(**
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *)

module Ast = Flow_ast
module File_sig = File_sig.With_Loc

open Utils_js
open ServerEnv

open FindRefsUtils
open GetDefUtils

let add_ref_kind kind = Core_list.map ~f:(fun loc -> (kind, loc))

module LiteralToPropLoc : sig
  (* Returns a map from object_literal_loc to prop_loc, for all object literals which contain the
   * given property name. *)
  val make: (Loc.t, Loc.t) Ast.program -> prop_name: string -> Loc.t LocMap.t
end = struct
  class locmap_builder prop_name = object(this)
    inherit [Loc.t LocMap.t] object_key_visitor ~init:LocMap.empty
    method! private visit_object_key
        (literal_loc: Loc.t)
        (key: (Loc.t, Loc.t) Ast.Expression.Object.Property.key) =
      let open Ast.Expression.Object in
      match key with
      | Property.Identifier (prop_loc, name) when name = prop_name ->
          this#update_acc (fun map -> LocMap.add literal_loc prop_loc map)
        (* TODO consider supporting other property keys (e.g. literals). Also update the
         * optimization in property_access_searcher below when this happens. *)
      | _ -> ()
  end

  let make ast ~prop_name =
    let builder = new locmap_builder prop_name in
    builder#eval builder#program ast
end

let set_get_refs_hook potential_refs potential_matching_literals target_name =
  let hook ret _ctxt name loc ty =
    begin if name = target_name then
      (* Replace previous bindings of `loc`. We should always use the result of the last call to
       * the hook for a given location. For details see the comment on the generate_tests function
       * in flow_js.ml *)
      potential_refs := ALocMap.add loc ty !potential_refs
    end;
    ret
  in
  let lval_hook cx name loc = function
    (* Treat destructuring as a property access *)
    | Type_inference_hooks_js.Parent ty -> hook () cx name loc ty
    | _ -> ()
  in
  let obj_to_obj_hook _ctxt obj1 obj2 =
    let open Type in
    match get_object_literal_loc obj1, obj2 with
    | Some loc, DefT (_, ObjT _) ->
      let entry = (loc, obj2) in
      potential_matching_literals := entry:: !potential_matching_literals
    | _ -> ()
  in

  Type_inference_hooks_js.set_member_hook (hook false);
  Type_inference_hooks_js.set_call_hook (hook ());
  Type_inference_hooks_js.set_lval_hook (lval_hook);
  Type_inference_hooks_js.set_obj_to_obj_hook obj_to_obj_hook

(* Returns `true` iff the given type is a reference to the symbol we are interested in *)
let type_matches_locs cx ty prop_def_info name =
  let rec def_loc_matches_locs = function
  | FoundClass ty_def_locs ->
    prop_def_info |> Nel.exists begin function
      | Object _ -> false
      | Class loc ->
        (* Only take the first extracted def loc -- that is, the one for the actual definition
         * and not overridden implementations, and compare it to the list of def locs we are
         * interested in *)
        loc = Nel.hd ty_def_locs
    end
  | FoundObject loc ->
    prop_def_info |> Nel.exists begin function
    | Class _ -> false
    | Object def_loc -> loc = def_loc
    end
  | FoundUnion def_locs ->
    def_locs
    |> Nel.map def_loc_matches_locs
    |> Nel.fold_left ( || ) false
  (* TODO we may want to surface AnyType results somehow since we can't be sure whether they
   * are references or not. For now we'll leave them out. *)
  | NoDefFound | UnsupportedType | AnyType -> false
  in
  extract_def_loc cx ty name >>| def_loc_matches_locs

let process_prop_refs cx potential_refs file_key prop_def_info name =
  potential_refs |>
    ALocMap.bindings |>
    Core_list.map ~f:begin fun (ref_loc, ty) ->
      type_matches_locs cx ty prop_def_info name
      >>| function
      | true -> Some (ALoc.to_loc ref_loc)
      | false -> None
    end
    |> Result.all
    |> Result.map_error ~f:(fun err ->
        Printf.sprintf
          "Encountered while finding refs in `%s`: %s"
          (File_key.to_string file_key)
          err
      )
    >>| begin fun refs ->
      refs
      |> ListUtils.cat_maybes
      |> add_ref_kind FindRefsTypes.PropertyAccess
    end

