| 16 | * events are never dropped regardless of how fast they arrive. |
| 17 | */ |
| 18 | export async function* parseStream( |
| 19 | response: Response, |
| 20 | opts?: ParseStreamOptions |
| 21 | ): AsyncGenerator<StreamEvent> { |
| 22 | const reader = response.body?.getReader(); |
| 23 | if (!reader) throw new ApiError(0, "No response body", "network"); |
| 24 | |
| 25 | const decoder = new TextDecoder(); |
| 26 | let buffer = ""; |
| 27 | const startTime = Date.now(); |
| 28 | let tokensReceived = 0; |
| 29 | |
| 30 | try { |
| 31 | while (true) { |
| 32 | if (opts?.signal?.aborted) break; |
| 33 | |
| 34 | const { done, value } = await reader.read(); |
| 35 | if (done) break; |
| 36 | |
| 37 | buffer += decoder.decode(value, { stream: true }); |
| 38 | |
| 39 | // Process all complete lines. The last (potentially incomplete) line |
| 40 | // stays in the buffer. |
| 41 | const lines = buffer.split("\n"); |
| 42 | buffer = lines.pop() ?? ""; |
| 43 | |
| 44 | for (const line of lines) { |
| 45 | if (!line.trim()) continue; // blank line = SSE event separator |
| 46 | if (!line.startsWith("data: ")) continue; |
| 47 | |
| 48 | const data = line.slice(6).trim(); |
| 49 | if (data === "[DONE]") return; |
| 50 | |
| 51 | try { |
| 52 | const event = JSON.parse(data) as StreamEvent; |
| 53 | |
| 54 | if ( |
| 55 | event.type === "content_block_delta" && |
| 56 | event.delta.type === "text_delta" |
| 57 | ) { |
| 58 | tokensReceived += event.delta.text.length; |
| 59 | } |
| 60 | |
| 61 | opts?.onProgress?.({ |
| 62 | tokensReceived, |
| 63 | elapsedMs: Date.now() - startTime, |
| 64 | isComplete: false, |
| 65 | }); |
| 66 | |
| 67 | yield event; |
| 68 | } catch { |
| 69 | // skip malformed JSON — keep going |
| 70 | } |
| 71 | } |
| 72 | } |
| 73 | } finally { |
| 74 | reader.releaseLock(); |
| 75 | opts?.onProgress?.({ |