TO-LEFT MARK"), ('\u{061C}', "ARABIC LETTER MARK"),];fn is_rtl_class(c: BidiClass) -> bool { matches!(c, BidiClass::R | BidiClass::AL) }/// The direction of `text`: `"rtl"` or `"ltr"` by its first strong letter (as `dir="auto"` decides), `"neutral"` when it has none (digits and punctuation only); `{ direction, has_rtl, has_ltr, mixed }`.pub fn bidi_direction(text: &str) -> Value {    let mut first = None;    let (mut r, mut l) = (false, false);    for c in text.chars() {        let cls = bidi_class(c);        if is_rtl_class(cls) { r = true; if first.is_none() { first = Some("rtl") } }        else if cls == BidiClass::L { l = true; if first.is_none() { first = Some("ltr") } }    }    json!({ "direction": first.unwrap_or("neutral"), "has_rtl": r, "has_ltr": l, "mixed": r && l })}/// `text` in display order, line by line (the Unicode Bidirectional Algorithm), for output that shows characters left to right as stored: thermal printers, terminals, text drawn on images./// `base` is `"auto"` (each paragraph by its first strong letter), `"ltr"` or `"rtl"`.pub fn bidi_visual(text: &str, base: &str) -> Result<String, String> {    let level = match base.trim().to_lowercase().as_str() { "" | "auto" => None, "ltr" => Some(Level::ltr()), "rtl" => Some(Level::rtl()), b => return Err(format!("base is auto, ltr or rtl, not `{}`", b)) };    let mut out = Vec::new();    for line in text.split('\n') {        let info = BidiInfo::new(line, level);        let mut s = String::new();        for para in &info.paragraphs { s.push_str(&info.reorder_line(para, para.range.clone())) }        out.push(s);    }    Ok(out.join("\n"))}/// `text` wrapped in a first-strong isolate (U+2068 … U+2069) with any controls inside removed: a user's name or a product title in Arabic or Hebrew put into a sentence without turning the words around it. (In HTML, `<bdi>` does the same.)pub fn bidi_isolate(text: &str) -> String {    format!("\u{2068}{}\u{2069}", bidi_strip(text))}/// `text` without the invisible direction controls (embeddings, overrides, isolates and marks): for usernames, file names and code, where they only disguise.pub fn bidi_strip(text: &str) -> String {    text.chars().filter(|c| !CONTROLS.iter().any(|(x, _)| x == c)).collect()}/// The direction controls in `text`, "Trojan Source" style: `{ safe, controls: [{ position, code, name }], unbalanced }`; `unbalanced` when an embedding, override or isolate is never closed, which lets it flip what follows. `safe` when there are no overrides, embeddings or isolates (lone marks are allowed).pub fn bidi_check(text: &str) -> Value {    let mut found = Vec::new();    let (mut emb, mut iso) = (0i64, 0i64);    let mut dangerous = false;    for (i, c) in text.chars().enumerate() {        if let Some((_, name)) = CONTROLS.iter().find(|(x, _)| *x == c) {            found.push(json!({ "position": i, "code": format!("U+{:04X}", c as u32), "name": name }));            match c {                '\u{202A}'..='\u{202B}' | '\u{202D}'..='\u{202E}' => { emb += 1; dangerous = true }                '\u{202C}' => emb -= 1,                '\u{2066}'..='\u{2068}' => { iso += 1; dangerous = true }                '\u{2069}' => iso -= 1,                _ => {}            }        }        if c == '\n' { if emb != 0 || iso != 0 { dangerous = true } }    }    json!({ "safe": !dangerous, "controls": found, "unbalanced": emb != 0 || iso != 0 })}