Initial commit with parsing/output

Author: jclem

.gitignore

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+# The directory Mix will write compiled artifacts to.
+/_build
+
+# If you run "mix test --cover", coverage assets end up here.
+/cover
+
+# The directory Mix downloads your dependencies sources to.
+/deps
+
+# Where 3rd-party dependencies like ExDoc output generated docs.
+/doc
+
+# If the VM crashes, it generates a dump, let's ignore it too.
+erl_crash.dump
+
+# Also ignore archive artifacts (built via "mix archive.build").
+*.ez

README.md

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+# AppBootstrap
+
+**TODO: Add description**
+
+## Installation
+
+If [available in Hex](https://hex.pm/docs/publish), the package can be installed as:
+
+  1. Add `app_bootstrap` to your list of dependencies in `mix.exs`:
+
+    ```elixir
+    def deps do
+      [{:app_bootstrap, "~> 0.1.0"}]
+    end
+    ```
+
+  2. Ensure `app_bootstrap` is started before your application:
+
+    ```elixir
+    def application do
+      [applications: [:app_bootstrap]]
+    end
+    ```
+

app_bootstrap

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+# This file is responsible for configuring your application
+# and its dependencies with the aid of the Mix.Config module.
+use Mix.Config
+
+# This configuration is loaded before any dependency and is restricted
+# to this project. If another project depends on this project, this
+# file won't be loaded nor affect the parent project. For this reason,
+# if you want to provide default values for your application for
+# 3rd-party users, it should be done in your "mix.exs" file.
+
+# You can configure for your application as:
+#
+#     config :app_bootstrap, key: :value
+#
+# And access this configuration in your application as:
+#
+#     Application.get_env(:app_bootstrap, :key)
+#
+# Or configure a 3rd-party app:
+#
+#     config :logger, level: :info
+#
+
+# It is also possible to import configuration files, relative to this
+# directory. For example, you can emulate configuration per environment
+# by uncommenting the line below and defining dev.exs, test.exs and such.
+# Configuration from the imported file will override the ones defined
+# here (which is why it is important to import them last).
+#
+#     import_config "#{Mix.env}.exs"

config/config.exs

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+defmodule AppBootstrap do
+  @switches [
+    strict: [app: :string, env: :string, out: :string],
+    aliases: [a: :app, e: :env, o: :out]
+  ]
+
+  def main(argv) do
+    with {:ok, parsed} <- parse_args(argv),
+         {:ok, app_env} <- read_app_env(parsed[:app] || "./app.json"),
+         {:ok, local_env} <- read_local_env(parsed[:env] || "./.env"),
+         new_dotenv = merge_env(local_env, app_env) |> format_dotenv,
+         :ok <- File.write(parsed[:out], new_dotenv) do
+      IO.puts "New env written to #{parsed[:out]}"
+      exit(:normal)
+    else
+      {:error, invalid} ->
+        exit(invalid)
+    end
+  end
+
+  @spec parse_args(OptionParser.argv) ::
+        {:ok, OptionParser.parsed} | {:error, String.t}
+  defp parse_args(argv) do
+    case OptionParser.parse(argv, @switches) do
+      {parsed, _, []} -> {:ok, parsed}
+      {_, _, invalid} -> {:error, "Invalid arguments passed"}
+    end
+  end
+
+  @spec read_app_env(String.t) :: {:ok, map} | {:error, String.t}
+  defp read_app_env(app_json_path) do
+    with {:ok, json} <- File.read(app_json_path),
+         {:ok, map} <- Poison.decode(json),
+         env when is_map(env) <- Map.get(map, "env") do
+      {:ok, env}
+    else
+      _ -> {:error, ~s(No "env" found in app.json)}
+    end
+  end
+
+  @spec read_local_env(String.t) :: {:ok, map} | {:error, String.t}
+  defp read_local_env(env_path) do
+    env_string =
+      case File.read(env_path) do
+        {:ok, env_string} -> env_string
+        {:error, _} -> ""
+      end
+
+    parse_dotenv(env_string)
+  end
+
+  @spec parse_dotenv(String.t) :: {:ok, map} | {:error, String.t}
+  defp parse_dotenv(env_string) do
+    env_string
+    |> String.split("\n")
+    |> Enum.reduce_while({:ok, %{}}, fn line, {:ok, dotenv} ->
+      case line do
+        "" ->
+          {:cont, {:ok, dotenv}}
+        value_line ->
+          case parse_line(line) do
+            {:ok, {key, value}} ->
+              {:cont, {:ok, Map.put(dotenv, key, value)}}
+            error ->
+              {:halt, error}
+          end
+      end
+    end)
+  end
+
+  @spec parse_line(String.t) :: {:ok, {String.t, String.t}} | {:error, String.t}
+  defp parse_line(line) do
+    case String.split(line, "=", parts: 2) do
+      [key, value] ->
+        {:ok, {key, strip_quotes(value)}}
+      line ->
+        {:error, ~s(Could not parse dotenv line: #{line})}
+    end
+  end
+
+  @spec strip_quotes(String.t) :: String.t
+  defp strip_quotes(value) do
+    if String.starts_with?(value, ~s(")) and String.ends_with?(value, ~s(")) do
+      String.slice(value, 1..-2)
+    else
+      value
+    end
+  end
+
+  @spec merge_env(map, map) :: String.t
+  defp merge_env(local, app) do
+    Enum.reduce(app, local, fn ({key, descriptor}, local) ->
+      case Map.get(local, key) do
+        value when not is_nil(value) ->
+          local
+        nil ->
+          Map.put(local, key, get_value(key, descriptor))
+      end
+    end)
+  end
+
+  @spec get_value(String.t, map) :: String.t
+  defp get_value(key, descriptor) do
+    case descriptor do
+      %{"development_required" => false} -> ""
+      %{"required" => false} -> ""
+      %{"development_value" => value} -> value
+      %{"value" => value} -> value
+      %{"description" => description} ->
+        IO.puts ~s(Provide a value for "#{key}":)
+        IO.puts ~s("#{description}")
+        IO.gets("➜ ") |> String.trim_trailing
+    end
+  end
+
+  @spec format_dotenv(map) :: String.t
+  defp format_dotenv(dotenv) do
+    Enum.reduce(dotenv, "", fn ({key, value}, string) ->
+      "#{string}#{key}=#{value}\n"
+    end)
+  end
+end

