fn s8_t ui_tprint_loc(ui_code_loc_t loc) {
    return s8_printf(tcx.temp, "%s(%d)", loc.file, loc.line);
}

fn s8_t ui_get_display_string(s8_t string) {
    s8_t result = string;
    s8_seek(result, s8_lit("##"), s8_seek_none, &result.len);
    return result;
}

fn s8_t ui_get_hash_string(s8_t string) {
    i64 len = 0;
    if (s8_seek(string, s8_lit("##"), s8_seek_none, &len)) {
        string = s8_skip(string, len + 2);
    }
    return string;
}

fn ui_id_t ui_id_from_string(s8_t string) {
    u64 value = hash_data(string);
    ui_id_t result = {value};
    return result;
}

fn u64 ui_hash_code_loc(ui_code_loc_t loc) {
    u64 result = 4242843;
    u64 file_hash = hash_data(s8_from_char(loc.file));
    u64 line_hash = hash_data(s8_struct(loc.line));
    u64 cont_hash = hash_data(s8_struct(loc.counter));
    result = hash_mix(result, file_hash);
    result = hash_mix(result, line_hash);
    result = hash_mix(result, cont_hash);
    return result;
}

fn ui_id_t ui_id_from_code_loc(ui_code_loc_t loc) {
    u64 id = ui_hash_code_loc(loc);
    ui_id_t result = {id};
    return result;
}

fn u64 ui_hash_from_stack(void) {
    u64 result = 34294923;
    for (i32 i = 0; i < ui->id_stack.len; i += 1) {
        result = hash_mix(result, ui->id_stack.data[i].value);
    }
    return result;
}

fn ui_id_t ui_id(s8_t string) {
    string = ui_get_hash_string(string);
    u64 string_hash = hash_data(string);
    u64 stack_hash = ui_hash_from_stack();
    u64 result = hash_mix(string_hash, stack_hash);
    return (ui_id_t){result};
}

fn ui_id_t ui_idf(char *str, ...) {
    S8_FMT(tcx.temp, str, string);
    return ui_id(string);
}

fn void ui_push_id(ui_id_t id) { STACK_PUSH(ui->id_stack, id); }
fn void ui_pop_id(void) { STACK_POP(ui->id_stack); }
fn void ui_push_id_string(s8_t string) { ui_push_id(ui_id(string)); }
fn void ui_push_top(ui_box_t *new_top) { assert(new_top->parent == ui->top); ui->top = new_top; ui_push_id(new_top->id); }
fn void ui_pop_top(void) { ui->top = ui->top->parent; ui_pop_id(); }

fn ui_box_t *ui_alloc_box(void) {
    ui_box_t *box = NULL;
    if (ui->free_first) {
        SLLS_POP_AND_STORE(ui->free_first, box);
    } else {
        box = ma_push_type(ui->box_arena, ui_box_t);
        ui->allocated_boxes += 1;
    }
    return box;
}

fn ui_box_t *ui_find_box(ui_id_t id) {
    if (id.value == 0) return NULL;
    for (ui_box_t *it = ui->hash_first; it; it = it->hash_next) {
        if (it->id.value == id.value) {
            return it;
        }
    }
    return NULL;
}

fn void ui_push_box(ui_box_t *parent, ui_box_t *box) {
    box->parent = parent;
    DLLQ_APPEND(parent->first, parent->last, box);
    parent->node_count += 1;
}

fn r2f32_t ui_next_rect(ui_op_t op, r2f32_t *rect, v2f32_t required_size) {
    switch (op) {
    case ui_op_cut_top: return r2f32_cut_top_no_squash(rect, required_size.y);  break;
    case ui_op_cut_bottom: return r2f32_cut_bottom_no_squash(rect, required_size.y); break;
    case ui_op_cut_left: return r2f32_cut_left_no_squash(rect, required_size.x); break;
    case ui_op_cut_right: return r2f32_cut_right_no_squash(rect, required_size.x); break;
    case ui_op_idle: break;
    default_is_invalid;
    }
    return (r2f32_t){0};
}

