namespace Eva {
  public interface Term : Object {
    public abstract string to_string();
    
    public bool equals(Term o) {
      return (match(o) != null);
    }
    
    public Gee.Map<string, Term>? match(Term o) {
      Gee.Map<string, Term> vars = new Gee.HashMap<string, Term>();
      Gee.Map<string, string> aliases = new Gee.HashMap<string, string>();
      if(!do_match(o, vars, aliases)) {
        return null;
      }
      else {
        foreach(string a in aliases.keys) {
          string v = Var.alias(a, aliases);
          
          if(v in vars)
            vars[a] = vars[v];
        }
        
        return vars;
      }
    }
    
    protected abstract bool do_match(Term o, Gee.Map<string, Term> vars, Gee.Map<string, string> aliases);
    
    public abstract void encode(Erl.Buffer buffer);
    
    public static Term decode(void *buffer) {
      int index = 0;
      int version;
      
      Erl.decode_version(buffer, ref index, out version);
      
      return do_decode(buffer, ref index);
    }
    
    private static Term do_decode(void *buffer, ref int index) {
      int type, size;
      assert(Erl.get_type(buffer, ref index, out type, out size) == 0);
      
      switch(type) {
      case Erl.TermType.SMALL_INTEGER:
        char value;
        assert(Erl.decode_char(buffer, ref index, out value) == 0);
        return new Int((uchar)value);
        
      case Erl.TermType.INTEGER:
        long value;
        assert(Erl.decode_long(buffer, ref index, out value) == 0);
        return new Int(value);
        
      case Erl.TermType.FLOAT:
        double value;
        assert(Erl.decode_double(buffer, ref index, out value) == 0);
        return new Double(value);
        
      case Erl.TermType.ATOM:
        char[] value = new char[size+1];
        assert(Erl.decode_atom(buffer, ref index, value) == 0);
        return new Atom(array_to_string(value, size));
        
      case Erl.TermType.SMALL_TUPLE:
      case Erl.TermType.LARGE_TUPLE:
        assert(Erl.decode_tuple_header(buffer, ref index, out size) == 0);
        Term[] terms = new Term[size];
        
        for(int i = 0; i < size; ++i) {
          terms[i] = do_decode(buffer, ref index);
        }
        
        return new Tuple(terms);
        
      case Erl.TermType.NIL:
      case Erl.TermType.LIST:
        List term = new List();
        
        assert(Erl.decode_list_header(buffer, ref index, out size) == 0);
        if(size != 0) {
          for(int i = 0; i < size; ++i) {
            term.list.add(do_decode(buffer, ref index));
          }
        
          term.tail = do_decode(buffer, ref index);
        }
        
        return term;
        
      case Erl.TermType.STRING:
        char[] value = new char[size+1];
        assert(Erl.decode_string(buffer, ref index, value) == 0);
        return new String(array_to_string(value, size));
        
      case Erl.TermType.BINARY:
        char[] value = new char[size];
        long l;
        assert(Erl.decode_binary(buffer, ref index, value, out l) == 0);
        return new Binary(value);
        
      case Erl.TermType.PID:
        Erl.Pid value;
        assert(Erl.decode_pid(buffer, ref index, out value) == 0);
        return new Pid(value);
        
      case Erl.TermType.PORT:
        Erl.Port value;
        assert(Erl.decode_port(buffer, ref index, out value) == 0);
        return new Port(value);
        
      case Erl.TermType.REFERENCE:
      case Erl.TermType.NEW_REFERENCE:
        Erl.Ref value;
        assert(Erl.decode_ref(buffer, ref index, out value) == 0);
        return new Ref(value);
        
      default:
        assert_not_reached();
      }
    }
  }
  
  public class Int : Object, Term {
    public long value {get; construct;}
    
    public Int(long v) {
      Object(value: v);
    }
    
    public string to_string() {
      return value.to_string();
    }
    
    protected bool do_match(Term o, Gee.Map<string, Term> vars, Gee.Map<string, string> aliases) {
      if(o is Var) {
        return o.do_match(this, vars, aliases);
      }
      
      if(o is Int) {
        return value == (o as Int).value;
      }
      else if(o is UInt) {
        return value == (o as UInt).value;
      }
      else {
        return false;
      }
    }
    
    public void encode(Erl.Buffer buffer) {
      buffer.encode_long(value);
    }
  }
  
  public class UInt : Object, Term {
    public ulong value {get; construct;}
    
    public UInt(ulong v) {
      Object(value: v);
    }
    
    public string to_string() {
      return value.to_string();
    }
    
    protected bool do_match(Term o, Gee.Map<string, Term> vars, Gee.Map<string, string> aliases) {
      if(o is Var) {
        return o.do_match(this, vars, aliases);
      }
      
