-module(eyg@parser@location).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch, inline]).
-define(FILEPATH, "src/eyg/parser/location.gleam").
-export([is_empty/1, source_context/2]).

-if(?OTP_RELEASE >= 27).
-define(MODULEDOC(Str), -moduledoc(Str)).
-define(DOC(Str), -doc(Str)).
-else.
-define(MODULEDOC(Str), -compile([])).
-define(DOC(Str), -compile([])).
-endif.

?MODULEDOC(
    " Render source-line context with carets under a span.\n"
    "\n"
    " The same renderer is used for parse errors (single position widened into\n"
    " a one-character span) and runtime errors (whole-expression spans). The\n"
    " interpreter does not depend on this module — the CLI calls it after\n"
    " composing the interpreter's description and hint.\n"
).

-file("src/eyg/parser/location.gleam", 18).
?DOC(" Returns true when a span carries no location information.\n").
-spec is_empty({integer(), integer()}) -> boolean().
is_empty(Span) ->
    Span =:= {0, 0}.

-file("src/eyg/parser/location.gleam", 73).
-spec render_line(integer(), binary(), integer(), integer()) -> binary().
render_line(Line_num, Line, Col, Width) ->
    Num_str = erlang:integer_to_binary(Line_num),
    Gutter = <<<<" "/utf8, Num_str/binary>>/binary, " | "/utf8>>,
    Blank_gutter = gleam@string:repeat(<<" "/utf8>>, string:length(Gutter)),
    <<<<<<<<<<Gutter/binary, Line/binary>>/binary, "\n"/utf8>>/binary,
                Blank_gutter/binary>>/binary,
            (gleam@string:repeat(<<" "/utf8>>, Col))/binary>>/binary,
        (gleam@string:repeat(<<"^"/utf8>>, Width))/binary>>.

-file("src/eyg/parser/location.gleam", 36).
-spec do_render(
    list(binary()),
    integer(),
    integer(),
    integer(),
    integer(),
    list(binary())
) -> list(binary()).
do_render(Lines, Start, End, Line_num, Offset, Acc) ->
    case Lines of
        [] ->
            lists:reverse(Acc);

        [Line | Rest] ->
            Line_len = erlang:byte_size(Line),
            Line_end = Offset + Line_len,
            Line_starts_inside = (Start =< Line_end) andalso (End >= Offset),
            case {Line_starts_inside, Start > Line_end} of
                {_, true} ->
                    do_render(Rest, Start, End, Line_num + 1, Line_end + 1, Acc);

                {false, false} ->
                    Acc;

                {true, false} ->
                    Caret_start = gleam@int:max(0, Start - Offset),
                    Caret_end = gleam@int:min(Line_len, End - Offset),
                    Width = case Start =:= End of
                        true ->
                            1;

                        false ->
                            gleam@int:max(1, Caret_end - Caret_start)
                    end,
                    Rendered = render_line(Line_num, Line, Caret_start, Width),
                    Acc@1 = [Rendered | Acc],
                    do_render(
                        Rest,
                        Start,
                        End,
                        Line_num + 1,
                        Line_end + 1,
                        Acc@1
                    )
            end
    end.

-file("src/eyg/parser/location.gleam", 29).
?DOC(
    " Render the source line(s) containing `span` with carets underneath.\n"
    "\n"
    " - A zero-width span (`#(p, p)`) renders a single `^` at column `p`.\n"
    " - A single-line span renders `^` characters spanning the range.\n"
    " - A multi-line span underlines from the start column to the end of the\n"
    "   first line, then renders subsequent lines (up to and including the line\n"
    "   containing `span.1`) with a row of `^`s underneath each.\n"
).
-spec source_context(binary(), {integer(), integer()}) -> list(binary()).
source_context(Source, Span) ->
    {Start, End} = Span,
    End@1 = gleam@int:max(End, Start),
    Lines = gleam@string:split(Source, <<"\n"/utf8>>),
    do_render(Lines, Start, End@1, 1, 0, []).