Adds ability to create a new client

.envrc

@@ -0,0 +1 @@
+source_env_if_exists .env

.formatter.exs

@@ -0,0 +1,4 @@
+# Used by "mix format"
+[
+  inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"]
+]

.github/workflows/ci.yml

@@ -0,0 +1,48 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  test:
+    name: Build & Test
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        elixir: [1.17.1, 1.18.3]
+        otp: [25.3, 26.2, 27.0]
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: erlef/setup-beam@v1
+        with:
+          elixir-version: ${{ matrix.elixir }}
+          otp-version: ${{ matrix.otp }}
+
+      - name: Restore deps cache
+        uses: actions/cache@v4
+        with:
+          path: deps
+          key: deps-${{ runner.os }}-${{ matrix.elixir }}-${{ matrix.otp }}-${{ hashFiles('**/mix.lock') }}
+          restore-keys: deps-${{ runner.os }}-${{ matrix.elixir }}-${{ matrix.otp }}
+
+      - name: Restore build cache
+        uses: actions/cache@v4
+        with:
+          path: _build
+          key: build-${{ runner.os }}-${{ matrix.elixir }}-${{ matrix.otp }}-${{ hashFiles('**/mix.lock') }}
+          restore-keys: build-${{ runner.os }}-${{ matrix.elixir }}-${{ matrix.otp }}
+
+      - name: Install dependencies
+        run: mix deps.get
+
+      - name: Compile project
+        run: mix compile --warnings-as-errors
+
+      - name: Run tests
+        run: mix test --exclude integration

.gitignore

@@ -21,3 +21,6 @@ msg-*.tar
 
 # Temporary files, for example, from tests.
 /tmp/
+
+# Don't commit environment variables used for local testing
+.env

LICENSE

@@ -0,0 +1,22 @@
+MIT License
+
+Copyright (c) 2025 John Thornton
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+"Software"), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

README.md

@@ -0,0 +1,43 @@
+# Microsoft Graph for Elixir
+
+`msg` is an Elixir library for accessing Microsoft 365 data using the [Microsoft Graph API](https://learn.microsoft.com/en-us/graph/api/overview).
+
+This library is designed for applications that use client credentials (application-only).
+
+Documentation can be found at [https://hexdocs.com/msg](https://hexdocs.com/msg).
+
+---
+
+## Installation
+
+This package is [available in Hex](https://hex.pm/packages/msg), and can be installed by adding `msg` to your list of dependencies in `mix.exs`:
+
+```elixir
+def deps do
+  [
+    {:msg, "~> 0.1.0"}
+  ]
+end
+```
+
+## Example Usage
+
+```elixir
+creds = %{
+  client_id: System.get_env("MICROSOFT_CLIENT_ID"),
+  client_secret: System.get_env("MICROSOFT_CLIENT_SECRET"),
+  tenant_id: System.get_env("MICROSOFT_TENANT_ID")
+}
+
+client = Msg.Client.new(creds)
+{:ok, %{"value" => users}} = Msg.Users.list(client)
+```
+
+## Features
+
+* Built on top of Req for HTTP requests
+* OAuth2 client credentials flow via oauth2
+
+## License
+
+MIT License. See [LICENSE](/LICENSE) for details.

lib/msg.ex

@@ -0,0 +1,18 @@
+defmodule Msg do
+  @moduledoc """
+  Documentation for `Msg`.
+  """
+
+  @doc """
+  Hello world.
+
+  ## Examples
+
+      iex> Msg.hello()
+      :world
+
+  """
+  def hello do
+    :world
+  end
+end

