#
#
#           The Nim Compiler
#        (c) Copyright 2017 Andreas Rumpf
#
#    See the file "copying.txt", included in this
#    distribution, for details about the copyright.
#

## This module implements the module graph data structure. The module graph
## represents a complete Nim project. Single modules can either be kept in RAM
## or stored in a rod-file.

import std/[intsets, tables, hashes, strtabs, os, strutils, parseutils]
import ../dist/checksums/src/checksums/md5
import ast, astalgo, options, lineinfos,idents, btrees, ropes, msgs, pathutils, packages, suggestsymdb

when not defined(nimKochBootstrap):
  import ast2nif
  import "../dist/nimony/src/lib" / [nifstreams, bitabs]

import typekeys

when defined(nimPreviewSlimSystem):
  import std/assertions

type
  SigHash* = distinct MD5Digest

  Iface* = object       ## data we don't want to store directly in the
                        ## ast.PSym type for s.kind == skModule
    module*: PSym       ## module this "Iface" belongs to
    converters*: seq[PSym]
    patterns*: seq[PSym]
    pureEnums*: seq[PSym]
    interf: TStrTable
    interfHidden: TStrTable
    uniqueName*: Rope

  Operators* = object
    opNot*, opContains*, opLe*, opLt*, opAnd*, opOr*, opIsNil*, opEq*: PSym
    opAdd*, opSub*, opMul*, opDiv*, opLen*: PSym

  PipelinePass* = enum
    NonePass
    SemPass
    JSgenPass
    CgenPass
    NifgenPass
    EvalPass
    InterpreterPass
    GenDependPass
    Docgen2TexPass
    Docgen2JsonPass
    Docgen2Pass

  ModuleGraph* {.acyclic.} = ref object
    ifaces*: seq[Iface]  ## indexed by int32 fileIdx

    typeInstCache*: Table[ItemId, seq[PType]] # A symbol's ItemId.
    procInstCache*: Table[ItemId, seq[PInstantiation]] # A symbol's ItemId.
    attachedOps*: array[TTypeAttachedOp, Table[ItemId, PSym]] # Type ID, destructors, etc.
    loadedOps: array[TTypeAttachedOp, Table[string, PSym]] # This can later by unified with `attachedOps` once it's stable
    opsLog*: seq[LogEntry]
    methodsPerGenericType*: Table[ItemId, seq[(int, PSym)]] # Type ID, attached methods
    memberProcsPerType*: Table[ItemId, seq[PSym]] # Type ID, attached member procs (only c++, virtual,member and ctor so far).
    initializersPerType*: Table[ItemId, PNode] # Type ID, AST call to the default ctor (c++ only)
    enumToStringProcs*: Table[ItemId, PSym]
    emittedTypeInfo*: Table[string, FileIndex]

    packageSyms*: TStrTable
    deps*: IntSet # the dependency graph or potentially its transitive closure.
    importDeps*: Table[FileIndex, seq[FileIndex]] # explicit import module dependencies
    suggestMode*: bool # whether we are in nimsuggest mode or not.
    invalidTransitiveClosure: bool
    interactive*: bool
    withinSystem*: bool # in system.nim or a module imported by system.nim
    inclToMod*: Table[FileIndex, FileIndex] # mapping of include file to the
                                            # first module that included it
    importStack*: seq[FileIndex]  # The current import stack. Used for detecting recursive
                                  # module dependencies.
    backend*: RootRef # minor hack so that a backend can extend this easily
    config*: ConfigRef
    cache*: IdentCache
    vm*: RootRef # unfortunately the 'vm' state is shared project-wise, this will
                 # be clarified in later compiler implementations.
    repl*: RootRef # REPL state is shared project-wise.
    doStopCompile*: proc(): bool {.closure.}
    usageSym*: PSym # for nimsuggest
    owners*: seq[PSym]
    suggestSymbols*: SuggestSymbolDatabase
    suggestErrors*: Table[FileIndex, seq[Suggest]]
    methods*: seq[tuple[methods: seq[PSym], dispatcher: PSym]] # needs serialization!
    bucketTable*: CountTable[ItemId]
    objectTree*: Table[ItemId, seq[tuple[depth: int, value: PType]]]
    methodsPerType*: Table[ItemId, seq[PSym]]
    dispatchers*: seq[PSym]

