class Provider::Openai < Provider
  include LlmConcept

  # Subclass so errors caught in this provider are raised as Provider::Openai::Error
  Error = Class.new(Provider::Error)

  DEFAULT_MODEL = "gpt-4.1".freeze
  SUPPORTED_MODELS = %w[gpt-4 gpt-5 o1 o3].freeze
  VISION_CAPABLE_MODEL_PREFIXES = %w[gpt-4o gpt-4-turbo gpt-4.1 gpt-5 o1 o3].freeze

  # Returns the effective model that would be used by the provider.
  # Priority: explicit ENV > Setting > DEFAULT_MODEL.
  def self.effective_model
    ENV.fetch("OPENAI_MODEL") { Setting.openai_model }.presence || DEFAULT_MODEL
  end

  def initialize(access_token, uri_base: nil, model: nil)
    client_options = { access_token: access_token }
    llm_uri_base = uri_base.presence
    llm_model = model.presence
    client_options[:uri_base] = llm_uri_base if llm_uri_base.present?
    client_options[:request_timeout] = ENV.fetch("OPENAI_REQUEST_TIMEOUT", 60).to_i

    @client = ::OpenAI::Client.new(**client_options)
    @uri_base = llm_uri_base
    if custom_provider? && llm_model.blank?
      raise Error, "Model is required when using a custom OpenAI‑compatible provider"
    end
    @default_model = llm_model.presence || self.class.effective_model
  end

  def supports_model?(model)
    # If using custom uri_base, support any model
    return true if custom_provider?

    # Otherwise, check if model starts with any supported OpenAI prefix
    SUPPORTED_MODELS.any? { |prefix| model.start_with?(prefix) }
  end

  def supports_responses_endpoint?
    return @supports_responses_endpoint if defined?(@supports_responses_endpoint)

    env_override = ENV["OPENAI_SUPPORTS_RESPONSES_ENDPOINT"]
    if env_override.to_s.present?
      return @supports_responses_endpoint = ActiveModel::Type::Boolean.new.cast(env_override)
    end

    @supports_responses_endpoint = !custom_provider?
  end

  def provider_name
    custom_provider? ? "Custom OpenAI-compatible (#{@uri_base})" : "OpenAI"
  end

  def supported_models_description
    if custom_provider?
      @default_model.present? ? "configured model: #{@default_model}" : "any model"
    else
      "models starting with: #{SUPPORTED_MODELS.join(", ")}"
    end
  end

  def custom_provider?
    @uri_base.present?
  end

  # Token-budget knobs. Precedence: ENV > Setting > default. Defaults match
  # Ollama's historical 2048-token baseline so local small-context models work
  # out of the box. Users on larger-context cloud models can raise via ENV or
  # via the Self-Hosting settings page.
  def context_window
    positive_budget(ENV["LLM_CONTEXT_WINDOW"], Setting.llm_context_window, 2048)
  end

  def max_response_tokens
    positive_budget(ENV["LLM_MAX_RESPONSE_TOKENS"], Setting.llm_max_response_tokens, 512)
  end

  def system_prompt_reserve
    positive_budget(ENV["LLM_SYSTEM_PROMPT_RESERVE"], nil, 256)
  end

  def max_history_tokens
    explicit = ENV["LLM_MAX_HISTORY_TOKENS"].presence&.to_i
    return explicit if explicit&.positive?
    [ context_window - max_response_tokens - system_prompt_reserve, 256 ].max
  end

  # Budget available for a one-shot (non-chat) request's full input,
  # excluding reserved response tokens AND the system/instructions prompt.
  # Drives the batch slicer for the auto_categorize / auto_detect_merchants /
  # enhance_provider_merchants calls — each ships ~200–400 tokens of
  # instructions + JSON schema that aren't counted in `fixed_tokens`.
  def max_input_tokens
    [ context_window - max_response_tokens - system_prompt_reserve, 256 ].max
  end

  def max_items_per_call
    positive_budget(ENV["LLM_MAX_ITEMS_PER_CALL"], Setting.llm_max_items_per_call, 25)
  end

  def auto_categorize(transactions: [], user_categories: [], model: "", family: nil, json_mode: nil)
    with_provider_response do
      if user_categories.blank?
        family_id = family&.id || "unknown"
        Rails.logger.error("Cannot auto-categorize transactions for family #{family_id}: no categories available")
        raise Error, "No categories available for auto-categorization"
      end