let property_find_refs_in_file ~reader options ast_info file_key def_info name =
  let potential_refs: Type.t ALocMap.t ref = ref ALocMap.empty in
  let potential_matching_literals: (Loc.t * Type.t) list ref = ref [] in
  let (ast, file_sig, info) = ast_info in
  let info = Docblock.set_flow_mode_for_ide_command info in
  let local_defs =
    Nel.to_list (all_locs_of_property_def_info def_info)
    |> List.filter (fun loc -> loc.Loc.source = Some file_key)
    |> add_ref_kind FindRefsTypes.PropertyDefinition
  in
  let has_symbol = PropertyAccessSearcher.search name ast in
  if not has_symbol then
    Ok local_defs
  else begin
    set_get_refs_hook potential_refs potential_matching_literals name;
    let (cx, _) = Merge_service.merge_contents_context
      ~reader options file_key ast info file_sig
    in
    unset_hooks ();
    let literal_prop_refs_result =
      (* Lazy to avoid this computation if there are no potentially-relevant object literals to
       * examine *)
      let prop_loc_map = lazy (LiteralToPropLoc.make ast name) in
      let get_prop_loc_if_relevant (obj_loc, into_type) =
        type_matches_locs cx into_type def_info name
        >>| function
        | false -> None
        | true -> LocMap.get obj_loc (Lazy.force prop_loc_map)
      in
      !potential_matching_literals
      |> Core_list.map ~f:get_prop_loc_if_relevant
      |> Result.all
      >>| begin fun refs ->
        refs
        |> ListUtils.cat_maybes
        |> add_ref_kind FindRefsTypes.PropertyDefinition
      end
    in
    literal_prop_refs_result
    >>= begin fun literal_prop_refs_result ->
      process_prop_refs cx !potential_refs file_key def_info name
      >>| (@) local_defs
      >>| (@) literal_prop_refs_result
    end
  end

let export_find_refs_in_file ~reader ast_info file_key def_loc =
  let open File_sig in
  let (_, file_sig, _) = ast_info in
  let is_relevant module_ref =
    Loc.source def_loc = file_key_of_module_ref ~reader file_key module_ref
  in
  let locs = List.fold_left begin fun acc require ->
    match require with
    | Require { source = (_, module_ref); require_loc; _ } ->
      if is_relevant module_ref then
        require_loc::acc
      else
        acc
    | _ -> acc
  end [] file_sig.module_sig.requires in
  let locs =
    if Loc.source def_loc = Some file_key then
      def_loc::locs
    else
      locs
  in
  Ok locs

let add_related_bindings ast_info refs =
  let (ast, file_sig, _) = ast_info in
  let locs = Core_list.map ~f:snd refs in
  let related_bindings = ImportExportSymbols.find_related_symbols file_sig locs in
  List.fold_left begin fun acc loc ->
    let new_refs =
      VariableFindRefs.local_find_refs ast loc
      |> Option.value_map ~default:[] ~f:(fun ((_, refs), _) -> refs)
    in
    List.rev_append new_refs acc
  end refs related_bindings

let find_refs_in_file ~reader options ast_info file_key def_info =
  let refs = match def_info with
  | Property (def_info, name) ->
    property_find_refs_in_file ~reader options ast_info file_key def_info name
  | CJSExport loc ->
    export_find_refs_in_file ~reader ast_info file_key loc >>| fun refs ->
    add_ref_kind FindRefsTypes.Other refs
  in
  refs >>| add_related_bindings ast_info

let find_refs_in_multiple_files ~reader genv all_deps def_info =
  let {options; workers} = genv in
  let dep_list: File_key.t list = FilenameSet.elements all_deps in
  let node_modules_containers = !Files.node_modules_containers in
  let%lwt result = MultiWorkerLwt.call workers
    ~job: begin fun _acc deps ->
      (* Yay for global mutable state *)
      Files.node_modules_containers := node_modules_containers;
      deps |> Core_list.map ~f:begin fun dep ->
        get_ast_result ~reader dep >>= fun ast_info ->
        find_refs_in_file ~reader options ast_info dep def_info
      end
    end
    ~merge: (fun refs acc -> List.rev_append refs acc)
    ~neutral: []
    ~next: (MultiWorkerLwt.next workers dep_list)
  in
  (* The types got a little too complicated here. Writing out the intermediate types makes it a
   * bit clearer. *)
  let result: (FindRefsTypes.single_ref list list, string) Result.t = Result.all result in
  let result: (FindRefsTypes.single_ref list, string) Result.t = result >>| List.concat in
  Lwt.return result

(* Get the source for each loc. Error if any loc is missing a source. *)
let files_of_locs (locs: Loc.t Nel.t) : (FilenameSet.t, string) result =
  let files_result =
    locs
    |> Nel.map (fun loc -> loc.Loc.source)
    |> Nel.map (Result.of_option ~error:"Expected a location with a source file")
    |> Nel.result_all
  in
  files_result >>| fun files ->
  Nel.to_list files |> FilenameSet.of_list

