// Copyright (c) 2020, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

import 'dart:ffi';
import 'dart:io';

import 'c_types.dart';
import 'structs_by_value_tests_configuration.dart';
import 'utils.dart';

/// The test type determines how to convert the arguments into return values
/// such that the caller knows what to check.
enum TestType {
  /// Tested by getting all the individual fields out of the structs and
  /// summing their values.
  structArguments,

  /// Tested by passing assigning the arguments to the struct fields.
  structReturn,

  /// Tested by returning the struct passed in.
  structReturnArgument,
}

extension on FunctionType {
  TestType get testType {
    if (arguments.containsComposites && returnValue is FundamentalType) {
      return TestType.structArguments;
    }
    if (returnValue is CompositeType && argumentTypes.contains(returnValue)) {
      return TestType.structReturnArgument;
    }
    if (returnValue is StructType) {
      if (arguments.length == (returnValue as CompositeType).members.length) {
        return TestType.structReturn;
      }
    }
    if (returnValue is UnionType) {
      if (arguments.length == 1) {
        return TestType.structReturn;
      }
    }

    // No structs, sum the arguments as well.
    return TestType.structArguments;
  }
}

/// We use the class structure as an algebraic data type in order to keep the
/// relevant parts of the code generation closer together.
extension on CType {
  /// The part of the cout expression after `std::cout` and before the `;`.
  String coutExpression(String variableName) {
    switch (this.runtimeType) {
      case FundamentalType:
        if (this == uint8 || this == int8) {
          return "<< static_cast<int>($variableName)";
        }
        return "<< $variableName";

      case StructType:
        final this_ = this as StructType;
        return this_.members.coutExpression("$variableName.");

      case UnionType:
        final this_ = this as UnionType;
        return this_.members.take(1).toList().coutExpression("$variableName.");

      case FixedLengthArrayType:
        final this_ = this as FixedLengthArrayType;
        final indices = [for (var i = 0; i < this_.length; i += 1) i];

        String result = '<< "["';
        result += indices
            .map((i) => this_.elementType.coutExpression("$variableName[$i]"))
            .join('<< ", "');
        result += '<< "]"';
        return result.trimCouts();
    }

    throw Exception("Not implemented for ${this.runtimeType}");
  }

  /// A statement recursively outputting all members.
  String coutStatement(String variableName) {
    final coutExpr = this.coutExpression(variableName);
    return 'std::cout << "$variableName = " $coutExpr << "\\n";';
  }
}

extension on List<Member> {
  /// The part of the cout expression after `std::cout` and before the `;`.
  String coutExpression([String namePrefix = ""]) {
    String result = '<< "("';
    result += this
        .map((m) => m.type.coutExpression("$namePrefix${m.name}"))
        .join('<< ", "');
    result += '<< ")"';
    return result.trimCouts();
  }
}

extension on CType {
  /// A list of statements adding all members recursively to `result`.
  ///
  /// Both valid in Dart and C.
  String addToResultStatements(String variableName) {
    switch (this.runtimeType) {
      case FundamentalType:
        final this_ = this as FundamentalType;
        final boolToInt = this_.isBool ? ' ? 1 : 0' : '';
        return "  result += $variableName$boolToInt;\n";

      case StructType:
        final this_ = this as StructType;
        return this_.members.addToResultStatements("$variableName.");

      case UnionType:
        final this_ = this as UnionType;
        final member = this_.members.first;
        return member.type
            .addToResultStatements("$variableName.${member.name}");

      case FixedLengthArrayType:
        final this_ = this as FixedLengthArrayType;
        final indices = [for (var i = 0; i < this_.length; i += 1) i];
        return indices
            .map((i) =>
                this_.elementType.addToResultStatements("$variableName[$i]"))
            .join();
    }

    throw Exception("Not implemented for ${this.runtimeType}");
  }
}

extension on List<Member> {
  /// A list of statements adding all members recursively to `result`.
  ///
  /// Both valid in Dart and C.
  String addToResultStatements([String namePrefix = ""]) {
    return map((m) => m.type.addToResultStatements("$namePrefix${m.name}"))
        .join();
  }
}

extension on CType {
  /// A list of statements recursively assigning all members with [a].
  ///
  /// Both valid in Dart and C.
  String assignValueStatements(ArgumentValueAssigner a, String variableName) {
    switch (this.runtimeType) {
      case FundamentalType:
        final this_ = this as FundamentalType;
        return "  $variableName = ${a.nextValue(this_)};\n";

      case StructType:
        final this_ = this as StructType;
        return this_.members.assignValueStatements(a, "$variableName.");

      case UnionType:
        final this_ = this as UnionType;
        final member = this_.members.first;
        return member.type
            .assignValueStatements(a, "$variableName.${member.name}");

      case FixedLengthArrayType:
        final this_ = this as FixedLengthArrayType;
        final indices = [for (var i = 0; i < this_.length; i += 1) i];
        return indices
            .map((i) =>
                this_.elementType.assignValueStatements(a, "$variableName[$i]"))
            .join();
    }

