71 lines
3.0 KiB
TypeScript
71 lines
3.0 KiB
TypeScript
/**
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* Request-header reconstruction utilities over full `request/header` session
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* events. Anyone holding a session log reconstructs the {@link EpochHeader}
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* any request was built under by taking the latest canonical snapshot; the
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* loop uses the same equality helper to avoid logging unchanged headers.
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*
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* @module dsh-session/request-header
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*/
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import { callConfigEquals } from '@deepseek-ai/dsh-llm'
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import type { Message, ToolSchema } from '@deepseek-ai/dsh-llm'
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import type { EpochHeader, SessionEvent } from './types.ts'
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/**
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* Normalize a header to canonical form: an empty system prompt, an empty tool
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* list, and an empty session prefix become absent fields, matching how requests
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* are built. Logging, folding, and comparison use this one representation.
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* @param header - the header to normalize (not mutated).
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* @returns the canonical header.
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*/
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export function canonicalHeader(header: EpochHeader): EpochHeader {
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return {
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config: header.config,
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...header.system !== undefined && header.system.length > 0 ? { system: header.system } : {},
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...header.tools !== undefined && header.tools.length > 0 ? { tools: header.tools } : {},
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...header.messagePrefix !== undefined && header.messagePrefix.length > 0 ? { messagePrefix: header.messagePrefix } : {},
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}
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}
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/** Canonical JSON equality for tool schemas assembled through the same path. */
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function sameSchema(a: ToolSchema, b: ToolSchema): boolean {
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return JSON.stringify(a) === JSON.stringify(b)
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}
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/** Canonical JSON equality over session-prefix arrays; absence equals empty. */
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function sameMessages(a: readonly Message[] | undefined, b: readonly Message[] | undefined): boolean {
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return JSON.stringify(a ?? []) === JSON.stringify(b ?? [])
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}
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/**
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* Field-wise equality over canonical headers. Tool schemas compare in order;
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* the session prefix compares as canonical JSON.
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* @param a - one canonical header.
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* @param b - the other.
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* @returns whether config, system, tools, and session prefix all match.
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*/
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export function headerEquals(a: EpochHeader, b: EpochHeader): boolean {
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if (!callConfigEquals(a.config, b.config) || a.system !== b.system) return false
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if (!sameMessages(a.messagePrefix, b.messagePrefix)) return false
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const at = a.tools ?? []
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const bt = b.tools ?? []
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return at.length === bt.length && at.every((tool, i) => sameSchema(tool, bt[i] as ToolSchema))
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}
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/**
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* Fold the header events of a log (or any prefix) into the
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* {@link EpochHeader} in force after the last snapshot. Non-header events are
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* skipped. This is the pure offline reconstruction path; the live session
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* tracks the same fold incrementally.
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* @param events - session events in log order.
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* @param from - a previously folded state to continue from.
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* @returns the latest canonical header, or undefined when none exists yet.
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*/
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export function foldRequestHeader(events: readonly SessionEvent[], from?: EpochHeader): EpochHeader | undefined {
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let state = from
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for (const event of events) {
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if (event.type === 'request/header') state = canonicalHeader(event.data.header)
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}
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return state
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}
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