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use crate::{SgmlEvent, SgmlFragment};
/// A convenience helper to insert and remove events from a [`SgmlFragment`].
#[derive(Clone, Debug, Default)]
pub struct Transform<'a> {
insertions: Vec<(usize, SgmlEvent<'a>)>,
deletions: Vec<usize>,
}
impl<'a> Transform<'a> {
/// Creates a new empty `Transform`.
pub fn new() -> Self {
Default::default()
}
/// Returns `true` if no operations were recorded.
pub fn is_empty(&self) -> bool {
self.insertions.is_empty() && self.deletions.is_empty()
}
/// Removes the event at the given position.
///
/// The position is always relative to the original list --- you should not
/// adjust indices to acommodate other insertions or removals.
///
/// Removing the same `index` multiple times is a no-op, since indices are not readjusted.
///
/// # Example
///
/// ```rust
/// # use sgmlish::{SgmlEvent, SgmlFragment};
/// # use sgmlish::transforms::Transform;
/// let fragment = SgmlFragment::from(vec![
/// /* 0 */ SgmlEvent::OpenStartTag { name: "A".into() },
/// /* 1 */ SgmlEvent::Attribute { name: "HREF".into(), value: Some("/".into()) },
/// /* 2 */ SgmlEvent::CloseStartTag,
/// /* 3 */ SgmlEvent::Character("hello".into()),
/// /* 4 */ SgmlEvent::EndTag { name: "A".into() },
/// /* 5 */ SgmlEvent::Character("!".into()),
/// /* 6 */
/// ]);
///
/// let mut transform = Transform::new();
/// // Remove the attribute
/// transform.remove_at(1);
/// // Remove the final exclamation mark
/// transform.remove_at(5);
/// let result = transform.apply(fragment);
///
/// assert_eq!(
/// result.into_vec(),
/// vec![
/// SgmlEvent::OpenStartTag { name: "A".into() },
/// SgmlEvent::CloseStartTag,
/// SgmlEvent::Character("hello".into()),
/// SgmlEvent::EndTag { name: "A".into() },
/// ]
/// );
/// ```
pub fn remove_at(&mut self, index: usize) {
self.deletions.push(index);
}
/// Inserts an event at the given position.
///
/// The position is always relative to the original list --- you should not
/// adjust indices to acommodate other insertions or removals.
///
/// Inserting multiple events at the same `index` will place them in the order they were passed.
///
/// # Example
///
/// ```rust
/// # use sgmlish::{SgmlEvent, SgmlFragment};
/// # use sgmlish::transforms::Transform;
/// let fragment = SgmlFragment::from(vec![
/// /* 0 */ SgmlEvent::OpenStartTag { name: "A".into() },
/// /* 1 */ SgmlEvent::Attribute { name: "HREF".into(), value: Some("/".into()) },
/// /* 2 */ SgmlEvent::CloseStartTag,
/// /* 3 */ SgmlEvent::Character("hello".into()),
/// /* 4 */
/// ]);
///
/// let mut transform = Transform::new();
/// // Insert another attribute
/// transform.insert_at(2, SgmlEvent::Attribute { name: "TARGET".into(), value: Some("_blank".into()) });
/// // Insert end tag
/// transform.insert_at(4, SgmlEvent::EndTag { name: "A".into() });
/// let result = transform.apply(fragment);
///
/// assert_eq!(
/// result.into_vec(),
/// vec![
/// SgmlEvent::OpenStartTag { name: "A".into() },
/// SgmlEvent::Attribute { name: "HREF".into(), value: Some("/".into()) },
/// SgmlEvent::Attribute { name: "TARGET".into(), value: Some("_blank".into()) },
/// SgmlEvent::CloseStartTag,
/// SgmlEvent::Character("hello".into()),
/// SgmlEvent::EndTag { name: "A".into() },
/// ]
/// );
/// ```
pub fn insert_at(&mut self, index: usize, event: SgmlEvent<'a>) {
self.insertions.push((index, event));
}
/// Applies the recorded changes to the given fragment.
