// Copyright 2021 The Tint Authors.
//
// 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 gerrit provides helpers for obtaining information from Tint's gerrit instance
package gerrit

import (
	"flag"
	"fmt"
	"io/ioutil"
	"net/url"
	"os"
	"regexp"
	"strconv"
	"strings"

	"github.com/andygrunwald/go-gerrit"
)

// Gerrit is the interface to gerrit
type Gerrit struct {
	client        *gerrit.Client
	authenticated bool
}

// Credentials holds the user name and password used to access Gerrit.
type Credentials struct {
	Username string
	Password string
}

// Patchset refers to a single gerrit patchset
type Patchset struct {
	// Gerrit host
	Host string
	// Gerrit project
	Project string
	// Change ID
	Change int
	// Patchset ID
	Patchset int
}

// ChangeInfo is an alias to gerrit.ChangeInfo
type ChangeInfo = gerrit.ChangeInfo

// LatestPatchest returns the latest Patchset from the ChangeInfo
func LatestPatchest(change *ChangeInfo) Patchset {
	u, _ := url.Parse(change.URL)
	ps := Patchset{
		Host:     u.Host,
		Project:  change.Project,
		Change:   change.Number,
		Patchset: change.Revisions[change.CurrentRevision].Number,
	}
	return ps
}

// RegisterFlags registers the command line flags to populate p
func (p *Patchset) RegisterFlags(defaultHost, defaultProject string) {
	flag.StringVar(&p.Host, "host", defaultHost, "gerrit host")
	flag.StringVar(&p.Project, "project", defaultProject, "gerrit project")
	flag.IntVar(&p.Change, "cl", 0, "gerrit change id")
	flag.IntVar(&p.Patchset, "ps", 0, "gerrit patchset id")
}

// RefsChanges returns the gerrit 'refs/changes/X/Y/Z' string for the patchset
func (p Patchset) RefsChanges() string {
	// https://gerrit-review.googlesource.com/Documentation/intro-user.html
	// A change ref has the format refs/changes/X/Y/Z where X is the last two
	// digits of the change number, Y is the entire change number, and Z is the
	// patch set. For example, if the change number is 263270, the ref would be
	// refs/changes/70/263270/2 for the second patch set.
	shortChange := fmt.Sprintf("%.2v", p.Change)
	shortChange = shortChange[len(shortChange)-2:]
	return fmt.Sprintf("refs/changes/%v/%v/%v", shortChange, p.Change, p.Patchset)
}

// LoadCredentials attempts to load the gerrit credentials for the given gerrit
// URL from the git cookies file. Returns an empty Credentials on failure.
func LoadCredentials(url string) Credentials {
	cookiesFile := os.Getenv("HOME") + "/.gitcookies"
	if cookies, err := ioutil.ReadFile(cookiesFile); err == nil {
		url := strings.TrimSuffix(strings.TrimPrefix(url, "https://"), "/")
		re := regexp.MustCompile(url + `/?\s+(?:FALSE|TRUE)[\s/]+(?:FALSE|TRUE)\s+[0-9]+\s+.\s+(.*)=(.*)`)
		match := re.FindStringSubmatch(string(cookies))
		if len(match) == 3 {
			return Credentials{match[1], match[2]}
		}
	}
	return Credentials{}
}

// New returns a new Gerrit instance. If credentials are not provided, then
// New() will automatically attempt to load them from the gitcookies file.
func New(url string, cred Credentials) (*Gerrit, error) {
	client, err := gerrit.NewClient(url, nil)
	if err != nil {
		return nil, fmt.Errorf("couldn't create gerrit client: %w", err)
	}

	if cred.Username == "" {
		cred = LoadCredentials(url)
	}

	if cred.Username != "" {
		client.Authentication.SetBasicAuth(cred.Username, cred.Password)
	}

	return &Gerrit{client, cred.Username != ""}, nil
}

// QueryChanges returns the changes that match the given query strings.
// See: https://gerrit-review.googlesource.com/Documentation/user-search.html#search-operators
func (g *Gerrit) QueryChanges(querys ...string) (changes []gerrit.ChangeInfo, query string, err error) {
	changes = []gerrit.ChangeInfo{}
	query = strings.Join(querys, "+")
	for {
		batch, _, err := g.client.Changes.QueryChanges(&gerrit.QueryChangeOptions{
			QueryOptions: gerrit.QueryOptions{Query: []string{query}},
			Skip:         len(changes),
		})
		if err != nil {
			return nil, "", g.maybeWrapError(err)
		}

		changes = append(changes, *batch...)
		if len(*batch) == 0 || !(*batch)[len(*batch)-1].MoreChanges {
			break
		}
	}
	return changes, query, nil
}

// Abandon abandons the change with the given changeID.
func (g *Gerrit) Abandon(changeID string) error {
	_, _, err := g.client.Changes.AbandonChange(changeID, &gerrit.AbandonInput{})
	if err != nil {
		return g.maybeWrapError(err)
	}
	return nil
}

