/*
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.UserModel
	decisions         *models.MotionModel
	notifier          *MailNotifier
}

func (r *RemindVotersJob) Schedule() {
	// TODO: check logic. It would make more sense to remind at a specific interval before the next pending
	//  decision is closed
	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.Schedule() }(r)

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

	ctx := context.Background()

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

		return
	}

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

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

			return
		}

		if len(decisions) > 0 {
			r.notifier.Notify(&RemindVoterNotification{voter: voter, decisions: decisions})
		}
	}
}

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

		r.timer = nil
	}
}

func (app *application) NewRemindVotersJob() Job {
	return &RemindVotersJob{
		infoLog:   app.infoLog,
		errorLog:  app.errorLog,
		voters:    app.users,
		decisions: app.motions,
		notifier:  app.mailNotifier,
	}
}

type CloseDecisionsJob struct {
	timer     *time.Timer
	infoLog   *log.Logger
	errorLog  *log.Logger
	decisions *models.MotionModel
	notifier  *MailNotifier
}

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

	ctx := context.Background()

	nextDue, err = c.decisions.NextPendingDue(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")

	defer func(c *CloseDecisionsJob) { c.Schedule() }(c)

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

	for _, res := range results {
		c.infoLog.Printf(
			"decision %s closed with result %s: reasoning '%s'",
			res.Tag,
			res.Status,
			res.Reasoning,
		)

		c.notifier.Notify(&ClosedDecisionNotification{Decision: res})
	}
}

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

func (app *application) NewCloseDecisionsJob() Job {
	return &CloseDecisionsJob{
		infoLog:   app.infoLog,
		errorLog:  app.errorLog,
		decisions: app.motions,
		notifier:  app.mailNotifier,
	}
}

type JobIdentifier int

const (
	JobIDCloseDecisions JobIdentifier = iota
	JobIDRemindVoters
)

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

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

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

	app.jobScheduler.addJob(JobIDCloseDecisions, app.NewCloseDecisionsJob())
	app.jobScheduler.addJob(JobIDRemindVoters, app.NewRemindVotersJob())
}

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

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

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

			return
		}
	}
}

func (js *JobScheduler) addJob(jobID JobIdentifier, job Job) {
	js.jobs[jobID] = job
}

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

func (js *JobScheduler) Reschedule(jobIDs ...JobIdentifier) {
	for i := range jobIDs {
		js.rescheduleChannel <- jobIDs[i]
	}
}