      if(o is Int) {
        return value == (o as Int).value;
      }
      else if(o is UInt) {
        return value == (o as UInt).value;
      }
      else {
        return false;
      }
    }

    
    public void encode(Erl.Buffer buffer) {
      buffer.encode_ulong(value);
    }
  }
  
  public class Double : Object, Term {
    public double value {get; construct;}
    
    public Double(double v) {
      Object(value: v);
    }
    
    public string to_string() {
      return value.to_string();
    }
    
    protected bool do_match(Term o, Gee.Map<string, Term> vars, Gee.Map<string, string> aliases) {
      if(o is Var) {
        return o.do_match(this, vars, aliases);
      }
      
      if(o is Double) {
        return value == (o as Double).value;
      }
      else {
        return false;
      }
    }
    
    public void encode(Erl.Buffer buffer) {
      buffer.encode_double(value);
    }
  }
  
  public class Atom : Object, Term {
    public string value {get; construct;}
    
    public Atom(string v) {
      assert(v.validate());
      Object(value: v);
    }
    
    public string to_string() {
      if(value.length == 0)
        return "''";
      
      bool special = false;
      unichar c = value.get_char();
      
      if(!c.islower())
        special = true;
      
      for(unowned string rest = value.next_char(); rest.length != 0 && !special; rest = rest.next_char()) {
        c = rest.get_char();
        
        if(!(c == '_' || c.isalnum()))
          special = true;
      }
      
      if(!special) {
        return value;
      }
      else {
        return "'" + value.replace("\\", "\\\\").replace("'", "\\'") + "'";
      }
    }
    
    protected bool do_match(Term o, Gee.Map<string, Term> vars, Gee.Map<string, string> aliases) {
      if(o is Var) {
        return o.do_match(this, vars, aliases);
      }
      
      if(o is Atom) {
        return value == (o as Atom).value;
      }
      else {
        return false;
      }
    }
    
    public void encode(Erl.Buffer buffer) {
      char[]? array = string_to_array(value);
      assert(array != null);
      buffer.encode_atom(array);
    }
  }
  
  public class Tuple : Object, Term {
    private Term[] elements {get; set;}
    
    public Tuple(Term[] terms) {
      elements = terms;
    }
    
    public int size {
      get {
        return elements.length;
      }
    }
    
    public new unowned Term get(int i) {
      assert(i >= 0 && i < size);
      
      return elements[i];
    }
    
    public string to_string() {
      string ret = "{";
      bool first = true;
      
      foreach(Term term in elements) {
        if(first) {
          first = false;
          ret += term.to_string();
        }
        else {
          ret += "," + term.to_string();
        }
      }
      
      return ret + "}";
    }
    
    protected bool do_match(Term o, Gee.Map<string, Term> vars, Gee.Map<string, string> aliases) {
      if(o is Var) {
        return o.do_match(this, vars, aliases);
      }
      
      if(!(o is Tuple))
        return false;
      
      Tuple t = o as Tuple;
      
      if(t.size != size)
        return false;
      
      for(int i = 0; i < size; ++i) {
        if(!this[i].do_match(t[i], vars, aliases))
          return false;
      }
      
      return true;
    }
    
    public void encode(Erl.Buffer buffer) {
      buffer.encode_tuple_header(size);
      
      foreach(Term term in elements) {
        term.encode(buffer);
      }
    }
  }
  
  public class List : Object, Term {
    private Term? _tail;
    
    public Gee.List<Term?> list {get; construct;}
    public Term? tail {
      get {
        return _tail;
      }
      set {
        if(value is List) {
          List l = value as List;
          
          list.add_all(l.list);
          _tail = l._tail;
        }
        else {
          _tail = value;
        }
      }
    }
    
    public List() {
      Gee.List<Term?> list0 = new Gee.LinkedList<Term?>();
      Object(list: list0);
      tail = null;
    }
    
    protected bool do_match(Term o, Gee.Map<string, Term> vars, Gee.Map<string, string> aliases) {
      if(o is Var) {
        return o.do_match(this, vars, aliases);
      }
      
      if(o is List) {
        List l = o as List;
        
        if(list.size != l.list.size)
          return false;
        if((tail == null) != (l.tail == null))
          return false;
        if(tail != null && !tail.do_match(l.tail, vars, aliases))
          return false;
        