      effective_model = model.presence || @default_model

      trace = create_langfuse_trace(
        name: "openai.auto_categorize",
        input: { transactions: transactions, user_categories: user_categories }
      )

      batches = slice_for_context(transactions, fixed: user_categories)

      result = batches.flat_map do |batch|
        AutoCategorizer.new(
          client,
          model: effective_model,
          transactions: batch,
          user_categories: user_categories,
          custom_provider: custom_provider?,
          langfuse_trace: trace,
          family: family,
          json_mode: json_mode
        ).auto_categorize
      end

      upsert_langfuse_trace(trace: trace, output: result.map(&:to_h))

      result
    end
  end

  def auto_detect_merchants(transactions: [], user_merchants: [], model: "", family: nil, json_mode: nil)
    with_provider_response do
      effective_model = model.presence || @default_model

      trace = create_langfuse_trace(
        name: "openai.auto_detect_merchants",
        input: { transactions: transactions, user_merchants: user_merchants }
      )

      batches = slice_for_context(transactions, fixed: user_merchants)

      result = batches.flat_map do |batch|
        AutoMerchantDetector.new(
          client,
          model: effective_model,
          transactions: batch,
          user_merchants: user_merchants,
          custom_provider: custom_provider?,
          langfuse_trace: trace,
          family: family,
          json_mode: json_mode
        ).auto_detect_merchants
      end

      upsert_langfuse_trace(trace: trace, output: result.map(&:to_h))

      result
    end
  end

  def enhance_provider_merchants(merchants: [], model: "", family: nil, json_mode: nil)
    with_provider_response do
      effective_model = model.presence || @default_model

      trace = create_langfuse_trace(
        name: "openai.enhance_provider_merchants",
        input: { merchants: merchants }
      )

      batches = slice_for_context(merchants)

      result = batches.flat_map do |batch|
        ProviderMerchantEnhancer.new(
          client,
          model: effective_model,
          merchants: batch,
          custom_provider: custom_provider?,
          langfuse_trace: trace,
          family: family,
          json_mode: json_mode
        ).enhance_merchants
      end

      upsert_langfuse_trace(trace: trace, output: result.map(&:to_h))

      result
    end
  end

  # Can be disabled via ENV for OpenAI-compatible endpoints that don't support vision
  # Only vision-capable models (gpt-4o, gpt-4-turbo, gpt-4.1, etc.) support PDF input
  def supports_pdf_processing?(model: @default_model)
    return false unless ENV.fetch("OPENAI_SUPPORTS_PDF_PROCESSING", "true").to_s.downcase.in?(%w[true 1 yes])

    # Custom providers manage their own model capabilities
    return true if custom_provider?

    # Check if the specified model supports vision/PDF input
    VISION_CAPABLE_MODEL_PREFIXES.any? { |prefix| model.start_with?(prefix) }
  end

  def process_pdf(pdf_content:, model: "", family: nil)
    with_provider_response do
      effective_model = model.presence || @default_model
      raise Error, "Model does not support PDF/vision processing: #{effective_model}" unless supports_pdf_processing?(model: effective_model)

      trace = create_langfuse_trace(
        name: "openai.process_pdf",
        input: { pdf_size: pdf_content&.bytesize }
      )

      result = PdfProcessor.new(
        client,
        model: effective_model,
        pdf_content: pdf_content,
        custom_provider: custom_provider?,
        langfuse_trace: trace,
        family: family,
        max_response_tokens: max_response_tokens
      ).process

      upsert_langfuse_trace(trace: trace, output: result.to_h)

      result
    end
  end

  def extract_bank_statement(pdf_content:, model: "", family: nil)
    with_provider_response do
      effective_model = model.presence || @default_model

      trace = create_langfuse_trace(
        name: "openai.extract_bank_statement",
        input: { pdf_size: pdf_content&.bytesize }
      )

      result = BankStatementExtractor.new(
        client: client,
        pdf_content: pdf_content,
        model: effective_model
      ).extract

      upsert_langfuse_trace(trace: trace, output: { transaction_count: result[:transactions].size })

