/-
Copyright (c) 2020 Microsoft Corporation. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Leonardo de Moura, Sebastian Ullrich
-/
import Lean.Modifiers
import Lean.Elab.Attributes
import Lean.Elab.Exception
import Lean.Elab.DeclUtil

namespace Lean.Elab

def checkNotAlreadyDeclared {m} [Monad m] [MonadEnv m] [MonadExceptOf Exception m] [MonadRef m] [AddErrorMessageContext m] (declName : Name) : m Unit := do
  let env ← getEnv
  if env.contains declName then
    match privateToUserName? declName with
    | none          => throwError! "'{declName}' has already been declared"
    | some declName => throwError! "private declaration '{declName}' has already been declared"
  if env.contains (mkPrivateName env declName) then
    throwError! "a private declaration '{declName}' has already been declared"
  match privateToUserName? declName with
  | none => pure ()
  | some declName =>
    if env.contains declName then
      throwError! "a non-private declaration '{declName}' has already been declared"

inductive Visibility
  | regular | «protected» | «private»

instance : ToString Visibility := ⟨fun
  | Visibility.regular     => "regular"
  | Visibility.«private»   => "private"
  | Visibility.«protected» => "protected"⟩

structure Modifiers :=
  (docString       : Option String := none)
  (visibility      : Visibility := Visibility.regular)
  (isNoncomputable : Bool := false)
  (isPartial       : Bool := false)
  (isUnsafe        : Bool := false)
  (attrs           : Array Attribute := #[])

def Modifiers.isPrivate : Modifiers → Bool
  | { visibility := Visibility.private, .. } => true
  | _                                        => false

def Modifiers.isProtected : Modifiers → Bool
  | { visibility := Visibility.protected, .. } => true
  | _                                          => false

def Modifiers.addAttribute (modifiers : Modifiers) (attr : Attribute) : Modifiers :=
  { modifiers with attrs := modifiers.attrs.push attr }

instance : ToFormat Modifiers := ⟨fun m =>
  let components : List Format :=
    (match m.docString with
     | some str => ["/--" ++ str ++ "-/"]
     | none     => [])
    ++ (match m.visibility with
     | Visibility.regular   => []
     | Visibility.protected => ["protected"]
     | Visibility.private   => ["private"])
    ++ (if m.isNoncomputable then ["noncomputable"] else [])
    ++ (if m.isPartial then ["partial"] else [])
    ++ (if m.isUnsafe then ["unsafe"] else [])
    ++ m.attrs.toList.map (fun attr => fmt attr)
  Format.bracket "{" (Format.joinSep components ("," ++ Format.line)) "}"⟩

instance : ToString Modifiers := ⟨toString ∘ format⟩

section Methods

variables {m : Type → Type} [Monad m] [MonadEnv m] [MonadExceptOf Exception m] [MonadRef m] [AddErrorMessageContext m]

def elabModifiers (stx : Syntax) : m Modifiers := do
  let docCommentStx := stx[0]
  let attrsStx      := stx[1]
  let visibilityStx := stx[2]
  let noncompStx    := stx[3]
  let unsafeStx     := stx[4]
  let partialStx    := stx[5]
  let docString ← match docCommentStx.getOptional? with
    | none   => pure none
    | some s => match s[1] with
      | Syntax.atom _ val => pure (some (val.extract 0 (val.bsize - 2)))
      | _                 => throwErrorAt! s "unexpected doc string {s[1]}"
  let visibility ← match visibilityStx.getOptional? with
    | none   => pure Visibility.regular
    | some v =>
      let kind := v.getKind
      if kind == `Lean.Parser.Command.private then pure Visibility.private
      else if kind == `Lean.Parser.Command.protected then pure Visibility.protected
      else throwErrorAt v "unexpected visibility modifier"
  let attrs ← match attrsStx.getOptional? with
    | none       => pure #[]
    | some attrs => elabDeclAttrs attrs
  pure {
    docString       := docString,
    visibility      := visibility,
    isPartial       := !partialStx.isNone,
    isUnsafe        := !unsafeStx.isNone,
    isNoncomputable := !noncompStx.isNone,
    attrs           := attrs
  }

def applyVisibility (visibility : Visibility) (declName : Name) : m Name := do
  match visibility with
  | Visibility.private =>
    let env ← getEnv
    let declName := mkPrivateName env declName
    checkNotAlreadyDeclared declName
    pure declName
  | Visibility.protected =>
    checkNotAlreadyDeclared declName
    let env ← getEnv
    let env := addProtected env declName
    setEnv env
    pure declName
  | _ =>
    checkNotAlreadyDeclared declName
    pure declName

def mkDeclName (currNamespace : Name) (modifiers : Modifiers) (shortName : Name) : m (Name × Name) := do
  let name := (extractMacroScopes shortName).name
  unless name.isAtomic || isFreshInstanceName name do
    throwError! "atomic identifier expected '{shortName}'"
  let declName := currNamespace ++ shortName
  let declName ← applyVisibility modifiers.visibility declName
  match modifiers.visibility with
  | Visibility.protected =>
    match currNamespace with
    | Name.str _ s _ => pure (declName, Name.mkSimple s ++ shortName)
    | _ => throwError "protected declarations must be in a namespace"
  | _ => pure (declName, shortName)

/-
  `declId` is of the form
  ```
  parser! ident >> optional (".{" >> sepBy1 ident ", " >> "}")
  ```
  but we also accept a single identifier to users to make macro writing more convenient .
-/
def expandDeclIdCore (declId : Syntax) : Name × Syntax :=
  if declId.isIdent then
    (declId.getId, mkNullNode)
  else
    let id             := declId[0].getId
    let optUnivDeclStx := declId[1]
    (id, optUnivDeclStx)

structure ExpandDeclIdResult :=
  (shortName  : Name)
  (declName   : Name)
  (levelNames : List Name)

def expandDeclId (currNamespace : Name) (currLevelNames : List Name) (declId : Syntax) (modifiers : Modifiers) : m ExpandDeclIdResult := do
  -- ident >> optional (".{" >> sepBy1 ident ", " >> "}")
  let (shortName, optUnivDeclStx) := expandDeclIdCore declId
  let levelNames ←
    if optUnivDeclStx.isNone then
      pure currLevelNames
    else
      let extraLevels := optUnivDeclStx[1].getArgs.getEvenElems
      extraLevels.foldlM
        (fun levelNames idStx =>
          let id := idStx.getId
          if levelNames.elem id then
            withRef idStx $ throwAlreadyDeclaredUniverseLevel id
          else
            pure (id :: levelNames))
        currLevelNames
  let (declName, shortName) ← withRef declId $ mkDeclName currNamespace modifiers shortName
  pure { shortName := shortName, declName := declName, levelNames := levelNames }

end Methods

end Lean.Elab