////////////////////////////////////////////////////////////////////////////////
//
// Copyright 2006 - 2021, Tomas Babej, Paul Beckingham, Federico Hernandez.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
// THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
//
// https://www.opensource.org/licenses/mit-license.php
//
////////////////////////////////////////////////////////////////////////////////

#include <cmake.h>
#include <iostream>
#include <iomanip>
#include <fstream>
#include <sstream>
#include <sys/types.h>
#include <inttypes.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <pwd.h>
#include <time.h>
#include <Context.h>
#include <Lexer.h>
#include <Datetime.h>
#include <Duration.h>
#include <format.h>
#include <unicode.h>
#include <util.h>
#include <main.h>

////////////////////////////////////////////////////////////////////////////////
// Scans all tasks, and for any recurring tasks, determines whether any new
// child tasks need to be generated to fill gaps.
void handleRecurrence ()
{
  // Recurrence can be disabled.
  // Note: This is currently a workaround for TD-44, TW-1520.
  if (! Context::getContext ().config.getBoolean ("recurrence"))
    return;

  auto tasks = Context::getContext ().tdb2.pending_tasks ();
  Datetime now;

  // Look at all tasks and find any recurring ones.
  for (auto& t : tasks)
  {
    if (t.getStatus () == Task::recurring)
    {
      // Generate a list of due dates for this recurring task, regardless of
      // the mask.
      std::vector <Datetime> due;
      if (! generateDueDates (t, due))
      {
        // Determine the end date.
        t.setStatus (Task::deleted);
        Context::getContext ().tdb2.modify (t);
        Context::getContext ().footnote (onExpiration (t));
        continue;
      }

      // Get the mask from the parent task.
      auto mask = t.get ("mask");

      // Iterate over the due dates, and check each against the mask.
      auto changed = false;
      unsigned int i = 0;
      for (auto& d : due)
      {
        if (mask.length () <= i)
        {
          changed = true;

          Task rec (t);                          // Clone the parent.
          rec.setStatus (Task::pending);         // Change the status.
          rec.set ("uuid", uuid ());             // New UUID.
          rec.set ("parent", t.get ("uuid"));    // Remember mom.
          rec.setAsNow ("entry");                // New entry date.
          rec.set ("due", format (d.toEpoch ()));

          if (t.has ("wait"))
          {
            Datetime old_wait (t.get_date ("wait"));
            Datetime old_due (t.get_date ("due"));
            Datetime due (d);
            rec.set ("wait", format ((due + (old_wait - old_due)).toEpoch ()));
            rec.setStatus (Task::waiting);
            mask += 'W';
          }
          else
          {
            mask += '-';
            rec.setStatus (Task::pending);
          }

          rec.set ("imask", i);
          rec.remove ("mask");                   // Remove the mask of the parent.

          // Add the new task to the DB.
          Context::getContext ().tdb2.add (rec);
        }

        ++i;
      }

      // Only modify the parent if necessary.
      if (changed)
      {
        t.set ("mask", mask);
        Context::getContext ().tdb2.modify (t);

        if (Context::getContext ().verbose ("recur"))
          Context::getContext ().footnote (format ("Creating recurring task instance '{1}'", t.get ("description")));
      }
    }
  }
}

////////////////////////////////////////////////////////////////////////////////
// Determine a start date (due), an optional end date (until), and an increment
// period (recur).  Then generate a set of corresponding dates.
//
// Returns false if the parent recurring task is depleted.
bool generateDueDates (Task& parent, std::vector <Datetime>& allDue)
{
  // Determine due date, recur period and until date.
  Datetime due (parent.get_date ("due"));
  if (due._date == 0)
    return false;

  std::string recur = parent.get ("recur");

  bool specificEnd = false;
  Datetime until;
  if (parent.get ("until") != "")
  {
    until = Datetime (parent.get ("until"));
    specificEnd = true;
  }

  auto recurrence_limit = Context::getContext ().config.getInteger ("recurrence.limit");
  int recurrence_counter = 0;
  Datetime now;
  for (Datetime i = due; ; i = getNextRecurrence (i, recur))
  {
    allDue.push_back (i);

    if (specificEnd && i > until)
    {
      // If i > until, it means there are no more tasks to generate, and if the
      // parent mask contains all + or X, then there never will be another task
      // to generate, and this parent task may be safely reaped.
      auto mask = parent.get ("mask");
      if (mask.length () == allDue.size () &&
          mask.find ('-') == std::string::npos)
        return false;

      return true;
    }

    if (i > now)
      ++recurrence_counter;

    if (recurrence_counter >= recurrence_limit)
      return true;
  }

  return true;
}

////////////////////////////////////////////////////////////////////////////////
Datetime getNextRecurrence (Datetime& current, std::string& period)
{
  auto m = current.month ();
  auto d = current.day ();
  auto y = current.year ();
  auto ho = current.hour ();
  auto mi = current.minute ();
  auto se = current.second ();

