Add a plugin API for reading HTTP response bodies (#560)

crates/common/yaak-rpc-schema/bindings/gen_models.ts

@@ -55,7 +55,7 @@ urlParameters: Array<HttpUrlParameter>, settingSendCookies: InheritedBoolSetting
 
 export type HttpRequestHeader = { enabled?: boolean, name: string, value: string, id?: string, };
 
-export type HttpResponse = { model: "http_response", id: string, createdAt: string, updatedAt: string, workspaceId: string, requestId: string, bodyPath: string | null, contentLength: number | null, contentLengthCompressed: number | null, elapsed: number, elapsedHeaders: number, elapsedDns: number, error: string | null, headers: Array<HttpResponseHeader>, remoteAddr: string | null, requestContentLength: number | null, requestHeaders: Array<HttpResponseHeader>, status: number, statusReason: string | null, state: HttpResponseState, url: string, version: string | null, };
+export type HttpResponse = { model: "http_response", id: string, createdAt: string, updatedAt: string, workspaceId: string, requestId: string, contentLength: number | null, contentLengthCompressed: number | null, elapsed: number, elapsedHeaders: number, elapsedDns: number, error: string | null, headers: Array<HttpResponseHeader>, remoteAddr: string | null, requestContentLength: number | null, requestHeaders: Array<HttpResponseHeader>, status: number, statusReason: string | null, state: HttpResponseState, url: string, version: string | null, };
 
 export type HttpResponseEvent = { model: "http_response_event", id: string, createdAt: string, updatedAt: string, workspaceId: string, responseId: string, event: HttpResponseEventData, };
 

crates/yaak-models/bindings/gen_models.ts

@@ -225,7 +225,6 @@ export type HttpResponse = {
   updatedAt: string;
   workspaceId: string;
   requestId: string;
-  bodyPath: string | null;
   contentLength: number | null;
   contentLengthCompressed: number | null;
   elapsed: number;

crates/yaak-models/src/models.rs

@@ -1677,6 +1677,13 @@ pub struct HttpResponse {
     pub workspace_id: String,
     pub request_id: String,
 
+    /// Where the engine put the body, when it puts it in a file.
+    ///
+    /// Not exported to TypeScript: a path is only meaningful to a host that
+    /// has the filesystem it names, and bodies are moving off it. Read a body
+    /// by response id instead — the frontend through
+    /// `cmd_http_response_body_path`, plugins through `ctx.httpResponse.body`.
+    #[ts(skip)]
     pub body_path: Option<String>,
     pub content_length: Option<i32>,
     pub content_length_compressed: Option<i32>,

crates/yaak-plugins/bindings/gen_models.ts

@@ -224,7 +224,6 @@ export type HttpResponse = {
   updatedAt: string;
   workspaceId: string;
   requestId: string;
-  bodyPath: string | null;
   contentLength: number | null;
   contentLengthCompressed: number | null;
   elapsed: number;

crates/yaak-plugins/src/events.rs

@@ -171,6 +171,12 @@ pub enum InternalEventPayload {
 
     FindHttpResponsesRequest(FindHttpResponsesRequest),
     FindHttpResponsesResponse(FindHttpResponsesResponse),
+
+    GetHttpResponseBodyInfoRequest(GetHttpResponseBodyInfoRequest),
+    GetHttpResponseBodyInfoResponse(GetHttpResponseBodyInfoResponse),
+    ReadHttpResponseBodyChunkRequest(ReadHttpResponseBodyChunkRequest),
+    ReadHttpResponseBodyChunkResponse(ReadHttpResponseBodyChunkResponse),
+
     ListHttpRequestsRequest(ListHttpRequestsRequest),
     ListHttpRequestsResponse(ListHttpRequestsResponse),
     ListFoldersRequest(ListFoldersRequest),
@@ -288,6 +294,15 @@ pub struct SendHttpRequestRequest {
 #[ts(export, export_to = "gen_events.ts")]
 pub struct SendHttpRequestResponse {
     pub http_response: HttpResponse,
+
+    /// The body, base64, when the send saved nothing.
+    ///
+    /// A request with no id behind it produces a response the model store never
+    /// sees, so it cannot be read back by id later the way a saved one can.
+    /// This is the only copy of it. `None` means the body was stored and should
+    /// be read with `read_http_response_body_chunk_request`.
+    #[ts(optional = nullable)]
+    pub body: Option<String>,
 }
 
