feat: implement streaming support for tail and line range filters

Co-authored-by: aider (openai/andrew/openrouter/deepseek/deepseek-chat-v3.1) <aider@aider.chat>

src/services/item_service.rs

@@ -646,6 +646,8 @@ struct TailFilter<R: Read + Send> {
     tail_lines: Option<usize>,
     is_eof: bool,
     bytes_read: usize,
+    output_pos: usize,
+    output_len: usize,
 }
 
 impl<R: Read + Send> TailFilter<R> {
@@ -677,27 +679,102 @@ impl<R: Read + Send> TailFilter<R> {
             tail_lines,
             is_eof: false,
             bytes_read: 0,
+            output_pos: 0,
+            output_len: 0,
         })
     }
+    
+    fn process_tail(&mut self) {
+        if self.is_eof {
+            // Process the ring buffer to extract the tail based on parameters
+            if let Some(bytes) = self.tail_bytes {
+                self.output_len = std::cmp::min(bytes, self.bytes_read);
+                self.output_pos = if self.bytes_read > self.ring_buffer.len() {
+                    // We've wrapped around the ring buffer
+                    self.ring_buffer_pos
+                } else {
+                    0
+                };
+            } else if let Some(lines) = self.tail_lines {
+                // Count lines from the end
+                let mut line_count = 0;
+                let mut pos = (self.ring_buffer_pos as isize - 1).rem_euclid(self.ring_buffer.len() as isize) as usize;
+                let mut i = 0;
+                
+                while i < self.bytes_read.min(self.ring_buffer.len()) {
+                    if self.ring_buffer[pos] == b'\n' {
+                        line_count += 1;
+                        if line_count == lines {
+                            break;
+                        }
+                    }
+                    pos = (pos as isize - 1).rem_euclid(self.ring_buffer.len() as isize) as usize;
+                    i += 1;
+                }
+                self.output_len = i + 1;
+                self.output_pos = (pos as isize).rem_euclid(self.ring_buffer.len() as isize) as usize;
+            } else if let Some(words) = self.tail_words {
+                // Count words from the end
+                let mut word_count = 0;
+                let mut pos = (self.ring_buffer_pos as isize - 1).rem_euclid(self.ring_buffer.len() as isize) as usize;
+                let mut i = 0;
+                let mut in_word = false;
+                
+                while i < self.bytes_read.min(self.ring_buffer.len()) {
+                    let byte = self.ring_buffer[pos];
+                    let is_whitespace = byte.is_ascii_whitespace();
+                    
+                    if !in_word && !is_whitespace {
+                        in_word = true;
+                        word_count += 1;
+                        if word_count == words {
+                            break;
+                        }
+                    } else if is_whitespace {
+                        in_word = false;
+                    }
+                    
+                    pos = (pos as isize - 1).rem_euclid(self.ring_buffer.len() as isize) as usize;
+                    i += 1;
+                }
+                self.output_len = i + 1;
+                self.output_pos = (pos as isize).rem_euclid(self.ring_buffer.len() as isize) as usize;
+            } else {
+                self.output_len = self.bytes_read.min(self.ring_buffer.len());
+                self.output_pos = if self.bytes_read > self.ring_buffer.len() {
+                    self.ring_buffer_pos
+                } else {
+                    0
+                };
+            }
+        }
+    }
 }
 
 impl<R: Read + Send> Read for TailFilter<R> {
     fn read(&mut self, buf: &mut [u8]) -> std::io::Result<usize> {
         if self.is_eof {
-            return Ok(0);
+            // We've processed the input and are now outputting the tail
+            if self.output_pos >= self.output_len {
+                return Ok(0);
+            }
+            
+            let bytes_to_copy = std::cmp::min(buf.len(), self.output_len - self.output_pos);
+            for i in 0..bytes_to_copy {
+                let index = (self.output_pos + i) % self.ring_buffer.len();
+                buf[i] = self.ring_buffer[index];
+            }
+            self.output_pos += bytes_to_copy;
+            return Ok(bytes_to_copy);
         }
         
