class Ai::UsageCost
  attr_reader :model_id, :input_tokens, :output_tokens

  class << self
    def from_llm_response(response)
      new \
        model_id: response.model_id,
        input_tokens: response.input_tokens,
        output_tokens: response.output_tokens
    end
  end

  def initialize(model_id:, input_tokens:, output_tokens:)
    @model_id = model_id
    @input_tokens = input_tokens
    @output_tokens = output_tokens
  end

  def in_microcents
    input_cost_in_microcents + output_cost_in_microcents
  end

  def input_cost_in_microcents
    calculate_token_cost(input_tokens, model_info.input_price_per_million)
  end

  def output_cost_in_microcents
    calculate_token_cost(output_tokens, model_info.output_price_per_million)
  end

  private
    def calculate_token_cost(token_count, price_per_million)
      return 0 unless price_per_million

      single_token_price = price_per_million.to_d / 1_000_000
      token_cost_dollars = token_count * single_token_price
      Ai::Quota::Money.wrap(token_cost_dollars).in_microcents
    end

    def model_info
      @model_info ||= RubyLLM.models.find(model_id)
    end
end