    throw Exception("Not implemented for ${this.runtimeType}");
  }

  /// A list of statements recursively coping all members from [source].
  ///
  /// Both valid in Dart and C.
  String copyValueStatements(String source, String destination) {
    switch (this.runtimeType) {
      case FundamentalType:
        return "$destination = $source;\n";

      case StructType:
        final this_ = this as StructType;
        return this_.members.copyValueStatements("$source.", "$destination.");
    }

    throw Exception("Not implemented for ${this.runtimeType}");
  }
}

extension on List<Member> {
  /// A list of statements recursively assigning all members with [a].
  ///
  /// Both valid in Dart and C.
  String assignValueStatements(ArgumentValueAssigner a,
      [String namePrefix = ""]) {
    return map((m) => m.type.assignValueStatements(a, "$namePrefix${m.name}"))
        .join();
  }

  /// A list of statements recursively coping all members from [source].
  ///
  /// Both valid in Dart and C.
  String copyValueStatements([sourcePrefix = "", destinationPrefix = ""]) {
    return map((m) => m.type.copyValueStatements(
        "$sourcePrefix${m.name}", "$destinationPrefix${m.name}")).join();
  }
}

/// A helper class that assigns values to fundamental types.
///
/// Also keeps track of a sum of all values, to be used for testing the result.
class ArgumentValueAssigner {
  int i = 1;
  int sum = 0;
  String nextValue(FundamentalType type) {
    int argumentValue = i;
    i++;
    if (type.isBool) {
      argumentValue = argumentValue % 2;
    }
    if (type.isSigned && i % 2 == 0) {
      argumentValue = -argumentValue;
    }
    sum += argumentValue;
    if (type.isFloatingPoint) {
      return argumentValue.toDouble().toString();
    } else if (type.isInteger) {
      return argumentValue.toString();
    } else if (type.isBool) {
      return argumentValue == 1 ? 'true' : 'false';
    }
    throw 'Unknown type $type';
  }

  String sumValue(FundamentalType type) {
    if (type.isFloatingPoint) {
      return sum.toDouble().toString();
    } else {
      return sum.toString();
    }
  }
}

extension on CType {
  /// A list of Dart statements recursively allocating all members.
  String dartAllocateStatements(String variableName) {
    switch (this.runtimeType) {
      case FundamentalType:
        return "  ${dartType} ${variableName};\n";

      case StructType:
      case UnionType:
        return """
  final ${variableName}Pointer = calloc<$dartType>();
  final ${dartType} ${variableName} = ${variableName}Pointer.ref;
  """;
    }

    throw Exception("Not implemented for ${this.runtimeType}");
  }

  /// A list of Dart statements allocating as zero or nullptr.
  String dartAllocateZeroStatements(String variableName,
      {bool structsAsPointers = false}) {
    switch (this.runtimeType) {
      case FundamentalType:
        final this_ = this as FundamentalType;
        if (this_.isInteger) {
          return "${dartType} ${variableName} = 0;\n";
        }
        if (this_.isFloatingPoint) {
          return "${dartType} ${variableName} = 0.0;\n";
        }
        if (this_.isBool) {
          return "${dartType} ${variableName} = false;\n";
        }
        throw 'Unknown type $this_';

      case StructType:
      case UnionType:
        if (structsAsPointers) {
          return "Pointer<${dartType}> ${variableName}Pointer = nullptr;\n";
        } else {
          return "${dartType} ${variableName} = Pointer<${dartType}>.fromAddress(0).ref;\n";
        }
    }

    throw Exception("Not implemented for ${this.runtimeType}");
  }
}

extension on List<Member> {
  /// A list of Dart statements recursively allocating all members.
  String dartAllocateStatements([String namePrefix = ""]) {
    return map((m) => m.type.dartAllocateStatements("$namePrefix${m.name}"))
        .join();
  }

  /// A list of Dart statements as zero or nullptr.
  String dartAllocateZeroStatements(String namePrefix) {
    return map((m) => m.type.dartAllocateZeroStatements("$namePrefix${m.name}"))
        .join();
  }
}

extension on CType {
  /// A list of Dart statements recursively freeing all members.
  String dartFreeStatements(String variableName) {
    switch (this.runtimeType) {
      case FundamentalType:
        return "";

      case StructType:
      case UnionType:
        return "calloc.free(${variableName}Pointer);\n";
    }

    throw Exception("Not implemented for ${this.runtimeType}");
  }
}

extension on List<Member> {
  /// A list of Dart statements recursively freeing all members.
  String dartFreeStatements([String namePrefix = ""]) {
    return map((m) => m.type.dartFreeStatements("$namePrefix${m.name}")).join();
  }
}

extension on CType {
  /// A list of C statements recursively allocating all members.
  String cAllocateStatements(String variableName) {
    switch (this.runtimeType) {
      case FundamentalType:
        return "${cType} ${variableName};\n";
      case StructType:
      case UnionType:
        return "${cType} ${variableName} = {};\n";
    }

