From d27414937a3f9cebe1df6c9b8454dfbf63cf4cdb Mon Sep 17 00:00:00 2001
From: bluebear94 <uruwi@protonmail.com>
Date: Wed, 1 May 2024 04:07:45 -0400
Subject: [PATCH] Add support for Eastern Arabic numerals (#4036)

---
 crates/typst/src/model/numbering.rs | 41 ++++++++++++++++++++++++++++-
 tests/suite/model/numbering.typ     |  4 +++
 2 files changed, 44 insertions(+), 1 deletion(-)

diff --git a/crates/typst/src/model/numbering.rs b/crates/typst/src/model/numbering.rs
index 10946ccc0..7cfdf98b6 100644
--- a/crates/typst/src/model/numbering.rs
+++ b/crates/typst/src/model/numbering.rs
@@ -3,6 +3,7 @@ use std::str::FromStr;
 use chinese_number::{ChineseCase, ChineseCountMethod, ChineseVariant, NumberToChinese};
 use comemo::Tracked;
 use ecow::{eco_format, EcoString, EcoVec};
+use smallvec::{smallvec, SmallVec};
 
 use crate::diag::SourceResult;
 use crate::engine::Engine;
@@ -243,11 +244,17 @@ cast! {
 /// Different kinds of numberings.
 #[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
 pub enum NumberingKind {
+    /// Arabic numerals (1, 2, 3, etc.).
     Arabic,
+    /// Latin letters (A, B, C, etc.). Items beyond Z use multiple symbols. Uses both cases.
     Letter,
+    /// Roman numerals (I, II, III, etc.). Uses both cases.
     Roman,
+    /// The symbols *, †, ‡, §, ¶, and ‖. Further items use multiple symbols.
     Symbol,
+    /// Hebrew numerals.
     Hebrew,
+    /// Simplified Chinese numerals. Uses standard numerals for lowercase and “banknote” numerals for uppercase.
     SimplifiedChinese,
     // TODO: Pick the numbering pattern based on languages choice.
     // As the `1st` numbering character of Chinese (Simplified) and
@@ -255,13 +262,24 @@ pub enum NumberingKind {
     // if the context is Simplified or Traditional by only this
     // character.
     #[allow(unused)]
+    /// Traditional Chinese numerals. Uses standard numerals for lowercase and “banknote” numerals for uppercase.
     TraditionalChinese,
+    /// Hiragana in the gojūon order. Includes n but excludes wi and we.
     HiraganaAiueo,
+    /// Hiragana in the iroha order. Includes wi and we but excludes n.
     HiraganaIroha,
+    /// Katakana in the gojūon order. Includes n but excludes wi and we.
     KatakanaAiueo,
+    /// Katakana in the iroha order. Includes wi and we but excludes n.
     KatakanaIroha,
+    /// Korean jamo (ㄱ, ㄴ, ㄷ, etc.).
     KoreanJamo,
+    /// Korean syllables (가, 나, 다, etc.).
     KoreanSyllable,
+    /// Eastern Arabic numerals, used in some Arabic-speaking countries.
+    EasternArabic,
+    /// The variant of Eastern Arabic numerals used in Persian and Urdu.
+    EasternArabicPersian,
 }
 
 impl NumberingKind {
@@ -280,6 +298,8 @@ impl NumberingKind {
             'イ' => NumberingKind::KatakanaIroha,
             'ㄱ' => NumberingKind::KoreanJamo,
             '가' => NumberingKind::KoreanSyllable,
+            '\u{0661}' => NumberingKind::EasternArabic,
+            '\u{06F1}' => NumberingKind::EasternArabicPersian,
             _ => return None,
         })
     }
@@ -300,6 +320,8 @@ impl NumberingKind {
             Self::KatakanaIroha => 'イ',
             Self::KoreanJamo => 'ㄱ',
             Self::KoreanSyllable => '가',
+            Self::EasternArabic => '\u{0661}',
+            Self::EasternArabicPersian => '\u{06F1}',
         }
     }
 
@@ -507,6 +529,8 @@ impl NumberingKind {
                 },
                 n,
             ),
+            Self::EasternArabic => decimal('\u{0660}', n),
+            Self::EasternArabicPersian => decimal('\u{06F0}', n),
         }
     }
 }
@@ -542,7 +566,7 @@ fn zeroless<const N_DIGITS: usize>(
     if n == 0 {
         return '-'.into();
     }
-    let mut cs = vec![];
+    let mut cs: SmallVec<[char; 8]> = smallvec![];
     while n > 0 {
         n -= 1;
         cs.push(mk_digit(n % N_DIGITS));
@@ -550,3 +574,18 @@ fn zeroless<const N_DIGITS: usize>(
     }
     cs.into_iter().rev().collect()
 }
+
+/// Stringify a number using a base-10 counting system with a zero digit.
+///
+/// This function assumes that the digits occupy contiguous codepoints.
+fn decimal(start: char, mut n: usize) -> EcoString {
+    if n == 0 {
+        return start.into();
+    }
+    let mut cs: SmallVec<[char; 8]> = smallvec![];
+    while n > 0 {
+        cs.push(char::from_u32((start as u32) + ((n % 10) as u32)).unwrap());
+        n /= 10;
+    }
+    cs.into_iter().rev().collect()
+}
diff --git a/tests/suite/model/numbering.typ b/tests/suite/model/numbering.typ
index c2de1e05e..124173e7c 100644
--- a/tests/suite/model/numbering.typ
+++ b/tests/suite/model/numbering.typ
@@ -98,6 +98,10 @@
   [ for #i \ ]
 }
 
+--- numbering-arabic-indic ---
+#assert.eq(numbering("\u{0661}", 1475), "١٤٧٥")
+#assert.eq(numbering("\u{06F1}", 1475), "۱۴۷۵")
+
 --- numbering-negative ---
 // Error: 17-19 number must be at least zero
 #numbering("1", -1)