/*
Copyright 2017-2022 CAcert Inc.
SPDX-License-Identifier: Apache-2.0

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package main

import (
	"context"
	"log"
	"time"

	"git.cacert.org/cacert-boardvoting/internal/models"
)

type Job interface {
	Schedule()
	Run()
	Stop()
}

type RemindVotersJob struct {
	infoLog, errorLog *log.Logger
	timer             *time.Timer
	voters            *models.VoterModel
	decisions         *models.MotionModel
	notify            chan NotificationMail
	reschedule        chan Job
}

func (r *RemindVotersJob) Schedule() {
	const reminderDays = 3

	year, month, day := time.Now().UTC().Date()

	nextExecution := time.Date(
		year, month, day, 0, 0, 0, 0, time.UTC,
	).AddDate(0, 0, reminderDays)

	r.infoLog.Printf("scheduling RemindVotersJob for %s", nextExecution)

	when := time.Until(nextExecution)

	if r.timer != nil {
		r.timer.Reset(when)

		return
	}

	r.timer = time.AfterFunc(when, r.Run)
}

func (r *RemindVotersJob) Run() {
	r.infoLog.Print("running RemindVotersJob")

	defer func(r *RemindVotersJob) { r.reschedule <- r }(r)

	var (
		voters    []*models.Voter
		decisions []*models.Motion
		err       error
	)

	ctx := context.Background()

	voters, err = r.voters.GetReminderVoters(ctx)
	if err != nil {
		r.errorLog.Printf("problem getting voters: %v", err)

		return
	}

	for _, voter := range voters {
		v := voter

		decisions, err = r.decisions.UnVotedDecisionsForVoter(ctx, v)
		if err != nil {
			r.errorLog.Printf("problem getting unvoted decisions: %v", err)

			return
		}

		if len(decisions) > 0 {
			r.notify <- &RemindVoterNotification{voter: voter, decisions: decisions}
		}
	}
}

func (r *RemindVotersJob) Stop() {
	if r.timer != nil {
		r.timer.Stop()

		r.timer = nil
	}
}

func (app *application) NewRemindVotersJob(
	rescheduleChannel chan Job,
) Job {
	return &RemindVotersJob{
		infoLog:    app.infoLog,
		errorLog:   app.errorLog,
		voters:     app.voters,
		decisions:  app.motions,
		reschedule: rescheduleChannel,
		notify:     app.mailNotifier.notifyChannel,
	}
}

type CloseDecisionsJob struct {
	timer      *time.Timer
	infoLog    *log.Logger
	errorLog   *log.Logger
	decisions  *models.MotionModel
	reschedule chan Job
	notify     chan NotificationMail
}

func (c *CloseDecisionsJob) Schedule() {
	var (
		nextDue *time.Time
		err     error
	)

	ctx := context.Background()

	nextDue, err = c.decisions.NextPendingDecisionDue(ctx)
	if err != nil {
		c.errorLog.Printf("could not get next pending due date")

		c.Stop()

		return
	}

	if nextDue == nil {
		c.infoLog.Printf("no next planned execution of CloseDecisionsJob")
		c.Stop()

		return
	}

	c.infoLog.Printf("scheduling CloseDecisionsJob for %s", nextDue)
	when := time.Until(nextDue.Add(time.Second))

	if c.timer == nil {
		c.timer = time.AfterFunc(when, c.Run)

		return
	}

	c.timer.Reset(when)
}

func (c *CloseDecisionsJob) Run() {
	c.infoLog.Printf("running CloseDecisionsJob")

	results, err := c.decisions.CloseDecisions(context.Background())
	if err != nil {
		c.errorLog.Printf("closing decisions failed: %v", err)
	}

	for _, res := range results {
		c.notify <- &ClosedDecisionNotification{decision: res}
	}

	c.reschedule <- c
}

func (c *CloseDecisionsJob) Stop() {
	if c.timer != nil {
		c.timer.Stop()
		c.timer = nil
	}
}

func (app *application) NewCloseDecisionsJob(
	rescheduleChannel chan Job,
) Job {
	return &CloseDecisionsJob{
		infoLog:    app.infoLog,
		errorLog:   app.errorLog,
		decisions:  app.motions,
		reschedule: rescheduleChannel,
		notify:     app.mailNotifier.notifyChannel,
	}
}

type JobScheduler struct {
	infoLogger        *log.Logger
	errorLogger       *log.Logger
	jobs              []Job
	rescheduleChannel chan Job
	quitChannel       chan struct{}
}

func (app *application) NewJobScheduler() {
	rescheduleChannel := make(chan Job, 1)

	app.jobScheduler = &JobScheduler{
		infoLogger:        app.infoLog,
		errorLogger:       app.errorLog,
		jobs:              make([]Job, 0, 2),
		rescheduleChannel: rescheduleChannel,
		quitChannel:       make(chan struct{}),
	}

	app.jobScheduler.addJob(app.NewCloseDecisionsJob(rescheduleChannel))
	app.jobScheduler.addJob(app.NewRemindVotersJob(rescheduleChannel))
}

func (js *JobScheduler) Schedule() {
	for _, job := range js.jobs {
		job.Schedule()
	}

	for {
		select {
		case job := <-js.rescheduleChannel:
			job.Schedule()
		case <-js.quitChannel:
			for _, job := range js.jobs {
				job.Stop()
			}

			js.infoLogger.Print("stop job scheduler")

			return
		}
	}
}

func (js *JobScheduler) addJob(job Job) {
	js.jobs = append(js.jobs, job)
}

func (js *JobScheduler) Quit() {
	js.quitChannel <- struct{}{}
}