(* Parse the command line. *)

open CalendarLib

open Todo_types
open Todo_utils

open Printf

let usage = "\
todo -- A simple to-do list

  todo [--global-options] [subcommand] [--subcommand-options]

Subcommands:
  todo list [--all] [--retired]
              - List all tasks
  todo today \"description\" [tag[,tag...]]
              - Add a simple task for today, with an optional list of tags
  todo idea \"description\" [tag[,tag...]]
              - Add an long-term idea
  todo [todo|task] deadline [--estimate nr_days] \"description\" [tag[,tag...]]
              - Add a to-do task with a deadline and optional time estimate
  todo retire ID [ID ...]
              - Retire one or more tasks using the task #ID
  todo move ID [today | [todo|task] deadline | ideas | retired | unsorted]
              - Move a task to another list
  todo tag ID tag [--del tag]
              - Add or remove tags from a task
  todo tag-list
              - List all tags and their usage
  todo tag-add tag colour
              - Create a new tag, with a colour
  todo tag-del tag
              - Delete a tag (must be unused)
  todo tag-colour tag colour
              - Change the colour of a tag

Tag colours may be:  black  blue  green  cyan  red  purple  yellow

Examples:
  todo today \"Eat breakfast\" personal,food
  todo task 2019-31-12 \"Prepare for next decade\"
  todo idea \"Write a to-do manager\" work
  todo list

Options:"

(* Parse the command line. *)
let parse_command_line () =
  let print_version_and_exit () =
    printf "%s %s\n" Todo_config.package_name Todo_config.package_version;
    exit 0
  in

  let list_all = ref false in
  let list_retired = ref false in
  let tag_del = ref [] in
  let add_tag_del tag = tag_del := tag :: !tag_del in
  let todo_estimate = ref None in
  let set_todo_estimate days =
    todo_estimate := Some (Calendar.Period.day days)
  in

  (* Per-subcommand specs. *)
  let idea_spec =
    Arg.align [
    ] in
  let list_spec =
    Arg.align [
      "--all", Arg.Set list_all, " List all tasks including retired";
      "--retired", Arg.Set list_retired, " List only retired tasks";
    ] in
  let move_spec =
    Arg.align [
    ] in
  let retire_spec =
    Arg.align [
    ] in
  let tag_spec =
    Arg.align [
      "--del", Arg.String add_tag_del, "tag Remove tag";
      "--delete", Arg.String add_tag_del, "tag Remove tag";
      "--remove", Arg.String add_tag_del, "tag Remove tag";
      "--rm", Arg.String add_tag_del, "tag Remove tag";
    ] in
  let tag_add_spec =
    Arg.align [
    ] in
  let tag_colour_spec =
    Arg.align [
    ] in
  let tag_del_spec =
    Arg.align [
    ] in
  let tag_list_spec =
    Arg.align [
    ] in
  let today_spec =
    Arg.align [
    ] in
  let todo_spec =
    Arg.align [
      "--estimate", Arg.Int set_todo_estimate, "days Estimated time taken";
    ] in

  (* This parses the global parameters before the subcommand. *)
  let global_spec =
    Arg.align [
      "--version", Arg.Unit print_version_and_exit, " Display version and exit";
    ] in
  let spec = ref global_spec in
  let subcommand = ref None in
  let anon_params = ref [] in
  let anon s =
    if !subcommand = None then (
      (* It's the subcommand, so switch the spec. *)
      let sc =
        try subcommand_of_string s
        with Invalid_argument _ ->
          raise (Arg.Bad "unknown subcommand") in
      subcommand := Some sc;
      match sc with
      | Idea -> spec := idea_spec
      | List -> spec := list_spec
      | Move -> spec := move_spec
      | Retire -> spec := retire_spec
      | Tag -> spec := tag_spec
      | Tag_add -> spec := tag_add_spec
      | Tag_colour -> spec := tag_colour_spec
      | Tag_del -> spec := tag_del_spec
      | Tag_list -> spec := tag_list_spec
      | Today -> spec := today_spec
      | Todo -> spec := todo_spec
    )
    else
      (* We've seen the subcommand already, just add it to anon_params. *)
      anon_params := s :: !anon_params
  in
  Arg.parse_dynamic spec anon usage;

  (* Return the parsed command line. *)
  let subcommand =
    match !subcommand with
    | None -> error "no subcommand given"
    | Some c -> c in
  let anon_params = List.rev !anon_params in

  let list_retired = !list_retired in
  let list_all = !list_all in
  let tag_del = List.rev !tag_del in
  let todo_estimate = !todo_estimate in

  subcommand, anon_params, list_retired, list_all, tag_del, todo_estimate