1 files changed, 100 insertions, 0 deletions
diff --git a/src/telegram.rs b/src/telegram.rs
new file mode 100644
index 0000000..ac6eeb3
--- /dev/null
+++ b/src/telegram.rs
@@ -0,0 +1,100 @@
+use std::cmp::Ordering;
+
+use pyo3::prelude::*;
+
+use crate::parser::parse_with_limits;
+
+const TELEGRAM_STYLES: &[(&'static str, &'static str)] = &[
+    ("_", "italics"),
+    ("*", "bold"),
+    ("~", "strikethrough"),
+    ("||", "spoiler"),
+    ("`", "code"),
+    ("```", "pre")
+];
+
+#[pyfunction]
+pub fn parse_for_telegram(body: String) -> PyResult<(String, Vec<(String, usize, usize, String)>)> {
+    let mut chars: Vec<char> = body.chars().collect();
+    if chars.len() < 1 {
+        return Ok((body, Vec::with_capacity(0)));
+    }
+
+    let styles: Vec<(String, usize, usize, usize, usize)> = parse_with_limits(&chars, 0, chars.len() - 1, 0);
+    let mut remove_tags: Vec<(usize, usize)> = Vec::with_capacity(styles.len() * 2);
+    for (keyword, start, remove_start, end, remove_end) in &styles {
+        if TELEGRAM_STYLES.iter().any(|&(k, _)| k == keyword) {
+            remove_tags.push((*start, *remove_start));
+            remove_tags.push((*end, *remove_end));
+        } else if keyword == "```>" {
+            remove_tags.push((*start, *remove_start));
+        }
+    }
+
+    remove_tags.sort_by(|a, b| b.0.cmp(&a.0));
+
+    for (index, end) in remove_tags {
+        chars = [chars[..index].to_vec(), chars[end..].to_vec()].concat();
+    }
+
+    let mut message_entities: Vec<(bool, usize, String, usize, String)> = Vec::with_capacity(styles.len() * 2);
+    let mut all_indexes: Vec<Vec<usize>> = Vec::with_capacity(styles.len());
+    for (keyword, start, remove_start, end, remove_end) in &styles {
+        if TELEGRAM_STYLES.iter().any(|&(k, _)| k == keyword) {
+            let language = if keyword == "```language" {
+                chars[start+3..remove_start-1]
+                .into_iter()
+                .collect::<String>()
+            } else {
+                "".to_string()
+            };
+            all_indexes.push(vec![*start, *remove_start, *end, *remove_end]);
+            let last_index = all_indexes.len() - 1;
+            message_entities.push((true, last_index, TELEGRAM_STYLES.iter().find(|&&(k, _)| k == keyword).unwrap().1.to_string(), *start, language));
+            message_entities.push((false, last_index, "".to_string(), *end, "".to_string()));
+        } else if keyword == "```>" {
+            all_indexes.push(vec![0, 0, *start, 1]);
+            message_entities.push((false, all_indexes.len() - 1, "".to_string(), *start, "".to_string()));
+        }
+    }
+    message_entities.sort_by(sort_message_entities);
+
+    let formatted_text = chars.into_iter().collect::<String>();
+    let utf16_lengths: Vec<usize> = utf8_to_utf16_length(&formatted_text);
+
+    let mut offset = 0;
+    for (is_start, index, _, _, _) in &message_entities {
+        let indexes = &mut all_indexes[*index];
+        if *is_start {
+            indexes[0] -= offset;
+            offset += indexes[1];
+        } else {
+            indexes[2] -= offset;
+            offset += indexes[3];
+        }
+    }
+    Ok((
+        formatted_text,
+        message_entities.into_iter()
+            .filter(|(is_start, _, _, _, _)| { *is_start } )
+            .map(|(_, index, format, _, language)| { (format, utf16_lengths[all_indexes[index][0]], utf16_lengths[all_indexes[index][2]], language) })
+            .collect()
+    ))
+}
+
+fn sort_message_entities(first: &(bool, usize, String, usize, String), second: &(bool, usize, String, usize, String)) -> Ordering {
+    return first.3.cmp(&second.3);
+}
+
+fn utf8_to_utf16_length(utf8_str: &str) -> Vec<usize> {
+    let mut utf16_lengths = Vec::with_capacity(utf8_str.len());
+
+    let mut length = 0;
+    for byte in utf8_str.as_bytes() {
+        if (byte & 0xc0) != 0x80 {
+            length += if *byte >= 0xf0 { 2 } else { 1 };
+        }
+        utf16_lengths.push(length);
+    }
+    utf16_lengths
+}