1 files changed, 51 insertions, 0 deletions
diff --git a/bin/utils.ml b/bin/utils.ml
new file mode 100644
index 0000000..4f488f4
--- /dev/null
+++ b/bin/utils.ml
@@ -0,0 +1,51 @@
+open Unix
+open Lwt
+open Cohttp
+open Cohttp_lwt_unix
+
+let session_file = ".session"
+
+let year_file = ".year"
+
+let get_token () =
+  let file = In_channel.open_text session_file in
+  let token = In_channel.input_all file in
+  In_channel.close file ; String.trim token
+
+let get_year () =
+  if Caml.Sys.file_exists year_file then (
+    let file = In_channel.open_text year_file in
+    let year = In_channel.input_all file in
+    In_channel.close file ;
+    int_of_string (String.trim year) )
+  else
+    let time = time () in
+    let time = gmtime time in
+    time.tm_year + 1900
+
+let download_input day fn =
+  let year = get_year () in
+  let url =
+    Printf.sprintf "https://adventofcode.com/%d/day/%s/input" year day
+  in
+  let token = get_token () in
+  let headers = Header.init () in
+  let headers = Header.add headers "Cookie" ("session=" ^ token) in
+  let headers =
+    Header.add headers "User-Agent"
+      "github.com/fangyi-zhou/advent-of-code-ocaml-starter by \
+       me+aoc@fangyi.io"
+  in
+  let uri = Uri.of_string url in
+  let body =
+    Client.get ~headers uri
+    >>= fun (resp, body) ->
+    let code = resp |> Response.status |> Code.code_of_status in
+    if code = 200 then body |> Cohttp_lwt.Body.to_string
+    else failwith ("Unable to get data, status " ^ Int.to_string code)
+  in
+  let body = Lwt_main.run body in
+  let body = String.trim body in
+  let file = Out_channel.open_text fn in
+  Out_channel.output_string file body ;
+  Out_channel.close file