    systemModule*: PSym
    sysTypes*: array[TTypeKind, PType]
    compilerprocs*: TStrTable
    exposed*: TStrTable
    packageTypes*: TStrTable
    emptyNode*: PNode
    canonTypes*: Table[SigHash, PType]
    symBodyHashes*: Table[int, SigHash] # symId to digest mapping
    importModuleCallback*: proc (graph: ModuleGraph; m: PSym, fileIdx: FileIndex): PSym {.nimcall.}
    includeFileCallback*: proc (graph: ModuleGraph; m: PSym, fileIdx: FileIndex): PNode {.nimcall.}
    cacheSeqs*: Table[string, PNode] # state that is shared to support the 'macrocache' API; IC: implemented
    cacheCounters*: Table[string, BiggestInt] # IC: implemented
    cacheTables*: Table[string, BTree[string, PNode]] # IC: implemented
    passes*: seq[TPass]
    pipelinePass*: PipelinePass
    onDefinition*: proc (graph: ModuleGraph; s: PSym; info: TLineInfo) {.nimcall.}
    onDefinitionResolveForward*: proc (graph: ModuleGraph; s: PSym; info: TLineInfo) {.nimcall.}
    onUsage*: proc (graph: ModuleGraph; s: PSym; info: TLineInfo) {.nimcall.}
    globalDestructors*: seq[PNode]
    strongSemCheck*: proc (graph: ModuleGraph; owner: PSym; body: PNode) {.nimcall.}
    compatibleProps*: proc (graph: ModuleGraph; formal, actual: PType): bool {.nimcall.}
    idgen*: IdGenerator
    operators*: Operators

    cachedFiles*: StringTableRef

    procGlobals*: seq[PNode]
    nifReplayActions*: Table[int32, seq[PNode]]  # module position -> replay actions for NIF
    cachedMods: IntSet

  TPassContext* = object of RootObj # the pass's context
    idgen*: IdGenerator
  PPassContext* = ref TPassContext

  TPassOpen* = proc (graph: ModuleGraph; module: PSym; idgen: IdGenerator): PPassContext {.nimcall.}
  TPassClose* = proc (graph: ModuleGraph; p: PPassContext, n: PNode): PNode {.nimcall.}
  TPassProcess* = proc (p: PPassContext, topLevelStmt: PNode): PNode {.nimcall.}

  TPass* = tuple[open: TPassOpen,
                 process: TPassProcess,
                 close: TPassClose,
                 isFrontend: bool]

proc resetForBackend*(g: ModuleGraph) =
  g.compilerprocs = initStrTable()
  g.typeInstCache.clear()
  g.procInstCache.clear()
  for a in mitems(g.attachedOps):
    a.clear()
  g.methodsPerGenericType.clear()
  g.enumToStringProcs.clear()
  g.dispatchers.setLen(0)
  g.methodsPerType.clear()
  for a in mitems(g.loadedOps):
    a.clear()
  g.opsLog.setLen(0)

const
  cb64 = [
    "A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N",
    "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z",
    "a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n",
    "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z",
    "0", "1", "2", "3", "4", "5", "6", "7", "8", "9a",
    "9b", "9c"]

proc toBase64a(s: cstring, len: int): string =
  ## encodes `s` into base64 representation.
  result = newStringOfCap(((len + 2) div 3) * 4)
  result.add "__"
  var i = 0
  while i < len - 2:
    let a = ord(s[i])
    let b = ord(s[i+1])
    let c = ord(s[i+2])
    result.add cb64[a shr 2]
    result.add cb64[((a and 3) shl 4) or ((b and 0xF0) shr 4)]
    result.add cb64[((b and 0x0F) shl 2) or ((c and 0xC0) shr 6)]
    result.add cb64[c and 0x3F]
    inc(i, 3)
  if i < len-1:
    let a = ord(s[i])
    let b = ord(s[i+1])
    result.add cb64[a shr 2]
    result.add cb64[((a and 3) shl 4) or ((b and 0xF0) shr 4)]
    result.add cb64[((b and 0x0F) shl 2)]
  elif i < len:
    let a = ord(s[i])
    result.add cb64[a shr 2]
    result.add cb64[(a and 3) shl 4]

