rem: implement basic event → reminder formatter

2 files changed, 346 insertions, 0 deletions

diff --git a/common.lua b/common.lua
index fe29d8c..c009207 100644
--- a/common.lua
+++ b/common.lua
@@ -1,3 +1,5 @@
+local string        = require "string"
+local stringformat  = string.format
 
 local verboselvl    = 0
 
diff --git a/rem.lua b/rem.lua
new file mode 100644
index 0000000..e1fdc1f
--- /dev/null
+++ b/rem.lua
@@ -0,0 +1,344 @@
+--[[--
+
+    remind(1) compatible formatting.
+
+--]]--
+
+local inspect = require "ext.inspect"
+
+local pcall         = pcall
+
+local io            = require "io"
+local iostdout      = io.stdout
+
+local math          = require "math"
+local mathfloor     = math.floor
+
+local os            = os
+local osdate        = os.date
+local ostime        = os.time
+
+local string        = require "string"
+local stringformat  = string.format
+local stringsub     = string.sub
+
+local table         = require "table"
+local tableconcat   = table.concat
+
+local common        = require "common"
+local println       = common.println
+local errorln       = common.errorln
+local noiseln       = common.noiseln
+local debugln       = common.debugln
+
+local seconds_of_time = function (t)
+  return t % 60
+end
+
+local minutes_of_time = function (t)
+  return mathfloor (t / 60) % 60
+end
+
+local hours_of_time = function (t)
+  return mathfloor (t / (60 * 60)) % 60
+end
+
+local days_of_time = function (t)
+  return mathfloor (t / (24 * 60 * 60))
+end
+
+local get_param = function (params, name)
+  local np = #params
+
+  for i = 1, np do
+    local param = params [i]
+    if param.name == name then return param end
+  end
+
+  return nil
+end
+
+local get_param_value = function (params, name)
+  local param = get_param (params, name)
+
+  if param ~= nil then return param.value end
+
+  return nil
+end
+
+local get_param_value_1 = function (params, name)
+  local val = get_param_value (params, name)
+
+  if val ~= nil then
+    return val [1]
+  end
+
+  return nil
+end
+
+local rem_of_vcalendars do
+
+  local f_sec    = 1
+  local f_min    = 60 * f_sec
+  local f_hour   = 60 * f_min
+  local f_day    = 24 * f_hour
+  local l_month  = { [00] =  0
+                   , [01] = 31
+                   , [02] = 30
+                   , [03] = 31
+                   , [04] = 30
+                   , [05] = 31
+                   , [06] = 30
+                   , [07] = 31
+                   , [08] = 31
+                   , [09] = 30
+                   , [10] = 31
+                   , [11] = 30
+                   , [12] = 31
+                   }
+
+  local time_of_month = function (m, y)
+    local r = 0
+
+    for i = 0, m - 1 do
+      local f = l_month [i] 
+
+      if i == 2 and y % 4 == 0 and y % 100 ~= 0 then
+        f = f + 1
+      end
+
+      r = r + f * f_day
+    end
+
+    return r
+  end
+
+  local time_of_year = function (y)
+    if y % 4 == 0 and y % 100 ~= 0 then
+    end
+  end
+
+  --[[--
+
+     Date format “%Y%M%D”
+
+  --]]--
+
+  local parse_date_value_DATE = function (st, tzid)
+    local Y = tonumber (stringsub (st, 1, 4))
+    local M = tonumber (stringsub (st, 5, 6))
+    local D = tonumber (stringsub (st, 7, 8))
+
+    return ostime { year = Y, month = M, day = D }
+  end
+
+  --[[--
+
+      Date format 1 date with local time: “%Y%M%DT%h%m%s”
+      Date format 2 date with local time: “%Y%M%DT%h%m%sZ%z”
+      Date format 3 date with local time: “%Y%M%DT%h%m%s” with TZID parm
+
+  --]]--
+  local parse_date_value_DATE_TIME = function (st, tzid)
+    if #st < 15 then
+      error (stringformat ("date-time specification [%s] is rubbish", st))
+    end
+
+    local Y = tonumber (stringsub (st, 1, 4))
+    local M = tonumber (stringsub (st, 5, 6))
+    local D = tonumber (stringsub (st, 7, 8))
+    assert (stringsub (st, 9, 9) == "T")
+    local h = tonumber (stringsub (st, 10, 11))
+    local m = tonumber (stringsub (st, 12, 13))
+    local s = tonumber (stringsub (st, 14, 15))
+
+    local t = { year  = Y
+              , month = M
+              , day   = D
+              , hour  = h
+              , min   = m
+              , sec   = s
+              , isdst = false
+              }
+
+    if #st == 15 then
+      --- format 3 (with time zone reference)
+      if tzid then
+        error (stringformat ("timezone specification (TZID) for dates \z
+                              not implemented, sorry"))
