ex_harness

defmodule Mix.Tasks.Harness.Init do
  @shortdoc "Full-codebase audit via dialyzer + reach"

  @moduledoc """
  #{@shortdoc}

  Runs `mix dialyzer --format short` and `Reach.Project` taint /
  dead-code analysis against the host project, then writes a Markdown
  audit report to `.harness/audit-<timestamp>.md` plus a `latest.md`
  copy and a `latest.json` machine-readable dump.

  ## Examples

      mix harness.init
      mix harness.init --skip dialyzer
      mix harness.init --quick

  ## Options

    * `--root DIR`  — project root to analyze (default: cwd)
    * `--skip LIST` — comma-separated runners to skip (`dialyzer`, `reach`)
    * `--quick`     — skip the `mix dialyzer --plt` rebuild step

  Always exits 0 — the report is the deliverable. CI gating with
  thresholds is intentionally a separate task (`harness.init.ci`,
  planned for v0.2).
  """

  use Mix.Task

  alias ExHarness.Audit
  alias ExHarness.DialyzerRunner
  alias ExHarness.ReachRunner

  @impl Mix.Task
  def run(argv) do
    {opts, _, _} =
      OptionParser.parse(argv,
        strict: [root: :string, skip: :string, quick: :boolean]
      )

    root = Path.expand(opts[:root] || File.cwd!())

    skip =
      (opts[:skip] || "")
      |> String.split(",", trim: true)
      |> Enum.map(&String.trim/1)
      |> MapSet.new()

    File.mkdir_p!(Path.join(root, ".harness"))

    Mix.shell().info("ex_harness: dialyzer + reach audit on #{root}")

    dialyzer =
      if MapSet.member?(skip, "dialyzer") do
        Mix.shell().info("  - dialyzer skipped")
        nil
      else
        Mix.shell().info("  - dialyzer running…")
        DialyzerRunner.run(root, quick: opts[:quick] == true)
      end

    reach =
      if MapSet.member?(skip, "reach") do
        Mix.shell().info("  - reach skipped")
        nil
      else
        Mix.shell().info("  - reach running…")
        ReachRunner.run(root)
      end

    metadata = build_metadata(root)
    md = Audit.render(metadata, dialyzer, reach)
    json = Audit.to_json(metadata, dialyzer, reach)

    stamp = stamp(metadata.timestamp)
    timestamped = Path.join(root, ".harness/audit-#{stamp}.md")
    latest_md = Path.join(root, ".harness/latest.md")
    latest_json = Path.join(root, ".harness/latest.json")

    File.write!(timestamped, md)
    File.write!(latest_md, md)
    File.write!(latest_json, encode_json(json))

    Mix.shell().info("\nReport: #{timestamped}")
    Mix.shell().info("        #{latest_md}")
    Mix.shell().info("        #{latest_json}")
    print_summary(dialyzer, reach)
    :ok
  end

  defp build_metadata(root) do
    %{
      root: root,
      timestamp: DateTime.utc_now(),
      elixir: System.version(),
      otp: :erlang.system_info(:otp_release) |> List.to_string(),
      lock_digest: lock_digest(root)
    }
  end

  defp lock_digest(root) do
    path = Path.join(root, "mix.lock")

    case File.read(path) do
      {:ok, contents} ->
        :crypto.hash(:sha256, contents) |> Base.encode16(case: :lower) |> binary_part(0, 12)

      _ ->
        nil
    end
  end

  defp stamp(%DateTime{} = dt) do
    dt
    |> DateTime.to_iso8601(:basic)
    |> String.replace(~r/[^0-9TZ]/, "")
  end

  defp encode_json(map) do
    if Code.ensure_loaded?(Jason) do
      Jason.encode!(map, pretty: true)
    else
      inspect(map, pretty: true, limit: :infinity, printable_limit: :infinity)
    end
  end

  defp print_summary(dialyzer, reach) do
    Mix.shell().info("")
    Mix.shell().info("Summary:")

    if dialyzer do
      Mix.shell().info("  dialyzer findings: #{length(dialyzer.findings)}")
    end

    if reach do
      Mix.shell().info(
        "  reach: #{reach.scope.modules} modules, " <>
          "#{length(reach.taints)} taints, " <>
          "#{length(reach.dead_code)} dead-code candidates"
      )
    end
  end
end