lib/msg/client.ex

@@ -0,0 +1,60 @@
+defmodule Msg.Client do
+  @moduledoc """
+  Responsible for handling authentication and request setup for
+  interacting with the Microsoft Graph API using the `req` and `oauth2` libraries.
+
+  ## Example
+
+      creds = %{
+        client_id: "your-client-id",
+        client_secret: "your-client-secret",
+        tenant_id: "your-tenant-id"
+      }
+
+      client = Msg.Client.new(creds)
+      Req.get!(client, "/me")
+
+      # With custom token provider for testability
+      token_provider = fn creds -> "stub-token" end
+      client = Msg.Client.new(creds, token_provider)
+
+  ## References
+  - Microsoft Graph REST API: https://learn.microsoft.com/en-us/graph/api/overview
+  - OAuth2 client credentials: https://learn.microsoft.com/en-us/azure/active-directory/develop/v2-oauth2-client-creds-grant-flow
+  """
+
+  @type credentials :: %{
+          required(:client_id) => String.t(),
+          required(:client_secret) => String.t(),
+          required(:tenant_id) => String.t()
+        }
+
+  @type token_provider :: (credentials() -> String.t())
+
+  @spec new(credentials(), token_provider()) :: Req.Request.t()
+  def new(creds, token_provider \\ &fetch_token!/1) do
+    access_token = token_provider.(creds)
+
+    Req.new(base_url: "https://graph.microsoft.com/v1.0")
+    |> Req.Request.put_headers([
+      {"authorization", "Bearer #{access_token}"},
+      {"content-type", "application/json"},
+      {"accept", "application/json"}
+    ])
+  end
+
+  @spec fetch_token!(credentials()) :: String.t()
+  def fetch_token!(%{client_id: client_id, client_secret: client_secret, tenant_id: tenant_id}) do
+    OAuth2.Client.new(
+      client_id: client_id,
+      client_secret: client_secret,
+      site: "https://graph.microsoft.com",
+      strategy: OAuth2.Strategy.ClientCredentials,
+      token_url: "https://login.microsoftonline.com/#{tenant_id}/oauth2/v2.0/token"
+    )
+    |> OAuth2.Client.put_serializer("application/json", Jason)
+    |> OAuth2.Client.get_token!(scope: "https://graph.microsoft.com/.default")
+    |> Map.get(:token)
+    |> Map.get(:access_token)
+  end
+end

lib/msg/request.ex

@@ -0,0 +1,34 @@
+defmodule Msg.Request do
+  @moduledoc """
+  Provides helpers for performing Microsoft Graph API requests using Req.
+
+  Handles common behaviors like parsing JSON, extracting errors, and optionally
+  paginating across `@odata.nextLink`.
+  """
+
+  @type client :: Req.Request.t()
+
+  @doc """
+  Performs a simple GET request to the given Graph API path.
+
+  ## Example
+
+      Msg.Request.get(client, "/me")
+  """
+  @spec get(client(), String.t()) :: {:ok, map()} | {:error, any()}
+  def get(%Req.Request{} = client, path) do
+    client
+    |> Req.get(url: path)
+    |> handle_response()
+  end
+
+  defp handle_response({:ok, %{status: status, body: body}}) when status in 200..299 do
+    {:ok, body}
+  end
+
+  defp handle_response({:ok, %{status: status, body: body}}) do
+    {:error, %{status: status, body: body}}
+  end
+
+  defp handle_response({:error, reason}), do: {:error, reason}
+end

lib/msg/users.ex

@@ -0,0 +1,23 @@
+defmodule Msg.Users do
+  @moduledoc """
+  Provides functions for interacting with the Microsoft Graph `/users` endpoint.
+
+  ## Example
+
+      client = Msg.Client.new(creds)
+      {:ok, users} = Msg.Users.list(client)
+  """
+
+  alias Msg.Request
+
+  @doc """
+  Lists all users in the organization.
+
+  Corresponds to: [GET /users]
+  https://learn.microsoft.com/en-us/graph/api/user-list?view=graph-rest-1.0&tabs=http
+  """
+  @spec list(Req.Request.t()) :: {:ok, map()} | {:error, any()}
+  def list(client) do
+    Request.get(client, "/users")
+  end
+end

mix.exs

@@ -0,0 +1,39 @@
+defmodule Msg.MixProject do
+  use Mix.Project
+
+  @version "0.1.0"
+
+  def project do
+    [
+      app: :msg,
+      version: @version,
+      elixir: "~> 1.16",
+      start_permanent: Mix.env() == :prod,
+      deps: deps(),
+      description: "Micorosft Graph for Elixir",
+      package: [
+        licenses: ["MIT"],
+        links: %{"GitHub" => "https://github.com/riddler/msg"}
+      ]
+    ]
+  end
+
+  def application do
+    [
+      extra_applications: [:logger]
+    ]
+  end
+
+  defp deps do
+    [
+      # Testing and development
+      {:ex_doc, "~> 0.31", only: :dev, runtime: false},
+      {:mox, "~> 1.1", only: :test},
+
+      # Actual dependencies
+      {:jason, "~> 1.4"},
+      {:oauth2, "~> 2.0"},
+      {:req, "~> 0.4"}
+    ]
+  end
+end

