/*
Copyright 2015 Google Inc. All rights reserved.

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 repository

import (
	"crypto/sha1"
	"encoding/json"
	"fmt"
	"strings"
)

// Constants used for testing.
// We initialize our mock repo with two branches (one of which holds a pending review),
// and commit history that looks like this:
//
//  Master Branch:    A--B--D--E--F--J
//                     \   /    \  \
//                       C       \  \
//                                \  \
//  Review Branch:                 G--H--I
//
// Where commits "B" and "D" represent reviews that have been submitted, and "G"
// is a pending review.
const (
	TestTargetRef          = "refs/heads/master"
	TestReviewRef          = "refs/heads/ojarjur/mychange"
	TestAlternateReviewRef = "refs/review/mychange"
	TestRequestsRef        = "refs/notes/devtools/reviews"
	TestCommentsRef        = "refs/notes/devtools/discuss"

	TestCommitA = "A"
	TestCommitB = "B"
	TestCommitC = "C"
	TestCommitD = "D"
	TestCommitE = "E"
	TestCommitF = "F"
	TestCommitG = "G"
	TestCommitH = "H"
	TestCommitI = "I"
	TestCommitJ = "J"

	TestRequestB = `{"timestamp": "0000000001", "reviewRef": "refs/heads/ojarjur/mychange", "targetRef": "refs/heads/master", "requester": "ojarjur", "reviewers": ["ojarjur"], "description": "B"}`
	TestRequestD = `{"timestamp": "0000000002", "reviewRef": "refs/heads/ojarjur/mychange", "targetRef": "refs/heads/master", "requester": "ojarjur", "reviewers": ["ojarjur"], "description": "D"}`
	TestRequestG = `{"timestamp": "0000000004", "reviewRef": "refs/heads/ojarjur/mychange", "targetRef": "refs/heads/master", "requester": "ojarjur", "reviewers": ["ojarjur"], "description": "G"}

{"timestamp": "0000000005", "reviewRef": "refs/heads/ojarjur/mychange", "targetRef": "refs/heads/master", "requester": "ojarjur", "reviewers": ["ojarjur"], "description": "Updated description of G"}

{"timestamp": "0000000005", "reviewRef": "refs/heads/ojarjur/mychange", "targetRef": "refs/heads/master", "requester": "ojarjur", "reviewers": ["ojarjur"], "description": "Final description of G"}`

	TestDiscussB = `{"timestamp": "0000000001", "author": "ojarjur", "location": {"commit": "B"}, "resolved": true}`
	TestDiscussD = `{"timestamp": "0000000003", "author": "ojarjur", "location": {"commit": "E"}, "resolved": true}`
)

type mockCommit struct {
	Message string   `json:"message,omitempty"`
	Time    string   `json:"time,omitempty"`
	Parents []string `json:"parents,omitempty"`
}

// mockRepoForTest defines an instance of Repo that can be used for testing.
type mockRepoForTest struct {
	Head    string
	Refs    map[string]string            `json:"refs,omitempty"`
	Commits map[string]mockCommit        `json:"commits,omitempty"`
	Notes   map[string]map[string]string `json:"notes,omitempty"`
}

func (r *mockRepoForTest) createCommit(message string, time string, parents []string) (string, error) {
	newCommit := mockCommit{
		Message: message,
		Time:    time,
		Parents: parents,
	}
	newCommitJSON, err := json.Marshal(newCommit)
	if err != nil {
		return "", err
	}
	newCommitHash := fmt.Sprintf("%x", sha1.Sum([]byte(newCommitJSON)))
	r.Commits[newCommitHash] = newCommit
	return newCommitHash, nil
}