(* Error if the set is empty *)
let nel_of_filename_set (set: FilenameSet.t) : (File_key.t Nel.t, string) result =
  set
  |> FilenameSet.elements
  |> Nel.of_list
  |> Result.of_option ~error:"Expected a nonempty filename set"

(* Returns the file(s) at which we should begin looking downstream for references. *)
let roots_of_def_info def_info : (File_key.t Nel.t, string) result =
  let root_locs = all_locs_of_def_info def_info in
  files_of_locs root_locs >>= nel_of_filename_set

let deps_of_file_key
    ~reader genv env (file_key: File_key.t) : (FilenameSet.t, string) result Lwt.t =
  let {options; workers} = genv in
  File_key.to_path file_key %>>= fun path ->
  let fileinput = File_input.FileName path in
  File_input.content_of_file_input fileinput %>>| fun content ->
  let%lwt all_deps, _ = get_dependents ~reader options workers env file_key content in
  Lwt.return all_deps

let deps_of_file_keys
    ~reader genv env (file_keys: File_key.t list) : (FilenameSet.t, string) result Lwt.t =
  (* We need to use map_s (rather than map_p) because we cannot interleave calls into
   * MultiWorkers. *)
  let%lwt deps_result = Lwt_list.map_s (deps_of_file_key ~reader genv env) file_keys in
  Result.all deps_result %>>| fun (deps: FilenameSet.t list) ->
  Lwt.return @@ List.fold_left FilenameSet.union FilenameSet.empty deps

let focus_and_check genv env paths =
  let%lwt new_env, _ =
    Lazy_mode_utils.focus_and_check genv !env paths
  in
  env := new_env;
  Lwt.return_unit

let focus_and_check_filename_set genv env files =
  let paths =
    files
    |> FilenameSet.elements
    |> Core_list.map ~f:File_key.to_path
    |> Result.all
  in
  paths %>>| fun paths ->
  Nel.of_list paths
  |> Option.value_map ~default:Lwt.return_unit ~f:(focus_and_check genv env)

(* Returns location pairs such that:
 * - Each location is the definition location for a property with the given
 *   name.
 * - Each pair indicates that the definition locations it contains are related.
 * - For two definition locations to be related, their enclosing object types
 *   must be related.
 * - Two object types are considered related when, in the course of typechecking
 *   the given file, we evaluate an `ObjT ~> ObjT` constraint relating the two
 *   object types.
 * - Note that this can return locations outside of the given file.
*)
let find_related_defs_in_file ~reader options name file =
  let get_single_def_info_pairs_if_relevant cx (t1, t2) =
    map2 (extract_def_loc cx t1 name) (extract_def_loc cx t2 name) ~f:begin fun x y -> match x, y with
    | FoundObject loc1, FoundObject loc2 -> [Object loc1, Object loc2]
    | FoundClass class_locs, FoundObject obj_loc ->
      class_locs
      |> Nel.to_list
      |> Core_list.map ~f:(fun class_loc -> (Class class_loc, Object obj_loc))
    | _ -> []
    (* TODO union types *)
    end
  in
  let related_types: (Type.t * Type.t) list ref = ref [] in
  let hook _cx t1 t2 =
    related_types := (t1, t2)::!related_types
  in
  Type_inference_hooks_js.set_obj_to_obj_hook hook;
  Type_inference_hooks_js.set_instance_to_obj_hook hook;
  let cx_result =
    get_ast_result ~reader file >>| fun (ast, file_sig, docblock) ->
    Merge_service.merge_contents_context
      ~reader options file ast docblock file_sig
  in
  unset_hooks ();
  cx_result >>= fun (cx, _) ->
  let results: (((single_def_info * single_def_info) list) list, string) result =
    !related_types
    |> Core_list.map ~f:(get_single_def_info_pairs_if_relevant cx)
    |> Result.all
  in
  results >>| List.concat

