// no external using required for quick json_query (text-slicing)

static box Main {
  main() {
    // DEBUG toggle (manual runs only). Keep 0 for tests.
    local DEBUG = 0
    // Simple JSON query runner: evaluate a few (json, path) pairs and print results
    // Path grammar (subset):
    //   <path> := ('.' <ident> | '[' <digits> ']')*
    // Examples: .a.b[1], .c, [0]

    local cases = new ArrayBox()

    // Case 1
    local j1 = "{\"a\":{\"b\":[1,2,3]},\"c\":\"x\"}"
    cases.push(j1)
    cases.push(".a.b[1]")    // -> 2
    cases.push(j1)
    cases.push(".c")         // -> "x"
    cases.push(j1)
    cases.push(".a")         // -> {"b":[1,2,3]}
    cases.push(j1)
    cases.push(".a.b")       // -> [1,2,3]
    cases.push(j1)
    cases.push(".a.b[10]")   // -> null
    cases.push(j1)
    cases.push(".x")         // -> null
    cases.push(j1)
    cases.push(".a.b[0]")    // -> 1

    // Case 2
    local j2 = "[ {\"k\":\"v\"}, 10, null ]"
    cases.push(j2)
    cases.push("[0].k")      // -> "v"
    cases.push(j2)
    cases.push("[1]")        // -> 10
    cases.push(j2)
    cases.push("[2]")        // -> null
    cases.push(j2)
    cases.push("[3]")        // -> null (out of range)

    local i = 0
    loop(i < cases.length()) {
      local json_text = cases.get(i)
      local path = cases.get(i + 1)
      if DEBUG == 1 { print("[dbg] path=" + path) }
      // Parser-less path: slice JSON text directly for quick profile stability
      local out_text = this.eval_path_text(json_text, path)
      if out_text == null { print("null") } else { print(out_text) }
      i = i + 2
    }
    return 0
  }

  _int_to_str(n) {
    if n == 0 { return "0" }
    local v = n
    local out = ""
    local digits = "0123456789"
    loop (v > 0) {
      local d = v % 10
      local ch = digits.substring(d, d+1)
      out = ch + out
      v = v / 10
    }
    return out
  }

  // Evaluate a simple JSON path by slicing JSON text directly (no full parse)
  // Returns a JSON substring for the value or null if not found
  eval_path_text(json_text, path) {
    local DEBUG = 0  // set to 1 for ad-hoc debug
    local cur_text = json_text
    local i = 0
    loop(i < path.length()) {
      local ch = path.substring(i, i + 1)
      if DEBUG == 1 { print("[dbg] step ch=" + ch) }
      if ch == "." {
        // parse identifier
        i = i + 1
        if DEBUG == 1 { print("[dbg] after dot i=" + i + ", ch1=" + path.substring(i, i + 1)) }
        local start = i
        loop(i < path.length()) {
          local c = path.substring(i, i + 1)
          if DEBUG == 1 { print("[dbg] c=" + c) }
          if this.is_alnum(c) || c == "_" { i = i + 1 } else { break }
        }
        local key = path.substring(start, i)
        if DEBUG == 1 { print("[dbg] key=" + key) }
        if key.length() == 0 { return null }
        // Get value text directly; then reset window to that text
        local next_text = this.object_get_text(cur_text, 0, cur_text.length(), key)
        if DEBUG == 1 { if next_text == null { print("[dbg] obj miss") } else { print("[dbg] obj hit len=" + next_text.length()) } }
        if next_text == null { return null }
        cur_text = next_text
      } else {
        if ch == "[" {
          // parse index
          i = i + 1
          if DEBUG == 1 { print("[dbg] after [ i=" + i + ", ch1=" + path.substring(i, i + 1)) }
          local start = i
          loop(i < path.length() && this.is_digit(path.substring(i, i + 1))) { i = i + 1 }
          local idx_str = path.substring(start, i)
          if DEBUG == 1 { print("[dbg] idx_str=" + idx_str + ", next=" + path.substring(i, i + 1)) }
          if i >= path.length() || path.substring(i, i + 1) != "]" { return null }
          i = i + 1 // skip ']'
          local idx = this.parse_int(idx_str)
          if DEBUG == 1 { print("[dbg] idx=" + idx) }
          local next_text = this.array_get_text(cur_text, 0, cur_text.length(), idx)
          if DEBUG == 1 { if next_text == null { print("[dbg] arr miss idx=" + idx_str) } else { print("[dbg] arr hit len=" + next_text.length()) } }
          if next_text == null { return null }
          cur_text = next_text
        } else {
          return null
        }
      }
    }
    return cur_text
  }

