// MethodCallHandlerBox - Handle Method calls (MirCall with Method callee)
// Single Responsibility: Execute instance methods (e.g., array.length(), string.substring())

using selfhost.vm.boxes.result_box as Result
using selfhost.shared.common.string_helpers as StringHelpers
using selfhost.vm.hakorune-vm.value_manager as ValueManagerBox
using selfhost.vm.hakorune-vm.callee_parser as CalleeParserBox
using selfhost.vm.hakorune-vm.args_extractor as ArgsExtractorBox
using selfhost.vm.hakorune-vm.args_guard as ArgsGuardBox
using selfhost.vm.hakorune-vm.receiver_guard as ReceiverGuardBox
using selfhost.vm.hakorune-vm.json_field_extractor as JsonFieldExtractor
using selfhost.shared.json.core.json_cursor as JsonCursorBox
using selfhost.shared.host_bridge.host_bridge as HostBridge
using selfhost.vm.hakorune-vm.core_bridge_ops as CoreBridgeOps

static box MethodCallHandlerBox {
  // TTL: Delegation policy (Phase 20.17 — P1 audit complete)
  // - Delegated via CoreBridgeOps: Array(size/push/pop/get/set), Map(len/iterator/set/get)
  // - Local/HostBridge: string instance methods（substring/indexOf/lastIndexOf/dirname/join…）は
  //   文字列意味論の完全移行まで HostBridge に留める（20.18+ で段階移行予定）。
  //   正規化は最小限（length→size のみ）として drift を抑制する。
  // Handle Method call
  // mir_call_json: {"callee":{"type":"Method","receiver":X,"method":"name"},"args":[...]}
  // dst_reg: destination register (null if no return value)
  // regs: register MapBox
  // Returns: Result.Ok(0) or Result.Err(message)
  handle(mir_call_json, dst_reg, regs) {
    // Extract receiver ValueId from callee.receiver field
    local receiver_id = CalleeParserBox.extract_receiver(mir_call_json)
    if receiver_id == null {
      return Result.Err("method: receiver not found in callee")
    }

    // Extract method name from callee.method field
    local method_name = CalleeParserBox.extract_method(mir_call_json)
    if method_name == null {
      return Result.Err("method: method name not found in callee")
    }

    // Extract arguments from mir_call.args
    local args_array = ArgsExtractorBox.extract_and_load(mir_call_json, regs)
    local _g = ArgsGuardBox.ensure_no_nulls(args_array, method_name + "/" + StringHelpers.int_to_str(args_array.length()))
    if _g.is_Err() { return _g }

    // Build signature and guard
    local arg_count = args_array.length()
    local method_sig = method_name + "/" + StringHelpers.int_to_str(arg_count)
    // Load receiver and guard
    local receiver = ValueManagerBox.get(regs, receiver_id)
    local guard = ReceiverGuardBox.ensure_valid(receiver, method_sig, receiver_id)
    if guard.is_Err() { return guard }

    // Unified dispatch via HostBridge (Phase B):
    // Normalize a few well-known aliases to SSOT names (e.g., length -> size).
    local method_canon = method_name
    if method_canon == "length" { method_canon = "size" }

    // Core bridge handles collection metadata + semantics directly (Phase 20.16).
    // Delegate to CoreBridgeOps for Array/Map shortcuts to avoid drift.
    // TODO: Remove fallback once Core mir_call covers every method variant (size/push/pop/len/set/get).
    local core_shortcut = CoreBridgeOps.try_method_collection(method_canon, mir_call_json, args_array, dst_reg, regs, receiver_id)
    if core_shortcut != null {
      return core_shortcut
    }

    // Forward to HostBridge. PluginResolver performs the final resolution.
    local result_val = HostBridge.box_call(receiver, method_canon, args_array)


    // Store result in destination register
    if dst_reg != null {
      ValueManagerBox.set(regs, dst_reg, result_val)
    }

    return Result.Ok(0)
  }
}