// NewMockRepoForTest returns a mocked-out instance of the Repo interface that has been pre-populated with test data.
func NewMockRepoForTest() Repo {
	commitA := mockCommit{
		Message: "First commit",
		Time:    "0",
		Parents: nil,
	}
	commitB := mockCommit{
		Message: "Second commit",
		Time:    "1",
		Parents: []string{TestCommitA},
	}
	commitC := mockCommit{
		Message: "No, I'm the second commit",
		Time:    "1",
		Parents: []string{TestCommitA},
	}
	commitD := mockCommit{
		Message: "Fourth commit",
		Time:    "2",
		Parents: []string{TestCommitB, TestCommitC},
	}
	commitE := mockCommit{
		Message: "Fifth commit",
		Time:    "3",
		Parents: []string{TestCommitD},
	}
	commitF := mockCommit{
		Message: "Sixth commit",
		Time:    "4",
		Parents: []string{TestCommitE},
	}
	commitG := mockCommit{
		Message: "No, I'm the sixth commit",
		Time:    "4",
		Parents: []string{TestCommitE},
	}
	commitH := mockCommit{
		Message: "Seventh commit",
		Time:    "5",
		Parents: []string{TestCommitG, TestCommitF},
	}
	commitI := mockCommit{
		Message: "Eighth commit",
		Time:    "6",
		Parents: []string{TestCommitH},
	}
	commitJ := mockCommit{
		Message: "No, I'm the eighth commit",
		Time:    "6",
		Parents: []string{TestCommitF},
	}
	return &mockRepoForTest{
		Head: TestTargetRef,
		Refs: map[string]string{
			TestTargetRef:          TestCommitJ,
			TestReviewRef:          TestCommitI,
			TestAlternateReviewRef: TestCommitI,
		},
		Commits: map[string]mockCommit{
			TestCommitA: commitA,
			TestCommitB: commitB,
			TestCommitC: commitC,
			TestCommitD: commitD,
			TestCommitE: commitE,
			TestCommitF: commitF,
			TestCommitG: commitG,
			TestCommitH: commitH,
			TestCommitI: commitI,
			TestCommitJ: commitJ,
		},
		Notes: map[string]map[string]string{
			TestRequestsRef: map[string]string{
				TestCommitB: TestRequestB,
				TestCommitD: TestRequestD,
				TestCommitG: TestRequestG,
			},
			TestCommentsRef: map[string]string{
				TestCommitB: TestDiscussB,
				TestCommitD: TestDiscussD,
			},
		},
	}
}

// GetPath returns the path to the repo.
func (r *mockRepoForTest) GetPath() string { return "~/mockRepo/" }

// GetRepoStateHash returns a hash which embodies the entire current state of a repository.
func (r *mockRepoForTest) GetRepoStateHash() (string, error) {
	repoJSON, err := json.Marshal(r)
	if err != nil {
		return "", err
	}
	return fmt.Sprintf("%x", sha1.Sum([]byte(repoJSON))), nil
}

// GetUserEmail returns the email address that the user has used to configure git.
func (r *mockRepoForTest) GetUserEmail() (string, error) { return "user@example.com", nil }

// GetUserSigningKey returns the key id the user has configured for
// sigining git artifacts.
func (r *mockRepoForTest) GetUserSigningKey() (string, error) {
	return "gpgsig", nil
}

// GetCoreEditor returns the name of the editor that the user has used to configure git.
func (r *mockRepoForTest) GetCoreEditor() (string, error) { return "vi", nil }

// GetSubmitStrategy returns the way in which a review is submitted
func (r *mockRepoForTest) GetSubmitStrategy() (string, error) { return "merge", nil }

// HasUncommittedChanges returns true if there are local, uncommitted changes.
func (r *mockRepoForTest) HasUncommittedChanges() (bool, error) { return false, nil }

func (r *mockRepoForTest) resolveLocalRef(ref string) (string, error) {
	if ref == "HEAD" {
		ref = r.Head
	}
	if commit, ok := r.Refs[ref]; ok {
		return commit, nil
	}
	if _, ok := r.Commits[ref]; ok {
		return ref, nil
	}
	return "", fmt.Errorf("The ref %q does not exist", ref)
}

// VerifyCommit verifies that the supplied hash points to a known commit.
func (r *mockRepoForTest) VerifyCommit(hash string) error {
	if _, ok := r.Commits[hash]; !ok {
		return fmt.Errorf("The given hash %q is not a known commit", hash)
	}
	return nil
}

// VerifyGitRef verifies that the supplied ref points to a known commit.
func (r *mockRepoForTest) VerifyGitRef(ref string) error {
	_, err := r.resolveLocalRef(ref)
	return err
}

// GetHeadRef returns the ref that is the current HEAD.
func (r *mockRepoForTest) GetHeadRef() (string, error) { return r.Head, nil }

