Dom.affine

// SPDX-License-Identifier: MPL-2.0
// Dom.affine — minimal virtual-DOM bindings for the Error-Lang Studio IDE.
//
// Written fresh for error-lang (MPL-2.0). This is NOT derived from
// hyperpolymath/affinescript-dom, which is AGPL-3.0-or-later and therefore
// licence-incompatible with this MPL-2.0 estate. The pieces here are (a) FFI
// `extern fn` declarations over the host DOM shim (ide/src/*.js) — function
// signatures, not copyrightable expression — and (b) a small, independently
// authored vnode builder + realiser.
//
// Event model (affine / host-runtime friendly): a vnode carries event bindings
// as (event-name, handler-id) string pairs rather than typed closures. The host
// bridge (Main) maps a handler-id back to a Msg and feeds the TEA run loop, so
// the View stays a pure `Model -> VNode` function with no embedded closures.

module Dom;

use prelude::*;

// ---- host DOM externs (opaque Int node handles) ----
pub extern fn dom_query_selector(selector: String) -> Int;
pub extern fn dom_create_element(tag: String) -> Int;
pub extern fn dom_create_text_node(content: String) -> Int;
pub extern fn dom_append_child(parent: Int, child: Int) -> Unit;
pub extern fn dom_set_attribute(el: Int, name: String, value: String) -> Unit;
pub extern fn dom_clear_children(el: Int) -> Unit;
pub extern fn dom_bind_event(el: Int, event: String, handler_id: String) -> Unit;

// ---- virtual nodes ----
// VElem(tag, attrs, events, children); events are (event-name, handler-id).
pub enum VNode {
  VElem(String, [(String, String)], [(String, String)], [VNode]),
  VText(String)
}

pub fn text(content: String) -> VNode {
  VText(content)
}

pub fn h(tag: String, attrs: [(String, String)], children: [VNode]) -> VNode {
  VElem(tag, attrs, [], children)
}

// element with event bindings, e.g. h_on("button", [("class","btn")], [("click","stop")], [...])
pub fn h_on(tag: String, attrs: [(String, String)], events: [(String, String)], children: [VNode]) -> VNode {
  VElem(tag, attrs, events, children)
}

// ---- realise a vnode into a host DOM node ----
pub fn render(vnode: VNode) -> Int {
  match vnode {
    VText(s) => dom_create_text_node(s),
    VElem(tag, attrs, events, children) => {
      let el = dom_create_element(tag);
      for a in attrs {
        let (name, value) = a;
        dom_set_attribute(el, name, value);
      }
      for ev in events {
        let (name, hid) = ev;
        dom_bind_event(el, name, hid);
      }
      for c in children {
        dom_append_child(el, render(c));
      }
      el
    }
  }
}

// replace the contents of `selector` with `vnode`
pub fn mount(selector: String, vnode: VNode) -> Unit {
  let root = dom_query_selector(selector);
  dom_clear_children(root);
  dom_append_child(root, render(vnode))
}