 #[derive(Debug, Clone, Default, Serialize, Deserialize, TS)]
@@ -1413,6 +1428,67 @@ pub struct FindHttpResponsesResponse {
     pub http_responses: Vec<HttpResponse>,
 }
 
+/// Ask what a response's body is, before deciding whether to pull it.
+///
+/// Bodies are addressed by response id and never by path, so where the host
+/// keeps the bytes is its own business.
+#[derive(Debug, Clone, Default, Serialize, Deserialize, TS)]
+#[serde(default, rename_all = "camelCase")]
+#[ts(export, export_to = "gen_events.ts")]
+pub struct GetHttpResponseBodyInfoRequest {
+    pub response_id: String,
+}
+
+#[derive(Debug, Clone, Default, Serialize, Deserialize, TS)]
+#[serde(default, rename_all = "camelCase")]
+#[ts(export, export_to = "gen_events.ts")]
+pub struct GetHttpResponseBodyInfoResponse {
+    /// How many bytes are stored right now, which is not necessarily what the
+    /// `Content-Length` header claimed. Zero when the response has no body.
+    #[ts(type = "number")]
+    pub content_length: u64,
+
+    /// Whether the response has finished arriving. While it has not, the body
+    /// keeps growing past `content_length`, and a reader that wants all of it
+    /// asks again.
+    pub complete: bool,
+
+    /// The response's `Content-Type` header, verbatim, so the reader can pick a
+    /// charset.
+    #[ts(optional = nullable)]
+    pub content_type: Option<String>,
+}
+
+/// Pull one window of a response body.
+///
+/// Reads are idempotent: the bytes live in durable storage, so the same window
+/// can be asked for as many times as the plugin likes.
+#[derive(Debug, Clone, Default, Serialize, Deserialize, TS)]
+#[serde(default, rename_all = "camelCase")]
+#[ts(export, export_to = "gen_events.ts")]
+pub struct ReadHttpResponseBodyChunkRequest {
+    pub response_id: String,
+    #[ts(type = "number")]
+    pub offset: u64,
+    #[ts(type = "number")]
+    pub length: u64,
+}
+
+#[derive(Debug, Clone, Default, Serialize, Deserialize, TS)]
+#[serde(default, rename_all = "camelCase")]
+#[ts(export, export_to = "gen_events.ts")]
+pub struct ReadHttpResponseBodyChunkResponse {
+    /// Base64, because the desktop transport is a WebSocket that only sends
+    /// text frames today. A host that can carry binary sends the bytes as they
+    /// are and fills this in from them.
+    pub data: String,
+
+    /// Bytes decoded from `data`. Short of the requested length means the body
+    /// ended here.
+    #[ts(type = "number")]
+    pub length: u64,
+}
+
 #[derive(Debug, Clone, Default, Serialize, Deserialize, TS)]
 #[serde(default, rename_all = "camelCase")]
 #[ts(export, export_to = "gen_events.ts")]

crates/yaak/Cargo.toml

@@ -6,6 +6,7 @@ publish = false
 
 [dependencies]
 async-trait = "0.1"
+base64 = "0.22.1" # For carrying body chunks over a text-only plugin transport
 log = { workspace = true }
 md5 = "0.8.0"
 serde_json = { workspace = true }

crates/yaak/src/lib.rs

@@ -3,6 +3,7 @@ pub mod export;
 pub mod import;
 pub mod plugin_events;
 pub mod render;
+pub mod response_body;
 pub mod send;
 
 pub use error::Error;