    throw Exception("Not implemented for ${this.runtimeType}");
  }
}

extension on List<Member> {
  /// A list of C statements recursively allocating all members.
  String cAllocateStatements([String namePrefix = ""]) {
    return map((m) => m.type.cAllocateStatements("$namePrefix${m.name}"))
        .join();
  }
}

extension on CType {
  /// A list of Dart statements recursively checking all members.
  String dartExpectsStatements(String expected, String actual) {
    switch (this.runtimeType) {
      case FundamentalType:
        final this_ = this as FundamentalType;
        if (this_.isInteger) {
          return "Expect.equals(${expected}, ${actual});";
        }
        if (this_.isFloatingPoint) {
          return "Expect.approxEquals(${expected}, ${actual});";
        }
        if (this_.isBool) {
          return "Expect.equals(${expected} % 2 != 0, ${actual});";
        }
        throw 'Unexpected type $this_';

      case StructType:
        final this_ = this as StructType;
        return this_.members.dartExpectsStatements("$expected.", "$actual.");

      case FixedLengthArrayType:
        final this_ = this as FixedLengthArrayType;
        return """
for (int i = 0; i < ${this_.length}; i++){
  ${this_.elementType.dartExpectsStatements("$expected[i]", "$actual[i]")}
}
""";
    }

    throw Exception("Not implemented for ${this.runtimeType}");
  }
}

extension on List<Member> {
  /// A list of Dart statements recursively checking all members.
  String dartExpectsStatements(
      [String expectedPrefix = "", String actualPrefix = ""]) {
    return map((m) => m.type.dartExpectsStatements(
        "$expectedPrefix${m.name}", "$actualPrefix${m.name}")).join();
  }
}

extension on CType {
  /// A list of C statements recursively checking all members.
  String cExpectsStatements(String expected, String actual) {
    switch (this.runtimeType) {
      case FundamentalType:
        final this_ = this as FundamentalType;
        if (this_.isInteger || this_.isBool) {
          return "CHECK_EQ(${expected}, ${actual});";
        }
        assert(this_.isFloatingPoint);
        return "CHECK_APPROX(${expected}, ${actual});";

      case StructType:
        final this_ = this as StructType;
        return this_.members.cExpectsStatements("$expected.", "$actual.");

      case FixedLengthArrayType:
        final this_ = this as FixedLengthArrayType;
        return """
for (intptr_t i = 0; i < ${this_.length}; i++){
  ${this_.elementType.cExpectsStatements("$expected[i]", "$actual[i]")}
}
""";
    }

    throw Exception("Not implemented for ${this.runtimeType}");
  }

  /// A list of C statements recursively checking all members for zero.
  String cExpectsZeroStatements(String actual) {
    switch (this.runtimeType) {
      case FundamentalType:
        final this_ = this as FundamentalType;
        if (this_.isInteger || this_.isBool) {
          return "CHECK_EQ(0, ${actual});";
        }
        assert(this_.isFloatingPoint);
        return "CHECK_APPROX(0.0, ${actual});";

      case StructType:
        final this_ = this as StructType;
        return this_.members.cExpectsZeroStatements("$actual.");

      case FixedLengthArrayType:
        final this_ = this as FixedLengthArrayType;
        return """
for (intptr_t i = 0; i < ${this_.length}; i++){
  ${this_.elementType.cExpectsZeroStatements("$actual[i]")}
}
""";
    }

    throw Exception("Not implemented for ${this.runtimeType}");
  }
}

extension on List<Member> {
  /// A list of C statements recursively checking all members.
  String cExpectsStatements(
      [String expectedPrefix = "", String actualPrefix = ""]) {
    return map((m) => m.type.cExpectsStatements(
        "$expectedPrefix${m.name}", "$actualPrefix${m.name}")).join();
  }

  /// A list of C statements recursively checking all members for zero.
  String cExpectsZeroStatements([String actualPrefix = ""]) {
    return map((m) => m.type.cExpectsZeroStatements("$actualPrefix${m.name}"))
        .join();
  }
}

extension on CType {
  /// Expression denoting the first FundamentalType field.
  ///
  /// Both valid in Dart and C.
  String firstArgumentName(String variableName) {
    switch (this.runtimeType) {
      case FundamentalType:
        return variableName;

      case StructType:
      case UnionType:
        final this_ = this as CompositeType;
        return this_.members.firstArgumentName("$variableName.");

      case FixedLengthArrayType:
        final this_ = this as FixedLengthArrayType;
        return this_.elementType.firstArgumentName("$variableName[0]");
    }

    throw Exception("Not implemented for ${this.runtimeType}");
  }
}

extension on List<Member> {
  /// Expression denoting the first FundamentalType field.
  ///
  /// Both valid in Dart and C.
  String firstArgumentName([String prefix = ""]) {
    return this[0].type.firstArgumentName("$prefix${this[0].name}");
  }
}

