-module(metamon@diff).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch, inline]).
-define(FILEPATH, "src/metamon/diff.gleam").
-export([diff/2, diff_string/2, render/1]).
-export_type([diff/0, indexed_diff/0, segment/0]).

-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(
    " Structural diff for failure reports. Compares two values\n"
    " element-by-element and produces a tree that the formatter can\n"
    " render compactly.\n"
    "\n"
    " The implementation is type-erased: it inspects the dynamic shape\n"
    " of each side via `string.inspect`. This is sufficient for the\n"
    " failure-report use case (we only need to *display* the diff, not\n"
    " reason about it programmatically), and avoids requiring users to\n"
    " supply per-type formatters.\n"
).

-type diff() :: {same, binary()} |
    {differ, binary(), binary()} |
    {list_diff, list(indexed_diff())} |
    {tuple_diff, list(indexed_diff())} |
    {string_diff, binary(), binary(), list(segment())}.

-type indexed_diff() :: {indexed_diff, integer(), diff()}.

-type segment() :: {common, binary()} | {removed, binary()} | {added, binary()}.

-file("src/metamon/diff.gleam", 70).
-spec is_list_inspect(binary()) -> boolean().
is_list_inspect(S) ->
    gleam_stdlib:string_starts_with(S, <<"["/utf8>>) andalso gleam_stdlib:string_ends_with(
        S,
        <<"]"/utf8>>
    ).

-file("src/metamon/diff.gleam", 74).
-spec is_tuple_inspect(binary()) -> boolean().
is_tuple_inspect(S) ->
    gleam_stdlib:string_starts_with(S, <<"#("/utf8>>) andalso gleam_stdlib:string_ends_with(
        S,
        <<")"/utf8>>
    ).

-file("src/metamon/diff.gleam", 94).
-spec drop_tuple_prefix(binary()) -> binary().
drop_tuple_prefix(Inspected) ->
    case gleam_stdlib:string_starts_with(Inspected, <<"#("/utf8>>) of
        true ->
            <<"("/utf8, (gleam@string:drop_start(Inspected, 2))/binary>>;

        false ->
            Inspected
    end.

-file("src/metamon/diff.gleam", 101).
-spec zip_items(list(binary()), list(binary()), integer()) -> list(indexed_diff()).
zip_items(Left, Right, Index) ->
    case {Left, Right} of
        {[], []} ->
            [];

        {[], [R | Rs]} ->
            [{indexed_diff, Index, {differ, <<"·"/utf8>>, R}} |
                zip_items([], Rs, Index + 1)];

        {[L | Ls], []} ->
            [{indexed_diff, Index, {differ, L, <<"·"/utf8>>}} |
                zip_items(Ls, [], Index + 1)];

        {[L@1 | Ls@1], [R@1 | Rs@1]} ->
            Inner = case L@1 =:= R@1 of
                true ->
                    {same, L@1};

                false ->
                    {differ, L@1, R@1}
            end,
            [{indexed_diff, Index, Inner} | zip_items(Ls@1, Rs@1, Index + 1)]
    end.

-file("src/metamon/diff.gleam", 174).
-spec finish_split(binary(), list(binary())) -> list(binary()).
finish_split(Acc, Results) ->
    case gleam@string:trim(Acc) of
        <<""/utf8>> ->
            lists:reverse(Results);

        Trimmed ->
            lists:reverse([Trimmed | Results])
    end.

-file("src/metamon/diff.gleam", 154).
-spec walk_and_split(list(binary()), integer(), binary(), list(binary())) -> list(binary()).
walk_and_split(Graphemes, Depth, Acc, Results) ->
    case Graphemes of
        [] ->
            finish_split(Acc, Results);

        [First | Rest] ->
            case {First, Depth} of
                {<<"["/utf8>>, _} ->
                    walk_and_split(
                        Rest,
                        Depth + 1,
                        <<Acc/binary, First/binary>>,
                        Results
                    );

                {<<"]"/utf8>>, D} when D > 0 ->
                    walk_and_split(
                        Rest,
                        D - 1,
                        <<Acc/binary, First/binary>>,
                        Results
                    );

                {<<"("/utf8>>, _} ->
                    walk_and_split(
                        Rest,
                        Depth + 1,
                        <<Acc/binary, First/binary>>,
                        Results
                    );

                {<<")"/utf8>>, D@1} when D@1 > 0 ->
                    walk_and_split(
                        Rest,
                        D@1 - 1,
                        <<Acc/binary, First/binary>>,
                        Results
                    );

                {<<","/utf8>>, 0} ->
                    walk_and_split(
                        Rest,
                        0,
                        <<""/utf8>>,
                        [gleam@string:trim(Acc) | Results]
                    );

                {_, _} ->
                    walk_and_split(
                        Rest,
                        Depth,
                        <<Acc/binary, First/binary>>,
                        Results
                    )
            end
    end.