crates/yaak/src/plugin_events.rs

@@ -1,3 +1,6 @@
+use crate::response_body::ResponseBodyStore;
+use base64::Engine;
+use base64::prelude::BASE64_STANDARD;
 use yaak_models::models::AnyModel;
 use yaak_models::query_manager::QueryManager;
 use yaak_models::util::UpdateSource;
@@ -5,12 +8,14 @@ use yaak_plugins::events::{
     CloseWindowRequest, CopyTextRequest, DeleteKeyValueRequest, DeleteKeyValueResponse,
     DeleteModelRequest, DeleteModelResponse, ErrorResponse, FindHttpResponsesRequest,
     FindHttpResponsesResponse, GetCookieValueRequest, GetHttpRequestByIdRequest,
-    GetHttpRequestByIdResponse, GetKeyValueRequest, GetKeyValueResponse, InternalEventPayload,
-    ListCookieNamesRequest, ListFoldersRequest, ListFoldersResponse, ListHttpRequestsRequest,
-    ListHttpRequestsResponse, ListOpenWorkspacesRequest, OpenExternalUrlRequest, OpenWindowRequest,
-    PromptFormRequest, PromptTextRequest, ReloadResponse, RenderGrpcRequestRequest,
-    RenderHttpRequestRequest, SendHttpRequestRequest, SetKeyValueRequest, ShowToastRequest,
-    TemplateRenderRequest, UpsertModelRequest, UpsertModelResponse, WindowInfoRequest,
+    GetHttpRequestByIdResponse, GetHttpResponseBodyInfoRequest, GetHttpResponseBodyInfoResponse,
+    GetKeyValueRequest, GetKeyValueResponse, InternalEventPayload, ListCookieNamesRequest,
+    ListFoldersRequest, ListFoldersResponse, ListHttpRequestsRequest, ListHttpRequestsResponse,
+    ListOpenWorkspacesRequest, OpenExternalUrlRequest, OpenWindowRequest, PromptFormRequest,
+    PromptTextRequest, ReadHttpResponseBodyChunkRequest, ReadHttpResponseBodyChunkResponse,
+    ReloadResponse, RenderGrpcRequestRequest, RenderHttpRequestRequest, SendHttpRequestRequest,
+    SetKeyValueRequest, ShowToastRequest, TemplateRenderRequest, UpsertModelRequest,
+    UpsertModelResponse, WindowInfoRequest,
 };
 
 pub struct SharedPluginEventContext<'a> {
@@ -40,6 +45,8 @@ pub enum SharedRequest<'a> {
     ListFolders(&'a ListFoldersRequest),
     ListHttpRequests(&'a ListHttpRequestsRequest),
     FindHttpResponses(&'a FindHttpResponsesRequest),
+    GetHttpResponseBodyInfo(&'a GetHttpResponseBodyInfoRequest),
+    ReadHttpResponseBodyChunk(&'a ReadHttpResponseBodyChunkRequest),
     UpsertModel(&'a UpsertModelRequest),
     DeleteModel(&'a DeleteModelRequest),
 }
@@ -136,6 +143,12 @@ impl<'a> From<&'a InternalEventPayload> for GroupedPluginRequest<'a> {
             InternalEventPayload::FindHttpResponsesRequest(req) => {
                 GroupedPluginRequest::Shared(SharedRequest::FindHttpResponses(req))
             }
+            InternalEventPayload::GetHttpResponseBodyInfoRequest(req) => {
+                GroupedPluginRequest::Shared(SharedRequest::GetHttpResponseBodyInfo(req))
+            }
+            InternalEventPayload::ReadHttpResponseBodyChunkRequest(req) => {
+                GroupedPluginRequest::Shared(SharedRequest::ReadHttpResponseBodyChunk(req))
+            }
             InternalEventPayload::UpsertModelRequest(req) => {
                 GroupedPluginRequest::Shared(SharedRequest::UpsertModel(req))
             }
@@ -182,13 +195,17 @@ impl<'a> From<&'a InternalEventPayload> for GroupedPluginRequest<'a> {
 