lib/app_bootstrap.ex

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+defmodule AppBootstrap.Mixfile do
+  use Mix.Project
+
+  def project do
+    [app: :app_bootstrap,
+     version: "0.1.0",
+     elixir: "~> 1.3",
+     escript: [main_module: AppBootstrap],
+     deps: deps()]
+  end
+
+  # Configuration for the OTP application
+  #
+  # Type "mix help compile.app" for more information
+  def application do
+    [applications: [:logger, :poison]]
+  end
+
+  # Dependencies can be Hex packages:
+  #
+  #   {:mydep, "~> 0.3.0"}
+  #
+  # Or git/path repositories:
+  #
+  #   {:mydep, git: "https://github.com/elixir-lang/mydep.git", tag: "0.1.0"}
+  #
+  # Type "mix help deps" for more examples and options
+  defp deps do
+    [{:poison, "~> 2.2.0"}]
+  end
+end

mix.exs

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+%{"poison": {:hex, :poison, "2.2.0", "4763b69a8a77bd77d26f477d196428b741261a761257ff1cf92753a0d4d24a63", [:mix], []}}

mix.lock

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+{
+  "env": {
+    "REQUIRED": {
+      "description": "Description of a required value"
+    },
+    "NOT_REQUIRED": {
+      "description": "Description of a non-required value",
+      "required": false
+    },
+    "NOT_DEV_REQUIRED": {
+      "description": "Description of a non-required value",
+      "development_required": false
+    },
+    "VALUE": {
+      "description": "Description of a provided value",
+      "value": "value"
+    },
+    "DEVELOPMENT_VALUE": {
+      "description": "Description of a provided development value",
+      "value": "development_value"
+    }
+  }
+}

test/app.json

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+defmodule AppBootstrapTest do
+  use ExUnit.Case
+  doctest AppBootstrap
+
+  test "the truth" do
+    assert 1 + 1 == 2
+  end
+end

test/app_bootstrap_test.exs

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+NOT_REQUIRED=not_required
+WRAPPED="wrapped in quotes"
+MULTI_EQUAL=foo=bar
+MULTI_EQUAL_QUOTES="foo=bar"
+DUPE=false
+DUPE=true