pub fn apply(self, fragment: SgmlFragment<'a>) -> SgmlFragment<'a> {
if self.is_empty() {
return fragment;
}
let mut deletions = self.deletions;
deletions.sort_unstable();
deletions.dedup();
let mut deletions = deletions.into_iter().peekable();
let mut insertions = self.insertions;
insertions.sort_by_key(|(pos, _)| *pos);
let mut insertions = insertions.into_iter().peekable();
let final_size = fragment.len().saturating_sub(deletions.len()) + insertions.len();
let mut result = Vec::with_capacity(final_size);
for (i, event) in fragment.into_iter().enumerate() {
while let Some((_, event_to_insert)) =
insertions.next_if(|(index_to_insert, _)| *index_to_insert == i)
{
result.push(event_to_insert);
}
if deletions.next_if_eq(&i).is_none() {
result.push(event);
}
}
// Insert remaining events at the end
result.extend(insertions.map(|(_, event)| event));
result.into()
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_insert_multiple_times_same_index() {
let fragment = SgmlFragment::from(vec![
SgmlEvent::OpenStartTag { name: "IMG".into() },
SgmlEvent::Attribute {
name: "SRC".into(),
value: Some("example.gif".into()),
},
SgmlEvent::CloseStartTag,
]);
let mut transform = Transform::new();
transform.insert_at(
2,
SgmlEvent::Attribute {
name: "BORDER".into(),
value: Some("0".into()),
},
);
transform.insert_at(
2,
SgmlEvent::Attribute {
name: "ISMAP".into(),
value: None,
},
);
let result = transform.apply(fragment);
assert_eq!(
result,
SgmlFragment::from(vec![
SgmlEvent::OpenStartTag { name: "IMG".into() },
SgmlEvent::Attribute {
name: "SRC".into(),
value: Some("example.gif".into()),
},
SgmlEvent::Attribute {
name: "BORDER".into(),
value: Some("0".into()),
},
SgmlEvent::Attribute {
name: "ISMAP".into(),
value: None,
},
SgmlEvent::CloseStartTag,
])
);
}
#[test]
fn test_remove_multiple_times_same_index() {
let fragment = SgmlFragment::from(vec![
SgmlEvent::OpenStartTag { name: "IMG".into() },
SgmlEvent::Attribute {
name: "SRC".into(),
value: Some("example.gif".into()),
},
SgmlEvent::Attribute {
name: "BORDER".into(),
value: Some("0".into()),
},
SgmlEvent::Attribute {
name: "ISMAP".into(),
value: None,
},
SgmlEvent::CloseStartTag,
]);
let mut transform = Transform::new();
transform.remove_at(2);
transform.remove_at(3);
transform.remove_at(3);
let result = transform.apply(fragment);
assert_eq!(
result,
SgmlFragment::from(vec![
SgmlEvent::OpenStartTag { name: "IMG".into() },
SgmlEvent::Attribute {
name: "SRC".into(),
value: Some("example.gif".into()),
},
SgmlEvent::CloseStartTag,
])
);
}
#[test]
fn test_insert_remove_at_same_index() {
let fragment = SgmlFragment::from(vec![
SgmlEvent::OpenStartTag { name: "A".into() },
SgmlEvent::Attribute {
name: "HREF".into(),
value: Some("/".into()),
},
SgmlEvent::CloseStartTag,
SgmlEvent::Character("hello".into()),
SgmlEvent::EndTag { name: "A".into() },
]);
let mut transform = Transform::new();
transform.insert_at(
1,
SgmlEvent::Attribute {
name: "NAME".into(),
value: Some("greeting".into()),
},
);
transform.remove_at(1);
let result = transform.apply(fragment);
assert_eq!(
result,
SgmlFragment::from(vec![
SgmlEvent::OpenStartTag { name: "A".into() },
SgmlEvent::Attribute {
name: "NAME".into(),
value: Some("greeting".into()),
},
SgmlEvent::CloseStartTag,
SgmlEvent::Character("hello".into()),
SgmlEvent::EndTag { name: "A".into() },
])
);
}
}