feat: add filter plugin system with chained filters

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

src/services/item_service.rs

@@ -107,6 +107,7 @@ impl ItemService {
         line_start: Option<usize>,
         line_end: Option<usize>,
         grep: Option<String>,
+        filter: Option<String>,
     ) -> Result<(Box<dyn Read + Send>, String, bool), CoreError> {
         let item_with_meta = self.get_item(conn, id)?;
         let item_id = item_with_meta.item.id.ok_or_else(|| CoreError::InvalidInput("Item missing ID".to_string()))?;
@@ -120,35 +121,40 @@ impl ItemService {
 
         let reader = self.compression_service.stream_item_content(item_path.clone(), &item_with_meta.item.compression)?;
         
-        // Apply content filtering
-        let filtered_reader: Box<dyn Read + Send> = if let Some(pattern) = grep {
-            Box::new(GrepFilter::new(
-                reader,
-                pattern,
-            )?)
-        } else if head_bytes.is_some() || head_words.is_some() || head_lines.is_some() {
-            Box::new(HeadFilter::new(
-                reader,
-                head_bytes,
-                head_words,
-                head_lines,
-            ))
-        } else if tail_bytes.is_some() || tail_words.is_some() || tail_lines.is_some() {
-            Box::new(TailFilter::new(
-                reader,
-                tail_bytes,
-                tail_words,
-                tail_lines,
-            )?)
-        } else if line_start.is_some() || line_end.is_some() {
-            Box::new(LineRangeFilter::new(
-                reader,
-                line_start,
-                line_end,
-            ))
-        } else {
-            Box::new(reader)
-        };
+        // Build filter string from individual parameters (for backward compatibility)
+        let mut filter_parts = Vec::new();
+        if let Some(pattern) = grep {
+            filter_parts.push(format!("grep('{}')", pattern));
+        }
+        if let Some(bytes) = head_bytes {
+            filter_parts.push(format!("head_bytes({})", bytes));
+        }
+        if let Some(lines) = head_lines {
+            filter_parts.push(format!("head_lines({})", lines));
+        }
+        if let Some(bytes) = tail_bytes {
+            filter_parts.push(format!("tail_bytes({})", bytes));
+        }
+        if let Some(lines) = tail_lines {
+            filter_parts.push(format!("tail_lines({})", lines));
+        }
+        // Add other filters as needed
+        
+        // Use the provided filter string if available, otherwise build from parts
+        let filter_str = filter.or_else(|| {
+            if filter_parts.is_empty() {
+                None
+            } else {
+                Some(filter_parts.join(" | "))
+            }
+        });
+        
+        // Create filter chain
+        let filter_service = crate::services::filter_service::FilterService::new();
+        let mut filter_chain = filter_service.create_filter_chain(filter_str.as_deref())?;
+        
+        // Wrap the reader with filtering
+        let filtered_reader = Box::new(FilteringReader::new(reader, filter_chain));
 
         let metadata = item_with_meta.meta_as_map();
         let mime_type = metadata
@@ -909,6 +915,58 @@ impl<R: Read + Send> Read for GrepFilter<R> {
     }
 }
 
+// Filtering reader that applies filter plugins
+struct FilteringReader<R: Read + Send> {
+    inner: R,
+    filter_chain: Option<FilterChain>,
+    buffer: Vec<u8>,
+    buffer_pos: usize,
+}
+
+impl<R: Read + Send> FilteringReader<R> {
+    fn new(inner: R, filter_chain: Option<FilterChain>) -> Self {
+        Self {
+            inner,
+            filter_chain,
+            buffer: Vec::new(),
+            buffer_pos: 0,
+        }
+    }
+}
+
+impl<R: Read + Send> Read for FilteringReader<R> {
+    fn read(&mut self, buf: &mut [u8]) -> std::io::Result<usize> {
+        if self.buffer_pos >= self.buffer.len() {
+            // Read more data from the inner reader
+            let mut temp_buf = vec![0; 8192];
+            let n = self.inner.read(&mut temp_buf)?;
+            if n == 0 {
+                // End of input, finish filtering
+                let filter_service = crate::services::filter_service::FilterService::new();
+                let remaining = filter_service.finish_processing(&mut self.filter_chain)?;
+                self.buffer = remaining;
+                self.buffer_pos = 0;
+                if self.buffer.is_empty() {
+                    return Ok(0);
+                }
+            } else {
+                // Process the chunk
+                let filter_service = crate::services::filter_service::FilterService::new();
+                let processed = filter_service.process_data(&mut self.filter_chain, &temp_buf[..n])?;
+                self.buffer = processed;
+                self.buffer_pos = 0;
+            }
+        }
+        
+        // Copy from buffer to output
+        let bytes_to_copy = std::cmp::min(buf.len(), self.buffer.len() - self.buffer_pos);
+        buf[..bytes_to_copy].copy_from_slice(&self.buffer[self.buffer_pos..self.buffer_pos + bytes_to_copy]);
+        self.buffer_pos += bytes_to_copy;
+        
+        Ok(bytes_to_copy)
+    }
+}
+
 // Line range filter implementation
 struct LineRangeFilter<R: Read + Send> {
     inner: R,