fn ui_box_t *ui_build_box_from_id(ui_code_loc_t loc, ui_box_flags_t flags, ui_id_t id) {
    ui_box_t *box = ui_find_box(id);
    if (box) {
        expect (box->last_touched_event_id != ui->event->id) {
            fatalf("likely ui id collision between: %S and %S", ui_tprint_loc(loc), ui_tprint_loc(box->loc));
        }
        memory_zero(box, offsetof(ui_box_t, id));
    } else {
        box = ui_alloc_box();
        box->created_new = true;
        DLLQ_APPEND_EX(ui->hash_first, ui->hash_last, box, hash_next, hash_prev);
    }
    box->loc = loc;
    box->last_touched_event_id = ui->event->id;
    box->id = id;
    box->flags = flags;
    box->text_align = ui->pref_text_align;
    ui_push_box(ui->top, box);
    return box;
}

fn ui_box_t *ui_build_box_from_string(ui_code_loc_t loc, ui_box_flags_t flags, s8_t string) {
    ui_id_t id = ui_id(string);
    ui_box_t *box = ui_build_box_from_id(loc, flags, id);
    box->string = ui_get_display_string(string);
    v2f32_t string_size = rn_measure_string(&rn_state.main_font, box->string);
    string_size.x += ui_em(1);
    r2f32_t rect = ui_next_rect(ui->top->op, &ui->top->rect, string_size);
    ui_set_rect(box, rect);
    return box;
}

#define ui_boxf(flags, ...) ui__boxf(UILOC, flags, __VA_ARGS__)
fn ui_box_t *ui__boxf(ui_code_loc_t loc, ui_box_flags_t flags, char *str, ...) {
    S8_FMT(tcx.temp, str, string);
    ui_box_t *box = ui_build_box_from_string(loc, flags, string);
    return box;
}

fn ui_signal_t ui_signal_from_box(ui_box_t *box) {
    ui_signal_t result = {box};
    app_event_t *ev = ui->event;

    b32 move = ev->kind == app_event_kind_mouse_move;
    b32 inside = r2f32_contains(box->final_rect, ev->mouse_pos);

    if (ui_is_active_box(box)) {
        result.dragging = true;
        if (ev_left_up(ev)) {
            if (ui_is_hot_box(box)) {
                result.clicked = true;
            } else {
                ui->active.value = 0;
            }
        }
    } else if (ui_is_hot_box(box) && ev_left_down(ev)) {
        ui->active = box->id;
    }

    if (inside) {
        ui->hot.value = box->id.value;
    } else if (!inside && ui_is_hot_box(box)) {
        ui->hot = ui_null_id;
    }

    return result;
}

#define ui_button(...) ui__button(UILOC, __VA_ARGS__)
fn ui_signal_t ui__button(ui_code_loc_t loc, char *str, ...) {
    S8_FMT(tcx.temp, str, string);
    ui_box_t *box = ui_build_box_from_string(loc, (ui_box_flags_t){ .draw_border = true, .draw_rect = true, .draw_text = true }, string);
    ui_signal_t signal = ui_signal_from_box(box);
    return signal;
}

#define ui_list_button(...) ui__list_button(UILOC, __VA_ARGS__)
fn ui_signal_t ui__list_button(ui_code_loc_t loc, char *str, ...) {
    S8_FMT(tcx.temp, str, string);
    ui_box_t *box = ui_build_box_from_string(loc, (ui_box_flags_t){ .draw_text = true }, string);
    ui_signal_t signal = ui_signal_from_box(box);
    return signal;
}

#define ui_label(...) ui__label(UILOC, __VA_ARGS__)
fn ui_box_t *ui__label(ui_code_loc_t loc, char *str, ...) {
    S8_FMT(tcx.temp, str, string);
    ui_box_t *box = ui_build_box_from_string(loc, (ui_box_flags_t){ .draw_text = true }, string);
    return box;
}

