-module(eyg@parser@debug).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch, inline]).
-define(FILEPATH, "src/eyg/parser/debug.gleam").
-export([describe/1, hint/1]).

-file("src/eyg/parser/debug.gleam", 6).
-spec describe(eyg@parser@parser:reason()) -> binary().
describe(Reason) ->
    case Reason of
        {unexpected_token, Token, Position} ->
            <<<<<<"unexpected `"/utf8,
                        (eyg@parser@token:to_string(Token))/binary>>/binary,
                    "` at position "/utf8>>/binary,
                (erlang:integer_to_binary(Position))/binary>>;

        unexpect_end ->
            <<"unexpected end of input"/utf8>>;

        {invalid_character, Char, Position@1} ->
            <<<<<<"invalid character '"/utf8, Char/binary>>/binary,
                    "' at position "/utf8>>/binary,
                (erlang:integer_to_binary(Position@1))/binary>>;

        {unterminated_string_literal, Position@2} ->
            <<"unterminated string literal at position "/utf8,
                (erlang:integer_to_binary(Position@2))/binary>>;

        {invalid_escape_sequence, Escape_char, Position@3} ->
            <<<<<<"invalid escape sequence `\\"/utf8, Escape_char/binary>>/binary,
                    "` in string at position "/utf8>>/binary,
                (erlang:integer_to_binary(Position@3))/binary>>;

        {missing_equals, Position@4} ->
            <<"expected `=` after let binding name at position "/utf8,
                (erlang:integer_to_binary(Position@4))/binary>>;

        {missing_arrow, Position@5} ->
            <<"expected `->` followed by `{` in function definition at position "/utf8,
                (erlang:integer_to_binary(Position@5))/binary>>;

        {unclosed_function_body, Open_at} ->
            <<"unclosed function body — expected `}` to close the `{` opened at position "/utf8,
                (erlang:integer_to_binary(Open_at))/binary>>;

        {expected_effect_name, Keyword, Position@6} ->
            <<<<<<"expected an uppercase effect name after `"/utf8,
                        Keyword/binary>>/binary,
                    "` at position "/utf8>>/binary,
                (erlang:integer_to_binary(Position@6))/binary>>;

        {expected_builtin_name, Position@7} ->
            <<"expected a builtin identifier after `!` at position "/utf8,
                (erlang:integer_to_binary(Position@7))/binary>>;

        {invalid_cid_reference, Position@8} ->
            <<"invalid content identifier (CID) at position "/utf8,
                (erlang:integer_to_binary(Position@8))/binary>>;

        {invalid_release_version, Position@9} ->
            <<"expected an integer release version after `:` at position "/utf8,
                (erlang:integer_to_binary(Position@9))/binary>>;

        {invalid_import_path, Position@10} ->
            <<"expected a string path after `import` at position "/utf8,
                (erlang:integer_to_binary(Position@10))/binary>>;

        {trailing_tokens, Token@1, Position@11} ->
            Token_str = case Token@1 of
                {unexpected_grapheme, Raw} ->
                    gleam@string:slice(Raw, 0, 1);

                _ ->
                    eyg@parser@token:to_string(Token@1)
            end,
            <<<<<<<<"unexpected `"/utf8, Token_str/binary>>/binary,
                        "` at position "/utf8>>/binary,
                    (erlang:integer_to_binary(Position@11))/binary>>/binary,
                " — the expression is complete but there are leftover tokens"/utf8>>
    end.

-file("src/eyg/parser/debug.gleam", 65).
-spec hint(eyg@parser@parser:reason()) -> binary().
hint(Reason) ->
    case Reason of
        {unexpected_token, _, _} ->
            <<"view the syntax guide"/utf8>>;

        unexpect_end ->
            <<"program must end with valid expression"/utf8>>;

        {invalid_character, _, _} ->
            <<"remove or replace this character — EYG does not use it"/utf8>>;

        {unterminated_string_literal, _} ->
            <<"close the string with a double-quote `\"`"/utf8>>;

        {invalid_escape_sequence, _, _} ->
            <<"valid escapes are \\n (newline), \\t (tab), \\r (carriage return), \\\" (quote), \\\\ (backslash)"/utf8>>;

        {missing_equals, _} ->
            <<"let bindings use the form `let name = expression`"/utf8>>;

        {missing_arrow, _} ->
            <<"functions are written as `(arg) -> { body }`"/utf8>>;

        {unclosed_function_body, _} ->
            <<"every `{` in a function body must be closed with `}`"/utf8>>;

        {expected_effect_name, Keyword, _} ->
            <<<<"effect names must start with an uppercase letter, e.g. `"/utf8,
                    Keyword/binary>>/binary,
                " Log`"/utf8>>;

        {expected_builtin_name, _} ->
            <<"builtins use lowercase names, e.g. `!int_add`"/utf8>>;

        {invalid_cid_reference, _} ->
            <<"CID references use a valid base32-encoded CID, e.g. `#bafyreig...`"/utf8>>;

        {invalid_release_version, _} ->
            <<"pin a release with `@package:N` (e.g. `@tandard:3`) or omit `:` to track the latest"/utf8>>;

        {invalid_import_path, _} ->
            <<"import paths must be string literals, e.g. `import \"./module.eyg.json\"`"/utf8>>;

        {trailing_tokens, Token, _} ->
            case Token of
                'let' ->
                    <<"the previous expression already completed the block. If you meant the block to continue, bind that expression to `let _ = ...` first."/utf8>>;

                _ ->
                    <<"EYG uses function calls for operations, not infix operators"/utf8>>
            end
    end.