template interfSelect(iface: Iface, importHidden: bool): TStrTable =
  var ret = iface.interf.addr # without intermediate ptr, it creates a copy and compiler becomes 15x slower!
  if importHidden: ret = iface.interfHidden.addr
  ret[]

template semtab(g: ModuleGraph, m: PSym): TStrTable =
  g.ifaces[m.position].interf

template semtabAll*(g: ModuleGraph, m: PSym): TStrTable =
  g.ifaces[m.position].interfHidden

proc initStrTables*(g: ModuleGraph, m: PSym) =
  semtab(g, m) = initStrTable()
  semtabAll(g, m) = initStrTable()

proc strTableAdds*(g: ModuleGraph, m: PSym, s: PSym) =
  strTableAdd(semtab(g, m), s)
  strTableAdd(semtabAll(g, m), s)

proc isCachedModule(g: ModuleGraph; module: int): bool {.inline.} =
  result = module in g.cachedMods

proc isCachedModule*(g: ModuleGraph; m: PSym): bool {.inline.} =
  isCachedModule(g, m.position)

type
  ModuleIter* = object
    modIndex: int
    ti: TIdentIter
    importHidden: bool

proc initModuleIter*(mi: var ModuleIter; g: ModuleGraph; m: PSym; name: PIdent): PSym =
  assert m.kind == skModule
  mi.modIndex = m.position
  mi.importHidden = optImportHidden in m.options
  result = initIdentIter(mi.ti, g.ifaces[mi.modIndex].interfSelect(mi.importHidden), name)

proc nextModuleIter*(mi: var ModuleIter; g: ModuleGraph): PSym =
  result = nextIdentIter(mi.ti, g.ifaces[mi.modIndex].interfSelect(mi.importHidden))

iterator allSyms*(g: ModuleGraph; m: PSym): PSym =
  let importHidden = optImportHidden in m.options
  for s in g.ifaces[m.position].interfSelect(importHidden).data:
    if s != nil:
      yield s

proc someSym*(g: ModuleGraph; m: PSym; name: PIdent): PSym =
  let importHidden = optImportHidden in m.options
  result = strTableGet(g.ifaces[m.position].interfSelect(importHidden), name)

proc someSymAmb*(g: ModuleGraph; m: PSym; name: PIdent; amb: var bool): PSym =
  let importHidden = optImportHidden in m.options
  var ti: TIdentIter = default(TIdentIter)
  result = initIdentIter(ti, g.ifaces[m.position].interfSelect(importHidden), name)
  if result != nil and nextIdentIter(ti, g.ifaces[m.position].interfSelect(importHidden)) != nil:
    # another symbol exists with same name
    amb = true

proc systemModuleSym*(g: ModuleGraph; name: PIdent): PSym =
  result = someSym(g, g.systemModule, name)

iterator systemModuleSyms*(g: ModuleGraph; name: PIdent): PSym =
  var mi: ModuleIter = default(ModuleIter)
  var r = initModuleIter(mi, g, g.systemModule, name)
  while r != nil:
    yield r
    r = nextModuleIter(mi, g)

iterator typeInstCacheItems*(g: ModuleGraph; s: PSym): PType =
  if g.typeInstCache.contains(s.itemId):
    let x = addr(g.typeInstCache[s.itemId])
    for t in mitems(x[]):
      yield t

iterator procInstCacheItems*(g: ModuleGraph; s: PSym): PInstantiation =
  if g.procInstCache.contains(s.itemId):
    let x = addr(g.procInstCache[s.itemId])
    for t in mitems(x[]):
      yield t


proc getAttachedOp*(g: ModuleGraph; t: PType; op: TTypeAttachedOp): PSym =
  ## returns the requested attached operation for type `t`. Can return nil
  ## if no such operation exists.
  if g.attachedOps[op].contains(t.itemId):
    result = g.attachedOps[op][t.itemId]
  elif g.config.cmd in {cmdNifC, cmdM}:
    # Fall back to key-based lookup for NIF-loaded hooks
    let key = typeKey(t, g.config, loadTypeCallback, loadSymCallback)
    result = g.loadedOps[op].getOrDefault(key)
    #echo "fallback ", key, " ", op, " ", result
  else:
    result = nil

