open Remind_sync
open Icalendar

type months = Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec

let month_of_int = function
  | 1 -> Jan
  | 2 -> Feb
  | 3 -> Mar
  | 4 -> Apr
  | 5 -> May
  | 6 -> Jun
  | 7 -> Jul
  | 8 -> Aug
  | 9 -> Sep
  | 10 -> Oct
  | 11 -> Nov
  | 12 -> Dec
  | _ -> failwith "Invalid month number"

let string_of_month = function
  | Jan -> "Jan"
  | Feb -> "Feb"
  | Mar -> "Mar"
  | Apr -> "Apr"
  | May -> "May"
  | Jun -> "Jun"
  | Jul -> "Jul"
  | Aug -> "Aug"
  | Sep -> "Sep"
  | Oct -> "Oct"
  | Nov -> "Nov"
  | Dec -> "Dec"

let spf = Printf.sprintf

let get_uid ev =
  let _, uid = ev.uid in
  uid

(* Questa funzione serve solo da esempio per copia e incolla *)
let unpack_date_or_datetime (d_or_dt : Icalendar.date_or_datetime) =
  match d_or_dt with
  | `Datetime (`Local _ptime_ts) -> ()
  | `Datetime (`Utc _ts) -> ()
  | `Datetime (`With_tzid (_ts, (_b, _tz_name))) -> ()
  | `Date (_year, _month, _day) -> ()

(* Questa funzione serve solo da esempio per copia e incolla *)
let unpack_dtend_or_duration dtend_or_dur =
  match dtend_or_dur with
  | None -> ()
  | Some (`Dtend (_, date_or_datetime)) -> unpack_date_or_datetime date_or_datetime
  | Some (`Duration (_, _duration)) -> ()

let string_of_time (t : Timedesc.Time.t) : string =
  let view = Timedesc.Time.view t in
  let hour, minute = (view.Timedesc.Time.hour, view.Timedesc.Time.minute) in
  spf "%02d:%02d" hour minute

let string_of_span (sp : Timedesc.Span.t) : string =
  let view = Timedesc.Span.For_human.view sp in
  let hours, minutes = (view.Timedesc.Span.For_human.hours, view.Timedesc.Span.For_human.minutes) in
  spf "%02d:%02d" hours minutes

let timedesc_of_timestamp (ts : timestamp) : Timedesc.t =
  let local_tz = Timedesc.Time_zone.local_exn () in
  match ts with
  | `Local t -> t |> Timedesc.Utils.timestamp_of_ptime |> Timedesc.of_timestamp_exn ~tz_of_date_time:local_tz
  (* this case is not present in my current dataset… *)
  | `Utc t -> t |> Timedesc.Utils.timestamp_of_ptime |> Timedesc.of_timestamp_exn ~tz_of_date_time:local_tz
  | `With_tzid (ts, (_b, tz_name)) ->
      (* Qui il timestamp è SCRITTO come se fosse UTC (+00:00) ma in realtà va interpretato con
       il fuso orario indicato da tz_name. *)
      let tz = Timedesc.Time_zone.make_exn tz_name in
      let wrong_ts = Timedesc.Utils.timestamp_of_ptime ts in
      let date = Timedesc.date (Timedesc.of_timestamp_exn ~tz_of_date_time:Timedesc.Time_zone.utc wrong_ts) in
      let year, month, day = (Timedesc.Date.year date, Timedesc.Date.month date, Timedesc.Date.day date) in
      let time = Timedesc.time_view (Timedesc.of_timestamp_exn ~tz_of_date_time:Timedesc.Time_zone.utc wrong_ts) in
      let hour, minute, second = (time.Timedesc.Time.hour, time.Timedesc.Time.minute, time.Timedesc.Time.second) in
      Timedesc.make_exn ~year ~month ~day ~hour ~minute ~second ~tz ()

