fix: implement TD-02.

lib/bds/ai/http_client.ex

@@ -1,58 +1,86 @@
 defmodule BDS.AI.HttpClient do
-  @moduledoc false
+  @moduledoc """
+  Req-based HTTP client for AI endpoints.
 
+  Replaces the previous `:httpc` wrapper with explicit connect/receive
+  timeouts, TLS verification via Req's defaults, and transient retries for
+  idempotent GETs only — POSTs (chat completions) are never retried.
+
+  The response contract is unchanged: `{:ok, %{status, headers, body}}` with
+  downcased single-valued header names and the body as a raw binary (callers
+  decode JSON themselves), or `{:error, reason}` where transport failures
+  surface as plain reason atoms such as `:timeout` or `:econnrefused`.
+
+  Config (`config :bds, BDS.AI.HttpClient`):
+
+    * `:connect_timeout_ms` — TCP/TLS connect budget (default 5_000)
+    * `:receive_timeout_ms` — response budget (default 120_000; generous
+      because local LLM completions are slow)
+    * `:get_max_retries` — transient retries for GETs (default 2)
+    * `:retry_delay_ms` — constant delay between retries (default 500)
+  """
+
+  @default_connect_timeout_ms 5_000
+  @default_receive_timeout_ms 120_000
+  @default_get_max_retries 2
+  @default_retry_delay_ms 500
+
+  @spec get(String.t(), %{String.t() => String.t()}) ::
+          {:ok, %{status: non_neg_integer(), headers: map(), body: binary()}} | {:error, term()}
   def get(url, headers) when is_binary(url) and is_map(headers) do
-    request =
-      {String.to_charlist(url),
-       Enum.map(headers, fn {key, value} ->
-         {String.to_charlist(key), String.to_charlist(value)}
-       end)}
-
-    :inets.start()
-    :ssl.start()
-
-    case :httpc.request(:get, request, [], body_format: :binary) do
-      {:ok, {{_version, status, _reason}, response_headers, body}} ->
-        {:ok,
-         %{
-           status: status,
-           headers: normalize_headers(response_headers),
-           body: body
-         }}
-
-      {:error, reason} ->
-        {:error, reason}
-    end
+    [
+      method: :get,
+      url: url,
+      headers: headers,
+      retry: :transient,
+      max_retries: config(:get_max_retries, @default_get_max_retries),
+      retry_delay: fn _retry_count -> config(:retry_delay_ms, @default_retry_delay_ms) end,
+      retry_log_level: false
+    ]
+    |> Keyword.merge(base_options())
+    |> Req.request()
+    |> normalize_result()
   end
 
+  @spec post(String.t(), %{String.t() => String.t()}, binary()) ::
+          {:ok, %{status: non_neg_integer(), headers: map(), body: binary()}} | {:error, term()}
   def post(url, headers, body)
       when is_binary(url) and is_map(headers) and is_binary(body) do
-    request =
-      {String.to_charlist(url),
-       Enum.map(headers, fn {key, value} ->
-         {String.to_charlist(key), String.to_charlist(value)}
-       end), ~c"application/json", body}
-
-    :inets.start()
-    :ssl.start()
-
-    case :httpc.request(:post, request, [], body_format: :binary) do
-      {:ok, {{_version, status, _reason}, response_headers, response_body}} ->
-        {:ok,
-         %{
-           status: status,
-           headers: normalize_headers(response_headers),
-           body: response_body
-         }}
-
-      {:error, reason} ->
-        {:error, reason}
-    end
+    [
+      method: :post,
+      url: url,
+      headers: headers,
+      body: body,
+      # Completions are not idempotent; a retry could bill or generate twice.
+      retry: false
+    ]
+    |> Keyword.merge(base_options())
+    |> Req.request()
+    |> normalize_result()
   end
 
+  defp base_options do
+    [
+      connect_options: [timeout: config(:connect_timeout_ms, @default_connect_timeout_ms)],
+      receive_timeout: config(:receive_timeout_ms, @default_receive_timeout_ms),
+      # Callers parse the body themselves; keep it a raw binary.
+      decode_body: false
+    ]
+  end
+
+  defp normalize_result({:ok, %Req.Response{status: status, headers: headers, body: body}}) do
+    {:ok, %{status: status, headers: normalize_headers(headers), body: body}}
+  end
+
+  defp normalize_result({:error, %Req.TransportError{reason: reason}}), do: {:error, reason}
+  defp normalize_result({:error, reason}), do: {:error, reason}
+
+  # Req header names are already downcased; values arrive as lists.
   defp normalize_headers(headers) do
-    Enum.into(headers, %{}, fn {key, value} ->
-      {key |> to_string() |> String.downcase(), to_string(value)}
-    end)
+    Map.new(headers, fn {name, values} -> {name, Enum.join(List.wrap(values), ", ")} end)
+  end
+
+  defp config(key, default) do
+    Application.get_env(:bds, __MODULE__, []) |> Keyword.get(key, default)
   end
 end