(* Utility functions. *)

open CalendarLib

open Printf

let rec find s sub =
  let len = String.length s in
  let sublen = String.length sub in
  let rec loop i =
    if i <= len-sublen then (
      let rec loop2 j =
        if j < sublen then (
          if s.[i+j] = sub.[j] then loop2 (j+1)
          else -1
        ) else
          i (* found *)
      in
      let r = loop2 0 in
      if r = -1 then loop (i+1) else r
    ) else
      -1 (* not found *)
  in
  loop 0

let rec nsplit sep str =
  let len = String.length str in
  let seplen = String.length sep in
  let i = find str sep in
  if i = -1 then [str]
  else (
    let s' = String.sub str 0 i in
    let s'' = String.sub str (i+seplen) (len-i-seplen) in
    s' :: nsplit sep s''
  )

let error fs =
  let display str =
    prerr_string "todo: error: ";
    prerr_endline str;
    exit 1
  in
  ksprintf display fs

let string_of_estimate period =
  (* We ignore the seconds, and assume every estimate is >= 1 day. *)
  let (years, months, days, _) = Calendar.Period.ymds period in
  let buf = Buffer.create 13 in
  let append str =
    if Buffer.length buf > 0 then
      Buffer.add_string buf ", ";
    Buffer.add_string buf str
  in
  if years >= 2 then append (sprintf "%d years" years)
  else if years = 1 then append "1 year";
  if months >= 2 then append (sprintf "%d months" months)
  else if months = 1 then append "1 month";
  if days >= 2 then append (sprintf "%d days" days)
  else if days = 1 then append "1 day";
  let str = Buffer.contents buf in
  if str <> "" then str else "-"