use smallvec::SmallVec; use crate::{Edit, PartialEdit}; /// Events emitted by `ToolEditParser` as tool call input streams in.#[derive(Debug, PartialEq, Eq)]pub enum ToolEditEvent {    /// A chunk of `old_text` for an edit operation.    OldTextChunk {        edit_index: usize,        chunk: String,        done: bool,    },    /// A chunk of `new_text` for an edit operation.    NewTextChunk {        edit_index: usize,        chunk: String,        done: bool,    },    /// A chunk of content for write/overwrite mode.    ContentChunk { chunk: String },} /// Tracks the streaming state of a single edit to detect deltas.#[derive(Default, Debug)]struct EditStreamState {    old_text_emitted_len: usize,    old_text_done: bool,    new_text_emitted_len: usize,    new_text_done: bool,} /// Converts incrementally-growing tool call JSON into a stream of chunk events.////// The tool call streaming infrastructure delivers partial JSON objects where/// string fields grow over time. This parser compares consecutive partials,/// computes the deltas, and emits `ToolEditEvent`s that downstream pipeline/// stages (`StreamingFuzzyMatcher` for old_text, `StreamingDiff` for new_text)/// can consume incrementally.////// Because partial JSON comes through a fixer (`partial-json-fixer`) that/// closes incomplete escape sequences, a string can temporarily contain wrong/// trailing characters (e.g. a literal `\` instead of `\n`).  We handle this/// by holding back trailing backslash characters in non-finalized chunks: if/// a partial string ends with `\` (0x5C), that byte is not emitted until the/// next partial confirms or corrects it.  This avoids feeding corrupted bytes/// to downstream consumers.#[derive(Default, Debug)]pub struct ToolEditParser {    edit_states: Vec<EditStreamState>,    content_emitted_len: usize,} impl ToolEditParser {    /// Push a new set of partial edits (from edit mode) and return any events.    ///    /// Each call should pass the *entire current* edits array as seen in the    /// latest partial input. The parser will diff it against its internal state    /// to produce only the new events.    pub fn push_edits(&mut self, edits: &[PartialEdit]) -> SmallVec<[ToolEditEvent; 4]> {        let mut events = SmallVec::new();         for (index, partial) in edits.iter().enumerate() {            if index >= self.edit_states.len() {                // A new edit appeared — finalize the previous one if there was one.                if let Some(previous) = self.finalize_previous_edit(index) {                    events.extend(previous);                }                self.edit_states.push(EditStreamState::default());            }             let state = &mut self.edit_states[index];             // Process old_text changes.            if let Some(old_text) = &partial.old_text                && !state.old_text_done            {                if partial.new_text.is_some() {                    // new_text appeared, so old_text is done — emit everything.                    let start = state.old_text_emitted_len.min(old_text.len());                    let chunk = old_text[start..].to_string();                    state.old_text_done = true;                    state.old_text_emitted_len = old_text.len();                    events.push(ToolEditEvent::OldTextChunk {                        edit_index: index,                        chunk,                        done: true,                    });                } else {                    let safe_end = safe_emit_end(old_text);                    if safe_end > state.old_text_emitted_len {                        let chunk = old_text[state.old_text_emitted_len..safe_end].to_string();                        state.old_text_emitted_len = safe_end;                        events.push(ToolEditEvent::OldTextChunk {                            edit_index: index,                            chunk,                            done: false,                        });                    }                }            }             // Process new_text changes.            if let Some(new_text) = &partial.new_text                && !state.new_text_done            {                let safe_end = safe_emit_end(new_text);                if safe_end > state.new_text_emitted_len {                    let chunk = new_text[state.new_text_emitted_len..safe_end].to_string();                    state.new_text_emitted_len = safe_end;                    events.push(ToolEditEvent::NewTextChunk {                        edit_index: index,                        chunk,                        done: false,                    });                }            }        }         events    }     /// Push new content and return any events.    ///    /// Each call should pass the *entire current* content string. The parser    /// will diff it against its internal state to emit only the new chunk.    pub fn push_content(&mut self, content: &str) -> SmallVec<[ToolEditEvent; 1]> {        let mut events = SmallVec::new();         let safe_end = safe_emit_end(content);        if safe_end > self.content_emitted_len {            let chunk = content[self.content_emitted_len..safe_end].to_string();            self.content_emitted_len = safe_end;            events.push(ToolEditEvent::ContentChunk { chunk });        }         events    }     /// Finalize all edits with the complete input. This emits `done: true`    /// events for any in-progress old_text or new_text that hasn't been    /// finalized yet.    ///    /// `final_edits` should be the fully deserialized final edits array. The    /// parser compares against its tracked state and emits any remaining deltas    /// with `done: true`.    pub fn finalize_edits(&mut self, edits: &[Edit]) -> SmallVec<[ToolEditEvent; 4]> {        let mut events = SmallVec::new();         for (index, edit) in edits.iter().enumerate() {            if index >= self.edit_states.len() {                // This edit was never seen in partials — emit it fully.                if let Some(previous) = self.finalize_previous_edit(index) {                    events.extend(previous);                }                self.edit_states.push(EditStreamState::default());            }             let state = &mut self.edit_states[index];             if !state.old_text_done {                let start = state.old_text_emitted_len.min(edit.old_text.len());                let chunk = edit.old_text[start..].to_string();                state.old_text_done = true;                state.old_text_emitted_len = edit.old_text.len();                events.push(ToolEditEvent::OldTextChunk {                    edit_index: index,                    chunk,                    done: true,                });            }             if !state.new_text_done {                let start = state.new_text_emitted_len.min(edit.new_text.len());                let chunk = edit.new_text[start..].to_string();                state.new_text_done = true;                state.new_text_emitted_len = edit.new_text.len();                events.push(ToolEditEvent::NewTextChunk {                    edit_index: index,                    chunk,                    done: true,                });            }        }         events    }     /// Finalize content with the complete input.    pub fn finalize_content(&mut self, content: &str) -> SmallVec<[ToolEditEvent; 1]> {        let mut events = SmallVec::new();         let start = self.content_emitted_len.min(content.len());        if content.len() > start {            let chunk = content[start..].to_string();            self.content_emitted_len = content.len();            events.push(ToolEditEvent::ContentChunk { chunk });        }         events    }     /// When a new edit appears at `index`, finalize the edit at `index - 1`    /// by emitting a `NewTextChunk { done: true }` if it hasn't been finalized.    fn finalize_previous_edit(&mut self, new_index: usize) -> Option<SmallVec<[ToolEditEvent; 2]>> {        if new_index == 0 || self.edit_states.is_empty() {            return None;        }         let previous_index = new_index - 1;        if previous_index >= self.edit_states.len() {            return None;        }         let state = &mut self.edit_states[previous_index];        let mut events = SmallVec::new();         // If old_text was never finalized, finalize it now with an empty done chunk.        if !state.old_text_done {            state.old_text_done = true;            events.push(ToolEditEvent::OldTextChunk {                edit_index: previous_index,                chunk: String::new(),                done: true,            });        }         // Emit a done event for new_text if not already finalized.        if !state.new_text_done {            state.new_text_done = true;            events.push(ToolEditEvent::NewTextChunk {                edit_index: previous_index,                chunk: String::new(),                done: true,            });        }         Some(events)    }} /// Returns the byte position up to which it is safe to emit from a partial/// string.  If the string ends with a backslash (`\`, 0x5C), that byte is/// held back because it may be an artifact of the partial JSON fixer closing/// an incomplete escape sequence (e.g. turning a half-received `\n` into `\\`)./// The next partial will reveal the correct character.fn safe_emit_end(text: &str) -> usize {    if text.as_bytes().last() == Some(&b'\\') {        text.len() - 1    } else {        text.len()    }} #[cfg(test)]mod tests {    use super::*;     #[test]    fn test_single_edit_streamed_incrementally() {        let mut parser = ToolEditParser::default();         // old_text arrives in chunks: "hell" → "hello w" → "hello world"        let events = parser.push_edits(&[PartialEdit {            old_text: Some("hell".into()),            new_text: None,        }]);        assert_eq!(            events.as_slice(),            &[ToolEditEvent::OldTextChunk {                edit_index: 0,                chunk: "hell".into(),                done: false,            }]        );         let events = parser.push_edits(&[PartialEdit {            old_text: Some("hello w".into()),            new_text: None,        }]);        assert_eq!(            events.as_slice(),            &[ToolEditEvent::OldTextChunk {                edit_index: 0,                chunk: "o w".into(),                done: false,            }]        );         // new_text appears → old_text finalizes        let events = parser.push_edits(&[PartialEdit {            old_text: Some("hello world".into()),            new_text: Some("good".into()),        }]);        assert_eq!(            events.as_slice(),            &[                ToolEditEvent::OldTextChunk {                    edit_index: 0,                    chunk: "orld".into(),                    done: true,                },                ToolEditEvent::NewTextChunk {                    edit_index: 0,                    chunk: "good".into(),                    done: false,                },            ]        );         // new_text grows        let events = parser.push_edits(&[PartialEdit {            old_text: Some("hello world".into()),            new_text: Some("goodbye world".into()),        }]);        assert_eq!