proc setAttachedOp*(g: ModuleGraph; module: int; t: PType; op: TTypeAttachedOp; value: PSym) =
  ## we also need to record this to the packed module.
  if not g.attachedOps[op].contains(t.itemId):
    let key = typeKey(t, g.config, loadTypeCallback, loadSymCallback)
    # Use key-based deduplication for opsLog because different type objects
    # (e.g. canon vs orig) can have different itemIds but same structural key
    if key notin g.loadedOps[op]:
      # Hooks should be written to the module where the type is defined,
      # not the module that triggered the registration
      let ownerModule = if t.sym != nil: t.sym.itemId.module.int else: module
      g.opsLog.add LogEntry(kind: HookEntry, op: op, module: ownerModule, key: key, sym: value)
      g.loadedOps[op][key] = value
  g.attachedOps[op][t.itemId] = value

proc setAttachedOp*(g: ModuleGraph; module: int; typeId: ItemId; op: TTypeAttachedOp; value: PSym) =
  ## Overload that takes ItemId directly, useful for registering hooks from NIF index.
  g.attachedOps[op][typeId] = value

proc setAttachedOpPartial*(g: ModuleGraph; module: int; t: PType; op: TTypeAttachedOp; value: PSym) =
  ## we also need to record this to the packed module.
  g.attachedOps[op][t.itemId] = value

proc completePartialOp*(g: ModuleGraph; module: int; t: PType; op: TTypeAttachedOp; value: PSym) {.inline.} =
  discard

iterator getDispatchers*(g: ModuleGraph): PSym =
  for i in g.dispatchers.mitems:
    yield i

proc addDispatchers*(g: ModuleGraph, value: PSym) =
  # TODO: add it for packed modules
  g.dispatchers.add value

iterator resolveLazySymSeq(g: ModuleGraph, list: var seq[PSym]): PSym =
  for it in list.mitems:
    yield it

proc setMethodsPerType*(g: ModuleGraph; id: ItemId, methods: seq[PSym]) =
  # TODO: add it for packed modules
  g.methodsPerType[id] = methods

proc addNifReplayAction*(g: ModuleGraph; module: int32; n: PNode) =
  ## Stores a replay action for NIF-based incremental compilation.
  g.nifReplayActions.mgetOrPut(module, @[]).add n

iterator getMethodsPerType*(g: ModuleGraph; t: PType): PSym =
  if g.methodsPerType.contains(t.itemId):
    for it in mitems g.methodsPerType[t.itemId]:
      yield it

proc getToStringProc*(g: ModuleGraph; t: PType): PSym =
  result = g.enumToStringProcs[t.itemId]
  assert result != nil

proc setToStringProc*(g: ModuleGraph; t: PType; value: PSym) =
  g.enumToStringProcs[t.itemId] = value
  let key = typeKey(t, g.config, loadTypeCallback, loadSymCallback)
  let ownerModule = if t.sym != nil: t.sym.itemId.module.int else: value.itemId.module.int
  g.opsLog.add LogEntry(kind: EnumToStrEntry, module: ownerModule, key: key, sym: value)

iterator methodsForGeneric*(g: ModuleGraph; t: PType): (int, PSym) =
  if g.methodsPerGenericType.contains(t.itemId):
    for it in mitems g.methodsPerGenericType[t.itemId]:
      yield (it[0], it[1])

proc addMethodToGeneric*(g: ModuleGraph; module: int; t: PType; col: int; m: PSym) =
  g.methodsPerGenericType.mgetOrPut(t.itemId, @[]).add (col, m)
  let key = typeKey(t, g.config, loadTypeCallback, loadSymCallback)
  let ownerModule = if t.sym != nil: t.sym.itemId.module.int else: module
  g.opsLog.add LogEntry(kind: MethodEntry, module: ownerModule, key: key, sym: m)

proc logGenericInstance*(g: ModuleGraph; inst: PSym) =
  ## Log a generic instance so it gets written to the NIF file.
  ## This is needed when generic instances are created during compile-time
  ## evaluation and may be referenced from other modules compiled in the same run.
  if g.config.cmd in {cmdNifC, cmdM}:
    let ownerModule = inst.itemId.module.int
    g.opsLog.add LogEntry(kind: GenericInstEntry, module: ownerModule, sym: inst)

