// json_frag.hako — JSON v0 断片抽出ユーティリティ（Box）
// 責務: 文字列JSONから key:int / key:str を簡便に取り出す。
// 非責務: 実行・評価（構造検査やVM実行は他箱に委譲）。

using selfhost.shared.json.core.json_cursor as JsonCursorBox
using selfhost.shared.common.string_helpers as StringHelpers

static box JsonFragBox {
  // 基本ヘルパ
  index_of_from(hay, needle, pos) { return JsonCursorBox.index_of_from(hay, needle, pos) }
  read_digits(text, pos) { return StringHelpers.read_digits(text, pos) }
  _str_to_int(s) { return StringHelpers.to_i64(s) }

  // key に続く数値（最初の一致）を返す。見つからなければ null。
  get_int(seg, key) {
    local pat1 = "\"" + key + "\":"
    local p = me.index_of_from(seg, pat1, 0)
    if p >= 0 {
      local v = me.read_digits(seg, p + pat1.length())
      if v != "" { return me._str_to_int(v) }
    }
    return null
  }

  // key に続く "..." の文字列（最初の一致）を返す。見つからなければ空文字。
  get_str(seg, key) {
    local pat = "\"" + key + "\":\""
    local p = me.index_of_from(seg, pat, 0)
    if p >= 0 {
      local vstart = p + pat.length()              // start of value (right after opening quote)
      local vend = JsonCursorBox.scan_string_end(seg, vstart - 1)
      if vend > vstart { return seg.substring(vstart, vend) }
    }
    return ""
  }



  // Strict variants: emit an error when the key is missing
  get_int_strict(seg, key) {
    local v = me.get_int(seg, key)
    if v == null {
      print("[ERROR] Missing key: " + key)
    }
    return v
  }

  get_str_strict(seg, key) {
    local v = me.get_str(seg, key)
    if v == "" {
      print("[ERROR] Missing key: " + key)
    }
    return v
  }
  // ブロック0の instructions を丸ごと返す（配列の中身のみ返す）。
  block0_segment(mjson) {
    if mjson == null { return "" }
    // Find the instructions array start reliably
    local key = "\"instructions\":["
    local pk = mjson.indexOf(key)
    if pk < 0 { return "" }
    // '[' position
    local arr_bracket = pk + key.length() - 1
    // Use escape-aware scanner to find matching ']'
    local endp = JsonCursorBox.seek_array_end(mjson, arr_bracket)
    if endp < 0 { return "" }
    return mjson.substring(arr_bracket + 1, endp)
  }


  // Alias for legacy/buggy resolvers that drop underscores in method names.
  // Keep as a thin forwarder to preserve strict naming in source while
  // unblocking runtimes that accidentally call `block0segment`.
}