/*
Copyright 2020 The Flux CD contributors.

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 controllers

import (
	"context"
	"fmt"
	"io/ioutil"
	"os"
	"path/filepath"
	"strings"
	"time"

	"github.com/blang/semver"
	"github.com/go-git/go-git/v5"
	"github.com/go-git/go-git/v5/plumbing"
	"github.com/go-git/go-git/v5/plumbing/transport"
	"github.com/go-git/go-git/v5/plumbing/transport/http"
	"github.com/go-git/go-git/v5/plumbing/transport/ssh"
	"github.com/go-logr/logr"
	corev1 "k8s.io/api/core/v1"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/runtime"
	"k8s.io/apimachinery/pkg/types"
	ctrl "sigs.k8s.io/controller-runtime"
	"sigs.k8s.io/controller-runtime/pkg/client"
	"sigs.k8s.io/controller-runtime/pkg/client/apiutil"
	"sigs.k8s.io/controller-runtime/pkg/event"
	"sigs.k8s.io/controller-runtime/pkg/predicate"

	sourcev1 "github.com/fluxcd/source-controller/api/v1alpha1"
)

// GitRepositoryReconciler reconciles a GitRepository object
type GitRepositoryReconciler struct {
	client.Client
	Log     logr.Logger
	Scheme  *runtime.Scheme
	Storage *Storage
}

// +kubebuilder:rbac:groups=source.fluxcd.io,resources=gitrepositories,verbs=get;list;watch;create;update;patch;delete
// +kubebuilder:rbac:groups=source.fluxcd.io,resources=gitrepositories/status,verbs=get;update;patch

func (r *GitRepositoryReconciler) Reconcile(req ctrl.Request) (ctrl.Result, error) {
	ctx, cancel := context.WithTimeout(context.Background(), 15*time.Second)
	defer cancel()

	var repo sourcev1.GitRepository
	if err := r.Get(ctx, req.NamespacedName, &repo); err != nil {
		return ctrl.Result{}, client.IgnoreNotFound(err)
	}

	log := r.Log.WithValues(repo.Kind, req.NamespacedName)

	// set initial status
	if reset, status := r.shouldResetStatus(repo); reset {
		log.Info("Initializing Git repository")
		repo.Status = status
		if err := r.Status().Update(ctx, &repo); err != nil {
			log.Error(err, "unable to update GitRepository status")
			return ctrl.Result{Requeue: true}, err
		}
	}

	// try to remove old artifacts
	r.gc(repo)

	// try git clone
	syncedRepo, err := r.sync(*repo.DeepCopy())
	if err != nil {
		log.Info("Git repository sync failed", "error", err.Error())
	}

	// update status
	if err := r.Status().Update(ctx, &syncedRepo); err != nil {
		log.Error(err, "unable to update GitRepository status")
		return ctrl.Result{Requeue: true}, err
	}

	log.Info("Git repository sync succeeded", "msg", sourcev1.GitRepositoryReadyMessage(syncedRepo))

	// requeue repository
	return ctrl.Result{RequeueAfter: repo.Spec.Interval.Duration}, nil
}

func (r *GitRepositoryReconciler) SetupWithManager(mgr ctrl.Manager) error {
	return ctrl.NewControllerManagedBy(mgr).
		For(&sourcev1.GitRepository{}).
		WithEventFilter(RepositoryChangePredicate{}).
		WithEventFilter(predicate.Funcs{
			DeleteFunc: func(e event.DeleteEvent) bool {
				gvk, err := apiutil.GVKForObject(e.Object, r.Scheme)
				if err != nil {
					r.Log.Error(err, "unable to get GroupVersionKind for deleted object")
					return false
				}
				// delete artifacts
				artifact := r.Storage.ArtifactFor(gvk.Kind, e.Meta, "*", "")
				if err := r.Storage.RemoveAll(artifact); err != nil {
					r.Log.Error(err, "unable to delete artifacts",
						gvk.Kind, fmt.Sprintf("%s/%s", e.Meta.GetNamespace(), e.Meta.GetName()))
				} else {
					r.Log.Info("Git repository artifacts deleted",
						gvk.Kind, fmt.Sprintf("%s/%s", e.Meta.GetNamespace(), e.Meta.GetName()))
				}
				return true
			},
		}).
		Complete(r)
}

func (r *GitRepositoryReconciler) sync(repository sourcev1.GitRepository) (sourcev1.GitRepository, error) {
	// set defaults: master branch, no tags fetching, max two commits
	branch := "master"
	revision := ""
	tagMode := git.NoTags
	depth := 2

	// determine ref
	refName := plumbing.NewBranchReferenceName(branch)
	if repository.Spec.Reference != nil {
		if repository.Spec.Reference.Branch != "" {
			branch = repository.Spec.Reference.Branch
			refName = plumbing.NewBranchReferenceName(branch)
		}
		if repository.Spec.Reference.Commit != "" {
			depth = 0
		} else {
			if repository.Spec.Reference.Tag != "" {
				refName = plumbing.NewTagReferenceName(repository.Spec.Reference.Tag)
			}
			if repository.Spec.Reference.SemVer != "" {
				tagMode = git.AllTags
			}
		}
	}

