(*
 * SPDX-FileCopyrightText: 2024 The Forester Project Contributors AND The RedPRL Development Team
 *
 * SPDX-License-Identifier: GPL-3.0-or-later OR Apache-2.0 WITH LLVM-exception
 *
 *)

open Forester_prelude
open Forester_core
open Forester_compiler
open Forester_frontend
open Forester_search
open State.Syntax

open struct
  module L = Lsp.Types
  module T = Types

  let ( let* ) = Option.bind
end

let compute ({position; textDocument; _} : L.HoverParams.t) =
  let Lsp_state.{forest; _} = Lsp_state.get () in
  let render = Plain_text_client.string_of_content ~forest in
  let uri =
    URI_scheme.lsp_uri_to_uri ~base:forest.config.url textDocument.uri
  in
  let@ content =
    Option.map
    @~
    match forest.={uri} with
    | None ->
      Reporter.fatal Internal_error
        ~extra_remarks:
          [Asai.Diagnostic.loctextf "%a is not in the index" URI.pp uri]
    | Some tree -> (
      let* {nodes; _} = Tree.to_code tree in
      let* node = Analysis.node_at_code ~position nodes in
      let tree_under_cursor =
        let* {value = addr; _} = Analysis.extract_addr node in
        let uri_under_cursor =
          URI_scheme.named_uri ~base:forest.config.url addr
        in
        State.get_article uri_under_cursor forest
      in
      match tree_under_cursor with
      | Some article -> Some (render article.mainmatter)
      | None ->
        let* doc = Tree.to_doc tree in
        let* search_term = Analysis.word_at ~position doc in
        let results =
          List.map snd @@ Index.search forest.search_index search_term
        in
        Some
          Format.(
            asprintf "Relevant results:@.%a@."
              (pp_print_list ~pp_sep:(fun out () -> fprintf out "@.") URI.pp)
              results))
  in
  L.Hover.create
    ~contents:(`MarkupContent {kind = L.MarkupKind.Markdown; value = content})
    ()