# check_call.ludic — L4: a call gives each parameter the type it asks for, and as many arguments
# as there are parameters. A function, an extern, a function value (a local, a global or a
# record's field) and the builtins that convert are checked; a namespace call (Input.pad_axis)
# gives the result type of the Ludic function behind it, and its arguments are the emitter's.
function ck_params(f: Node, labels: []pointer, tys: []pointer) -> void {
  var i = 0
  while i < len(f.kids) {
    if f.kids[i].kind == N_PARAM {
      push(labels, f.kids[i].s)
      push(tys, f.kids[i].ty)
    }
    i += 1
  }
}
function ck_call_fn(e: Node, name: pointer, f: Node) -> pointer {
  call_fill_defaults(e, f)
  let labels = new []pointer
  let tys = new []pointer
  ck_params(f, labels, tys)
  ck_args(e, name, labels, tys)
  if f.ty == null { return "void" }
  return f.ty
}
function ck_call_alias(e: Node, name: pointer, al: int, f: Node) -> pointer {
  if g_al_labels[al] == null { call_fill_defaults(e, f) } else { call_mixed_to_named(e, ns_alias_labels(al)) }
  let labels = new []pointer
  let tys = new []pointer
  ck_params(f, labels, tys)
  let alabels = ns_alias_labels(al)
  if len(alabels) == len(tys) { ck_args(e, name, alabels, tys) } else { ck_args(e, name, labels, tys) }
  if f.ty == null { return "void" }
  return f.ty
}
function ck_call_sig(e: Node, name: pointer, t: pointer) -> pointer {
  ck_args(e, name, new []pointer, fn_ty_params(t))
  return fn_ty_ret(t)
}
function ck_label_at(labels: []pointer, s: pointer) -> int {
  var i = 0
  while i < len(labels) {
    if labels[i] == s { return i }
    i += 1
  }
  return -1
}
function ck_args(e: Node, name: pointer, labels: []pointer, tys: []pointer) -> void {
  let n = len(e.kids)
  if n > 0 and e.kids[0].kind == E_FINIT {
    var j = 0
    while j < n {
      let fi = e.kids[j]
      let vt = ck_expr(fi.a)
      let at = ck_label_at(labels, fi.s)
      if at >= 0 { ck_give(tys[at], vt, fi.a, `argument {fi.s} of {name}`) }
      if at < 0 and len(labels) > 0 { ck_err("arity", fi.a, `{name} has no parameter {fi.s}`) }
      j += 1
    }
    var m = 0
    while m < len(labels) {
      if not ck_named_has(e, labels[m]) { ck_err("arity", e, `this call to {name} leaves out {labels[m]}, which has no default`) }
      m += 1
    }
    return
  }
  if n < len(tys) and len(labels) == len(tys) { ck_err("arity", e, `this call to {name} leaves out {labels[n]}, which has no default`) }
  else { if n != len(tys) { ck_err("arity", e, `{name} takes {itoa(len(tys))} argument(s) and this call gives {itoa(n)}`) } }
  var i = 0
  while i < n {
    if i < len(tys) { ck_expect = tys[i] }
    let at = ck_expr(e.kids[i])
    if i < len(tys) { ck_give(tys[i], at, e.kids[i], `argument {itoa(i + 1)} of {name}`) }
    i += 1
  }
}
function ck_named_has(e: Node, label: pointer) -> bool {
  var i = 0
  while i < len(e.kids) {
    if (e.kids[i].s == label) { return true }
    i += 1
  }
  return false
}
function ck_walk_args(e: Node) -> void {
  var i = 0
  while i < len(e.kids) {
    ck_any(e.kids[i])
    i += 1
  }
}
# the builtins whose type is their name, and push, whose element must fit the slice
function ck_builtin(e: Node, name: pointer) -> pointer {
  if (name == "string") or (name == "int") or (name == "float") or (name == "fixed") or (name == "long") or (name == "double") {
    ck_walk_args(e)
    return name
  }
  if (name == "as_int") or (name == "as_fixed") {
    ck_walk_args(e)
    return name[3..len(name)]
  }
  if (name == "len") or (name == "float_bits") {
    ck_walk_args(e)
    return "int"
  }
  if (name == "view") and len(e.kids) == 3 {
    let vt = ck_expr(e.kids[0])
    ck_give("int", ck_expr(e.kids[1]), e.kids[1], "the start of a view")
    ck_give("int", ck_expr(e.kids[2]), e.kids[2], "the length of a view")
    if not ck_unknown(vt) and not is_slice_ty(vt) { ck_err("kind", e, `view takes a slice, and this is {ck_a(vt)}`) }
    return vt
  }
  if (name == "bytes") or (name == "offset") {
    ck_walk_args(e)
    return "pointer"
  }
  if (name == "data_of") {
    ck_walk_args(e)
    return "pointer"
  }
  if (name == "words") {
    ck_walk_args(e)
    return "[]int"
  }
  if (name == "buffer") {
    ck_walk_args(e)
    return "[]byte"
  }
  if (name == "fixeds") or (name == "pointers") {
    ck_walk_args(e)
    return "[]" + name[0 .. len(name) - 1]
  }
  if (name == "floats") or (name == "doubles") {
    ck_walk_args(e)
    return "[]" + name[0 .. len(name) - 1]
  }
  if (name == "float_from_bits") {
    ck_walk_args(e)
    return "float"
  }
  if (name == "print") {
    ck_walk_args(e)
    return "void"
  }
  if (name == "push") and len(e.kids) == 2 {
    let st = ck_expr(e.kids[0])
    let vt = ck_expr(e.kids[1])
    if not ck_unknown(st) and is_slice_ty(st) { ck_give(slice_elem(st), vt, e.kids[1], `push onto {ck_a(st)}`) }
    return "void"