// CreateChange creates a new change in the given project and branch, with the
// given subject. If wip is true, then the change is constructed as
// Work-In-Progress.
func (g *Gerrit) CreateChange(project, branch, subject string, wip bool) (*ChangeInfo, error) {
	change, _, err := g.client.Changes.CreateChange(&gerrit.ChangeInput{
		Project:        project,
		Branch:         branch,
		Subject:        subject,
		WorkInProgress: wip,
	})
	if err != nil {
		return nil, g.maybeWrapError(err)
	}
	return change, nil
}

// EditFiles replaces the content of the files in the given change. It deletes deletedFiles.
// If newCommitMsg is not an empty string, then the commit message is replaced
// with the string value.
func (g *Gerrit) EditFiles(changeID, newCommitMsg string, files map[string]string, deletedFiles []string) (Patchset, error) {
	if newCommitMsg != "" {
		resp, err := g.client.Changes.ChangeCommitMessageInChangeEdit(changeID, &gerrit.ChangeEditMessageInput{
			Message: newCommitMsg,
		})
		if err != nil && resp.StatusCode != 409 { // 409 no changes were made
			return Patchset{}, g.maybeWrapError(err)
		}
	}
	for path, content := range files {
		resp, err := g.client.Changes.ChangeFileContentInChangeEdit(changeID, path, content)
		if err != nil && resp.StatusCode != 409 { // 409 no changes were made
			return Patchset{}, g.maybeWrapError(err)
		}
	}
	for _, path := range deletedFiles {
		resp, err := g.client.Changes.DeleteFileInChangeEdit(changeID, path)
		if err != nil && resp.StatusCode != 409 { // 409 no changes were made
			return Patchset{}, g.maybeWrapError(err)
		}
	}

	resp, err := g.client.Changes.PublishChangeEdit(changeID, "NONE")
	if err != nil && resp.StatusCode != 409 { // 409 no changes were made
		return Patchset{}, g.maybeWrapError(err)
	}

	return g.LatestPatchest(changeID)
}

// LatestPatchest returns the latest patchset for the change.
func (g *Gerrit) LatestPatchest(changeID string) (Patchset, error) {
	change, _, err := g.client.Changes.GetChange(changeID, &gerrit.ChangeOptions{
		AdditionalFields: []string{"CURRENT_REVISION"},
	})
	if err != nil {
		return Patchset{}, g.maybeWrapError(err)
	}
	ps := Patchset{
		Host:     g.client.BaseURL().Host,
		Project:  change.Project,
		Change:   change.Number,
		Patchset: change.Revisions[change.CurrentRevision].Number,
	}
	return ps, nil
}

// CommentSide is an enumerator for specifying which side code-comments should
// be shown.
type CommentSide int

const (
	// Left is used to specifiy that code comments should appear on the parent
	// change
	Left CommentSide = iota
	// Right is used to specifiy that code comments should appear on the new
	// change
	Right
)

// FileComment describes a single comment on a file
type FileComment struct {
	Path    string      // The file path
	Side    CommentSide // Which side the comment should appear
	Line    int         // The 1-based line number for the comment
	Message string      // The comment message
}

// Comment posts a review comment on the given patchset.
// If comments is an optional list of file-comments to include in the comment.
func (g *Gerrit) Comment(ps Patchset, msg string, comments []FileComment) error {
	input := &gerrit.ReviewInput{
		Message: msg,
	}
	if len(comments) > 0 {
		input.Comments = map[string][]gerrit.CommentInput{}
		for _, c := range comments {
			ci := gerrit.CommentInput{
				Line: c.Line,
				// Updated: &gerrit.Timestamp{Time: time.Now()},
				Message: c.Message,
			}
			if c.Side == Left {
				ci.Side = "PARENT"
			} else {
				ci.Side = "REVISION"
			}
			input.Comments[c.Path] = append(input.Comments[c.Path], ci)
		}
	}
	_, _, err := g.client.Changes.SetReview(strconv.Itoa(ps.Change), strconv.Itoa(ps.Patchset), input)
	if err != nil {
		return g.maybeWrapError(err)
	}
	return nil
}

// SetReadyForReview marks the change as ready for review.
func (g *Gerrit) SetReadyForReview(changeID, message string) error {
	resp, err := g.client.Changes.SetReadyForReview(changeID, &gerrit.ReadyForReviewInput{
		Message: message,
	})
	if err != nil && resp.StatusCode != 409 { // 409: already ready
		return g.maybeWrapError(err)
	}
	return nil
}

func (g *Gerrit) maybeWrapError(err error) error {
	if err != nil && !g.authenticated {
		return fmt.Errorf(`query failed, possibly because of authentication.
See https://dawn.googlesource.com/new-password for obtaining a username
and password which can be provided with --gerrit-user and --gerrit-pass.
Note: This tool will scan ~/.gitcookies for credentials.
%w`, err)
	}
	return err
}