package main

import (
	"bytes"
	"context"
	"encoding/json"
	"log"
	"os"
	"regexp"
	"strconv"
	"strings"
	"sync"
	"text/template"
	"time"

	"cloud.google.com/go/pubsub"
	"github.com/ReneKroon/ttlcache/v2"
	"go.skia.org/infra/go/monorail/v1"
	"google.golang.org/api/option"
)

var (
	gcloudProjectId      = "avm99963-bugs"
	pubsubSubscriptionId = "gerrit-events-sub"
	monorailEndpointURL  = "https://bugs.avm99963.com/_ah/api/monorail/v1/"
)

type Bug struct {
	Project   string
	Number    int64
	WillClose bool
}

type Account struct {
	Name     string `json:"name"`
	Email    string `json:"email"`
	Username string `json:"username"`
}

type Message struct {
	Timestamp int64   `json:"timestamp"`
	Reviewer  Account `json:"reviewer"`
	Message   string  `json:"message"`
}

type Approval struct {
	ApprovalType string  `json:"type"`
	Description  string  `json:"description"`
	Value        string  `json:"value"`
	OldValue     string  `json:"oldValue"`
	GrantedOn    int64   `json:"grantedOn"`
	By           Account `json:"by"`
}

type File struct {
	File       string `json:"file"`
	FileOld    string `json:"fileOld"`
	FileType   string `json:"type"`
	Insertions int    `json:"insertions"`
	Deletions  int    `json:"deletions"`
}

type PatchsetComment struct {
	File     string  `json:"file"`
	Line     int     `json:"line"`
	Reviewer Account `json:"reviewer"`
	Message  string  `json:"message"`
}

type PatchSet struct {
	Number         int               `json:"number"`
	Revision       string            `json:"revision"`
	Parents        []string          `json:"parents"`
	Ref            string            `json:"ref"`
	Uploader       Account           `json:"uploader"`
	Author         Account           `json:"author"`
	CreatedOn      int64             `json:"createdOn"`
	Kind           string            `json:"kind"`
	Approvals      []Approval        `json:"approvals"`
	Comments       []PatchsetComment `json:"comments"`
	Files          []File            `json:"files"`
	SizeInsertions int               `json:"sizeInsertions"`
	SizeDeletions  int               `json:"sizeDeletions"`
}

type Dependency struct {
	Id                string `json:"id"`
	Number            int    `json:"number"`
	Revision          string `json:"revision"`
	Ref               string `json:"ref"`
	IsCurrentPatchSet bool   `json:"isCurrentPatchSet"`
}

type Label struct {
	Label  string  `json:"label"`
	Status string  `json:"status"`
	By     Account `json:"by"`
}

type Requirement struct {
	FallbackText    string                 `json:"fallbackText"`
	RequirementType string                 `json:"type"`
	Data            map[string]interface{} `json:"data"`
}

type SubmitRecord struct {
	Status       string        `json:"status"`
	Labels       []Label       `json:"labels"`
	Requirements []Requirement `json:"requirements"`
}

type Change struct {
	Project         string       `json:"project"`
	Branch          string       `json:"branch"`
	Id              string       `json:"id"`
	Number          int          `json:"number"`
	Subject         string       `json:"subject"`
	Owner           Account      `json:"owner"`
	Url             string       `json:"url"`
	CommitMessage   string       `json:"commitMessage"`
	Hashtags        []string     `json:"hashtags"`
	CreatedOn       int64        `json:"createdOn"`
	LastUpdated     int64        `json:"lastUpdated"`
	Open            bool         `json:"open"`
	Status          string       `json:"status"`
	Private         bool         `json:"private"`
	Wip             bool         `json:"wip"`
	Comments        []Message    `json:"comments"`
	TrackingIds     []int        `json:"trackingIds"`
	CurrentPatchSet PatchSet     `json:"currentPatchSet"`
	PatchSets       []PatchSet   `json:"patchSets"`
	DependsOn       []Dependency `json:"dependsOn"`
	NeededBy        []Dependency `json:"neededBy"`
	SubmitRecords   SubmitRecord `json:"submitRecords"`
	AllReviewers    []Account    `json:"allReviewers"`
}

type ChangeMergedEvent struct {
	EventType      string   `json:"type"`
	Change         Change   `json:"change"`
	PatchSet       PatchSet `json:"patchSet"`
	Submitter      Account  `json:"submitter"`
	NewRev         string   `json:"newRev"`
	EventCreatedOn int64    `json:"eventCreatedOn"`
}

var (
	bugsRegex = regexp.MustCompile(`(Bug:|BUG=|Fixed:)((?:\s*(?:[a-z]\w[-\w]*:)?\d+,)*\s*(?:[a-z]\w[-\w]*:)?\d+),?`)
)

