#
#
#           The Nimrod Compiler
#        (c) Copyright 2011 Andreas Rumpf
#
#    See the file "copying.txt", included in this
#    distribution, for details about the copyright.
#

# This module does the instantiation of generic types.

import ast, astalgo, msgs, types, semdata

proc checkConstructedType*(info: TLineInfo, t: PType) = 
  if tfAcyclic in t.flags and skipTypes(t, abstractInst).kind != tyObject: 
    LocalError(info, errInvalidPragmaX, "acyclic")
  elif t.kind == tyVar and t.sons[0].kind == tyVar: 
    LocalError(info, errVarVarTypeNotAllowed)
  elif computeSize(t) < 0:
    LocalError(info, errIllegalRecursionInTypeX, typeToString(t))
  when false:
    if t.kind == tyObject and t.sons[0] != nil:
      if t.sons[0].kind != tyObject or tfFinal in t.sons[0].flags: 
        localError(info, errInheritanceOnlyWithNonFinalObjects)
    
proc containsGenericTypeIter(t: PType, closure: PObject): bool = 
  result = t.kind in GenericTypes

proc containsGenericType*(t: PType): bool = 
  result = iterOverType(t, containsGenericTypeIter, nil)

proc searchInstTypes(tab: TIdTable, key: PType): PType = 
  # returns nil if we need to declare this type
  result = PType(IdTableGet(tab, key))
  if result == nil and tab.counter > 0: 
    # we have to do a slow linear search because types may need
    # to be compared by their structure:
    for h in countup(0, high(tab.data)): 
      var t = PType(tab.data[h].key)
      if t != nil: 
        if key.containerId == t.containerID: 
          var match = true
          for j in countup(0, sonsLen(t) - 1): 
            # XXX sameType is not really correct for nested generics?
            if not sameType(t.sons[j], key.sons[j]): 
              match = false
              break 
          if match: 
            return PType(tab.data[h].val)

type
  TReplTypeVars* {.final.} = object 
    c*: PContext
    typeMap*: TIdTable        # map PType to PType
    symMap*: TIdTable         # map PSym to PSym
    info*: TLineInfo

proc ReplaceTypeVarsT*(cl: var TReplTypeVars, t: PType): PType
proc ReplaceTypeVarsS(cl: var TReplTypeVars, s: PSym): PSym
proc ReplaceTypeVarsN(cl: var TReplTypeVars, n: PNode): PNode = 
  if n != nil: 
    result = copyNode(n)
    result.typ = ReplaceTypeVarsT(cl, n.typ)
    case n.kind
    of nkNone..pred(nkSym), succ(nkSym)..nkNilLit: 
      nil
    of nkSym: 
      result.sym = ReplaceTypeVarsS(cl, n.sym)
    else: 
      var length = sonsLen(n)
      if length > 0: 
        newSons(result, length)
        for i in countup(0, length - 1): 
          result.sons[i] = ReplaceTypeVarsN(cl, n.sons[i])
  
proc ReplaceTypeVarsS(cl: var TReplTypeVars, s: PSym): PSym = 
  if s == nil: return nil
  result = PSym(idTableGet(cl.symMap, s))
  if result == nil: 
    result = copySym(s, false)
    incl(result.flags, sfFromGeneric)
    idTablePut(cl.symMap, s, result)
    result.typ = ReplaceTypeVarsT(cl, s.typ)
    result.owner = s.owner
    result.ast = ReplaceTypeVarsN(cl, s.ast)

proc lookupTypeVar(cl: TReplTypeVars, t: PType): PType = 
  result = PType(idTableGet(cl.typeMap, t))
  if result == nil: 
    GlobalError(t.sym.info, errCannotInstantiateX, typeToString(t))
  elif result.kind == tyGenericParam: 
    InternalError(cl.info, "substitution with generic parameter")
  
proc handleGenericInvokation(cl: var TReplTypeVars, t: PType): PType = 
  var body = t.sons[0]
  if body.kind != tyGenericBody: InternalError(cl.info, "no generic body")
  var header: PType = nil
  for i in countup(1, sonsLen(t) - 1):
    var x = replaceTypeVarsT(cl, t.sons[i])
    if t.sons[i].kind == tyGenericParam: 
      if header == nil: header = copyType(t, t.owner, false)
      header.sons[i] = x
    when false:
      var x: PType
      if t.sons[i].kind == tyGenericParam: 
        x = lookupTypeVar(cl, t.sons[i])
        if header == nil: header = copyType(t, t.owner, false)
        header.sons[i] = x
      else: 
        x = t.sons[i]
    idTablePut(cl.typeMap, body.sons[i-1], x)
  if header == nil: header = t
  result = searchInstTypes(gInstTypes, header)
  if result != nil: return 
  result = newType(tyGenericInst, t.sons[0].owner)
  for i in countup(0, sonsLen(t) - 1): 
    # if one of the params is not concrete, we cannot do anything
    # but we already raised an error!
    addSon(result, header.sons[i])
  idTablePut(gInstTypes, header, result)
  var newbody = ReplaceTypeVarsT(cl, lastSon(body))
  newbody.flags = newbody.flags + t.flags + body.flags
  newbody.n = ReplaceTypeVarsN(cl, lastSon(body).n)
  addSon(result, newbody)   
  #writeln(output, ropeToStr(Typetoyaml(newbody)));
  checkConstructedType(cl.info, newbody)
    
proc ReplaceTypeVarsT*(cl: var TReplTypeVars, t: PType): PType = 
  result = t
  if t == nil: return 
  case t.kind
  of tyGenericParam: 
    result = lookupTypeVar(cl, t)
  of tyGenericInvokation: 
    result = handleGenericInvokation(cl, t)
  of tyGenericBody: 
    InternalError(cl.info, "ReplaceTypeVarsT: tyGenericBody")
    result = ReplaceTypeVarsT(cl, lastSon(t))
  else:
    if containsGenericType(t):
      result = copyType(t, t.owner, false)
      for i in countup(0, sonsLen(result) - 1):
        result.sons[i] = ReplaceTypeVarsT(cl, result.sons[i])
      result.n = ReplaceTypeVarsN(cl, result.n)
      if result.Kind in GenericTypes:
        LocalError(cl.info, errCannotInstantiateX, TypeToString(t, preferName))
        #writeln(output, ropeToStr(Typetoyaml(result)))
        #checkConstructedType(cl.info, result)

proc generateTypeInstance*(p: PContext, pt: TIdTable, arg: PNode, 
                           t: PType): PType = 
  var cl: TReplTypeVars
  InitIdTable(cl.symMap)
  copyIdTable(cl.typeMap, pt)
  cl.info = arg.info
  cl.c = p
  pushInfoContext(arg.info)
  result = ReplaceTypeVarsT(cl, t)
  popInfoContext()