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 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;
    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_from_string(ui_get_hash_string(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 += 50;
    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_rect = true, .draw_text = true, .fully_center_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));
    return signal;
}

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

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(app_frame_t *frame) {
    for (ui_preorder_iter_t it = ui_iterate_preorder(&ui->root); ui_preorder_iter_is_valid(it); ui_iter_advance_preorder(&it)) {
        ui_box_t *box = it.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->flags.fully_center_text) {
                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);
        }
    }
}

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_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 *top_box = ui_boxf((ui_box_flags_t){.draw_rect = true, .draw_border = true}, "top_box");
        ui_set_rect(top_box, r2f32_cut_top(&ui->top->rect, ui_em(1)));
        defer_block(ui_push_top(top_box), ui_pop_top()) {
            top_box->op = ui_op_cut_left;
            ui_button("file");
            ui_button("edit");
        }

        ui_box_t *scroller_box = ui_boxf((ui_box_flags_t){.draw_rect = true}, "scroller");
        ui_set_rect(scroller_box, r2f32_cut_right(&ui->top->rect, ui_em(1)));

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

        // @todo: now actually fill this out with struct data using type info
        static f32 scroller_value;
        defer_block(ui_push_top(item_box), ui_pop_top()) {
            defer_if (ui_begin_expander("app_event_t").clicked, ui_end_expander()) {
                for (int i = 0; i < 10; 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);
                    }
                }
            }
        }


        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;

            scroller_box->op = ui_op_idle;
            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_id_from_string(s8_lit("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();
    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);
    ui_draw(frame);
    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;
        }
    }
}