feat: initial implementation of iCalendar to Remind converter

- Add project scaffolding (dune, dune-project, opam, .ocamlformat)
- Implement basic parsing and handling of iCalendar events
- Add event predicates for common event types (all-day, timed,
  recurrence, exceptions)
- Add transformation logic to map iCalendar events to Remind format
  (stub implementation)
- Provide utilities for extracting event details and converting
  dates/times
- Set up executable entrypoint and command-line interface using Cmdliner
- Include Remind event type definitions and helpers

.ocamlformat

@@ -0,0 +1,19 @@
+version = 0.28.1
+profile = conventional
+
+break-cases = fit-or-vertical
+break-infix = fit-or-vertical
+break-separators = after
+cases-exp-indent = 2
+exp-grouping = preserve
+if-then-else = keyword-first
+leading-nested-match-parens = false
+let-and = sparse
+margin = 120
+space-around-arrays = false
+space-around-lists = false
+space-around-records = false
+space-around-records = true
+space-around-variants = false
+type-decl = sparse
+wrap-fun-args = false

bin/commandLine.ml

@@ -0,0 +1,17 @@
+open Cmdliner
+open Cmdliner.Term.Syntax
+
+let ical_file =
+  let doc = "TODO" in
+  let docv = "ICAL" in
+  Arg.(required & pos ~rev:true 0 (some string) None & info [] ~docv ~doc)
+
+let main_command f =
+  let doc = "Convert iCalendar files to remind format" in
+  let man = [] in
+  Cmd.make (Cmd.info "ical2rem" ~version:"%%VERSION%%" ~doc ~man)
+  @@
+  let+ ical_file = ical_file in
+  f ical_file
+
+let main f = Cmd.eval @@ main_command f

bin/dune

@@ -0,0 +1,13 @@
+(executable
+ (public_name remind_sync)
+ (name main)
+ (modules main commandLine remind eventTransformer eventPredicates utils)
+ (preprocess
+  (pps ppx_deriving.show))
+ (libraries
+  ;remind_sync
+  cmdliner
+  icalendar
+  timedesc-tzdb.full
+  timedesc-tzlocal.unix
+  timedesc))

bin/eventTransformer.ml

@@ -0,0 +1,15 @@
+let default_implementation = Remind.Omit (Ptime.epoch |> Ptime.to_date)
+
+let remind_of_event (ev : Icalendar.event) : Remind.event =
+  let found =
+    ListLabels.fold_left ~init:[] EventPredicates.all_predicates ~f:(fun acc (pred, desc) ->
+        if pred ev then desc :: acc else acc)
+    |> List.rev
+  in
+  if List.length found > 0
+  then begin
+    Printf.printf "  󰧓 ⇒ matches these predicates:\n";
+    List.iter (fun d -> Printf.printf "    - %s\n" (EventPredicates.show_event_description d)) found;
+    Printf.printf "\n"
+  end;
+  default_implementation

bin/main.ml

@@ -0,0 +1,34 @@
+let ical2rem ical_file =
+  let ic = open_in ical_file in
+  let n = in_channel_length ic in
+  let s = Bytes.create n in
+  really_input ic s 0 n;
+  close_in ic;
+  let cal_or_error = Icalendar.parse (Bytes.unsafe_to_string s) in
+  match cal_or_error with
+  | Error e -> prerr_endline ("Error parsing iCalendar file: " ^ e)
+  | Ok (_, components) -> begin
+    let events = ref 0 in
+    List.iter
+      (fun comp ->
+        match comp with
+        | `Event event ->
+          events := !events + 1;
+          let uid = Utils.get_uid event in
+          Printf.printf "󰧓 ⇒ UID: %s\n" uid;
+          Printf.printf "%s\n\n\n" (Icalendar.show_component comp)
+        | _ -> () (* Ignore non-event components *))
+      components;
+    Printf.printf "\nEvents: %d\n" !events;
+    let events =
+      List.filter_map
+        (function
+          | `Event ev -> Some ev
+          | _ -> None)
+        components
+    in
+    let _reminders = List.map EventTransformer.remind_of_event events in
+    ()
+  end
+
+let () = if !Sys.interactive then () else exit (CommandLine.main ical2rem)