mix.lock

@@ -0,0 +1,21 @@
+%{
+  "earmark_parser": {:hex, :earmark_parser, "1.4.44", "f20830dd6b5c77afe2b063777ddbbff09f9759396500cdbe7523efd58d7a339c", [:mix], [], "hexpm", "4778ac752b4701a5599215f7030989c989ffdc4f6df457c5f36938cc2d2a2750"},
+  "ex_doc": {:hex, :ex_doc, "0.38.1", "bae0a0bd5b5925b1caef4987e3470902d072d03347114ffe03a55dbe206dd4c2", [:mix], [{:earmark_parser, "~> 1.4.44", [hex: :earmark_parser, repo: "hexpm", optional: false]}, {:makeup_c, ">= 0.1.0", [hex: :makeup_c, repo: "hexpm", optional: true]}, {:makeup_elixir, "~> 0.14 or ~> 1.0", [hex: :makeup_elixir, repo: "hexpm", optional: false]}, {:makeup_erlang, "~> 0.1 or ~> 1.0", [hex: :makeup_erlang, repo: "hexpm", optional: false]}, {:makeup_html, ">= 0.1.0", [hex: :makeup_html, repo: "hexpm", optional: true]}], "hexpm", "754636236d191b895e1e4de2ebb504c057fe1995fdfdd92e9d75c4b05633008b"},
+  "finch": {:hex, :finch, "0.19.0", "c644641491ea854fc5c1bbaef36bfc764e3f08e7185e1f084e35e0672241b76d", [:mix], [{:mime, "~> 1.0 or ~> 2.0", [hex: :mime, repo: "hexpm", optional: false]}, {:mint, "~> 1.6.2 or ~> 1.7", [hex: :mint, repo: "hexpm", optional: false]}, {:nimble_options, "~> 0.4 or ~> 1.0", [hex: :nimble_options, repo: "hexpm", optional: false]}, {:nimble_pool, "~> 1.1", [hex: :nimble_pool, repo: "hexpm", optional: false]}, {:telemetry, "~> 0.4 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "fc5324ce209125d1e2fa0fcd2634601c52a787aff1cd33ee833664a5af4ea2b6"},
+  "hpax": {:hex, :hpax, "1.0.3", "ed67ef51ad4df91e75cc6a1494f851850c0bd98ebc0be6e81b026e765ee535aa", [:mix], [], "hexpm", "8eab6e1cfa8d5918c2ce4ba43588e894af35dbd8e91e6e55c817bca5847df34a"},
+  "jason": {:hex, :jason, "1.4.4", "b9226785a9aa77b6857ca22832cffa5d5011a667207eb2a0ad56adb5db443b8a", [:mix], [{:decimal, "~> 1.0 or ~> 2.0", [hex: :decimal, repo: "hexpm", optional: true]}], "hexpm", "c5eb0cab91f094599f94d55bc63409236a8ec69a21a67814529e8d5f6cc90b3b"},
+  "makeup": {:hex, :makeup, "1.2.1", "e90ac1c65589ef354378def3ba19d401e739ee7ee06fb47f94c687016e3713d1", [:mix], [{:nimble_parsec, "~> 1.4", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "d36484867b0bae0fea568d10131197a4c2e47056a6fbe84922bf6ba71c8d17ce"},
+  "makeup_elixir": {:hex, :makeup_elixir, "1.0.1", "e928a4f984e795e41e3abd27bfc09f51db16ab8ba1aebdba2b3a575437efafc2", [:mix], [{:makeup, "~> 1.0", [hex: :makeup, repo: "hexpm", optional: false]}, {:nimble_parsec, "~> 1.2.3 or ~> 1.3", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "7284900d412a3e5cfd97fdaed4f5ed389b8f2b4cb49efc0eb3bd10e2febf9507"},
+  "makeup_erlang": {:hex, :makeup_erlang, "1.0.2", "03e1804074b3aa64d5fad7aa64601ed0fb395337b982d9bcf04029d68d51b6a7", [:mix], [{:makeup, "~> 1.0", [hex: :makeup, repo: "hexpm", optional: false]}], "hexpm", "af33ff7ef368d5893e4a267933e7744e46ce3cf1f61e2dccf53a111ed3aa3727"},
+  "mime": {:hex, :mime, "2.0.7", "b8d739037be7cd402aee1ba0306edfdef982687ee7e9859bee6198c1e7e2f128", [:mix], [], "hexpm", "6171188e399ee16023ffc5b76ce445eb6d9672e2e241d2df6050f3c771e80ccd"},
+  "mint": {:hex, :mint, "1.7.1", "113fdb2b2f3b59e47c7955971854641c61f378549d73e829e1768de90fc1abf1", [:mix], [{:castore, "~> 0.1.0 or ~> 1.0", [hex: :castore, repo: "hexpm", optional: true]}, {:hpax, "~> 0.1.1 or ~> 0.2.0 or ~> 1.0", [hex: :hpax, repo: "hexpm", optional: false]}], "hexpm", "fceba0a4d0f24301ddee3024ae116df1c3f4bb7a563a731f45fdfeb9d39a231b"},
