[wip] static file cache data structure works

src/fd_sfc_cache.erl

@@ -0,0 +1,68 @@
+% @doc
+% cache data management
+-module(fd_sfc_cache).
+
+-export_type([
+    cache/0
+]).
+
+-export([
+    new/0, new/1
+]).
+
+-include("$zx_include/zx_logger.hrl").
+
+-type cache() :: #{HttpPath :: binary() := Entry :: fd_sfc_entry:entry()}.
+
+
+-spec new() -> cache().
+new() -> #{}.
+
+
+-spec new(BasePath) -> cache()
+    when BasePath :: file:filename().
+% @doc
+% if you give a file path it just takes the parent dir
+%
+% recursively crawls through file tree and picks
+%
+% IO errors will be logged but will result in cache misses
+
+new(BasePath) ->
+    case filelib:is_file(BasePath) of
+        true  -> new2(BasePath);
+        false ->
+            tell("~p:new(~p): no such file or directory, returning empty cache", [?MODULE, BasePath]),
+            #{}
+    end.
+
+new2(BasePath) ->
+    BaseDir =
+        case filelib:is_dir(BasePath) of
+            true  -> filename:absname(BasePath);
+            false -> filename:absname(filename:dirname(BasePath))
+        end,
+    %% hacky, fuck you
+    RemovePrefix =
+        fun (Prefix, Size, From) ->
+            <<Prefix:Size/bytes, Rest/bytes>> = From,
+            Rest
+        end,
+    BBaseDir = unicode:characters_to_binary(BaseDir),
+    BBS      = byte_size(BBaseDir),
+    HandlePath =
+        fun(AbsPath, AccCache) ->
+            BAbsPath = unicode:characters_to_binary(AbsPath),
+            HttpPath = RemovePrefix(BBaseDir, BBS, BAbsPath),
+            NewCache =
+                case fd_sfc_entry:new(AbsPath) of
+                    {found, Entry} -> maps:put(HttpPath, Entry, AccCache);
+                    not_found      -> AccCache
+                end,
+            NewCache
+        end,
+    filelib:fold_files(_dir       = BaseDir,
+                       _match     = ".+",
+                       _recursive = true,
+                       _fun       = HandlePath,
+                       _init_acc  = #{}).