	// create tmp dir for SSH known_hosts
	tmpSSH, err := ioutil.TempDir("", repository.Name)
	if err != nil {
		err = fmt.Errorf("tmp dir error: %w", err)
		return sourcev1.GitRepositoryNotReady(repository, sourcev1.StorageOperationFailedReason, err.Error()), err
	}
	defer os.RemoveAll(tmpSSH)

	auth, err := r.auth(repository, tmpSSH)
	if err != nil {
		err = fmt.Errorf("auth error: %w", err)
		return sourcev1.GitRepositoryNotReady(repository, sourcev1.StorageOperationFailedReason, err.Error()), err
	}

	// create tmp dir for the Git clone
	tmpGit, err := ioutil.TempDir("", repository.Name)
	if err != nil {
		err = fmt.Errorf("tmp dir error: %w", err)
		return sourcev1.GitRepositoryNotReady(repository, sourcev1.StorageOperationFailedReason, err.Error()), err
	}
	defer os.RemoveAll(tmpGit)

	// clone to tmp
	repo, err := git.PlainClone(tmpGit, false, &git.CloneOptions{
		URL:               repository.Spec.URL,
		Auth:              auth,
		RemoteName:        "origin",
		ReferenceName:     refName,
		SingleBranch:      true,
		NoCheckout:        false,
		Depth:             depth,
		RecurseSubmodules: 0,
		Progress:          nil,
		Tags:              tagMode,
	})
	if err != nil {
		err = fmt.Errorf("git clone error: %w", err)
		return sourcev1.GitRepositoryNotReady(repository, sourcev1.GitOperationFailedReason, err.Error()), err
	}

	// checkout commit or tag
	if repository.Spec.Reference != nil {
		if commit := repository.Spec.Reference.Commit; commit != "" {
			w, err := repo.Worktree()
			if err != nil {
				err = fmt.Errorf("git worktree error: %w", err)
				return sourcev1.GitRepositoryNotReady(repository, sourcev1.GitOperationFailedReason, err.Error()), err
			}

			err = w.Checkout(&git.CheckoutOptions{
				Hash:  plumbing.NewHash(commit),
				Force: true,
			})
			if err != nil {
				err = fmt.Errorf("git checkout '%s' for '%s' error: %w", commit, branch, err)
				return sourcev1.GitRepositoryNotReady(repository, sourcev1.GitOperationFailedReason, err.Error()), err
			}
		} else if exp := repository.Spec.Reference.SemVer; exp != "" {
			rng, err := semver.ParseRange(exp)
			if err != nil {
				err = fmt.Errorf("semver parse range error: %w", err)
				return sourcev1.GitRepositoryNotReady(repository, sourcev1.GitOperationFailedReason, err.Error()), err
			}

			repoTags, err := repo.Tags()
			if err != nil {
				err = fmt.Errorf("git list tags error: %w", err)
				return sourcev1.GitRepositoryNotReady(repository, sourcev1.GitOperationFailedReason, err.Error()), err
			}

			tags := make(map[string]string)
			_ = repoTags.ForEach(func(t *plumbing.Reference) error {
				tags[t.Name().Short()] = t.Strings()[1]
				return nil
			})

			svTags := make(map[string]string)
			var svers []semver.Version
			for tag, _ := range tags {
				v, _ := semver.ParseTolerant(tag)
				if rng(v) {
					svers = append(svers, v)
					svTags[v.String()] = tag
				}
			}

			if len(svers) > 0 {
				semver.Sort(svers)
				v := svers[len(svers)-1]
				t := svTags[v.String()]
				commit := tags[t]
				revision = fmt.Sprintf("%s/%s", t, commit)

				w, err := repo.Worktree()
				if err != nil {
					err = fmt.Errorf("git worktree error: %w", err)
					return sourcev1.GitRepositoryNotReady(repository, sourcev1.GitOperationFailedReason, err.Error()), err
				}

				err = w.Checkout(&git.CheckoutOptions{
					Hash: plumbing.NewHash(commit),
				})
				if err != nil {
					err = fmt.Errorf("git checkout error: %w", err)
					return sourcev1.GitRepositoryNotReady(repository, sourcev1.GitOperationFailedReason, err.Error()), err
				}
			} else {
				err = fmt.Errorf("no match found for semver: %s", repository.Spec.Reference.SemVer)
				return sourcev1.GitRepositoryNotReady(repository, sourcev1.GitOperationFailedReason, err.Error()), err
			}
		}
	}