+  "mox": {:hex, :mox, "1.2.0", "a2cd96b4b80a3883e3100a221e8adc1b98e4c3a332a8fc434c39526babafd5b3", [:mix], [{:nimble_ownership, "~> 1.0", [hex: :nimble_ownership, repo: "hexpm", optional: false]}], "hexpm", "c7b92b3cc69ee24a7eeeaf944cd7be22013c52fcb580c1f33f50845ec821089a"},
+  "nimble_options": {:hex, :nimble_options, "1.1.1", "e3a492d54d85fc3fd7c5baf411d9d2852922f66e69476317787a7b2bb000a61b", [:mix], [], "hexpm", "821b2470ca9442c4b6984882fe9bb0389371b8ddec4d45a9504f00a66f650b44"},
+  "nimble_ownership": {:hex, :nimble_ownership, "1.0.1", "f69fae0cdd451b1614364013544e66e4f5d25f36a2056a9698b793305c5aa3a6", [:mix], [], "hexpm", "3825e461025464f519f3f3e4a1f9b68c47dc151369611629ad08b636b73bb22d"},
+  "nimble_parsec": {:hex, :nimble_parsec, "1.4.2", "8efba0122db06df95bfaa78f791344a89352ba04baedd3849593bfce4d0dc1c6", [:mix], [], "hexpm", "4b21398942dda052b403bbe1da991ccd03a053668d147d53fb8c4e0efe09c973"},
+  "nimble_pool": {:hex, :nimble_pool, "1.1.0", "bf9c29fbdcba3564a8b800d1eeb5a3c58f36e1e11d7b7fb2e084a643f645f06b", [:mix], [], "hexpm", "af2e4e6b34197db81f7aad230c1118eac993acc0dae6bc83bac0126d4ae0813a"},
+  "oauth2": {:hex, :oauth2, "2.1.0", "beb657f393814a3a7a8a15bd5e5776ecae341fd344df425342a3b6f1904c2989", [:mix], [{:tesla, "~> 1.5", [hex: :tesla, repo: "hexpm", optional: false]}], "hexpm", "8ac07f85b3307dd1acfeb0ec852f64161b22f57d0ce0c15e616a1dfc8ebe2b41"},
+  "req": {:hex, :req, "0.5.10", "a3a063eab8b7510785a467f03d30a8d95f66f5c3d9495be3474b61459c54376c", [:mix], [{:brotli, "~> 0.3.1", [hex: :brotli, repo: "hexpm", optional: true]}, {:ezstd, "~> 1.0", [hex: :ezstd, repo: "hexpm", optional: true]}, {:finch, "~> 0.17", [hex: :finch, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}, {:mime, "~> 2.0.6 or ~> 2.1", [hex: :mime, repo: "hexpm", optional: false]}, {:nimble_csv, "~> 1.0", [hex: :nimble_csv, repo: "hexpm", optional: true]}, {:plug, "~> 1.0", [hex: :plug, repo: "hexpm", optional: true]}], "hexpm", "8a604815743f8a2d3b5de0659fa3137fa4b1cffd636ecb69b30b2b9b2c2559be"},
+  "telemetry": {:hex, :telemetry, "1.3.0", "fedebbae410d715cf8e7062c96a1ef32ec22e764197f70cda73d82778d61e7a2", [:rebar3], [], "hexpm", "7015fc8919dbe63764f4b4b87a95b7c0996bd539e0d499be6ec9d7f3875b79e6"},
+  "tesla": {:hex, :tesla, "1.14.1", "71c5b031b4e089c0fbfb2b362e24b4478465773ae4ef569760a8c2899ad1e73c", [:mix], [{:castore, "~> 0.1 or ~> 1.0", [hex: :castore, repo: "hexpm", optional: true]}, {:exjsx, ">= 3.0.0", [hex: :exjsx, repo: "hexpm", optional: true]}, {:finch, "~> 0.13", [hex: :finch, repo: "hexpm", optional: true]}, {:fuse, "~> 2.4", [hex: :fuse, repo: "hexpm", optional: true]}, {:gun, ">= 1.0.0", [hex: :gun, repo: "hexpm", optional: true]}, {:hackney, "~> 1.21", [hex: :hackney, repo: "hexpm", optional: true]}, {:ibrowse, "4.4.2", [hex: :ibrowse, repo: "hexpm", optional: true]}, {:jason, ">= 1.0.0", [hex: :jason, repo: "hexpm", optional: true]}, {:mime, "~> 1.0 or ~> 2.0", [hex: :mime, repo: "hexpm", optional: false]}, {:mint, "~> 1.0", [hex: :mint, repo: "hexpm", optional: true]}, {:mox, "~> 1.0", [hex: :mox, repo: "hexpm", optional: true]}, {:msgpax, "~> 2.3", [hex: :msgpax, repo: "hexpm", optional: true]}, {:poison, ">= 1.0.0", [hex: :poison, repo: "hexpm", optional: true]}, {:telemetry, "~> 0.4 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: true]}], "hexpm", "c1dde8140a49a3bef5bb622356e77ac5a24ad0c8091f12c3b7fc1077ce797155"},
+}