extension CompositeTypeGenerator on CompositeType {
  String dartClass() {
    final self = this;
    final packingAnnotation = (self is StructType) && self.hasPacking
        ? "@Packed(${self.packing})"
        : "";
    String dartFields = "";
    for (final member in members) {
      dartFields += "${member.dartStructField()}\n\n";
    }
    String toStringBody = members.map((m) {
      if (m.type is FixedLengthArrayType) {
        int dimensionNumber = 0;
        String inlineFor = "";
        String read = m.name;
        String closing = "";
        for (final dimension in (m.type as FixedLengthArrayType).dimensions) {
          final i = "i$dimensionNumber";
          inlineFor += "[for (var $i = 0; $i < $dimension; $i += 1)";
          read += "[$i]";
          closing += "]";
          dimensionNumber++;
        }
        return "\$\{$inlineFor $read $closing\}";
      }
      return "\$\{${m.name}\}";
    }).join(", ");
    return """
    $packingAnnotation
    final class $name extends $dartSuperClass {
      $dartFields

      String toString() => "($toStringBody)";
    }
    """;
  }

  String get cDefinition {
    final self = this;
    final packingPragmaPush = (self is StructType) && self.hasPacking
        ? "#pragma pack(push, ${self.packing})"
        : "";
    final packingPragmaPop =
        (self is StructType) && self.hasPacking ? "#pragma pack(pop)" : "";

    String cFields = "";
    for (final member in members) {
      cFields += "  ${member.cStructField}\n";
    }
    return """
    $packingPragmaPush
    $cKeyword $name {
      $cFields
    };
    $packingPragmaPop

    """;
  }
}

extension on FunctionType {
  String dartCallCode({required bool isLeaf, required bool isNative}) {
    final a = ArgumentValueAssigner();
    final assignValues = arguments.assignValueStatements(a);
    final argumentFrees = arguments.dartFreeStatements();

    final argumentNames = arguments.map((e) => e.name).join(", ");

    String expects;
    switch (testType) {
      case TestType.structArguments:
        // Check against sum value.
        final expectedResult = a.sumValue(returnValue as FundamentalType);
        expects = returnValue.dartExpectsStatements(expectedResult, "result");
        break;
      case TestType.structReturn:
        // Check against input arguments.
        expects = arguments.dartExpectsStatements("", "result.");
        break;
      case TestType.structReturnArgument:
        expects = returnValue.dartExpectsStatements(
            structReturnArgument.name, "result");
        break;
    }

    var namePostfix = isNative ? "Native" : "";
    namePostfix += isLeaf ? "Leaf" : "";
    return """

${isNative ? '''
@Native<$dartCType>(symbol: '$cName'${isLeaf ? ", isLeaf:true" : ""})
external ${returnValue.dartType} $dartName$namePostfix(${arguments.map((m) => '${m.type.dartType} ${m.name}').join(', ')});
''' : '''
final $dartName$namePostfix =
  ffiTestFunctions.lookupFunction<$dartCType, $dartType>(
      "$cName"${isLeaf ? ", isLeaf:true" : ""});
'''}
${reason.makeDartDocComment()}
void $dartTestName$namePostfix() {
${arguments.dartAllocateStatements()}
${assignValues}

  final result = $dartName$namePostfix($argumentNames);

  print("result = \$result");

  $expects

  $argumentFrees
}
    """;
  }

  String dartCallbackCode() {
    final argumentString =
        arguments.map((a) => "${a.type.dartType} ${a.name}").join(", ");

    final prints = arguments.map((a) => "\$\{${a.name}\}").join(", ");

    bool structsAsPointers = false;
    String assignReturnGlobal = "";
    String buildReturnValue = "";
    String returnValueType = returnValue.dartType;
    String result = 'result';
    if (returnValueType == 'bool') {
      // We can't sum a bool;
      returnValueType = 'int';
      result = 'result % 2 != 0';
    }

    switch (testType) {
      case TestType.structArguments:
        // Sum all input values.

        buildReturnValue = """
  $returnValueType result = 0;

${arguments.addToResultStatements('${dartName}_')}
  """;
        assignReturnGlobal = "${dartName}Result = $result;";
        break;
      case TestType.structReturn:
        // Allocate a struct.
        buildReturnValue = """
  final resultPointer = calloc<${returnValue.dartType}>();
  final result = resultPointer.ref;

  ${arguments.copyValueStatements("${dartName}_", "result.")}
  """;
        assignReturnGlobal = "${dartName}ResultPointer = resultPointer;";
        structsAsPointers = true;
        break;
      case TestType.structReturnArgument:
        buildReturnValue = """
  ${returnValue.cType} result = ${dartName}_${structReturnArgument.name};
  """;
        assignReturnGlobal = "${dartName}Result = result;";
        break;
    }

    final globals = arguments.dartAllocateZeroStatements("${dartName}_");

    final copyToGlobals =
        arguments.map((a) => '${dartName}_${a.name} = ${a.name};').join("\n  ");

