33 lines
1.3 KiB
TypeScript
33 lines
1.3 KiB
TypeScript
/** Durable request-route lookup for one closed model step. @module @deepseek-ai/dsh-llm-retry/history */
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import type { SessionEvent } from '@deepseek-ai/dsh-session'
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/**
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* Find the provider in force when one step closed, excluding later recovery mutations.
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* Request headers remain effective across turn boundaries until a newer full
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* snapshot changes them; every provider change requires a newer full snapshot.
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* @param events - session events containing the closed step.
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* @param turn - turn that owns the failed step.
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* @param step - failed step whose provider is required.
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* @returns the provider from the request header in force at that step boundary.
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*/
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export function providerForClosedStep(
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events: readonly SessionEvent[],
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turn: number,
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step: number,
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): string | undefined {
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const stepEndIndex = events.findLastIndex(event =>
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event.type === 'step/end'
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&& event.data.turn === turn
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&& event.data.step === step,
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)
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if (stepEndIndex < 0) return undefined
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for (let index = stepEndIndex; index >= 0; index -= 1) {
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// The loop bounds prove this indexed read exists.
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// oxlint-disable-next-line typescript/no-non-null-assertion
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const event = events[index]!
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if (event.type === 'request/header') return event.data.header.config.provider
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}
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return undefined
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}
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