	// read commit hash
	ref, err := repo.Head()
	if err != nil {
		err = fmt.Errorf("git resolve HEAD error: %w", err)
		return sourcev1.GitRepositoryNotReady(repository, sourcev1.GitOperationFailedReason, err.Error()), err
	}

	if revision == "" {
		revision = fmt.Sprintf("%s/%s", branch, ref.Hash().String())
	}

	artifact := r.Storage.ArtifactFor(repository.Kind, repository.ObjectMeta.GetObjectMeta(),
		fmt.Sprintf("%s.tar.gz", ref.Hash().String()), revision)

	// create artifact dir
	err = r.Storage.MkdirAll(artifact)
	if err != nil {
		err = fmt.Errorf("mkdir dir error: %w", err)
		return sourcev1.GitRepositoryNotReady(repository, sourcev1.StorageOperationFailedReason, err.Error()), err
	}

	// acquire lock
	unlock, err := r.Storage.Lock(artifact)
	if err != nil {
		err = fmt.Errorf("unable to acquire lock: %w", err)
		return sourcev1.GitRepositoryNotReady(repository, sourcev1.StorageOperationFailedReason, err.Error()), err
	}
	defer unlock()

	// archive artifact
	err = r.Storage.Archive(artifact, tmpGit, "")
	if err != nil {
		err = fmt.Errorf("storage archive error: %w", err)
		return sourcev1.GitRepositoryNotReady(repository, sourcev1.StorageOperationFailedReason, err.Error()), err
	}

	// update latest symlink
	url, err := r.Storage.Symlink(artifact, "latest.tar.gz")
	if err != nil {
		err = fmt.Errorf("storage lock error: %w", err)
		return sourcev1.GitRepositoryNotReady(repository, sourcev1.StorageOperationFailedReason, err.Error()), err
	}

	message := fmt.Sprintf("Git repoistory artifacts are available at: %s", artifact.Path)
	return sourcev1.GitRepositoryReady(repository, artifact, url, sourcev1.GitOperationSucceedReason, message), nil
}

func (r *GitRepositoryReconciler) shouldResetStatus(repository sourcev1.GitRepository) (bool, sourcev1.GitRepositoryStatus) {
	resetStatus := false
	if repository.Status.Artifact != nil {
		if !r.Storage.ArtifactExist(*repository.Status.Artifact) {
			resetStatus = true
		}
	}

	// set initial status
	if len(repository.Status.Conditions) == 0 || resetStatus {
		resetStatus = true
	}

	return resetStatus, sourcev1.GitRepositoryStatus{
		Conditions: []sourcev1.SourceCondition{
			{
				Type:               sourcev1.ReadyCondition,
				Status:             corev1.ConditionUnknown,
				Reason:             sourcev1.InitializingReason,
				LastTransitionTime: metav1.Now(),
			},
		},
	}
}

func (r *GitRepositoryReconciler) gc(repository sourcev1.GitRepository) {
	if repository.Status.Artifact != nil {
		if err := r.Storage.RemoveAllButCurrent(*repository.Status.Artifact); err != nil {
			r.Log.Info("Artifacts GC failed", "error", err)
		}
	}
}

func (r *GitRepositoryReconciler) auth(repository sourcev1.GitRepository, tmp string) (transport.AuthMethod, error) {
	if repository.Spec.SecretRef == nil {
		return nil, nil
	}

	name := types.NamespacedName{
		Namespace: repository.GetNamespace(),
		Name:      repository.Spec.SecretRef.Name,
	}

	var secret corev1.Secret
	err := r.Client.Get(context.TODO(), name, &secret)
	if err != nil {
		return nil, err
	}

	credentials := secret.Data

	// HTTP auth
	if strings.HasPrefix(repository.Spec.URL, "http") {
		auth := &http.BasicAuth{}
		if username, ok := credentials["username"]; ok {
			auth.Username = string(username)
		}
		if password, ok := credentials["password"]; ok {
			auth.Password = string(password)
		}

		if auth.Username == "" || auth.Password == "" {
			return nil, fmt.Errorf("invalid '%s' secret data: required fields username and password",
				repository.Spec.SecretRef.Name)
		}

		return auth, nil
	}

	// SSH auth
	if strings.HasPrefix(repository.Spec.URL, "ssh") {
		var privateKey []byte
		if identity, ok := credentials["identity"]; ok {
			privateKey = identity
		} else {
			return nil, fmt.Errorf("invalid '%s' secret data: required field identity", repository.Spec.SecretRef.Name)
		}

		pk, err := ssh.NewPublicKeys("git", privateKey, "")
		if err != nil {
			return nil, err
		}

		known_hosts := filepath.Join(tmp, "known_hosts")
		if kh, ok := credentials["known_hosts"]; ok {
			if err := ioutil.WriteFile(filepath.Join(tmp, "known_hosts"), kh, 0644); err != nil {
				return nil, err
			}
		} else {
			return nil, fmt.Errorf("invalid '%s' secret data: required field known_hosts", repository.Spec.SecretRef.Name)
		}

		callback, err := ssh.NewKnownHostsCallback(known_hosts)
		if err != nil {
			return nil, err
		}
		pk.HostKeyCallback = callback

		return pk, nil
	}

	return nil, nil
}