    // Simulate assigning values the same way as in C, so that we know what the
    // final return value should be.
    final a = ArgumentValueAssigner();
    arguments.assignValueStatements(a);
    String afterCallbackExpects = "";
    String afterCallbackFrees = "";
    switch (testType) {
      case TestType.structArguments:
        // Check that the input structs are still available.
        // Check against sum value.
        final expectedResult = a.sumValue(returnValue as FundamentalType);
        afterCallbackExpects =
            returnValue.dartExpectsStatements(expectedResult, "result");
        break;
      case TestType.structReturn:
        // We're passing allocating structs in [buildReturnValue].
        afterCallbackFrees =
            returnValue.dartFreeStatements("${dartName}Result");
        break;
      case TestType.structReturnArgument:
        break;
    }
    return """
typedef ${cName}Type = $dartCType;

// Global variables to be able to test inputs after callback returned.
$globals

// Result variable also global, so we can delete it after the callback.
${returnValue.dartAllocateZeroStatements("${dartName}Result", structsAsPointers: structsAsPointers)}

${returnValue.dartType} ${dartName}CalculateResult() {
$buildReturnValue

  $assignReturnGlobal

  return $result;
}

${reason.makeDartDocComment()}
${returnValue.dartType} $dartName($argumentString) {
  print("$dartName($prints)");

  // Possibly throw.
  if (${arguments.firstArgumentName()} == $throwExceptionValue ||
      ${arguments.firstArgumentName()} == $returnNullValue) {
    print("throwing!");
    throw Exception("$cName throwing on purpose!");
  }

  $copyToGlobals

  final result = ${dartName}CalculateResult();

  print("result = \$result");

  return result;
}

void ${dartName}AfterCallback() {
  $afterCallbackFrees

  final result = ${dartName}CalculateResult();

  print("after callback result = \$result");

  $afterCallbackExpects

  $afterCallbackFrees
}

""";
  }

  String dartCallbackTestConstructor({required bool isNativeCallable}) {
    String exceptionalPrefix = isNativeCallable ? "exceptionalReturn: " : "";
    String exceptionalReturn = "";
    if (returnValue is FundamentalType) {
      final returnValue_ = returnValue as FundamentalType;
      if (returnValue_.isFloatingPoint) {
        exceptionalReturn = ", ${exceptionalPrefix}0.0";
      } else if (returnValue_.isInteger) {
        exceptionalReturn = ", ${exceptionalPrefix}0";
      } else if (returnValue_.isBool) {
        exceptionalReturn = ", ${exceptionalPrefix}false";
      } else {
        throw 'Unexpected type $returnValue_';
      }
    }
    final T = '${cName}Type';
    final constructor = isNativeCallable
        ? 'NativeCallable<$T>.isolateLocal'
        : 'Pointer.fromFunction<$T>';
    return """
  CallbackTest.withCheck("$cName",
    $constructor($dartName$exceptionalReturn),
    ${dartName}AfterCallback),
""";
  }

  String dartNativeCallableListenerCode({required bool isAsync}) {
    final argumentString =
        arguments.map((a) => "${a.type.dartType} ${a.name}").join(", ");
    final prints = arguments.map((a) => "\$\{${a.name}\}").join(", ");

    // The type of the async callback is the same as this FunctionType, but with
    // a void return type.
    final callbackType =
        FunctionType(argumentTypes, void_, reason, varArgsIndex: varArgsIndex);

    final a = ArgumentValueAssigner();
    arguments.assignValueStatements(a);
    final expectedResult = a.sumValue(int64);

    return """
typedef ${cName}Type = ${callbackType.dartCType};

// Global variable that stores the result.
final ${cName}Result = Completer<double>();

${reason.makeDartDocComment()}
void $dartName($argumentString) {
  print("$dartName($prints)");

  double result = 0;

${arguments.addToResultStatements()}

  print("result = \$result");
  ${cName}Result.complete(result);
}

Future<void> ${dartName}AfterCallback() async {
  final result = await ${cName}Result.future;
  print("after callback result = \$result");
  Expect.approxEquals($expectedResult, result);
}

""";
  }

  String dartNativeCallableListenerTestConstructor({required bool isAsync}) {
    final T = '${cName}Type';
    final constructor =
        isAsync ? 'NativeCallable<$T>.listener' : 'Pointer.fromFunction<$T>';
    return """
  AsyncCallbackTest("$cName",
    $constructor($dartName),
    ${dartName}AfterCallback),
""";
  }

  String get cCallCode {
    String body = "";
    String returnValueType = returnValue.cType;
    String returnStatement = 'return result;';
    if (returnValueType == 'bool') {
      // We can't sum in a bool.
      returnValueType = 'uint64_t';
      returnStatement = 'return result % 2 != 0;';
    }
    switch (testType) {
      case TestType.structArguments:
        body = """
        $returnValueType result = 0;

        ${arguments.addToResultStatements()}
        """;
        break;
      case TestType.structReturn:
        body = """
        $returnValueType result = {};

        ${arguments.copyValueStatements("", "result.")}
        """;
        break;
      case TestType.structReturnArgument:
        body = """
        $returnValueType result = ${structReturnArgument.name};
        """;
        break;
    }

    final argumentString = [
      for (final argument in arguments.take(varArgsIndex ?? arguments.length))
        "${argument.type.cType} ${argument.name}",
      if (varArgsIndex != null) "...",
    ].join(", ");

    final varArgUnpackArguments = [
      for (final argument in arguments.skip(varArgsIndex ?? arguments.length))
        "  ${argument.type.cType} ${argument.name} = va_arg(var_args, ${argument.type.cType});",
    ].join("\n");

