// Copyright 2017 HootSuite Media Inc.
//
// 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.
// Modified hereafter by contributors to runatlantis/atlantis.

package events

import (
	"fmt"

	"github.com/runatlantis/atlantis/server/events/locking"
	"github.com/runatlantis/atlantis/server/events/models"
	"github.com/runatlantis/atlantis/server/logging"
)

//go:generate pegomock generate -m --use-experimental-model-gen --package mocks -o mocks/mock_project_lock.go ProjectLocker

// ProjectLocker locks this project against other plans being run until this
// project is unlocked.
type ProjectLocker interface {
	// TryLock attempts to acquire the lock for this project. It returns true if the lock
	// was acquired. If it returns false, the lock was not acquired and the second
	// return value will be a string describing why the lock was not acquired.
	// The third return value is a function that can be called to unlock the
	// lock. It will only be set if the lock was acquired. Any errors will set
	// error.
	TryLock(log *logging.SimpleLogger, pull models.PullRequest, user models.User, workspace string, project models.Project) (*TryLockResponse, error)
}

// DefaultProjectLocker implements ProjectLocker.
type DefaultProjectLocker struct {
	Locker locking.Locker
}

// TryLockResponse is the result of trying to lock a project.
type TryLockResponse struct {
	// LockAcquired is true if the lock was acquired.
	LockAcquired bool
	// LockFailureReason is the reason why the lock was not acquired. It will
	// only be set if LockAcquired is false.
	LockFailureReason string
	// UnlockFn will unlock the lock created by the caller. This might be called
	// if there is an error later and the caller doesn't want to continue to
	// hold the lock.
	UnlockFn func() error
	// LockKey is the key for the lock if the lock was acquired.
	LockKey string
}

// TryLock implements ProjectLocker.TryLock.
func (p *DefaultProjectLocker) TryLock(log *logging.SimpleLogger, pull models.PullRequest, user models.User, workspace string, project models.Project) (*TryLockResponse, error) {
	lockAttempt, err := p.Locker.TryLock(project, workspace, pull, user)
	if err != nil {
		return nil, err
	}
	if !lockAttempt.LockAcquired && lockAttempt.CurrLock.Pull.Num != pull.Num {
		failureMsg := fmt.Sprintf(
			"This project is currently locked by #%d. The locking plan must be applied or discarded before future plans can execute.",
			lockAttempt.CurrLock.Pull.Num)
		return &TryLockResponse{
			LockAcquired:      false,
			LockFailureReason: failureMsg,
		}, nil
	}
	log.Info("acquired lock with id %q", lockAttempt.LockKey)
	return &TryLockResponse{
		LockAcquired: true,
		UnlockFn: func() error {
			_, err := p.Locker.Unlock(lockAttempt.LockKey)
			return err
		},
		LockKey: lockAttempt.LockKey,
	}, nil
}