-        // Fill the ring buffer with data from the inner reader
+        // Read data into the ring buffer
         let mut temp_buf = vec![0; 8192];
         let n = self.inner.read(&mut temp_buf)?;
         if n == 0 {
             self.is_eof = true;
-            // Now we can process the ring buffer to extract the tail
+            self.process_tail();
-            // This part needs to be implemented based on the tail parameters
+            return self.read(buf);
-            // For now, just return from the ring buffer
-            let to_copy = std::cmp::min(buf.len(), self.ring_buffer.len());
-            buf[..to_copy].copy_from_slice(&self.ring_buffer[..to_copy]);
-            return Ok(to_copy);
         }
         
         // Add new data to the ring buffer
@@ -707,7 +784,7 @@ impl<R: Read + Send> Read for TailFilter<R> {
             self.bytes_read += 1;
         }
         
-        // We're still reading, so return 0 until EOF
+        // While reading, return 0 bytes
         Ok(0)
     }
 }
@@ -721,6 +798,7 @@ struct LineRangeFilter<R: Read + Send> {
     in_range: bool,
     buffer: Vec<u8>,
     buffer_pos: usize,
+    is_eof: bool,
 }
 
 impl<R: Read + Send> LineRangeFilter<R> {
@@ -731,21 +809,98 @@ impl<R: Read + Send> LineRangeFilter<R> {
     ) -> Self {
         Self {
             inner,
-            line_start,
+            line_start: line_start.or(Some(1)),
             line_end,
             current_line: 1,
             in_range: false,
             buffer: Vec::new(),
             buffer_pos: 0,
+            is_eof: false,
         }
     }
+    
+    fn fill_buffer(&mut self) -> std::io::Result<()> {
+        if self.buffer_pos >= self.buffer.len() && !self.is_eof {
+            // Read more data
+            let mut temp_buf = [0; 8192];
+            let n = self.inner.read(&mut temp_buf)?;
+            if n == 0 {
+                self.is_eof = true;
+                return Ok(());
+            }
+            self.buffer.extend_from_slice(&temp_buf[..n]);
+        }
+        Ok(())
+    }
 }
 
 impl<R: Read + Send> Read for LineRangeFilter<R> {
     fn read(&mut self, buf: &mut [u8]) -> std::io::Result<usize> {
-        // Implementation would process the stream to find the specified line range
+        if self.is_eof && self.buffer_pos >= self.buffer.len() {
-        // This is a complex operation that needs to be implemented carefully
+            return Ok(0);
-        // For now, this is a placeholder
+        }
-        Ok(0)
+        
+        let start_line = self.line_start.unwrap_or(1);
+        let end_line = self.line_end.unwrap_or(usize::MAX);
+        
+        let mut bytes_written = 0;
+        
+        while bytes_written < buf.len() {
+            // Fill the buffer if needed
+            self.fill_buffer()?;
+            
+            if self.buffer_pos >= self.buffer.len() {
+                break;
+            }
+            
+            // Process bytes until we find the start of the range
+            if !self.in_range {
+                while self.buffer_pos < self.buffer.len() && self.current_line < start_line {
+                    if self.buffer[self.buffer_pos] == b'\n' {
+                        self.current_line += 1;
+                        if self.current_line >= start_line {
+                            self.in_range = true;
+                            self.buffer_pos += 1;
+                            break;
+                        }
+                    }
+                    self.buffer_pos += 1;
+                }
+                // If we're still not in range, continue reading
+                if !self.in_range {
+                    continue;
+                }
+            }
+            
+            // Now we're in the range, copy data until we reach the end line or buffer end
+            if self.in_range && self.current_line <= end_line {
+                let bytes_to_copy = std::cmp::min(
+                    buf.len() - bytes_written,
+                    self.buffer.len() - self.buffer_pos
+                );
+                
+                // Check if we encounter a newline that would take us past the end line
+                for i in 0..bytes_to_copy {
+                    let byte = self.buffer[self.buffer_pos + i];
+                    buf[bytes_written + i] = byte;
+                    
+                    if byte == b'\n' {
+                        self.current_line += 1;
+                        if self.current_line > end_line {
+                            // We've reached the end of the range
+                            self.buffer_pos += i + 1;
+                            return Ok(bytes_written + i + 1);
+                        }
+                    }
+                }
+                
+                bytes_written += bytes_to_copy;
+                self.buffer_pos += bytes_to_copy;
+            } else {
+                break;
+            }
+        }
+        
+        Ok(bytes_written)
     }
 }