defmodule Mix.Tasks.Firebird.Target.Bench do
  @moduledoc """
  Run benchmarks comparing compiled WASM against native BEAM execution.

  ## Usage

      # Run the full benchmark suite (optimized by default)
      mix firebird.target.bench

      # Run with custom iterations
      mix firebird.target.bench --iterations 500

      # Compare unoptimized vs optimized vs BEAM side-by-side
      mix firebird.target.bench --compare

      # Run without optimizations to see raw compiler output
      mix firebird.target.bench --no-optimize --no-tco --no-inline

      # Filter benchmarks by name
      mix firebird.target.bench --filter fibonacci

      # Output as JSON / Markdown / CSV
      mix firebird.target.bench --json
      mix firebird.target.bench --markdown
      mix firebird.target.bench --csv

  ## What's Benchmarked

  The suite tests compiled WASM performance across categories:

  - **Arithmetic** - add, multiply operations
  - **Pattern matching** - abs, max with branching
  - **Light recursion** - fibonacci, factorial with small inputs
  - **Tail-recursive** - accumulator variants that benefit from TCO
  - **Deep recursion** - sum_to_acc, collatz_acc with large inputs (TCO showcase)
  - **Math operations** - gcd, power

  Each benchmark runs the function through both the WASM runtime
  (via Wasmex) and the native BEAM VM, then compares timing.

  ## Comparison Mode (--compare)

  Compiles each benchmark twice — once without optimizations and once with
  all optimizations (TCO, inlining, constant folding) — then shows a
  three-way comparison table demonstrating the concrete impact of each
  compiler optimization pass.
  """

  use Mix.Task

  @shortdoc "Benchmark WASM target vs native BEAM execution"

  @switches [
    iterations: :integer,
    warmup: :integer,
    filter: :string,
    json: :boolean,
    markdown: :boolean,
    csv: :boolean,
    verbose: :boolean,
    compare: :boolean,
    optimize: :boolean,
    tco: :boolean,
    inline: :boolean,
    licm: :boolean
  ]

  @aliases [
    n: :iterations,
    f: :filter,
    v: :verbose,
    c: :compare
  ]

  @impl Mix.Task
  def run(args) do
    {opts, _rest, _invalid} = OptionParser.parse(args, switches: @switches, aliases: @aliases)

    iterations = Keyword.get(opts, :iterations, 100)
    warmup = Keyword.get(opts, :warmup, 10)
    filter = Keyword.get(opts, :filter)
    compare_mode = Keyword.get(opts, :compare, false)

    Mix.shell().info("🔥 Firebird WASM Target — Benchmark Suite")
    Mix.shell().info("   Iterations: #{iterations}, Warmup: #{warmup}")

    if filter do
      Mix.shell().info("   Filter: #{filter}")
    end

    if compare_mode do
      Mix.shell().info("   Mode: Comparison (unoptimized vs optimized vs BEAM)")
    else
      opt_flags = []
      opt_flags = if Keyword.get(opts, :optimize, true), do: ["opt" | opt_flags], else: opt_flags
      opt_flags = if Keyword.get(opts, :tco, true), do: ["tco" | opt_flags], else: opt_flags
      opt_flags = if Keyword.get(opts, :inline, true), do: ["inline" | opt_flags], else: opt_flags
      opt_flags = if Keyword.get(opts, :licm, true), do: ["licm" | opt_flags], else: opt_flags
      Mix.shell().info("   Optimizations: #{Enum.join(Enum.reverse(opt_flags), ", ")}")
    end

    Mix.shell().info("")

    if compare_mode do
      run_comparison_mode(opts, iterations, warmup, filter)
    else
      run_standard_mode(opts, iterations, warmup, filter)
    end

    :ok
  end

  defp run_standard_mode(opts, iterations, warmup, filter) do
    results =
      Firebird.Target.Benchmark.run_suite(
        iterations: iterations,
        warmup: warmup,
        filter: filter,
        optimize: Keyword.get(opts, :optimize, true),
        tco: Keyword.get(opts, :tco, true),
        inline: Keyword.get(opts, :inline, true),
        licm: Keyword.get(opts, :licm, true)
      )

    cond do
      Keyword.get(opts, :json, false) ->
        Mix.shell().info(Firebird.Target.Benchmark.format_json(results))

      Keyword.get(opts, :markdown, false) ->
        Mix.shell().info(Firebird.Target.Benchmark.format_markdown(results))

      Keyword.get(opts, :csv, false) ->
        Mix.shell().info(Firebird.Target.Benchmark.format_csv(results))

      true ->
        Mix.shell().info(Firebird.Target.Benchmark.format_results(results))
    end

    if Keyword.get(opts, :verbose, false) do
      print_verbose(results)
    end
  end

  defp run_comparison_mode(opts, iterations, warmup, filter) do
    results =
      Firebird.Target.Benchmark.run_comparison_suite(
        iterations: iterations,
        warmup: warmup,
        filter: filter
      )

    cond do
      Keyword.get(opts, :markdown, false) ->
        Mix.shell().info(Firebird.Target.Benchmark.format_comparison_markdown(results))

      true ->
        Mix.shell().info(Firebird.Target.Benchmark.format_comparison(results))
    end

    if Keyword.get(opts, :verbose, false) do
      print_comparison_verbose(results)
    end
  end

  defp print_verbose(results) do
    Mix.shell().info("")
    Mix.shell().info("Detailed Results:")

    Enum.each(results, fn r ->
      Mix.shell().info("")
      Mix.shell().info("  #{r.name}:")

      Mix.shell().info(
        "    WASM: avg=#{Float.round(r.wasm.avg, 1)}μs min=#{r.wasm.min}μs max=#{r.wasm.max}μs p95=#{Float.round(r.wasm.p95, 1)}μs"
      )

      Mix.shell().info(
        "    BEAM: avg=#{Float.round(r.beam.avg, 1)}μs min=#{r.beam.min}μs max=#{r.beam.max}μs p95=#{Float.round(r.beam.p95, 1)}μs"
      )

      Mix.shell().info("    Speedup: #{r.speedup}x, Correct: #{r.correct}")
      Mix.shell().info("    WASM binary: #{Map.get(r, :wasm_size, 0)} bytes")
      Mix.shell().info("    Optimizations: #{Map.get(r, :optimizations, []) |> Enum.join(", ")}")
    end)
  end

  defp print_comparison_verbose(results) do
    Mix.shell().info("")
    Mix.shell().info("Detailed Comparison:")

    Enum.each(results, fn r ->
      Mix.shell().info("")
      Mix.shell().info("  #{r.name}:")

      Mix.shell().info(
        "    Raw WASM:  avg=#{Float.round(r.unoptimized.avg, 1)}μs p95=#{Float.round(r.unoptimized.p95, 1)}μs"
      )

      Mix.shell().info(
        "    Opt WASM:  avg=#{Float.round(r.optimized.avg, 1)}μs p95=#{Float.round(r.optimized.p95, 1)}μs"
      )

      Mix.shell().info(
        "    BEAM:      avg=#{Float.round(r.beam.avg, 1)}μs p95=#{Float.round(r.beam.p95, 1)}μs"
      )

      Mix.shell().info("    Opt gain:  #{r.opt_vs_raw}x faster than raw WASM")
      Mix.shell().info("    vs BEAM:   #{r.opt_vs_beam}x")

      Mix.shell().info(
        "    Size:      #{r.unopt_wasm_size}B → #{r.opt_wasm_size}B (#{r.size_reduction}B saved)"
      )
    end)
  end
end