//! Steam Deck controls -> editor input, as a pure state machine: gui.zig
//! feeds SDL gamepad events in and applies the returned actions (cursor
//! moves, synthetic clicks, wheel ticks, keys, rumble), so the whole
//! mapping replays off-device from deckcap recordings (test/deck/).
//!
//! Layout: right pad moves the pointer (relative, laptop-touchpad-style),
//! left pad scrolls, R2 = select (button 1), L2 = execute (button 2),
//! L1 = look (button 3), dpad down/up = n/N, A = Enter, Y = Tab; execute
//! and look presses also request a brief rumble ack.

const std = @import("std");

// SDL_GamepadButton / SDL_GamepadAxis / touchpad indices (SDL3), verified
// against real deck recordings (test/deck/*.zon) and the pinned SDL's
// hidapi deck driver (touchpad 0 = left pad, 1 = right pad).
pub const BTN_A = 0; // SOUTH
pub const BTN_Y = 3; // NORTH
pub const BTN_L1 = 9; // LEFT_SHOULDER
pub const BTN_DPAD_UP = 11;
pub const BTN_DPAD_DOWN = 12;
pub const AXIS_L2 = 4; // LEFT_TRIGGER, analog 0..32767
pub const AXIS_R2 = 5; // RIGHT_TRIGGER
pub const PAD_LEFT = 0;
pub const PAD_RIGHT = 1;

/// feel knobs: a full-pad finger sweep covers this many screen pixels
/// (the deck's screen is 1280x800) / this many wheel ticks
pub const POINTER_SCALE: f32 = 600.0;
pub const SCROLL_SCALE: f32 = 24.0;
/// the pinned SDL 3.4.4 deck driver skips upstream's pad-Y negation, so
/// touch y arrives 0 = pad bottom; flip this when the sdl dep is bumped
pub const PAD_Y_SIGN: f32 = -1.0;
// analog triggers click at 30% and release at 20%: the gap keeps a value
// hovering near one threshold from chattering press/release pairs
pub const TRIG_PRESS: i16 = 9830;
pub const TRIG_RELEASE: i16 = 6553;

pub const Input = union(enum) {
    button: struct { idx: u8, down: bool },
    axis: struct { idx: u8, value: i16 },
    touch: struct { pad: u8, phase: enum { down, motion, up }, x: f32, y: f32 },
};

pub const Click = enum { select, execute, look }; // mouse buttons 1/2/3
pub const Keytap = enum { n, cap_n, enter, tab };

pub const Action = union(enum) {
    move: struct { dx: f32, dy: f32 }, // pointer delta in screen pixels
    click: struct { which: Click, down: bool },
    wheel: i32, // whole ticks, positive = wheel_down
    key: Keytap,
    rumble,
};

pub const Deck = struct {
    rpad_on: bool = false,
    rpad_x: f32 = 0,
    rpad_y: f32 = 0,
    lpad_on: bool = false,
    lpad_y: f32 = 0,
    scroll: f32 = 0, // fractional wheel ticks carried between motions
    l2_held: bool = false,
    r2_held: bool = false,
    look_held: bool = false,

    pub fn feed(d: *Deck, in: Input, out: *[2]Action) usize {
        var n: usize = 0;
        switch (in) {
            .button => |b| switch (b.idx) {
                BTN_A => if (b.down) {
                    out[0] = .{ .key = .enter };
                    n = 1;
                },
                BTN_Y => if (b.down) {
                    out[0] = .{ .key = .tab };
                    n = 1;
                },
                BTN_DPAD_UP => if (b.down) {
                    out[0] = .{ .key = .cap_n };
                    n = 1;
                },
                BTN_DPAD_DOWN => if (b.down) {
                    out[0] = .{ .key = .n };
                    n = 1;
                },
                BTN_L1 => {
                    d.look_held = b.down;
                    out[0] = .{ .click = .{ .which = .look, .down = b.down } };
                    n = 1;
                    if (b.down) {
                        out[1] = .rumble;
                        n = 2;
                    }
                },
                else => {},
            },
            .axis => |a| {
                if (a.idx != AXIS_L2 and a.idx != AXIS_R2) return 0;
                const held = if (a.idx == AXIS_L2) &d.l2_held else &d.r2_held;
                const which: Click = if (a.idx == AXIS_L2) .execute else .select;
                if (!held.* and a.value >= TRIG_PRESS) {
                    held.* = true;
                    out[0] = .{ .click = .{ .which = which, .down = true } };
                    n = 1;
                    if (which == .execute) {
                        out[1] = .rumble;
                        n = 2;
                    }
                } else if (held.* and a.value <= TRIG_RELEASE) {
                    held.* = false;
                    out[0] = .{ .click = .{ .which = which, .down = false } };
                    n = 1;
                }
            },
            .touch => |t| switch (t.pad) {
                PAD_RIGHT => switch (t.phase) {
                    // a fresh touch only re-anchors — deltas start from the
                    // landing point, so the pointer never jumps to it
                    .down => {
                        d.rpad_on = true;
                        d.rpad_x = t.x;
                        d.rpad_y = t.y;
                    },
                    .motion => if (d.rpad_on) {
                        out[0] = .{ .move = .{
                            .dx = (t.x - d.rpad_x) * POINTER_SCALE,
                            .dy = (t.y - d.rpad_y) * PAD_Y_SIGN * POINTER_SCALE,
                        } };
                        n = 1;
                        d.rpad_x = t.x;
                        d.rpad_y = t.y;
                    },
                    .up => d.rpad_on = false,
                },
                PAD_LEFT => switch (t.phase) {
                    .down => {
                        d.lpad_on = true;
                        d.lpad_y = t.y;
                    },
                    .motion => if (d.lpad_on) {
                        d.scroll += (t.y - d.lpad_y) * PAD_Y_SIGN * SCROLL_SCALE;
                        d.lpad_y = t.y;
                        const ticks: i32 = @intFromFloat(d.scroll);
                        if (ticks != 0) {
                            d.scroll -= @floatFromInt(ticks);
                            out[0] = .{ .wheel = ticks };
                            n = 1;
                        }
                    },
                    .up => d.lpad_on = false,
                },
                else => {},
            },
        }
        return n;
    }
};