# style_rule.ludic - a rule read, the cascade a file sees, and a node's rules applied to it
function lss_rule(f: UiFile, sels: string, body: string, err: []string, line: int) -> void {
  let decls = lss_decls(body, err)
  let each = lss_split(sels, 44)
  for i in 0 .. len(each) {
    let sel = tpl_words(each[i])
    if len(sel) > 0 { lss_rule_add(f, decls, sel, err, line) }
    unsafe {                           # a selector keeps its parsed parts, never its text
      if not tpl_clean(each[i]) { free(sel) }
      free(each[i])
    }
  }
  unsafe {
    free(each)
    free(decls)                        # the holder only: each rule keeps its keys and values lists
  }
}
function lss_rule_add(f: UiFile, decls: UiRule, sel: string, err: []string, line: int) -> void {
  let r = new UiRule
  r.keys = decls.keys
  r.vals = decls.vals
  r.text = `{sel}`                     # a copy: the selector's text is given back below
  r.at = `{f.path}:{line}`
  r.sel = sel_parse(sel, err)
  if r.sel != null {
    r.spec = sel_spec(r.sel)
    push(f.own, r)
  }
}
# `key: value; key: value`, a rule's body or a style="..." attribute
function lss_decls(body: string, err: []string) -> UiRule {
  let r = new UiRule
  r.keys = new []string
  r.vals = new []UiExpr
  let decls = lss_split(body, 59)
  for i in 0 .. len(decls) {
    let d = decls[i]
    var colon = -1
    for k in 0 .. len(d) {
      if colon < 0 and d[k] == 58 { colon = k }
    }
    if colon < 0 {
      if len(tpl_words(d)) > 0 { push(err, `"{tpl_words(d)}" is not a property: value`) }
      continue
    }
    lss_decl_add(r, d, colon, err)
  }
  unsafe {                             # the pieces the declarations were sliced from
    for i in 0 .. len(decls) { free(decls[i]) }
    free(decls)
  }
  return r
}
@alloc_ok("a memo miss (mm_split) or a stylesheet being read: once per text")
function lss_split(s: string, c: int) -> []string {
  let out = new []string
  var at = 0
  for i in 0 .. len(s) {
    if s[i] == c {
      push(out, s[at..i])
      at = i + 1
    }
  }
  push(out, s[at..len(s)])
  return out
}
# the imports' rules, then the file's own, ordered by specificity and otherwise as written
function sheet_of(f: UiFile) -> UiSheet {
  let sh = new UiSheet
  sh.rules = new []UiRule
  for i in 0 .. len(f.imp) {
    if f.imp[i].sheet != null {
      for k in 0 .. len(f.imp[i].sheet.rules) { sheet_add(sh, f.imp[i].sheet.rules[k]) }
    }
  }
  for k in 0 .. len(f.own) { sheet_add(sh, f.own[k]) }
  return sh
}
function sheet_add(sh: UiSheet, r: UiRule) -> void {
  push(sh.rules, r)
  var i = len(sh.rules) - 1
  while i > 0 and sh.rules[i - 1].spec > r.spec {
    sh.rules[i] = sh.rules[i - 1]
    i -= 1
  }
  sh.rules[i] = r
}

# one `key: value` into the rule: the key kept as read (a clean slice is its own words), the
# value parsed (its expression copies what it keeps), and the slices nothing keeps given back
function lss_decl_add(r: UiRule, d: string, colon: int, err: []string) -> void {
  let kr: string = d[0..colon]
  push(r.keys, tpl_words(kr))
  if not tpl_clean(kr) { unsafe { free(kr) } }
  let vr: string = d[colon + 1..len(d)]
  let vt = tpl_words(vr)
  push(r.vals, tpl_value(vt, err))
  unsafe {
    if not tpl_clean(vr) { free(vt) }
    free(vr)
  }
}