feat(functions): add lookup and reference functions

lib/src/functions/lookup.dart

@@ -0,0 +1,142 @@
+import '../ast.dart';
+import '../evaluator.dart';
+import '../values.dart';
+import 'helpers.dart';
+
+void registerLookup(Map<String, CellFunction> registry) {
+  registry['INDEX'] = (args, ctx) {
+    arity(args, 2, 3);
+    final area = ctx.resolveArea(args[0]);
+    if (args.length == 2) {
+      final index = intArg(args[1], ctx);
+      if (index < 1 || index > area.cells.length) {
+        throw const EvalException(ErrorValue(ErrorKind.ref));
+      }
+      return area.cells[index - 1];
+    }
+    final rowNum = intArg(args[1], ctx);
+    final colNum = intArg(args[2], ctx);
+    if (rowNum < 1 || rowNum > area.rows || colNum < 1 || colNum > area.cols) {
+      throw const EvalException(ErrorValue(ErrorKind.ref));
+    }
+    return area.at(rowNum - 1, colNum - 1);
+  };
+
+  registry['MATCH'] = (args, ctx) {
+    arity(args, 2, 3);
+    final needle = ctx.eval(args[0]);
+    final haystack = ctx.resolveArea(args[1]).cells;
+    final matchType = args.length > 2 ? intArg(args[2], ctx) : 1;
+    final position = _matchPosition(needle, haystack, matchType, ctx);
+    if (position < 0) throw const EvalException(ErrorValue(ErrorKind.na));
+    return NumberValue((position + 1).toDouble());
+  };
+
+  registry['VLOOKUP'] = (args, ctx) {
+    arity(args, 3, 4);
+    final key = ctx.eval(args[0]);
+    final area = ctx.resolveArea(args[1]);
+    final colIndex = intArg(args[2], ctx);
+    final approximate = args.length < 4 || boolArg(args[3], ctx);
+    if (colIndex < 1 || colIndex > area.cols) {
+      throw const EvalException(ErrorValue(ErrorKind.ref));
+    }
+    final firstColumn = [for (var row = 0; row < area.rows; row++) area.at(row, 0)];
+    final row = _matchPosition(key, firstColumn, approximate ? 1 : 0, ctx);
+    if (row < 0) throw const EvalException(ErrorValue(ErrorKind.na));
+    return area.at(row, colIndex - 1);
+  };
+
+  registry['HLOOKUP'] = (args, ctx) {
+    arity(args, 3, 4);
+    final key = ctx.eval(args[0]);
+    final area = ctx.resolveArea(args[1]);
+    final rowIndex = intArg(args[2], ctx);
+    final approximate = args.length < 4 || boolArg(args[3], ctx);
+    if (rowIndex < 1 || rowIndex > area.rows) {
+      throw const EvalException(ErrorValue(ErrorKind.ref));
+    }
+    final firstRow = [for (var col = 0; col < area.cols; col++) area.at(0, col)];
+    final col = _matchPosition(key, firstRow, approximate ? 1 : 0, ctx);
+    if (col < 0) throw const EvalException(ErrorValue(ErrorKind.na));
+    return area.at(rowIndex - 1, col);
+  };
+
+  registry['LOOKUP'] = (args, ctx) {
+    arity(args, 2, 3);
+    final key = ctx.eval(args[0]);
+    final search = ctx.resolveArea(args[1]).cells;
+    final result = args.length == 3 ? ctx.resolveArea(args[2]).cells : search;
+    final position = _matchPosition(key, search, 1, ctx);
+    if (position < 0 || position >= result.length) {
+      throw const EvalException(ErrorValue(ErrorKind.na));
+    }
+    return result[position];
+  };
+
+  registry['CHOOSE'] = (args, ctx) {
+    arity(args, 2);
+    final index = intArg(args[0], ctx);
+    if (index < 1 || index >= args.length) {
+      throw const EvalException(ErrorValue(ErrorKind.value));
+    }
+    return ctx.eval(args[index]);
+  };
+
+  registry['ROWS'] = (args, ctx) {
+    arity(args, 1, 1);
+    return NumberValue(ctx.resolveArea(args[0]).rows.toDouble());
+  };
+
+  registry['COLUMNS'] = (args, ctx) {
+    arity(args, 1, 1);
+    return NumberValue(ctx.resolveArea(args[0]).cols.toDouble());
+  };
+
+  registry['ROW'] = (args, ctx) {
+    arity(args, 1, 1);
+    final node = args[0];
+    if (node is RefNode) return NumberValue((node.address.row + 1).toDouble());
+    if (node is RangeNode) return NumberValue((node.start.row + 1).toDouble());
+    throw const EvalException(ErrorValue(ErrorKind.value));
+  };
+
+  registry['COLUMN'] = (args, ctx) {
+    arity(args, 1, 1);
+    final node = args[0];
+    if (node is RefNode) return NumberValue((node.address.col + 1).toDouble());
+    if (node is RangeNode) return NumberValue((node.start.col + 1).toDouble());
+    throw const EvalException(ErrorValue(ErrorKind.value));
+  };
+}
+
+int _matchPosition(CellValue needle, List<CellValue> haystack, int matchType, EvalContext ctx) {
+  if (matchType == 0) {
+    for (var i = 0; i < haystack.length; i++) {
+      if (haystack[i] is! ErrorValue && ctx.compare(needle, haystack[i]) == 0) return i;
+    }
+    return -1;
+  }
+  if (matchType > 0) {
+    var best = -1;
+    for (var i = 0; i < haystack.length; i++) {
+      if (haystack[i] is ErrorValue) continue;
+      if (ctx.compare(haystack[i], needle) <= 0) {
+        best = i;
+      } else {
+        break;
+      }
+    }
+    return best;
+  }
+  var best = -1;
+  for (var i = 0; i < haystack.length; i++) {
+    if (haystack[i] is ErrorValue) continue;
+    if (ctx.compare(haystack[i], needle) >= 0) {
+      best = i;
+    } else {
+      break;
+    }
+  }
+  return best;
+}