#define ui_begin_expander(...) ui__begin_expander(UILOC, __VA_ARGS__)
fn ui_signal_t ui__begin_expander(ui_code_loc_t loc, char *str, ...) {
    S8_FMT(tcx.temp, str, string);
    ui_box_t *box = ui_build_box_from_string(loc, (ui_box_flags_t){ .draw_text = true }, string);
    if (box->created_new) box->expanded = true;
    ui_signal_t signal = ui_signal_from_box(box);
    if (signal.clicked) box->expanded = !box->expanded;
    signal.clicked = box->expanded;
    if ( box->expanded) box->string = s8_printf(tcx.temp, "* %S", box->string);
    if (!box->expanded) box->string = s8_printf(tcx.temp, "> %S", box->string);
    if (box->expanded) {
        r2f32_cut_left(&ui->top->rect, ui_em(0.5f));
        ui_push_id(box->id);
    }
    return signal;
}

fn void ui_end_expander(void) {
    r2f32_add_left(&ui->top->rect, ui_em(0.5f));
    ui_pop_id();
}

fn void ui_begin_build(ui_code_loc_t loc, app_event_t *ev, r2f32_t window_rect) {
    ui->event = ev;

    for (ui_box_t *box = ui->hash_first, *next = NULL; box; box = next) {
        next = box->hash_next;
        if (box->id.value == 0) {
            DLLQ_REMOVE_EX(ui->hash_first, ui->hash_last, box, hash_next, hash_prev);
            zero_struct(box);
            SLLS_PUSH(ui->free_first, box);
        }
    }

    zero_struct(&ui->root);
    ui->root.full_rect = ui->root.rect = window_rect;
    ui->top = &ui->root;
    ui->root.loc = loc;
}

fn void ui_end_build(void) {
    assert(ui->top == &ui->root);

    for (ui_box_t *box = ui->hash_first, *next = NULL; box; box = next) {
        next = box->hash_next;
        b32 touched_box_during_update = ui->event->id <= box->last_touched_event_id;
        if (!touched_box_during_update) {
            DLLQ_REMOVE_EX(ui->hash_first, ui->hash_last, box, hash_next, hash_prev);
            zero_struct(box);
            SLLS_PUSH(ui->free_first, box);
        }
    }
}

fn r2f32_t window_rect_from_frame(app_frame_t *frame) {
    r2f32_t window_rect = r2f32(0, 0, frame->window_size.x, frame->window_size.y);
    return window_rect;
}

fn void ui__draw_box(app_frame_t *frame, ui_box_t *box) {
    box->final_rect = box->full_rect;
    r2f32_t rect = box->final_rect;

    v4f32_t rect_color = primary_color_global;
    v4f32_t text_color = black_color_global;
    if (ui_is_hot_box(box)) {
        rect_color = secondary_color_global;
        text_color = accent2_color_global;
    }
    if (ui_is_active_box(box)) {
        rect_color = accent1_color_global;
        text_color = accent1_color_global;
    }

    if (box->flags.draw_rect) {
        rn_draw_rect(rect, rect_color);
    }
    if (box->flags.draw_border) {
        rn_draw_rect_border(rect, accent2_color_global);
    }
    if (box->flags.draw_text) {
        v2f32_t string_size = rn_measure_string(&rn_state.main_font, box->string);
        v2f32_t rect_size = r2f32_get_size(rect);
        v2f32_t rect_string_diff = v2f32_sub(rect_size, string_size);
        v2f32_t center_pos = v2f32_divs(rect_string_diff, 2);
        v2f32_t pos_in_rect = v2f32(0, center_pos.y);
        if (box->text_align == ui_text_align_center) {
            pos_in_rect = center_pos;
        }
        v2f32_t pos = v2f32_add(pos_in_rect, rect.min);
        rn_draw_string(&rn_state.main_font, pos, text_color, box->string);
    }

    r2f32_t prev_clip_rect = ui->clip_rect;
    if (box->flags.clip_rect) {
        ui->clip_rect = box->full_rect;
        rn_set_clip(ui->clip_rect);
    }
    for (ui_box_t *it = box->first; it; it = it->next) {
        ui__draw_box(frame, it);
    }
    if (box->flags.clip_rect) {
        ui->clip_rect = prev_clip_rect;
        rn_set_clip(ui->clip_rect);
    }
}