func getBugsList(message string) []Bug {
	bugsFooters := bugsRegex.FindAllStringSubmatch(message, -1)
	var allBugs []Bug
	for _, footerMatches := range bugsFooters {
		// This shouldn't happen, but we protect against this case
		// TODO(avm99963): This should be replaced by something like what DCHECK() does in Chromium
		if len(footerMatches) < 3 {
			continue
		}
		willCloseBug := footerMatches[1] == "Fixed:"
		bugs := strings.Split(footerMatches[2], ",")
		for i, _ := range bugs {
			bug := strings.TrimSpace(bugs[i])
			res := strings.Split(bug, ":")
			if len(res) > 2 {
				continue
			}
			if len(res) == 1 {
				number, err := strconv.ParseInt(res[0], 10, 64)
				if err != nil {
					log.Printf("Couldn't parse bug number from %v: %v", bug, err)
				}
				allBugs = append(allBugs, Bug{
					Project:   "misc",
					Number:    number,
					WillClose: willCloseBug,
				})
			} else if len(res) == 2 {
				number, err := strconv.ParseInt(res[1], 10, 64)
				if err != nil {
					log.Printf("Couldn't parse bug number from %v: %v", bug, err)
				}
				allBugs = append(allBugs, Bug{
					Project:   res[0],
					Number:    number,
					WillClose: willCloseBug,
				})
			}
		}
	}
	return allBugs
}

func handlePubSubMessage(ctx context.Context, msg *pubsub.Message, monorailSvc *monorail.Service, template *template.Template, mu sync.Mutex, cache ttlcache.SimpleCache) error {
	mu.Lock()
	defer mu.Unlock()

	var m ChangeMergedEvent
	err := json.Unmarshal(msg.Data, &m)
	if err != nil {
		msg.Ack()
		return err
	}

	// We're only interested in merged changes
	//
	// Even if the struct is meant for change-merged events, unknown fields are
	// ignored.
	if m.EventType != "change-merged" {
		log.Printf("Ignoring message with event '%v'.\n", m.EventType)
		msg.Ack()
		return nil
	}

	if _, err := cache.Get(strconv.Itoa(m.Change.Number)); err != ttlcache.ErrNotFound {
		log.Printf("Not processing CL:%d since it has been processed before", m.Change.Number)
		msg.Ack()
		return nil
	}

	log.Printf("Processing CL:%d\n", m.Change.Number)

	patchSetTime := time.Unix(m.PatchSet.CreatedOn, 0)
	patchSetTimeString := patchSetTime.Format(time.RFC1123Z)

	messageBuf := new(bytes.Buffer)
	template.Execute(messageBuf, struct {
		Event     ChangeMergedEvent
		CommitURL string
		Date      string
	}{
		m,
		"undefined",
		patchSetTimeString,
	})
	if err != nil {
		msg.Ack()
		return err
	}

	message := messageBuf.String()

	ctxRequest, cancel := context.WithDeadline(ctx, time.Now().Add(45*time.Second))
	defer cancel()

	bugs := getBugsList(m.Change.CommitMessage)
	log.Printf("[CL:%d] Bugs: %v\n", m.Change.Number, bugs)

	for _, b := range bugs {
		comment := monorail.ProtoApiPb2V1IssueCommentWrapper{
			Content: message,
			Updates: &monorail.ProtoApiPb2V1Update{},
		}

		if b.WillClose {
			comment.Updates.Status = "Fixed"
		}

		_, err := monorailSvc.Issues.Comments.Insert(b.Project, b.Number, &comment).Context(ctxRequest).Do()
		if err != nil {
			log.Printf("[CL:%d] Couldn't add comment to bug %v: %v\n", m.Change.Number, b, err)
		}

		log.Printf("[CL:%d] Added comment to bug %v\n", m.Change.Number, b)
	}

	cache.Set(strconv.Itoa(m.Change.Number), true)

	msg.Ack()

	return nil
}

func main() {
	log.Println("Starting gitwatcher...")

	ctx := context.Background()

	template, err := template.New("MonorailMessage").Parse(`The following change refers to this bug:
  {{.Event.Change.Url}}

commit {{.Event.NewRev}}
Author: {{.Event.PatchSet.Author.Name}} <{{.Event.PatchSet.Author.Email}}>
Date: {{.Date}}

{{.Event.Change.CommitMessage}}`)
	if err != nil {
		log.Fatal(err)
	}

	cache := ttlcache.NewCache()
	cache.SetTTL(time.Duration(10 * time.Minute))

	pubsubClient, err := pubsub.NewClient(ctx, gcloudProjectId)
	if err != nil {
		log.Fatal(err)
	}
	defer pubsubClient.Close()

	jsonFile, ok := os.LookupEnv("GOOGLE_APPLICATION_CREDENTIALS")
	if !ok {
		log.Println("GOOGLE_APPLICATION_CREDENTIALS environment variable is not set.")
		return
	}

	monorailSvc, err := monorail.NewService(ctx, option.WithEndpoint(monorailEndpointURL), option.WithCredentialsFile(jsonFile))
	if err != nil {
		log.Fatal(err)
	}

	var mu sync.Mutex

	sub := pubsubClient.Subscription(pubsubSubscriptionId)
	err = sub.Receive(ctx, func(ctx context.Context, msg *pubsub.Message) {
		err := handlePubSubMessage(ctx, msg, monorailSvc, template, mu, cache)
		if err != nil {
			log.Printf("Couldn't handle pubsub message: %v\n", err)
		}
	})
}