// GetCommitHash returns the hash of the commit pointed to by the given ref.
func (r *mockRepoForTest) GetCommitHash(ref string) (string, error) {
	err := r.VerifyGitRef(ref)
	if err != nil {
		return "", err
	}
	return r.resolveLocalRef(ref)
}

// ResolveRefCommit returns the commit pointed to by the given ref, which may be a remote ref.
//
// This differs from GetCommitHash which only works on exact matches, in that it will try to
// intelligently handle the scenario of a ref not existing locally, but being known to exist
// in a remote repo.
//
// This method should be used when a command may be performed by either the reviewer or the
// reviewee, while GetCommitHash should be used when the encompassing command should only be
// performed by the reviewee.
func (r *mockRepoForTest) ResolveRefCommit(ref string) (string, error) {
	if commit, err := r.resolveLocalRef(ref); err == nil {
		return commit, err
	}
	return r.resolveLocalRef(strings.Replace(ref, "refs/heads/", "refs/remotes/origin/", 1))
}

func (r *mockRepoForTest) getCommit(ref string) (mockCommit, error) {
	commit, err := r.resolveLocalRef(ref)
	return r.Commits[commit], err
}

// GetCommitMessage returns the message stored in the commit pointed to by the given ref.
func (r *mockRepoForTest) GetCommitMessage(ref string) (string, error) {
	commit, err := r.getCommit(ref)
	if err != nil {
		return "", err
	}
	return commit.Message, nil
}

// GetCommitTime returns the commit time of the commit pointed to by the given ref.
func (r *mockRepoForTest) GetCommitTime(ref string) (string, error) {
	commit, err := r.getCommit(ref)
	if err != nil {
		return "", err
	}
	return commit.Time, nil
}

// GetLastParent returns the last parent of the given commit (as ordered by git).
func (r *mockRepoForTest) GetLastParent(ref string) (string, error) {
	commit, err := r.getCommit(ref)
	if len(commit.Parents) > 0 {
		return commit.Parents[len(commit.Parents)-1], err
	}
	return "", err
}

// GetCommitDetails returns the details of a commit's metadata.
func (r *mockRepoForTest) GetCommitDetails(ref string) (*CommitDetails, error) {
	commit, err := r.getCommit(ref)
	if err != nil {
		return nil, err
	}
	var details CommitDetails
	details.Author = "Test Author"
	details.AuthorEmail = "author@example.com"
	details.Summary = commit.Message
	details.Time = commit.Time
	details.Parents = commit.Parents
	return &details, nil
}

// ancestors returns the breadth-first traversal of a commit's ancestors
func (r *mockRepoForTest) ancestors(commit string) ([]string, error) {
	queue := []string{commit}
	var ancestors []string
	for queue != nil {
		var nextQueue []string
		for _, c := range queue {
			commit, err := r.getCommit(c)
			if err != nil {
				return nil, err
			}
			parents := commit.Parents
			nextQueue = append(nextQueue, parents...)
			ancestors = append(ancestors, parents...)
		}
		queue = nextQueue
	}
	return ancestors, nil
}

// IsAncestor determines if the first argument points to a commit that is an ancestor of the second.
func (r *mockRepoForTest) IsAncestor(ancestor, descendant string) (bool, error) {
	var err error
	ancestor, err = r.resolveLocalRef(ancestor)
	if err != nil {
		return false, err
	}
	descendant, err = r.resolveLocalRef(descendant)
	if err != nil {
		return false, err
	}
	if ancestor == descendant {
		return true, nil
	}
	descendantCommit, err := r.getCommit(descendant)
	if err != nil {
		return false, err
	}
	for _, parent := range descendantCommit.Parents {
		if t, e := r.IsAncestor(ancestor, parent); e == nil && t {
			return true, nil
		}
	}
	return false, nil
}

// MergeBase determines if the first commit that is an ancestor of the two arguments.
func (r *mockRepoForTest) MergeBase(a, b string) (string, error) {
	ancestors, err := r.ancestors(a)
	if err != nil {
		return "", err
	}
	for _, ancestor := range ancestors {
		if t, e := r.IsAncestor(ancestor, b); e == nil && t {
			return ancestor, nil
		}
	}
	return "", nil
}

// Diff computes the diff between two given commits.
func (r *mockRepoForTest) Diff(left, right string, diffArgs ...string) (string, error) {
	return fmt.Sprintf("Diff between %q and %q", left, right), nil
}