fn void ui_draw(app_frame_t *frame) {
    ui->clip_rect = window_rect_from_frame(frame);
    rn_set_clip(ui->clip_rect);
    ui__draw_box(frame, &ui->root);
}

fn void ui_demo_init(ma_arena_t *arena) {
    ui = ma_push_type(arena, ui_t);
    ui->box_arena = ma_push_arena(arena, mib(1));
}

fn void ui_serial_subtype(void *p, type_t *type, s8_t name) {
    assert(type->kind != type_kind_invalid);

    switch(type->kind) {
    case type_kind_i8: {
        i8 *n = (i8 *)p;
        if (ui_list_button("%S: %d##slider%S", name, *n, name).dragging) {
            f32 delta = ui->event->mouse_delta.x;
            n[0] += (i8)delta;
        }
        return;
    } break;
    case type_kind_i16: {
        i16 *n = (i16 *)p;
        if (ui_list_button("%S: %d##slider%S", name, *n, name).dragging) {
            f32 delta = ui->event->mouse_delta.x;
            n[0] += (i16)delta;
        }
        return;
    } break;
    case type_kind_i32: {
        i32 *n = (i32 *)p;
        if (ui_list_button("%S: %d##slider%S", name, *n, name).dragging) {
            f32 delta = ui->event->mouse_delta.x;
            n[0] += (i32)delta;
        }
        return;
    } break;
    case type_kind_i64: {
        i64 *n = (i64 *)p;
        if (ui_list_button("%S: %lld##slider%S", name, (long long)*n, name).dragging) {
            f32 delta = ui->event->mouse_delta.x;
            n[0] += (i64)delta;
        }
        return;
    } break;
    case type_kind_u8: {
        u8 *n = (u8 *)p;
        if (ui_list_button("%S: %u##slider%S", name, *n, name).dragging) {
            f32 delta = ui->event->mouse_delta.x;
            n[0] += (u8)delta;
        }
        return;
    } break;
    case type_kind_u16: {
        u16 *n = (u16 *)p;
        if (ui_list_button("%S: %u##slider%S", name, *n, name).dragging) {
            f32 delta = ui->event->mouse_delta.x;
            n[0] += (u16)delta;
        }
        return;
    } break;
    case type_kind_u32: {
        u32 *n = (u32 *)p;
        if (ui_list_button("%S: %u##slider%S", name, *n, name).dragging) {
            f32 delta = ui->event->mouse_delta.x;
            n[0] += (u32)delta;
        }
        return;
    } break;
    case type_kind_u64: {
        u64 *n = (u64 *)p;
        if (ui_list_button("%S: %llu##slider%S", name, (unsigned long long)*n, name).dragging) {
            f32 delta = ui->event->mouse_delta.x;
            n[0] += (u64)delta;
        }
        return;
    } break;
    case type_kind_b8: {
        b8 *n = (b8 *)p;
        if (ui_list_button("%S: %s", name, *n ? "true" : "false").clicked) {
            *n = !*n;
        }
        return;
    } break;
    case type_kind_b16: {
        b16 *n = (b16 *)p;
        if (ui_list_button("%S: %s", name, *n ? "true" : "false").clicked) {
            *n = !*n;
        }
        return;
    } break;
    case type_kind_b32: {
        b32 *n = (b32 *)p;
        if (ui_list_button("%S: %s", name, *n ? "true" : "false").clicked) {
            *n = !*n;
        }
        return;
    } break;
    case type_kind_b64: {
        b64 *n = (b64 *)p;
        if (ui_list_button("%S: %s", name, *n ? "true" : "false").clicked) {
            *n = !*n;
        }
        return;
    } break;
    case type_kind_f32: {
        f32 *n = (f32 *)p;
        if (ui_list_button("%S: %f##slider%S", name, *n, name).dragging) {
            f32 delta = ui->event->mouse_delta.x;
            n[0] += delta;
        }
        return;
    } break;
    case type_kind_f64: {
        f64 *n = (f64 *)p;
        if (ui_list_button("%S: %f##slider%S", name, *n, name).dragging) {
            f32 delta = ui->event->mouse_delta.x;
            n[0] += delta;
        }
        return;
    } break;
    case type_kind_isize: {
        isize *n = (isize *)p;
        if (ui_list_button("%S: %lld##slider%S", name, *n, name).dragging) {
            f32 delta = ui->event->mouse_delta.x;
            n[0] += (isize)delta;
        }
        return;;
    } break;
    case type_kind_usize: {
        usize *n = (usize *)p;
        if (ui_list_button("%S: %llu##slider%S", name, *n, name).dragging) {
            f32 delta = ui->event->mouse_delta.x;
            n[0] += (usize)delta;
        }
        return;;
    } break;
    case type_kind_int: {
        int *n = (int *)p;
        if (ui_list_button("%S: %d##slider%S", name, *n, name).dragging) {
            f32 delta = ui->event->mouse_delta.x;
            n[0] += (int)delta;
        }
        return;;
    } break;
    case type_kind_char: {
        char *n = (char *)p;
        if (ui_list_button("%S: %c##slider%S", name, *n, name).dragging) {
            f32 delta = ui->event->mouse_delta.x;
            n[0] += (char)delta;
        }
        return;;
    } break;
    }