  }
  return null
}
# a program's function named like the target of one of the engine's own namespace methods takes
# that method's calls - a package's rng_range(a, b, c) made every Random.range a call to it, and
# the checker then asked for its third argument. Refused where the method is called.
var ck_shadow_seen: []pointer = new []pointer
function ck_alias_shadow(e: Node, al: int, tf: Node) -> void {
  if not has_sub(g_al_file[al], "runtime/native/") { return }
  if tf.file == null or has_sub(tf.file, "runtime/native/") { return }
  var i = 0
  while i < len(ck_shadow_seen) {
    if (ck_shadow_seen[i] == tf.s) { return }
    i += 1
  }
  push(ck_shadow_seen, tf.s)
  ck_err("shadow", tf, `{tf.s} is the engine's {g_al_ns[al]}.{g_al_meth[al]}, which this program calls ({e.file}:{itoa(e.line)}), and every such call would reach this function instead; choose another name`)
}
function ck_call(e: Node) -> pointer {
  let c = e.a
  if c.kind == E_ID { return ck_call_named(e, c.s) }
  if c.kind == E_MEMBER {
    let b = c.a
    if b.kind == E_ID and ck_local(b.s) < 0 and ck_global(b.s) == null {
      # an alias (L6) is its target, labels and all, so its arguments are checked in full
      if (b.s == "Memory") { ck_raw(e, `Memory.{c.s}`) }
      let al = ns_alias_find(b.s, c.s)
      if al >= 0 {
        var tf = ck_fn(g_al_target[al])
        if tf != null { ck_alias_shadow(e, al, tf) }
        if tf == null {
          tf = ck_extern(g_al_target[al])
          if tf != null { ck_raw(e, `{b.s}.{c.s}, a C function`) }
        }
        if tf != null {
          if ck_fn(g_al_target[al]) != null { ck_vis(tf, g_al_target[al], e) }
          ck_extern_arg = ck_extern(g_al_target[al]) != null
          let at = ck_call_alias(e, `{b.s}.{c.s}`, al, tf)
          ck_extern_arg = false
          return at
        }
        ck_walk_args(e)
        return "?"
      }
      # any other Ns.fn is the emitter's own table, which supplies defaults and reorders,
      # so the Ludic function behind it gives the result's type and nothing about the arguments
      ck_walk_args(e)
      let nf = ck_fn(ns_lower(b.s) + "_" + c.s)
      if nf != null { ck_vis(nf, nf.s, e) }
      if nf != null and nf.ty != null { return nf.ty }
      return "?"
    }
    let r = ck_record(ck_expr(b))
    if r != null {
      let ft = ck_field(r, c.s)
      if ft != null and is_fn_type(ft) { return ck_call_sig(e, c.s, ft) }
    }
    ck_walk_args(e)
    return "?"
  }
  ck_expr(c)
  ck_walk_args(e)
  return "?"
}
function ck_call_named(e: Node, name: pointer) -> pointer {
  let li = ck_local(name)
  if li >= 0 {
    if is_fn_type(ck_tys[li]) { return ck_call_sig(e, name, ck_tys[li]) }
    ck_walk_args(e)
    return "?"
  }
  if ck_raw_builtin(name) { ck_raw(e, `{name}()`) }
  let bt = ck_builtin(e, name)
  if bt != null { return bt }
  let f = ck_fn(name)
  if f != null {
    ck_vis(f, name, e)
    return ck_call_fn(e, name, f)
  }
  let gt = gen_template(g_gen_fns, name)
  if gt != null {
    ck_vis(gt, name, e)
    return gen_call(e, name, gt)
  }
  let x = ck_extern(name)
  if x != null {
    ck_raw(e, `the C function {name}`)
    ck_extern_arg = true
    let xt = ck_call_fn(e, name, x)
    ck_extern_arg = false
    return xt
  }
  let g = ck_global(name)
  if g != null and is_fn_type(g.ty) { return ck_call_sig(e, name, g.ty) }
  ck_walk_args(e)
  return "?"
}
# emit E(field: v): each field gets the type the event declares for it
function ck_emit(s: Node) -> void {
  let ev = find_event(s.s)
  ck_vis(ev, s.s, s)
  if s.a == null { return }
  var i = 0
  while i < len(s.a.kids) {
    let fi = s.a.kids[i]
    let vt = ck_expr(fi.a)
    if ev != null {
      let ft = ck_field(ev, fi.s)
      if ft != null { ck_give(ft, vt, fi.a, `field {fi.s} of {s.s}`) }
    }
    i += 1
  }
}