test/msg/client_test.exs

@@ -0,0 +1,21 @@
+defmodule Msg.ClientTest do
+  use ExUnit.Case, async: true
+
+  @creds %{
+    client_id: "fake-client-id",
+    client_secret: "fake-client-secret",
+    tenant_id: "fake-tenant-id"
+  }
+
+  test "new/2 builds a Req client with expected headers" do
+    token_provider = fn _ -> "stub-token-123" end
+
+    client = Msg.Client.new(@creds, token_provider)
+    headers = Req.get_headers_list(client)
+
+    assert client.options.base_url == "https://graph.microsoft.com/v1.0"
+    assert {"authorization", "Bearer stub-token-123"} in headers
+    assert {"content-type", "application/json"} in headers
+    assert {"accept", "application/json"} in headers
+  end
+end

test/msg/integration/client_test.exs

@@ -0,0 +1,19 @@
+defmodule Msg.Integration.ClientTest do
+  use ExUnit.Case, async: false
+
+  alias Msg.Client
+
+  @tag :integration
+  test "creates a new client and fetches an access token" do
+    creds = %{
+      client_id: System.fetch_env!("MICROSOFT_CLIENT_ID"),
+      client_secret: System.fetch_env!("MICROSOFT_CLIENT_SECRET"),
+      tenant_id: System.fetch_env!("MICROSOFT_TENANT_ID")
+    }
+
+    # Ensure no errors are raised and token is returned
+    token = Client.fetch_token!(creds)
+    assert is_binary(token)
+    assert String.length(token) > 20
+  end
+end

test/msg_test.exs

@@ -0,0 +1,8 @@
+defmodule MsgTest do
+  use ExUnit.Case
+  doctest Msg
+
+  test "greets the world" do
+    assert Msg.hello() == :world
+  end
+end

test/test_helper.exs

@@ -0,0 +1 @@
+ExUnit.start()