// Show returns the contents of the given file at the given commit.
func (r *mockRepoForTest) Show(commit, path string) (string, error) {
	return fmt.Sprintf("%s:%s", commit, path), nil
}

// SwitchToRef changes the currently-checked-out ref.
func (r *mockRepoForTest) SwitchToRef(ref string) error {
	r.Head = ref
	return nil
}

// ArchiveRef adds the current commit pointed to by the 'ref' argument
// under the ref specified in the 'archive' argument.
//
// Both the 'ref' and 'archive' arguments are expected to be the fully
// qualified names of git refs (e.g. 'refs/heads/my-change' or
// 'refs/archive/devtools').
//
// If the ref pointed to by the 'archive' argument does not exist
// yet, then it will be created.
func (r *mockRepoForTest) ArchiveRef(ref, archive string) error {
	commitToArchive, err := r.resolveLocalRef(ref)
	if err != nil {
		return err
	}
	var archiveParents []string
	if archiveCommit, err := r.resolveLocalRef(archive); err == nil {
		archiveParents = []string{archiveCommit, commitToArchive}
	} else {
		archiveParents = []string{commitToArchive}
	}
	archiveCommit, err := r.createCommit("Archiving", "Nowish", archiveParents)
	if err != nil {
		return err
	}
	r.Refs[archive] = archiveCommit
	return nil
}

// MergeRef merges the given ref into the current one.
//
// The ref argument is the ref to merge, and fastForward indicates that the
// current ref should only move forward, as opposed to creating a bubble merge.
func (r *mockRepoForTest) MergeRef(ref string, fastForward bool, messages ...string) error {
	newCommitHash, err := r.resolveLocalRef(ref)
	if err != nil {
		return err
	}
	if !fastForward {
		origCommit, err := r.resolveLocalRef(r.Head)
		if err != nil {
			return err
		}
		newCommit, err := r.getCommit(ref)
		if err != nil {
			return err
		}
		message := strings.Join(messages, "\n\n")
		time := newCommit.Time
		parents := []string{origCommit, newCommitHash}
		newCommitHash, err = r.createCommit(message, time, parents)
		if err != nil {
			return err
		}
	}
	r.Refs[r.Head] = newCommitHash
	return nil
}

// MergeAndSignRef merges the given ref into the current one and signs the
// merge.
//
// The ref argument is the ref to merge, and fastForward indicates that the
// current ref should only move forward, as opposed to creating a bubble merge.
func (r *mockRepoForTest) MergeAndSignRef(ref string, fastForward bool,
	messages ...string) error {
	return nil
}

// RebaseRef rebases the current ref onto the given one.
func (r *mockRepoForTest) RebaseRef(ref string) error {
	parentHash := r.Refs[ref]
	origCommit, err := r.getCommit(r.Head)
	if err != nil {
		return err
	}
	newCommitHash, err := r.createCommit(origCommit.Message, origCommit.Time, []string{parentHash})
	if err != nil {
		return err
	}
	if strings.HasPrefix(r.Head, "refs/heads/") {
		r.Refs[r.Head] = newCommitHash
	} else {
		// The current head is not a branch, so updating
		// it should leave us in a detached-head state.
		r.Head = newCommitHash
	}
	return nil
}

// RebaseAndSignRef rebases the current ref onto the given one and signs the
// result.
func (r *mockRepoForTest) RebaseAndSignRef(ref string) error { return nil }

// ListCommits returns the list of commits reachable from the given ref.
//
// The generated list is in chronological order (with the oldest commit first).
//
// If the specified ref does not exist, then this method returns an empty result.
func (r *mockRepoForTest) ListCommits(ref string) []string { return nil }

