Class: Clacky::BedrockStreamAggregator

Inherits:
Object
  • Object
show all
Defined in:
lib/clacky/bedrock_stream_aggregator.rb

Overview

Reassembles a Bedrock Converse event stream into the same hash shape that MessageFormat::Bedrock.parse_response expects from a non-streaming response, while invoking on_chunk(input_tokens:, output_tokens:) as usage information accumulates.

Bedrock event-stream events handled (passed through as raw event JSON):

messageStart      → { role: "assistant" }
contentBlockStart → { start: {toolUse: {toolUseId, name}} | {}, contentBlockIndex: N }
contentBlockDelta → { delta: {text: "..."} | {toolUse: {input: "..."}}, contentBlockIndex: N }
contentBlockStop  → { contentBlockIndex: N }
messageStop       → { stopReason: "end_turn" | "tool_use" | "max_tokens" | ... }
metadata          → { usage: {inputTokens, outputTokens, cacheReadInputTokens, cacheWriteInputTokens}, metrics: {...} }

Tool-use input is streamed as a sequence of partial JSON strings; we concatenate and let the response parser leave it as a string for downstream tool dispatch (which calls JSON.parse with a {} fallback).

Instance Method Summary collapse

Constructor Details

#initialize(on_chunk: nil) ⇒ BedrockStreamAggregator

Returns a new instance of BedrockStreamAggregator.



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# File 'lib/clacky/bedrock_stream_aggregator.rb', line 24

def initialize(on_chunk: nil)
  @on_chunk = on_chunk
  @role = "assistant"
  @blocks = {}
  @stop_reason = nil
  @usage = {}
  @last_input_tokens = 0
  @last_output_tokens = 0
end

Instance Method Details

#handle(event, data_str) ⇒ Object 



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# File 'lib/clacky/bedrock_stream_aggregator.rb', line 34

def handle(event, data_str)
  data = parse_or_nil(data_str)
  return unless data

  case event
  when "messageStart"
    @role = data["role"] || @role
  when "contentBlockStart"
    idx = data["contentBlockIndex"] || @blocks.size
    start = data["start"] || {}
    if (tu = start["toolUse"])
      @blocks[idx] = { kind: :tool_use, id: tu["toolUseId"], name: tu["name"], input_str: +"" }
    else
      @blocks[idx] = { kind: :text, text: +"" }
    end
  when "contentBlockDelta"
    idx = data["contentBlockIndex"] || 0
    delta = data["delta"] || {}
    block = (@blocks[idx] ||= { kind: :text, text: +"" })
    if delta["text"]
      block[:kind] ||= :text
      block[:text] ||= +""
      block[:text] << delta["text"]
    elsif (tu = delta["toolUse"])
      block[:kind] = :tool_use
      block[:input_str] ||= +""
      block[:input_str] << tu["input"].to_s
      block[:id]   ||= tu["toolUseId"]
      block[:name] ||= tu["name"]
    elsif (rc = delta["reasoningContent"])
      block[:kind] = :reasoning
      block[:reasoning] ||= +""
      block[:reasoning] << rc["text"].to_s
    end
    emit_estimate_progress
  when "contentBlockStop"
    # Nothing to assemble: blocks are kept as-is until messageStop.
  when "messageStop"
    @stop_reason = data["stopReason"] || @stop_reason
  when "metadata"
    if (u = data["usage"])
      @usage.merge!(u)
      emit_usage_progress(u)
    end
  end
end

#to_h ⇒ Object

Render the canonical non-streaming Bedrock response hash so the existing MessageFormat::Bedrock.parse_response can consume it unchanged.



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# File 'lib/clacky/bedrock_stream_aggregator.rb', line 83

def to_h
  content_blocks = @blocks.keys.sort.map do |idx|
    b = @blocks[idx]
    case b[:kind]
    when :tool_use
      input_value = b[:input_str].to_s.empty? ? {} : (JSON.parse(b[:input_str]) rescue b[:input_str])
      { "toolUse" => { "toolUseId" => b[:id], "name" => b[:name], "input" => input_value } }
    else
      { "text" => b[:text].to_s }
    end
  end

  {
    "output"     => { "message" => { "role" => @role, "content" => content_blocks } },
    "stopReason" => @stop_reason,
    "usage"      => @usage
  }
end