defmodule MoundHunters.TileProcessor do
  @moduledoc """
  GenServer that processes tile requests: lookup tile IDs and download/convert tiles.
  
  Processing pipeline:
  1. :looking_up - Query ArcGIS for tile metadata
  2. :downloading - Download ZIP from OGRIP
  3. :extracting - Unzip the archive
  4. :converting - Run las2mound.py to create .mound file
  5. :done - Files ready in priv/tiles/
  """
  use GenServer
  require Logger

  alias MoundHunters.OhioLidar

  # Processing statuses
  @type lookup_status :: :pending | {:ok, String.t()} | {:error, String.t()}
  @type processing_status ::
          :queued | :downloading | :extracting | :converting | :done | {:error, String.t()}

  # Client API

  def start_link(opts) do
    GenServer.start_link(__MODULE__, opts, name: __MODULE__)
  end

  @doc """
  Request processing for a lat/lng coordinate pair.
  Returns the lookup_id that can be used to poll progress.
  """
  def request_tile(lat, lng) do
    lookup_id = MoundHunters.Boundary.format_lookup_id(lat, lng)
    GenServer.cast(__MODULE__, {:request_tile, lookup_id, lat, lng})
    {:ok, lookup_id}
  end

  @doc """
  Get the current lookup status for a coordinate pair.
  """
  def get_lookup_status(lookup_id) do
    case :ets.lookup(:tile_lookups, lookup_id) do
      [{^lookup_id, status}] -> {:ok, status}
      [] -> {:error, :not_found}
    end
  end

  @doc """
  Get the current processing status for a tile.
  """
  def get_processing_status(tile_id) do
    case :ets.lookup(:tile_processing, tile_id) do
      [{^tile_id, status, _metadata}] -> {:ok, status}
      [] -> {:error, :not_found}
    end
  end

  @doc """
  Get full metadata for a processing tile.
  """
  def get_processing_metadata(tile_id) do
    case :ets.lookup(:tile_processing, tile_id) do
      [{^tile_id, status, metadata}] -> {:ok, status, metadata}
      [] -> {:error, :not_found}
    end
  end

  # Server callbacks

  @impl true
  def init(_opts) do
    # Create ETS tables
    :ets.new(:tile_lookups, [:set, :public, :named_table])
    :ets.new(:tile_processing, [:set, :public, :named_table])

    # Ensure temp directory exists
    temp_dir = Application.get_env(:mound_hunters, :tile_temp_dir)
    File.mkdir_p!(temp_dir)

    state = %{
      las2mound_script: Application.get_env(:mound_hunters, :las2mound_script_path),
      tile_output_dir: Application.get_env(:mound_hunters, :tile_output_dir),
      tile_temp_dir: temp_dir,
      processing_queue: :queue.new(),
      current_job: nil
    }

    Logger.info("TileProcessor started")
    {:ok, state}
  end

  @impl true
  def handle_cast({:request_tile, lookup_id, lat, lng}, state) do
    # Check if we already have this lookup in progress or completed
    case :ets.lookup(:tile_lookups, lookup_id) do
      [] ->
        # New request - insert as pending and start lookup
        :ets.insert(:tile_lookups, {lookup_id, :pending})
        Logger.info("New tile request for #{lookup_id} (#{lat}, #{lng})")

        # Start lookup asynchronously
        send(self(), {:lookup_tile, lookup_id, lat, lng})

      [{^lookup_id, _status}] ->
        # Already in progress or completed, ignore duplicate request
        Logger.debug("Duplicate tile request for #{lookup_id}, ignoring")
    end

    {:noreply, state}
  end

  @impl true
  def handle_info({:lookup_tile, lookup_id, lat, lng}, state) do
    Logger.info("Looking up tile for coordinates (#{lat}, #{lng})")

    case OhioLidar.query_tile_info(lng, lat) do
      {:ok, tile_info} ->
        tile_name = tile_info.tile_name
        Logger.info("Found tile: #{tile_name} in #{tile_info.county} county")

        # Update lookup table with success
        :ets.insert(:tile_lookups, {lookup_id, {:ok, tile_name}})

        # Check if tile already exists
        output_file = Path.join(state.tile_output_dir, "#{tile_name}.mound")

        if File.exists?(output_file) do
          Logger.info("Tile #{tile_name} already processed, marking as done")
          :ets.insert(:tile_processing, {tile_name, :done, %{tile_info: tile_info}})
        else
          # Queue for processing
          state = queue_tile_for_processing(state, tile_name, tile_info)
          {:noreply, state}
        end

      {:error, :no_tile_found} ->
        Logger.warning("No tile found for coordinates (#{lat}, #{lng})")
        :ets.insert(:tile_lookups, {lookup_id, {:error, "No tile found at coordinates"}})
        {:noreply, state}

      {:error, reason} ->
        Logger.error("Failed to lookup tile: #{inspect(reason)}")
        :ets.insert(:tile_lookups, {lookup_id, {:error, "Lookup failed: #{inspect(reason)}"}})
        {:noreply, state}
    end
  end

  @impl true
  def handle_info({:process_tile, tile_name, tile_info}, state) do
    Logger.info("Starting processing for tile #{tile_name}")

    # Update status to downloading
    :ets.insert(:tile_processing, {tile_name, :downloading, %{tile_info: tile_info}})

    # Download ZIP
    temp_zip = Path.join(state.tile_temp_dir, "#{tile_name}.zip")

    case OhioLidar.download_tile(tile_name, tile_info.county, temp_zip) do
      {:ok, _bytes} ->
        send(self(), {:extract_tile, tile_name, tile_info, temp_zip})
        {:noreply, state}

