// 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.

// gerrit provides helpers for obtaining information from Tint's gerrit instance
package gerrit

import (
	"fmt"
	"io/ioutil"
	"os"
	"regexp"
	"strings"

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

const URL = "https://dawn-review.googlesource.com/"

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

type Config struct {
	Username string
	Password string
}

func LoadCredentials() (user, pass string) {
	cookiesFile := os.Getenv("HOME") + "/.gitcookies"
	if cookies, err := ioutil.ReadFile(cookiesFile); err == nil {
		re := regexp.MustCompile(`dawn-review.googlesource.com\s+(?:FALSE|TRUE)[\s/]+(?:FALSE|TRUE)\s+[0-9]+\s+.\s+(.*)=(.*)`)
		match := re.FindStringSubmatch(string(cookies))
		if len(match) == 3 {
			return match[1], match[2]
		}
	}
	return "", ""
}

func New(cfg Config) (*G, error) {
	client, err := gerrit.NewClient(URL, nil)
	if err != nil {
		return nil, fmt.Errorf("couldn't create gerrit client: %w", err)
	}

	user, pass := cfg.Username, cfg.Password
	if user == "" {
		user, pass = LoadCredentials()
	}

	if user != "" {
		client.Authentication.SetBasicAuth(user, pass)
	}

	return &G{client, user != ""}, nil
}

func (g *G) QueryChanges(queryParts ...string) (changes []gerrit.ChangeInfo, query string, err error) {
	changes = []gerrit.ChangeInfo{}
	query = strings.Join(queryParts, "+")
	for {
		batch, _, err := g.client.Changes.QueryChanges(&gerrit.QueryChangeOptions{
			QueryOptions: gerrit.QueryOptions{Query: []string{query}},
			Skip:         len(changes),
		})
		if err != nil {
			if !g.authenticated {
				err = fmt.Errorf(`query failed, possibly because of authentication.
	See https://dawn-review.googlesource.com/new-password for obtaining a username
	and password which can be provided with --gerrit-user and --gerrit-pass.
	%w`, err)
			}
			return nil, "", err
		}

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