let timedesc_of_date_or_datetime (t : date_or_datetime) : Timedesc.t =
  match t with
  | `Datetime (`Local _ptime_ts) ->
      (* this case is not present in my current dataset… *)
      failwith "Unhandled case: `Local datetime"
  | `Datetime (`Utc ts) ->
      Timedesc.Utils.timestamp_of_ptime ts
      |> Timedesc.of_timestamp_exn ~tz_of_date_time:(Timedesc.Time_zone.local_exn ())
  | `Datetime (`With_tzid (ts, (_b, tz_name))) ->
      (* Qui il timestamp è SCRITTO come se fosse UTC (+00:00) ma in realtà va interpretato con
       il fuso orario indicato da tz_name. *)
      let tz = Timedesc.Time_zone.make_exn tz_name in
      let wrong_ts = Timedesc.Utils.timestamp_of_ptime ts in
      let date = Timedesc.date (Timedesc.of_timestamp_exn ~tz_of_date_time:Timedesc.Time_zone.utc wrong_ts) in
      let year, month, day = (Timedesc.Date.year date, Timedesc.Date.month date, Timedesc.Date.day date) in
      let time = Timedesc.time_view (Timedesc.of_timestamp_exn ~tz_of_date_time:Timedesc.Time_zone.utc wrong_ts) in
      let hour, minute, second = (time.Timedesc.Time.hour, time.Timedesc.Time.minute, time.Timedesc.Time.second) in
      Timedesc.make_exn ~year ~month ~day ~hour ~minute ~second ~tz ()
  | `Date (year, month, day) ->
      Timedesc.make_exn ~year ~month ~day ~hour:0 ~minute:0 ~second:0 ~tz:(Timedesc.Time_zone.local_exn ()) ()

let get_exdates ev =
  let event_props = ev.props in
  let dates_or_datetimes =
    List.filter_map
      (fun prop ->
        match prop with
        | `Exdate (_, dates) -> Some dates
        | _ -> None)
      event_props
  in
  ListLabels.fold_left ~init:[] dates_or_datetimes ~f:(fun acc dates ->
      let added =
        match dates with
        | `Datetimes ts_list -> List.map (fun ts -> `Datetime ts) ts_list
        | `Dates date_list -> List.map (fun date -> `Date date) date_list
      in
      added @ acc)
  |> List.map timedesc_of_date_or_datetime

let get_rdates ev =
  let event_props = ev.props in
  let dates_or_datetimes =
    List.filter_map
      (fun prop ->
        match prop with
        | `Rdate (_, dates) -> Some dates
        | _ -> None)
      event_props
  in
  ListLabels.fold_left ~init:[] dates_or_datetimes ~f:(fun acc dates ->
      let added =
        match dates with
        | `Datetimes ts_list -> List.map (fun ts -> `Datetime ts) ts_list
        | `Dates date_list -> List.map (fun date -> `Date date) date_list
        | `Periods _ ->
            (* Ignored for now, does not appear in my current dataset *)
            failwith "Unhandled case: `Periods in RDATE"
      in
      added @ acc)
  |> List.map timedesc_of_date_or_datetime

let get_recurrence_id ev =
  List.find_map
    (fun prop ->
      match prop with
      | `Recur_id (_, date_or_datetime) -> Some date_or_datetime
      | _ -> None)
    ev.props

let separate_master_and_recurrence (events : Icalendar.event list) : Icalendar.event * Icalendar.event list =
  (* List.iteri (fun i e -> Printf.eprintf "%02d: %s\n" (i + 1) (Icalendar.show_component (`Event e))) events; *)
  let recur_ids = List.map (fun ev -> (ev, get_recurrence_id ev)) events in

  let master_and_recurrences =
    List.partition_map
      (fun (ev, recur_id_opt) ->
        match recur_id_opt with
        | None -> Right ev
        | Some _ -> Left ev)
      recur_ids
  in
  match master_and_recurrences with
  | [], _ -> failwith "No master event found"
  | master :: _, recurrences -> (master, recurrences)