proc hasDisabledAsgn*(g: ModuleGraph; t: PType): bool =
  let op = getAttachedOp(g, t, attachedAsgn)
  result = op != nil and sfError in op.flags

proc copyTypeProps*(g: ModuleGraph; module: int; dest, src: PType) =
  for k in low(TTypeAttachedOp)..high(TTypeAttachedOp):
    let op = getAttachedOp(g, src, k)
    if op != nil:
      setAttachedOp(g, module, dest, k, op)

proc loadCompilerProc*(g: ModuleGraph; name: string): PSym =
  result = nil
  if g.config.symbolFiles == disabledSf and optWithinConfigSystem notin g.config.globalOptions:
    # For NIF-based compilation, search in loaded NIF modules
    when not defined(nimKochBootstrap):
      # Try to resolve from NIF for both cmdNifC and cmdM (which uses NIF files)
      if g.config.cmd in {cmdNifC, cmdM}:
        # First try system module (most compilerprocs are there)
        let systemFileIdx = g.config.m.systemFileIdx
        if systemFileIdx != InvalidFileIdx and not g.withinSystem:
          # Only try to load from NIF if the file exists (it may not during initial ic build)
          result = tryResolveCompilerProc(ast.program, name, systemFileIdx)
          if result != nil:
            strTableAdd(g.compilerprocs, result)
            return result

        # Try threadpool module (some compilerprocs like FlowVar are there)
        # Find threadpool module by searching loaded modules
        for moduleIdx in 0..<g.ifaces.len:
          let module = g.ifaces[moduleIdx].module
          if module != nil and module.name.s == "threadpool":
            let threadpoolFileIdx = module.position.FileIndex
            result = tryResolveCompilerProc(ast.program, name, threadpoolFileIdx)
            if result != nil:
              strTableAdd(g.compilerprocs, result)
              return result
    return nil

proc `$`*(u: SigHash): string =
  toBase64a(cast[cstring](unsafeAddr u), sizeof(u))

proc `==`*(a, b: SigHash): bool =
  result = equalMem(unsafeAddr a, unsafeAddr b, sizeof(a))

proc hash*(u: SigHash): Hash =
  result = 0
  for x in 0..3:
    result = (result shl 8) or u.MD5Digest[x].int

proc hash*(x: FileIndex): Hash {.borrow.}

template getPContext(): untyped =
  when c is PContext: c
  else: c.c

when defined(nimsuggest):
  template onUse*(info: TLineInfo; s: PSym; isGenericInstance = false) = discard
  template onDefResolveForward*(info: TLineInfo; s: PSym) = discard
else:
  template onUse*(info: TLineInfo; s: PSym; isGenericInstance = false) = discard
  template onDef*(info: TLineInfo; s: PSym) = discard
  template onDefResolveForward*(info: TLineInfo; s: PSym) = discard

proc stopCompile*(g: ModuleGraph): bool {.inline.} =
  result = g.doStopCompile != nil and g.doStopCompile()

proc createMagic*(g: ModuleGraph; idgen: IdGenerator; name: string, m: TMagic): PSym =
  result = newSym(skProc, getIdent(g.cache, name), idgen, nil, unknownLineInfo, {})
  result.magic = m
  result.flags = {sfNeverRaises}

proc createMagic(g: ModuleGraph; name: string, m: TMagic): PSym =
  result = createMagic(g, g.idgen, name, m)

proc uniqueModuleName*(conf: ConfigRef; m: PSym): string =
  ## The unique module name is guaranteed to only contain {'A'..'Z', 'a'..'z', '0'..'9', '_'}
  ## so that it is useful as a C identifier snippet.
  let fid = FileIndex(m.position)
  let path = AbsoluteFile toFullPath(conf, fid)
  var isLib = false
  var rel = ""
  if path.string.startsWith(conf.libpath.string):
    isLib = true
    rel = relativeTo(path, conf.libpath).string
  else:
    rel = relativeTo(path, conf.projectPath).string