(* Returns all locations which are considered related to the given definition locations. Definition
 * locations are considered related if they refer to a property with the same name, and their
 * enclosing object types appear in a subtype relationship with each other. *)
let find_related_defs
    ~reader
    genv
    env
    (def_info: property_def_info)
    (name: string)
    : (property_def_info, string) result Lwt.t =
  (* Outline:
   * - Create a disjoint set for definition locations
   * - Seed it with every given def_loc
   * - In all files we need to inspect:
   *   - Look for cases where both ObjTs in an ObjT ~> ObjT constraint have a
   *     property with the name we are looking for.
   *   - Add the definition locations of those properties to the disjoint set
   * - Look in the set of related definition locations that we are interested in:
   *   - If any has a source file we have not yet inspected, inspect that file
   *     and all its dependents (less those we have already inspected) as
   *     described above.
   *   - Iterate until we reach a fixed point
   *)
  let {options; workers} = genv in
  let related_defs =
    let uf = UnionFind.of_list (Nel.to_list def_info) in
    let hd, tl = def_info in
    List.iter (UnionFind.union uf hd) tl;
    uf
  in
  let process_files file_set =
    let node_modules_containers = !Files.node_modules_containers in
    let%lwt (result: ((single_def_info * single_def_info) list, string) result list) =
      MultiWorkerLwt.call workers
        ~job: begin fun _acc files ->
          Files.node_modules_containers := node_modules_containers;
          Core_list.map ~f:(find_related_defs_in_file ~reader options name) files
        end
        ~merge: List.rev_append
        ~neutral: []
        ~next: (MultiWorkerLwt.next workers (FilenameSet.elements file_set))
    in
    Result.all result %>>| fun (pairs: (single_def_info * single_def_info) list list) ->
    List.iter (List.iter (fun (x, y) -> UnionFind.union related_defs x y)) pairs;
    Lwt.return_unit
  in
  let get_unchecked_roots current_def_info checked_files =
    current_def_info |> all_locs_of_property_def_info |> files_of_locs >>| fun roots ->
    FilenameSet.diff roots checked_files
  in
  let get_files_to_check unchecked_roots checked_files =
    let%lwt deps = deps_of_file_keys ~reader genv env (FilenameSet.elements unchecked_roots) in
    deps %>>| fun deps ->
    Lwt.return (
      FilenameSet.union
        (FilenameSet.diff deps checked_files)
        unchecked_roots
    )
  in
  let rec loop current_def_info checked_files =
    get_unchecked_roots current_def_info checked_files %>>= fun unchecked_roots ->
    if FilenameSet.is_empty unchecked_roots then
      Lwt.return (Ok current_def_info)
    else begin
      let%lwt result = focus_and_check_filename_set genv env unchecked_roots in
      result %>>= fun () ->
      let%lwt files_to_check = get_files_to_check unchecked_roots checked_files in
      files_to_check %>>= fun files_to_check ->
      let%lwt check_result = process_files files_to_check in
      check_result %>>= fun () ->
      let checked_files = FilenameSet.union checked_files files_to_check in
      let current_def_info =
        let updated_def_info = UnionFind.members related_defs (Nel.hd current_def_info) in
        Nel.of_list updated_def_info
        |> Result.of_option ~error:"Unexpected empty list"
      in
      current_def_info %>>= fun current_def_info ->
      loop current_def_info checked_files
    end
  in
  loop def_info FilenameSet.empty

let find_refs_global ~reader genv env multi_hop def_info =
  let%lwt def_info =
    if multi_hop then
      match def_info with
      | Property (property_def_info, name) ->
        let%lwt result = find_related_defs ~reader genv env property_def_info name in
        result %>>| fun x -> Lwt.return @@ Property (x, name)
      | CJSExport _ -> Lwt.return (Ok def_info)
    else
      Lwt.return (Ok def_info)
  in
  def_info %>>= fun def_info ->
  roots_of_def_info def_info %>>= fun root_file_keys ->
  let root_file_paths_result =
    Nel.map File_key.to_path root_file_keys
    |> Nel.result_all
  in
  root_file_paths_result %>>= fun root_file_paths ->
  let%lwt () = focus_and_check genv env root_file_paths in
  let%lwt deps_result = deps_of_file_keys ~reader genv env (Nel.to_list root_file_keys) in
  deps_result %>>= fun deps ->
  let dependent_file_count = FilenameSet.cardinal deps in
  let relevant_files =
    Nel.to_list root_file_keys
    |> FilenameSet.of_list
    |> FilenameSet.union deps
  in
  Hh_logger.info
    "find-refs: searching %d dependent modules for references"
    dependent_file_count;
  let%lwt refs = find_refs_in_multiple_files ~reader genv relevant_files def_info in
  refs %>>| fun refs ->
  Lwt.return @@ Some ((display_name_of_def_info def_info, refs), Some dependent_file_count)

let find_refs_local ~reader genv file_key content def_info =
  compute_ast_result genv.options file_key content >>= fun ast_info ->
  find_refs_in_file ~reader genv.options ast_info file_key def_info >>= fun refs ->
  Ok (Some ((display_name_of_def_info def_info, refs), None))

let find_refs ~reader genv env ~content file_key def_info ~global ~multi_hop =
  def_info %>>= fun def_info_opt ->
  match def_info_opt with
    | None -> Lwt.return (Ok None)
    | Some def_info ->
        if global || multi_hop then
          find_refs_global ~reader genv env multi_hop def_info
        else
          Lwt.return @@ find_refs_local ~reader genv file_key content def_info