    if (type->kind == type_kind_pointer) {
        ui_label("%S: %S = %llx", name, type->name, *(usize *)p);
        return;
    }

    if (type->kind == type_kind_enum) {
        i64 value = ti_enum_read_value(p, type);
        s8_t string_value = ti_enum_value_to_name(value, type);
        if (ui_list_button("%S: %S = %S", name, type->name, string_value).clicked) {
            i64 new_value = ti_enum_next_value(p, value, type);
            ti_enum_write_value(p, new_value, type);
        }
        return;
    }

    if (type->kind == type_kind_array) {
        defer_if (ui_begin_expander("%S:", name).clicked, ui_end_expander()) {
            for (i32 i = 0; i < type->count; i += 1) {
                ma_temp_t scratch = ma_begin_scratch();
                s8_t index_name = s8_printf(scratch.arena, "[%d]", i);
                void *tmp = ti_extract_array_idx(p, type, i);
                ui_serial_subtype(tmp, type->base, index_name);
                ma_end_scratch(scratch);
            }
        }
        return;
    }

    if (type->kind == type_kind_struct) {
        defer_if (ui_begin_expander("%S:", name).clicked, ui_end_expander()) {
            for (i32 i = 0; i < type->count; i += 1) {
                type_member_t *tm = type->members + i;
                void *tmp = ti_extract_member(p, tm);
                ui_serial_subtype(tmp, tm->type, tm->name);
            }
        }
        return;
    } else {
        ui_label("%S: %S", name, type->name);
    }
}

fn void ui_serial_type(void *p, type_t *type) {
    ui_serial_subtype(p, type, type->name);
}

gb app_event_t ui_test_event;
fn void ui_demo_update(app_frame_t *frame) {
    for (app_event_t *ev = frame->first_event; ev; ev = ev->next) {
        ui_begin_build(UILOC, ev, window_rect_from_frame(frame));

        ui->top->op = ui_op_idle;

        ui_box_t *scroller_box = ui_boxf((ui_box_flags_t){.draw_rect = true, .clip_rect = true}, "scroller");
        ui_set_rect(scroller_box, r2f32_cut_right(&ui->top->rect, ui_em(0.5f)));

        ui_box_t *item_box = ui_boxf((ui_box_flags_t){.draw_rect = true, .clip_rect = true}, "item_box");
        ui_set_rect(item_box, r2f32_cut_left(&ui->top->rect, ui_max));

