{"version":3,"file":"sse-writer.cjs","names":[],"sources":["../src/sse-writer.ts"],"sourcesContent":["import type * as http from \"node:http\";\nimport type { SSEChunk, StreamingProfile, RecordedTimings } from \"./types.js\";\n\nexport function delay(ms: number, signal?: AbortSignal): Promise {\n if (ms <= 0 || signal?.aborted) return Promise.resolve();\n return new Promise((resolve) => {\n const timer = setTimeout(resolve, ms);\n signal?.addEventListener(\n \"abort\",\n () => {\n clearTimeout(timer);\n resolve();\n },\n { once: true },\n );\n });\n}\n\nexport interface StreamOptions {\n latency?: number;\n streamingProfile?: StreamingProfile;\n recordedTimings?: RecordedTimings;\n replaySpeed?: number;\n signal?: AbortSignal;\n onChunkSent?: () => void;\n /** When set, emitted as the final chunk before [DONE] (OpenAI stream_options.include_usage). */\n usageChunk?: SSEChunk;\n}\n\nexport function calculateDelay(\n chunkIndex: number,\n profile?: StreamingProfile,\n fallbackLatency?: number,\n recordedTimings?: RecordedTimings,\n replaySpeed?: number,\n): number {\n const speed = replaySpeed ?? 1.0;\n let delayMs: number;\n\n if (profile) {\n // StreamingProfile has highest precedence\n let fromProfile = true;\n if (chunkIndex === 0 && profile.ttft !== undefined) {\n delayMs = profile.ttft;\n } else if (profile.tps !== undefined && profile.tps > 0) {\n delayMs = 1000 / profile.tps;\n } else {\n delayMs = fallbackLatency ?? 0;\n fromProfile = false;\n }\n // Jitter only applies when the delay came from ttft/tps, not fallback\n if (fromProfile && profile.jitter && profile.jitter > 0) {\n delayMs *= 1 + (Math.random() * 2 - 1) * profile.jitter;\n if (delayMs < 0) delayMs = 0;\n }\n } else if (recordedTimings) {\n // Recorded timings (second precedence)\n if (chunkIndex === 0) {\n delayMs = recordedTimings.ttftMs;\n } else {\n const idx = chunkIndex - 1;\n if (idx < recordedTimings.interChunkDelaysMs.length) {\n delayMs = recordedTimings.interChunkDelaysMs[idx];\n } else {\n // Excess chunks: derive average from recorded inter-chunk delays\n const totalInterChunk = recordedTimings.interChunkDelaysMs.reduce((a, b) => a + b, 0);\n delayMs =\n recordedTimings.interChunkDelaysMs.length > 0\n ? totalInterChunk / recordedTimings.interChunkDelaysMs.length\n : 0;\n }\n }\n } else {\n delayMs = fallbackLatency ?? 0;\n }\n\n delayMs = Math.max(0, delayMs);\n return speed > 0 ? delayMs / speed : delayMs;\n}\n\nexport async function writeSSEStream(\n res: http.ServerResponse,\n chunks: SSEChunk[],\n optionsOrLatency?: number | StreamOptions,\n): Promise {\n const opts: StreamOptions =\n typeof optionsOrLatency === \"number\" ? { latency: optionsOrLatency } : (optionsOrLatency ?? {});\n const latency = opts.latency ?? 0;\n const profile = opts.streamingProfile;\n const { recordedTimings, replaySpeed } = opts;\n const signal = opts.signal;\n const onChunkSent = opts.onChunkSent;\n\n if (res.writableEnded) return true;\n res.setHeader(\"Content-Type\", \"text/event-stream\");\n res.setHeader(\"Cache-Control\", \"no-cache\");\n res.setHeader(\"Connection\", \"keep-alive\");\n\n let chunkIndex = 0;\n for (const chunk of chunks) {\n const chunkDelay = calculateDelay(chunkIndex, profile, latency, recordedTimings, replaySpeed);\n if (chunkDelay > 0) {\n await delay(chunkDelay, signal);\n }\n if (signal?.aborted) return false;\n if (res.writableEnded) return true;\n res.write(`data: ${JSON.stringify(chunk)}\\n\\n`);\n onChunkSent?.();\n if (signal?.aborted) return false;\n chunkIndex++;\n }\n\n if (!res.writableEnded) {\n if (opts.usageChunk) {\n res.write(`data: ${JSON.stringify(opts.usageChunk)}\\n\\n`);\n }\n res.write(\"data: [DONE]\\n\\n\");\n res.end();\n }\n return true;\n}\n\n/**\n * Default rate-limit response headers matching OpenAI's format.\n * Values are static — aimock doesn't track actual request counts.\n */\nconst RATE_LIMIT_HEADERS: Record = {\n \"x-ratelimit-limit-requests\": \"60\",\n \"x-ratelimit-limit-tokens\": \"150000\",\n \"x-ratelimit-remaining-requests\": \"0\",\n \"x-ratelimit-remaining-tokens\": \"0\",\n \"x-ratelimit-reset-requests\": \"1s\",\n \"x-ratelimit-reset-tokens\": \"6m0s\",\n};\n\nexport interface ErrorResponseOptions {\n /** Override the Retry-After header value (seconds). 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