    String varArgsUnpack = '';
    if (varArgsIndex != null) {
      varArgsUnpack = """
  va_list var_args;
  va_start(var_args, ${arguments[varArgsIndex! - 1].name});
$varArgUnpackArguments
  va_end(var_args);
""";
    }

    return """
// Used for testing structs and unions by value.
${reason.makeCComment()}
DART_EXPORT ${returnValue.cType} $cName($argumentString) {
$varArgsUnpack

  std::cout << "$cName" ${arguments.coutExpression()} << "\\n";

  $body

  ${returnValue.coutStatement("result")}

  $returnStatement
}

    """;
  }

  String get cCallbackCode {
    final a = ArgumentValueAssigner();
    final argumentAllocations = arguments.cAllocateStatements();
    final assignValues = arguments.assignValueStatements(a);

    final argumentString = [
      for (final argument in arguments.take(varArgsIndex ?? arguments.length))
        "${argument.type.cType} ${argument.name}",
      if (varArgsIndex != null) "...",
    ].join(", ");

    final argumentNames = arguments.map((e) => e.name).join(", ");

    String expects = "";
    String expectsZero = "";
    switch (testType) {
      case TestType.structArguments:
        // Check against sum value.
        final returnValue_ = returnValue as FundamentalType;
        final expectedResult = a.sumValue(returnValue_);
        expects = returnValue.cExpectsStatements(expectedResult, "result");

        expectsZero = returnValue.cExpectsZeroStatements("result");
        break;
      case TestType.structReturn:
        // Check against input statements.
        expects = arguments.cExpectsStatements("", "result.");

        expectsZero = arguments.cExpectsZeroStatements("result.");
        break;
      case TestType.structReturnArgument:
        // Check against input struct fields.
        expects =
            returnValue.cExpectsStatements(structReturnArgument.name, "result");

        expectsZero = returnValue.cExpectsZeroStatements("result");
        break;
    }

    return """
    // Used for testing structs and unions by value.
    ${reason.makeCComment()}
    DART_EXPORT intptr_t
    Test$cName(
        // NOLINTNEXTLINE(whitespace/parens)
        ${returnValue.cType} (*f)($argumentString)) {
      $argumentAllocations

      $assignValues

      std::cout << "Calling Test$cName(" ${arguments.coutExpression()} << ")\\n";

      ${returnValue.cType} result = f($argumentNames);

      ${returnValue.coutStatement("result")}

      $expects

      // Pass argument that will make the Dart callback throw.
      ${arguments.firstArgumentName()} = $throwExceptionValue;

      result = f($argumentNames);

      $expectsZero

      // Pass argument that will make the Dart callback return null.
      ${arguments.firstArgumentName()} = $returnNullValue;

      result = f($argumentNames);

      $expectsZero

      return 0;
    }

    """;
  }

  String get cAsyncCallbackCode {
    final a = ArgumentValueAssigner();
    final argumentAllocations = arguments.cAllocateStatements();
    final assignValues = arguments.assignValueStatements(a);

    final argumentString = [
      for (final argument in arguments.take(varArgsIndex ?? arguments.length))
        "${argument.type.cType} ${argument.name}",
      if (varArgsIndex != null) "...",
    ].join(", ");

    final argumentNames = arguments.map((e) => e.name).join(", ");

    return """
    // Used for testing structs and unions by value.
    ${reason.makeCComment()}
    DART_EXPORT void
    TestAsync$cName(
        // NOLINTNEXTLINE(whitespace/parens)
        void (*f)($argumentString)) {
      $argumentAllocations

      $assignValues

      std::cout << "Calling TestAsync$cName(" ${arguments.coutExpression()} << ")\\n";

      f($argumentNames);
    }

    """;
  }
}

/// Some value between 0 and 127 (works in every native type).
const throwExceptionValue = 42;

/// Some value between 0 and 127 (works in every native type).
const returnNullValue = 84;

const generatorPath =
    'tests/ffi/generator/structs_by_value_tests_generator.dart';

headerDartCompound({required int copyrightYear}) => """
${headerCommon(copyrightYear: copyrightYear, generatorPath: generatorPath)}

import 'dart:ffi';

""";

String compoundsPath() => Platform.script
    .resolve("../../ffi/function_structs_by_value_generated_compounds.dart")
    .toFilePath();

