// Stage1UsingResolverBox — resolve `using` statements for Stage‑1 pipelines
// Responsibilities:
//   - Collect line-based using declarations via UsingCollectorBox.
//   - Resolve namespace targets against `nyash.toml` `[modules]` entries (fed via env).
//   - Read the referenced .hako files and return a concatenated prefix for Stage‑B.
//
// Env requirements:
//   - HAKO_STAGEB_MODULES_LIST: `name=path` entries joined by "|||".
//   - NYASH_ROOT: absolute path to repo root (for resolving relative paths).

using lang.compiler.parser.using.using_collector_box as UsingCollectorBox
using lang.compiler.parser.scan.parser_common_utils_box as ParserCommonUtilsBox
using selfhost.shared.json.utils.json_frag as JsonFragBox

static box Stage1UsingResolverBox {
  resolve_for_source(src) {
    // Shallow recursion guard to prevent accidental self-recursion in Stage‑1 using resolver.
    {
      local depth = env.get("HAKO_STAGEB_USING_DEPTH")
      if depth != null && ("" + depth) != "0" {
        print("[stageb/recursion] Stage1UsingResolverBox.resolve_for_source recursion detected")
        return ""
      }
      env.set("HAKO_STAGEB_USING_DEPTH", "1")
    }

    if src == null { return "" }
    local apply_flag = env.get("HAKO_STAGEB_APPLY_USINGS")
    if apply_flag != null && ("" + apply_flag) == "0" { return "" }

    local entries = me._collect_using_entries(src)
    if entries == null || entries.length() == 0 { return "" }

    local modules = me._build_module_map()
    local seen = new MapBox()
    local prefix = ""

    local i = 0
    local n = entries.length()
    loop(i < n) {
      local entry = entries.get(i)
      local name = "" + entry.get("name")
      if name == "" { i = i + 1  continue }

      local path = entry.get("path")
      if path == null || ("" + path) == "" {
        path = me._lookup_module_path(modules, name)
      } else {
        path = "" + path
      }
      if path == null || path == "" { i = i + 1  continue }

      local abs_path = me._abs_path(path)
      if abs_path == null || abs_path == "" { i = i + 1  continue }
      if seen.get(abs_path) == "1" { i = i + 1  continue }

      local code = me._read_file(abs_path)
      if code == null { i = i + 1  continue }

      seen.set(abs_path, "1")
      prefix = prefix + "\n" + code + "\n"
      i = i + 1
    }

    // Clear depth guard before returning
    env.set("HAKO_STAGEB_USING_DEPTH", "0")
    return prefix
  }

  // Collect entries from UsingCollectorBox JSON output.
  _collect_using_entries(src) {
    local json = UsingCollectorBox.collect(src)
    if json == null || json == "" || json == "[]" { return null }
    local out = new ArrayBox()
    local pos = 0
    local n = json.length()
    loop(pos < n) {
      local name_idx = JsonFragBox.index_of_from(json, "\"name\":\"", pos)
      if name_idx < 0 { break }
      local name = JsonFragBox.read_string_after(json, name_idx + 7)
      local obj_end = JsonFragBox.index_of_from(json, "}", name_idx)
      if obj_end < 0 { obj_end = n }

      local path = null
      local path_idx = JsonFragBox.index_of_from(json, "\"path\":\"", name_idx)
      if path_idx >= 0 && path_idx < obj_end {
        path = JsonFragBox.read_string_after(json, path_idx + 7)
      }

      local entry = new MapBox()
      entry.set("name", name)
      if path != null { entry.set("path", path) }
      out.push(entry)
      pos = obj_end + 1
    }
    return out
  }

  _build_module_map() {
    local map = new MapBox()
    local raw = env.get("HAKO_STAGEB_MODULES_LIST")
    if raw == null { return map }
    local str = "" + raw
    if str == "" { return map }

    local delim = "|||"
    local start = 0
    loop(true) {
      local next = ParserCommonUtilsBox.index_of(str, start, delim)
      local seg = ""
      if next >= 0 { seg = str.substring(start, next) } else { seg = str.substring(start, str.length()) }
      me._push_module_entry(map, seg)
      if next < 0 { break }
      start = next + delim.length()
    }
    return map
  }

  _push_module_entry(map, seg) {
    if seg == null { return }
    local line = ParserCommonUtilsBox.trim("" + seg)
    if line == "" { return }
    local eq_idx = ParserCommonUtilsBox.index_of(line, 0, "=")
    if eq_idx < 0 { return }
    local key = ParserCommonUtilsBox.trim(line.substring(0, eq_idx))
    local val = ParserCommonUtilsBox.trim(line.substring(eq_idx + 1, line.length()))
    if key == "" || val == "" { return }
    map.set(key, val)
  }

  _lookup_module_path(map, name) {
    if map == null { return null }
    local val = map.get(name)
    if val != null { return "" + val }
    return null
  }

  _abs_path(path) {
    if path == null { return null }
    local p = "" + path
    if p == "" { return null }
    if ParserCommonUtilsBox.starts_with(p, 0, "/") == 1 { return p }
    local root = env.get("NYASH_ROOT")
    if root == null || root == "" { return p }
    local base = "" + root
    if base == "" { return p }
    if base.substring(base.length() - 1, base.length()) == "/" { return base + p }
    return base + "/" + p
  }

  _read_file(path) {
    if path == null { return null }
    @fb = new FileBox()
    @ok = fb.open(path, "r")
    if ok != 1 { return null }
    @content = fb.read()
    fb.close()
    return content
  }
}

static box Stage1UsingResolverBoxMain { main(args) { return 0 } }