defmodule Mix.Tasks.ImportContestLogs do
  @shortdoc "Import ARRL contest CSV files with deduplication"
  @moduledoc """
  Imports one or more contest CSV files, deduplicating both across files
  and against existing contacts in the database.

  Uses the same direction-agnostic, 60-minute-window dedup logic as the
  web CSV uploader.

      mix import_contest_logs ~/Downloads/arrl_10ghz_2024.csv ~/Downloads/arrl_10ghz_2023.csv ...
      mix import_contest_logs ~/Downloads/arrl_10ghz_*.csv
  """
  use Mix.Task

  alias Microwaveprop.Radio.CsvImport

  @impl Mix.Task
  def run(argv) do
    if argv == [] do
      Mix.raise("Usage: mix import_contest_logs FILE [FILE ...]")
    end

    Mix.Task.run("app.start")
    _ = Oban.pause_all_queues(Oban)

    # Concatenate all CSVs into one string (skip headers after the first file)
    combined =
      argv
      |> Enum.with_index()
      |> Enum.map(fn {path, idx} ->
        expanded = Path.expand(path)
        content = File.read!(expanded)
        lines = String.split(content, ~r/\r?\n/)

        # Skip header for all files after the first
        data_lines = if idx == 0, do: lines, else: tl(lines)

        # Drop blank trailing lines
        Enum.reject(data_lines, &(String.trim(&1) == ""))
      end)
      |> List.flatten()
      |> Enum.join("\n")

    total_lines = combined |> String.split("\n") |> length() |> Kernel.-(1)
    Mix.shell().info("Combined #{length(argv)} files: #{total_lines} data rows")

    Mix.shell().info("Running preview (validate + deduplicate)...")

    case CsvImport.preview(combined, "contest-import@ntms.org") do
      {:ok, preview} ->
        print_preview_summary(preview)
        print_invalid_rows(preview.invalid)

        if preview.valid == [] do
          Mix.shell().info("Nothing to import.")
        else
          import_batches(preview.valid)
        end

      {:error, reason} ->
        Mix.raise("Failed: #{inspect(reason)}")
    end
  end

  defp print_preview_summary(preview) do
    Mix.shell().info("""
    Preview:
      Valid:      #{length(preview.valid)}
      Duplicates: #{length(preview.duplicates)}
      Invalid:    #{length(preview.invalid)}
    """)
  end

  defp print_invalid_rows([]), do: :ok

  defp print_invalid_rows(invalid) do
    invalid
    |> Enum.take(10)
    |> Enum.each(fn row ->
      Mix.shell().info("  Row #{row.row_num}: #{Enum.join(row.messages, ", ")}")
    end)

    if length(invalid) > 10 do
      Mix.shell().info("  ... and #{length(invalid) - 10} more")
    end
  end

  defp import_batches(valid) do
    Mix.shell().info("Importing #{length(valid)} contacts...")

    {imported, errors} =
      valid
      |> Enum.chunk_every(500)
      |> Enum.with_index(1)
      |> Enum.reduce({0, 0}, fn {batch, batch_num}, {imported, errors} ->
        {:ok, result} = CsvImport.commit(batch)
        new_imported = imported + length(result.imported)
        new_errors = errors + length(result.errors)

        Mix.shell().info(
          "  Batch #{batch_num}: +#{length(result.imported)} imported, #{length(result.errors)} errors (total: #{new_imported})"
        )

        {new_imported, new_errors}
      end)

    Mix.shell().info("Done! Imported #{imported} contacts, #{errors} errors.")
  end
end