bin/remind.ml

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+(* Alias esplicito per chiarezza *)
+type date = Ptime.date
+
+let pp_date fmt (y, m, d) = Format.fprintf fmt "%04d-%02d-%02d" y m d
+
+let show_date (d : date) : string =
+  let y, m, day = d in
+  Printf.sprintf "%04d-%02d-%02d" y m day
+
+type tod = Ptime.Span.t (* secondi da mezzanotte locale *)
+
+let pp_tod = Ptime.Span.pp
+let span_min (m : int) : tod = Ptime.Span.of_int_s (m * 60)
+let span_hm ~(h : int) ~(m : int) : tod = Ptime.Span.of_int_s ((h * 3600) + (m * 60))
+
+let hm_of_tod (t : tod) : int * int =
+  match Ptime.Span.to_int_s t with
+  | None -> invalid_arg "tod out of range"
+  | Some s -> (s / 3600, s mod 3600 / 60)
+
+type weekday =
+  | Mon
+  | Tue
+  | Wed
+  | Thu
+  | Fri
+  | Sat
+  | Sun
+
+type time_spec =
+  | All_day
+  | Timed of {
+      at : tod;
+      duration : Ptime.Span.t option;
+    }
+
+type range = {
+  from_ : date;
+  until : date option;
+}
+(* UNTIL inclusivo *)
+
+type recurrence =
+  | No_recur
+  | Daily of {
+      interval : int;
+      span : range;
+    }
+  | Weekly of {
+      interval : int;
+      days : weekday list;
+      span : range;
+    }
+  | Monthly_dom of {
+      interval : int;
+      day : int;
+      span : range;
+    }
+  | Monthly_nth_weekday of {
+      interval : int;
+      n : int;
+      wday : weekday;
+      span : range;
+    }
+  | Yearly of {
+      month : int;
+      day : int;
+    }
+
+type alarm = { warn_before : Ptime.Span.t }
+
+type meta = {
+  location : string option;
+  url : string option;
+  categories : string list;
+  attendees : string list;
+}
+
+type instance_override = {
+  on : date;
+  cancel : bool;
+  summary : string option;
+  time_spec : time_spec option;
+  notes : string option;
+  alarm : alarm option;
+  meta : meta option;
+}
+
+type series = {
+  summary : string;
+  start : date; (* DTSTART locale *)
+  time_spec : time_spec;
+  recur : recurrence;
+  exdates : date list;
+  overrides : instance_override list;
+  alarm : alarm option;
+  notes : string option;
+  meta : meta;
+}
+
+type info_header = string [@@deriving show]
+type info_value = string [@@deriving show]
+
+type event =
+  | Rem of {
+      date_expr : string;
+      at : tod option;
+      duration : Ptime.Span.t option;
+      warn : Ptime.Span.t option;
+      msg : string;
+      exdates : date list;
+      infos : (info_header * info_value) list;
+    }
+  | Omit of date
+[@@deriving show]
+
+let string_of_date (d : date) : string =
+  let y, m, day = d in
+  Printf.sprintf "%04d-%02d-%02d" y m day

bin/utils.ml

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+open Icalendar
+
+let get_uid ev =
+  let _, uid = ev.uid in
+  uid
+
+let timedesc_of_date_or_datetime (t : date_or_datetime) : Timedesc.t =
+  match t with
+  | `Datetime (`Local _ptime_ts) ->
+    (* TODO: 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_start ev =
+  let _, start = ev.dtstart in
+  timedesc_of_date_or_datetime start
+
+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 _ ->
+          (* TODO: 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

dune

@@ -0,0 +1 @@
+(data_only_dirs contrib)

dune-project

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+(lang dune 3.20)
+
+(name remind_sync)
+
+(generate_opam_files true)
+
+(source
+ (uri https://git.donadeo.net/pdonadeo/remind-sync))
+
+(authors "Paolo Donadeo <paolo@donadeo.net>")
+
+(maintainers "Maintainer Name <maintainer@example.com>")
+
+(license MIT)
+
+(documentation https://git.donadeo.net/pdonadeo/remind-sync)
+
+(package
+ (name remind_sync)
+ (synopsis "A short synopsis")
+ (description "A longer description")
+ (depends ocaml)
+ (tags
+  ("add topics" "to describe" your project)))

lib/dune

@@ -0,0 +1,2 @@
+(library
+ (name remind_sync))

remind_sync.opam

@@ -0,0 +1,30 @@
+# This file is generated by dune, edit dune-project instead
+opam-version: "2.0"
+synopsis: "A short synopsis"
+description: "A longer description"
+maintainer: ["Maintainer Name <maintainer@example.com>"]
+authors: ["Paolo Donadeo <paolo@donadeo.net>"]
+license: "MIT"
+tags: ["add topics" "to describe" "your" "project"]
+doc: "https://git.donadeo.net/pdonadeo/remind-sync"
+depends: [
+  "dune" {>= "3.20"}
+  "ocaml"
+  "odoc" {with-doc}
+]
+build: [
+  ["dune" "subst"] {dev}
+  [
+    "dune"
+    "build"
+    "-p"
+    name
+    "-j"
+    jobs
+    "@install"
+    "@runtest" {with-test}
+    "@doc" {with-doc}
+  ]
+]
+dev-repo: "https://git.donadeo.net/pdonadeo/remind-sync"
+x-maintenance-intent: ["(latest)"]