(            events.as_slice(),            &[ToolEditEvent::NewTextChunk {                edit_index: 0,                chunk: "bye world".into(),                done: false,            }]        );         // Finalize        let events = parser.finalize_edits(&[Edit {            old_text: "hello world".into(),            new_text: "goodbye world".into(),        }]);        assert_eq!(            events.as_slice(),            &[ToolEditEvent::NewTextChunk {                edit_index: 0,                chunk: "".into(),                done: true,            }]        );    }     #[test]    fn test_multiple_edits_sequential() {        let mut parser = ToolEditParser::default();         // First edit streams in        let events = parser.push_edits(&[PartialEdit {            old_text: Some("first old".into()),            new_text: None,        }]);        assert_eq!(            events.as_slice(),            &[ToolEditEvent::OldTextChunk {                edit_index: 0,                chunk: "first old".into(),                done: false,            }]        );         let events = parser.push_edits(&[PartialEdit {            old_text: Some("first old".into()),            new_text: Some("first new".into()),        }]);        assert_eq!(            events.as_slice(),            &[                ToolEditEvent::OldTextChunk {                    edit_index: 0,                    chunk: "".into(),                    done: true,                },                ToolEditEvent::NewTextChunk {                    edit_index: 0,                    chunk: "first new".into(),                    done: false,                },            ]        );         // Second edit appears → first edit's new_text is finalized        let events = parser.push_edits(&[            PartialEdit {                old_text: Some("first old".into()),                new_text: Some("first new".into()),            },            PartialEdit {                old_text: Some("second".into()),                new_text: None,            },        ]);        assert_eq!(            events.as_slice(),            &[                ToolEditEvent::NewTextChunk {                    edit_index: 0,                    chunk: "".into(),                    done: true,                },                ToolEditEvent::OldTextChunk {                    edit_index: 1,                    chunk: "second".into(),                    done: false,                },            ]        );         // Finalize everything        let events = parser.finalize_edits(&[            Edit {                old_text: "first old".into(),                new_text: "first new".into(),            },            Edit {                old_text: "second old".into(),                new_text: "second new".into(),            },        ]);        assert_eq!(            events.as_slice(),            &[                ToolEditEvent::OldTextChunk {                    edit_index: 1,                    chunk: " old".into(),                    done: true,                },                ToolEditEvent::NewTextChunk {                    edit_index: 1,                    chunk: "second new".into(),                    done: true,                },            ]        );    }     #[test]    fn test_content_streamed_incrementally() {        let mut parser = ToolEditParser::default();         let events = parser.push_content("hello");        assert_eq!(            events.as_slice(),            &[ToolEditEvent::ContentChunk {                chunk: "hello".into(),            }]        );         let events = parser.push_content("hello world");        assert_eq!(            events.as_slice(),            &[ToolEditEvent::ContentChunk {                chunk: " world".into(),            }]        );         // No change        let events = parser.push_content("hello world");        assert!(events.is_empty());         let events = parser.push_content("hello world!");        assert_eq!(            events.as_slice(),            &[ToolEditEvent::ContentChunk { chunk: "!".into() }]        );         // Finalize with no additional content        let events = parser.finalize_content("hello world!");        assert!(events.is_empty());    }     #[test]    fn test_finalize_content_with_remaining() {        let mut parser = ToolEditParser::default();         parser.push_content("partial");        let events = parser.finalize_content("partial content here");        assert_eq!(            events.as_slice(),            &[ToolEditEvent::ContentChunk {                chunk: " content here".into(),            }]        );    }     #[test]    fn test_content_trailing_backslash_held_back() {        let mut parser = ToolEditParser::default();         // Partial JSON fixer turns incomplete \n into \\ (literal backslash).        // The trailing backslash is held back.        let events = parser.push_content("hello,\\");        assert_eq!(            events.as_slice(),            &[ToolEditEvent::ContentChunk {                chunk: "hello,".into(),            }]        );         // Next partial corrects the escape to an actual newline.        // The held-back byte was wrong; the correct newline is emitted.        let events = parser.push_content("hello,\n");        assert_eq!(            events.as_slice(),

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