-module(etui@color).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch, inline]).
-define(FILEPATH, "src/etui/color.gleam").
-export([lerp_rgb/4, hue_to_rgb/1, rainbow/2, gradient/3, pulse/3, scale/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.

-file("src/etui/color.gleam", 13).
?DOC(
    " Linear interpolation between two Rgb colors.\n"
    " For non-Rgb inputs, returns whichever endpoint is closer to t.\n"
).
-spec lerp_rgb(etui@style:color(), etui@style:color(), integer(), integer()) -> etui@style:color().
lerp_rgb(A, B, T, Max) ->
    case {A, B} of
        {{rgb, R1, G1, B1}, {rgb, R2, G2, B2}} ->
            {rgb,
                etui@anim:lerp(R1, R2, T, Max),
                etui@anim:lerp(G1, G2, T, Max),
                etui@anim:lerp(B1, B2, T, Max)};

        {_, _} ->
            case (T * 2) < Max of
                true ->
                    A;

                false ->
                    B
            end
    end.

-file("src/etui/color.gleam", 39).
?DOC(
    " Convert a hue angle (0–359) to a fully-saturated Rgb color.\n"
    " Implements the HSV→RGB formula with S=1, V=1, integer arithmetic.\n"
).
-spec hue_to_rgb(integer()) -> etui@style:color().
hue_to_rgb(Hue) ->
    H = ((Hue rem 360) + 360) rem 360,
    Sector = H div 60,
    F = H rem 60,
    Up = (F * 255) div 60,
    Dn = ((60 - F) * 255) div 60,
    case Sector of
        0 ->
            {rgb, 255, Up, 0};

        1 ->
            {rgb, Dn, 255, 0};

        2 ->
            {rgb, 0, 255, Up};

        3 ->
            {rgb, 0, Dn, 255};

        4 ->
            {rgb, Up, 0, 255};

        _ ->
            {rgb, 255, 0, Dn}
    end.

-file("src/etui/color.gleam", 60).
?DOC(
    " Returns an Rgb color that cycles through the full hue spectrum\n"
    " with the given period in frames.\n"
).
-spec rainbow(integer(), integer()) -> etui@style:color().
rainbow(Frame, Period) ->
    P = gleam@int:max(1, Period),
    hue_to_rgb(case P of
            0 -> 0;
            Gleam@denominator -> etui@anim:cycle(Frame, P) * 360 div Gleam@denominator
        end).

-file("src/etui/color.gleam", 127).
-spec get_nth(list(etui@style:color()), integer()) -> etui@style:color().
get_nth(Colors, N) ->
    case Colors of
        [] ->
            default;

        [C | _] when N =< 0 ->
            C;

        [_ | Rest] ->
            get_nth(Rest, N - 1)
    end.

-file("src/etui/color.gleam", 71).
?DOC(
    " Color at integer position `pos` within [0, max] across a list of\n"
    " color stops. Stops are distributed evenly. Lerps between adjacent\n"
    " stops. Requires Rgb stops for smooth blending; non-Rgb stops snap.\n"
).
-spec gradient(list(etui@style:color()), integer(), integer()) -> etui@style:color().
gradient(Stops, Pos, Max) ->
    N = erlang:length(Stops),
    case N of
        0 ->
            default;

        1 ->
            case Stops of
                [C | _] ->
                    C;

                [] ->
                    default
            end;

        _ ->
            Segs = N - 1,
            Seg_size = gleam@int:max(1, case Segs of
                    0 -> 0;
                    Gleam@denominator -> Max div Gleam@denominator
                end),
            Seg_idx = gleam@int:min(Segs - 1, case Seg_size of
                    0 -> 0;
                    Gleam@denominator@1 -> Pos div Gleam@denominator@1
                end),
            Seg_pos = Pos - (Seg_idx * Seg_size),
            lerp_rgb(
                get_nth(Stops, Seg_idx),
                get_nth(Stops, Seg_idx + 1),
                Seg_pos,
                Seg_size
            )
    end.

-file("src/etui/color.gleam", 101).
?DOC(
    " Oscillate an Rgb color between half and full brightness.\n"
    " Use `frame + x * phase_step` for a per-cell wave effect.\n"
    " Non-Rgb colors are returned unchanged.\n"
).
-spec pulse(etui@style:color(), integer(), integer()) -> etui@style:color().
pulse(C, Frame, Period) ->
    case C of
        {rgb, R, G, B} ->
            Bright = etui@anim:oscillate(
                128,
                255,
                Frame,
                gleam@int:max(1, Period)
            ),
            {rgb,
                (R * Bright) div 255,
                (G * Bright) div 255,
                (B * Bright) div 255};

        _ ->
            C
    end.

-file("src/etui/color.gleam", 116).
?DOC(
    " Scale all RGB channels by `factor` / 255.\n"
    " factor=255 → unchanged, factor=128 → half brightness.\n"
).
-spec scale(etui@style:color(), integer()) -> etui@style:color().
scale(C, Factor) ->
    case C of
        {rgb, R, G, B} ->
            {rgb,
                (R * Factor) div 255,
                (G * Factor) div 255,
                (B * Factor) div 255};

        _ ->
            C
    end.