defmodule RodarRelease do
  @moduledoc """
  Version management and release utilities.

  The version lives directly in `mix.exs` as the single source of truth.
  At release time, `mix rodar_release.patch|minor|major` bumps it, updates
  CHANGELOG.md, commits, and tags.

  ## Semantic Versioning

  Versions follow [Semantic Versioning](https://semver.org) (`MAJOR.MINOR.PATCH`):

    * `:patch` — backward-compatible bug fixes
    * `:minor` — new functionality, backward-compatible
    * `:major` — breaking changes

  Pre-release and build metadata (e.g. `1.0.0-rc.1`) are not currently supported.

  ## Releasing

      mix rodar_release.patch              # bug fix
      mix rodar_release.minor              # new feature
      mix rodar_release.major              # breaking change
      mix rodar_release.patch --dry-run    # preview

  ## Rollback & Amend

      mix rodar_release.rollback           # undo last release (soft reset)
      mix rodar_release.rollback --hard    # undo and discard changes
      mix rodar_release.amend              # fold changes into release commit

  Run `mix help rodar_release` for the full list of commands.
  """

  @version_pattern ~r/version:\s*"(\d+\.\d+\.\d+)"/

  @doc """
  Reads the current version from a mix.exs file.

  ## Options

    * `:file` - path to mix.exs (default: `"mix.exs"`)

  ## Examples

      iex> File.write!("test_mix.exs", ~s|version: "1.2.3"|)
      iex> RodarRelease.read_version(file: "test_mix.exs")
      "1.2.3"
      iex> File.rm!("test_mix.exs")

  """
  def read_version(opts \\ []) do
    file = Keyword.get(opts, :file, "mix.exs")

    content =
      case File.read(file) do
        {:ok, c} -> c
        {:error, _} -> raise "Could not read #{file}"
      end

    case Regex.run(@version_pattern, content) do
      [_, version] -> version
      nil -> raise "Could not find version in #{file}. Expected `version: \"x.y.z\"`."
    end
  end

  @doc """
  Writes a new version into a mix.exs file, replacing the existing version string.

  ## Options

    * `:file` - path to mix.exs (default: `"mix.exs"`)

  """
  def write_version(new_version, opts \\ []) do
    file = Keyword.get(opts, :file, "mix.exs")

    content =
      case File.read(file) do
        {:ok, c} -> c
        {:error, _} -> raise "Could not read #{file}"
      end

    updated =
      Regex.replace(@version_pattern, content, ~s|version: "#{new_version}"|, global: false)

    File.write!(file, updated)
  end

  @doc """
  Bumps a version string by the given segment.

  ## Examples

      iex> RodarRelease.bump("1.0.8", :patch)
      "1.0.9"

      iex> RodarRelease.bump("1.0.8", :minor)
      "1.1.0"

      iex> RodarRelease.bump("1.0.8", :major)
      "2.0.0"

  """
  def bump(version, segment) when segment in [:patch, :minor, :major] do
    [major, minor, patch] =
      version
      |> String.split(".")
      |> Enum.map(&String.to_integer/1)

    case segment do
      :patch -> "#{major}.#{minor}.#{patch + 1}"
      :minor -> "#{major}.#{minor + 1}.0"
      :major -> "#{major + 1}.0.0"
    end
  end
end