 pub fn handle_shared_plugin_event<'a>(
     query_manager: &QueryManager,
+    body_store: &dyn ResponseBodyStore,
     payload: &'a InternalEventPayload,
     context: SharedPluginEventContext<'_>,
 ) -> GroupedPluginEvent<'a> {
     match GroupedPluginRequest::from(payload) {
-        GroupedPluginRequest::Shared(req) => {
-            GroupedPluginEvent::Handled(Some(build_shared_reply(query_manager, req, context)))
-        }
+        GroupedPluginRequest::Shared(req) => GroupedPluginEvent::Handled(Some(build_shared_reply(
+            query_manager,
+            body_store,
+            req,
+            context,
+        ))),
         GroupedPluginRequest::Host(req) => GroupedPluginEvent::ToHandle(req),
         GroupedPluginRequest::Ignore => GroupedPluginEvent::Handled(None),
     }
@@ -196,6 +213,7 @@ pub fn handle_shared_plugin_event<'a>(
 
 fn build_shared_reply(
     query_manager: &QueryManager,
+    body_store: &dyn ResponseBodyStore,
     request: SharedRequest<'_>,
     context: SharedPluginEventContext<'_>,
 ) -> InternalEventPayload {
@@ -283,6 +301,31 @@ fn build_shared_reply(
                 http_responses,
             })
         }
+        SharedRequest::GetHttpResponseBodyInfo(req) => match body_store.info(&req.response_id) {
+            Ok(info) => InternalEventPayload::GetHttpResponseBodyInfoResponse(
+                GetHttpResponseBodyInfoResponse {
+                    content_length: info.content_length,
+                    content_type: info.content_type,
+                    complete: info.complete,
+                },
+            ),
+            Err(err) => InternalEventPayload::ErrorResponse(ErrorResponse {
+                error: format!("Failed to read body of response {}: {err}", req.response_id),
+            }),
+        },
+        SharedRequest::ReadHttpResponseBodyChunk(req) => {
+            match body_store.read_chunk(&req.response_id, req.offset, req.length) {
+                Ok(bytes) => InternalEventPayload::ReadHttpResponseBodyChunkResponse(
+                    ReadHttpResponseBodyChunkResponse {
+                        length: bytes.len() as u64,
+                        data: BASE64_STANDARD.encode(bytes),
+                    },
+                ),
+                Err(err) => InternalEventPayload::ErrorResponse(ErrorResponse {
+                    error: format!("Failed to read body of response {}: {err}", req.response_id),
+                }),
+            }
+        }
         SharedRequest::UpsertModel(req) => {
             use AnyModel::*;
 
@@ -437,10 +480,26 @@ fn build_shared_reply(
 #[cfg(test)]
 mod tests {
     use super::*;
+    use crate::response_body::{FileResponseBodyStore, ResponseBodyInfo};
+    use std::cell::RefCell;
     use tempfile::TempDir;
     use yaak_models::models::{AnyModel, Folder, HttpRequest, Workspace};
     use yaak_models::util::UpdateSource;
 
+    /// The real dispatch, with the store the desktop and CLI hand it.
+    fn dispatch<'a>(
+        query_manager: &QueryManager,
+        payload: &'a InternalEventPayload,
+        context: SharedPluginEventContext<'_>,
+    ) -> GroupedPluginEvent<'a> {
+        handle_shared_plugin_event(
+            query_manager,
+            &FileResponseBodyStore::new(query_manager),
+            payload,
+            context,
+        )
+    }
+
     fn seed_query_manager() -> (QueryManager, TempDir) {
         let temp_dir = TempDir::new().expect("Failed to create temp dir");
         let db_path = temp_dir.path().join("db.sqlite");
@@ -498,7 +557,7 @@ mod tests {
         let payload = InternalEventPayload::ListHttpRequestsRequest(
             yaak_plugins::events::ListHttpRequestsRequest { folder_id: None },
         );
-        let result = handle_shared_plugin_event(
+        let result = dispatch(
             &query_manager,
             &payload,
             SharedPluginEventContext { plugin_name: "@yaak/test", workspace_id: None },
@@ -517,7 +576,7 @@ mod tests {
         let by_workspace_payload = InternalEventPayload::ListHttpRequestsRequest(
             yaak_plugins::events::ListHttpRequestsRequest { folder_id: None },
         );
-        let by_workspace = handle_shared_plugin_event(
+        let by_workspace = dispatch(
             &query_manager,
             &by_workspace_payload,
             SharedPluginEventContext { plugin_name: "@yaak/test", workspace_id: Some("wk_test") },
@@ -536,7 +595,7 @@ mod tests {
                 folder_id: Some("fl_test".to_string()),
             },
         );
-        let by_folder = handle_shared_plugin_event(
+        let by_folder = dispatch(
             &query_manager,
             &by_folder_payload,
             SharedPluginEventContext { plugin_name: "@yaak/test", workspace_id: None },
@@ -559,7 +618,7 @@ mod tests {
             limit: Some(1),
         });
 
