Backend for editing previous queries

[ggordonhall]

This change set allows users to rephrase a query that they've already made and get a new answer. This is similar functionality to ChatGPT, but whereas they persist both the original and rephrased versions of a query (and their successive conversation states), we only store the state after query rephrasing, discarding everything else.

The approach is to add an additional parent_query_id parameter to /answer:

{
	"query": "...",
	"repo_ref": "...",
	"thread_id": "...",
	"parent_query_id": "..."
}

On receiving this payload the backend loads the Conversation by thread_id from SQLite. But, rather than using the entire history as context, we truncate Vec<Exchanges> at the point at which Exchange.id == parent_exchange_id. We only use the history up to parent_query_id as context.

To get this working a major refactor of answer.rs was in order:

• I removed llm_history. This information is now reproducible from Vec<Exchange> using the history() method which iterates over exchanges and builds a linear sequence of Message
• I moved paths and code_chunks into Exchange. Each Exchange in a conversation now stores the paths and code_chunks that were discovered by its functions. The conversation-level path and code_chunk state is now reproducible with code_chunks() and paths() methods on Agent. Code chunk canonicalisation now happens on the fly, but this shouldn't give a noticeable performance hit
• New StartStep and EndStep update types. We use these to tell the frontend that a step has started, and that it's ended. EndStep adds the result of the function to the Exchange
• Removed the Conversation struct. All functionality is now implemented on Agent.

Todo (this PR)

• We shouldn't stream intermediate function results to the frontend @calyptobai
• Implement the frontend logic, passing parent_query_id

Todo (future PR)

• Move function implementation logic into separate classes
• Move Agent out of webserver

[oppiliappan]

i believe some of this logic has changed: 047ccbf

Outdated