        Gee.Iterator<Term> lt = l.list.iterator();
        lt.first();
        foreach(Term t in list) {
          if(!t.do_match(lt.get(), vars, aliases))
            return false;
          
          lt.next();
        }
        
        return true;
      }
      else if(o is String) {
        if(tail != null)
          return false;
        
        string s = "";
        
        foreach(Term t in list) {
          unichar c;
          
          if(t is Int) {
            Int i = t as Int;
            if(i.value < 0 || i.value > 255)
              return false;
            
            c = (unichar)i.value;
          }
          else if(t is UInt) {
            UInt i = t as UInt;
            if(i.value > 255)
              return false;
            
            c = (unichar)i.value;
          }
          else {
            return false;
          }
          
          string buf = string.nfill(6, 0);
          c.to_utf8(buf);
          
          s += buf;
        }
        
        return (s == (o as String).value);
      }
      else {
        return false;
      }
    }
    
    public string to_string() {
      string ret = "[";
      bool first = true;
      
      foreach(Term term in list) {
        if(first) {
          first = false;
          ret += term.to_string();
        }
        else {
          ret += "," + term.to_string();
        }
      }
      
      if(tail != null)
        ret += "|" + tail.to_string();
      
      return ret + "]";
    }
    
    public void encode(Erl.Buffer buffer) {
      if(!list.is_empty) {
        buffer.encode_list_header(list.size);
      
        foreach(Term term in list) {
          term.encode(buffer);
        }
      }
      
      if(tail == null)
        buffer.encode_empty_list();
      else
        tail.encode(buffer);
    }
  }
  
  public class String : Object, Term {
    public string value {get; construct;}
    
    public String(string v) {
      Object(value: v);
    }
    
    public string to_string() {
      return "\"" + value.replace("\\", "\\\\").replace("\"", "\\\"") + "\"";
    }
    
    protected bool do_match(Term o, Gee.Map<string, Term> vars, Gee.Map<string, string> aliases) {
      if(o is Var) {
        return o.do_match(this, vars, aliases);
      }
      
      if(o is String) {
        return (value == (o as String).value);
      }
      else if(o is List) {
        return o.do_match(this, vars, aliases);
      }
      else {
        return false;
      }
    }
    
    public void encode(Erl.Buffer buffer) {
      char[]? array = string_to_array(value);
      if(array != null) {
        buffer.encode_string(array);
      }
      else {
        string_to_list(value).encode(buffer);
      }
    }
  }
  
  public class Binary : Object, Term {
    public void* value {get; private set;}
    public long len {get; private set;}
    
    public Binary(char[] v) {
      value = Memory.dup(v, (uint)(sizeof(char)*v.length));
      len = v.length;
    }
    
    public string to_string() {
      return "#Bin";
    }
    
    protected bool do_match(Term o, Gee.Map<string, Term> vars, Gee.Map<string, string> aliases) {
      if(o is Var) {
        return o.do_match(this, vars, aliases);
      }
      
      if(o is Binary) {
        Binary b = o as Binary;
        
        if(b.len != len)
          return false;
        
        return (Memory.cmp(value, b.value, len) == 0);
      }
      else {
        return false;
      }
    }

    
    public void encode(Erl.Buffer buffer) {
      buffer.encode_binary((char*)value, len);
    }
  }
  
  public class Pid : Object, Term {
    public string node {get; construct;}
    public uint num {get; construct;}
    public uint serial {get; construct;}
    public uint creation {get; construct;}
    
    public Pid(Erl.Pid pid) {
      this.create(array_to_string(pid.node, Erl.MAXATOMLEN), pid.num, pid.serial, pid.creation);
    }
    
    private Pid.create(string node0, uint num0, uint serial0, uint creation0) {
      Object(node: node0, num: num0, serial: serial0, creation: creation0);
    }
    
    public string to_string() {
      return "<" + node + "." + num.to_string() + "." + serial.to_string() + ">";
    }
    
    protected bool do_match(Term o, Gee.Map<string, Term> vars, Gee.Map<string, string> aliases) {
      if(o is Var) {
        return o.do_match(this, vars, aliases);
      }
      
      if(!(o is Pid))
        return false;
      
      Pid p = o as Pid;
      
      return (node == p.node && num == p.num && serial == p.serial && creation == p.creation);
    }
    
    public void encode(Erl.Buffer buffer) {
      Erl.Pid pid = Erl.Pid();
      char[]? nodedata = string_to_array(node);
      assert(nodedata != null);
      