  if not isLib and not belongsToProjectPackage(conf, m):
    # special handlings for nimble packages
    when DirSep == '\\':
      let rel2 = replace(rel, '\\', '/')
    else:
      let rel2 = rel
    const pkgs2 = "pkgs2/"
    var start = rel2.find(pkgs2)
    if start >= 0:
      start += pkgs2.len
      start += skipUntil(rel2, {'/'}, start)
      if start+1 < rel2.len:
        rel = "pkg/" & rel2[start+1..<rel.len] # strips paths

  let trunc = if rel.endsWith(".nim"): rel.len - len(".nim") else: rel.len
  result = newStringOfCap(trunc)
  for i in 0..<trunc:
    let c = rel[i]
    case c
    of 'a'..'z', '0'..'9':
      result.add c
    of {os.DirSep, os.AltSep}:
      result.add 'Z' # because it looks a bit like '/'
    of '.':
      result.add 'O' # a circle
    else:
      # We mangle upper letters too so that there cannot
      # be clashes with our special meanings of 'Z' and 'O'
      result.addInt ord(c)

proc registerModule*(g: ModuleGraph; m: PSym) =
  assert m != nil
  assert m.kind == skModule

  if m.position >= g.ifaces.len:
    setLen(g.ifaces, m.position + 1)

  if g.ifaces[m.position].module == nil:
    g.ifaces[m.position] = Iface(module: m, converters: @[], patterns: @[],
                                uniqueName: rope(uniqueModuleName(g.config, m)))
    initStrTables(g, m)

proc registerModuleById*(g: ModuleGraph; m: FileIndex) =
  registerModule(g, g.ifaces[int m].module)

proc initOperators*(g: ModuleGraph): Operators =
  # These are safe for IC.
  # Public because it's used by DrNim.
  result = Operators(
    opLe: createMagic(g, "<=", mLeI),
    opLt: createMagic(g, "<", mLtI),
    opAnd: createMagic(g, "and", mAnd),
    opOr: createMagic(g, "or", mOr),
    opIsNil: createMagic(g, "isnil", mIsNil),
    opEq: createMagic(g, "==", mEqI),
    opAdd: createMagic(g, "+", mAddI),
    opSub: createMagic(g, "-", mSubI),
    opMul: createMagic(g, "*", mMulI),
    opDiv: createMagic(g, "div", mDivI),
    opLen: createMagic(g, "len", mLengthSeq),
    opNot: createMagic(g, "not", mNot),
    opContains: createMagic(g, "contains", mInSet)
  )

proc initModuleGraphFields(result: ModuleGraph) =
  # A module ID of -1 means that the symbol is not attached to a module at all,
  # but to the module graph:
  result.idgen = IdGenerator(module: -1'i32, symId: 0'i32, typeId: 0'i32)
  result.packageSyms = initStrTable()
  result.deps = initIntSet()
  result.importDeps = initTable[FileIndex, seq[FileIndex]]()
  result.ifaces = @[]
  result.importStack = @[]
  result.inclToMod = initTable[FileIndex, FileIndex]()
  result.owners = @[]
  result.suggestSymbols = initTable[FileIndex, SuggestFileSymbolDatabase]()
  result.suggestErrors = initTable[FileIndex, seq[Suggest]]()
  result.methods = @[]
  result.compilerprocs = initStrTable()
  result.exposed = initStrTable()
  result.packageTypes = initStrTable()
  result.emptyNode = newNode(nkEmpty)
  result.cacheSeqs = initTable[string, PNode]()
  result.cacheCounters = initTable[string, BiggestInt]()
  result.cacheTables = initTable[string, BTree[string, PNode]]()
  result.canonTypes = initTable[SigHash, PType]()
  result.symBodyHashes = initTable[int, SigHash]()
  result.operators = initOperators(result)
  result.emittedTypeInfo = initTable[string, FileIndex]()
  result.cachedFiles = newStringTable()
  result.cachedMods = initIntSet()

proc newModuleGraph*(cache: IdentCache; config: ConfigRef): ModuleGraph =
  result = ModuleGraph()
  result.config = config
  result.cache = cache
  initModuleGraphFields(result)
  ast.setupProgram(config, cache)

