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#!/usr/bin/env escript
%% -*- erlang-indent-level: 4;indent-tabs-mode: nil -*-
%%! -smp enable
%%% ---------------------------------------------------------------------------
%%% @doc
%%% The purpose of this command is to prepare a mix project so that mix
%%% understands that the dependencies are all already installed. If you want a
%%% hygienic build on nix then you must run this command before running mix. I
%%% suggest that you add a `Makefile` to your project and have the bootstrap
%%% command be a dependency of the build commands. See the nix documentation for
%%% more information.
%%%
%%% This command designed to have as few dependencies as possible so that it can
%%% be a dependency of root level packages like mix. To that end it does many
%%% things in a fairly simplistic way. That is by design.
%%%
%%% ### Assumptions
%%%
%%% This command makes the following assumptions:
%%%
%%% * It is run in a nix-shell or nix-build environment
%%% * that all dependencies have been added to the ERL_LIBS
%%% Environment Variable
-record(data, {version
, erl_libs
, root
, name}).
-define(LOCAL_HEX_REGISTRY, "registry.ets").
main(Args) ->
{ok, RequiredData} = gather_required_data_from_the_environment(Args),
ok = bootstrap_libs(RequiredData).
%% @doc
%% This takes an app name in the standard OTP <name>-<version> format
%% and returns just the app name. Why? Because rebar doesn't
%% respect OTP conventions in some cases.
-spec fixup_app_name(file:name()) -> string().
fixup_app_name(Path) ->
BaseName = filename:basename(Path),
case string:split(BaseName, "-") of
[Name, _Version] -> Name;
Name -> Name
end.
-spec gather_required_data_from_the_environment([string()]) -> {ok, #data{}}.
gather_required_data_from_the_environment(_) ->
{ok, #data{ version = guard_env("version")
, erl_libs = os:getenv("ERL_LIBS", [])
, root = code:root_dir()
, name = guard_env("name")}}.
-spec guard_env(string()) -> string().
guard_env(Name) ->
case os:getenv(Name) of
false ->
stderr("Expected Environment variable ~s! Are you sure you are "
"running in a Nix environment? Either a nix-build, "
"nix-shell, etc?~n", [Name]),
erlang:halt(1);
Variable ->
Variable
end.
-spec bootstrap_libs(#data{}) -> ok.
bootstrap_libs(#data{erl_libs = ErlLibs}) ->
io:format("Bootstrapping dependent libraries~n"),
Target = "_build/prod/lib/",
Paths = string:tokens(ErlLibs, ":"),
CopiableFiles =
lists:foldl(fun(Path, Acc) ->
gather_directory_contents(Path) ++ Acc
end, [], Paths),
lists:foreach(fun (Path) ->
ok = link_app(Path, Target)
end, CopiableFiles).
-spec gather_directory_contents(string()) -> [{string(), string()}].
gather_directory_contents(Path) ->
{ok, Names} = file:list_dir(Path),
lists:map(fun(AppName) ->
{filename:join(Path, AppName), fixup_app_name(AppName)}
end, Names).
%% @doc
%% Makes a symlink from the directory pointed at by Path to a
%% directory of the same name in Target. So if we had a Path of
%% {`foo/bar/baz/bash`, `baz`} and a Target of `faz/foo/foos`, the symlink
%% would be `faz/foo/foos/baz`.
-spec link_app({string(), string()}, string()) -> ok.
link_app({Path, TargetFile}, TargetDir) ->
Target = filename:join(TargetDir, TargetFile),
ok = make_symlink(Path, Target).
-spec make_symlink(string(), string()) -> ok.
make_symlink(Path, TargetFile) ->
file:delete(TargetFile),
ok = filelib:ensure_dir(TargetFile),
io:format("Making symlink from ~s to ~s~n", [Path, TargetFile]),
ok = file:make_symlink(Path, TargetFile).
%% @doc
%% Write the result of the format string out to stderr.
-spec stderr(string(), [term()]) -> ok.
stderr(FormatStr, Args) ->
io:put_chars(standard_error, io_lib:format(FormatStr, Args)).
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