// Copyright 2019 Drone.IO Inc. All rights reserved.
// Use of this source code is governed by the Drone Non-Commercial License
// that can be found in the LICENSE file.

package cron

import (
	"context"
	"fmt"
	"time"

	"github.com/drone/drone/core"

	"github.com/hashicorp/go-multierror"
	"github.com/robfig/cron"
	"github.com/sirupsen/logrus"
)

// New returns a new Cron scheduler.
func New(
	commits core.CommitService,
	cron core.CronStore,
	repos core.RepositoryStore,
	users core.UserStore,
	trigger core.Triggerer,
) *Scheduler {
	return &Scheduler{
		commits: commits,
		cron:    cron,
		repos:   repos,
		users:   users,
		trigger: trigger,
	}
}

// Scheduler defines a cron scheduler.
type Scheduler struct {
	commits core.CommitService
	cron    core.CronStore
	repos   core.RepositoryStore
	users   core.UserStore
	trigger core.Triggerer
}

// Start starts the cron scheduler.
func (s *Scheduler) Start(ctx context.Context, dur time.Duration) error {
	for {
		select {
		case <-ctx.Done():
			return ctx.Err()
		case <-time.After(dur):
			s.run(ctx)
		}
	}
}

func (s *Scheduler) run(ctx context.Context) error {
	var result error

	logrus.Debugln("cron: begin process pending jobs")

	defer func() {
		if err := recover(); err != nil {
			logger := logrus.WithField("error", err)
			logger.Errorln("cron: unexpected panic")
		}
	}()

	now := time.Now()
	jobs, err := s.cron.Ready(ctx, now.Unix())
	if err != nil {
		logger := logrus.WithError(err)
		logger.Error("cron: cannot list pending jobs")
		return err
	}

	for _, job := range jobs {
		// jobs can be manually disabled in the user interface,
		// and should be skipped.
		if job.Disabled {
			continue
		}

		sched, err := cron.Parse(job.Expr)
		if err != nil {
			result = multierror.Append(result, err)
			// this should never happen since we parse and verify
			// the cron expression when the cron entry is created.
			continue
		}

		// calculate the next execution date.
		job.Prev = job.Next
		job.Next = sched.Next(now).Unix()

		logger := logrus.WithFields(
			logrus.Fields{
				"repo": job.RepoID,
				"cron": job.ID,
			},
		)

		err = s.cron.Update(ctx, job)
		if err != nil {
			logger := logrus.WithError(err)
			logger.Warnln("cron: cannot re-schedule job")
			result = multierror.Append(result, err)
			continue
		}

		repo, err := s.repos.Find(ctx, job.RepoID)
		if err != nil {
			logger := logrus.WithError(err)
			logger.Warnln("cron: cannot find repository")
			result = multierror.Append(result, err)
			continue
		}

		user, err := s.users.Find(ctx, repo.UserID)
		if err != nil {
			logger := logrus.WithError(err)
			logger.Warnln("cron: cannot find repository owner")
			result = multierror.Append(result, err)
			continue
		}

		// TODO(bradrydzewski) we may actually need to query the branch
		// first to get the sha, and then query the commit. This works fine
		// with github and gitlab, but may not work with other providers.

		commit, err := s.commits.FindRef(ctx, user, repo.Slug, job.Branch)
		if err != nil {
			logger.WithFields(
				logrus.Fields{
					"error":  err,
					"repo":   repo.Slug,
					"branch": repo.Branch,
				}).Warnln("cron: cannot find commit")
			result = multierror.Append(result, err)
			continue
		}

		hook := &core.Hook{
			Trigger:      core.TriggerCron,
			Event:        core.EventPush,
			Link:         commit.Link,
			Timestamp:    commit.Author.Date,
			Message:      commit.Message,
			After:        commit.Sha,
			Ref:          fmt.Sprintf("refs/heads/%s", job.Branch),
			Target:       job.Branch,
			Author:       commit.Author.Login,
			AuthorName:   commit.Author.Name,
			AuthorEmail:  commit.Author.Email,
			AuthorAvatar: commit.Author.Avatar,
			Sender:       commit.Author.Login,
		}

		_, err = s.trigger.Trigger(ctx, repo, hook)
		if err != nil {
			logger.WithFields(
				logrus.Fields{
					"error":  err,
					"repo":   repo.Slug,
					"branch": repo.Branch,
					"sha":    commit.Sha,
				}).Warnln("cron: cannot trigger build")
			result = multierror.Append(result, err)
			continue
		}
	}

	logrus.Debugf("cron: finished processing jobs")
	return result
}