-file("src/metamon/diff.gleam", 126).
-spec split_top_level(binary()) -> list(binary()).
split_top_level(Inspected) ->
    Inner = case {gleam_stdlib:string_starts_with(Inspected, <<"["/utf8>>),
        gleam_stdlib:string_ends_with(Inspected, <<"]"/utf8>>)} of
        {true, true} ->
            _pipe = Inspected,
            _pipe@1 = gleam@string:drop_start(_pipe, 1),
            gleam@string:drop_end(_pipe@1, 1);

        {_, _} ->
            case {gleam_stdlib:string_starts_with(Inspected, <<"("/utf8>>),
                gleam_stdlib:string_ends_with(Inspected, <<")"/utf8>>)} of
                {true, true} ->
                    _pipe@2 = Inspected,
                    _pipe@3 = gleam@string:drop_start(_pipe@2, 1),
                    gleam@string:drop_end(_pipe@3, 1);

                {_, _} ->
                    Inspected
            end
    end,
    walk_and_split(gleam@string:to_graphemes(Inner), 0, <<""/utf8>>, []).

-file("src/metamon/diff.gleam", 78).
-spec list_diff_from_inspect(binary(), binary()) -> diff().
list_diff_from_inspect(Left, Right) ->
    L_items = split_top_level(Left),
    R_items = split_top_level(Right),
    {list_diff, zip_items(L_items, R_items, 0)}.

-file("src/metamon/diff.gleam", 84).
-spec tuple_diff_from_inspect(binary(), binary()) -> diff().
tuple_diff_from_inspect(Left, Right) ->
    L_inner = drop_tuple_prefix(Left),
    R_inner = drop_tuple_prefix(Right),
    L_items = split_top_level(L_inner),
    R_items = split_top_level(R_inner),
    {tuple_diff, zip_items(L_items, R_items, 0)}.

-file("src/metamon/diff.gleam", 55).
-spec shape_aware_diff(GFI, GFI) -> diff().
shape_aware_diff(Left, Right) ->
    L_str = gleam@string:inspect(Left),
    R_str = gleam@string:inspect(Right),
    case {is_list_inspect(L_str),
        is_list_inspect(R_str),
        is_tuple_inspect(L_str),
        is_tuple_inspect(R_str)} of
        {true, true, _, _} ->
            list_diff_from_inspect(L_str, R_str);

        {_, _, true, true} ->
            tuple_diff_from_inspect(L_str, R_str);

        {_, _, _, _} ->
            {differ, L_str, R_str}
    end.

-file("src/metamon/diff.gleam", 48).
?DOC(
    " Compute a structural diff between two values. Equal inputs collapse\n"
    " to `Same`; otherwise the result depends on whether\n"
    " `string.inspect` exposes list-shaped or string-shaped output.\n"
).
-spec diff(GFH, GFH) -> diff().
diff(Left, Right) ->
    case Left =:= Right of
        true ->
            {same, gleam@string:inspect(Left)};

        false ->
            shape_aware_diff(Left, Right)
    end.

-file("src/metamon/diff.gleam", 234).
-spec render_string_diff(list(segment()), binary()) -> binary().
render_string_diff(Segments, Indent) ->
    _pipe = gleam@list:map(Segments, fun(Segment) -> case Segment of
                {common, Text} ->
                    <<<<Indent/binary, "  "/utf8>>/binary, Text/binary>>;

                {removed, Text@1} ->
                    <<<<Indent/binary, "- "/utf8>>/binary, Text@1/binary>>;

                {added, Text@2} ->
                    <<<<Indent/binary, "+ "/utf8>>/binary, Text@2/binary>>
            end end),
    gleam@string:join(_pipe, <<"\n"/utf8>>).

-file("src/metamon/diff.gleam", 278).
-spec empty_row(list(binary())) -> list(integer()).
empty_row(Right) ->
    [0 | gleam@list:map(Right, fun(_) -> 0 end)].

-file("src/metamon/diff.gleam", 310).
-spec max_int(integer(), integer()) -> integer().
max_int(A, B) ->
    case A >= B of
        true ->
            A;

        false ->
            B
    end.

-file("src/metamon/diff.gleam", 282).
-spec build_row(
    binary(),
    list(binary()),
    list(integer()),
    list(integer()),
    integer()
) -> list(integer()).
build_row(L, Remaining, Prev_row, Acc, Current_left_value) ->
    case {Remaining, Prev_row} of
        {[], _} ->
            lists:reverse([Current_left_value | Acc]);

        {[R | Rs], [_ | Rest_prev]} ->
            Above = case Rest_prev of
                [V | _] ->
                    V;

                [] ->
                    0
            end,
            Diagonal = case Prev_row of
                [V@1 | _] ->
                    V@1;

                [] ->
                    0
            end,
            Value = case L =:= R of
                true ->
                    Diagonal + 1;

                false ->
                    max_int(Above, Current_left_value)
            end,
            build_row(L, Rs, Rest_prev, [Current_left_value | Acc], Value);

        {_, []} ->
            lists:reverse([Current_left_value | Acc])
    end.