-        let result = handle_shared_plugin_event(
+        let result = dispatch(
             &query_manager,
             &payload,
             SharedPluginEventContext { plugin_name: "@yaak/test", workspace_id: Some("wk_test") },
@@ -575,6 +634,105 @@ mod tests {
         }
     }
 
+    /// A store that answers from memory, standing in for whatever holds the
+    /// bytes — the point being that the dispatch below never learns which.
+    struct FakeBodyStore {
+        body: Vec<u8>,
+        reads: RefCell<Vec<(u64, u64)>>,
+    }
+
+    impl ResponseBodyStore for FakeBodyStore {
+        fn info(&self, _response_id: &str) -> crate::error::Result<ResponseBodyInfo> {
+            Ok(ResponseBodyInfo {
+                content_length: self.body.len() as u64,
+                content_type: Some("text/plain; charset=utf-8".to_string()),
+                complete: true,
+            })
+        }
+
+        fn read_chunk(
+            &self,
+            _response_id: &str,
+            offset: u64,
+            length: u64,
+        ) -> crate::error::Result<Vec<u8>> {
+            self.reads.borrow_mut().push((offset, length));
+            let start = (offset as usize).min(self.body.len());
+            let end = (start + length as usize).min(self.body.len());
+            Ok(self.body[start..end].to_vec())
+        }
+    }
+
+    #[test]
+    fn response_body_is_read_by_id_through_the_store() {
+        let (query_manager, _temp_dir) = seed_query_manager();
+        let store = FakeBodyStore { body: b"hello".to_vec(), reads: RefCell::new(Vec::new()) };
+
+        let info_payload = InternalEventPayload::GetHttpResponseBodyInfoRequest(
+            GetHttpResponseBodyInfoRequest { response_id: "rs_test".to_string() },
+        );
+        let info = handle_shared_plugin_event(
+            &query_manager,
+            &store,
+            &info_payload,
+            SharedPluginEventContext { plugin_name: "@yaak/test", workspace_id: None },
+        );
+        match info {
+            GroupedPluginEvent::Handled(Some(
+                InternalEventPayload::GetHttpResponseBodyInfoResponse(resp),
+            )) => {
+                assert_eq!(resp.content_length, 5);
+                assert_eq!(resp.content_type.as_deref(), Some("text/plain; charset=utf-8"));
+            }
+            other => panic!("unexpected body info result: {other:?}"),
+        }
+
+        let chunk_payload = InternalEventPayload::ReadHttpResponseBodyChunkRequest(
+            ReadHttpResponseBodyChunkRequest {
+                response_id: "rs_test".to_string(),
+                offset: 1,
+                length: 3,
+            },
+        );
+        let chunk = handle_shared_plugin_event(
+            &query_manager,
+            &store,
+            &chunk_payload,
+            SharedPluginEventContext { plugin_name: "@yaak/test", workspace_id: None },
+        );
+        match chunk {
+            GroupedPluginEvent::Handled(Some(
+                InternalEventPayload::ReadHttpResponseBodyChunkResponse(resp),
+            )) => {
+                assert_eq!(resp.length, 3);
+                assert_eq!(BASE64_STANDARD.decode(resp.data).unwrap(), b"ell");
+            }
+            other => panic!("unexpected body chunk result: {other:?}"),
+        }
+
+        assert_eq!(*store.reads.borrow(), vec![(1, 3)]);
+    }
+
+    #[test]
+    fn an_unreadable_response_body_becomes_an_error_reply() {
+        let (query_manager, _temp_dir) = seed_query_manager();
+        let payload = InternalEventPayload::GetHttpResponseBodyInfoRequest(
+            GetHttpResponseBodyInfoRequest { response_id: "rs_never_persisted".to_string() },
+        );
+        let result = dispatch(
+            &query_manager,
+            &payload,
+            SharedPluginEventContext { plugin_name: "@yaak/test", workspace_id: None },
+        );
+
+        match result {
+            GroupedPluginEvent::Handled(Some(InternalEventPayload::ErrorResponse(resp))) => {
+                assert!(resp.error.contains("rs_never_persisted"), "unhelpful error: {}", resp.error)
+            }
+            other => panic!("unexpected missing-response result: {other:?}"),
+        }
+    }
+
     #[test]
     fn upsert_and_delete_model_are_shared_handled() {
         let (query_manager, _temp_dir) = seed_query_manager();
@@ -590,7 +748,7 @@ mod tests {
             }),
         });
 
