-module(grisp_tools_util).

% API
-export([env/1]).
-export([cdn_path/2]).
-export([otp_path/2]).
-export([package_name/1]).
-export([package_cache_temp/1]).
-export([package_cache_file/1]).
-export([package_cache_etag/1]).
-export([ensure_dir/1]).
-export([mv/2]).
-export([rm/1]).
-export([source_files/2]).
-export([source_hash/2]).
-export([with_file/3]).

%--- Macros --------------------------------------------------------------------

-define(HASH_BLOCK_SIZE, 4194304). % 4MB

%--- API -----------------------------------------------------------------------

% FIXME: Change to grisp_tools when migrated
env(Key) ->
    {ok, Value} = application:get_env(grisp_tools, Key),
    Value.

cdn_path(otp, #{board := Board} = State) ->
    #{path := Path} = URI = uri_string:parse(env(cdn)),
    File = grisp_tools_util:package_name(State) ++ ".tar.gz",
    uri_string:recompose(URI#{
        path => Path ++ string:join(["/platforms", Board, "otp", File], "/")
    }).

otp_path(#{custom_build := true, project_root := Root, otp_version := OTPVersion}, build_root) ->
    filename:join([Root, "otp", OTPVersion, "build"]);
otp_path(#{custom_build := true, project_root := Root, otp_version := OTPVersion}, install_root) ->
    filename:join([Root, "otp", OTPVersion, "install"]);
otp_path(State, install_root) ->
    filename:join([package_dir(), package_name(State)]).

package_name(#{otp_version := OTPVersion, hash := Hash}) ->
    "grisp_otp_build_" ++ OTPVersion ++ "_" ++ Hash.

package_cache_temp(State) ->
    package_cache_file(State) ++ ".temp".

package_cache_file(State) ->
    filename:join(otp_path(State, install_root), package_name(State)).

package_cache_etag(State) ->
    InstallRoot = otp_path(State, install_root),
    Tarball = grisp_tools_util:package_name(State),
    PackageFile = filename:join(InstallRoot, Tarball),
    ETagFile = filename:join(InstallRoot, "ETag"),
    ETag = case {filelib:is_regular(PackageFile), filelib:is_regular(ETagFile)} of
        {true, true}  ->
            {ok, Properties} = file:consult(ETagFile),
            proplists:get_value(etag, Properties);
        _Else ->
            undefined
    end,
    {ETagFile, ETag}.

ensure_dir(File) ->
    case filelib:ensure_dir(File) of
        ok    -> ok;
        Error -> error({create_dir_failed, filename:dirname(File), Error})
    end.

mv(From, To) ->
    rm(To),
    case file:rename(From, To) of
        ok              -> ok;
        Error           -> error({rename_file_failed, From, To, Error})
    end.

rm(File) ->
    case file:delete(File) of
        ok              -> ok;
        {error, enoent} -> ok;
        Error           -> error({delete_file_failed, File, Error})
    end.

source_files(Apps, Board) ->
    lists:foldl(fun({_App, Dir}, {Sys, Drivers}) ->
        {AppSys, AppDrivers} = collect_c_sources(Dir, Board),
        {maps:merge(Sys, AppSys), maps:merge(Drivers, AppDrivers)}
    end, {#{}, #{}}, Apps).

source_hash(Apps, Board) ->
    {DriverFiles, SystemFiles} = source_files(Apps, Board),
    Targets = maps:merge(DriverFiles, SystemFiles),
    hash_files(Targets).

with_file(File, Opts, Fun) ->
    Handle = case file:open(File, Opts) of
        {ok, H} -> H;
        Error   -> error({open_file_failed, File, Error})
    end,
    try
        Fun(Handle)
    after
        file:close(Handle)
    end.

%--- Internal ------------------------------------------------------------------

cache_dir() -> filename:basedir(user_cache, "grisp").

package_dir() -> filename:join([cache_dir(), "packages", "otp"]).

collect_c_sources(Dir, Board) ->
    Source = filename:join([Dir, "grisp", Board]),
    case filelib:is_dir(Source) of
        true  -> {collect_sys(Source), collect_drivers(Source)};
        false -> {#{}, #{}}
    end.

collect_sys(Source) ->
    maps:merge(
        collect_files({Source, "sys/*.h"}, "erts/emulator/sys/unix"),
        collect_files({Source, "sys/*.c"}, "erts/emulator/sys/unix")
    ).

collect_drivers(Source) ->
    maps:merge(
        collect_files(
            {Source, "drivers/*.h"},
            "erts/emulator/drivers/unix"
        ),
        collect_files(
            {Source, "drivers/*.c"},
            "erts/emulator/drivers/unix"
        )
    ).

collect_files({SourceRoot, Pattern}, Target) ->
    Files = filelib:wildcard(filename:join(SourceRoot, Pattern)),
    lists:foldl(fun(File, Collected) ->
        TargetFile = filename:join([Target, filename:basename(File)]),
        Collected#{TargetFile => File}
    end, #{}, Files).

hash_files(Targets) ->
    Sorted = lists:keysort(1, maps:to_list(Targets)),
    FileHashes = lists:map(fun({Target, Source}) ->
        {ok, Hash} = hash_file(Source, sha256),
        {Target, Hash}
    end, Sorted),

    HashIndex = lists:map(fun({Target, Hash}) ->
        io_lib:format("~s ~s~n", [Target, format_hash(sha256, Hash)]) end,
    FileHashes),

    TopHash = format_hash(sha256, crypto:hash(sha256, HashIndex)),
    {TopHash, HashIndex}.

hash_file(File, Algorithm) ->
    Context = crypto:hash_init(Algorithm),
    with_file(File, [binary, raw, read], fun(Handle) ->
        hash_file_read(Handle, Context)
    end).

hash_file_read(Handle, Context) ->
    case file:read(Handle, ?HASH_BLOCK_SIZE) of
        {ok, Bin} -> hash_file_read(Handle, crypto:hash_update(Context, Bin));
        eof       -> {ok, crypto:hash_final(Context)}
    end.

format_hash(sha256, <<Int:256/big-unsigned-integer>>) -> format_hash(Int);
format_hash(md5, <<Int:128/big-unsigned-integer>>)    -> format_hash(Int).

format_hash(Int) when is_integer(Int) -> io_lib:format("~.16b", [Int]).