Future<void> writeDartCompounds() async {
  final StringBuffer buffer = StringBuffer();
  buffer.write(headerDartCompound(copyrightYear: 2021));

  buffer.writeAll(compounds.map((e) => e.dartClass()));

  final path = compoundsPath();
  await File(path).writeAsString(buffer.toString());
  await runProcess(Platform.resolvedExecutable, ["format", path]);
}

headerDartCallTest({
  required int copyrightYear,
  String vmFlags = '',
}) {
  if (vmFlags.length != 0 && !vmFlags.endsWith(' ')) {
    vmFlags += ' ';
  }

  return """
${headerCommon(copyrightYear: copyrightYear, generatorPath: generatorPath)}
//
// SharedObjects=ffi_test_functions
// VMOptions=${vmFlags.trim()}
// VMOptions=$vmFlags--deterministic --optimization-counter-threshold=90
// VMOptions=$vmFlags--use-slow-path
// VMOptions=$vmFlags--use-slow-path --stacktrace-every=100

import 'dart:ffi';

import 'package:expect/expect.dart';
// ignore: unused_import
import 'package:ffi/ffi.dart';


import 'dylib_utils.dart';

// Reuse the compound classes.
import 'function_structs_by_value_generated_compounds.dart';

final ffiTestFunctions = dlopenPlatformSpecific("ffi_test_functions");
""";
}

Future<void> writeDartCallTest(
  String nameSuffix,
  List<FunctionType> functions, {
  required bool isLeaf,
  required bool isNative,
  required bool isVarArgs,
}) async {
  final StringBuffer buffer = StringBuffer();
  buffer.write(headerDartCallTest(
    copyrightYear: isVarArgs || isNative
        ? 2023
        : isLeaf
            ? 2021
            : 2020,
  ));
  var suffix = isNative ? 'Native' : '';
  suffix += isLeaf ? 'Leaf' : '';

  final forceDlOpen = !isNative
      ? ''
      : '''
  // Force dlopen so @Native lookups in DynamicLibrary.process() succeed.
  dlopenGlobalPlatformSpecific('ffi_test_functions');
''';

  buffer.write("""
void main() {$forceDlOpen
  for (int i = 0; i < 100; ++i) {
    ${functions.map((e) => "${e.dartTestName}$suffix();").join("\n    ")}
  }
}
""");
  buffer.writeAll(
      functions.map((e) => e.dartCallCode(isLeaf: isLeaf, isNative: isNative)));

  final path = callTestPath(
      isLeaf: isLeaf,
      isNative: isNative,
      nameSuffix: nameSuffix,
      isVarArgs: isVarArgs);
  await File(path).writeAsString(buffer.toString());
  await runProcess(Platform.resolvedExecutable, ["format", path]);
}

String callTestPath({
  required bool isLeaf,
  required bool isNative,
  String nameSuffix = '',
  required bool isVarArgs,
}) {
  final baseName = isVarArgs ? 'varargs' : 'structs_by_value';
  final suffix =
      '$nameSuffix${isNative ? '_native' : ''}${isLeaf ? '_leaf' : ''}';
  return Platform.script
      .resolve("../../ffi/function_${baseName}_generated${suffix}_test.dart")
      .toFilePath();
}

headerDartCallbackTest({
  required int copyrightYear,
  String vmFlags = '',
}) {
  if (vmFlags.length != 0 && !vmFlags.endsWith(' ')) {
    vmFlags += ' ';
  }

  return """
${headerCommon(copyrightYear: copyrightYear, generatorPath: generatorPath)}
//
// SharedObjects=ffi_test_functions
// VMOptions=${vmFlags.trim()}
// VMOptions=$vmFlags--deterministic --optimization-counter-threshold=20
// VMOptions=$vmFlags--use-slow-path
// VMOptions=$vmFlags--use-slow-path --stacktrace-every=100

import 'dart:ffi';

import 'package:expect/expect.dart';
// ignore: unused_import
import 'package:ffi/ffi.dart';


import 'callback_tests_utils.dart';

import 'dylib_utils.dart';

// Reuse the compound classes.
import 'function_structs_by_value_generated_compounds.dart';

final ffiTestFunctions = dlopenPlatformSpecific("ffi_test_functions");

void main() {
  testCases.forEach((t) {
    print("==== Running " + t.name);
    t.run();
  });
}


""";
}

Future<void> writeDartCallbackTest(
  List<FunctionType> functions, {
  required bool isVarArgs,
}) async {
  for (bool isNativeCallable in [false, true]) {
    final StringBuffer buffer = StringBuffer();
    buffer.write(headerDartCallbackTest(
      copyrightYear: isVarArgs || isNativeCallable ? 2023 : 2020,
    ));

    buffer.write("""
  final testCases = [
  ${functions.map((e) => e.dartCallbackTestConstructor(isNativeCallable: isNativeCallable)).join("\n")}
  ];
  """);

    buffer.writeAll(functions.map((e) => e.dartCallbackCode()));

    final path = callbackTestPath(
        isVarArgs: isVarArgs, isNativeCallable: isNativeCallable);
    await File(path).writeAsString(buffer.toString());
    await runProcess(Platform.resolvedExecutable, ["format", path]);
  }
}