  // Local helpers (avoid external using in app)
  is_digit(ch) {
    return ch == "0" || ch == "1" || ch == "2" || ch == "3" || ch == "4" || ch == "5" || ch == "6" || ch == "7" || ch == "8" || ch == "9"
  }
  is_alpha(ch) {
    // membership without using indexOf (avoid VoidBox.* risks)
    local letters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
    local i = 0
    loop(i < letters.length()) {
      if letters.substring(i, i+1) == ch { return true }
      i = i + 1
    }
    return false
  }
  is_alnum(ch) {
    return this.is_alpha(ch) || this.is_digit(ch)
  }
  parse_int(s) {
    local i = 0
    local neg = false
    if s.length() > 0 && s.substring(0,1) == "-" {
      neg = true
      i = 1
    }
    local acc = 0
    loop(i < s.length()) {
      local ch = s.substring(i, i + 1)
      if ! this.is_digit(ch) { break }
      // ch to digit
      // 0..9
      if ch == "0" { acc = acc * 10 + 0 }
      else { if ch == "1" { acc = acc * 10 + 1 }
      else { if ch == "2" { acc = acc * 10 + 2 }
      else { if ch == "3" { acc = acc * 10 + 3 }
      else { if ch == "4" { acc = acc * 10 + 4 }
      else { if ch == "5" { acc = acc * 10 + 5 }
      else { if ch == "6" { acc = acc * 10 + 6 }
      else { if ch == "7" { acc = acc * 10 + 7 }
      else { if ch == "8" { acc = acc * 10 + 8 }
      else { if ch == "9" { acc = acc * 10 + 9 } }}}}}}}}}
      i = i + 1
    }
    if neg { return 0 - acc } else { return acc }
  }
  // --- Minimal JSON slicing helpers (object/array) ---
  // Span utilities: represent [i,j) as "i:j" string to avoid method calls
  span_pack(i, j) { return this._int_to_str(i) + ":" + this._int_to_str(j) }
  span_unpack_i(sp) {
    // find ':' without using indexOf
    local i = 0
    local n = sp.length()
    loop(i < n) {
      if sp.substring(i, i+1) == ":" { break }
      i = i + 1
    }
    if i >= n { return 0 }
    return this.parse_int(sp.substring(0, i))
  }
  span_unpack_j(sp) {
    local i = 0
    local n = sp.length()
    loop(i < n) {
      if sp.substring(i, i+1) == ":" { break }
      i = i + 1
    }
    if i >= n { return 0 }
    return this.parse_int(sp.substring(i + 1, n))
  }
  // Find a key's value span within an object JSON slice [start,end)
  object_get_span(s, start, end, key) {
    local i = start
    if i < end && s.substring(i, i+1) == "{" { i = i + 1 } else { return null }
    loop(i < end) {
      i = this.skip_ws(s, i, end)
      if i >= end { return null }
      if s.substring(i, i+1) == "}" { return null }
      if s.substring(i, i+1) != "\"" { return null }
      local key_end = this.read_string_end(s, i, end)
      if key_end == -1 { return null }
      local key_text = s.substring(i+1, key_end-1)
      i = key_end
      i = this.skip_ws(s, i, end)
      if i >= end || s.substring(i, i+1) != ":" { return null }
      i = i + 1
      i = this.skip_ws(s, i, end)
      local vspan = this.read_value_span(s, i, end)
      if vspan == null { return null }
      if key_text == key { return vspan }
      i = this.span_unpack_j(vspan)
      i = this.skip_ws(s, i, end)
      if i < end && s.substring(i, i+1) == "," {
        i = i + 1
        continue
      } else {
        return null
      }
    }
    return null
  }