proc resetAllModules*(g: ModuleGraph) =
  g.packageSyms = initStrTable()
  g.deps = initIntSet()
  g.ifaces = @[]
  g.importStack = @[]
  g.inclToMod = initTable[FileIndex, FileIndex]()
  g.usageSym = nil
  g.owners = @[]
  g.methods = @[]
  g.compilerprocs = initStrTable()
  g.exposed = initStrTable()
  initModuleGraphFields(g)

proc getModule*(g: ModuleGraph; fileIdx: FileIndex): PSym =
  if fileIdx.int32 >= 0 and fileIdx.int32 < g.ifaces.len:
    result = g.ifaces[fileIdx.int32].module
  else:
    result = nil

proc moduleOpenForCodegen*(g: ModuleGraph; m: FileIndex): bool {.inline.} =
  result = true

proc dependsOn(a, b: int): int {.inline.} = (a shl 15) + b

proc addDep*(g: ModuleGraph; m: PSym, dep: FileIndex) =
  assert m.position == m.info.fileIndex.int32
  if g.suggestMode:
    g.deps.incl m.position.dependsOn(dep.int)
    # we compute the transitive closure later when querying the graph lazily.
    # this improves efficiency quite a lot:
    #invalidTransitiveClosure = true

proc addIncludeDep*(g: ModuleGraph; module, includeFile: FileIndex) =
  discard hasKeyOrPut(g.inclToMod, includeFile, module)

proc parentModule*(g: ModuleGraph; fileIdx: FileIndex): FileIndex =
  ## returns 'fileIdx' if the file belonging to this index is
  ## directly used as a module or else the module that first
  ## references this include file.
  if fileIdx.int32 >= 0 and fileIdx.int32 < g.ifaces.len and g.ifaces[fileIdx.int32].module != nil:
    result = fileIdx
  else:
    result = g.inclToMod.getOrDefault(fileIdx)

proc transitiveClosure(g: var IntSet; n: int) =
  # warshall's algorithm
  for k in 0..<n:
    for i in 0..<n:
      for j in 0..<n:
        if i != j and not g.contains(i.dependsOn(j)):
          if g.contains(i.dependsOn(k)) and g.contains(k.dependsOn(j)):
            g.incl i.dependsOn(j)

proc markDirty*(g: ModuleGraph; fileIdx: FileIndex) =
  let m = g.getModule fileIdx
  if m != nil:
    g.suggestSymbols.del(fileIdx)
    g.suggestErrors.del(fileIdx)
    incl m.flagsImpl, sfDirty

proc unmarkAllDirty*(g: ModuleGraph) =
  for i in 0i32..<g.ifaces.len.int32:
    let m = g.ifaces[i].module
    if m != nil:
      m.flagsImpl.excl sfDirty

proc isDirty*(g: ModuleGraph; m: PSym): bool =
  result = g.suggestMode and sfDirty in m.flags

proc markClientsDirty*(g: ModuleGraph; fileIdx: FileIndex) =
  # we need to mark its dependent modules D as dirty right away because after
  # nimsuggest is done with this module, the module's dirty flag will be
  # cleared but D still needs to be remembered as 'dirty'.
  if g.invalidTransitiveClosure:
    g.invalidTransitiveClosure = false
    transitiveClosure(g.deps, g.ifaces.len)

  # every module that *depends* on this file is also dirty:
  for i in 0i32..<g.ifaces.len.int32:
    if g.deps.contains(i.dependsOn(fileIdx.int)):
      g.markDirty(FileIndex(i))

proc needsCompilation*(g: ModuleGraph): bool =
  # every module that *depends* on this file is also dirty:
  result = false
  for i in 0i32..<g.ifaces.len.int32:
    let m = g.ifaces[i].module
    if m != nil:
      if sfDirty in m.flags:
        return true

proc needsCompilation*(g: ModuleGraph, fileIdx: FileIndex): bool =
  result = false
  let module = g.getModule(fileIdx)
  if module != nil and g.isDirty(module):
    return true

  for i in 0i32..<g.ifaces.len.int32:
    let m = g.ifaces[i].module
    if m != nil and g.isDirty(m) and g.deps.contains(fileIdx.int32.dependsOn(i)):
      return true

proc getBody*(g: ModuleGraph; s: PSym): PNode {.inline.} =
  result = s.ast[bodyPos]
  assert result != nil

when not defined(nimKochBootstrap):
  proc moduleFromNifFile*(g: ModuleGraph; fileIdx: FileIndex;
                          flags: set[LoadFlag] = {}): PrecompiledModule =
    ## Returns 'nil' if the module needs to be recompiled.
    ## Loads module from NIF file when optCompress is enabled.
    ## When loadFullAst is true, loads the complete module AST for code generation.
    if not fileExists(toNifFilename(g.config, fileIdx)):
      return PrecompiledModule(module: nil)