-        let upsert_result = handle_shared_plugin_event(
+        let upsert_result = dispatch(
             &query_manager,
             &upsert_payload,
             SharedPluginEventContext { plugin_name: "@yaak/test", workspace_id: Some("wk_test") },
@@ -609,7 +767,7 @@ mod tests {
             model: "http_request".to_string(),
             id: "rq_test".to_string(),
         });
-        let delete_result = handle_shared_plugin_event(
+        let delete_result = dispatch(
             &query_manager,
             &delete_payload,
             SharedPluginEventContext { plugin_name: "@yaak/test", workspace_id: Some("wk_test") },
@@ -631,7 +789,7 @@ mod tests {
         let payload = InternalEventPayload::WindowInfoRequest(WindowInfoRequest {
             label: "main".to_string(),
         });
-        let result = handle_shared_plugin_event(
+        let result = dispatch(
             &query_manager,
             &payload,
             SharedPluginEventContext { plugin_name: "@yaak/test", workspace_id: None },

crates/yaak/src/response_body.rs

@@ -0,0 +1,232 @@
+//! Reading response bodies back out, by response id.
+//!
+//! Plugins only ever name a response. Where its bytes actually live — files the
+//! engine wrote under `<data dir>/responses/<id>` today, blob rows later — is
+//! behind [`ResponseBodyStore`], so moving the bytes is a change to this file
+//! and nothing a plugin can see.
+//!
+//! Only saved responses are reachable by id. A send that saved nothing hands
+//! its body back with the reply instead, which is the only copy of it there is.
+
+use crate::error::Result;
+use std::fs::File;
+use std::io::{Read, Seek, SeekFrom};
+use yaak_models::models::HttpResponseState;
+use yaak_models::query_manager::QueryManager;
+
+/// The most bytes one read will hand back, however much was asked for.
+///
+/// A chunk is buffered whole and, on the desktop transport, base64'd into a
+/// single WebSocket frame, so an unbounded request is a way to make the host
+/// allocate on a plugin's say-so.
+pub const MAX_CHUNK_BYTES: u64 = 8 * 1024 * 1024;
+
+/// What a stored body is, without reading any of it.
+#[derive(Debug, Clone, Default)]
+pub struct ResponseBodyInfo {
+    /// Bytes actually stored, which is not necessarily what `Content-Length`
+    /// claimed. Zero when the response has no body.
+    pub content_length: u64,
+    /// The response's `Content-Type` header, verbatim.
+    pub content_type: Option<String>,
+    /// Whether the response has finished arriving, so `content_length` is
+    /// final. A body still being written grows past it.
+    pub complete: bool,
+}
+
+/// Somewhere response bodies can be read from, a window at a time.
+///
+/// Reads are repeatable — the bytes are durable, so nothing is consumed by
+/// looking at it.
+pub trait ResponseBodyStore {
+    fn info(&self, response_id: &str) -> Result<ResponseBodyInfo>;
+
+    /// Bytes `[offset, offset + length)`, clamped to what is there. A short
+    /// read means the body ended.
+    fn read_chunk(&self, response_id: &str, offset: u64, length: u64) -> Result<Vec<u8>>;
+}
+
+/// The desktop and CLI store: the database says where the file is, and the
+/// filesystem holds it.
+pub struct FileResponseBodyStore<'a> {
+    query_manager: &'a QueryManager,
+}
+
+impl<'a> FileResponseBodyStore<'a> {
+    pub fn new(query_manager: &'a QueryManager) -> Self {
+        Self { query_manager }
+    }
+
+    /// The file backing a response, or `None` when it stored no body.