String callbackTestPath({
  required bool isVarArgs,
  required bool isNativeCallable,
}) {
  final baseName = isVarArgs ? "varargs" : "structs_by_value";
  final natCall = isNativeCallable ? "_native_callable" : "";
  return Platform.script
      .resolve(
          "../../ffi/function_callbacks_${baseName}${natCall}_generated_test.dart")
      .toFilePath();
}

headerDartAsyncCallbackTest({String vmFlags = ''}) {
  if (vmFlags.length != 0 && !vmFlags.endsWith(' ')) {
    vmFlags += ' ';
  }

  return """
${headerCommon(copyrightYear: 2023, generatorPath: generatorPath)}
//
// SharedObjects=ffi_test_functions
// VMOptions=${vmFlags.trim()}
// VMOptions=$vmFlags--deterministic --optimization-counter-threshold=20
// VMOptions=$vmFlags--use-slow-path
// VMOptions=$vmFlags--use-slow-path --stacktrace-every=100

import 'dart:async';
import 'dart:ffi';

import 'package:expect/expect.dart';
// ignore: unused_import
import 'package:ffi/ffi.dart';


import 'async_callback_tests_utils.dart';

import 'dylib_utils.dart';

// Reuse the compound classes.
import 'function_structs_by_value_generated_compounds.dart';

final ffiTestFunctions = dlopenPlatformSpecific("ffi_test_functions");

Future<void> main() async {
  for (final t in testCases) {
    print("==== Running " + t.name);
    await t.run();
  }
}


""";
}

Future<void> writeDartNativeCallableListenerTest(List<FunctionType> functions,
    {required bool isAsync}) async {
  final StringBuffer buffer = StringBuffer();
  buffer.write(headerDartAsyncCallbackTest());
  final constructors = functions
      .map((e) => e.dartNativeCallableListenerTestConstructor(isAsync: isAsync))
      .join("\n");

  buffer.write("""
final testCases = [
$constructors
];
""");

  buffer.writeAll(
      functions.map((e) => e.dartNativeCallableListenerCode(isAsync: isAsync)));

  final path = nativeCallableListenerTestPath(isAsync: isAsync);
  await File(path).writeAsString(buffer.toString());
  await runProcess(Platform.resolvedExecutable, ["format", path]);
}

String nativeCallableListenerTestPath({required bool isAsync}) {
  return Platform.script
      .resolve("../../ffi/native_callables_${isAsync ? 'async' : 'sync'}_"
          "structs_by_value_generated_test.dart")
      .toFilePath();
}

Future<void> writeC() async {
  final StringBuffer buffer = StringBuffer();
  buffer.write(headerC(copyrightYear: 2020, generatorPath: generatorPath));

  buffer.writeAll(compounds.map((e) => e.cDefinition));
  buffer.writeAll(functions.map((e) => e.cCallCode));
  buffer.writeAll(functions.map((e) => e.cCallbackCode));
  buffer.writeAll(functions.map((e) => e.cAsyncCallbackCode));
  buffer.writeAll(functionsVarArgs.map((e) => e.cCallCode));
  buffer.writeAll(functionsVarArgs.map((e) => e.cCallbackCode));

  buffer.write(footerC);

  await File(ccPath).writeAsString(buffer.toString());
  await runProcess(clangFormatPath, ["-i", ccPath]);
}

final sdkRoot = Platform.script.resolve("../../../");

final ccPath = sdkRoot
    .resolve("runtime/bin/ffi_test/ffi_test_functions_generated.cc")
    .toFilePath();

final clangFormatPath = sdkRoot
    .resolve(
        'buildtools/${buildToolsSubdir[Abi.current()]!}/clang/bin/clang-format')
    .toFilePath();

const buildToolsSubdir = {
  Abi.linuxArm64: 'linux-arm64',
  Abi.linuxX64: 'linux-x64',
  Abi.macosArm64: 'mac-arm64',
  Abi.macosX64: 'mac-x64',
  Abi.windowsX64: 'win-x64',
};

void printUsage() {
  print("""
Generates structs by value tests.
""");
}

void main(List<String> arguments) async {
  if (arguments.length != 0) {
    printUsage();
    return;
  }

  await Future.wait([
    writeDartCompounds(),
    for (bool isLeaf in [false, true]) ...[
      for (bool isNative in [false, true]) ...[
        writeDartCallTest(
          '_args',
          functionsStructArguments,
          isLeaf: isLeaf,
          isNative: isNative,
          isVarArgs: false,
        ),
        writeDartCallTest(
          '_ret',
          functionsStructReturn,
          isLeaf: isLeaf,
          isNative: isNative,
          isVarArgs: false,
        ),
        writeDartCallTest(
          '_ret_arg',
          functionsReturnArgument,
          isLeaf: isLeaf,
          isNative: isNative,
          isVarArgs: false,
        ),
        writeDartCallTest(
          '',
          functionsVarArgs,
          isLeaf: isLeaf,
          isNative: isNative,
          isVarArgs: true,
        ),
      ],
    ],
    writeDartCallbackTest(functions, isVarArgs: false),
    writeDartCallbackTest(functionsVarArgs, isVarArgs: true),
    writeDartNativeCallableListenerTest(functions, isAsync: false),
    writeDartNativeCallableListenerTest(functions, isAsync: true),
    writeC(),
  ]);
}