      result
    end
  end

  def chat_response(
    prompt,
    model:,
    instructions: nil,
    functions: [],
    function_results: [],
    messages: nil,
    streamer: nil,
    previous_response_id: nil,
    session_id: nil,
    user_identifier: nil,
    family: nil
  )
    if supports_responses_endpoint?
      # Native path uses the Responses API which chains history via
      # `previous_response_id`; it does NOT need (and must not receive)
      # inline message history in the input payload.
      native_chat_response(
        prompt: prompt,
        model: model,
        instructions: instructions,
        functions: functions,
        function_results: function_results,
        streamer: streamer,
        previous_response_id: previous_response_id,
        session_id: session_id,
        user_identifier: user_identifier,
        family: family
      )
    else
      generic_chat_response(
        prompt: prompt,
        model: model,
        instructions: instructions,
        functions: functions,
        function_results: function_results,
        messages: messages,
        streamer: streamer,
        session_id: session_id,
        user_identifier: user_identifier,
        family: family
      )
    end
  end

  private
    attr_reader :client

    # Returns the first positive integer among env, setting, default. Treats
    # zero or negative values as "unset" and falls through — a 0-token budget
    # is never what the user meant.
    def positive_budget(env_value, setting_value, default)
      from_env = env_value.to_s.strip.to_i
      return from_env if from_env.positive?
      return setting_value.to_i if setting_value.to_i.positive?
      default
    end

    # Routes one-shot (non-chat) inputs through the BatchSlicer so large
    # caller batches are split to fit the model's context window. `fixed` is
    # the portion of the prompt that stays constant across every sub-batch
    # (e.g. user_categories, user_merchants), used for fixed-tokens accounting.
    def slice_for_context(items, fixed: nil)
      BatchSlicer.call(
        Array(items),
        max_items: max_items_per_call,
        max_tokens: max_input_tokens,
        fixed_tokens: fixed ? Assistant::TokenEstimator.estimate(fixed) : 0
      )
    end

    def native_chat_response(
      prompt:,
      model:,
      instructions: nil,
      functions: [],
      function_results: [],
      streamer: nil,
      previous_response_id: nil,
      session_id: nil,
      user_identifier: nil,
      family: nil
    )
      with_provider_response do
        chat_config = ChatConfig.new(
          functions: functions,
          function_results: function_results
        )

        collected_chunks = []

        # Proxy that converts raw stream to "LLM Provider concept" stream
        stream_proxy = if streamer.present?
          proc do |chunk|
            parsed_chunk = ChatStreamParser.new(chunk).parsed

            unless parsed_chunk.nil?
              streamer.call(parsed_chunk)
              collected_chunks << parsed_chunk
            end
          end
        else
          nil
        end

        input_payload = chat_config.build_input(prompt: prompt)

        begin
          raw_response = client.responses.create(parameters: {
            model: model,
            input: input_payload,
            instructions: instructions,
            tools: chat_config.tools,
            previous_response_id: previous_response_id,
            stream: stream_proxy
          })

          # If streaming, Ruby OpenAI does not return anything, so to normalize this method's API, we search
          # for the "response chunk" in the stream and return it (it is already parsed)
          if stream_proxy.present?
            response_chunk = collected_chunks.find { |chunk| chunk.type == "response" }
            response = response_chunk.data
            usage = response_chunk.usage
            Rails.logger.debug("Stream response usage: #{usage.inspect}")
            log_langfuse_generation(
              name: "chat_response",
              model: model,
              input: input_payload,
              output: response.messages.map(&:output_text).join("\n"),
              usage: usage,
              session_id: session_id,
              user_identifier: user_identifier
            )
            record_llm_usage(family: family, model: model, operation: "chat", usage: usage)
            response
          else
            parsed = ChatParser.new(raw_response).parsed
            Rails.logger.debug("Non-stream raw_response['usage']: #{raw_response['usage'].inspect}")
            log_langfuse_generation(
              name: "chat_response",
              model: model,
              input: input_payload,
              output: parsed.messages.map(&:output_text).join("\n"),
              usage: raw_response["usage"],
              session_id: session_id,
              user_identifier: user_identifier
            )
            record_llm_usage(family: family, model: model, operation: "chat", usage: raw_response["usage"])
            parsed
          end
        rescue => e
          log_langfuse_generation(
            name: "chat_response",
            model: model,
            input: input_payload,
            error: e,
            session_id: session_id,
            user_identifier: user_identifier
          )
          record_llm_usage(family: family, model: model, operation: "chat", error: e)
          raise
        end
      end
    end

    def generic_chat_response(
      prompt:,
      model:,
      instructions: nil,
      functions: [],
      function_results: [],
      messages: nil,
      streamer: nil,
      session_id: nil,
      user_identifier: nil,
      family: nil
    )
      with_provider_response do
        messages = build_generic_messages(
          prompt: prompt,
          instructions: instructions,
          function_results: function_results,
          messages: messages
        )

        tools = build_generic_tools(functions)