// ListCommitsBetween returns the list of commits between the two given revisions.
//
// The "from" parameter is the starting point (exclusive), and the "to"
// parameter is the ending point (inclusive).
//
// The "from" commit does not need to be an ancestor of the "to" commit. If it
// is not, then the merge base of the two is used as the starting point.
// Admittedly, this makes calling these the "between" commits is a bit of a
// misnomer, but it also makes the method easier to use when you want to
// generate the list of changes in a feature branch, as it eliminates the need
// to explicitly calculate the merge base. This also makes the semantics of the
// method compatible with git's built-in "rev-list" command.
//
// The generated list is in chronological order (with the oldest commit first).
func (r *mockRepoForTest) ListCommitsBetween(from, to string) ([]string, error) {
	commits := []string{to}
	potentialCommits, _ := r.ancestors(to)
	for _, commit := range potentialCommits {
		blocked, err := r.IsAncestor(commit, from)
		if err != nil {
			return nil, err
		}
		if !blocked {
			commits = append(commits, commit)
		}
	}
	return commits, nil
}

// GetNotes reads the notes from the given ref that annotate the given revision.
func (r *mockRepoForTest) GetNotes(notesRef, revision string) []Note {
	notesText := r.Notes[notesRef][revision]
	var notes []Note
	for _, line := range strings.Split(notesText, "\n") {
		notes = append(notes, Note(line))
	}
	return notes
}

// GetAllNotes reads the contents of the notes under the given ref for every commit.
//
// The returned value is a mapping from commit hash to the list of notes for that commit.
//
// This is the batch version of the corresponding GetNotes(...) method.
func (r *mockRepoForTest) GetAllNotes(notesRef string) (map[string][]Note, error) {
	notesMap := make(map[string][]Note)
	for _, commit := range r.ListNotedRevisions(notesRef) {
		notesMap[commit] = r.GetNotes(notesRef, commit)
	}
	return notesMap, nil
}

// AppendNote appends a note to a revision under the given ref.
func (r *mockRepoForTest) AppendNote(ref, revision string, note Note) error {
	existingNotes := r.Notes[ref][revision]
	newNotes := existingNotes + "\n" + string(note)
	r.Notes[ref][revision] = newNotes
	return nil
}

// ListNotedRevisions returns the collection of revisions that are annotated by notes in the given ref.
func (r *mockRepoForTest) ListNotedRevisions(notesRef string) []string {
	var revisions []string
	for revision := range r.Notes[notesRef] {
		if _, ok := r.Commits[revision]; ok {
			revisions = append(revisions, revision)
		}
	}
	return revisions
}

// PushNotes pushes git notes to a remote repo.
func (r *mockRepoForTest) PushNotes(remote, notesRefPattern string) error { return nil }

// PullNotes fetches the contents of the given notes ref from a remote repo,
// and then merges them with the corresponding local notes using the
// "cat_sort_uniq" strategy.
func (r *mockRepoForTest) PullNotes(remote, notesRefPattern string) error { return nil }

// PushNotesAndArchive pushes the given notes and archive refs to a remote repo.
func (r *mockRepoForTest) PushNotesAndArchive(remote, notesRefPattern, archiveRefPattern string) error {
	return nil
}

// PullNotesAndArchive fetches the contents of the notes and archives refs from
// a remote repo, and merges them with the corresponding local refs.
//
// For notes refs, we assume that every note can be automatically merged using
// the 'cat_sort_uniq' strategy (the git-appraise schemas fit that requirement),
// so we automatically merge the remote notes into the local notes.
//
// For "archive" refs, they are expected to be used solely for maintaining
// reachability of commits that are part of the history of any reviews,
// so we do not maintain any consistency with their tree objects. Instead,
// we merely ensure that their history graph includes every commit that we
// intend to keep.
func (r *mockRepoForTest) PullNotesAndArchive(remote, notesRefPattern, archiveRefPattern string) error {
	return nil
}

// MergeNotes merges in the remote's state of the archives reference into
// the local repository's.
func (repo *mockRepoForTest) MergeNotes(remote, notesRefPattern string) error {
	return nil
}

// MergeArchives merges in the remote's state of the archives reference into
// the local repository's.
func (repo *mockRepoForTest) MergeArchives(remote,
	archiveRefPattern string) error {
	return nil
}

// FetchAndReturnNewReviewHashes fetches the notes "branches" and then susses
// out the IDs (the revision the review points to) of any new reviews, then
// returns that list of IDs.
//
// This is accomplished by determining which files in the notes tree have
// changed because the _names_ of these files correspond to the revisions they
// point to.
func (repo *mockRepoForTest) FetchAndReturnNewReviewHashes(remote, notesRefPattern,
	archiveRefPattern string) ([]string, error) {
	return nil, nil
}