#include <cstddef>
#include <cstdint>
#include <exception>
#include <iostream>
#include <sstream>

#include <llvm/ExecutionEngine/RuntimeDyld.h>

typedef enum {
  PROTECT_NONE,
  PROTECT_READ,
  PROTECT_READ_WRITE,
  PROTECT_READ_EXECUTE,
} mem_protect_t;

typedef enum {
  RESULT_OK,
  RESULT_ALLOCATE_FAILURE,
  RESULT_PROTECT_FAILURE,
  RESULT_DEALLOC_FAILURE,
  RESULT_OBJECT_LOAD_FAILURE,
} result_t;

typedef result_t (*alloc_memory_t)(size_t size, mem_protect_t protect,
                                   uint8_t **ptr_out, size_t *size_out);
typedef result_t (*protect_memory_t)(uint8_t *ptr, size_t size,
                                     mem_protect_t protect);
typedef result_t (*dealloc_memory_t)(uint8_t *ptr, size_t size);
typedef uintptr_t (*lookup_vm_symbol_t)(const char *name_ptr, size_t length);
typedef void (*fde_visitor_t)(uint8_t *fde);
typedef result_t (*visit_fde_t)(uint8_t *fde, size_t size,
                                fde_visitor_t visitor);

typedef void (*trampoline_t)(void *, void *, void *, void *);

typedef struct {
  /* Memory management. */
  alloc_memory_t alloc_memory;
  protect_memory_t protect_memory;
  dealloc_memory_t dealloc_memory;

  lookup_vm_symbol_t lookup_vm_symbol;

  visit_fde_t visit_fde;
} callbacks_t;

typedef struct {
  size_t data, vtable;
} box_any_t;

struct WasmException {
public:
  virtual std::string description() const noexcept = 0;
};

struct UncatchableException : WasmException {
public:
  virtual std::string description() const noexcept override {
    return "Uncatchable exception";
  }
};

struct UserException : UncatchableException {
public:
  UserException(size_t data, size_t vtable) : error_data({data, vtable}) {}

  virtual std::string description() const noexcept override {
    return "user exception";
  }

  // The parts of a `Box<dyn Any>`.
  box_any_t error_data;
};

struct BreakpointException : UncatchableException {
public:
  BreakpointException(uintptr_t callback) : callback(callback) {}

  virtual std::string description() const noexcept override {
    return "breakpoint exception";
  }

  uintptr_t callback;
};

struct WasmTrap : UncatchableException {
public:
  enum Type {
    Unreachable = 0,
    IncorrectCallIndirectSignature = 1,
    MemoryOutOfBounds = 2,
    CallIndirectOOB = 3,
    IllegalArithmetic = 4,
    Unknown,
  };

  WasmTrap(Type type) : type(type) {}

  virtual std::string description() const noexcept override {
    std::ostringstream ss;
    ss << "WebAssembly trap:" << '\n' << " - type: " << type << '\n';

    return ss.str();
  }

  Type type;

private:
  friend std::ostream &operator<<(std::ostream &out, const Type &ty) {
    switch (ty) {
    case Type::Unreachable:
      out << "unreachable";
      break;
    case Type::IncorrectCallIndirectSignature:
      out << "incorrect call_indirect signature";
      break;
    case Type::MemoryOutOfBounds:
      out << "memory access out-of-bounds";
      break;
    case Type::CallIndirectOOB:
      out << "call_indirect out-of-bounds";
      break;
    case Type::IllegalArithmetic:
      out << "illegal arithmetic operation";
      break;
    case Type::Unknown:
    default:
      out << "unknown";
      break;
    }
    return out;
  }
};

struct CatchableException : WasmException {
public:
  CatchableException(uint32_t type_id, uint32_t value_num)
      : type_id(type_id), value_num(value_num) {}

  virtual std::string description() const noexcept override {
    return "catchable exception";
  }

  uint32_t type_id, value_num;
  uint64_t values[1];
};

struct WasmModule {
public:
  WasmModule(const uint8_t *object_start, size_t object_size,
             callbacks_t callbacks);

  void *get_func(llvm::StringRef name) const;

  bool _init_failed = false;

private:
  std::unique_ptr<llvm::RuntimeDyld::MemoryManager> memory_manager;
  std::unique_ptr<llvm::object::ObjectFile> object_file;
  std::unique_ptr<llvm::RuntimeDyld> runtime_dyld;
};

extern "C" {
void callback_trampoline(void *, void *);

result_t module_load(const uint8_t *mem_ptr, size_t mem_size,
                     callbacks_t callbacks, WasmModule **module_out) {
  *module_out = new WasmModule(mem_ptr, mem_size, callbacks);

  if ((*module_out)->_init_failed) {
    return RESULT_OBJECT_LOAD_FAILURE;
  }

  return RESULT_OK;
}

[[noreturn]] void throw_trap(WasmTrap::Type ty) { throw WasmTrap(ty); }

void module_delete(WasmModule *module) { delete module; }

// Throw a fat pointer that's assumed to be `*mut dyn Any` on the rust
// side.
[[noreturn]] void throw_any(size_t data, size_t vtable) {
  throw UserException(data, vtable);
}

// Throw a pointer that's assumed to be codegen::BreakpointHandler on the
// rust side.
[[noreturn]] void throw_breakpoint(uintptr_t callback) {
  throw BreakpointException(callback);
}

bool invoke_trampoline(trampoline_t trampoline, void *ctx, void *func,
                       void *params, void *results, WasmTrap::Type *trap_out,
                       box_any_t *user_error, void *invoke_env) noexcept {
  try {
    trampoline(ctx, func, params, results);
    return true;
  } catch (const WasmTrap &e) {
    *trap_out = e.type;
    return false;
  } catch (const UserException &e) {
    *user_error = e.error_data;
    return false;
  } catch (const BreakpointException &e) {
    callback_trampoline(user_error, (void *)e.callback);
    return false;
  } catch (const WasmException &e) {
    *trap_out = WasmTrap::Type::Unknown;
    return false;
  } catch (...) {
    *trap_out = WasmTrap::Type::Unknown;
    return false;
  }
}

void *get_func_symbol(WasmModule *module, const char *name) {
  return module->get_func(llvm::StringRef(name));
}
}