        static f32 scroller_value;
        defer_block(ui_push_top(item_box), ui_pop_top()) {
            for (i32 i = 0; i < lengthof(tweak_table); i += 1) {
                mt_tweak_t *tweak = tweak_table + i;
                if (tweak->type->kind == type_kind_b32) {
                    b32 *n = (b32 *)tweak->ptr;
                    if (ui_list_button("%S: %s##slider%S", tweak->name, *n ? "true" : "false", tweak->name).clicked) {
                        *n = !*n;
                    }
                } else if (tweak->type->kind == type_kind_f32) {
                    f32 *n = (f32 *)tweak->ptr;
                    ui_signal_t signal = ui_list_button("%S: %f##slider%S", tweak->name, *n, tweak->name);
                    if (signal.dragging) {
                        f32 size = tweak->max - tweak->min;
                        v2f32_t string_size = rn_measure_string(&rn_state.main_font, signal.box->string);
                        f32 delta = (ui->event->mouse_delta.x / string_size.x) * size;
                        *n = CLAMP(*n + delta, tweak->min, tweak->max);
                    }
                } else_is_invalid;
            }
            ui_serial_type(&ui_test_event, type(app_event_t));
            defer_if (ui_begin_expander("app_event_t").clicked, ui_end_expander()) {
                for (int i = 0; i < 2; i += 1) {
                    ui_label("kind: app_event_kind_t##a%d", i);
                    ui_label("ctrl: b8##ds%d", i);
                    ui_label("shift: b8##f%d", i);
                    defer_if (ui_begin_expander("pos: v3f32_t##gg%d", i).clicked, ui_end_expander()) {
                        ui_label("x: f64 = value##hgt%d", i);
                        ui_label("y: f64 = value##r%d", i);
                        ui_label("z: f64 = value##yr%d", i);
                    }
                    defer_if (ui_begin_expander("mouse_pos: v2f32_t##i2%d", i).clicked, ui_end_expander()) {
                        ui_label("x: f64 = value##i3%d", i);
                        ui_label("y: f64 = value##i4%d", i);
                    }
                }
            }
        }

        // @todo: fix scroller to match mouse
        defer_block(ui_push_top(scroller_box), ui_pop_top()) {
            f32 item_count = (f32)item_box->node_count;
            f32 all_items_size = item_count * rn_state.main_font.size;
            f32 item_box_size = r2f32_get_size(ui->top->full_rect).y;
            f32 scroller_box_size = r2f32_get_size(scroller_box->full_rect).y;
            f32 scroller_size = CLAMP(item_box_size / all_items_size, 0, 1.0f);
            f32 scrollable_space = (1 - scroller_size);
            f32 scroller_norm = scroller_value / (all_items_size);
            f32 scroller_percent = scroller_norm * scrollable_space;
            f32 scroller_second = scrollable_space - scroller_percent;

            r2f32_cut_top(&ui->top->rect, scroller_percent * scroller_box_size);
            ui_box_t *box = ui_build_box_from_id(UILOC, (ui_box_flags_t){.draw_border = true, .draw_rect = true}, ui_idf("slider"));
            ui_set_rect(box, r2f32_cut_top(&ui->top->rect, scroller_size * scroller_box_size));
            ui_signal_t signal = ui_signal_from_box(box);
            if (signal.dragging) {
                scroller_value += (ev->mouse_delta.y / item_box_size * 2) * (all_items_size);
                scroller_value = CLAMP(scroller_value, 0, all_items_size);
            }
            if (ev->kind == app_event_kind_mouse_wheel) {
                scroller_value -= ev->mouse_wheel_delta.y;
                scroller_value = CLAMP(scroller_value, 0, all_items_size);
            }

            for (ui_box_t *it = item_box->first; it; it = it->next) {
                it->full_rect.min.y -= scroller_value;
                it->full_rect.max.y -= scroller_value;
                it->rect.min.y -= scroller_value;
                it->rect.max.y -= scroller_value;
            }
        }

        ui_end_build();
    }

    rn_begin();
    ui_draw(frame);
    rn_draw_stringf(&rn_state.main_font, v2f32(0, frame->window_size.y - rn_state.main_font.size), black_color_global, "boxes: %d", ui->allocated_boxes);
    rn_end(frame->window_size, white_color_global);


    // End frame
    for (app_event_t *ev = frame->first_event; ev; ev = ev->next) {
        if (ev_left_up(ev)) {
            ui->active = ui_null_id;
        }
    }
}