#pragma once

#include <concepts>
#include <cstdint>
#include <cstring>
#include <iostream>

#include "arena.hpp"
#include "pod.hpp"

// Forward declarations

class Value;

struct SourcePosition {
  size_t line{1};
  size_t column{1};
  size_t offset{0};
};

struct SourceRange {
  SourcePosition start;
  SourcePosition end;
};

class PodInt64 final : public PodObject {
 public:
  PodInt64() : PodObject(Tag::Int64){};

  int64_t value;
};

class PodFloat final : public PodObject {
 public:
  PodFloat() : PodObject(Tag::Float){};

  double value;
};

class PodString final : public PodObject {
 public:
  PodString() : PodObject(Tag::String){};

  uint64_t size;
  char32_t data[];
};

class PodSymbol final : public PodObject {
 public:
  PodSymbol() : PodObject(Tag::Symbol){};

  uint64_t size;
  char32_t data[];
};

class PodSyntax : public PodObject {
 public:
  PodSyntax() : PodObject(Tag::Syntax){};
  OffPtr<PodString> filename;
  OffPtr<PodString> modulename;
  OffPtr<PodObject> expression;
  SourceRange sourcerange;
};

class PodPair : public PodObject {
 public:
  PodPair() : PodObject(Tag::Pair){};
  OffPtr<PodObject> first;
  OffPtr<PodObject> second;
};

class Object {
 public:
  virtual Tag tag() = 0;
  virtual Result<Value> copy(Arena& arena) = 0;
};

class Nil : public Object {
 public:
  Nil() {}

  virtual Tag tag() final { return Tag::Nil; }
  virtual Result<Value> copy(Arena& arena) final;
};

class String : public Object {
 public:
  String() {}
  String(GcRoot<PodString>&& val) : _value(std::move(val)) {}
  virtual Tag tag() final { return Tag::String; }

  static Result<String> create(Arena& arena, PodString* obj) {
    return String(TRY(MkGcRoot(obj, arena)));
  }
  static Result<String> create(Arena& arena, char32_t* chars, int64_t size) {
    auto pod_string = TRY(arena.alloc<PodString>(size * sizeof(char32_t)));

    memcpy(pod_string->data, chars, size * sizeof(char32_t));

    return String(TRY(MkGcRoot(pod_string, arena)));
  }

  virtual Result<Value> copy(Arena& arena) final;

 private:
  GcRoot<PodString> _value;
};

class Symbol : public Object {
 public:
  Symbol() {}
  Symbol(GcRoot<PodSymbol>&& val) : _value(std::move(val)) {}
  virtual Tag tag() final { return Tag::Symbol; }

  static Result<Symbol> create(Arena& arena, PodSymbol* obj) {
    return Symbol(TRY(MkGcRoot(obj, arena)));
  }

  static Result<Symbol> create(Arena& arena, char32_t* chars, int64_t size) {
    auto pod_symbol = TRY(arena.alloc<PodSymbol>(size * sizeof(char32_t)));

    memcpy(pod_symbol->data, chars, size * sizeof(char32_t));

    return Symbol(TRY(MkGcRoot(pod_symbol, arena)));
  }

  virtual Result<Value> copy(Arena& arena) final;

 private:
  GcRoot<PodSymbol> _value;
};

class Syntax : public Object {
 public:
  Syntax() {}
  Syntax(GcRoot<PodSyntax>&& val) : _value(std::move(val)) {}
  Syntax(String filename, String modulename, Value expression);
  virtual Tag tag() final { return Tag::Syntax; }

  static Result<Syntax> create(Arena& arena, PodSyntax* obj) {
    return Syntax(TRY(MkGcRoot(obj, arena)));
  }

  Result<Value> get_value(Arena& arena);

  virtual Result<Value> copy(Arena& arena) final;

 private:
  GcRoot<PodSyntax> _value;
};

class Pair : public Object {
 public:
  Pair() {}
  Pair(GcRoot<PodPair>&& val) : _value(std::move(val)) {}
  virtual Tag tag() final { return Tag::Pair; }

  static Result<Pair> create(Arena& arena, PodPair* obj) {
    return Pair(TRY(MkGcRoot(obj, arena)));
  }

  static Result<Value> first(Arena& arena);

  virtual Result<Value> copy(Arena& arena) final;

 private:
  GcRoot<PodPair> _value;
};

class Int64 : public Object {
 public:
  Int64() : _value(0) {}
  Int64(int64_t val) : _value(val) {}
  virtual ~Int64() = default;

  virtual Tag tag() final { return Tag::Int64; }

  int64_t value() { return _value; }

  virtual Result<Value> copy(Arena& arena) final;

 private:
  int64_t _value;
};

class Float : public Object {
 public:
  Float() : _value(0) {}
  Float(double val) : _value(val) {}
  virtual ~Float() = default;

  virtual Tag tag() final { return Tag::Float; }

  double value() { return _value; }

  virtual Result<Value> copy(Arena& arena) final;

 private:
  double _value;
};

// note: this class doesn't perform proper destruction of objects in some cases
class Value {
 public:
  Value() { new (buf) Nil(); }
  ~Value() { ((Object*)buf)->~Object(); }
  Value(Value&& val) { memcpy(buf, val.buf, 24); }
  Value(const Value&) = delete;

  template <class T>
  Value(T&& obj)
    requires std::derived_from<T, Object>
  {
    new (buf) T(std::move(obj));
  }

  static Result<Value> create(Arena& arena, PodObject* obj);

  template <class T>
  bool is() {
    return dynamic_cast<T*>((Object*)buf) != nullptr;
  }

  template <class T>
  T* to() {
    return dynamic_cast<T*>((Object*)buf);
  }

  Object& operator*() { return *(Object*)(buf); }
  Object* operator->() { return (Object*)(buf); }

  Result<Value> copy(Arena& arena) { return ((Object*)buf)->copy(arena); }

 private:
  uint8_t buf[24];
};

Result<Value> syntax_unwrap(Value& val);