# frozen_string_literal: true

require 'net/http'
require 'json'

# Client for the external web service that turns text into embedding
# vectors for nearest neighbor search (pgvector).
#
#   Vectorizer.embed('A fast text editor') # => [0.123, -0.456, ...]
#
# The service URL can be overridden with the VECTOR_SERVICE_URL
# environment variable.
class Vectorizer
  # Raised when the vector service cannot be reached or returns garbage
  class Error < StandardError; end

  DEFAULT_URL = 'https://vector-search.workaround.org/vector'

  class << self
    # Compute the embedding vector for the given text.
    # Returns an array of floats.
    def embed(text)
      new.embed(text)
    end

    def service_url
      ENV.fetch('VECTOR_SERVICE_URL', DEFAULT_URL)
    end
  end

  def embed(text)
    response = post_text(text)

    unless response.is_a?(Net::HTTPSuccess)
      raise Error, "Vector service returned HTTP #{response.code}"
    end

    JSON.parse(response.body).fetch('vector')
  rescue JSON::ParserError => e
    raise Error, "Vector service returned invalid JSON: #{e.message}"
  rescue KeyError
    raise Error, 'Vector service response did not contain a "vector" field'
  end

  private

  def post_text(text)
    uri = URI.parse(self.class.service_url)
    request = build_request(uri, text)

    options = { use_ssl: uri.scheme == 'https', read_timeout: 30, open_timeout: 10 }
    Net::HTTP.start(uri.host, uri.port, **options) do |http|
      http.request(request)
    end
  rescue SocketError, Errno::ECONNREFUSED, Net::OpenTimeout, Net::ReadTimeout => e
    raise Error, "Could not reach vector service: #{e.message}"
  end

  def build_request(uri, text)
    request = Net::HTTP::Post.new(uri.request_uri)
    request['Content-Type'] = 'application/json'
    request.body = { text: text }.to_json

    # Optional Bearer token if the service runs with API_SECRET set
    secret = ENV['VECTOR_SERVICE_SECRET']
    request['Authorization'] = "Bearer #{secret}" if secret.present?

    request
  end
end