      Memory.copy(pid.node, nodedata, int.min(Erl.MAXATOMLEN, nodedata.length));
      pid.node[int.min(Erl.MAXATOMLEN, nodedata.length)] = 0;
      
      pid.num = num;
      pid.serial = serial;
      pid.creation = creation;
      
      buffer.encode_pid(pid);
    }
  }

  public class Port : Object, Term {
    public string node {get; construct;}
    public uint id {get; construct;}
    public uint creation {get; construct;}
    
    public Port(Erl.Port port) {
      this.create(array_to_string(port.node, Erl.MAXATOMLEN), port.id, port.creation);
    }
    
    private Port.create(string node0, uint id0, uint creation0) {
      Object(node: node0, id: id0, creation: creation0);
    }
    
    public string to_string() {
      return "#Port";
    }
    
    protected bool do_match(Term o, Gee.Map<string, Term> vars, Gee.Map<string, string> aliases) {
      if(o is Var) {
        return o.do_match(this, vars, aliases);
      }
      
      if(!(o is Port))
        return false;
      
      Port p = o as Port;
      
      return (node == p.node && id == p.id && creation == p.creation);
    }
    
    public void encode(Erl.Buffer buffer) {
      Erl.Port port = Erl.Port();
      char[]? nodedata = string_to_array(node);
      assert(nodedata != null);
      
      Memory.copy(port.node, nodedata, int.min(Erl.MAXATOMLEN, nodedata.length));
      port.node[int.min(Erl.MAXATOMLEN, nodedata.length)] = 0;
      
      port.id = id;
      port.creation = creation;
      
      buffer.encode_port(port);
    }
  }
  
  public class Ref : Object, Term {
    public string node {get; construct;}
    public int len {get; construct;}
    public uint[] n {get; private set;}
    public uint creation {get; construct;}
    
    public Ref(Erl.Ref reference) {
      this.create(array_to_string(reference.node, Erl.MAXATOMLEN), reference.len, reference.n, reference.creation);
    }
    
    private Ref.create(string node0, int len0, uint* n0, uint creation0) {
      Object(node: node0, len: len0, creation: creation0);
      
      n = new uint[len];
      for(int i = 0; i < len; ++i) {
        n[i] = n0[i];
      }
    }
    
    public string to_string() {
      return "#Ref";
    }
    
    protected bool do_match(Term o, Gee.Map<string, Term> vars, Gee.Map<string, string> aliases) {
      if(o is Var) {
        return o.do_match(this, vars, aliases);
      }
      
      if(!(o is Ref))
        return false;
      
      Ref r = o as Ref;
      
      if(node != r.node || len != r.len || creation != r.creation) {
        return false;
      }
      
      for(int i = 0; i < len; ++i) {
        if(n[i] != r.n[i])
          return false;
      }
      
      return true;
    }
    
    public void encode(Erl.Buffer buffer) {
      Erl.Ref reference = Erl.Ref();
      char[]? nodedata = string_to_array(node);
      assert(nodedata != null);
      
      Memory.copy(reference.node, nodedata, int.min(Erl.MAXATOMLEN, nodedata.length));
      reference.node[int.min(Erl.MAXATOMLEN, nodedata.length)] = 0;
      
      reference.len = len;
      
      for(int i = 0; i < len; ++i) {
        reference.n[i] = n[i];
      }
      
      reference.creation = creation;
      
      buffer.encode_ref(reference);
    }
  }
  
  public class Var : Term, Object {
    public string name {get; construct;}
    
    public Var(string name0) {
      assert(name0.get_char() == '_' || name0.get_char().isupper());
      
      Object(name: name0);
    }
    
    public string to_string() {
      return name;
    }
    
    internal static string alias(string key, Gee.Map<string, string> aliases) {
      if(!(key in aliases))
        return key;
      else
        return alias(aliases[key], aliases);
    }
    
    protected bool do_match(Term o, Gee.Map<string, Term> vars, Gee.Map<string, string> aliases) {
      string key = alias(name, aliases);
      
      if(o is Var) {
        Var v = o as Var;
        string vkey = alias(v.name, aliases);
        
        if(key == vkey)
          return true;
        
        if(key in vars && vkey in vars)
          return vars[key].do_match(vars[vkey], vars, aliases);
        else if(!(vkey in vars)) {
          aliases[vkey] = key;
          return true;
        }
        else /* !(key in vars) */ {
          aliases[key] = vkey;
          return true;
        }
      }
      else {
        if(key in vars) {
          return vars[key].do_match(o, vars, aliases);
        }
        else {
          vars[key] = o;
          return true;
        }
      }
    }
    
    public void encode(Erl.Buffer buffer) {
      assert_not_reached();
    }
  }
}