+    ///
+    /// Only responses the store knows about are reachable here. A send with no
+    /// request behind it never reaches the store at all, and its bytes come
+    /// back from the send instead — see `SendHttpRequestResponse::body`.
+    fn body_path(&self, response_id: &str) -> Result<Option<String>> {
+        Ok(self.query_manager.connect().get_http_response(response_id)?.body_path)
+    }
+}
+
+impl ResponseBodyStore for FileResponseBodyStore<'_> {
+    fn info(&self, response_id: &str) -> Result<ResponseBodyInfo> {
+        let response = self.query_manager.connect().get_http_response(response_id)?;
+
+        let content_type = response
+            .headers
+            .iter()
+            .find(|h| h.name.eq_ignore_ascii_case("content-type"))
+            .map(|h| h.value.clone());
+
+        let content_length = match response.body_path {
+            Some(path) => std::fs::metadata(path)?.len(),
+            None => 0,
+        };
+
+        Ok(ResponseBodyInfo {
+            content_length,
+            content_type,
+            // Closed is the one terminal state: success, error, and cancel all end there.
+            complete: matches!(response.state, HttpResponseState::Closed),
+        })
+    }
+
+    fn read_chunk(&self, response_id: &str, offset: u64, length: u64) -> Result<Vec<u8>> {
+        let Some(path) = self.body_path(response_id)? else {
+            return Ok(Vec::new());
+        };
+
+        let length = length.min(MAX_CHUNK_BYTES);
+        if length == 0 {
+            return Ok(Vec::new());
+        }
+
+        let mut file = File::open(path)?;
+        file.seek(SeekFrom::Start(offset))?;
+
+        let mut buf = Vec::new();
+        file.take(length).read_to_end(&mut buf)?;
+        Ok(buf)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::io::Write;
+    use tempfile::TempDir;
+    use yaak_models::models::{HttpRequest, HttpResponse, HttpResponseHeader, Workspace};
+    use yaak_models::util::UpdateSource;
+
+    fn seed(body: Option<&[u8]>) -> (QueryManager, TempDir, String) {
+        let temp_dir = TempDir::new().unwrap();
+        let (query_manager, blob_manager, _rx) = yaak_models::init_standalone(
+            &temp_dir.path().join("db.sqlite"),
+            &temp_dir.path().join("blobs.sqlite"),
+        )
+        .unwrap();
+
+        query_manager
+            .connect()
+            .upsert_workspace(
+                &Workspace { id: "wk_test".to_string(), ..Default::default() },
+                &UpdateSource::Sync,
+            )
+            .unwrap();
+
+        query_manager
+            .connect()
+            .upsert_http_request(
+                &HttpRequest {
+                    id: "rq_test".to_string(),
+                    workspace_id: "wk_test".to_string(),
+                    ..Default::default()
+                },
+                &UpdateSource::Sync,
+            )
+            .unwrap();
+
+        let body_path = body.map(|bytes| {
+            let path = temp_dir.path().join("body");
+            let mut f = std::fs::File::create(&path).unwrap();
+            f.write_all(bytes).unwrap();
+            path.to_string_lossy().to_string()
+        });
+
+        let response = query_manager
+            .connect()
+            .upsert_http_response(
+                &HttpResponse {
+                    workspace_id: "wk_test".to_string(),
+                    request_id: "rq_test".to_string(),
+                    body_path,
+                    headers: vec![HttpResponseHeader {
