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/**
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
*/
/**
* ===================================================================
* ARCHITECTURE ROADMAP: The Compaction Waterfall
* ===================================================================
* This module prevents LLM context window collapse and reduces TTFT
* (Time-To-First-Token) latency by deterministically compacting massive
* background tool payloads before they are dispatched to the API.
* * Planned Stages:
* - Stage 1 (Active): ID-Based Upsert. Deduplicates repetitive get_page_content reads.
* - Stage 2 (Planned): Proportional Bottom-Up Shave. Truncates old page content/Search payloads.
* - Stage 3 (Planned): Copy-Paste Tax. Truncates massive old user queries.
* - Stage 4 (Planned): LRU Eviction. Drops oldest conversation turns as a failsafe.
* ===================================================================
*/
/**
* Scans the conversation history, tracks the latest fetch for each URL, and
* replaces older redundant page content with a lightweight placeholder.
*
* CRITICAL ASSUMPTION: This logic relies on an implicit contract with the
* `get_page_content` tool. It assumes the tool returns a JSON-stringified array
* of text contents that strictly matches the exact index order and length of
* the requested `url_list` arguments.
*
* @param {Array<object>} messages - The cloned conversation history array.
* @returns {Array<object>} The array with compacted get_page_content payloads.
*/
function deduplicatePageContent(messages) {
const callIdToUrls = new Map();
const urlToLatestCallId = new Map();
// PASS 1: Build the relational map from the Assistant's requests
for (const msg of messages) {
if (msg.role === "assistant" && Array.isArray(msg.tool_calls)) {
for (const toolCall of msg.tool_calls) {
if (
toolCall.type === "function" &&
toolCall.function?.name === "get_page_content"
) {
try {
const args = JSON.parse(toolCall.function.arguments);
if (Array.isArray(args.url_list)) {
// Map the Call ID to the ordered array of URLs it requested
callIdToUrls.set(toolCall.id, args.url_list);
// Continually overwrite to guarantee we only store the LATEST ID for each URL
for (const url of args.url_list) {
urlToLatestCallId.set(url, toolCall.id);
}
}
} catch (error) {
console.warn(
"SmartWindow: Failed to parse get_page_content arguments during compaction.",
error
);
}
}
}
}
}
// PASS 2: Execute the replacement on the Tool responses
for (const msg of messages) {
if (
msg.role === "tool" &&
msg.name === "get_page_content" &&
msg.tool_call_id
) {
const requestedUrls = callIdToUrls.get(msg.tool_call_id);
if (requestedUrls) {
try {
// The get_page_content tool returns a JSON stringified array of text blocks
const contentArray = JSON.parse(msg.content);
if (Array.isArray(contentArray)) {
const compactedContentArray = contentArray.map(
(textContent, index) => {
// Relies on the assumption that contentArray[index] maps perfectly to requestedUrls[index]
const url = requestedUrls[index];
// If we tracked this URL, and this tool_call_id is NOT the newest one, drop the heavy text
if (url && urlToLatestCallId.get(url) !== msg.tool_call_id) {
return `[System Note: Content omitted for ${url}. A fresher read occurs later in context.]`;
}
return textContent;
}
);
msg.content = JSON.stringify(compactedContentArray);
}
} catch (error) {
console.warn(
`SmartWindow: Failed to parse tool content for ID ${msg.tool_call_id}.`,
error
);
}
}
}
}
return messages;
}
/**
* MAIN ENTRY POINT
* Orchestrates the prompt compaction waterfall.
*
* @param {Array<object>} rawMessages - The original conversation history.
* @returns {Array<object>} The optimized array ready to be sent to the LLM API.
*/
export function compactMessages(rawMessages) {
try {
// Deep clone to guarantee we never mutate the frontend's active UI state
let compactedMessages = structuredClone(rawMessages);
// Stage 1: Deduplication (Always runs, zero semantic loss)
compactedMessages = deduplicatePageContent(compactedMessages);
// Future stages (Threshold checking, proportional shaving) will be injected here
return compactedMessages;
} catch (error) {
console.error(
"SmartWindow: Prompt compaction failed. Falling back to raw messages.",
error
);
return rawMessages;
}
}