module Grep = Grep
module Common = Common
open Notty
module Help_screen = Help_screen

type state =
  { pos : int * int
  ; scroll : int
  ; content : (string * string) array
  ; content_pretty : string array
  ; goto_headlines : (unit -> unit) -> unit
  ; goto_done : (unit -> unit) -> unit
  }

let title = I.strf ~attr:A.(st bold) "%s" "Todo View" |> I.pad ~l:0 ~t:0
let content_start = 2

let init ~goto_done ~goto_headlines =
  let content = Grep.get_todos () |> Grep.parse_todo_string in
  let content_pretty = Grep.pretty_format_todo content in
  { pos = 0, content_start
  ; scroll = 0
  ; content = content |> Array.of_list
  ; content_pretty = content_pretty |> Array.of_list
  ; goto_headlines
  ; goto_done
  }


let load_todos () =
  let todo_content = Grep.get_todos () |> Grep.parse_todo_string in
  let todo_pretty = Grep.pretty_format_todo todo_content in
  todo_content, todo_pretty


let rec render
  t
  ({ pos; scroll; content; content_pretty; goto_headlines; goto_done } as state)
  =
  let x, y = pos in
  let content_position = y - content_start in
  let img =
    let dot = I.string A.(st bold) ">" |> I.pad ~l:0 ~t:(y - scroll)
    and elements =
      Array.mapi
        (fun i el ->
          if i == y - scroll
          then I.strf "%s" el |> I.pad ~l:2 ~t:(i + content_start)
          else I.strf "%s" el |> I.pad ~l:2 ~t:(i + content_start))
        (Array.to_seq content_pretty |> Seq.drop scroll |> Array.of_seq)
    in
    let open I in
    Array.fold_left (fun sum el -> el </> sum) (title </> dot) elements
  in
  let _, size_y = Common.Term.size t in
  Common.Term.image t img;
  let content_end = Array.length content_pretty + (content_start - 1) in
  let scroll_up () =
    let scroll = if y - content_start - scroll = 0 then max (scroll - 1) 0 else scroll in
    render t { state with pos = x, max (y - 1) content_start; scroll }
  in
  let scroll_down () =
    let scroll = if y - scroll >= size_y - 1 then scroll + 1 else scroll in
    render t { state with pos = x, min (y + 1) content_end; scroll }
  in
  match Common.Term.event t with
  | `End | `Key (`Escape, []) | `Key (`ASCII 'q', []) | `Key (`ASCII 'C', [ `Ctrl ]) -> ()
  | `Mouse (`Press (`Scroll s), _, _) ->
    (match s with
     | `Down -> scroll_down ()
     | `Up -> scroll_up ())
  | `Resize _ -> render t state
  | `Mouse ((`Press _ | `Drag), (_, y), _) ->
    render t { state with pos = 0, min y content_end }
  | `Key (`ASCII '?', []) -> Help_screen.render t { go_back = (fun () -> render t state) }
  | `Key (`ASCII 's', []) ->
    let (input_state : Input_screen.state) =
      { screen = img
      ; user_input = ""
      ; prompt = "GREP: "
      ; on_enter =
          (fun tag ->
            let content = Grep.get_tagged_headlines tag () |> Grep.parse_headlines in
            let content_pretty = Grep.pretty_format content in
            Common.Term.cursor t None;
            render t { state with content; content_pretty })
      ; on_cancel =
          (fun _ ->
            Common.Term.cursor t None;
            render t state)
      }
    in
    Input_screen.render t input_state
  | `Key (`ASCII '1', []) -> goto_headlines (fun () -> render t state)
  | `Key (`ASCII '3', []) -> goto_done (fun () -> render t state)
  | `Key (`ASCII 'j', []) | `Key (`ASCII 'N', [ `Ctrl ]) -> scroll_down ()
  | `Key (`ASCII 'k', []) | `Key (`ASCII 'P', [ `Ctrl ]) -> scroll_up ()
  | `Key (`ASCII 't', []) ->
    let selected_file, _ = Array.get content (y - content_start) in
    let _ = Grep.toggle_done selected_file in
    let content, content_pretty = load_todos () in
    render
      t
      { state with
        content = content |> Array.of_list
      ; content_pretty = Array.of_list content_pretty
      }
  | `Key (`Arrow d, _) ->
    (match d with
     | `Up -> scroll_up ()
     | `Down -> scroll_down ()
     | _ -> render t state)
  | `Key (`ASCII 'e', []) | `Key (`Enter, []) ->
    (* Editor might be set with extra args, in that case we need to separate these *)
    let[@warning "-8"] (editor :: args) =
      String.split_on_char ' ' (Sys.getenv "EDITOR")
    in
    let selected_file, _ = Array.get content content_position in
    let full_path_file = Grep.execution_directory ^ "/" ^ selected_file in
    let full_args = Array.append (Array.of_list args) [| full_path_file |] in
    Common.Term.cursor t (Some (0, 0));
    let _ =
      Unix.create_process_env
        editor
        full_args
        (Unix.environment ())
        Unix.stdin
        Unix.stdout
        Unix.stderr
    in
    let rec run_editor () =
      match Unix.wait () with
      | _, _ ->
        Common.Term.cursor t None;
        render t state
      (* Capture resizing events *)
      | exception Unix.Unix_error (Unix.EINTR, _, _) -> run_editor ()
      | exception Unix.Unix_error (_, _, _) -> failwith "ERROR"
    in
    run_editor ()
  | _ -> render t state