Add flake input tracking

and restructure the whole codebase!

Not fully tested due to #4; theoretically resolves #1

lib/flake_env__watches.re

@@ -0,0 +1,48 @@
+open Core;
+open Yojson.Safe.Util;
+
+module Unix = Core_unix;
+module StringSet = Set.Make(String);
+module Util = Flake_env__util;
+
+[@deriving yojson]
+type watch = {
+  exists: bool,
+  modtime: int,
+  path: string
+};
+
+[@deriving yojson]
+type watches = array<watch>;
+
+let get = () => {
+  let direnv_watch_str = Sys.getenv("DIRENV_WATCHES") |> Option.value_exn(~message="Environment missing DIRENV_WATCHES");
+  let proc_info = Unix.create_process(~prog="direnv", ~args=["show_dump", direnv_watch_str]);
+  let sub_stdout = Unix.in_channel_of_descr(proc_info.stdout);
+
+  switch (Unix.waitpid(proc_info.pid)) {
+    | Ok() => Ok(watches_of_yojson(Yojson.Safe.from_channel(sub_stdout)))
+    | _ => Error("Failed to parse watches")
+  }
+};
+
+let get_path = (doc) => String.drop_prefix(doc |> member("path") |> to_string, 11);
+
+let rec get_paths_from_doc = (doc, paths) => {
+  let p = get_path(doc);
+  let sub_paths = List.concat(
+    doc |> member("inputs")
+        |> to_assoc
+        |> List.map(~f=((_k, v)) => get_paths_from_doc(v, paths)));
+  List.concat([[p], sub_paths])
+};
+
+let get_input_paths = () => {
+  switch (Util.nix(["flake", "archive", "--json", "--no-write-lock-file"])) {
+  | (Ok(), output) => get_paths_from_doc(Yojson.Safe.from_string(output), [])
+  | (Error(_), _) => {
+      Printf.eprintf("Failed to parse output of `nix flake archive --json`. Ignorning flake inputs. \n");
+      []
+    }
+  }
+};