  // Some periods are difficult, because they can be vague.
  if (period == "monthly" ||
      period == "P1M")
  {
    if (++m > 12)
    {
       m -= 12;
       ++y;
    }

    while (! Datetime::valid (y, m, d))
      --d;

    return Datetime (y, m, d, ho, mi, se);
  }

  else if (period == "weekdays")
  {
    auto dow = current.dayOfWeek ();
    int days;

         if (dow == 5) days = 3;
    else if (dow == 6) days = 2;
    else               days = 1;

    return current + (days * 86400);
  }

  else if (unicodeLatinDigit (period[0]) &&
           period[period.length () - 1] == 'm')
  {
    int increment = strtol (period.substr (0, period.length () - 1).c_str (), nullptr, 10);

    if (increment <= 0)
      throw format ("Recurrence period '{1}' is equivalent to {2} and hence invalid.", period, increment);

    m += increment;
    while (m > 12)
    {
       m -= 12;
       ++y;
    }

    while (! Datetime::valid (y, m, d))
      --d;

    return Datetime (y, m, d, ho, mi, se);
  }

  else if (period[0] == 'P'                                            &&
           Lexer::isAllDigits (period.substr (1, period.length () - 2)) &&
           period[period.length () - 1] == 'M')
  {
    int increment = strtol (period.substr (1, period.length () - 2).c_str (), nullptr, 10);

    if (increment <= 0)
      throw format ("Recurrence period '{1}' is equivalent to {2} and hence invalid.", period, increment);

    m += increment;
    while (m > 12)
    {
       m -= 12;
       ++y;
    }

    while (! Datetime::valid (y, m, d))
      --d;

    return Datetime (y, m, d);
  }

  else if (period == "quarterly" ||
           period == "P3M")
  {
    m += 3;
    if (m > 12)
    {
       m -= 12;
       ++y;
    }

    while (! Datetime::valid (y, m, d))
      --d;

    return Datetime (y, m, d, ho, mi, se);
  }

  else if (unicodeLatinDigit (period[0]) && period[period.length () - 1] == 'q')
  {
    int increment = strtol (period.substr (0, period.length () - 1).c_str (), nullptr, 10);

    if (increment <= 0)
      throw format ("Recurrence period '{1}' is equivalent to {2} and hence invalid.", period, increment);

    m += 3 * increment;
    while (m > 12)
    {
       m -= 12;
       ++y;
    }

    while (! Datetime::valid (y, m, d))
      --d;

    return Datetime (y, m, d, ho, mi, se);
  }

  else if (period == "semiannual" ||
           period == "P6M")
  {
    m += 6;
    if (m > 12)
    {
       m -= 12;
       ++y;
    }

    while (! Datetime::valid (y, m, d))
      --d;

    return Datetime (y, m, d, ho, mi, se);
  }

  else if (period == "bimonthly" ||
           period == "P2M")
  {
    m += 2;
    if (m > 12)
    {
       m -= 12;
       ++y;
    }

    while (! Datetime::valid (y, m, d))
      --d;

    return Datetime (y, m, d, ho, mi, se);
  }

  else if (period == "biannual" ||
           period == "biyearly" ||
           period == "P2Y")
  {
    y += 2;

    return Datetime (y, m, d, ho, mi, se);
  }

  else if (period == "annual" ||
           period == "yearly" ||
           period == "P1Y")
  {
    y += 1;

    // If the due data just happens to be 2/29 in a leap year, then simply
    // incrementing y is going to create an invalid date.
    if (m == 2 && d == 29)
      d = 28;

    return Datetime (y, m, d, ho, mi, se);
  }

  // Add the period to current, and we're done.
  std::string::size_type idx = 0;
  Duration p;
  if (! p.parse (period, idx))
    throw std::string (format ("The recurrence value '{1}' is not valid.", period));

  return current + p.toTime_t ();
}

////////////////////////////////////////////////////////////////////////////////
// When the status of a recurring child task changes, the parent task must
// update it's mask.
void updateRecurrenceMask (Task& task)
{
  auto uuid = task.get ("parent");
  Task parent;

  if (uuid != "" &&
      Context::getContext ().tdb2.get (uuid, parent))
  {
    unsigned int index = strtol (task.get ("imask").c_str (), nullptr, 10);
    auto mask = parent.get ("mask");
    if (mask.length () > index)
    {
      mask[index] = (task.getStatus () == Task::pending)   ? '-'
                  : (task.getStatus () == Task::completed) ? '+'
                  : (task.getStatus () == Task::deleted)   ? 'X'
                  : (task.getStatus () == Task::waiting)   ? 'W'
                  :                                          '?';
    }
    else
    {
      std::string mask;
      for (unsigned int i = 0; i < index; ++i)
        mask += "?";

      mask += (task.getStatus () == Task::pending)   ? '-'
            : (task.getStatus () == Task::completed) ? '+'
            : (task.getStatus () == Task::deleted)   ? 'X'
            : (task.getStatus () == Task::waiting)   ? 'W'
            :                                          '?';
    }

    parent.set ("mask", mask);
    Context::getContext ().tdb2.modify (parent);
  }
}

////////////////////////////////////////////////////////////////////////////////
// Delete expired tasks.
void handleUntil ()
{
  Datetime now;
  auto tasks = Context::getContext ().tdb2.pending_tasks ();
  for (auto& t : tasks)
  {
    // TODO What about expiring template tasks?
    if (t.getStatus () == Task::pending &&
        t.has ("until"))
    {
      auto until = Datetime (t.get_date ("until"));
      if (until < now)
      {
        Context::getContext ().debug (format ("handleUntil: recurrence expired until {1} < now {2}", until.toISOLocalExtended (), now.toISOLocalExtended ()));
        t.setStatus (Task::deleted);
        Context::getContext ().tdb2.modify(t);
        Context::getContext ().footnote (onExpiration (t));
      }
    }
  }
}

////////////////////////////////////////////////////////////////////////////////