  // Return the value text for a key within an object slice, or null
  object_get_text(s, start, end, key) {
    local sp = this.object_get_span(s, start, end, key)
    if sp == null { return null }
    // Use the computed span directly (start,end) to avoid rescan drift
    local i0 = this.span_unpack_i(sp)
    local j0 = this.span_unpack_j(sp)
    return s.substring(i0, j0)
  }

  // Get the span of the idx-th element at top-level of an array slice [start,end)
  array_get_span(s, start, end, idx) {
    local i = start
    if i < end && s.substring(i, i+1) == "[" {
      i = i + 1
    } else {
      return null
    }
    local cur = 0
    local DEBUG = 0
    loop(i < end) {
      i = this.skip_ws(s, i, end)
      if i >= end { return null }
      if s.substring(i, i+1) == "]" { return null }
      local vspan = this.read_value_span(s, i, end)
      if DEBUG == 1 { print("[dbg] arr cur=" + cur + ", i=" + i + ", ch=" + s.substring(i, i+1)) }
      if vspan == null { return null }
      if DEBUG == 1 { print("[dbg] arr vspan=[" + this.span_unpack_i(vspan) + "," + this.span_unpack_j(vspan) + "]") }
      if cur == idx { return vspan }
      i = this.span_unpack_j(vspan)
      i = this.skip_ws(s, i, end)
      if i < end && s.substring(i, i+1) == "," {
        i = i + 1
        cur = cur + 1
        continue
      } else {
        return null
      }
    }
    return null
  }

  // Return the text of idx-th element within an array slice, or null
  array_get_text(s, start, end, idx) {
    // DEBUG
    // print("[dbg] arr_text head=" + s.substring(start, start+1) + ", len=" + (end - start))
    local sp = this.array_get_span(s, start, end, idx)
    if sp == null { return null }
    local i0 = this.span_unpack_i(sp)
    local j0 = this.span_unpack_j(sp)
    return s.substring(i0, j0)
  }

  // Read a JSON value span starting at i; returns [start,end)
  read_value_span(s, i, end) {
    if i >= end { return null }
    local ch = s.substring(i, i+1)
    if ch == "\"" {
      local j = this.read_string_end(s, i, end)
      if j == -1 { return null } else { return this.span_pack(i, j) }
    }
    if ch == "{" {
      local j = this.matching_brace(s, i, end, "{", "}")
      if j == -1 { return null } else { return this.span_pack(i, j) }
    }
    if ch == "[" {
      local j = this.matching_brace(s, i, end, "[", "]")
      if j == -1 { return null } else { return this.span_pack(i, j) }
    }
    // number/bool/null: read until comma or closing
    local j = i
    loop(j < end) {
      local c = s.substring(j, j+1)
      if c == "," || c == "}" || c == "]" || this.is_ws_char(c) { break }
      j = j + 1
    }
    return this.span_pack(i, j)
  }

  // Find end index (exclusive) of a JSON string literal starting at i ('"')
  read_string_end(s, i, end) {
    local j = i + 1
    loop(j < end) {
      local c = s.substring(j, j+1)
      if c == "\\" {
        j = j + 2
        continue
      }
      if c == "\"" { return j + 1 }
      j = j + 1
    }
    return -1
  }

  // Match paired braces/brackets with simple string-awareness; returns end index (exclusive)
  matching_brace(s, i, end, open, close) {
    local depth = 0
    local j = i
    loop(j < end) {
      local c = s.substring(j, j+1)
      if c == "\"" {
        j = this.read_string_end(s, j, end)
        if j == -1 { return -1 }
        continue
      }
      if c == open {
        depth = depth + 1
      } else {
        if c == close {
          depth = depth - 1
          if depth == 0 { return j + 1 }
        }
      }
      j = j + 1
    }
    return -1
  }

  // Whitespace utilities
  skip_ws(s, i, end) {
    local j = i
    loop(j < end && this.is_ws_char(s.substring(j, j+1))) { j = j + 1 }
    return j
  }
  is_ws_char(ch) { return ch == " " || ch == "\t" || ch == "\n" || ch == "\r" }
  // Note: normalization now lives in JsonNode (object_get/array_get)
}