# ============================================================================
# reflect_io.ludic — Reflect.serialize / Reflect.apply, in Ludic. One call walks
# an entity's whole component set into a generic value tree (value.ludic), and
# its inverse writes a value tree's fields back into a live entity. Together with
# Json.* this is a one-call save/load and the backbone of tooling (debug
# inspectors, network snapshots as text).
#
# It stands on the reflection ABI (world_* builtins — the EV2/EV8 world table)
# and the value tree, so ludicc force-emits the world table and splices value.ludic
# whenever Reflect.serialize/apply appear (parse.ludic + emit_decl.ludic).
#
# Serialize captures each field's raw stored value: a `fixed` field becomes a
# `fixed` node (its Q16.16 value), everything else an `int` node — so a
# serialize -> apply round-trip is bit-exact. The entity's model id rides along
# under the reserved "@kind" key; apply skips any "@"-prefixed key.
# ============================================================================

# entity -> a value-tree object: { "@kind": <model id>, "<Comp>": { "<field>": v, … }, … }
function reflect_serialize(e: int) -> Val {
  let obj = value_object()
  value_put(obj, "@kind", value_int(world_kind(e)))
  let pc = world_prop_count()
  var p = 0
  while p < pc {
    if world_has(e, p) != 0 {
      let comp = value_object()
      let fc = world_field_count(p)
      var f = 0
      while f < fc {
        let fname = world_field_name(p, f)
        let raw = world_get(e, p, f)
        var node = value_int(raw)
        if world_field_type(p, f) == "fixed" { node = value_fixed(raw) }
        value_put(comp, fname, node)
        f += 1
      }
      value_put(obj, world_prop_name(p), comp)
    }
    p += 1
  }
  return obj
}

# write a value-tree object's fields back into entity `e`. Only components the
# entity already has and fields the schema knows are applied; reserved "@"-keys
# (e.g. "@kind") and unknown names are skipped. Returns the number of fields set.
function reflect_apply(e: int, v: Val) -> int {
  var set = 0
  var i = 0
  while i < value_count(v) {
    let pname = value_key_at(v, i)
    if pname[0] != '@' {                            # skip reserved "@…" keys
      let p = world_prop_id(pname)
      if p >= 0 and world_has(e, p) != 0 {
        let comp = value_at(v, i)
        var j = 0
        while j < value_count(comp) {
          let fname = value_key_at(comp, j)
          let f = world_field_id(p, fname)
          if f >= 0 {
            world_set(e, p, f, value_as_int(value_at(comp, j)))
            set += 1
          }
          j += 1
        }
      }
    }
    i += 1
  }
  return set
}