        # Force synchronous calls for generic chat (streaming not supported for custom providers)
        params = {
          model: model,
          messages: messages
        }
        params[:tools] = tools if tools.present?

        begin
          raw_response = client.chat(parameters: params)

          parsed = GenericChatParser.new(raw_response).parsed

          log_langfuse_generation(
            name: "chat_response",
            model: model,
            input: messages,
            output: parsed.messages.map(&:output_text).join("\n"),
            usage: raw_response["usage"],
            session_id: session_id,
            user_identifier: user_identifier
          )

          record_llm_usage(family: family, model: model, operation: "chat", usage: raw_response["usage"])

          # If a streamer was provided, manually call it with the parsed response
          # to maintain the same contract as the streaming version
          if streamer.present?
            # Emit output_text chunks for each message
            parsed.messages.each do |message|
              if message.output_text.present?
                streamer.call(Provider::LlmConcept::ChatStreamChunk.new(type: "output_text", data: message.output_text, usage: nil))
              end
            end

            # Emit response chunk
            streamer.call(Provider::LlmConcept::ChatStreamChunk.new(type: "response", data: parsed, usage: raw_response["usage"]))
          end

          parsed
        rescue => e
          log_langfuse_generation(
            name: "chat_response",
            model: model,
            input: messages,
            error: e,
            session_id: session_id,
            user_identifier: user_identifier
          )
          record_llm_usage(family: family, model: model, operation: "chat", error: e)
          raise
        end
      end
    end

    def build_generic_messages(prompt:, instructions: nil, function_results: [], messages: nil)
      payload = []

      # Add system message if instructions present
      if instructions.present?
        payload << { role: "system", content: instructions }
      end

      # Add conversation history or user prompt. History is trimmed to fit the
      # configured token budget so small-context local models (Ollama, LM Studio,
      # LocalAI) don't silently truncate. tool_call/tool_result pairs are
      # preserved atomically by HistoryTrimmer.
      if messages.present?
        trimmed = Assistant::HistoryTrimmer.new(messages, max_tokens: max_history_tokens).call
        payload.concat(trimmed)
      elsif prompt.present?
        payload << { role: "user", content: prompt }
      end

      # If there are function results, we need to add the assistant message that made the tool calls
      # followed by the tool messages with the results
      if function_results.any?
        # Build assistant message with tool_calls
        tool_calls = function_results.map do |fn_result|
          # Convert arguments to JSON string if it's not already a string
          arguments = fn_result[:arguments]
          arguments_str = arguments.is_a?(String) ? arguments : arguments.to_json

          {
            id: fn_result[:call_id],
            type: "function",
            function: {
              name: fn_result[:name],
              arguments: arguments_str
            }
          }
        end

        payload << {
          role: "assistant",
          content: "",  # Some OpenAI-compatible APIs require string, not null
          tool_calls: tool_calls
        }

        # Add function results as tool messages
        function_results.each do |fn_result|
          # Convert output to JSON string if it's not already a string
          # OpenAI API requires content to be either a string or array of objects
          # Handle nil explicitly to avoid serializing to "null"
          output = fn_result[:output]
          content = if output.nil?
            ""
          elsif output.is_a?(String)
            output
          else
            output.to_json
          end

          payload << {
            role: "tool",
            tool_call_id: fn_result[:call_id],
            name: fn_result[:name],
            content: content
          }
        end
      end

      payload
    end

    def build_generic_tools(functions)
      return [] if functions.blank?

      functions.map do |fn|
        {
          type: "function",
          function: {
            name: fn[:name],
            description: fn[:description],
            parameters: fn[:params_schema],
            strict: fn[:strict]
          }
        }
      end
    end

    def langfuse_client
      return unless ENV["LANGFUSE_PUBLIC_KEY"].present? && ENV["LANGFUSE_SECRET_KEY"].present?