+                        name: "Content-Type".to_string(),
+                        value: "application/json; charset=utf-8".to_string(),
+                    }],
+                    ..Default::default()
+                },
+                &UpdateSource::Sync,
+                &blob_manager,
+            )
+            .unwrap();
+
+        let id = response.id.clone();
+        (query_manager, temp_dir, id)
+    }
+
+    #[test]
+    fn info_reports_stored_size_and_content_type() {
+        let (qm, _tmp, id) = seed(Some(b"hello world"));
+        let info = FileResponseBodyStore::new(&qm).info(&id).unwrap();
+        assert_eq!(info.content_length, 11);
+        assert_eq!(info.content_type.as_deref(), Some("application/json; charset=utf-8"));
+    }
+
+    #[test]
+    fn chunks_cover_the_body_and_stop_short_at_the_end() {
+        let (qm, _tmp, id) = seed(Some(b"hello world"));
+        let store = FileResponseBodyStore::new(&qm);
+        assert_eq!(store.read_chunk(&id, 0, 5).unwrap(), b"hello");
+        assert_eq!(store.read_chunk(&id, 6, 100).unwrap(), b"world");
+        assert!(store.read_chunk(&id, 11, 100).unwrap().is_empty());
+        // Reading the same window twice gives the same bytes; nothing is consumed.
+        assert_eq!(store.read_chunk(&id, 0, 5).unwrap(), b"hello");
+    }
+
+    #[test]
+    fn a_response_with_no_body_is_empty_not_an_error() {
+        let (qm, _tmp, id) = seed(None);
+        let store = FileResponseBodyStore::new(&qm);
+        assert_eq!(store.info(&id).unwrap().content_length, 0);
+        assert!(store.read_chunk(&id, 0, 100).unwrap().is_empty());
+    }
+
+    #[test]
+    fn complete_tracks_whether_the_response_has_closed() {
+        let (qm, _tmp, id) = seed(Some(b"partial"));
+        // Seeded responses default to Initialized: still arriving.
+        assert!(!FileResponseBodyStore::new(&qm).info(&id).unwrap().complete);
+
+        let mut response = qm.connect().get_http_response(&id).unwrap();
+        response.state = HttpResponseState::Closed;
+        qm.connect().update_http_response_if_id(&response, &UpdateSource::Sync).unwrap();
+
+        assert!(FileResponseBodyStore::new(&qm).info(&id).unwrap().complete);
+    }
+
+    #[test]
+    fn an_unknown_response_fails() {
+        let (qm, _tmp, _id) = seed(Some(b"hi"));
+        assert!(FileResponseBodyStore::new(&qm).info("rs_nope").is_err());
+    }
+
+    #[test]
+    fn an_unsaved_response_is_not_reachable_by_id() {
+        // Its bytes rode back with the send; there is nothing here to find, and
+        // guessing at a file named for the id is exactly what this must not do.
+        let (qm, tmp, _id) = seed(Some(b"hi"));
+        std::fs::write(tmp.path().join("rs_ephemeral1"), b"access_token=abc").unwrap();
+
+        assert!(FileResponseBodyStore::new(&qm).info("rs_ephemeral1").is_err());
+    }
+}

crates/yaak/src/send.rs

@@ -354,6 +354,19 @@ pub enum ResponseBody {
     Returned(Vec<u8>),
 }
 
+impl ResponseBody {
+    /// The bytes, when this is the only copy of them.
+    ///
+    /// Stored and streamed bodies belong to whoever holds them; only `Returned`
+    /// has to travel back to the caller.
+    pub fn returned_bytes(&self) -> Option<&[u8]> {
+        match self {
+            ResponseBody::Returned(bytes) => Some(bytes),
+            ResponseBody::Stored | ResponseBody::Streamed => None,
+        }
+    }
+}
+
 pub struct SendHttpRequestResult {
     pub rendered_request: HttpRequest,
     pub response: HttpResponse,