// 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-stats gathers statistics about changes made to Tint.
package main

import (
	"flag"
	"fmt"
	"net/url"
	"os"
	"os/exec"
	"regexp"
	"time"

	"dawn.googlesource.com/dawn/tools/src/dawn"
	"dawn.googlesource.com/dawn/tools/src/gerrit"
	"dawn.googlesource.com/dawn/tools/src/git"
)

const yyyymmdd = "2006-01-02"

var (
	// See https://dawn-review.googlesource.com/new-password for obtaining
	// username and password for gerrit.
	gerritUser  = flag.String("gerrit-user", "", "gerrit authentication username")
	gerritPass  = flag.String("gerrit-pass", "", "gerrit authentication password")
	repoFlag    = flag.String("repo", "dawn", "the project (tint or dawn)")
	userFlag    = flag.String("user", defaultUser(), "user name / email")
	afterFlag   = flag.String("after", "", "start date")
	beforeFlag  = flag.String("before", "", "end date")
	daysFlag    = flag.Int("days", 182, "interval in days (used if --after is not specified)")
	verboseFlag = flag.Bool("v", false, "verbose mode - lists all the changes")
)

func defaultUser() string {
	if gitExe, err := exec.LookPath("git"); err == nil {
		if g, err := git.New(gitExe); err == nil {
			if cwd, err := os.Getwd(); err == nil {
				if r, err := g.Open(cwd); err == nil {
					if cfg, err := r.Config(nil); err == nil {
						return cfg["user.email"]
					}
				}
			}
		}
	}
	return ""
}

func main() {
	flag.Parse()
	if err := run(); err != nil {
		fmt.Fprintln(os.Stderr, err)
		os.Exit(1)
	}
}

func run() error {
	var after, before time.Time
	var err error
	user := *userFlag
	if user == "" {
		return fmt.Errorf("Missing required 'user' flag")
	}
	if *beforeFlag != "" {
		before, err = time.Parse(yyyymmdd, *beforeFlag)
		if err != nil {
			return fmt.Errorf("Couldn't parse before date: %w", err)
		}
	} else {
		before = time.Now().Add(time.Hour * 24)
	}
	if *afterFlag != "" {
		after, err = time.Parse(yyyymmdd, *afterFlag)
		if err != nil {
			return fmt.Errorf("Couldn't parse after date: %w", err)
		}
	} else {
		after = before.Add(-time.Hour * time.Duration(24**daysFlag))
	}

	g, err := gerrit.New(dawn.GerritURL, gerrit.Credentials{
		Username: *gerritUser, Password: *gerritPass,
	})
	if err != nil {
		return err
	}

	submitted, submittedQuery, err := g.QueryChanges(
		"status:merged",
		"owner:"+user,
		"after:"+date(after),
		"before:"+date(before),
		"repo:"+*repoFlag)
	if err != nil {
		return fmt.Errorf("Query failed: %w", err)
	}

	reviewed, reviewQuery, err := g.QueryChanges(
		"commentby:"+user,
		"-owner:"+user,
		"after:"+date(after),
		"before:"+date(before),
		"repo:"+*repoFlag)
	if err != nil {
		return fmt.Errorf("Query failed: %w", err)
	}

	ignorelist := []*regexp.Regexp{
		regexp.MustCompile("Revert .*"),
	}
	ignore := func(s string) bool {
		for _, re := range ignorelist {
			if re.MatchString(s) {
				return true
			}
		}
		return false
	}

	insertions, deletions := 0, 0
	for _, change := range submitted {
		if ignore(change.Subject) {
			continue
		}
		insertions += change.Insertions
		deletions += change.Deletions
	}

	fmt.Printf("Between %v and %v, %v:\n", date(after), date(before), user)
	fmt.Printf("  Submitted %v changes (LOC: %v+, %v-) \n", len(submitted), insertions, deletions)
	fmt.Printf("  Reviewed %v changes\n", len(reviewed))
	fmt.Printf("\n")

	if *verboseFlag {
		fmt.Printf("Submitted changes:\n")
		for i, change := range submitted {
			fmt.Printf("%3.1v: %6.v %v (LOC: %v+, %v-)\n", i, change.Number, change.Subject, change.Insertions, change.Deletions)
		}
		fmt.Printf("\n")
		fmt.Printf("Reviewed changes:\n")
		for i, change := range reviewed {
			fmt.Printf("%3.1v: %6.v %v (LOC: %v+, %v-)\n", i, change.Number, change.Subject, change.Insertions, change.Deletions)
		}
	}

	fmt.Printf("\n")
	fmt.Printf("Submitted query: %vq/%v\n", dawn.GerritURL, url.QueryEscape(submittedQuery))
	fmt.Printf("Review query: %vq/%v\n", dawn.GerritURL, url.QueryEscape(reviewQuery))

	return nil
}

func today() time.Time {
	return time.Now()
}

func date(t time.Time) string {
	return t.Format(yyyymmdd)
}