    # Create module symbol
    let filename = AbsoluteFile toFullPath(g.config, fileIdx)

    let m = PSym(
      kindImpl: skModule,
      itemId: ItemId(module: int32(fileIdx), item: 0'i32),
      name: getIdent(g.cache, splitFile(filename).name),
      infoImpl: newLineInfo(fileIdx, 1, 1),
      positionImpl: int(fileIdx))
    setOwner(m, getPackage(g.config, g.cache, fileIdx))
    # Register module in graph
    registerModule(g, m)

    result = loadNifModule(ast.program, fileIdx,
                           g.ifaces[fileIdx.int].interf,
                           g.ifaces[fileIdx.int].interfHidden, flags)
    result.module = m

    # Mark module as cached
    g.cachedMods.incl fileIdx.int

    # Register hooks from NIF index with the module graph
    for x in result.logOps:
      case x.kind
      of HookEntry:
        g.loadedOps[x.op][x.key] = x.sym
      of ConverterEntry:
        g.ifaces[fileIdx.int].converters.add x.sym
      of MethodEntry:
        discard "todo"
      of EnumToStrEntry:
        discard "todo"
      of GenericInstEntry:
        raiseAssert "GenericInstEntry should not be in the NIF index"
    # Register methods per type from NIF index
    discard "todo"

proc configComplete*(g: ModuleGraph) =
  #rememberStartupConfig(g.startupPackedConfig, g.config)
  discard

proc onProcessing*(graph: ModuleGraph, fileIdx: FileIndex, moduleStatus: string, fromModule: PSym) =
  let conf = graph.config
  let isNimscript = conf.isDefined("nimscript")
  if (not isNimscript) or hintProcessing in conf.cmdlineNotes:
    let path = toFilenameOption(conf, fileIdx, conf.filenameOption)
    let indent = ">".repeat(graph.importStack.len)
    let fromModule2 = if fromModule != nil: $fromModule.name.s else: "(toplevel)"
    let mode = if isNimscript: "(nims) " else: ""
    rawMessage(conf, hintProcessing, "$#$# $#: $#: $#" % [mode, indent, fromModule2, moduleStatus, path])

proc getPackage*(graph: ModuleGraph; fileIdx: FileIndex): PSym =
  ## Returns a package symbol for yet to be defined module for fileIdx.
  ## The package symbol is added to the graph if it doesn't exist.
  let pkgSym = getPackage(graph.config, graph.cache, fileIdx)
  # check if the package is already in the graph
  result = graph.packageSyms.strTableGet(pkgSym.name)
  if result == nil:
     # the package isn't in the graph, so create and add it
    result = pkgSym
    graph.packageSyms.strTableAdd(pkgSym)

proc belongsToStdlib*(graph: ModuleGraph, sym: PSym): bool =
  ## Check if symbol belongs to the 'stdlib' package.
  sym.getPackageSymbol.getPackageId == graph.systemModule.getPackageId

proc fileSymbols*(graph: ModuleGraph, fileIdx: FileIndex): SuggestFileSymbolDatabase =
  result = graph.suggestSymbols.getOrDefault(fileIdx, newSuggestFileSymbolDatabase(fileIdx, optIdeExceptionInlayHints in graph.config.globalOptions))
  doAssert(result.fileIndex == fileIdx)

iterator suggestSymbolsIter*(g: ModuleGraph): SymInfoPair =
  for xs in g.suggestSymbols.values:
    for i in xs.lineInfo.low..xs.lineInfo.high:
      yield xs.getSymInfoPair(i)

iterator suggestErrorsIter*(g: ModuleGraph): Suggest =
  for xs in g.suggestErrors.values:
    for x in xs:
      yield x