      @langfuse_client = Langfuse.new
    end

    def create_langfuse_trace(name:, input:, session_id: nil, user_identifier: nil)
      return unless langfuse_client

      langfuse_client.trace(
        name: name,
        input: input,
        session_id: session_id,
        user_id: user_identifier,
        environment: Rails.env
      )
    rescue => e
      Rails.logger.warn("Langfuse trace creation failed: #{e.message}\n#{e.full_message}")
      nil
    end

    def log_langfuse_generation(name:, model:, input:, output: nil, usage: nil, error: nil, session_id: nil, user_identifier: nil)
      return unless langfuse_client

      trace = create_langfuse_trace(
        name: "openai.#{name}",
        input: input,
        session_id: session_id,
        user_identifier: user_identifier
      )

      generation = trace&.generation(
        name: name,
        model: model,
        input: input
      )

      if error
        generation&.end(
          output: { error: error.message, details: error.respond_to?(:details) ? error.details : nil },
          level: "ERROR"
        )
        upsert_langfuse_trace(
          trace: trace,
          output: { error: error.message },
          level: "ERROR"
        )
      else
        generation&.end(output: output, usage: usage)
        upsert_langfuse_trace(trace: trace, output: output)
      end
    rescue => e
      Rails.logger.warn("Langfuse logging failed: #{e.message}\n#{e.full_message}")
    end

    def upsert_langfuse_trace(trace:, output:, level: nil)
      return unless langfuse_client && trace&.id

      payload = {
        id: trace.id,
        output: output
      }
      payload[:level] = level if level.present?

      langfuse_client.trace(**payload)
    rescue => e
      Rails.logger.warn("Langfuse trace upsert failed for trace_id=#{trace&.id}: #{e.message}\n#{e.full_message}")
      nil
    end

    def record_llm_usage(family:, model:, operation:, usage: nil, error: nil)
      return unless family

      # For error cases, record with zero tokens
      if error.present?
        Rails.logger.info("Recording failed LLM usage - Error: #{safe_error_message(error)}")

        # Extract HTTP status code if available from the error
        http_status_code = extract_http_status_code(error)

        inferred_provider = LlmUsage.infer_provider(model)
        family.llm_usages.create!(
          provider: inferred_provider,
          model: model,
          operation: operation,
          prompt_tokens: 0,
          completion_tokens: 0,
          total_tokens: 0,
          estimated_cost: nil,
          metadata: {
            error: safe_error_message(error),
            http_status_code: http_status_code
          }
        )

        Rails.logger.info("Failed LLM usage recorded successfully - Status: #{http_status_code}")
        return
      end

      return unless usage

      Rails.logger.info("Recording LLM usage - Raw usage data: #{usage.inspect}")

      # Handle both old and new OpenAI API response formats
      # Old format: prompt_tokens, completion_tokens, total_tokens
      # New format: input_tokens, output_tokens, total_tokens
      prompt_tokens = usage["prompt_tokens"] || usage["input_tokens"] || 0
      completion_tokens = usage["completion_tokens"] || usage["output_tokens"] || 0
      total_tokens = usage["total_tokens"] || 0

      Rails.logger.info("Extracted tokens - prompt: #{prompt_tokens}, completion: #{completion_tokens}, total: #{total_tokens}")

      estimated_cost = LlmUsage.calculate_cost(
        model: model,
        prompt_tokens: prompt_tokens,
        completion_tokens: completion_tokens
      )

      # Log when we can't estimate the cost (e.g., custom/self-hosted models)
      if estimated_cost.nil?
        Rails.logger.info("Recording LLM usage without cost estimate for unknown model: #{model} (custom provider: #{custom_provider?})")
      end

      inferred_provider = LlmUsage.infer_provider(model)
      family.llm_usages.create!(
        provider: inferred_provider,
        model: model,
        operation: operation,
        prompt_tokens: prompt_tokens,
        completion_tokens: completion_tokens,
        total_tokens: total_tokens,
        estimated_cost: estimated_cost,
        metadata: {}
      )

      Rails.logger.info("LLM usage recorded successfully - Cost: #{estimated_cost.inspect}")
    rescue => e
      Rails.logger.error("Failed to record LLM usage: #{e.message}")
    end

    def extract_http_status_code(error)
      # Try to extract HTTP status code from various error types
      # OpenAI gem errors may have status codes in different formats
      if error.respond_to?(:code)
        error.code
      elsif error.respond_to?(:http_status)
        error.http_status
      elsif error.respond_to?(:status_code)
        error.status_code
      elsif error.respond_to?(:response) && error.response.respond_to?(:code)
        error.response.code.to_i
      elsif safe_error_message(error) =~ /(\d{3})/
        # Extract 3-digit HTTP status code from error message
        $1.to_i
      else
        nil
      end
    end

    def safe_error_message(error)
      error&.message
    rescue => e
      "(message unavailable: #{e.class})"
    end
end