-file("src/metamon/diff.gleam", 257).
-spec build_rows(list(binary()), list(binary()), list(list(integer()))) -> list(list(integer())).
build_rows(Remaining_left, Right, Acc) ->
    case Remaining_left of
        [] ->
            Row_for_empty = gleam@list:map(Right, fun(_) -> 0 end),
            lists:reverse([[0 | Row_for_empty] | Acc]);

        [First | Rest] ->
            Prev_row = case Acc of
                [] ->
                    empty_row(Right);

                [Most_recent | _] ->
                    Most_recent
            end,
            Row = build_row(First, Right, Prev_row, [], 0),
            build_rows(Rest, Right, [Row | Acc])
    end.

-file("src/metamon/diff.gleam", 253).
-spec build_lcs(list(binary()), list(binary())) -> list(list(integer())).
build_lcs(Left, Right) ->
    build_rows(Left, Right, []).

-file("src/metamon/diff.gleam", 317).
-spec backtrack_diff(list(binary()), list(binary()), list(list(integer()))) -> list(segment()).
backtrack_diff(Left, Right, _) ->
    case {Left, Right} of
        {[], []} ->
            [];

        {[], [R | Rs]} ->
            [{added, R} | backtrack_diff([], Rs, [])];

        {[L | Ls], []} ->
            [{removed, L} | backtrack_diff(Ls, [], [])];

        {[L@1 | Ls@1], [R@1 | Rs@1]} ->
            case L@1 =:= R@1 of
                true ->
                    [{common, L@1} | backtrack_diff(Ls@1, Rs@1, [])];

                false ->
                    [{removed, L@1},
                        {added, R@1} |
                        backtrack_diff(Ls@1, Rs@1, [])]
            end
    end.

-file("src/metamon/diff.gleam", 185).
?DOC(
    " Multi-line string diff using a longest-common-subsequence (LCS) on\n"
    " lines. Lines unique to the left side are shown as `Removed`, lines\n"
    " unique to the right are shown as `Added`, lines present in both\n"
    " are shown as `Common`.\n"
).
-spec diff_string(binary(), binary()) -> diff().
diff_string(Left, Right) ->
    case Left =:= Right of
        true ->
            {same, Left};

        false ->
            L_lines = gleam@string:split(Left, <<"\n"/utf8>>),
            R_lines = gleam@string:split(Right, <<"\n"/utf8>>),
            Lcs_table = build_lcs(L_lines, R_lines),
            Segments = backtrack_diff(L_lines, R_lines, Lcs_table),
            {string_diff, Left, Right, Segments}
    end.

-file("src/metamon/diff.gleam", 214).
-spec render_list_diff(list(indexed_diff()), binary(), binary()) -> binary().
render_list_diff(Items, Indent, Prefix) ->
    Close = case Prefix of
        <<"#."/utf8>> ->
            <<""/utf8>>;

        _ ->
            <<"]"/utf8>>
    end,
    _pipe = gleam@list:map(
        Items,
        fun(Item) ->
            <<<<<<<<<<Indent/binary, Prefix/binary>>/binary,
                            (erlang:integer_to_binary(erlang:element(2, Item)))/binary>>/binary,
                        Close/binary>>/binary,
                    "\n"/utf8>>/binary,
                (render_with_indent(
                    erlang:element(3, Item),
                    <<Indent/binary, "  "/utf8>>
                ))/binary>>
        end
    ),
    gleam@string:join(_pipe, <<"\n"/utf8>>).

-file("src/metamon/diff.gleam", 203).
-spec render_with_indent(diff(), binary()) -> binary().
render_with_indent(D, Indent) ->
    case D of
        {same, Rendered} ->
            <<<<Indent/binary, "= "/utf8>>/binary, Rendered/binary>>;

        {differ, Left, Right} ->
            <<<<<<<<<<<<Indent/binary, "- "/utf8>>/binary, Left/binary>>/binary,
                            "\n"/utf8>>/binary,
                        Indent/binary>>/binary,
                    "+ "/utf8>>/binary,
                Right/binary>>;

        {list_diff, Items} ->
            render_list_diff(Items, Indent, <<"[#"/utf8>>);

        {tuple_diff, Items@1} ->
            render_list_diff(Items@1, Indent, <<"#."/utf8>>);

        {string_diff, _, _, Segments} ->
            render_string_diff(Segments, Indent)
    end.

-file("src/metamon/diff.gleam", 199).
?DOC(" Render a `Diff` as a human-readable multi-line string.\n").
-spec render(diff()) -> binary().
render(D) ->
    render_with_indent(D, <<""/utf8>>).