perspective-viewer 5.2.0

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// ┃ Copyright (c) 2017, the Perspective Authors.                              ┃
// ┃ ╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌ ┃
// ┃ This file is part of the Perspective library, distributed under the terms ┃
// ┃ of the [Apache License 2.0](https://www.apache.org/licenses/LICENSE-2.0). ┃
// ┗━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┛

//! Minimal HTML entity decoding: numeric references plus the named entities
//! that actually occur in LLM output. An unrecognized entity stays literal
//! text — a cosmetic divergence from CommonMark's 2,000-entry table, never a
//! correctness one (this module exists so we don't link that table).

const NAMED: &[(&str, char)] = &[
    ("amp", '&'),
    ("lt", '<'),
    ("gt", '>'),
    ("quot", '"'),
    ("apos", '\''),
    ("nbsp", '\u{a0}'),
    ("mdash", '—'),
    ("ndash", '–'),
    ("hellip", '…'),
    ("copy", '©'),
    ("reg", '®'),
    ("trade", '™'),
    ("deg", '°'),
    ("times", '×'),
    ("plusmn", '±'),
    ("middot", '·'),
];

/// Try to decode an entity reference at the start of `text` (which begins
/// just AFTER the `&`). Returns the decoded char and the length consumed
/// (excluding the `&`).
pub fn decode(text: &str) -> Option<(char, usize)> {
    let semi = text.find(';').filter(|x| *x <= 10)?;
    let name = &text[..semi];
    let decoded = if let Some(hex) = name.strip_prefix("#x").or_else(|| name.strip_prefix("#X")) {
        char::from_u32(u32::from_str_radix(hex, 16).ok()?)?
    } else if let Some(dec) = name.strip_prefix('#') {
        char::from_u32(dec.parse().ok()?)?
    } else {
        NAMED.iter().find(|(n, _)| *n == name)?.1
    };

    Some((decoded, semi + 1))
}