      {:error, reason} ->
        Logger.error("Failed to download tile #{tile_name}: #{inspect(reason)}")
        :ets.insert(:tile_processing, {tile_name, {:error, "Download failed: #{inspect(reason)}"}, %{}})
        
        # Clean up
        File.rm(temp_zip)
        
        # Process next in queue
        state = process_next_in_queue(state)
        {:noreply, state}
    end
  end

  @impl true
  def handle_info({:extract_tile, tile_name, tile_info, zip_path}, state) do
    Logger.info("Extracting tile #{tile_name}")
    :ets.insert(:tile_processing, {tile_name, :extracting, %{tile_info: tile_info}})

    extract_dir = Path.join(state.tile_temp_dir, tile_name)
    File.mkdir_p!(extract_dir)

    case unzip_file(zip_path, extract_dir) do
      :ok ->
        # Find the .las file
        case find_las_file(extract_dir) do
          {:ok, las_file} ->
            send(self(), {:convert_tile, tile_name, tile_info, las_file, extract_dir})
            {:noreply, state}

          {:error, reason} ->
            Logger.error("Failed to find LAS file in #{extract_dir}: #{reason}")
            :ets.insert(:tile_processing, {tile_name, {:error, "No LAS file found"}, %{}})
            
            # Clean up
            File.rm_rf!(extract_dir)
            File.rm(zip_path)
            
            state = process_next_in_queue(state)
            {:noreply, state}
        end

      {:error, reason} ->
        Logger.error("Failed to extract #{zip_path}: #{inspect(reason)}")
        :ets.insert(:tile_processing, {tile_name, {:error, "Extraction failed: #{inspect(reason)}"}, %{}})
        
        # Clean up
        File.rm_rf!(extract_dir)
        File.rm(zip_path)
        
        state = process_next_in_queue(state)
        {:noreply, state}
    end
  end

  @impl true
  def handle_info({:convert_tile, tile_name, tile_info, las_file, temp_dir}, state) do
    Logger.info("Converting tile #{tile_name} to mound format")
    :ets.insert(:tile_processing, {tile_name, :converting, %{tile_info: tile_info}})

    output_file = Path.join(state.tile_output_dir, "#{tile_name}.mound")
    File.mkdir_p!(state.tile_output_dir)

    case run_las2mound(state.las2mound_script, las_file, output_file) do
      :ok ->
        Logger.info("Successfully converted #{tile_name}")
        :ets.insert(:tile_processing, {tile_name, :done, %{tile_info: tile_info}})

        # Update Mnesia
        MoundHunters.Repo.upsert_tile(%{
          id: tile_name,
          status: :ready,
          min_lat: nil,  # TODO: Extract from tile_info or LAS bounds
          max_lat: nil,
          min_lng: nil,
          max_lng: nil
        })

        # Clean up temp files
        File.rm_rf!(temp_dir)
        File.rm(Path.join(state.tile_temp_dir, "#{tile_name}.zip"))

        state = process_next_in_queue(state)
        {:noreply, state}

      {:error, reason} ->
        Logger.error("Failed to convert #{tile_name}: #{inspect(reason)}")
        :ets.insert(:tile_processing, {tile_name, {:error, "Conversion failed: #{inspect(reason)}"}, %{}})

        # Clean up
        File.rm_rf!(temp_dir)
        File.rm(Path.join(state.tile_temp_dir, "#{tile_name}.zip"))

        state = process_next_in_queue(state)
        {:noreply, state}
    end
  end

  # Helper functions

  defp queue_tile_for_processing(state, tile_name, tile_info) do
    # Check if already in queue or processing
    case :ets.lookup(:tile_processing, tile_name) do
      [] ->
        # Add to queue
        :ets.insert(:tile_processing, {tile_name, :queued, %{tile_info: tile_info}})
        new_queue = :queue.in({tile_name, tile_info}, state.processing_queue)
        state = %{state | processing_queue: new_queue}

        # If nothing currently processing, start now
        if state.current_job == nil do
          process_next_in_queue(state)
        else
          state
        end

      [{^tile_name, _status, _metadata}] ->
        Logger.debug("Tile #{tile_name} already in processing queue")
        state
    end
  end

  defp process_next_in_queue(state) do
    case :queue.out(state.processing_queue) do
      {{:value, {tile_name, tile_info}}, new_queue} ->
        Logger.info("Processing next tile in queue: #{tile_name}")
        send(self(), {:process_tile, tile_name, tile_info})
        %{state | processing_queue: new_queue, current_job: tile_name}

      {:empty, _} ->
        Logger.debug("Processing queue empty")
        %{state | current_job: nil}
    end
  end

  defp unzip_file(zip_path, extract_dir) do
    case :zip.unzip(String.to_charlist(zip_path), cwd: String.to_charlist(extract_dir)) do
      {:ok, _files} ->
        :ok

      {:error, reason} ->
        {:error, reason}
    end
  end

  defp find_las_file(dir) do
    case File.ls(dir) do
      {:ok, files} ->
        las_files = Enum.filter(files, &String.ends_with?(&1, ".las"))

        case las_files do
          [las_file | _] -> {:ok, Path.join(dir, las_file)}
          [] -> {:error, :no_las_file}
        end

      {:error, reason} ->
        {:error, reason}
    end
  end

  defp run_las2mound(script_path, input_las, output_mound) do
    Logger.info("Running: #{script_path} #{input_las} #{output_mound}")

    case System.cmd("python3", [script_path, input_las, output_mound], stderr_to_stdout: true) do
      {output, 0} ->
        Logger.debug("las2mound output: #{output}")
        :ok

      {output, exit_code} ->
        Logger.error("las2mound failed with exit code #{exit_code}: #{output}")
        {:error, "Exit code #{exit_code}"}
    end
  end
end