+      end
+
+      --- format 1 (local)
+      return ostime (t), true
+    end
+
+    --- format 2 (UTC)
+    assert (stringsub (st, 16, 16) == "Z",
+            stringformat ("rubbish date-time specification %s", st))
+
+    return ostime (t), false
+  end
+
+  --[[--
+
+    if params lack a VALUE entry, DATE-TIME is assumed
+  --]]--
+
+  local parse_date_value = function (val)
+    local params = val.params
+
+    local ptzid = get_param_value_1 (params, "TZID") 
+    local pdate = get_param_value_1 (params, "VALUE") 
+
+    if pdate == nil or pdate == "DATE-TIME" then
+      return parse_date_value_DATE_TIME (val.value, ptzid)
+    end
+
+    if pdate == "DATE" then
+      return parse_date_value_DATE (val.value, ptzid), false
+    end
+
+    return nil
+  end
+
+  local rem_date = function (d, loctime)
+    if loctime == true then
+      return osdate ("%b %d %Y AT %H:%M", d)
+    end
+
+    return osdate ("!%b %d %Y AT %H:%M", d)
+  end
+
+  local rem_duration = function (dt)
+    --[[-- remind(1): Note that duration is specified in hours and minutes. --]]--
+
+    local s
+    local ret = ""
+
+    s = dt % 60
+    ret = ret .. stringformat ("%0.2d", s)
+
+    dt = mathfloor (dt / 60)
+    if dt == 0 then return ret end
+
+    return stringformat ("%0.2d:%s", dt, ret)
+  end
+
+  local rem_date_duration = function (t0, te, loctime)
+    local dt = te - t0
+    local s_t0 = rem_date (t0, loctime)
+    local s_dt = rem_duration (dt)
+
+    return stringformat ("%s DURATION %s", s_t0, s_dt)
+  end
+
+  local date_of_interval = function (dtstart, dtend)
+    local t0, loctime = parse_date_value (dtstart)
+    local te, _ignore = parse_date_value (dtend)
+
+    if t0 ~= nil then
+      if te ~= nil then return rem_date_duration (t0, te, loctime) end
+      return rem_date (t0, loctime)
+    end
+
+    return nil
+  end
+
+  local msg_of_description = function (val)
+    return val.value
+  end
+
+  local rem_of_vevent = function (ev)
+    local dtstart, dtend
+    local date, msg
+    local vals  = ev.value
+    local nvals = #vals
+
+    for i = 1, nvals do
+      local val = vals [i]
+
+      if val.kind == "other" then
+        local valname = val.name
+
+        if     valname == "description" then msg = msg_of_description (val)
+        elseif valname == "dtstart"     then dtstart = val
+        elseif valname == "dtend"       then dtend = val
+        else
+          noiseln ("rem_of_vevent: ignoring value [%s]", valname)
+        end
+      else
+      end
+    end
+
+    date = date_of_interval (dtstart, dtend)
+
+    if date == nil then
+      error ("could not derive date from event values")
+    end
+
+    if msg == nil then
+      error ("could not derive message text from event values")
+    end
+
+    return stringformat ("REM %s MSG %s", date, msg)
+  end
+
+  local rem_of_vcalendar = function (vcal)
+    local acc   = { }
+    local vals  = vcal.value
+    local nvals = #vals
+
+    for i = 1, nvals do
+      local val = vals [i]
+
+      if val.kind ~= "scope" or val.name ~= "VEVENT" then
+        noiseln ("rem_of_vcalendar: ignoring value %d of type [%s/%s]",
+                 i, val.kind, val.name)
+      else
+        local ok, res = pcall (rem_of_vevent, val)
+        if ok then
+          acc [#acc + 1] = res
+        else
+          errorln ("rem_of_vcalendar: vevent %d contains invalid entry: %s",
+                   i, tostring (res))
+        end
+      end
+    end
+
+    return tableconcat (acc, "\n")
+  end
+
+  rem_of_vcalendars = function (vcals)
+    local value = vcals.value
+    local nvcal = #value
+    local acc = { }
+
+    for i = 1, nvcal do
+      local vcal = value [i]
+      if vcal.kind ~= "scope" or vcal.name ~= "VCALENDAR" then
+        noiseln ("rem_of_vcalendars: ignoring object %d of type [%s/%s]",
+                 i, vcal.kind, vcal.name)
+      else
+        acc [#acc + 1] = rem_of_vcalendar (vcal)
+      end
+    end
+
+    return tableconcat (acc, "\n")
+  end
+end --- [rem_of_vcalendars]
+
+-------------------------------------------------------------------------------
+--- API
+-------------------------------------------------------------------------------
+
+local output_calendar = function (cal, fh)
+  fh = fh or iostdout
+  local ok, str = pcall (rem_of_vcalendars, cal)
+  if ok then
+    fh:write (str)
+  end
+end
+
+return { output_calendar = output_calendar
+       }
+